Skip to main content
NCBI home page
NIHPA Author Manuscripts logoLink to NIHPA Author Manuscripts
. Author manuscript; available in PMC: 2013 Aug 5.
Published in final edited form as: Curr Opin Infect Dis. 2011 Aug;24(4):315–322. doi: 10.1097/QCO.0b013e328348b159

Immune responses against Aspergillus fumigatus: what have we learned?

Robert A Cramer a, Amariliz Rivera b, Tobias M Hohl c
PMCID: PMC3733365  NIHMSID: NIHMS334059  PMID: 21666456

Abstract

Purpose of review

Aspergillus fumigatus causes invasive and allergenic disease. Host defense relies on the ability of the respiratory immune system to restrict spore germination into invasive hyphae and to limit fungus-induced or inflammation-induced damage in infected tissues. This review covers the molecular and cellular events that mediate innate and CD4 T-cell responses to A. fumigatus and fungal attributes that counter hostile microenvironments and, in turn, affect host responses.

Recent findings

Host recognition of fungal cell wall components is critical for fungal uptake, killing, and the formation of protective innate and CD4 T-cell effector populations. Beyond the known role of neutrophils and macrophages, circulating monocytes, dendritic cells, and natural killer cells contribute to optimal defense against A. fumigatus. Genetic and pharmacologic manipulation of A. fumigatus reveals that hypoxia adaptation, cell wall assembly, and secondary metabolite production in mammalian tissues contribute to fungal pathogenesis and the outcome of infection.

Summary

Greater understanding of the immune mechanisms that underlie protective responses and fungal pathways that promote microbial adaptation and growth in mammalian tissue provide a conceptual framework for improving current antifungal therapies.

Keywords: Aspergillus, fungus, immune response, inflammation, pathogenesis

Introduction

Aspergillus fumigatus is an airborne fungus that causes a range of disease states in humans (summarized in Table 1) [1]. Exposure to inhaled spores (conidia) is lifelong and, for most humans, symptomless. Invasive disease occurs in hosts with defects in myeloid cell number or function and results from spore germination into tissue-invasive hyphae. Allergenic disease can develop in hosts with underlying inflammatory conditions, exemplified by asthma, atopy, and cystic fibrosis, and arises from dysregulated or exuberant immune responses to fungal antigens in colonized airways.

Table 1. Human disease associated with Aspergillus fumigatus.

Disease Pathogenesis Patient groups
Acute aspergillosis (invasive aspergillosis) Invasive, disseminates hematogenously, rapidly progressive (<1 month) Hematologic malignancies or aplasia, bone marrow and lung transplant recipients, chronic granulomatous disease, hyper-IgE syndrome
Invasive aspergillosis is associated with severely immune compromised states and myeloid cell dysfunction
Subacute aspergillosis (chronic necrotizing) Invasive, rare dissemination, progressive (1–3 months), nodular and cavitary lesions Chronic corticosteroid therapy, alcoholics, chronic obstructive pulmonary disease and underlying lung disease, cystic fibrosis
Subacute aspergillosis is associated with a lower degree of immune compromise than patients with invasive aspergillosis
Chronic aspergillosis Little to no fungal tissue invasion, slowly progressive (>3 months), cavitary and/or fibrosing lesions, fungus balls (aspergilloma) Structural and/or underlying lung disease
Allergic aspergillosis Fungal colonization, dysregulated inflammatory response to Aspergillus antigens Allergic bronchopulmonary aspergillosis (ABPA), allergic fungal sinusitis
Open in a new tab

Following A. fumigatus spore inhalation, the respiratory immune system initiates a series of events that culminates in fungal clearance in immune-competent hosts. These include fungal particle recognition, uptake by opsonic and nonopsonic receptors, killing by reactive oxygen-dependent and oxygen-independent mechanisms, and the release of mediators that coordinate effector cell recruitment, activation, and function in the innate and adaptive phases of the response (for comprehensive reviews see [1,2]). Damage to host tissue can occur with unrestrained fungal growth or from the recruitment of inflammatory cells to infected sites. Although humans represent accidental hosts for airborne A. fumigatus spores, fungal attributes that have evolved for survival in its ecologic niche (decaying organic matter) can act to counter clearance mechanisms at distinct steps listed above and promote fungal pathogenesis and persistence in hostile tissue environments [3,4].

The fungal cell wall: the center of discourse

The fungal cell wall has a significant impact on the host immune response as it represents the first structure encountered by the host cells and contains a number of polysaccharides with immune activating and modulatory properties; these include β-1,3/1,4-glucan, α-1,3-glucan, chitin, galactomannan, and a unique polymer of galactosaminogalactan [5–7]. Fungal cell wall composition varies during the process of germination and hyphal growth and is influenced by the presence of antifungal drugs and local conditions in tissue microenvironments.

Cell wall interactions important for spore uptake

The surface of inhaled spores contains a proteinaceous layer that masks the underlying immunologically active polysaccharides [8••]. At this stage, a critical opsonic interaction is the binding of the collectin pentraxin-3,released primarily from neutrophil granules, to the spore surface [9]. Pentraxin-3(−/−) mice are vulnerable to A. fumigatus infection [10], and this susceptibility has been associated with a defect in spore uptake, as neutrophils take up pentraxin-3-coated spores much more efficiently than uncoated spores. Pentraxin-3-dependent fungal cell uptake operates via a complement protein C3-dependent process that involves CD11b (CR3) and FcγR recruitment to the phagocytic cup The protective function of pentraxin-3 administration is abolished in Fc-γR(−/−) mice but not in SCID and Rag-2(−/−) mice, excluding a role for antibody in pentraxin-3-dependent and FcRγ-dependent spore uptake process [11•]. Pentraxin-3 can also act as an endogenous inhibitor of neutrophil adhesion to vascular surfaces by binding to endothelial P-selectin [12]. Whether this regulatory mechanism is beneficial during respiratory fungal infection remains unclear, but may serve to limit inflammation-induced tissue damage.

A. fumigatus can counter opsonization and complement activation through secreted proteolytic activity. The alkaline protease Alp1 degrades human complement proteins C3, C4, and C5 [13]. Although the virulence of the Δalp1 strain is similar to the wild-type strain in a pulmonary infection model [13], another study found that the complement-degrading proteolytic activity diminishes fungal uptake by brain microglial cells [14], suggesting a possible role in the pathogenesis of disseminated CNS aspergillosis.

Diverse signaling receptors recognize cell wall changes during germination

The process of spore swelling, the first step of germination, results in the obligate exposure of fungal ligands that bind cognate C-type lectin (CTL) and Toll-like receptors (TLRs) [1,2,15]. This process activates signaling pathways linked to the production of inflammatory cytokines and chemokines, prostaglandins, as well as the production of reactive oxygen. Germination is associated with an increase in fungal metabolism, which is important for the production of immunomodulatory factors such as primary and secondary metabolites and the secreted protease mentioned above. Chief among these host–fungal interactions is the binding of the CTL receptor Dectin-1 to fibrillar β-(1,3)-glucan [16–18]. Dectin-1(−/−) mice are more susceptible to high doses of A. fumigatus than control mice and produce diminished proinflammatory cytokine responses [19]. In allogeneic stem cell transplant patients, receipt of a T-cell-depleted allograft that contains a defective Dectin-1 allele (Dectin-1Y238X/+) is associated with an increased risk of developing invasive aspergillosis [20•].

TLR2, TLR4, and TLR9 are implicated in A. fumigatus recognition and signaling through the common TLR adaptor protein MyD88 [1]. MyD88(−/−) mice exhibit a higher lung fungal burden than control mice and mount dysregulated inflammatory responses [21]. In humans, the presence of a TLR4 polymorphism among donor cells increases the risk for invasive aspergillosis among hematopoietic stem cell transplant (HCT) recipients [22]. Thus, both Dectin-1-dependent and MyD88-dependent signals are crucial for host defense in mice and humans.

Germinating spores and hyphae also trigger interelukin (IL)-1β.release by a macrophage cell line [23] and in vivo[19]. Gene-silencing experiments implicate the NRLP3 inflammasome in caspase-1 activation [23]. The precise in-vivo role of the NLRP3 inflammasome and IL-1 signaling in host defense remains undefined, though downstream IL-1 receptor-dependent pathways may not be essential for survival [24].

New players on the block: traps, monocytes, and natural killer cells

Although neutrophil-mediated spore and hyphal killing is essential to defense [1], recent work indicates that other inflammatory cell populations, notably monocytes, dendritic cells, and natural killer (NK) cells, exert direct antifungal effector properties and, in the case of infection-induced dendritic cells, initiate the adaptive phase of the immune response.

Neutrophil extracellular traps

Beyond established effector mechanisms (reactive oxygen, phagosome proteolytic activity, and granule proteins such as lactoferrin), neutrophils can form extracellular traps upon encountering germinating A. fumigatus spores and hyphae in the test tube and lung [25,26]. Although their relative role in fungal killing remains unknown, Neutrophil extracellular trap formation was restored by gene therapy in a patient with chronic granulomatous disease and coincided with the resolution of preexisting pulmonary aspergillosis [27].

Role of monocytes, dendritic cells, and natural killer cells in host defense

The murine lung inflammatory cell infiltrate contains numerous Ly6Chi monocytes (also known as inflamma-tory monocytes) recruited from bone marrow stores via CC chemokine receptor 2 (CCR2)-mediated mechanisms within 24h postinfection (Fig. 1) [28•]. Human CD14+ monocytes, murine Ly6Chi monocyte counterparts, phagocytose spores and inhibit germination [29]. In infected lungs, Ly6Chi monocytes rapidly differentiate into CD11b+CD11c+MHC class IIhi monocyte-derived dendritic cells (Mo-DCs) and transport spores to lung-draining lymph nodes, a process that is essential for the priming and expansion of A. fumigatus-specific CD4 T cells [28•].

Figure 1. Model of monocyte function during pulmonaryAspergillus fumigatus infection.

Figure 1

Open in a new tab

Ly6Chi CCR2+ monocytes rapidly infiltrate Aspergillus fumigatus-infected lungs, differentiate into monocyte-derived dendritic cells (Mo-DCs), and engulf fungal spores for transport to lung-draining lymph nodes. Monocyte and their derivatives generate inflammatory cues that are essential for the development of IFN-γ-producing CD4 airway effector cells. In neutropenic mice, Mo-DCs likely form a significant pool of innate antifungal effector cells that control fungal growth, although the precise mechanisms remain to be elucidated.

The size of the lung Mo-DC population correlates with survival in neutropenic mice [30•] and is greater in neutropenic than in neutrophil-sufficient animals, even when mice are challenged with killed fungal products [31•]. In neutropenic mice, monocyte-dependent and Mo-DC-dependent tumor necrosis factor production enhances their CCR2-dependent pulmonary trafficking [31•]. Genetic deletion of the chemokine receptor CCR7 in hematopoietic cells enhances Mo-DC production from bone marrow precursors following bone marrow transplantation [32] and diminishes Mo-DC lung egress to draining lymph nodes [30•], both of which increase the number of Mo-DCs in infected lungs and correlate with enhanced survival. Depletion strategies that predominately target monocytes and Mo-DCs in immune-competent mice (using ablation of CCR2+ cells) or that include Mo-DCs in neutropenic mice (using ablation o CD11c+ cells) result in delayed fungal clearance [28•] or in diminished survival [31•].

A recent study found a role for plasmacytoid dendritic cells during respiratory fungal infection [33]. Purified plasmacytoid dendritic cells damage A. fumigatus hyphae in a partially Zn2+ -dependent mechanism that is consistent with a role for the granular protein calprotectin in fungal cell killing. Furthermore, mice defective in type I interferon production are susceptible to invasive disease. The finding that antibody-mediated plasmacytoid dendritic cell depletion recapitulates this phenotype, albeit in a milder form, is consistent with a role for plasmacytoid dendritic cell-dependent type I interferon production in host defense in vivo.

In neutropenic mice, the recruitment or adoptive transfer of NK cells to infected lungs is beneficial [34]. NK-cell-derived interferon (IFN)-γ activates macrophage-dependent fungal clearance in vitro and is essential for NK-cell-dependent host defense in neutropenic mice in vivo[35]. In-vitro studies demonstrate that human NK cells damage A. fumigatus hyphae [36]. Thus, a key translational question is to define a therapeutic role for NK cells, monocytes, and dendritic cells as effector cells in diseased patients, particularly as these cells can be harvested by leukopheresis and expanded ex vivo.

Aspergillus fumigatus-specific CD4 T cells

A. fumigatus spore exposure leads to the development of diverse CD4 T-cell responses that include T helper (Th) 1, Th2, Th17, and regulatory T (Treg) cells [37]. Protection against invasive aspergillosis in mice [38,39] and humans [40] relies in part on fungus-specific CD4 T cells. In immune compromised patients, adoptive transfer of A. fumigatus-specific CD4 T cells can provide a benefit [41,42]. Consistent with the notion that Th1 responses are beneficial, neutralizing Th2-biased cytokines in neutropenic mice improves disease outcome [38].

Various factors contribute to the molecular and cellular mechanisms that regulate A. fumigatus-specific CD4 T-cell differentiation toward Th1, Th2, and Th17 effector cells in vivo. These include exposure frequency, antigen type, engagement of CTL and TLR signaling pathways, and infection-induced dendritic cell populations in the lung. In single exposure models, the A. fumigatus-specific CD4 T-cell airway response consists of a dominant Th1 and a smaller Th17 population [43••, 44].Similarly, CD4 T-cell responses in healthy individuals are primarily Th1-biased [45], whereas A. fumigatus-specific Th2 CD4 T cells predominate in the response in allergic bronchopulmonary aspergillosis (ABPA) patients and contribute to disease progression [46••]. Repeated exposures to A. fumigatus spores in murine pulmonary infection models result in increased recruitment of Th2 and Th17 CD4 T cells [47]. In a vaccine model, distinct preparations of A. fumigatus antigens induce the selective expansion of various CD4 T-cell subsets with secreted antigens promoting the differentiation of Th2 cells, membrane components Th1 cells, and glycolipids Th17 cells [37]. Similarly, the protease activity of A. fumigatus allergens is crucial to their capacity to induce Th2 differentiation [48].

Role of Dectin-1 and Toll-like receptor signaling on the formation of fungus-specific CD4 effector cells

The induction of predominately Th1- or Th2-biased CD4 T-cell responses by live and heat-inactivated spores, respectively, indicates that innate receptor signaling activated by the process of spore germination is a critical determinant of CD4 T cell differentiation [49]. Innate TLR-MyD88 signaling is crucial for the initial induction of T-bet (Th1 transcription factor) in the lung-draining lymph node, while MyD88-independent and Dectin-1-independent mechanisms promote further T-bet expression in CD4 T cells that enter airways [43••, 44] In turn, the induction of T-bet expression in fungus-specific CD4 T cells inhibits Th17 differentiation [43••], consistent with a role of T-bet in suppressing RORγt (Th17 transcription factor) induction [50] and similar to its known role in suppressing GATA-3 (Th2 transcription factor) induction [51,52]. Thus, T-bet expression is a critical switch in the regulation of A. fumigatus-specific CD4 T-cell differentiation.

Following A. fumigatus infection, Dectin-1 signaling and the presence of Mo-DCs influence T-bet expression levels in fungus-specific CD4 T cells. Dectin-1 signals act on innate cells to diminish the production of IL-12p35 and IFN-γ, leading to a reduction in T-bet expression by fungus-specific CD4 T cells. By regulating T-bet expression levels in CD4 T cells, Dectin-1 facilitates the development of Th17 effector cells and contributes to the establishment of a more diverse CD4 T-cell response [43••].

Beyond their role in fungal antigen transport to lung-draining lymph nodes, monocyte derivatives provide essential cues that shape CD4 T-cell differentiation [43••]. Depletion of Mo-DCs at various times after infection results in enhanced Th17 and diminished Th1 differentiation. The alteration in the Th1/Th17 balance correlates with a loss of T-bet expression in fungus-specific CD4 T cells. Thus, it appears that monocyte derivatives are important for the maintenance of T-bet expression in CD4 T cells and the development of a protective Th1 response [43••].

The infection microenvironment: a crossroad between fungal and host factors

The above studies illustrate our understanding of key immune system mechanisms to prevent invasive A. fumigatus infections primarily in the immunocompetent host. Future challenges will include learning how this understanding of fungal resistance can be translated into the immunocompromised patient populations that acquire A. fumigatus infections. However, once germination occurs in an immunocompromised patient, the relationship between the tissue microenvironment and fungal cell metabolic activity during the course of infection is largely unappreciated, but potentially important for disease outcome and evolution of host immune responses. A better understanding of how the host microenvironment influences fungal virulence and immunomodulatory factors, as well as what factors induce changes in the infection microenvironment itself, should improve our ability to design more effective therapeutics to manage invasive aspergillosis. With this in mind, we review recent advances in our understanding of the fungal response to the infection microenvironment encountered by A. fumigatus during colonization and invasive growth in immunocompromised hosts.

Fungal secondary metabolism

A unique aspect of A. fumigatus metabolism is the production of bioactive secondary metabolites, which are typically dispensable for completion of the fungal life cycle [53]. The most studied A. fumigatus secondary metabolite is the epipolythiodioxopiperazine gliotoxin [54–57] that is produced in murine models of invasive aspergillosis [58,59]. The role of gliotoxin in invasive pulmonary aspergillosis (IPA) seems to be host microenvironment dependent, with the key factor being the method of immunosuppression. In murine models of IPA that utilize cyclophosphamide for neutrophil depletion, gliotoxin production was found to be dispensable for disease development [59–62]. However, in murine models that utilize corticosteroids for immunosuppression, gliotoxin was found to be a critical factor for disease development [62,63]. Although the exact mechanism for gliotoxin's differential role in Aspergillus virulence is unknown, its ability to induce apoptosis in neutrophils is thought to be a primary mode of action [62–64]. The massive myeloid cell depletion that occurs when cyclophosphamide is used as the immunosuppressant may mitigate any effects of gliotoxin on these target cells that are largely absent from the infection site.

In addition to gliotoxin's direct effect on neutrophils, recent data suggest an in-vivo link between secondary metabolite production and inhibition of host angiogenesis, as the A. fumigatus laeA null mutant that is deficient in secondary metabolite production does not inhibit angiogenesis to the same degree as the wild-type strain [65••]. Both gliotoxin and fumagillin are candidate secondary metabolites that may mediate the LaeA-dependent effect on host angiogenesis. Intriguingly, inhibition of host angiogenesis likely results in significant localized tissue hypoxia [66]. Deficiency of the LaeA transcriptional regulator also impacts the composition of the fungal cell wall, resulting in a diminished hydrophobic layer and enhanced phagocytosis of ΔlaeA spores by neutrophils [67].

Hypoxia adaptation

As mentioned, oxygen availability is an important feature of the infection microenvironment that is not well understood. Oxygen is a critical molecule for both host and pathogen cell metabolism and its absence places a significant stress on most eukaryotic cells. Recent studies confirm that in three immunologically distinct murine models of IPA (neutropenic, corticosteroid, and chronic granulomatous disease), hypoxia (O2 ≤1.5%) occurs at sites of A. fumigatus invasive growth in the lung [68]. Importantly, the ability to overcome hypoxia appears to be a requirement for lethal disease, as SrbA, a fungal transcription factor in the sterol regulatory element-binding protein family, is required for A. fumigatus growth under hypoxia and for lethal invasive disease in multiple murine models of IPA [69]. Ongoing studies are exploring the mechanisms of SrbA-dependent hypoxia growth and its relation to invasive disease.

The presence of hypoxia at the site of infection is also likely to have a significant effect on the expression and composition of the fungal cell wall. In the yeast Saccharomyces cerevisiae, low-oxygen environments stimulate cell-wall remodeling that results in increased exposure or production of the DAN/TIR mannoproteins [70–72]. Although whole-genome gene expression studies reveal significant transcriptional changes in A. fumigatus cell-wall biosynthesis genes in response to hypoxia (B. Barker, R.A. Cramer, unpublished observation), the functional significance and exact nature of these changes remains to be elucidated, specifically in the context of clinically relevant immunosuppression regimens.

Immunopharmacologic effects

The presence of antifungal drugs used to treat A. fumigatus infections may also alter the infection microenvironment by affecting fungal metabolism and subsequent host responses. Echinocandin drugs, β-(1,3) glucan synthase inhibitors, alter the surface content of β-glucan on A. fumigatus hyphae resulting in enhanced macrophage and neutrophil inflammatory responses via a Dectin-1-dependent mechanism [73,74]. In a systemic candidiasis model, echinocandin-dependent β-(1,3)-glucan exposure occurs in infected tissues [75]. Thus, echinocandin drugs may act in part via an immunopharmacologic mechanism to benefit the host, as they fail to inhibit A. fumigatus growth completely at any concentration. The effects of amphotericin B on the immune system are also an active area of investigation [76].

Conclusion

The past several years have witnessed significant advances in our understanding of host defense mechanisms against A. fumigatus and of fungal attributes that facilitate growth in hostile tissue microenvironments. Several of these findings have important clinical implications for patient care. First, dissection of host pathways involved in fungal recognition and killing has led to advances in the field of immunogenetics and the recognition of genetic risk for invasive aspergillosis in the context of bone marrow transplantation [77]. An important area of research is to incorporate these findings into patient care, for example, in prophylaxis strategies and allograft selection when multiple donors are available. Second, the recognition that monocytes, dendritic cells, and NK cells can act in host defense in neutropenic hosts opens new research directions for myeloid reconstitution and adoptive transfer strategies. Third, improved understanding of molecular cues that underlie CD4 T-cell differentiation has implications for modulating allergenic responses, as exemplified by the link between vitamin D levels and Th2 responses in ABPA patients [46••]. Fourth, research on the influence of the infection microenvironment on fungal metabolism may lead to new drug targets and a better understanding of which immunomodulatory techniques may be therapeutically viable. These areas of research provide fertile ground to build on improvements in clinical outcomes [78] and to reduce Aspergillus-related morbidity and mortality.

Key points.

  • Dissecting the molecular mechanisms of Aspergillus fumigatus recognition in the lung has identified critical antifungal effector pathways and established that human genetic variants confer risk for invasive disease during hematopoietic stem cell transplantation.

  • Monocytes, dendritic cells, and natural killer cells play important roles in A. fumigatus host defense and may be of particular significance in neutropenic patients.

  • The formation of specific CD4 T-cell effector populations during invasive and allergenic disease depends in part on Toll-like receptor and C-type lectin signaling pathways in innate cells recruited to the lung.

  • Understanding fungal metabolic pathways that are activated in hostile tissue microenvironments and in response to antifungal therapy point to novel microbial targets for drug development and a better understanding of the role of immunomodulatory therapies in these settings.

Acknowledgments

T.M.H. acknowledges the Robert M. Sinskey Foundation, the American Heart Association, and NIH grant K08 AI071998 for support. R.A.C. acknowledges grants from NIH/NIAID R01AI81838, NIH/NCRR COBRE 2P20RR020185, NIH/NCRR INBRE 2P20RR16455, and the Montana State University Agricultural Experiment Station. The authors regret that valuable contributions from many authors in the field could not be included due to space limitations.

References and recommended reading

Papers of particular interest, published within the annual period of review, have been highlighted as:

• of special interest

•• of outstanding interest

Additional references related to this topic can also be found in the Current World Literature section in this issue (pp. 397-398).

  • 1.Segal BH. Aspergillosis N Engl J Med. 2009;360:1870–1884. doi: 10.1056/NEJMra0808853. [DOI] [PubMed] [Google Scholar]
  • 2.Brown GD. Innate antifungal immunity: the key role of phagocytes. Annu Rev Immunol. 2011;29:1–21. doi: 10.1146/annurev-immunol-030409-101229. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 3.Hohl TM, Feldmesser M. Aspergillus fumigatus: principles of pathogenesis and host defense. Eukaryot Cell. 2007;6:1953–1963. doi: 10.1128/EC.00274-07. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 4.Askew DS. Aspergillus fumigatus: virulence genes in a street-smart mold. Curr Opin Microbiol. 2008;11:331–337. doi: 10.1016/j.mib.2008.05.009. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 5.Chai LY, Vonk AG, Kullberg BJ, et al. Aspergillus fumigatus cell wall components differentially modulate host TLR2 and TLR4 responses. Microbes Infect. 2011;13:151–159. doi: 10.1016/j.micinf.2010.10.005. [DOI] [PubMed] [Google Scholar]
  • 6.Loussert C, Schmitt C, Prevost MC, et al. In vivo biofilm composition of Aspergillus fumigatus. Cell Microbiol. 2010;12:405–410. doi: 10.1111/j.1462-5822.2009.01409.x. [DOI] [PubMed] [Google Scholar]
  • 7.Latge JP. Tasting the fungal cell wall. Cell Microbiol. 2010;12:863–872. doi: 10.1111/j.1462-5822.2010.01474.x. [DOI] [PubMed] [Google Scholar]
  • 8••.Aimanianda V, Bayry J, Bozza S, et al. Surface hydrophobin prevents immune recognition of airborne fungal spores. Nature. 2009;460:1117–1121. doi: 10.1038/nature08264. The authors demonstrate that genetic or chemical removalof the hydrophobin layeron resting spores exposes fungal β-(1,3)-glucan that can trigger dendritic cell activation and the formation of protective immunity in a vaccine model. This finding indicates that the hydrophobin layer acts to sequester immune-activating polysaccharides which may benefit A. fumigatus in its natural ecologic niche. Anotherimplication is that mammalian hosts lack receptors that bind hydrophobins and are directly tied to inducing inflammation. These findings support a model in which restricted recognition of germinating spores focuses full innate immune activation on spores most likely to cause tissue-invasive disease [16–18] [DOI] [PubMed] [Google Scholar]
  • 9.Jaillon S, Peri G, Delneste Y, et al. The humoral pattern recognition receptor PTX3 is stored in neutrophil granules and localizes in extracellulartraps. J Exp Med. 2007;204:793–804. doi: 10.1084/jem.20061301. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 10.Garlanda C, Hirsch E, Bozza S, et al. Nonredundant role of the long pentraxin PTX3 in antifungal innate immune response. Nature. 2002;420:182–186. doi: 10.1038/nature01195. [DOI] [PubMed] [Google Scholar]
  • 11•.Moalli F, Doni A, Deban L, et al. Role of complement and Fc{gamma} receptors in the protective activity of the long pentraxin PTX3 against Aspergillus fumigatus. Blood. 2010;116:5170–5180. doi: 10.1182/blood-2009-12-258376. The study integrates the interactions between pentraxin-3, complement proteins, and binding receptors into a model for fungal particle uptake. [DOI] [PubMed] [Google Scholar]
  • 12.Deban L, Russo RC, Sironi M, et al. Regulation of leukocyte recruitment by the long pentraxin PTX3. Nat Immunol. 2010;11:328–334. doi: 10.1038/ni.1854. [DOI] [PubMed] [Google Scholar]
  • 13.Behnsen J, Lessing F, Schindler S, et al. Secreted Aspergillus fumigatus protease Alp1 degrades human complement proteins C3, C4, and C5. Infect Immun. 2010;78:3585–3594. doi: 10.1128/IAI.01353-09. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 14.Rambach G, Dum D, Mohsenipour I, et al. Secretion of a fungal protease represents a complement evasion mechanism in cerebral aspergillosis. Mol Immunol. 2010;47:1438–1449. doi: 10.1016/j.molimm.2010.02.010. [DOI] [PubMed] [Google Scholar]
  • 15.Barrett NA, Maekawa A, Rahman OM, et al. Dectin-2 recognition of house dust mite triggers cysteinyl leukotriene generation by dendritic cells. J Immunol. 2009;182:1119–1128. doi: 10.4049/jimmunol.182.2.1119. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 16.Hohl TM, Van Epps HL, Rivera A, et al. Aspergillus fumigatus triggers inflammatory responses by stage-specific beta-glucan display. PLoS Pathog. 2005;1:e30. doi: 10.1371/journal.ppat.0010030. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 17.Steele C, Rapaka RR, Metz A, et al. The beta-glucan receptor dectin-1 recognizes specific morphologies of Aspergillus fumigatus. PLoS Pathog. 2005;1:e42. doi: 10.1371/journal.ppat.0010042. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 18.Gersuk GM, Underhill DM, Zhu L, Marr KA. Dectin-1 and TLRs permit macrophages to distinguish between different Aspergillus fumigatus cellular states. J Immunol. 2006;176:371, 7–3724. doi: 10.4049/jimmunol.176.6.3717. [DOI] [PubMed] [Google Scholar]
  • 19.Werner JL, Metz AE, Horn D, et al. Requisite role for the dectin-1 beta-glucan receptor in pulmonary defense against Aspergillus fumigatus. J Immunol. 2009;182:4938–4946. doi: 10.4049/jimmunol.0804250. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 20•.Cunha C, Di Ianni M, Bozza S, et al. Dectin-1 Y238Xpolymorphism associates with susceptibility to invasive aspergillosis in hematopoietic transplantation through impairment of both recipient- and donor-dependent mechanisms of antifungal immunity. Blood. 2010;116:5394–5402. doi: 10.1182/blood-2010-04-279307. This study together with [22] demonstrates the link between genetic variants in TLR and CTL signaling and susceptibility to invasive aspergillosis in the bone marrow transplant setting. A challenge for future clinical translation research is to integrate genetic risk into prevention strategies. [DOI] [PubMed] [Google Scholar]
  • 21.Bretz C, Gersuk G, Knoblaugh S, et al. MyD88 signaling contributes to early pulmonary responses to Aspergillus fumigatus. Infect Immun. 2008;76:952–958. doi: 10.1128/IAI.00927-07. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 22.Bochud PY, Chien JW, Marr KA, et al. Toll-like receptor 4 polymorphisms and aspergillosis in stem-cell transplantation. N Engl J Med. 2008;359:1766–1777. doi: 10.1056/NEJMoa0802629. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 23.Said-Sadier N, Padilla E, Langsley G, Ojcius DM. Aspergillus fumigatus stimulates the NLRP3 inflammasome through a pathway requiring ROS production and the Syk tyrosine kinase. PLoS One. 2010;5:e10008. doi: 10.1371/journal.pone.0010008. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 24.Bellocchio S, Montagnoli C, Bozza S, et al. The contribution of the Toll-like/IL-1 receptor superfamily to innate and adaptive immunity to fungal pathogens in vivo. J Immunol. 2004;172:3059–3069. doi: 10.4049/jimmunol.172.5.3059. [DOI] [PubMed] [Google Scholar]
  • 25.Bruns S, Kniemeyer O, Hasenberg M, et al. Production of extracellular traps against Aspergillus fumigatus in vitro and in infected lung tissue is dependent on invading neutrophils and influenced by hydrophobin RodA. PLoS Pathog. 2010;6:e1000873. doi: 10.1371/journal.ppat.1000873. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 26.McCormick A, Heesemann L, Wagener J, et al. NETs formed by human neutrophils inhibit growth of the pathogenic mold Aspergillus fumigatus. Microbes Infect. 2010;12:928–936. doi: 10.1016/j.micinf.2010.06.009. [DOI] [PubMed] [Google Scholar]
  • 27.Bianchi M, Hakkim A, Brinkmann V, et al. Restoration of NET formation by gene therapy in CGD controls aspergillosis. Blood. 2009;114:2619–2622. doi: 10.1182/blood-2009-05-221606. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 28•.Hohl TM, Rivera A, Lipuma L, et al. Inflammatory monocytes facilitate adaptive CD4 T cell responses during respiratory fungal infection. Cell Host Microbe. 2009;6:470–481. doi: 10.1016/j.chom.2009.10.007. This study and [30•,31•] provide mechanistic insight into the role of monocytes and infection-induced Mo-DC derivatives in host defense against A. fumigatus in the immune competent and neutrophil-depleted host. Monocytes and their derivatives facilitate the induction of fungus-specific CD4 T-cell responses in the lung and are protective independent of neutrophil function. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 29.Serbina NV, Cherny M, Shi C, et al. Distinct responses of human monocyte subsets to Aspergillus fumigatus conidia. J Immunol. 2009;183:2678–2687. doi: 10.4049/jimmunol.0803398. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 30•.Hartigan AJ, Westwick J, Jarai G, Hogaboam CM. CCR7 deficiency on dendritic cells enhances fungal clearance in a murine model of pulmonaryinvasive aspergillosis. J Immunol. 2009;183:5171–5179. doi: 10.4049/jimmunol.0901027. See [28•] [DOI] [PubMed] [Google Scholar]
  • 31•.ParkSJ SJ, Burdick MD, Brix WK, et al. Neutropenia enhances lung dendritic cell recruitment in response to Aspergillus via a cytokine-to-chemokine amplification loop. J Immunol. 2010;185:6190–6197. doi: 10.4049/jimmunol.1002064. See [28•] [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 32.Hartigan AJ, Kallal LE, Hogaboam CM. CCR7 impairs hematopoiesis after hematopoietic stem cell transplantation increasing susceptibility to invasive aspergillosis. Blood. 2010;116:5383–5393. doi: 10.1182/blood-2010-01-265454. [DOI] [PubMed] [Google Scholar]
  • 33.Ramirez-Ortiz ZG, Lee CK, Wang JP, et al. A non-redundant role for plasmacytoid dendritic cells in host defense against the human fungal pathogen Aspergillus fumigatus. Cell Host Microbe. 2011;9:415–424. doi: 10.1016/j.chom.2011.04.007. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 34.Morrison BE, Park SJ, Mooney JM, Mehrad B. Chemokine-mediated recruitment of NK cells is a critical host defense mechanism in invasive aspergillosis. J Clin Invest. 2003;112:1862–1870. doi: 10.1172/JCI18125. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 35.Park SJ, Hughes MA, Burdick M, et al. Early NK cell-derived IFN-{gamma} is essential to host defense in neutropenic invasive aspergillosis. J Immunol. 2009;182:4306–4312. doi: 10.4049/jimmunol.0803462. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 36.Schmidt S, Tramsen L, Hanisch M, et al. Human natural killer cells exhibit direct activity against Aspergillus fumigatus hyphae, but not against resting conidia. J Infect Dis. 2011;203:430–435. doi: 10.1093/infdis/jiq062. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 37.Bozza S, Clavaud C, Giovannini G, et al. Immune sensing of Aspergillus fumigatus proteins, glycolipids, and polysaccharides and the impact on Th immunity and vaccination. J Immunol. 2009;183:2407–2414. doi: 10.4049/jimmunol.0900961. [DOI] [PubMed] [Google Scholar]
  • 38.Cenci E, Perito S, Enssle KH, et al. Th1 and Th2 cytokines in mice with invasive aspergillosis. Infect Immun. 1997;65:564–570. doi: 10.1128/iai.65.2.564-570.1997. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 39.Cenci E, Mencacci A, Bacci A, et al. T cell vaccination in mice with invasive pulmonary aspergillosis. J Immunol. 2000;165:381–388. doi: 10.4049/jimmunol.165.1.381. [DOI] [PubMed] [Google Scholar]
  • 40.Hebart H, Bollinger C, Fisch P, et al. Analysis of T-cell responses to Aspergillus fumigatus antigens in healthy individuals and patients with hematologic malignancies. Blood. 2002;100:4521–4528. doi: 10.1182/blood-2002-01-0265. [DOI] [PubMed] [Google Scholar]
  • 41.Perruccio K, Tosti A, Burchielli E, et al. Transferring functional immune responses to pathogens after haploidentical hematopoietic transplantation. Blood. 2005;106:4397–4406. doi: 10.1182/blood-2005-05-1775. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 42.Beck O, Topp MS, Koehl U, et al. Generation of highly purified and functionally active human TH1 cells against Aspergillus fumigatus. Blood. 2006;107:2562–2569. doi: 10.1182/blood-2005-04-1660. [DOI] [PubMed] [Google Scholar]
  • 43••.Rivera A, Hohl TM, Collins N, et al. Dectin-1 diversifies Aspergillus fumigatus- specific T cell responses by inhibiting T helper type 1 CD4 T cell differentiation. J Exp Med. 2011;208:369–381. doi: 10.1084/jem.20100906. The study outlines the molecular and cellularmechanismsthatunderlieTh1 andTh17 CD4 lineage differentiation during respiratory fungal infection. The finding that TLR-MyD88 (↑) and Dectin-1 signals (↓) control T-bet expression, thereby reciprocally boosting or dampening Th1 and Th1 7 lineage formation, suggests possibilities for therapeutic intervention in human disease states, as exemplified by [46••] [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 44.Rivera A, Ro G, Van Epps HL, et al. Innate immune activation and CD4+ Tcell priming during respiratory fungal infection. Immunity. 2006;25:665–675. doi: 10.1016/j.immuni.2006.08.016. [DOI] [PubMed] [Google Scholar]
  • 45.Chaudhary N, Staab JF, Marr KA. Healthy human T-cell responses to Aspergillus fumigatus antigens. PLoS One. 2010;5:e9036. doi: 10.1371/journal.pone.0009036. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 46••.Kreindler JL, Steele C, Nguyen N, et al. Vitamin D3 attenuates Th2 responses to Aspergillus fumigatus mounted by CD4+T cells from cystic fibrosis patients with allergic bronchopulmonary aspergillosis. J Clin Invest. 2010;120:3242–3254. doi: 10.1172/JCI42388. The authors find that OX40 ligand (OX40L) is critical for driving CD4 Th2 responses among lymphocytes isolated from cystic fibrosis patients with ABPA. The administration of 1,25 OH-vitamin D3 reduces OX40L expression on dendritic cells in vitro and favors the development TGF-β-producing regulatory CD4 T cells. These preclinical data support the notion that vitamin D deficiency, common in cystic fibrosis patients, may predispose to ABPA, and suggest that vitamin D administration may show clinical benefit in this patient population. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 47.Murdock BJ, Shreiner AB, McDonald RA, et al. Coevolution of TH1,TH2, and TH17 responses during repeated pulmonary exposure to Aspergillus fumigatus conidia. Infect Immun. 2011;79:125–135. doi: 10.1128/IAI.00508-10. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 48.Kheradmand F, Kiss A, Xu J, et al. A protease-activated pathway underlying Th cell type 2 activation and allergic lung disease. J Immunol. 2002;169:5904–5911. doi: 10.4049/jimmunol.169.10.5904. [DOI] [PubMed] [Google Scholar]
  • 49.Rivera A, Van Epps HL, Hohl TM, et al. Distinct CD4+-T-cell responses to live and heat-inactivated Aspergillus fumigatus conidia. Infect Immun. 2005;73:7170–7179. doi: 10.1128/IAI.73.11.7170-7179.2005. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 50.Lazarevic V, Chen X, Shim JH, et al. T-bet represses T(H)17 differentiation by preventing Runx1-mediated activation of the gene encoding RORgammat. Nat Immunol. 2011;12:96–104. doi: 10.1038/ni.1969. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 51.Hwang ES, Szabo SJ, Schwartzberg PL, Glimcher LH. T helper cell fate specified by kinase-mediated interaction of T-bet with GATA-3. Science. 2005;307:430–433. doi: 10.1126/science.1103336. [DOI] [PubMed] [Google Scholar]
  • 52.Usui T, Preiss JC, Kanno Y, et al. T-bet regulates Th1 responses through essential effects on GATA-3 function rather than on IFNG gene acetylation and transcription. J Exp Med. 2006;203:755–766. doi: 10.1084/jem.20052165. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 53.Yu JH, Keller N. Regulation of secondary metabolism in filamentous fungi. Annu Rev Phytopathol. 2005;43:437–458. doi: 10.1146/annurev.phyto.43.040204.140214. [DOI] [PubMed] [Google Scholar]
  • 54.Murayama T, Amitani R, Ikegami Y, et al. Suppressive effects of Aspergillus fumigatus culture filtrates on human alveolar macrophages and polymorphonuclear leucocytes. Eur Respir J. 1996;9:293–300. doi: 10.1183/09031936.96.09020293. [DOI] [PubMed] [Google Scholar]
  • 55.Pahl HL, Krauss B, Schulze-Osthoff K, et al. The immunosuppressive fungal metabolite gliotoxin specifically inhibits transcription factor NF-kappaB. J Exp Med. 1996;183:1829–1840. doi: 10.1084/jem.183.4.1829. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 56.Sutton P, Waring P, Mullbacher A. Exacerbation of invasive aspergillosis by the immunosuppressive fungal metabolite, gliotoxin. Immunol Cell Biol. 1996;74:318–322. doi: 10.1038/icb.1996.57. [DOI] [PubMed] [Google Scholar]
  • 57.Kwon-Chung KJ, Sugui JA. What do we know about the role of gliotoxin in the pathobiology of Aspergillus fumigatus? Med Mycol. 2009;47(Suppl 1):S97–S103. doi: 10.1080/13693780802056012. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 58.Bok JW, Balajee SA, Marr KA, et al. LaeA, a regulator of morphogenetic fungal virulence factors. Eukaryot Cell. 2005;4:1574–1582. doi: 10.1128/EC.4.9.1574-1582.2005. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 59.Bok JW, Chung D, Balajee SA, et al. GliZ, a transcriptional regulator of gliotoxin biosynthesis, contributes to Aspergillus fumigatus virulence. Infect Immun. 2006;74:6761–6768. doi: 10.1128/IAI.00780-06. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 60.Cramer RA, Jr, Gamcsik MP, Brooking RM, et al. Disruption of a nonribosomal peptide synthetase in Aspergillus fumigatus eliminates gliotoxin production. Eukaryot Cell. 2006;5:972–980. doi: 10.1128/EC.00049-06. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 61.Kupfahl C, Heinekamp T, Geginat G, et al. Deletion of the gliP gene of Aspergillus fumigatus results in loss of gliotoxin production but has no effect on virulence of the fungus in a low-dose mouse infection model. Mol Microbiol. 2006;62:292–302. doi: 10.1111/j.1365-2958.2006.05373.x. [DOI] [PubMed] [Google Scholar]
  • 62.Spikes S, Xu R, Nguyen CK, et al. Gliotoxin production in Aspergillus fumigatus contributes to host-specific differences in virulence. J Infect Dis. 2008;197:479–486. doi: 10.1086/525044. [DOI] [PubMed] [Google Scholar]
  • 63.Sugui JA, Pardo J, Chang YC, et al. Gliotoxin is a virulence factor of Aspergillus fumigatus: gliP deletion attenuates virulence in mice immunosuppressed with hydrocortisone. Eukaryot Cell. 2007;6:1562–1569. doi: 10.1128/EC.00141-07. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 64.Tsunawaki S, Yoshida LS, Nishida S, et al. Fungal metabolite gliotoxin inhibits assembly of the human respiratory burst NADPH oxidase. Infect Immun. 2004;72:3373–3382. doi: 10.1128/IAI.72.6.3373-3382.2004. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 65••.Ben-Ami R, Lewis RE, Leventakos K, Kontoyiannis DP. Aspergillus fumigatus inhibits angiogenesis through the production of gliotoxin and other secondary metabolites. Blood. 2009;114:5393–5399. doi: 10.1182/blood-2009-07-231209. This study demonstrates that fungal secondary metabolites inhibit host angiogenesis and thereby shape the host microenvironment. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 66.Cramer RA, Shwab EK, Keller NP. Genetic regulation of Aspergillus secondary metabolites and their role in fungal pathogenesis. In: Latge JP, Steinbach W, editors. Aspergillus fumigatus and Aspergillosis. Washington, DC: ASM Press; 2009. pp. 185–199. [Google Scholar]
  • 67.Dagenais TR, Giles SS, Aimanianda V, et al. Aspergillus fumigatus LaeAmediated phagocytosis is associated with a decreased hydrophobin layer. Infect Immun. 2010;78:823–829. doi: 10.1128/IAI.00980-09. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 68.Grahl N, Puttikamonkul S, Macdonald JM, et al. In vivo hypoxia and a fungal alcohol dehydrogenase influence the pathogenesis of invasive pulmonary aspergillosis. PLoS Pathogens. doi: 10.1371/journal.ppat.1002145. in press. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 69.Willger SD, Puttikamonkul S, Kim KH, et al. A sterol-regulatory element binding protein is required for cell polarity, hypoxia adaptation, azole drug resistance, and virulence in Aspergillus fumigatus. PLoS Pathog. 2008;4:e1000200. doi: 10.1371/journal.ppat.1000200. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 70.Abramova N, Sertil O, Mehta S, Lowry CV. Reciprocal regulation of anaerobic and aerobic cell wall mannoprotein gene expression in Saccharomyces cerevisiae. J Bacteriol. 2001;183:2881–2887. doi: 10.1128/JB.183.9.2881-2887.2001. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 71.Abramova NE, Cohen BD, Sertil O, et al. Regulatory mechanisms controlling expression of the DAN/TIR mannoprotein genes during anaerobic remodeling of the cell wall in Saccharomyces cerevisiae. Genetics. 2001;157:1169–1177. doi: 10.1093/genetics/157.3.1169. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 72.Cohen BD, Sertil O, Abramova NE, et al. Induction and repression of DAN1 and the family of anaerobic mannoprotein genes in Saccharomyces cerevisiae occurs through a complex array of regulatory sites. Nucleic Acids Res. 2001;29:799–808. doi: 10.1093/nar/29.3.799. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 73.Hohl TM, Feldmesser M, Perlin DS, Pamer EG. Caspofungin modulates inflammatory responses to Aspergillus fumigatus through stage-specific effects on fungal beta-glucan exposure. J Infect Dis. 2008;198:176–185. doi: 10.1086/589304. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 74.Lamaris GA, Lewis RE, Chamilos G, et al. Caspofungin-mediated beta-glucan unmasking and enhancement of human polymorphonuclear neutrophil activity against Aspergillus and non-Aspergillus hyphae. J Infect Dis. 2008;198:186–192. doi: 10.1086/589305. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 75.Wheeler RT, Kombe D, Agarwala SD, Fink GR. Dynamic, morphotype-specific Candida albicans beta-glucan exposure during infection and drug treatment. PLoS Pathog. 2008;4:e1000227. doi: 10.1371/journal.ppat.1000227. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 76.Simitsopoulou M, Roilides E, Georgiadou E, et al. Differential transcriptional profiles induced by amphotericin B formulations on human monocytes during response to hyphae of Aspergillus fumigatus. Med Mycol. 2011;49:176–185. doi: 10.3109/13693786.2010.510539. [DOI] [PubMed] [Google Scholar]
  • 77.Lamoth F, Rubino I, Bochud PY. Immunogenetics of invasive aspergillosis. Med Mycol. 2011;49:S125–S136. doi: 10.3109/13693786.2010.516408. [DOI] [PubMed] [Google Scholar]
  • 78.Upton A, Kirby KA, Carpenter P, et al. Invasive aspergillosis following hematopoietic cell transplantation: outcomes and prognostic factors associated with mortality. Clin Infect Dis. 2007;44:531–540. doi: 10.1086/510592. [DOI] [PubMed] [Google Scholar]

RESOURCES