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. 2022 Feb 17;13:817468. doi: 10.3389/fimmu.2022.817468

Mucosal Defense Against Giardia at the Intestinal Epithelial Cell Interface

Shahram Solaymani-Mohammadi 1,*
PMCID: PMC8891505  PMID: 35250996

Abstract

Human giardiasis, caused by the protozoan parasite Giardia duodenalis (syn. Giardia lamblia, Giardia intestinalis, Lamblia intestinalis), is one of the most commonly-identified parasitic diseases worldwide. Chronic G. duodenalis infections cause a malabsorption syndrome that may lead to failure to thrive and/or stunted growth, especially in children in developing countries. Understanding the parasite/epithelial cell crosstalk at the mucosal surfaces of the small intestine during human giardiasis may provide novel insights into the mechanisms underlying the parasite-induced immunopathology and epithelial tissue damage, leading to malnutrition. Efforts to identify new targets for intervening in the development of intestinal immunopathology and the progression to malnutrition are critical. Translating these findings into a clinical setting will require analysis of these pathways in cells and tissues from humans and clinical trials could be devised to determine whether interfering with unwanted mucosal immune responses developed during human giardiasis provide better therapeutic benefits and clinical outcomes for G. duodenalis infections in humans.

Keywords: giardiasis, Giardia duodenalis, mucosal immunity, intestinal barrier, epithelium, antimicrobial peptides, disaccharidase deficiency

Introduction

Human giardiasis, caused by the protozoan parasite Giardia duodenalis (syn. Giardia lamblia, Giardia intestinalis, Lamblia intestinalis), is one of the most prevalent enteric parasitic protozoan infections globally, with prevalence rates ranging from 2-5% in the developed world and 20-30% in the developing countries (13). Infections with G. duodenalis account for more than 280 million of new cases of human giardiasis annually worldwide (4, 5). Epidemiological and molecular studies have classified G. duodenalis parasites into eight distinct and genetically-different parasites or “assemblages” (A-H) of which only assemblages A and B are typically identified in both humans and in other mammalian hosts, whereas assemblage E, for example, is predominantly identified in the livestock (6, 7). In recent years, however, assemblage E has also been identified to infect humans in Brazil (8, 9), Egypt (10), Australia (11), Vietnam (12) and New Zealand (13). This further indicates the potential for more widespread anthropozoonotic importance of G. duodenalis parasites and the roles played by numerous mammalian species in the maintenance of the parasite’s life cycle. The parasite’s life cycle follows a direct oral-fecal transmission route, and human infections are initiated by the ingestion of quadrinucleate cysts along with contaminated food or water (1). The ingestion of as few as 10-25 cysts would be enough to successfully colonize the small intestine (14). The vegetative forms of the parasite or trophozoites are binuclear pear-shaped flagellated structures with a bilateral symmetry that colonize the proximal portions of the small intestine, especially the duodenum and less commonly jejunum and the ileum (15).

Most cases of human giardiasis in immunocompetent individuals are self-limiting and and are spontaneously resolved within weeks following exposure (14). Individuals residing in hyperendemic areas for human giardiasis develop partial immunity against subsequent infections as opposed to newly arrived visitors (16, 17). These findings indicate the development of an effective anti-Giardia immunity sufficient for the clearance of G. duodenalis infections in humans. The majority of human giardiasis cases are asymptomatic with no signs of overt clinical profiles (18, 19). Human cases with asymptomatic giardiasis predominantly excrete infective cysts in the feces and play important roles in the maintenance of the parasite’s life cycle (1). Nonetheless, human subjects with symptomatic giardiasis mostly shed trophozoites in feces and are commonly presented with gastrointestinal manifestations that may include abdominal cramps, flatulence, diarrhea, nausea, with a malabsorption syndrome occurring in clinical and subclinical cases and may result in failure to thrive (FTT) and/or stunted growth, especially in children (2023). The malabsorption syndrome observed during chronic human giardiasis is characterized by a steatorrhea type diarrhea with signs of fat- (i.e., vitamins A, K) and water-soluble (i.e., vitamin B12) vitamins deficiency (2429). In persistent cases of giardiasis, especially in children under the age of 5, significant weight loss accompanied by a wasting protein-losing enteropathy are also present (3033).

Giardia Disrupts Tight Junction Proteins and Modulates Intestinal Barrier Integrity

Tight junction (TJ) proteins represent major components of the intercellular adhesion molecules and regulate the permeability of epithelial (i.e., intestine) and endothelial barrier functions [for a review see ref (34)]. These molecules are multi-protein complexes required for defining the structurally- and functionally-distinct basolateral and apical plasma membrane domains and are critical for the maintenance of the cell polarity and paracellular passage (34). The TJ proteins are not entirely impermeable yet the passive trans-epithelial passage of ions and small molecules occurs depending on molecule’s size and polarity (3537). It has been clearly established that TJ proteins play critical and non-redundant roles in multiple organs. The ZO-1 or ZO-2 deficiency was embryonically lethal in mice (38, 39), whereas mice deficient for claudin 1 died shortly after the birth owing to excessive dehydration of the skin (40). While mice deficient for occludin (Ocln-/- ) manifested extensive histological abnormalities as well as chronic inflammatory responses in intestinal and extra-intestinal organs (41), the genetic deletion of ZO-3 in mice did not cause any signs of developmental abnormalities (39, 42).

The integrity of the intestinal TJ proteins is essential for the epithelial impermeability against invading intestinal mucosal pathogens, confining pathogens in the lumen and preventing them to gain access to deeper mucosal layers (43, 44). The impaired TJ protein expression at the mucosal surfaces of the intestine leads to the facilitated entry and spread of enteric pathogens (45). Many enteric microbial pathogens, including enteropathogenic and enterohemorrhagic Escherichia coli (EPEC and EHEC, respectively) as well as Helicobacter pylori, secrete virulence factors that target TJ proteins in order to induce pathogenesis (4345). The Entamoeba histolytica cysteine protease A5 (EhCP-A5) elicited a pro-inflammatory profile, as characterized by increased expression of IFN-γ, TNF-α, and IL-13 that correlated with impaired expression of TJ proteins claudin-2, occludin, and ZO-1 (46). The disrupted or the re-localization of TJ proteins, for example, result in an imbalanced water absorption, an increase in the intra-luminal water content in the intestine and may contribute to the diarrhea observed following the human infections with the attaching and effacing (A/E) EPEC and EHEC (45, 47).

Several lines of evidence have indicated that Giardia infection compromises intestinal epithelial barrier integrity in humans as well as in animal models of human giardiasis (4852). The dysfunctional intestinal epithelial barrier during Giardia infection is characterized by altered expression of TJ proteins (i.e., ZO-1, claudins, occludin), increased intestinal permeability, and reduced transepithelial electrical resistance (TEER) in both murine models of giardiasis as well as in humans (51, 53). The disruption of intestinal epithelial TJ proteins is considered a milestone in the pathological changes associated with Giardia infection in vitro and in vivo (51, 53). The Giardia infection disruption of intestinal epithelial TJ proteins (i.e., ZO-1) was strain-dependent and could be reversed by using caspase-3 inhibitors or the pre-treatment with the epidermal growth factor (EGF) (50). Further clinical investigations indicated that the expression of the TJ protein, claudin 1, decreased by 71% in human subjects with giardiasis as compared with those individuals in the control group (51). It has been postulated that the disruption of the intestinal epithelial TJ proteins during Giardia infection leads to an increased leakage of food antigens through compromised intestinal mucosa into extra-intestinal sites and this may render infected individuals susceptible to allergic reactions commonly observed during human giardiasis (54). Notably, the translocation of commensal bacteria into extra-intestinal sites as a result of Giardia-induced barrier dysfunction correlated with the degradation of TJ proteins occludin and claudin-4 (55). However, it is still unclear how the bacterial translocations into extra-intestinal organs, including mesenteric lymph nodes (MLNs), would contribute to the pathogenesis of human giardiasis. It is yet to be discovered whether different strains of G. duodenalis would cause the differential translocations of bacteria from the intestinal lumen into extra-intestinal organs and whether this potential differential bacterial translocation could account for varied clinical symptoms associated with genetically-diverse G. duodenalis strains.

Several mechanisms have been proposed as to how G. duodenalis infection leads to loss of intestinal epithelial barrier integrity during human giardiasis as well as in murine models of human Giardia infection (50, 52). The attachment of G. duodenalis trophozoites to IECs leads to a contact-dependent alterations in the TJ protein occludin as well as the cellular redistribution of claudin-1 in fully differentiated Caco-2/TC7 cell monolayers (56). It has been suggested that alterations in the TJ proteins in the brush border (BB) occurred in a contact-dependent manner and required the lipid raft membrane of the trophozoite (56). The pre-treatment of the non-transformed human small intestinal epithelial cell line (SCBN) monolayers with EGF (57) or the myosin light chain kinase (MLCK) inhibitor (58), however, significantly prevented the attachment of the live trophozoites to the epithelial monolayers and abolished the parasite-induced disruption of the tight junctional protein ZO-1 (57). The Alerted distribution of TJ proteins, rather than changes in the expression of these proteins, has been proposed as a mechanism underlying the IEC abnormalities observed following Giardia infection (59).

Contact-independent mechanisms also have shown to contribute to the degradation of the TJ proteins and compromised intestinal integrity following Giardia infections; Giardia trophozoites contain a plethora of secreted molecules, including cysteine proteases (CPs), capable of degrading multiple components of the host immune system (6062). The CPs secreted by Giardia trophozoites are considered emerging virulence factors that are able to degrade TJ proteins (i.e., claudin-1 and -4, occludin, E-cadherin) in IECs and are also capable of degrading chemokines expressed by parasitized IECs (63, 64). Recent evidence has suggested that giardipain-1, a cathepsin B-like enzyme, is expressed on the cell surface and flagella of G. duodenalis trophozoites and it can induce apoptosis in IEC-6 epithelial cell monolayers, as evidenced by membrane blebbing and the expression of phosphatidylserine on the surface of parasitized epithelial cell monolayers (52, 60, 62). Giardipain-1 was localized at the epithelial cell-cell junction interface and induced the reorganization and the degradation of occludin and claudin-1 as well as caused decreased TEER in Madin Darby Canine Kidney (MDCK) cell monolayers (52). Consistent with the proteolytic activity of giardipain-1 in degrading the TJ proteins, the pre-treatment with a selective CP inhibitor, E-64, or the siRNA targeting of giardipain-1 gene in G. duodenalis trophozoites led to an attenuated proteolytic activity of giardipain-1, as demonstrated by lessened epithelial insult in IEC-6 monolayers. Three major CPs localized in cytoplasm and the endoplasmic reticulum of G. duodenalis trophozoites were identified in a Giardia/epithelial cell co-culture setting and further evidence demonstrated that these CPs were capable of proteolyzing or reorganizing multiple TJ proteins, including claudins and occludin (64). Notably, G. duodenalis trophozoites expressing a variant surface protein, VSP9B10A, were able to induce the loss of cell-cell contact and cell detachment at the sites of the trophozoites attachment (65). The incubation of IEC-6 cell monolayers with conditioned medium obtained from G. duodenalis trophozoites expressing VSP9B10A/IEC-6 cell monolayers co-culture also induced cytotoxicity, whereas the monoclonal antibody blockade targeting the VSP9B10A protein expressed by trophozoites reversed those cytotoxic effects at the trophozoite/epithelial cell interface (62, 65).

Altogether, these findings demonstrate that secreted soluble proteins, including proteases, can immensely contribute to the pathogenesis of G. duodenalis infection in vivo. However, it still remains unclear how these parasite-derived CPs contribute to the immunopathology observed during giardiasis and whether vaccine candidates targeting these proteins could protect from parasite-induced immunotherapy. To further understand how TJ protein abnormalities could lead to a malabsorption syndrome (i.e., impaired absorption of electrolytes, water and disaccharidase deficiency) as well as increased intestinal permeability observed during human giardiasis, especially in younger children, further investigations are warranted (66, 67).

Giardia Induces Apoptosis in Parasitized IECs

Apoptotic IECs comprised up to 1.5% of the total IECs in parasitized human duodenal biopsies following G. duodenalis infections, whereas 1% of the total IECs from duodenal biopsies from healthy controls were apoptotic as determined by a positive terminal transferase uridyl nick end labeling (TUNEL) staining assay (51). Apoptotic IECs, following human G. duodenalis infections, were characterized by chromatin condensation clustering around the nuclear periphery as well as segmentation of the nucleus (51). The Giardia-induced apoptosis in IECs was more evident after infection with non-host specific strains as well as following mixed infections with distinct G. duodenalis assemblages (68).

A wide array of mechanisms have been proposed to contribute to apoptosis induced by different genotypes of Giardia parasites in IECs (69). Earlier studies reported a strain-dependent induction of apoptosis in IECs following infection with a single Giardia assemblage or after mixed Giardia infections (50, 68). It was shown that the NF and S2 strains of G. duodenalis, but not WB or PB, were able to induce apoptosis in IECs, and these effects were abolished by pre-treating human duodenal epithelial monolayers with a caspase-3 inhibitor, Z-DEVD-FMK (50). Further studies have indicated the importance of caspases, including caspase 3 (50, 52, 70, 71) and caspase 9 (72) in mediating Giardia-induced apoptosis in IECs. Giardia infections facilitate apoptosis in IECs by the downregulation of anti-apoptotic proteins, including Bcl-2, and the up-regulation of the pro-apoptotic proteins, including Bax, suggesting a potential contribution of caspase-dependent apoptosis signaling pathways in the induction of pathogenesis during giardiasis (51, 70, 73).

The production of nitric oxide (NO), and its two major ultimate metabolites (i.e., nitrite and nitrate) by IECs represents another defensive mechanism employed against a wide range of lumen-dwelling enteric pathogens at the intestinal epithelium surface (74, 75). Giardia parasites interfere with the NO production by IECs through competing over local arginine availability and depriving IECs of arginine is considered a mechanism employed by G. duodenalis to evade NO-mediated killing of the parasite (74). Additionally, this has been suggested as a mechanism by which G. duodenalis induces apoptosis in parasitized IECs, since arginine deprivation is known to lead to apoptosis (74, 75).

Consistent with the observations that G. duodenalis strains differ in their ability to induce pathological changes at the upper intestinal epithelial surface (50, 66, 68, 76), calves infected with assemblage E neither showed increased rates of apoptotic cells nor did they exhibit any signs of villus shortening as compared with uninfected controls (77). Although the exact mechanisms underlying this discrepancy is still unclear, it is likely that the genetic loci, including triosephosphate isomerase (tpi), glutamate dehydrogenase (gdh) and β-giardin (bg), commonly used to assign Giardia parasites to specific genotypes/assemblages are not associated with virulence (2).

Giardia Infection Induces Cytoskeletal Remodeling in IECs

It has been shown that parasitized IECs undergo drastic cytoskeletal remodeling following Giardia infection in vitro and in vivo (76). The expression and the cellular distribution of actin filaments (i.e., F-actin and alpha-actinin) as well as actin-binding proteins (i.e., villin and ezrin) are altered following Giardia infection, leading to compromised intestinal epithelial integrity (49, 76, 78). The co-incubation of human intestinal epithelial monolayers (i.e., SCBN and Caco2 cell lines) with live Giardia parasites led to local condensation of F-actin and loss of alpha-actinin in IECs as did the co-culture of monolayers with Giardia lysates or Giardia conditioned medium (49). However, Verapamil, a phenylalkylamine calcium channel blocker, did not alter F-actin reorganization suggesting an extracellular calcium independent-mechanism in the induction of cytoskeletal abnormalities following Giardia infection (49). Further studies demonstrated the significant contribution of host immune responses in the induction of cytoskeletal alterations following Giardia infection in vivo (76). The expression and the cellular distribution of villin and ezrin, the two crucial elements of the actin cytoskeleton of the BB of IECs, underwent major post-transcriptional changes during the clearance phase of G. duodenalis infection in vivo (76). Notably, ezrin and villin were found to be differentially regulated by immune-mediated mechanisms following Giardia infection; while ezrin proteolysis required CD4+ T cells alone, the cleavage of villin required both CD4+ and CD8+ T cell responses (76). The decreased levels of ezrin phosphorylation as well as increased levels of phosphorylated villin correlated with reduced BB disaccharidase enzymes (i.e., sucrase, maltase) activity observed during Giardia infection (66, 76). Altogether these observations demonstrated that both host and pathogen factors contributed to the cytoskeletal remodeling observed during giardiasis.

Giardia Infection Promotes the Expression of Antimicrobial Peptides by Parasitized IECs

As the first line of defense against mucosal pathogens, IECs are equipped with a plethora of defensive mechanisms, including the ability to secret a wide array of antimicrobial peptides (AMPs) (i.e., defensins, trefoil factors) [for a review see ref (79)]. The AMPs are a diverse group of naturally occurring positively charged small molecules and are considered integral components of the innate immune system in a wide range of animals and plants (80). These proteins are crucial against invading mucosa-dwelling microbes, including bacterial, parasitic, and fungal pathogens (81, 82). Multiple AMPs, including indolicidin, a 13-residue peptide originally isolated from bovine neutrophils, as well as human defensins possessed antigiardial activity against G. duodenalis trophozoites in vitro (83).

The cytokine IL-22 is shown to promote antimicrobial responses at the mucosal surfaces of the intestine via the regulation of these peptide secretions through interaction with its receptor, IL-22R, which is solely expressed on non-hematopoietic cells, including epithelial cells in the intestine [for a review see ref (84)]. As depicted in Figure 1 , we showed that G. duodenalis infection induces IL-22 secretion in a CD4+ T cell-dependent manner in a mouse model of the human Giardia infection (66). Giardia infection upregulates the expression of multiple AMPs both in vitro and in vivo (8587). Caco-2 monolayers incubated with G. duodenalis trophozoites promoted the expression of human β-defensin 2 (HBD-2) and trefoil factor 3 (TFF3) (87). The upregulation of HBD-2 and TFF3 by Caco-2 monolayers was abolished by pretreatment of G. duodenalis with a global CP inhibitor, E-64d, or a cathepsin B CP inhibitor, Ca-074Me (87). Furthermore, Giardia parasite-derived proteases can cleave human defensins (i.e., α-HD6 and β-HD1) in vitro (64), indicating that Giardia parasites likely employ this strategy to evade immune-mediated killing by AMPs in vivo. These observations demonstrate the pivotal roles played by Giardia-derived proteases as contributing factors in the pathogenesis of human giardiasis and exemplify a potential strategy employed by the parasite to survive in vivo and suggests that these AMPs could be devised to boost host’s non-immune defense mechanisms against this pathogen.

Figure 1.

Figure 1

Giardia infection induces the secretion of AMPs (e.g., defensins, trefoil factors) in parasitized IECs likely via an IL-22/IL-22R-mediated mechanism.

Giardia Parasites Are Closely Associated With the Intestinal Epithelium

Early studies have shown that G. duodenalis differentially binds to the apical surface and the basolateral membrane of murine cell lines in vitro (88) and trophozoite optimal growth and survival require intimate interaction with mammalian cells (89). Giardia trophozoites bind to small intestinal IECs with a higher affinity as compared with colonic enterocytes, consistent with the anatomical adaptation/niche in the upper portions of the small intestine (88). Giardia trophozoites adhere to microvilli close to the bases of the villi in the upper portions of the mouse small intestinal epithelium in vivo (15, 90). They also have the ability to colonize Peyer’s patches throughout the upper portions of the small intestine, but they are not found attaching to microfold cells (also known as M cells) (90). Upon infection, Giardia trophozoites are contained in the lumen and do not invade deeper layers of the intestine. Under certain circumstances (i.e., in immunocompromised individuals), however, Giardia trophozoites become invasive and are spread into intestinal mucosa extending into submucosa layer as well as extra-intestinal sites (9193). These findings indicate the requirement of an intact immune response in order to contain the parasite within the intestinal lumen.

Intestinal Epithelium as First Defense Layer Against Giardia: Role of Intestinal Mucus Layer

The mucosal surface of the intestinal tract represents a main entry point for various microbial pathogens. These microbial pathogens encounter natural innate barriers in the gut, including the mucus layer, in order to prevent potential pathogens or their immunomodulatory components/antigens to reach the underlying epithelium, a process known as non-immune exclusion (94, 95). Mucins of the human gastrointestinal tract are highly glycosylated proteins and consist of an apomucin protein backbone (100-500 kDa) joined to oligosaccharides (96). These glycoproteins are secreted by specialized epithelial cell types (i.e., goblet cells) and line the luminal surfaces of the gastrointestinal tract from the oral cavity/oropharynx to rectum (97), and act as the first line of host defense against multiple enteric microbial pathogens, including G. duodenalis (61). The mucin binding sites compete with those of underlying intestinal epithelium and limit attachment and the subsequent colonization of the intestinal wall by microbial pathogens (98, 99). Furthermore, the mucus layer of the intestinal tract provides a slimy and viscous physical barrier against ingested pathogens and can substantially limit their access to the underlying intestinal epithelium (100). The gut-dwelling protozoan parasites, including G. duodenalis, encounter natural barriers during intestinal colonization and have developed strategies to streamline this process through evading the recognition by host’s non-immune and immune mechanisms (2). The expression of mucins is upregulated following Giardia infection in vitro and in vivo (101106) and can inhibit the attachment of G. duodenalis trophozoites in vitro most likely through electrostatic repulsion between the trophozoites and the underlying substratum (107). However, not all the components of the mucus possess inhibitory effects on the parasite attachment, since a non-mucin low density, protein-rich fraction of the mucus from the duodenum and ileum of humans or rabbits promoted the attachment and the survival of G. duodenalis trophozoites in a dose-dependent manner in vitro as well as protected trophozoites from being destroyed by the human milk (108110). While lumen-dwelling protozoan parasites were drastically different in their ability to break down mucins, G. duodenalis produced beta-N-acetylglucosaminidase as well as detectable levels of beta-N-acetylgalactosaminidase activity, suggesting the ability of G. duodenalis trophozoites to efficiently break down mucins (111). These findings were further confirmed by the observations that animals infected with G. duodenalis exhibited a thinner mucus layer and had larger goblet cells (GCs) in greater numbers, accompanied by depleted GCs mucin stores as compared with their uninfected controls (104, 112). Consistent with the protective roles played by mucins during giardiasis, mice deficient for mucin 2 gene (Muc2 -/-) showed significantly higher trophozoite burdens in the small intestine and had impaired weight gain as compared with control animals (104). The mucus secretion is regulated by a wide range of immune (i.e., pro-inflammatory cytokines) and non-immune (i.e., diet) factors (113, 114). Diets low in fiber facilitate the overgrowth of those bacteria capable of degrading the mucus layer and promotes the subsequent Citrobacter rodentium-induced colitis (115). Consistently, Mongolian gerbils (Meriones unguiculatus) receiving a high-fiber (20%) diet were more resistant to infection with G. duodenalis as compared with those gerbils maintained on a diet with low fiber (5%) contents (101). The higher mucus secretion in those animals maintained on a high-fiber diet was suggested as a factor contributing to the resistance of these animals to G. duodenalis infection (101). These findings reveal an intricate crosstalk between G. duodenalis and the intestinal mucus layer at the mucosal surfaces of the small intestine. Strategies should be employed to boost non-immune innate mechanisms against intestinal microbial pathogens via restoring eroded mucus layer by promoting the secretion of mucus using fiber-rich diets.

Immune Activation by Giardia Parasites at the Intestinal Epithelium

Giardia parasites are considered non-invasive to minimally invasive gut pathogens that typically reside on the epithelial surfaces of the upper portions of the small intestine (90). Yet, the adhesion of Giardia parasites to the intestinal epithelium triggers a strong immune response activation, as characterized by an increased influx of immune cell subtypes in the intraepithelial lymphocytes (IELs) as well as in the lamina propria lymphocytes (LPLs) of the small intestine during an early phase of the parasite’s colonization (66, 116121). Furthermore, several lines of research have indicated that parasitized IECs secrete a wide array of chemokines and anti-giardial factors upon coming into contact with Giardia parasites in vitro and in vivo (19, 74, 75, 106, 122125). The treatment of human colonic cell lines (i.e., Caco-2, HT-29) with the excretory-secretory products of Giardia or whole trophozoites induced the production of pro-inflammatory cytokines TNF-α, IL-1β, and IL-8 (also known as CXCL8) by these cells in vitro (63, 125). The degradation of CXCL8 via G. duodenalis cathepsin B cysteine proteases attenuates CXCL8-induced chemotaxis of human neutrophils (63, 126), indicating a potential immune evasion mechanism employed by the parasite to prevent the recruitment of neutrophils via a CXCL8/CXCR1/CXCR2 circuit.

Giardia Infection Predisposes Infected Individuals to Disaccharidase Deficiency

Disaccharidase enzymes, including sucrase and lactase, are expressed by BB membrane and IECs in the small intestine. A decrease in the surface area of the small intestine is associated with diminished levels of disaccharidases required for the breakdown of disaccharides into absorbable monosaccharides (127). Sucrase, for example, breaks down sucrose into glucose- fructose, whereas lactase and maltase convert lactose and maltose into galactose-glucose and two glucose monomers, respectively. Undigested intact disaccharides can increase the small intestine’s osmotic pressure gradients, facilitating the secretion of large quantities of water into the intestinal lumen and leads to intestinal swelling and rapid gastrointestinal transit into the colon (128). Disaccharidase deficiency is observed following various infectious and non-infectious conditions (66, 129, 130).

As shown in Figure 2 , numerous studies have linked disaccharidases deficiency with Giardia infections in both humans and in mouse models of the human disease (57, 117, 131). Early studies demonstrated that the eradication of the parasite in human subjects infected with G. duodenalis led to the disappearance of clinical symptoms and the malabsorption syndrome as well as restored the villi microstructures (132). Among disaccharidases, the lactase deficiency is a common finding in Giardia-infected individuals (133135), and its deficiency strongly correlates with the severity of mucosal damage in the jejunum and may persist as the lactose intolerance even after the successful chemotherapy (136).

Figure 2.

Figure 2

Schematic model of disaccharidase deficiency following infection with Giardia infection in vivo.

Several mechanisms have been proposed as to how Giardia infection causes disaccharidase deficiency in the small intestine. Gillon et al. found a direct correlation between the impaired expression of disaccharidases and the maximal trophozoite numbers in the jejunum 2 weeks post-infection and thus proposed that the parasite’s direct effects on the jejunal BB rather than IECs immaturity, accounted for impaired levels of disaccharidase activities in a model of primary G. muris infection (117). In consistent with these observations, it was also proposed that the G. duodenalis induction of disaccharidase deficiency was a direct result of the damage to the small intestine epithelial surface rather than bacterial overgrowth, bile aids deconjugation, or immune-mediated host responses (137, 138). However, the IECs immaturity and an increase in the immature/mature IECs ratio have been proposed as a mechanism underlying disaccharidase deficiency, since immature IECs express substantially lower levels of disaccharidases as compared with mature fully-transformed IECs (76). We have demonstrated that G. duodenalis infection leads to a facilitated proliferation of IECs, a shift in the immature/mature IECs ratio, and an altered positional distribution/migration of IECs along the crypt-villus axis (CVA) in a primary mouse model of human infection (76). Reduced levels of ezrin phosphorylation as well as enhanced phosphorylation levels of villin correlated with diminished BB enzyme activity at the peak of G. duodenalis infection (76).

The primary G. duodenalis infection in gerbils was associated with ephemeral impairments in disaccharidase activity in the small intestine, whereas the secondary infections in these animals caused even more severe reductions in the disaccharidase levels following infection (139). Notably, the inoculum dose on the re-challenge did not correlate with reduced levels of disaccharidases activity and the presence of viable trophozoites was not required for the induction of severe enzyme deficiency during a secondary G. duodenalis infection (139, 140). The disaccharidase deficiency was dependent on the mouse strain and was more evident in those mice susceptible (i.e., C3H/HeN) to G. muris infections as compared with the resistant C57BL/6 strain (141). In an attempt to reveal the contribution of host and parasite factors, including host gender, in the induction of enzyme deficiency during G. muris infection, it was observed that male and female mice both had decreased enzyme activities following infection, with males exhibiting persistent reductions in enzyme activity as compared with females and a given strain of Giardia was associated with impaired enzyme activity, whereas as other strains were not (67, 142, 143). The significantly higher trophozoite numbers in males during a primary infection setting accounted for the gender-based differences in enzyme activity in these animals (142). The gender-biased differences in the microbiome compositions between males and females could potentially explain discrepancies observed in the levels of enzyme activity following Giardia infection, as the microbiome is shown to regulate disaccharidase levels through the activation of T cell subsets (121). Altogether, these findings highlighted the contribution of host factors, including host’s genetic background and gender, in the reduction of BB enzymes during giardiasis. These observations also emphasized the potential roles played by immune system during giardiasis, especially during secondary infections.

Further investigations have clearly found a more direct link between host’s immune status and disaccharidase deficiency in the small intestine following Giardia infection (66, 144, 145). The BB damage and the subsequent disaccharidase deficiency did not develop in the absence of T cells in nude mice following G. muris infection or in those mice with severe combined immunodeficiency (SCID), lacking both arms of the adaptive immunity (66, 145). The adoptive transfer of CD8+ T cells, but not CD4+ T cells, from infected mice into naïve mice led to reduced disaccharidase enzymatic activity in recipients, suggesting that CD8+ T cells are crucial for the induction of BB abnormalities typically observed during Giardia infection. As such, those mice deficient in CD8+ T cells (β2M -/-) cleared G. duodenalis infection similar to their wild-type controls, whereas they did not exhibit defects in disaccharidase activity (66). Based on these findings, it is hypothetically feasible to generate protective immunity against Giardia infections without inducing the BB damage, including disaccharidase deficiency.

Conclusion

The mucosal surface of the intestinal tract represents a major interface for host-microbe interaction and the main entry route for many microbial pathogens, including Giardia parasites. Intestinal epithelial cells are integral components of an intricate network of immune and non-immune players responsible for the maintenance of the intestinal homeostasis. As a major mucosal surface interfacing between the “self” and the “non-self”, the intestinal epithelium participates in host defense against a wide range of lumen-dwelling intestinal pathogens by secreting multiple immune mediators with direct anti-microbial properties. The Giardia attachment to the intestinal epithelium is considered an essential step towards the parasite colonization and the subsequent induction of pathological changes observed during human giardiasis. However, the mechanisms by which Giardia parasites intimately associate with the intestinal epithelium are not fully understood. To this end, a comprehensive understanding of the crosstalk between the intestinal epithelial layer and Giardia parasites will provide insights into the roles contributed by host and parasite factors in the development of immunopathology during human infections and will further provide mechanisms to harness dysregulated immune responses in patients with giardiasis and may offer novel therapeutic targets for the treatment of these patients.

Author Contributions

Conceptualization, writing—original draft, reviewing, and editing: SS-M.

Funding

Research in the Laboratory of Mucosal Immunology is supported by a startup fund (20344-8015) from the Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota (to SS-M), a Dean’s Meritorious Pilot Grant, School of Medicine and Health Sciences, University of North Dakota (to SS-M), and by NIH/NIGMSP20GM113123 (to SS-M).

Conflict of Interest

The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s Note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Acknowledgments

I thank Dr. Emilie Dekrey at the University of North Dakota for comments and useful discussion. Figures 1 and 2 were generated using Biorender.com.

Abbreviations

AMPs, antimicrobial peptides; A/E, attaching and effacing; BB, brush border; CPs, cysteine proteases; CVA, crypt-villus axis; EGF, epidermal growth factor; EHEC, enterohemorrhagic Escherichia coli; EPEC, enteropathogenic Escherichia coli; FTT, failure to thrive; GC, goblet cell; HBD-2, human β-defensin 2; IEC, intestinal epithelial cell; IELs, intraepithelial lymphocytes; LPLs, lamina propria lymphocytes; MDCK, Madin Darby canine kidney; MLCK, myosin light chain kinase; MLNs, mesenteric lymph nodes; NO, nitric oxide; SCID, severe combined immunodeficiency; TEER, transepithelial electrical resistance; TFF3, trefoil factors 3; TJ, tight junction; TUNEL, terminal transferase uridyl nick end labeling; ZO-1, zonula occludens-1

References

  • 1. Adam RD. Biology of Giardia Lamblia. Clin Microbiol Rev (2001) 14:447–75. doi: 10.1128/CMR.14.3.447-475.2001 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 2. Solaymani-Mohammadi S, Singer SM. Giardia Duodenalis: The Double-Edged Sword of Immune Responses in Giardiasis. Exp Parasitol (2010) 126:292–7. doi: 10.1016/j.exppara.2010.06.014 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 3. Yoder JS, Gargano JW, Wallace RM, Beach MJ. Giardiasis Surveillance-United States, 2009-2010. MMWR (2012) 2012:61:13–23. [PubMed] [Google Scholar]
  • 4. Savioli L, Smith H, Thompson A. Giardia and Cryptosporidium Join the 'Neglected Diseases Initiative'. Trends Parasitol (2006) 22:203–8. doi: 10.1016/j.pt.2006.02.015 [DOI] [PubMed] [Google Scholar]
  • 5. Einarsson E, Ma'ayeh S, Svärd SG. An Up-Date on Giardia and Giardiasis. Curr Opin Microbiol (2016) 34:47–52. doi: 10.1016/j.mib.2016.07.019 [DOI] [PubMed] [Google Scholar]
  • 6. Thompson RC. Echinococcus, Giardia and Cryptosporidium: Observational Studies Challenging Accepted Dogma. Parasitology (2009) 136:1529–35. doi: 10.1017/S0031182009005897 [DOI] [PubMed] [Google Scholar]
  • 7. Heyworth MF. Giardia Duodenalis Genetic Assemblages and Hosts. Parasite (2016) 23:13. doi: 10.1051/parasite/2016013 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 8. Fantinatti M, Bello AR, Fernandes O, Da-Cruz AM. Identification of Giardia Lamblia Assemblage E in Humans Points to a New Anthropozoonotic Cycle. J Infect Dis (2016) 214:1256–9. doi: 10.1093/infdis/jiw361 [DOI] [PubMed] [Google Scholar]
  • 9. Scalia LA, Fava NM, Soares RM, Limongi JE, da Cunha MJ, Pena IF, et al. Multilocus Genotyping of Giardia Duodenalis in Brazilian Children. Trans R Soc Trop Med Hyg (2016) 110:343–9. doi: 10.1093/trstmh/trw036 [DOI] [PubMed] [Google Scholar]
  • 10. Abdel-Moein KA, Saeed H. The Zoonotic Potential of Giardia Intestinalis Assemblage E in Rural Settings. Parasitol Res (2016) 115:3197–202. doi: 10.1007/s00436-016-5081-7 [DOI] [PubMed] [Google Scholar]
  • 11. Zahedi A, Field D, Ryan U. Molecular Typing of Giardia Duodenalis in Humans in Queensland - First Report of Assemblage E. Parasitology (2017) 144:1154–61. doi: 10.1017/S0031182017000439 [DOI] [PubMed] [Google Scholar]
  • 12. Iwashita H, Sugamoto T, Takemura T, Tokizawa A, Vu TD, Nguyen TH, et al. Molecular Epidemiology of Giardia Spp. In Northern Vietnam: Potential Transmission Between Animals and Humans. Parasite Epidemiol Control (2020) 12:e00193. doi: 10.1016/j.parepi.2020.e00193 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 13. Garcia-R JC, Ogbuigwe P, Pita AB, Velathanthiri N, Knox MA, Biggs PJ, et al. First Report of Novel Assemblages and Mixed Infections of Giardia Duodenalis in Human Isolates From New Zealand. Acta Trop (2021) 220:105969. doi: 10.1016/j.actatropica.2021.105969 [DOI] [PubMed] [Google Scholar]
  • 14. Rendtorff RC. The Experimental Transmission of Human Intestinal Protozoan Parasites. II. Giardia Lamblia Cysts Given in Capsules. Am J Hyg (1954) 59:209–20. doi: 10.1093/oxfordjournals.aje.a119634 [DOI] [PubMed] [Google Scholar]
  • 15. Homan WL, Mank TG. Human Giardiasis: Genotype Linked Differences in Clinical Symptomatology. Int J Parasitol (2001) 31:822–6. doi: 10.1016/S0020-7519(01)00183-7 [DOI] [PubMed] [Google Scholar]
  • 16. Istre GR, Dunlop TS, Gaspard GB, Hopkins RS. Waterborne Giardiasis at a Mountain Resort: Evidence for Acquired Immunity. Am J Public Health (1984) 74:602–4. doi: 10.2105/AJPH.74.6.602 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 17. Isaac-Renton JL, Lewis LF, Ong CS, Nulsen MF. A Second Community Outbreak of Waterborne Giardiasis in Canada and Serological Investigation of Patients. Trans R Soc Trop Med Hyg (1994) 88:395–9. doi: 10.1016/0035-9203(94)90397-2 [DOI] [PubMed] [Google Scholar]
  • 18. Garzón M, Pereira-da-Silva L, Seixas J, Papoila AL, Alves M, Ferreira F, et al. Association of Enteric Parasitic Infections With Intestinal Inflammation and Permeability in Asymptomatic Infants of São Tomé Island. Pathog Glob Health (2017) 111:116–27. doi: 10.1080/20477724.2017.1299831 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 19. Kraft MR, Klotz C, Bücker R, Schulzke JD, Aebischer T. Giardia's Epithelial Cell Interaction In Vitro: Mimicking Asymptomatic Infection? Front Cell Infect Microbiol (2017) 7:421. doi: 10.3389/fcimb.2017.00421 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 20. Gilman RH, Brown KH, Visvesvara GS, Mondal G, Greenberg B, Sack RB, et al. Epidemiology and Serology of Giardia Lamblia in a Developing Country: Bangladesh. Trans R Soc Trop Med Hyg (1985) 79:469–73. doi: 10.1016/0035-9203(85)90068-9 [DOI] [PubMed] [Google Scholar]
  • 21. Mahmud MA, Chappell C, Hossain MM, Habib M, Dupont HL. Risk Factors for Development of First Symptomatic Giardia Infection Among Infants of a Birth Cohort in Rural Egypt. Am J Trop Med Hyg (1995) 53:84–8. doi: 10.4269/ajtmh.1995.53.84 [DOI] [PubMed] [Google Scholar]
  • 22. Al-Mekhlafi HM, Al-Maktari MT, Jani R, Ahmed A, Anuar TS, Moktar N, et al. Burden of Giardia Duodenalis Infection and Its Adverse Effects on Growth of Schoolchildren in Rural Malaysia. PloS Negl Trop Dis (2013) 7:e2516. doi: 10.1371/journal.pntd.0002516 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 23. Rogawski ET, Bartelt LA, Platts-Mills JA, Seidman JC, Samie A, Havt A, et al. MAL-ED Network Investigators. Determinants and Impact of Giardia Infection in the First 2 Years of Life in the MAL-ED Birth Cohort. J Pediatr Infect Dis Soc (2017) 6:153–60. doi: 10.1093/jpids/piw082 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 24. Cowen AE, Campbell CB. Giardiasis–a Cause of Vitamin B12 Malabsorption. Am J Dig Dis (1973) 18:384–90. doi: 10.1007/BF01071987 [DOI] [PubMed] [Google Scholar]
  • 25. Mahalanabis D, Simpson TW, Chakraborty ML, Ganguli C, Bhattacharjee AK, Mukherjee KL. Malabsorption of Water Miscible Vitamin A in Children With Giardiasis and Ascariasis. Am J Clin Nutr (1979) 32:313–8. doi: 10.1093/ajcn/32.2.313 [DOI] [PubMed] [Google Scholar]
  • 26. Takahashi M, Katayama Y, Takada H, Hirakawa J, Kuwayama H, Yamaji H, et al. Silent Infection of Giardia Lamblia Causing Bleeding Through Vitamin K Malabsorption. J Gastroenterol Hepatol (2001) 16:1171–2. doi: 10.1046/j.1440-1746.2001.02414.x [DOI] [PubMed] [Google Scholar]
  • 27. Girard C, Dereure O, Blatière V, Guillot B, Bessis D. Vitamin a Deficiency Phrynoderma Associated With Chronic Giardiasis. Pediatr Dermatol (2006) 23:346–9. doi: 10.1111/j.1525-1470.2006.00261.x [DOI] [PubMed] [Google Scholar]
  • 28. Quihui-Cota L, Astiazarán-García H, Valencia ME, Morales-Figueroa GG, Lopez-Mata MA, Vazquez Ortiz F. Impact of Giardia Intestinalis on Vitamin A Status in Schoolchildren From Northwest Mexico. Int J Vitam Nutr Res (2008) 78:51–6. doi: 10.1024/0300-9831.78.2.51 [DOI] [PubMed] [Google Scholar]
  • 29. Astiazaran-Garcia H, Lopez-Teros V, Valencia ME, Vazquez-Ortiz F, Sotelo-Cruz N, Quihui-Cota L. Giardia Lamblia Infection and Its Implications for Vitamin A Liver Stores in School Children. Ann Nutr Metab (2010) 57:228–33. doi: 10.1159/000321682 [DOI] [PubMed] [Google Scholar]
  • 30. Sutton DL, Kamath KR. Giardiasis With Protein-Losing Enteropathy. J Pediatr Gastroenterol Nutr (1985) 4:56–9. doi: 10.1097/00005176-198502000-00011 [DOI] [PubMed] [Google Scholar]
  • 31. Korman SH, Bar-Oz B, Mandelberg A, Matoth I. Giardiasis With Protein-Losing Enteropathy: Diagnosis by Fecal Alpha 1-Antitrypsin Determination. J Pediatr Gastroenterol Nutr (1990) 10:249–52. doi: 10.1097/00005176-199002000-00019 [DOI] [PubMed] [Google Scholar]
  • 32. Al-Mekhlafi MS, Azlin M, Nor Aini U, Shaik A, Sa'iah A, Fatmah MS, et al. Giardiasis as a Predictor of Childhood Malnutrition in Orang Asli Children in Malaysia. Trans R Soc Trop Med Hyg (2005) 99:686–891. doi: 10.1016/j.trstmh.2005.02.006 [DOI] [PubMed] [Google Scholar]
  • 33. Akkelle BS, Tutar E, Sengul OK, Celikel CA, Ertem D. A Rare Complication of Giardiasis in Children: Protein-Losing Enteropathy. Pediatr Infect Dis J (2018) 37:e345–7. doi: 10.1097/INF.0000000000002025 [DOI] [PubMed] [Google Scholar]
  • 34. Otani T, Furuse M. Tight Junction Structure and Function Revisited. Trends Cell Biol (2020) 30:805–17. doi: 10.1016/j.tcb.2020.08.004 [DOI] [PubMed] [Google Scholar]
  • 35. Van Itallie CM, Anderson JM. The Molecular Physiology of Tight Junction Pores. Physiol (Bethesda) (2004) 19:331–8. doi: 10.1152/physiol.00027.2004 [DOI] [PubMed] [Google Scholar]
  • 36. Van Itallie CM, Anderson JM. Claudins and Epithelial Paracellular Transport. Annu Rev Physiol (2006) 68:403–29. doi: 10.1146/annurev.physiol.68.040104.131404 [DOI] [PubMed] [Google Scholar]
  • 37. Angelow S, Yu AS. Claudins and Paracellular Transport: An Update. Curr Opin Nephrol Hypertens (2007) 16:459–64. doi: 10.1097/MNH.0b013e32820ac97d [DOI] [PubMed] [Google Scholar]
  • 38. Katsuno T, Umeda K, Matsui T, Hata M, Tamura A, Itoh M, et al. Deficiency of Zonula Occludens-1 Causes Embryonic Lethal Phenotype Associated With Defected Yolk Sac Angiogenesis and Apoptosis of Embryonic Cells. Mol Biol Cell (2008) 19:2465–75. doi: 10.1091/mbc.e07-12-1215 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 39. Xu J, Kausalya PJ, Phua DC, Ali SM, Hossain Z, Hunziker W. Early Embryonic Lethality of Mice Lacking ZO-2, But Not ZO-3, Reveals Critical and Nonredundant Roles for Individual Zonula Occludens Proteins in Mammalian Development. Mol Cell Biol (2008) 28:1669–78. doi: 10.1128/MCB.00891-07 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 40. Furuse M, Hata M, Furuse K, Yoshida Y, Haratake A, Sugitani Y, et al. Claudin-Based Tight Junctions Are Crucial for the Mammalian Epidermal Barrier: A Lesson From Claudin-1-Deficient Mice. J Cell Biol (2002) 156:1099–111. doi: 10.1083/jcb.200110122 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 41. Saitou M, Furuse M, Sasaki H, Schulzke JD, Fromm M, Takano H, et al. Complex Phenotype of Mice Lacking Occludin, a Component of Tight Junction Strands. Mol Biol Cell (2000) 11:4131–42. doi: 10.1091/mbc.11.12.4131 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 42. Adachi M, Inoko A, Hata M, Furuse K, Umeda K, Itoh M, et al. Normal Establishment of Epithelial Tight Junctions in Mice and Cultured Cells Lacking Expression of ZO-3, a Tight-Junction MAGUK Protein. Mol Cell Biol (2006) 26:9003–15. doi: 10.1128/MCB.01811-05 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 43. Uotani T, Murakami K, Uchida T, Tanaka S, Nagashima H, Zeng XL, et al. Changes of Tight Junction and Interleukin-8 Expression Using a Human Gastroid Monolayer Model of Helicobacter Pylori Infection. Helicobacter (2019) 24:e12583. doi: 10.1111/hel.12583 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 44. Lu RY, Yang WX, Hu YJ. The Role of Epithelial Tight Junctions Involved in Pathogen Infections. Mol Biol Rep (2014) 41:6591–610. doi: 10.1007/s11033-014-3543-5 [DOI] [PubMed] [Google Scholar]
  • 45. Ugalde-Silva P, Gonzalez-Lugo O, Navarro-Garcia F. Tight Junction Disruption Induced by Type 3 Secretion System Effectors Injected by Enteropathogenic and Enterohemorrhagic Escherichia Coli. Front Cell Infect Microbiol (2016) 6:87. doi: 10.3389/fcimb.2016.00087 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 46. Kissoon-Singh V, Moreau F, Trusevych E, Chadee K. Entamoeba Histolytica Exacerbates Epithelial Tight Junction Permeability and Proinflammatory Responses in Muc2(-/-) Mice. Am J Pathol (2013) 182:852–65. doi: 10.1016/j.ajpath.2012.11.035 [DOI] [PubMed] [Google Scholar]
  • 47. Guttman JA, Finlay BB. Tight Junctions as Targets of Infectious Agents. Biochim Biophys Acta (2009) 1788:832–41. doi: 10.1016/j.bbamem.2008.10.028 [DOI] [PubMed] [Google Scholar]
  • 48. Hardin JA, Buret AG, Olson ME, Kimm MH, Gall DG. Mast Cell Hyperplasia and Increased Macromolecular Uptake in an Animal Model of Giardiasis. J Parasitol (1997) 83:908–12. doi: 10.2307/3284287 [DOI] [PubMed] [Google Scholar]
  • 49. Teoh DA, Kamieniecki D, Pang G, Buret AG. Giardia Lamblia Rearranges F-Actin and Alpha-Actinin in Human Colonic and Duodenal Monolayers and Reduces Transepithelial Electrical Resistance. J Parasitol (2000) 86:800–6. doi: 10.1645/0022-3395(2000)086[0800:GLRFAA]2.0.CO;2 [DOI] [PubMed] [Google Scholar]
  • 50. Chin AC, Teoh DA, Scott KG, Meddings JB, Macnaughton WK, Buret AG. Strain-Dependent Induction of Enterocyte Apoptosis by Giardia Lamblia Disrupts Epithelial Barrier Function in a Caspase-3-Dependent Manner. Infect Immun (2002) 70:3673–80. doi: 10.1128/IAI.70.7.3673-3680.2002 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 51. Troeger H, Epple HJ, Schneider T, Wahnschaffe U, Ullrich R, Burchard GD, et al. Effect of Chronic Giardia Lamblia Infection on Epithelial Transport and Barrier Function in Human Duodenum. Gut (2007) 56:328–35. doi: 10.1136/gut.2006.100198 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 52. Ortega-Pierres G, Argüello-García R, Laredo-Cisneros MS, Fonseca-Linán R, Gómez-Mondragón M, Inzunza-Arroyo R, et al. Giardipain-1, a Protease Secreted by Giardia Duodenalis Trophozoites, Causes Junctional, Barrier and Apoptotic Damage in Epithelial Cell Monolayers. Int J Parasitol (2018) 48:621–39. doi: 10.1016/j.ijpara.2018.01.006 [DOI] [PubMed] [Google Scholar]
  • 53. Müller N, von Allmen N. Recent Insights Into the Mucosal Reactions Associated With Giardia Lamblia Infections. Int J Parasitol (2005) 35:1339–47. doi: 10.1016/j.ijpara.2005.07.008 [DOI] [PubMed] [Google Scholar]
  • 54. Martínez-Girón R. Potential Role of Protozoa and Tight Junctions in the Airway Epithelium Disruption. Clin Respir J (2011) 5:e6. doi: 10.1111/j.1752-699X.2010.00215.x [DOI] [PubMed] [Google Scholar]
  • 55. Halliez MC, Motta JP, Feener TD, Guérin G, LeGoff L, François A, et al. Giardia Duodenalis Induces Paracellular Bacterial Translocation and Causes Postinfectious Visceral Hypersensitivity. Am J Physiol Gastrointest Liver Physiol (2016) 310:G574–585. doi: 10.1152/ajpgi.00144.2015 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 56. Humen MA, Pérez PF, Liévin-Le Moal V. Lipid Raft-Dependent Adhesion of Giardia Intestinalis Trophozoites to a Cultured Human Enterocyte-Like Caco-2/TC7 Cell Monolayer Leads to Cytoskeleton-Dependent Functional Injuries. Cell Microbiol (2011) 13:1683–702. doi: 10.1111/j.1462-5822.2011.01647.x [DOI] [PubMed] [Google Scholar]
  • 57. Buret AG, Mitchell K, Muench DG, Scott KG. Giardia Lamblia Disrupts Tight Junctional ZO-1 and Increases Permeability in Non-Transformed Human Small Intestinal Epithelial Monolayers: Effects of Epidermal Growth Factor. Parasitology (2002) 125:11–9. doi: 10.1017/S0031182002001853 [DOI] [PubMed] [Google Scholar]
  • 58. Scott KG, Meddings JB, Kirk DR, Lees-Miller SP, Buret AG. Intestinal Infection With Giardia Spp. Reduces Epithelial Barrier Function in a Myosin Light Chain Kinase-Dependent Fashion. Gastroenterology (2002) 123:1179–90. doi: 10.1053/gast.2002.36002 [DOI] [PubMed] [Google Scholar]
  • 59. Maia-Brigagão C, Morgado-Díaz JA, De Souza W. Giardia Disrupts the Arrangement of Tight, Adherens and Desmosomal Junction Proteins of Intestinal Cells. Parasitol Int (2012) 61:280–7. doi: 10.1016/j.parint.2011.11.002 [DOI] [PubMed] [Google Scholar]
  • 60. Ortega-Pierres MG, Argüello-García R. Giardia Duodenalis: Role of Secreted Molecules as Virulent Factors in the Cytotoxic Effect on Epithelial Cells. Adv Parasitol (2019) 106:129–69. doi: 10.1016/bs.apar.2019.07.003 [DOI] [PubMed] [Google Scholar]
  • 61. Allain T, Amat CB, Motta JP, Manko A, Buret AG. Interactions of Giardia Sp. With the Intestinal Barrier: Epithelium, Mucus, and Microbiota. Tissue Barriers (2017) 5:e1274354. doi: 10.1080/21688370.2016.1274354 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 62. Argüello-García R, Ortega-Pierres MG. Giardia Duodenalis Virulence - "To Be, or Not To Be". Curr Trop Med Rep (2021) 1–11. doi: 10.1007/s40475-021-00248-z [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 63. Cotton JA, Bhargava A, Ferraz JG, Yates RM, Beck PL, Buret AG. Giardia Duodenalis Cathepsin B Proteases Degrade Intestinal Epithelial Interleukin-8 and Attenuate Interleukin-8-Induced Neutrophil Chemotaxis. Infect Immun (2014) 82:2772–87. doi: 10.1128/IAI.01771-14 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 64. Liu J, Fu Z, Hellman L, Svärd SG. Cleavage Specificity of Recombinant Giardia Intestinalis Cysteine Proteases: Degradation of Immunoglobulins and Defensins. Mol Biochem Parasitol (2019) 227:29–38. doi: 10.1016/j.molbiopara.2018.10.004 [DOI] [PubMed] [Google Scholar]
  • 65. Cabrera-Licona A, Solano-González E, Fonseca-Liñán R, Bazán-Tejeda ML, Argüello-García R, Bermúdez-Cruz RM, et al. Expression and Secretion of the Giardia Duodenalis Variant Surface Protein 9B10A by Transfected Trophozoites Causes Damage to Epithelial Cell Monolayers Mediated by Protease Activity. Exp Parasitol (2017) 179:49–64. doi: 10.1016/j.exppara.2017.06.006 [DOI] [PubMed] [Google Scholar]
  • 66. Solaymani-Mohammadi S, Singer SM. Host Immunity and Pathogen Strain Contribute to Intestinal Disaccharidase Impairment Following Gut Infection. J Immunol (2011) 187:3769–75. doi: 10.4049/jimmunol.1100606 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 67. Cevallos A, Carnaby S, James M, Farthing JG. Small Intestinal Injury in a Neonatal Rat Model of Giardiasis Is Strain Dependent. Gastroenterology (1995) 109:766–73. doi: 10.1016/0016-5085(95)90383-6 [DOI] [PubMed] [Google Scholar]
  • 68. Koh WH, Geurden T, Paget T, O'Handley R, Steuart RF, Thompson RC, et al. Giardia Duodenalis Assemblage-Specific Induction of Apoptosis and Tight Junction Disruption in Human Intestinal Epithelial Cells: Effects of Mixed Infections. J Parasitol (2013) 99:353–8. doi: 10.1645/GE-3021.1 [DOI] [PubMed] [Google Scholar]
  • 69. Bartelt LA, Roche J, Kolling G, Bolick D, Noronha F, Naylor C, et al. Persistent G. Lamblia Impairs Growth in a Murine Malnutrition Model. J Clin Invest (2013) 123:2672–84. doi: 10.1172/JCI67294 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 70. Panaro MA, Cianciulli A, Mitolo V, Mitolo CI, Acquafredda A, Brandonisio O, et al. Caspase-Dependent Apoptosis of the HCT-8 Epithelial Cell Line Induced by the Parasite Giardia Intestinalis. FEMS Immunol Med Microbiol (2007) 51:302–9. doi: 10.1111/j.1574-695X.2007.00304.x [DOI] [PubMed] [Google Scholar]
  • 71. Yu LC, Huang CY, Kuo WT, Sayer H, Turner JR, Buret AG. SGLT-1-Mediated Glucose Uptake Protects Human Intestinal Epithelial Cells Against Giardia Duodenalis-Induced Apoptosis. Int J Parasitol (2008) 38:923–34. doi: 10.1016/j.ijpara.2007.12.004 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 72. Liu L, Fang R, Wei Z, Wu J, Li X, Li W. Giardia Duodenalis Induces Apoptosis in Intestinal Epithelial Cells via Reactive Oxygen Species-Mediated Mitochondrial Pathway In Vitro. Pathogens (2020) 9:693. doi: 10.3390/pathogens9090693 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 73. Liu L, Wei Z, Fang R, Li X, Li W. Giardia Duodenalis Induces Extrinsic Pathway of Apoptosis in Intestinal Epithelial Cells Through Activation of TNFR1 and K63 De-Ubiquitination of RIP1 In Vitro. Microb Pathog (2020) 149:104315. doi: 10.1016/j.micpath.2020.104315 [DOI] [PubMed] [Google Scholar]
  • 74. Eckmann L, Laurent F, Langford TD, Hetsko ML, Smith JR, Kagnoff MF, et al. Nitric Oxide Production by Human Intestinal Epithelial Cells and Competition for Arginine as Potential Determinants of Host Defense Against the Lumen-Dwelling Pathogen Giardia Lamblia. J Immunol (2000) 164:1478–87. doi: 10.4049/jimmunol.164.3.1478 [DOI] [PubMed] [Google Scholar]
  • 75. Eckmann L. Mucosal Defences Against Giardia. Parasite Immunol (2003) 25:259–70. doi: 10.1046/j.1365-3024.2003.00634.x [DOI] [PubMed] [Google Scholar]
  • 76. Solaymani-Mohammadi S, Singer SM. Regulation of Intestinal Epithelial Cell Cytoskeletal Remodeling by Cellular Immunity Following Gut Infection. Mucosal Immunol (2013) 6:369–78. doi: 10.1038/mi.2012.80 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 77. Barigye R, Dyer NW, Newell TK, Khaitsa ML, Trout JM, Santin M, et al. Molecular and Immunohistochemical Detection of Assemblage E, Giardia Duodenalis in Scouring North Dakota Calves. Vet Parasitol (2008) 157:196–202. doi: 10.1016/j.vetpar.2008.07.033 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 78. Bhargava A, Cotton JA, Dixon BR, Gedamu L, Yates RM, Buret AG. Giardia Duodenalis Surface Cysteine Proteases Induce Cleavage of the Intestinal Epithelial Cytoskeletal Protein Villin via Myosin Light Chain Kinase. PloS One (2015) 10:e0136102. doi: 10.1371/journal.pone.0136102 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 79. Larsen SB, Cowley CJ, Fuchs E. Epithelial Cells: Liaisons of Immunity. Curr Opin Immunol (2020) 62:45–53. doi: 10.1016/j.coi.2019.11.004 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 80. López Cascales JJ, Zenak S, García de la Torre J, Lezama OG, Garro A, Enriz RD. Small Cationic Peptides: Influence of Charge on Their Antimicrobial Activity. ACS Omega (2018) 3:5390–8. doi: 10.1021/acsomega.8b00293 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 81. Iimura M, Gallo RL, Hase K, Miyamoto Y, Eckmann L, Kagnoff MF. Cathelicidin Mediates Innate Intestinal Defense Against Colonization With Epithelial Adherent Bacterial Pathogens. J Immunol (2005) 174:4901–7. doi: 10.4049/jimmunol.174.8.4901 [DOI] [PubMed] [Google Scholar]
  • 82. van Eijk M, Boerefijn S, Cen L, Rosa M, Morren MJH, van der Ent CK, et al. Cathelicidin-Inspired Antimicrobial Peptides as Novel Antifungal Compounds. Med Mycol (2020) 58:1073–84. doi: 10.1093/mmy/myaa014 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 83. Aley SB, Zimmerman M, Hetsko M, Selsted ME, Gillin FD. Killing of Giardia Lamblia by Cryptdins and Cationic Neutrophil Peptides. Infect Immun (1994) 62:5397–403. doi: 10.1128/iai.62.12.5397-5403.1994 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 84. Sonnenberg GF, Fouser LA, Artis D. Functional Biology of the IL-22-IL-22r Pathway in Regulating Immunity and Inflammation at Barrier Surfaces. Adv Immunol (2010) 107:1–29. doi: 10.1016/B978-0-12-381300-8.00001-0 [DOI] [PubMed] [Google Scholar]
  • 85. Paerewijck O, Maertens B, Dreesen L, Van Meulder F, Peelaers I, Ratman D, et al. Interleukin-17 Receptor A (IL-17RA) as a Central Regulator of the Protective Immune Response Against Giardia. Sci Rep (2017) 7:8520. doi: 10.1038/s41598-017-08590-x [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 86. Manko A, Motta JP, Cotton JA, Feener T, Oyeyemi A, Vallance BA, et al. Giardia Co-Infection Promotes the Secretion of Antimicrobial Peptides Beta-Defensin 2 and Trefoil Factor 3 and Attenuates Attaching and Effacing Bacteria-Induced Intestinal Disease. PloS One (2017) 12:e0178647. doi: 10.1371/journal.pone.0178647 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 87. Manko-Prykhoda A, Allain T, Motta JP, Cotton JA, Feener T, Oyeyemi A, et al. Giardia Spp. Promote the Production of Antimicrobial Peptides and Attenuate Disease Severity Induced by Attaching and Effacing Enteropathogens via the Induction of the NLRP3 Inflammasome. I. Nt J Parasitol (2020) 50:263–75. doi: 10.1016/j.ijpara.2019.12.011 [DOI] [PubMed] [Google Scholar]
  • 88. Inge PM, Edson CM, Farthing MJ. Attachment of Giardia Lamblia to Rat Intestinal Epithelial Cells. Gut (1988) 29:795–801. doi: 10.1136/gut.29.6.795 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 89. Nash TE. Long-Term Culture of Giardia Lamblia in Cell Culture Medium Requires Intimate Association With Viable Mammalian Cells. Infect Immun (2019) 87:e00639–19. doi: 10.1128/IAI.00639-19 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 90. Owen RL, Nemanic PC, Stevens DP. Ultrastructural Observations on Giardiasis in a Murine Model. I. Intestinal Distribution, Attachment, and Relationship to the Immune System of Giardia Muris . Gastroenterology (1979) 76:757–69. doi: 10.1016/S0016-5085(79)80176-6 [DOI] [PubMed] [Google Scholar]
  • 91. Brandborg LL, Tankersley CB, Gottieb S, Barancik M, Sartor VE. Histological Demonstration of Mucosal Invasion by Giardia Lamblia in Man. Gastroenterology (1967) 52:143–50. doi: 10.1016/S0016-5085(67)80001-5 [DOI] [PubMed] [Google Scholar]
  • 92. Saha TK, Ghosh TK. Invasion of Small Intestinal Mucosa by Giardia Lamblia in Man. Gastroenterology (1977) 72:402–5. doi: 10.1016/S0016-5085(77)80247-3 [DOI] [PubMed] [Google Scholar]
  • 93. Reynoso-Robles R, Ponce-Macotela M, Rosas-López LE, Ramos-Morales A, Martínez-Gordillo MN, González-Maciel A. The Invasive Potential of Giardia Intestinalis in an In Vivo Model. Sci Rep (2015) 5:15168. doi: 10.1038/srep15168 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 94. Dharmani P, Srivastava V, Kissoon-Singh V, Chadee K. Role of Intestinal Mucins in Innate Host Defense Mechanisms Against Pathogens. J Innate Immun (2009) 1:123–35. doi: 10.1159/000163037 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 95. Solaymani-Mohammadi S, Petri WA., Jr. Intestinal Invasion by Entamoeba Histolytica. Subcell Biochem (2008) 47:221–32. doi: 10.1007/978-0-387-78267-6_18 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 96. Bansil R, Turner BS. The Biology of Mucus: Composition, Synthesis and Organization. Adv Drug Deliv Rev (2018) 124:3–15. doi: 10.1016/j.addr.2017.09.023 [DOI] [PubMed] [Google Scholar]
  • 97. Lamont JT. Mucus: The Front Line of Intestinal Mucosal Defense. Ann NY Acad Sci (1992) 664:190–201. doi: 10.1111/j.1749-6632.1992.tb39760.x [DOI] [PubMed] [Google Scholar]
  • 98. Vimal D, Khullar M, Gupta S, Ganguly N. Intestinal Mucins: The Binding Sites for Salmonella Typhimurium. Mol Cell Biochem (2000) 204:107–17. doi: 10.1023/A:1007015312036 [DOI] [PubMed] [Google Scholar]
  • 99. Linden SK, Sutton P, Karlsson NG, Korolik V, McGuckin MA. Mucins in the Mucosal Barrier to Infection. Mucosal Immunol (2008) 1:183–97. doi: 10.1038/mi.2008.5 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 100. McGuckin MA, Linden SK, Sutton P, Florin TF. Mucin Dynamics and Enteric Pathogens. Nat Rev Microbiol (2011) 9:265–78. doi: 10.1038/nrmicro2538 [DOI] [PubMed] [Google Scholar]
  • 101. Leitch GJ, Visvesvara GS, Wahlquist SP, Harmon CT. Dietary Fiber and Giardiasis: Dietary Fiber Reduces Rate of Intestinal Infection by Giardia Lamblia in the Gerbil. Am J Trop Med Hyg (1989) 41:512–20. doi: 10.4269/ajtmh.1989.41.512 [DOI] [PubMed] [Google Scholar]
  • 102. Macechko PT, van Keulen H, Jarroll EL, Mulgrew T, Gurien A, Erlandsen SL. Detection of Giardia Trophozoites in Archival Pathology Specimens of Human Small Intestine. Microsc Microanal (1998) 4:397–403. doi: 10.1017/S1431927698980370 [DOI] [PubMed] [Google Scholar]
  • 103. Ventura LL, Oliveira DR, Viana JC, Santos JF, Caliari MV, Gomes MA. Impact of Protein Malnutrition on Histological Parameters of Experimentally Infected Animals With Giardia Lamblia. Exp Parasitol (2013) 133:391–5. doi: 10.1016/j.exppara.2013.01.007 [DOI] [PubMed] [Google Scholar]
  • 104. Amat CB, Motta JP, Fekete E, Moreau F, Chadee K, Buret AG. Cysteine Protease Dependent Mucous Disruptions and Differential Mucin Gene Expression in Giardia Duodenalis Infection. Am J Pathol (2017) 187:2486–98. doi: 10.1016/j.ajpath.2017.07.009 [DOI] [PubMed] [Google Scholar]
  • 105. Araújo NS, Mundim MJ, Gomes MA, Amorim RM, Viana JC, Queiroz RP, et al. Giardia Duodenalis: Pathological Alterations in Gerbils, Meriones Unguiculatus, Infected With Different Dosages of Trophozoites. Exp Parasitol (2008) 118:449–57. doi: 10.1016/j.exppara.2007.10.007 [DOI] [PubMed] [Google Scholar]
  • 106. Ma'ayeh SY, Knörr L, Sköld K, Garnham A, Ansell BRE, Jex AR, et al. Responses of the Differentiated Intestinal Epithelial Cell Line Caco-2 to Infection With the Giardia Intestinalis GS Isolate. Front Cell Infect Microbiol (2018) 8:244. doi: 10.3389/fcimb.2018.00244 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 107. Roskens H, Erlandsen SL. Inhibition of In Vitro Attachment of Giardia Trophozoites by Mucin. J Parasitol (2002) 88:869–73. doi: 10.1645/0022-3395(2002)088[0869:IOIVAO]2.0.CO;2 [DOI] [PubMed] [Google Scholar]
  • 108. Zenian AJ, Gillin FD. Intestinal Mucus Protects Giardia Lamblia From Killing by Human Milk. J Protozool (1987) 34:22–6. doi: 10.1111/j.1550-7408.1987.tb03124.x [DOI] [PubMed] [Google Scholar]
  • 109. Zenian A, Gillin FD. Interactions of Giardia Lamblia With Human Intestinal Mucus: Enhancement of Trophozoite Attachment to Glass. J Protozool (1985) 32:664–8. doi: 10.1111/j.1550-7408.1985.tb03098.x [DOI] [PubMed] [Google Scholar]
  • 110. Gault MJ, Gillin FD, Zenian AJ. Giardia Lamblia: Stimulation of Growth by Human Intestinal Mucus and Epithelial Cells in Serum Free Medium. Exp Parasitol (1987) 64:29–37. doi: 10.1016/0014-4894(87)90005-1 [DOI] [PubMed] [Google Scholar]
  • 111. Connaris S, Greenwell P. Glycosidases in Mucin-Dwelling Protozoans. Glycoconj J (1997) 14:879–82. doi: 10.1023/A:1018554408558 [DOI] [PubMed] [Google Scholar]
  • 112. Ponce-Macotela M, González-Maciel A, Reynoso-Robles R, Martínez-Gordillo MN. Goblet Cells: Are They an Unspecific Barrier Against Giardia Intestinalis or a Gate? Parasitol Res (2008) 102:509–13. doi: 10.1007/s00436-007-0790-6 [DOI] [PubMed] [Google Scholar]
  • 113. Vahouny GV, Le T, Ifrim I, Satchithanandam S, Cassidy MM. Stimulation of Intestinal Cytokinetics and Mucin Turnover in Rats Fed Wheat Bran or Cellulose. Am J Clin Nutr (1985) 41:895–900. doi: 10.1093/ajcn/41.5.895 [DOI] [PubMed] [Google Scholar]
  • 114. Cornick S, Tawiah A, Chadee K. Roles and Regulation of the Mucus Barrier in the Gut. Tissue Barriers (2015) 3:e982426. doi: 10.4161/21688370.2014.982426 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 115. Desai MS, Seekatz AM, Koropatkin NM, Kamada N, Hickey CA, Wolter M, et al. A Dietary Fiber-Deprived Gut Microbiota Degrades the Colonic Mucus Barrier and Enhances Pathogen Susceptibility. Cell (2016) 167:1339–1353.e21. doi: 10.1016/j.cell.2016.10.043 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 116. Babaei Z, Malihi N, Zia-Ali N, Sharifi I, Mohammadi MA, Kagnoff MF, et al. Adaptive Immune Response in Symptomatic and Asymptomatic Enteric Protozoal Infection: Evidence for a Determining Role of Parasite Genetic Heterogeneity in Host Immunity to Human Giardiasis. Microbes Infect (2016) 18:687–95. doi: 10.1016/j.micinf.2016.06.009 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 117. Gillon J, Al Thamery D, Ferguson A. Features of Small Intestinal Pathology (Epithelial Cell Kinetics, Intraepithelial Lymphocytes, Disaccharidases) in a Primary Giardia Muris Infection. Gut (1982) 23:498–506. doi: 10.1136/gut.23.6.498 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 118. Vinayak VK, Khanna R, Kum K. Kinetics of Intraepithelium and Lamina Propria Lymphocyte Responses During Giardia Lamblia Infection in Mice. Microb Pathog (1991) 10:343–50. doi: 10.1016/0882-4010(91)90079-P [DOI] [PubMed] [Google Scholar]
  • 119. Hanevik K, Kristoffersen E, Svard S, Bruserud O, Ringqvist E, Sørnes S, et al. Human Cellular Immune Response Against Giardia Lamblia 5 Years After Acute Giardiasis. J Infect Dis (2011) 204:1779–86. doi: 10.1093/infdis/jir639 [DOI] [PubMed] [Google Scholar]
  • 120. Saghaug CS, Sørnes S, Peirasmaki D, Svärd S, Langeland N, Hanevik K. Human Memory CD4+ T Cell Immune Responses Against Giardia Lamblia. Clin Vaccine Immunol (2015) 23:11–8. doi: 10.1128/CVI.00419-15 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 121. Keselman A, Li E, Maloney J, Singer SM. The Microbiota Contributes to CD8+ T Cell Activation and Nutrient Malabsorption Following Intestinal Infection With Giardia Duodenalis. Infect Immun (2016) 84:2853–60. doi: 10.1128/IAI.00348-16 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 122. Roxström-Lindquist K, Ringqvist E, Palm D, Svärd S. Giardia Lamblia-Induced Changes in Gene Expression in Differentiated Caco-2 Human Intestinal Epithelial Cells. Infect Immun (2005) 73:8204–8. doi: 10.1128/IAI.73.12.8204-8208.2005 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 123. Stadelmann B, Merino MC, Persson L, Svärd SG. Arginine Consumption by the Intestinal Parasite Giardia Intestinalis Reduces Proliferation of Intestinal Epithelial Cells. PloS One (2012) 7:e45325. doi: 10.1371/journal.pone.0045325 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 124. Fisher BS, Estraño CE, Cole JA. Modeling Long-Term Host Cell-Giardia Lamblia Interactions in an In Vitro Co-Culture System. PloS One (2013) 8:e81104. doi: 10.1371/journal.pone.0081104 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 125. Lee HY, Hyung S, Lee NY, Yong TS, Han SH, Park SJ. Excretory-Secretory Products of Giardia Lamblia Induce Interleukin-8 Production in Human Colonic Cells via Activation of P38, ERK1/2, NF-κb and AP-1. Parasite Immunol (2012) 34:183–98. doi: 10.1111/j.1365-3024.2012.01354.x [DOI] [PubMed] [Google Scholar]
  • 126. Cotton JA, Motta JP, Schenck LP, Hirota SA, Beck PL, Buret AG. Giardia Duodenalis Infection Reduces Granulocyte Infiltration in an In Vivo Model of Bacterial Toxin-Induced Colitis and Attenuates Inflammation in Human Intestinal Tissue. PloS One (2014) 9:e109087. doi: 10.1371/journal.pone.0109087 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 127. Farthing MJ. The Molecular Pathogenesis of Giardiasis. J Pediatr Gastroenterol Nutr (1997) 24:79–88. doi: 10.1097/00005176-199701000-00018 [DOI] [PubMed] [Google Scholar]
  • 128. Gericke B, Amiri M, Naim HY. The Multiple Roles of Sucrase-Isomaltase in the Intestinal Physiology. Mol Cell Pediatr (2016) 3:2. doi: 10.1186/s40348-016-0033-y [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 129. Taylor C, Hodgson K, Sharpstone D, Sigthorsson G, Coutts M, Sherwood R, et al. The Prevalence and Severity of Intestinal Disaccharidase Deficiency in Human Immunodeficiency Virus-Infected Subjects. Scand J Gastroenterol (2000) 35:599–606. doi: 10.1080/003655200750023552 [DOI] [PubMed] [Google Scholar]
  • 130. Mones RL, Yankah A, Duelfer D, Bustami R, Mercer G. Disaccharidase Deficiency in Pediatric Patients With Celiac Disease and Intact Villi. Scand J Gastroenterol (2011) 46:1429–34. doi: 10.3109/00365521.2011.619276 [DOI] [PubMed] [Google Scholar]
  • 131. Jennings W, Rowland R, Hecker R, Gibson GE, Fitch RJ, Reid DP. The Significance of Lowered Jejunal Disaccharidase Levels. Aust N Z J Med (1976) 6:556–60. doi: 10.1111/j.1445-5994.1976.tb03994.x [DOI] [PubMed] [Google Scholar]
  • 132. Ochs HD, Ament ME, Davis SD. Structure and Function of the Gastrointestinal Tract in Primary Immunodeficiency Syndromes (IDS) and in Granulocyte Dysfunction. Birth Defects Orig Artic Ser (1975) 11:199–207. [PubMed] [Google Scholar]
  • 133. Judd R, Deckelbaum RJ, Weizman Z, Granot E, Ron N, Okon E. Giardiasis in Childhood: Poor Clinical and Histological Correlations. Isr J Med Sci (1983) 19:818–23. [PubMed] [Google Scholar]
  • 134. Singh KD, Bhasin DK, Rana SV, Vaiphei K, Katyal R, Vinayak VK, et al. Effect of Giardia Lamblia on Duodenal Disaccharidase Levels in Humans. Trop Gastroenterol (2000) 21:174–6. [PubMed] [Google Scholar]
  • 135. Ish-Horowicz M, Korman SH, Shapiro M, Har-Even U, Tamir I, Strauss N, et al. Asymptomatic Giardiasis in Children. Pediatr Infect Dis J (1989) 8:773–9. doi: 10.1097/00006454-198911000-00009 [DOI] [PubMed] [Google Scholar]
  • 136. Gendrel D, Richard-Lenoble D, Kombila M, Dupont C, Moreno JL, Gendrel C, et al. Influence of Intestinal Parasitism on Lactose Absorption in Well-Nourished African Children. Am J Trop Med Hyg (1992) 46:137–40. doi: 10.4269/ajtmh.1992.46.137 [DOI] [PubMed] [Google Scholar]
  • 137. Anand BS, Chaudhary R, Jyothi A, Yadev RS, Baveja UK. Experimental Examination of the Direct Damaging Effects of Giardia Lamblia on Intestinal Mucosal Scrapings of Mice. Trans R Soc Trop Med Hyg (1985) 79:613–7. doi: 10.1016/0035-9203(85)90167-1 [DOI] [PubMed] [Google Scholar]
  • 138. Khanna R, Vinayak VK, Mehta S, KumKum, Nain CK. Giardia Lamblia Infection in Immunosuppressed Animals Causes Severe Alterations to Brush Border Membrane Enzymes. Dig Dis Sci (1988) 33:1147–52. doi: 10.1007/BF01535792 [DOI] [PubMed] [Google Scholar]
  • 139. Belosevic M, Faubert GM, MacLean JD. Disaccharidase Activity in the Small Intestine of Gerbils (Meriones Unguiculatus) During Primary and Challenge Infections With Giardia Lamblia. Gut (1989) 30:1213–9. doi: 10.1136/gut.30.9.1213 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 140. Mohammed SR, Faubert GM. Disaccharidase Deficiencies in Mongolian Gerbils (Meriones Unguiculatus) Protected Against Giardia Lamblia. Parasitol Res (1995) 81:582–90. doi: 10.1007/BF00932025 [DOI] [PubMed] [Google Scholar]
  • 141. Daniels CW, Belosevic M. Disaccharidase Activity in the Small Intestine of Susceptible and Resistant Mice After Primary and Challenge Infections With Giardia Muris. Am J Trop Med Hyg (1992) 46:382–90. doi: 10.4269/ajtmh.1992.46.382 [DOI] [PubMed] [Google Scholar]
  • 142. Daniels CW, Belosevic M. Disaccharidase Activity in Male and Female C57BL/6 Mice Infected With Giardia Muris. Parasitol Res (1995) 81:143–7. doi: 10.1007/BF00931620 [DOI] [PubMed] [Google Scholar]
  • 143. Bénéré E, Van Assche T, Van Ginneken C, Peulen O, Cos P, Maes L. Intestinal Growth and Pathology of Giardia Duodenalis Assemblage Subtype A(I), A(II), B and E in the Gerbil Model. Parasitology (2012) 139:424–33. doi: 10.1017/S0031182011002137 [DOI] [PubMed] [Google Scholar]
  • 144. Scott KG, Logan MR, Klammer GM, Teoh DA, Buret AG. Jejunal Brush Border Microvillous Alterations in Giardia Muris-Infected Mice: Role of T Lymphocytes and Interleukin-6. Infect Immun (2000) 68:3412–8. doi: 10.1128/IAI.68.6.3412-3418.2000 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 145. Scott KG, Yu LC, Buret AG. Role of CD8+ and CD4+ T Lymphocytes in Jejunal Mucosal Injury During Murine Giardiasis. Infect Immun (2004) 72:3536–42. doi: 10.1128/IAI.72.6.3536-3542.2004 [DOI] [PMC free article] [PubMed] [Google Scholar]

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