Skip to main content
NCBI home page
Heliyon logoLink to Heliyon
. 2020 Oct 7;6(10):e05129. doi: 10.1016/j.heliyon.2020.e05129

Association of genetic polymorphism at tumor necrosis factor-α gene promoter - 1031T/C and parasitic infections among children in Northern South Africa

NC Davhana a, AK ElBakri b,∗, PO Bessong a, A Samie a
PMCID: PMC7553974  PMID: 33083607

Abstract

Intestinal parasitic diseases are common in developing countries including South Africa and have been documented to be the most common in children under the age of five. The present study aimed to identify any potential association that may exist between TNF-α promoter gene polymorphism and parasitic infections. A total of 199 blood samples were evaluated from children who were part of the MAL-ED study cohort. The DNA was used to investigate polymorphism in the promoter region of the TNF-α gene at position -1031T/C. The polymorphisms were detected by polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) assay. The TC genotype at position -1031 was significantly higher in healthy controls children than in children who were infected with Entamoeba species (59.9% vs 29.4%, P = 0.015) and Entamoeba coli (59.1% vs 30.8%, P = 0.046), indicating that TC genotype may be protective against Entamoeba infections and Entamoeba coli infections. The CC genotype at position -1031 was more common among children with parasite and diarrhea and the results was statistically significant (P = 0.04). This study has revealed that the CC genotype may be is a risk factor for symptomatic parasitic infections while the TC genotype might be protective of Entamoeba infections among children in Dzimauli community.

Keywords: Genetics, Immunology, Microbiology, Molecular biology, TNF-α, PCR-RFLP, Dzimauli community, Limpopo province, South Africa

Genetics; Immunology; Microbiology; Molecular Biology; TNF-α; PCR-RFLP; Dzimauli community; Limpopo Province; South Africa

1. Introduction

Gastrointestinal parasitic diseases are among the most prevalent infections worldwide, especially in children younger than five years (Ul-Wadood et al., 2005). It is estimated that intestinal parasites affect around 3.5 billion people, particularly in areas of poor sanitation, inadequate water supply and poor hygiene practices (Pullan et al., 2014). Entamoeba species, Cryptosporidium parvum, Giardia lamblia, Cyclospora and Balantidium coli are among few of the orofecally and/or zoonotically transmitted intestinal parasites that have been documented to be the most common in children under the age of five (Ahmed et al., 2018). Most of these protozoan parasitic infections are generally asymptomatic with only a few manifesting into acute and/or chronic infections. However, despite significant efforts, the precise factors determining the outcome of these infections still remain unknown. Nevertheless, diarrhea is one of the main manifestations of these illnesses (Fischer Walker et al., 2012).

A multifunctional proinflammatory cytokine, TNF- α plays a crucial role in the induction and adaptation of the immune system. It activates inflammatory white blood cells, recruits neutrophils and promotes macrophages to produce other cytokines, such as interleukin (IL)-1 and IL-6 leading to tissue inflammation (Lee et al., 2002; Derouich-Guergour et al., 2001). It can also increase cell permeability, resulting in impairment of barrier function and edema formation (Durmaz et al., 1998). Furthermore, TNF-α is an important inflammatory cytokine involved in the development of resistance to dissimilar microbes including protozoa (Burns et al., 1996; Lean et al., 2006).

Significant genetic variation and polymorphism has been reported in TNF-α, mainly in the promoter region responsible for the transcriptional regulation of the TNF-α gene. Elevated levels of the cytokine have been observed in certain gastrointestinal tract illnesses such as in the case of inflammatory colitis and inflammatory bowel disease (IBD) (Ekhlas et al., 2013). Furthermore, administration of anti-TNF agents has been proven to be effective treatment options for some individuals (Enriquez and Michael, 1998). To our knowledge, not many studies have examined the association between genetic polymorphisms at the TNF-α promoter regions and parasitic infections. Thus, in this study, we aimed to investigate whether one of the common polymorphisms in the promoter region of TNF-α (1031T/C) is associated with gastrointestinal tract parasitic infections among children under the aged of five in Northern South Africa.

2. Materials and methods

2.1. Ethical considerations

The present study was part of the MalEd study in the South African site which has been previously described (Bessong et al., 2014). The study was approved by the research and ethics committee of the University of Venda and the Department of Health and Welfare in Polokwane, Limpopo province, South Africa. The objectives of the study were clearly explained to the participants and those who agreed to participate in the research were requested to sign consent forms and complete the questionnaires in order to obtain socio-demographic information. These tools have been fairly described in previous publications (Houpt et al., 2014; Richard et al., 2014). Confidentiality of the participants was kept by giving to each a code. The information obtained from the participants was kept confidential.

2.1.1. Study sites

The study was conducted in the Dzimauli community under Mutale Municipality, Vhembe District, Limpopo Province which is comprised of 9 settlements aligned linearly and adjacent to one another. It is the site of the MalEd study in the South African site previously described (Bessong et al., 2014). The areas are rural with people of different religious, educational and socio-economic backgrounds, living in neighborhoods with distinctly different level of sanitation. Five of the nine settlements (Tshibvumo, Tshapasha, Thongwe, Matshavhawe and Pile) have been identified as the primary areas of the study for the Enteric Infections and Malnutrition (Mal-Ed) project in Limpopo, South Africa.

2.2. Sample collection, processing and genomic DNA extraction

We evaluated 199 blood samples from children who were part of the MAL-ED study cohort. Each sample was labeled with the patient's code, sex, age and the collection date and taken to the University of Venda microbiology laboratory for analysis. Upon arrival all samples were kept on the bench overnight for separation of plasma, buffy coat and red blood cells. DNA was extracted from blood buffy coat using Gen-Elute™ blood genomic kit from Sigma Aldrich following instructions from the manufacturer. Briefly 20μl of proteinase K solution was placed into 1.5ml micro-centrifuge tubes where 200μl of blood buffy coat was added. 200μl of lysis solution C was added to the sample which was vortexed for 15 s. The sample mixture was then incubated at 55 °C for 10 min. The samples were prepared for binding by adding 200μl of ethanol to the mixture and vortexed again for 10 s. The entire mixture was transferred to a column which was first prepared by addition of 500μl of column preparation solution and centrifuged at 12000 rpm for 1 min. The columns were then washed twice with the addition of wash solutions, and centrifuged for 3 min at maximum speed. The DNA was then eluted by pipetting a 200μl of elution solution into the center of the column directly and centrifuged for 1 min at maximum speed. The DNA was then stored in the freezer at -200C until further analysis.

Stool samples from the participants were tested for parasites using parasitological methods as previously described (Platts-Mills et al., 2014).

2.3. PCR-RFLP analysis of TNF-α

Genomic DNA was used to investigate the polymorphism in the promoter region of the TNF-α gene at position -1031T/C using polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) assay as previously described by Naderi et al. (2014). Genotyping for the -1031T/C was performed using a PCR fragment amplified by the forward (5′-GGGGAGAACAAAAGGATAAG-3′) and reverse (5′-CCCCATACTCGACTTTCATA-3′) primer pairs. Briefly, a total of 30 cycles was carried out; each of these consisted of 95 °C for 30s, 55 °C for 30s, 72 °C for 30s. There was an initial denaturation step at 95°C for 5 min and a final extension step at 72 °C for 5 min. The 1031T/C polymorphism (C allele, 180 + 71+13bp; T allele, 251 + 13bp) was later evaluated by digestion with the restriction enzyme BbsI as described by the manufacturer (New England Biolabs, Ipswich MA, USA) at 37 °C for 16h. Digested PCR fragments were separated by a 4% of agarose gel electrophoresis and visualized by ethidium bromide staining.

2.4. Statistical analyses

Statistical analysis was performed using the chi-square test to determine statistical associations between the genotype distribution and the occurrence of parasitic infections. P-value less than 0.05 were considered statistically significant. Odds ratio (OR) and 95% confidence intervals (CI) were also calculated. All data analysis was conducted using SPSS software, version 24.

3. Results

3.1. The overall demographic and clinical characteristics of the study population

A total of 199 blood samples were collected from 199 participants who were part of the MalEd study (The MAL-ED Network Investigators, 2014), of which 94 (47.2%) were males and 105 (52.8%) were females. Table 1 summarizes the demographic data of the study population. Of the 199 blood samples collected, 182 (91.5%) never had any Entamoeba species while 17 (8.5%) had Entamoeba species. From the study population, about 98 (49.2%) participants were found to had been infected with Giardia lamblia followed by Cryptosporidium with 56 (28.1%), Entamoeba coli with 13 (6.5%), Balantidium with 12 (6.0%). Of all children, only 1 (0.5%) was found to had infected with Cyclospora (Figure 1).

Table 1.

Demographic and clinical features of the study population.

Characteristics Frequency Percentage (%)
Gender Male 94 47.2%
Female 105 52.8%
Low birth weight Never had low birth weight 176 88.4
Had low BWT 23 11.6
High birth weight Never had high weight 159 79.9
Had high birth weight 40 20.1
Colostrum No colostrum 7 3.5
Colostrum 192 96.5
Diarrhea Had no diarrhea at all 75 37.7
Had had at least one diarrheal episode 124 62.3
Vomit Never had any vomiting episode 177 88.9
Had had at least one episode of Vomiting 22 11.1
Fever Never had any fever episode 176 88.4
Had had at least one fever episode 23 11.6
Acute lower respiratory infection (ALRI) Never had an ALRI episode 120 60.3
Had had at least one ALRI episode 79 39.7
Open in a new tab

Figure 1.

Figure 1

Open in a new tab

Occurrence of some parasitic organisms in the study population.

3.2. Prevalence of parasite and infection in the study population

Of the total number of participants, 27.6% had been infected with parasite and exhibited acute lower respiratory tract infection while 72.4% participant had no parasite infection nor had shown acute lower respiratory infection. On the other hand, 54.3% of the children never had been infected with parasite and nor had diarrhea whereas 45.7% had had infections with a parasite with diarrhea. Of the 199 children, only 80 (40.2%) were found to had been infected with parasite and exhibited illness except 59.8% had never been infected with parasite and illness.

3.3. Association of TNF-α -1031T/C polymorphism with Entamoeba species, Entamoeba coli, Cryptosporidium parvum, Giardia lamblia, Balantidium coli and Cyclospora

Table 3 illustrates the association between TNF-α -1031T/C polymorphism, Entamoeba species, Entamoeba coli, Cryptosporidium parvum, Giardia lamblia, Balantidium coli and Cyclospora. The CC and TT genotypes at position -1031T/C were more common among children with Entamoeba species than in the control group even though the results were insignificant (P = 0.106, X2 = 2.606, OR = 2.640, 95% CI = 0.781–8.916) and (P = 0.139, X2 = 2.192, OR = 2.107, 95% CI = 0.772–5.751); respectively. On the other hand, TC genotype was common and statistically significant in children who had no Entamoeba species (P = 0.015, X2 = 5.902, OR = 0.279, 95% CI = 0.094–1.825). Similarly, both the CC and TT genotypes was more common among children with Entamoeba coli than the control group with the results being statistically insignificant (P = 0.179, X2 = 1.805, OR = 2.490, 95% CI = 0.632–9.810) and (P = 0.227, X = 1.459, OR = 1.990, 95% CI = 0.772–5.751). However, the TC genotype was frequent and statistically significant in children who had no Entamoeba coli (P = 0.046, X2 = 3.997, OR = 0.307, 95% CI = 0.091–1.033). On the other hand, the CC genotype noted to have been more frequent and statistically significant among children with Cyclospora infections P = 0.006, X2 = 7.691, OR = 1.045, 95% CI = 0.958–1.141) (Table 2).

Table 3.

TNF- α genotype at position -1031T/C in patients with parasite and diarrhea, parasite and acute lower respiratory infection, and parasite and illness.

Characteristics Did not have the condition Those that had the condition Significance OR 95% CI
Parasite and diarrhea CC 6 (5.6%) 17 (18.7%) P = 0.04 (χ2 = 8.324) 3.905 1.469–10.381
TC 63 (58.3%) 51 (56.0%) P = 0.106 (χ2 = 0.745) 0.911 0.518–1.600
TT 39 (36.1%) 23 (25.3%) P = 0.100 (χ2 = 2.704) 0.598 0.324–1.106
Parasite and acute lower respiratory infection CC 11(7.6%) 12(21.8%) P = 0.005 (χ2= 7.828) 3.374 1.389–8.196
TC 85 (59.0%) 29 (52.7%) P = 0.422 (χ2 = 0.646) 0.774 0.414–1.446
TT 48 (33.3%) 14 (25.5%) P = 0.283 (χ2 = 1.152) 0.683 0.340–1.373
Parasite and any illness CC 9(7.6%) 14(17.5%) P = 0.032 (χ2= 4.621) 2.593 1.063–6.321
TC 66 (55.5%) 48 (60.0%) P = 0.403 (χ2 = 0.526) 1.205 0.678–2.141
TT 44(37.0%) 18(22.5%) P = 0.031 (χ2= 4.673) 0.495 0.260–0.942
Open in a new tab

Note: Illness here represents any type of illness identified in the child at the time of sample collection including any of the following: Diarrhea, Acute lower respiratory syndrome, Vomiting and Fever.

The results were found significant if the P value was less than 0.05 and are indicated in bold.

Table 2.

TNF- α genotype at position -1031T/C in patients with Entamoeba species, Entamoeba coli, Cryptosporidium parvum, Giardia lamblia, Balantidium and Cyclospora.

Did not have the infection Had the infection Significance OR 95% CI
Entamoeba spp CC 19 (10.4%) 4 (23.5%) P = 0.106 (χ2 = 2.606) 2.640 0.781–8.916
TC 109(59.9%) 5(29.4%) P = 0.015 (χ2= 5.902) 0.279 0.094–1.825
TT 54 (29.7%) 8 (47.1%) P = 0.139 (χ2 = 2.192) 2.107 0.772–5.751
Entamoeba coli CC 20 (10.8%) 3 (23.1%) P = 0.179 (χ2 = 1.805) 2.490 0.632–9.810
TC 110(59.1%) 4(30.8%) P = 0.046 (χ2= 3.997) 0.307 0.091–1.033
TT 56 (30.1%) 6 (46.2%) P = 0.227 (χ2 = 1.459) 1.990 0.640–6.188
Giardia lamblia CC 10 (9.9%) 13 (13.3%) P = 0.458 (χ2 = 0.551) 1.392 0.580–3.341
TC 57 (56.4%) 57 (58.2%) P = 0.061 (χ2 = 805) 1.073 0.612–1.882
TT 34 (33.7%) 28 (28.6%) P = 0.438 (χ2 = 601) 0.788 0.432–1.439
Balantidium coli CC 20 (10.7%) 3 (25.0%) P = 0.133 (χ2 = 2.257) 2.783 0.696–11.136
TC 108 (57.8%) 6 (25.0%) P = 0.277 (χ2 = 0.599) 0.731 0.227–2.353
TT 59 (31.6%) 3 (25.0%) P = 0.226 (χ2 = 0.635) 0.723 0.189–2.769
Cyclospora CC 22(11.1%) 1(100.0%) P = 0.006 (χ2= 7.691) 1.045 0.958–1.141
TC 114 (57.6%) 0 (0.0%) P = 0.246 (χ2 = 1.348) 0.988 0.966–1.011
TT 62 (31.3%) 0 (0.0%) P = 0.455 (χ2 = 0.500) 0.993 0.979–1.007
Cryptosporidium parvum CC 16 (11.2%) 7 (12.5%) P = 0.068 (χ2 = 0.795) 1.134 0.440–2.924
TC 78 (54.5%) 36 (64.3%) P = 0.212 (χ2 = 1.560) 1.500 0.792–2.839
TT 49 (34.3%) 13 (23.2%) P = 0.130 (χ2 = 2.291 0.580 0.285–1.180
Open in a new tab

The results were found significant if the P value was less than 0.05 and are indicated in bold.

3.4. Association of TNF- α -1031T/C polymorphism with parasite and diarrhea, parasite and acute lower respiratory infection, and parasite and illness

Table 3 illustrates the association between TNF- α -1031T/C polymorphism and the overall parasite and diarrhea, acute lower respiratory infection, and illness. The CC genotype at position -1031T/C was statistically significant among children with overall parasite and diarrhea (P = 0.04, X2 = 8.324, OR = 3.905, 95% CI = 1.469–10.381), with overall parasite and acute lower respiratory infection (P = 0.005, X2 = 7.828, OR = 3.374, 95% CI = 1.389–8.196), and those with overall parasite and illness (P = 0.032, X2 = 4.621, OR = 2.593, 95% CI = 1.063–6.321). On the other hand, TT genotype was significantly abundant in healthy individuals (37.0%) than children who had parasite and illness (22.5%) (P = 0.031, X2 = 4.673, OR = 0.495, 95% CI = 0.260–0.942) (Table 3).

4. Discussion

Enteric protozoan parasites like Entamoeba histolytica, Cryptosporidium parvum and Giardia lamblia are regarded as a serious public health problem and important causes of diarrheal disease (Xiao, 2010; Yaoyu and Xiao, 2011). Millions of people are annually infected with E. histolytica and G. lamblia, making the diseases a major cause of morbidity worldwide (Teles et al., 2011). Cytokines play important roles in the activation and regulation of human immune responses and their production are variable due to single nucleotide polymorphisms (Ollier, 2004). No evidence on the association between TNF-α and parasitic infections in Limpopo Province of South Africa, particularly in the rural areas. Furthermore, the role of host genetic factors that might contribute to the burden of diseases has never been studied especially in districts within the Limpopo Province. Therefore, there is a need to identify any potential association that may exist between TNF-α promoter gene polymorphisms and parasitic infections.

Of the study participants (ages 0–5 years) with and without diarrhea recruited in this analysis, 28.1% were positive for Cryptosporidium species. This result is higher than those reported from Ethiopia and Tanzania with 9.4% and 10.4% positive rates, respectively (Kabayiza et al., 2014 and Nasser, 2016). The current study revealed a prevalence of 49.2% with Giardia lamblia among children less than 5 years. This is unlike a report by Naz et al. (2018), in which they observed a much less prevalence (11.1%) among children of the same age range as those in the current survey. On the other hand, a much lower prevalence of Cyclospora (0.5%) was determined in the study group unlike a Nepalese survey where a 7.9% was reported among diarrheal children (Sherchan et al., 2010).

The present study also examined any possible association between TNF-α promoter gene polymorphism at position -1031T/C with parasitic infections. Our study found an association between differences in the TNF-α promoter gene polymorphism at position -1031T/C and susceptibility to the development of parasitic diseases leading us to postulate that these polymorphic differences might play an important role in the pathophysiology of these parasitic diseases.

Previous studies have shown conflicting results regarding the role of TNF-α and amoebae. In the present study, the TC genotype was significantly associated with reduced prevalence of Entamoeba species (p = 0.015). Indicating that the TC genotype may be protective against Entamoeba infections. Some in vitro studies have revealed that TNF-α leads to increased nitric oxide (NO) production and killing of amoeba (Séguin et al., 1997). These findings would suggest that TNF-α may be beneficial in amoebic colitis. In this study, heterozygous TC genotype of the SNP -1031T/C was significantly higher in healthy control than children with Entamoeba species and Entamoeba coli. This indicates that -1031T/C genotype may offer a protective effect against Entamoeba species and Entamoeba coli. TNF-α has been shown to worsen tissue damage in mouse models of amoebic colitis (Zhang et al., 2003 and Zhang and Stanley, 2004). The TNF-α also attracts E. histolytica trophozoites through chemotaxis (Blazquez et al., 2006), which may aid the parasite in the process of tissue invasion and colitis. Although not statistically significant, the present study showed that the CC genotype of the SNP -1031T/C was greater in children with Giardia lamblia as compared to healthy control. Zhou et al. (2007) showed that TNF-α plays an important role in the early control of giardiasis.

Our results also showed that homozygous CC genotype of the SNP -1031T/C was significantly higher among children with Cyclospora and overall parasitic infection with diarrhea and acute lower respiratory infection, indicating that CC genotype may be a factor for Cyclospora. These findings are in agreement with a previous study by Akman et al. (2006), who showed that TNF-α -1031CC genotype was also associated with a significantly higher serum TNF-α level in Behcet's disease. Another study by Sohail et al. (2008), also revealed that TNF-α -1031CC genotype was also associated with a significantly higher serum level of TNF-α in malaria patients.

Although no significant association was observed, heterozygous TC genotype of the SNP -1031 was greater among the children with Cryptosporidium infections as opposed to the control group. A previous study carried out by Nourian et al. (2017), demonstrated similar results with regards to the TC genotype which increased in patients with IBD in an Iranian population nonetheless no significant association was discerned.

In conclusion, the present study shows for the first time that -1031 (T/C) polymorphism of the TNF-α promotor gene is associated with pathogenic parasitic infections, particularly Entamoeba spp and Cyclospora infections. In particular, the heterozygote genotypes were associated with protection against Entamoeba infections while the homozygote genotypes seemed to be more common among participants with more infections. However, this polymorphism of TNF-α promotor gene was not associated with Cryptosporidium species, Giardia lamblia and Balantidium coli, suggesting that polymorphism might not have an impact on the occurrence of these infections among children.

Declarations

Author contribution statement

Davhana NC: Performed the experiments; Analyzed and interpreted the data; Wrote the paper.

ElBakri AK: Analyzed and interpreted the data.

Bessong PO, Samie A: Conceived and designed the experiments; Performed the experiments; Analyzed and interpreted the data.

Funding statement

This work was supported by a grant made available to Prof. Samie, A through the National Research Foundation of South Africa (Grant number IFR180215313776). The study was also funded by University of Virginia with support from MAL-ED Network Investigators from the Foundation of National Institute of Health, Fogarty International Center (FIC) with overall support from the Bill & Melinda Gates Foundation.

Competing interest statement

The authors declare no conflict of interest.

Additional information

No additional information is available for this paper.

Acknowledgements

The authors would like to thank the hospital management and the patients for their cooperation throughout the study.

References

  1. Ahmed A.S., Flórez M.G., Karanis P. The impact of water crises and climate changes on the transmission of protozoan parasites in Africa. Pathog. Glob. Health. 2018;112(6):281–293. doi: 10.1080/20477724.2018.1523778. Published online 2018 Oct 17. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Akman A., Sallakci N., Coskun M., Bacanli A., Yavuzer U., Alpsoy E., Yegin O. TNF-alpha gene 1031 T/C polymorphism in Turkish patients with Behçet’s disease. Br. J. Dermatol. 2006;155(2):350–356. doi: 10.1111/j.1365-2133.2006.07348.x. [DOI] [PubMed] [Google Scholar]
  3. Bessong P.O., Nyathi E., Mahopo T.C., Netshandama V., MAL-ED South Africa Development of the Dzimauli community in Vhembe district, Limpopo province of South Africa, for the MAL-ED cohort study. Clin. Infect. Dis. 2014;59(Suppl 4):S317–S324. doi: 10.1093/cid/ciu418. [DOI] [PubMed] [Google Scholar]
  4. Blazquez S., Zimmer C., Guigon G., Olivo-Marin J.C., Guillén N., Labruyère E. Human tumor necrosis factor is a chemoattractant for the parasite Entamoeba histolytica. Infect. Immun. 2006;74:1407–1411. doi: 10.1128/IAI.74.2.1407-1411.2006. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Burns J.W., Siadat-Pajouh M., Krishnaney A.A., Greenberg H.B. Protective effect of rotavirus VP6-specific IgA monoclonal antibodies that lack neutralizing activity. Science. 1996;272:104–107. doi: 10.1126/science.272.5258.104. [DOI] [PubMed] [Google Scholar]
  6. Derouich-Guergour D., Brenier-Pinchart M.P., Ambroise-Thomas P., Pelloux H. Tumor necrosis factor-α receptors: role in the physiopathology of protozoan parasite infections. Int. J. Parasitol. 2001;31:763–769. doi: 10.1016/s0020-7519(01)00194-1. [DOI] [PubMed] [Google Scholar]
  7. Durmaz B., Yakinci C., Koroğlu M., Rafiq M., Durmaz R. Concentration of total serum IgE in parasitized children and the effects of the antiparasitic therapy on IgE levels. J. Trop. Pediatr. 1998;44:121. doi: 10.1093/tropej/44.2.121. [DOI] [PubMed] [Google Scholar]
  8. Ekhlas H.A., Usama S.B., Manal Z.M., Koji N., Kazumi N. Breast-feeding protects infantile diarrhea caused by intestinal Protozoan infections. Kor. J. Parasitol. 2013;51:519–524. doi: 10.3347/kjp.2013.51.5.519. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Enriquez F.J., Michael W.R. Role of immunoglobulin A monoclonal antibodies against P23 in controlling murine Cryptosporidium parvum infection. Infect. Immun. 1998;66:4469–4473. doi: 10.1128/iai.66.9.4469-4473.1998. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Fischer Walker C.L., Perin J., Aryee M.J., Boschi-Pinto C., Black R.E. Diarrhea incidence in low- and middle-income countries in 1990 and 2010: a systematic review. BMC Publ. Health. 2012;12:220. doi: 10.1186/1471-2458-12-220. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Houpt E., Gratz J., Kosek M., Zaidi A.M.K., Qureshi S., Kang G., Babji S., Mason C., Bodhidatta L., Samie A., Bessong P., Barrett L., Lima A., Havt A., Haque R., Mondal D., Taniuchi M., Stroup S., McGrath M., Lang D., The MAL-ED Network Investigators Microbiologic methods utilized in the MAL-ED cohort study. Clin. Infect. Dis. 2014;59(Suppl 4):S225–S232. doi: 10.1093/cid/ciu413. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Kabayiza J.Z., Andersson M.E., Nilsson S., Bergstrom T., Muhirwa G., Lindh M. Real time PCR identification of agents causing diarrhea in Rwandan children less than 5 years of age. Pediatr. Infect. Dis. J. 2014;33:1037–1042. doi: 10.1097/INF.0000000000000448. [DOI] [PubMed] [Google Scholar]
  13. Lean S., Lacroix-Lamandé S., Laurent F., McDonald V. Role of tumor necrosis factor alpha in development of immunity against Cryptosporidium parvum infection. Infect. Immun. 2006;74(7):4379–4382. doi: 10.1128/IAI.00195-06. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Lee M.K., Park A.J., Kim D.H. Tumor necrosis factor-alpha and interleukin-6 promoter gene polymorphisms are not associated with an increase risk of endometriosis. Fertil. Steril. 2002;77:1304–1305. doi: 10.1016/s0015-0282(02)03132-1. [DOI] [PubMed] [Google Scholar]
  15. MAL-ED Network Investigators The MAL-ED study: a multinational and multidisciplinary approach to understand the relationship between enteric pathogens, malnutrition, gut physiology, physical growth, cognitive development, and immune responses in infants and children up to 2 years of age in resource-poor environments. Clin. Infect. Dis. 2014;59(Suppl 4):S193–206. doi: 10.1093/cid/ciu653. [DOI] [PubMed] [Google Scholar]
  16. Naderi N., Farnood A., Dadaei T., Habibi M., Balaii H., Firouzi F., Mahban A., Soltani M., Zali M. Association of tumor necrosis factor Alpha gene polymorphisms with inflammatory bowel disease in Iran. Iran. J. Public Health. 2014;43:630–636. [PMC free article] [PubMed] [Google Scholar]
  17. Nasser A.M. Removal of cryptosporidium by wastewater treatment processes: a review. J. Water Health. 2016;14:1–3. doi: 10.2166/wh.2015.131. [DOI] [PubMed] [Google Scholar]
  18. Naz A., Nawaz Z., Rasool N.H., Zahoor M.A. Cross-sectional epidemiological investigations of Giardia lamblia in children in Pakistan. Sao Paulo Med. J. 2018;136:449–453. doi: 10.1590/1516-3180.2018.0350060918. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Nourian M., Chaleshi V., Pishkar L., Azimzadeh P., Baradaran Ghavami S., Balaii H., Alinaghi S., Shahrokh S., Asadzadeh Aghdaei H., Zali M.R. Evaluation of tumor necrosis factor (TNF)-α mRNA expression level and the rs1799964 polymorphism of the TNF-α gene in peripheral mononuclear cells of patients with inflammatory bowel diseases. Biomed. Rep. 2017;6(6):698–702. doi: 10.3892/br.2017.908. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Ollier W.E. Cytokine genes and disease susceptibility. Cytokine. 2004;28:174–178. doi: 10.1016/j.cyto.2004.07.014. [DOI] [PubMed] [Google Scholar]
  21. Platts-Mills J.A., McCormick B.J., Kosek M., Pan W.K., Checkley W., Houpt E.R., MAL-ED Network Investigators Methods of analysis of enteropathogen infection in the MAL-ED Cohort Study. Clin. Infect. Dis. 2014;59(Suppl 4):S233–S238. doi: 10.1093/cid/ciu408. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Pullan R.L., Smith J.L., Jasrasaria R., Brooker S.J. Global numbers of infection and disease burden of soil transmitted helminth infections in 2010. Parasite Vector. 2014;7:37. doi: 10.1186/1756-3305-7-37. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Richard S.A., Barrett L.J., Guerrant R.L., Checkley W., Miller M.A., MAL-ED Network Investigators Disease surveillance methods used in the 8-site MAL-ED cohort study. Clin. Infect. Dis. 2014;59(Suppl 4):S220–S224. doi: 10.1093/cid/ciu435. [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. Séguin R., Mann B.J., Keller K., Chadee K. The tumor necrosis factor alpha-stimulating region of galactose-inhibitable lectin of Entamoeba histolytica activates gamma interferon-primed macrophages for amebicidal activity mediated by nitric oxide. Infect. Immun. 1997;65:2522–2527. doi: 10.1128/iai.65.7.2522-2527.1997. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Sherchan J., Sherpa K., Tandukar S. Infection of Cyclospora cayetanesis in diarrheal children of Nepal. J. Nepal Pediatr. Soc. 2010;30:23–30. [Google Scholar]
  26. Sohail M, Kaul A, Bali P, Raziuddin M, Singh MP, Singh OP, Dash AP, Adak T. Alleles −308A and −1031C in the TNF- gene promoter do not increase the risk but associated with circulating levels of TNF- and clinical features of vivax malaria in Indian patients. Mol. Immunol. 2008;45:1682–1692. doi: 10.1016/j.molimm.2007.10.002. [DOI] [PubMed] [Google Scholar]
  27. Teles N.S., Fechine F.V., Viana F.A., Viana I.O., Nascimento D.F., Leite A.L., Bezerra F.A., Moraes M.O., Moraes M.E. Evaluation of the therapeutic efficacy of Mentha crispa in the treatment of giardiasis. Contemp. Clin. Trials. 2011;32:809–813. doi: 10.1016/j.cct.2011.08.005. [DOI] [PubMed] [Google Scholar]
  28. ul Wadood A., Bari A., ur Rhman A., Qasim K.F. Frequency of intestinal parasite infestation in children hospital quetta. Pak. J. Med. Res. 2005;44:87–88. [Google Scholar]
  29. Xiao L. Molecular epidemiology of cryptosporidiosis: an update. Exp. Parasitol. 2010;124:80–89. doi: 10.1016/j.exppara.2009.03.018. [DOI] [PubMed] [Google Scholar]
  30. Yaoyu F., Xiao L. Zoonotic potential and molecular epidemiology of Giardia species and giardiasis. Clin. Microbiol. Rev. 2011;24:110–140. doi: 10.1128/CMR.00033-10. [DOI] [PMC free article] [PubMed] [Google Scholar]
  31. Zhang Z., Mahajan S., Zhang X., Stanley S.L. Tumor necrosis factor alpha is a key mediator of gut inflammation seen in amebic colitis in human intestine in the SCID mouse-human intestinal xenograft model of disease. Infect. Immun. 2003;71:5355–5359. doi: 10.1128/IAI.71.9.5355-5359.2003. [DOI] [PMC free article] [PubMed] [Google Scholar]
  32. Zhang Z., Stanley S.L. Stereotypic and specific elements of the human colonic response to Entamoeba histolytica and Shigella flexneri. Cell Microbiol. 2004;6:535–554. doi: 10.1111/j.1462-5822.2004.00381.x. [DOI] [PubMed] [Google Scholar]
  33. Zhou P., Li E., Shea-Donohue T., Singer S.M. Tumor necrosis factor alpha contributes to protection against Giardia lamblia infection in mice. Parasite Immunol. 2007;29:367–374. doi: 10.1111/j.1365-3024.2007.00953.x. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from Heliyon are provided here courtesy of Elsevier

RESOURCES