Genetic susceptibility to Aspergillus fumigatus infections

Proteome and Dihydrorhodamine Profiling of Bronchoalveolar Lavage in Patients with Chronic Pulmonary Aspergillosis

Neutrophil and (alveolar) macrophage immunity is considered crucial for eliminating Aspergillus fumigatus. Data derived from bronchoalveloar lavage (BAL) characterizing the human immuno-pulmonary response to Aspergillus fumigatus are non-existent. To obtain a comprehensive picture of the immune pathways involved in chronic pulmonary aspergillosis (CPA), we performed proteome analysis on AL of 9 CPA patients and 17 patients with interstitial lung disease (ILD). The dihydrorhodamine (DHR) test was also performed on BAL and blood neutrophils from CPA patients and compared to blood neutrophils from healthy controls (HCs). BAL from CPA patients primarily contained neutrophils, while ILD BAL was also characterized by a large fraction of lymphocytes; these differences likely reflecting the different immunological etiologies underlying the two disorders. BAL and blood neutrophils from CPA patients displayed the same oxidative burst capacity as HC blood neutrophils. Hence, immune evasion by Aspergillus involves other mechanisms than impaired neutrophil oxidative burst capacity per se. CPA BAL was enriched by proteins associated with innate immunity, as well as, more specifically, with neutrophil degranulation, Toll-like receptor 4 signaling, and neutrophil-mediated iron chelation. Our data provide the first comprehensive target organ-derived immune data on the human pulmonary immune response to Aspergillus fumigatus.

Polymorphisms in Innate and Adaptive Immune Genes in Subjects with Allergic Bronchopulmonary Aspergillosis Complicating Asthma

Innate and adaptive immunity play a crucial role in allergic bronchopulmonary aspergillosis (ABPA) pathogenesis. We performed next-generation sequencing using the Illumina TruSight One panel (4,811 human disease-associated genes, at least 20 × coverage) and selected 22 known immune genes (toll-like receptors (TLRs), C-type lectin, interleukin-4 receptor, and others). We included ABPA (n = 18), asthma without ABPA (n = 12), and healthy controls (n = 8). We analyzed 3011 SNPs from 22 genes and identified 145 SNPs (13 genes) that were present only in the disease groups and absent in controls. The SNP frequency overall was significantly higher in ABPA than in asthmatics (89/145 [61.4%] vs. 56/145 [38.6%], p = 0.0001). The SNP frequency in the TLR10 gene was also significantly higher in ABPA than in asthma (p = 0.017). Association analysis further revealed three genes having significant associations. Of these, NOS3 and HLA-DQB1 are associated with antimicrobial activity and adaptive immunity. More extensive studies are required to confirm our findings.

Difference in immune responses to Candida albicans in two inbred strains of male rats

OBJECTIVE

To investigate the influence of strain differences in immune response on the pathogenesis of oral candidiasis in Dark Agouti (DA) and Albino Oxford (AO) inbred strains of rats.

DESIGN

Seventy male 8-weeks old DA and AO rats were inoculated with Candida albicans to induce three different experimental models of oral candidiasis, one immunocompetent and two immunocompromised models. The animals were sacrificed after 16 days from the beginning of the experiment followed by collecting the samples of the tongue dorsum and blood for histopathological (PAS and H&E staining), immunohistochemical, qRT-PCR, and oxidative stress analyses.

RESULTS

Histopathological and immunohistochemical analyses revealed lower levels of epithelial colonization, epithelial damage, and inflammatory infiltration in DA compared to AO strain of rats. DA rats had fewer CD45, CD68, and CD3 positive cells but more HIS 48 positive cells than AO rats. The expressions of IL-1β, TNFα, IFN-γ, IL-10 and TGF-β1 were consistently higher in DA strain across all experimental models. However, the expressions of IL-4 and IL-17 differed inconsistently between DA and AO strain in various experimental models. Strain differences were observed in levels of prooxidative hydrogen peroxide and lipid peroxidation, with higher levels presented in AO rats compared to DA rats, while antioxidative parameters presented little yet inconsistent difference between strains.

CONCLUSION

DA strain of rats consistently presented lower susceptibility to oral infection with C. albicans compared to AO strain with robust Th1/Th17 immune response indicating the importance of the genetic background on the development of oral candidiasis.

Allergic bronchopulmonary aspergillosis

Allergic bronchopulmonary aspergillosis (ABPA) is an inflammatory disease caused by immunologic reactions initiated against Aspergillus fumigatus colonizing the airways of patients with asthma and cystic fibrosis. The common manifestations include treatment-resistant asthma, transient and fleeting pulmonary opacities and bronchiectasis. It is believed that globally there are about five million cases of ABPA, with India alone accounting for about 1.4 million cases. The occurrence of ABPA among asthmatic patients in special clinics may be as high as 13 per cent. Thus, a high degree of suspicion for ABPA should be entertained while treating a patient with bronchial asthma, particularly in specialized clinics. Early diagnosis and appropriate treatment can delay (or even prevent) the onset of bronchiectasis, which suggests that all patients of bronchial asthma should be screened for ABPA, especially in chest clinics. The current review summarizes the recent advances in the pathogenesis, diagnosis and management of ABPA.

Prevalence of Vitamin D Deficiency in Treatment-Naïve Subjects with Chronic Pulmonary Aspergillosis

The association of vitamin D deficiency in the pathogenesis of invasive and allergic pulmonary aspergillosis is known. Whether vitamin D deficiency is prevalent in chronic pulmonary aspergillosis (CPA) remains unknown. We evaluated the prevalence of vitamin D deficiency in subjects with CPA. We compared the clinicoradiological features, microbiology, the immunological response, and the severity of CPA in those with or without vitamin D deficiency. We measured plasma vitamin D levels in 230 consecutive treatment-naïve subjects with CPA and 78 controls (28 with prior tuberculosis (TB); 50 healthy controls). We defined vitamin D deficiency as 25(OH)D3 level <20 ng/mL. The mean (95% confidence intervals (CI)) levels of plasma vitamin D levels were 19.5 (17.6–21.4), 18.6 (13.9–23.3), and 15.3 (12.6–17.9) ng/mL in subjects with CPA, diseased controls, and healthy controls, respectively; and the levels were not different between the groups. The prevalence of vitamin D deficiency in subjects with CPA was 65% (n = 150) and was also not different between healthy (70%) or diseased (61%) controls. We did not find any difference in the clinicoradiological features, microbiology, immunological response, and severity of CPA between vitamin D sufficient and deficient groups. The prevalence of vitamin D deficiency is high in subjects with CPA, albeit similar to controls. Vitamin D deficiency does not affect the disease severity in subjects with CPA.

Pentraxin-3 polymorphisms and pulmonary fungal disease in non-neutropenic patients

Background

Pentraxin 3 (PTX3) plays a non-redundant role in innate immunity against fungal diseases. Although single nucleotide polymorphisms (SNPs) of PTX3 are associated with a higher risk of invasive aspergillosis among the immunosuppressed population and chronic obstructive pulmonary disease patients, it is unknown whether PTX3 genetic variants influence the risk of pulmonary fungal disease in immunocompetent patients.

Methods

To investigate the association between PTX3 gene polymorphisms and pulmonary mycosis in non-neutropenic patients, we conducted a case-control study in a tertiary hospital department. Forty-five patients were identified using the criteria of the European Organization for Research and Treatment of Cancer/Invasive Fungal Infections Cooperative Group and the National Institute of Allergy and Infectious Diseases Mycoses Study Group (EORTC-MSG) and enrolled in the case group. Of these patients, 15 had allergic bronchopulmonary aspergillosis (ABPA), 10 had invasive pulmonary aspergillosis (IPA), 18 had pulmonary cryptococcosis, and 2 had other types of pulmonary mycosis. One hundred and twenty-two non-neutropenic inpatients not infected by fungal disease were randomly selected as the control group. We detected three SNPs (rs2305619, rs3816527, and rs1840680) within the PTX3 gene using polymerase chain reaction sequencing and compared their associations with different types of pulmonary fungal disease.

Results

Three SNPs were consistent with Hardy-Weinberg equilibrium (HWE). SNP rs2305619 was in linkage disequilibrium with rs3816527 (D’=0.85) and rs1840680 (D’=0.85), respectively. There was no difference in the genotypic distribution and haplotype frequency of the SNPs between the case group and the control group. When we focused on invasive mold infections as a subgroup, we found that the SNP rs3816527 CC homozygote was associated with a higher risk of IPA (OR, 7.37; 95% CI, 0.93–44.44; P=0.033), while the rs3816527 AA homozygote might lower the risk of pulmonary cryptococcosis (OR, 0.35; 95% CI, 0.11–0.96; P=0.047). No genotypic distribution differences were observed for the other two SNPs (rs2305619 and rs1840680). When it came to the comparison between ABPA subgroup and control group, no difference in single nucleotide polymorphism was observed.

Conclusions

This study showed that the SNP rs3816527 is associated with IPA in non-neutropenic patients. Further investigations in large populations are needed to validate this genetic predisposition. Functional studies are also required.

Retrospective analysis of the association of the expression and single nucleotide polymorphisms (SNPs) of the TLR4, PTX3 and Dectin-1 (CLEC/A) genes with development of invasive aspergillosis among haematopoietic stem cell transplant recipients with oncohaematological disorders

OBJECTIVES

Several studies described single nucleotide polymorphisms (SNPs) on pattern recognition receptor (PRR) such as toll-like receptors (TLRs), dendritic cell-associated C-type lectin-1 (Dectin-1/CLEC7A) genes of patients with invasive fungal infections (IFIs) caused by Candida and Aspergillus. We screened TLR4, Dectin-1 and PTX3 polymorphisms in a Turkish population with invasive aspergillosis (IA) underlying haematological malignancies.

METHODS

In this case-control study, a cohort of 59 patients with haematological malignancies were included. There were 26 IA patients assigned by the EORTC-MSG criteria and 33 patients with no evidence of fungal disease. DNA and RNA were isolated from frozen bone marrow and serum samples. RNA levels and polymorphisms of TLR4 (rs4986790, rs4986791), Dectin-1 (rs16910526, rs7309123) and PTX3 (rs2305619, rs3816527) were determined. The odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were calculated by unconditional logistic regression analysis.

RESULTS AND CONCLUSIONS

TLR4, PTX3 and Dectin-1 genes were downregulated in aspergillosis cohort under similar haematological conditions. TLR4 expression was 0.0626 ± 0.032 in controls when compared to IA patients as 0.0077 ± 0.014, and the difference was significant (P = .026). There was a difference in also the PTX3 gene among IA (0.0043 ± 0.004) and control (0.5265 ± 0.0043) groups (P = .035). The Dectin-1 (CLEC/A) expression was downregulated in IA group (0.1887 ± 0.072 & 0.0655 ± 0.010) but not statistically significant (P > .05). Conditional logistic regression analyses indicated that the GT genotype of rs16910526 polymorphism in Dectin-1 gene was associated with lower risk of IA (odds ratio = 3.635, 95% confidence interval = 0.690-3.138, P = .04).

Polymorphisms in TNF Receptor Superfamily 1B (TNFRSF1B:rs3397) are Linked to Mycobacterium avium paratuberculosis Infection and Osteoporosis in Rheumatoid Arthritis

We previously discovered that single nucleotide polymorphisms (SNPs) in PTPN2/22 (T-cell negative-regulators) occur in 78% of rheumatoid arthritis (RA), along with Mycobacterium avium paratuberculosis (MAP) infection in 33% of patients. In Crohn's disease, we reported that SNPs in TNFα and receptors (TNFRSF1A/TNFRSF1B) benefited intracellular MAP-survival, increased infection, and elevated inflammatory response mimicking the poor response to anti-TNFα treatment in some patients. Here, we studied the frequency and effects of SNPs in TNFα/TNFRSF1A/TNFRSF1B in RA including gene expression, MAP infection, and osteoporosis marker levels in blood (54 RA and 48 healthy controls). TNFα:rs1800629 (GA) was detected in 19/48 (40%) RA and 8/54 (15%) controls (p-value < 0.05, odds ratio (OR) = 3.6, 95% CI: 1.37-9.54). TNFRS1B:rs3397 (CT) was detected in 21/48 (44%) RA and 10/54 (19%) controls (p-value < 0.05, OR = 4.43, 95% CI: 1.73-11.33). In RA, rs3397 downregulated TNFRSF1B expression (CC > CT (0.34 ± 0.14) and CC > TT (0.27 ± 0.12)), compared to wildtype CC (0.51 ± 0.17), p-value < 0.05. MAP DNA was detected significantly in 17/48 (35.4%) RA compared to 11/54 (20.4%) controls (p-value < 0.05, OR = 2.14, 95% CI: 1.12-5.20). The average osteocalcin level was significantly lower (p-value < 0.05) in RA (2.70 ± 0.87 ng/mL), RA + MAP (0.60 ± 0.31 ng/mL), RA + TNFRSF1B:rs3397 (TT) (0.67 ± 0.35 ng/mL), compared to the healthy control (5.31 ± 1.39 ng/mL), and MAP-free RA (3.85 ± 1.31 ng/mL). Overall, rs3397 appears to downregulate TNFRSF1B, increase MAP infection, worsen inflammation, and cause osteocalcin deficiency and possibly osteoporosis in RA.

Searching for Bacteria in Neural Tissue From Amyotrophic Lateral Sclerosis

Despite great efforts in the investigation, the exact etiology of amyotrophic lateral sclerosis (ALS) is a matter of intensive research. We recently advanced the idea that ALS might be caused by fungal infection. Indeed, fungal yeast and hyphal structures can be directly visualized in neural tissue of ALS patients, and a number of fungal species have been identified in the central nervous system (CNS). In the present work, we tested the possibility that bacterial infections can accompany these mycoses. Our findings establish the presence of bacterial DNA in different regions of the CNS from all ALS patients examined. Specifically, we used PCR and next generation sequencing (NGS) to precisely determine the bacterial species present in ALS tissue. Consistent with these findings, immunohistochemistry analysis of CNS sections using specific anti-bacterial antibodies identified prokaryotic cells in neural tissue. Finally, we assayed for the repeat expansion of the hexanucleotide repeat GGGGCC in C9orf72, which is considered the most common genetic cause of ALS in patients, using DNA extracted from ALS CNS tissue. We failed to find this repeated sequence in any of the eleven patients analyzed. Our results indicate that bacterial DNA and prokaryotic cells are present in CNS tissue, leading to the concept that both fungal and bacterial infections coexist in patients with ALS. These observations lay the groundwork for the use of appropriate therapies to eradicate the polymicrobial infections in ALS.

Association between polymorphisms in the genes encoding toll-like receptors and dectin-1 and susceptibility to invasive aspergillosis: a systematic review

Invasive aspergillosis is a common fungal infection in immunocompromised individuals. Some studies have shown that toll-like receptor and dectin-1 genetic polymorphisms may alter signaling pathways, thus increasing an individual's susceptibility to invasive aspergillosis. We investigated the pertinent literature to determine whether polymorphisms in the genes encoding toll-like receptors and dectin-1 increase the susceptibility to invasive aspergillosis. This study systematically reviewed the literature using the databases PubMed/PMC, Scopus, and Web of Science using the keywords invasive aspergillosis, polymorphism, Toll-like, and Dectin-1. From the initial search, 415 studies were found and according to our inclusion and exclusion criteria, eight studies were selected. Several studies described single-nucleotide polymorphisms (SNPs) that are associated with a greater susceptibility to invasive aspergillosis. These SNPs were found in the genes that encode toll-like receptors 1, 3, 4, and 5 and the gene that encodes dectin-1; upon activation, both cellular receptors initiate a signaling cascade that can result in the production of cytokines and chemokines. Thus, our literature review uncovered a significant association between polymorphisms in the genes that encode toll-like receptors and dectin-1 and invasive aspergillosis. More studies should be performed to better understand the relationship between toll-like receptor and dectin-1 genetic polymorphisms and invasive aspergillosis susceptibility.

Human NK cells adapt their immune response towards increasing multiplicities of infection of Aspergillus fumigatus

BACKGROUND

The saprophytic fungus Aspergillus fumigatus reproduces by generation of conidia, which are spread by airflow throughout nature. Since humans are inhaling certain amounts of spores every day, the (innate) immune system is constantly challenged. Even though macrophages and neutrophils carry the main burden, also NK cells are regarded to contribute to the antifungal immune response. While NK cells reveal a low frequency, expression and release of immunomodulatory molecules seem to be a natural way of their involvement.

RESULTS

In this study we show, that NK cells secrete chemokines such as CCL3/MIP-1α, CCL4/MIP-1β and CCL5/RANTES early on after stimulation with Aspergillus fumigatus and, in addition, adjust the concentration of chemokines released to the multiplicity of infection of Aspergillus fumigatus.

CONCLUSIONS

These results further corroborate the relevance of NK cells within the antifungal immune response, which is regarded to be more and more important in the development and outcome of invasive aspergillosis in immunocompromised patients after hematopoietic stem cell transplantation. Additionally, the correlation between the multiplicity of infection and the expression and release of chemokines shown here may be useful in further studies for the quantification and/or surveillance of the NK cell involvement in antifungal immune responses.

Common Genetic Polymorphisms within NFκB-Related Genes and the Risk of Developing Invasive Aspergillosis

Invasive Aspergillosis (IA) is an opportunistic infection caused by Aspergillus, a ubiquitously present airborne pathogenic mold. A growing number of studies suggest a major host genetic component in disease susceptibility. Here, we evaluated whether 14 single-nucleotide polymorphisms within NFκB1, NFκB2, RelA, RelB, Rel, and IRF4 genes influence the risk of IA in a population of 834 high-risk patients (157 IA and 677 non-IA) recruited through a collaborative effort involving the aspBIOmics consortium and four European clinical institutions. No significant overall associations between selected SNPs and the risk of IA were found in this large cohort. Although a hematopoietic stem cell transplantation (HSCT)-stratified analysis revealed that carriers of the IRF4_{rs12203592T/T} genotype had a six-fold increased risk of developing the infection when compared with those carrying the C allele (OR_REC = 6.24, 95%CI 1.25–31.2, P = 0.026), the association of this variant with IA risk did not reach significance at experiment-wide significant threshold. In addition, we found an association of the IRF4_AATC and IRF4_GGTC haplotypes (not including the IRF4_rs12203592T risk allele) with a decreased risk of IA but the magnitude of the association was similar to the one observed in the single-SNP analysis, which indicated that the haplotypic effect on IA risk was likely due to the IRF4_rs12203592 SNP. Finally, no evidence of significant interactions among the genetic markers tested and the risk of IA was found. These results suggest that the SNPs on the studied genes do not have a clinically relevant impact on the risk of developing IA.

Genetic Susceptibility to Fungal Infections: What is in the Genes?

The development of severe fungal infections has long been associated with traditional risk factors such as profound immunosuppression, yet it remains challenging to understand why under similar conditions only some patients will develop these infections while others will not. Recent studies have demonstrated the importance of host genetic variation in influencing the severity and susceptibility to invasive fungal infections (IFIs). In this review, we examine selected primary immunodeficiencies characterized by their vulnerability to a narrow range of fungal pathogens, and then focus on recently identified genetic polymorphisms associated with an increased susceptibility to IFIs.

Gene expression profiles of human dendritic cells interacting with Aspergillus fumigatus in a bilayer model of the alveolar epithelium/endothelium interface

The initial stages of the interaction between the host and Aspergillus fumigatus at the alveolar surface of the human lung are critical in the establishment of aspergillosis. Using an in vitro bilayer model of the alveolus, including both the epithelium (human lung adenocarcinoma epithelial cell line, A549) and endothelium (human pulmonary artery epithelial cells, HPAEC) on transwell membranes, it was possible to closely replicate the in vivo conditions. Two distinct sub-groups of dendritic cells (DC), monocyte-derived DC (moDC) and myeloid DC (mDC), were included in the model to examine immune responses to fungal infection at the alveolar surface. RNA in high quantity and quality was extracted from the cell layers on the transwell membrane to allow gene expression analysis using tailored custom-made microarrays, containing probes for 117 immune-relevant genes. This microarray data indicated minimal induction of immune gene expression in A549 alveolar epithelial cells in response to germ tubes of A. fumigatus. In contrast, the addition of DC to the system greatly increased the number of differentially expressed immune genes. moDC exhibited increased expression of genes including CLEC7A, CD209 and CCL18 in the absence of A. fumigatus compared to mDC. In the presence of A. fumigatus, both DC subgroups exhibited up-regulation of genes identified in previous studies as being associated with the exposure of DC to A. fumigatus and exhibiting chemotactic properties for neutrophils, including CXCL2, CXCL5, CCL20, and IL1B. This model closely approximated the human alveolus allowing for an analysis of the host pathogen interface that complements existing animal models of IA.

Evaluation of the conjunctival fungal flora and its susceptibility to antifungal agents in healthy horses in Switzerland

OBJECTIVE

To characterize the conjunctival fungal flora and to determine the susceptibility of 2 isolated molds to antifungal drugs in samples of 64 healthy horses from The National Stud in Switzerland.

PROCEDURE

Conjunctival cytobrush samples were collected from both eyes of 64 ophthalmologically normal horses in August 2012 and subsequently cultured on Sabouraud's agar medium. Growing fungi were identified and counted. Etests or broth microdilution tests for Aspergillus fumigatus and Eurotium amstelodami were carried out to determine antifungal drug sensitivity. These species had previously been detected in samples from eyes with keratomycosis in Switzerland. Minimal inhibitory concentrations (MICs) for voriconazole, fluconazole, itraconazole, amphotericin B, and miconazole were recorded.

RESULTS

Fifty-nine of the horses were tested positive for fungal growth from at least one eye (92%). Eleven genera of fungi were identified. The most common fungal genera were Alternaria, Eurotium, Rhizopus, and Cladosporium. Aspergillus spp. and Penicillium spp. were isolated frequently, while no Fusarium spp. was found. In only 2 cases, yeasts were identified as Candida guilliermondii. For certain fungal species, the type of bedding and housing appeared to influence their prevalence. Susceptibility testing of A. fumigatus showed lowest MICs for voriconazole, E. amstelodami for voriconazole and itraconazole. High MICs for fluconazole were detected for all tested fungi while MICs for amphotericin B and miconazole were variable.

CONCLUSIONS

A large range of fungal mold species was identified including A. fumigatus and E. amstelodami, which have been causative agents of keratomycosis in Switzerland. Best in vitro susceptibility results for these two species were obtained for voriconazole.

Dectin-1 and DC-SIGN polymorphisms associated with invasive pulmonary Aspergillosis infection

The recognition of pathogen-derived structures by C-type lectins and the chemotactic activity mediated by the CCL2/CCR2 axis are critical steps in determining the host immune response to fungi. The present study was designed to investigate whether the presence of single nucleotide polymorphisms (SNPs) within DC-SIGN, Dectin-1, Dectin-2, CCL2 and CCR2 genes influence the risk of developing Invasive Pulmonary Aspergillosis (IPA). Twenty-seven SNPs were selected using a hybrid functional/tagging approach and genotyped in 182 haematological patients, fifty-seven of them diagnosed with proven or probable IPA according to the 2008 EORTC/MSG criteria. Association analysis revealed that carriers of the Dectin-1(rs3901533 T/T) and Dectin-1(rs7309123 G/G) genotypes and DC-SIGN(rs4804800 G), DC-SIGN(rs11465384 T), DC-SIGN(7248637 A) and DC-SIGN(7252229 C) alleles had a significantly increased risk of IPA infection (OR = 5.59 95%CI 1.37-22.77; OR = 4.91 95%CI 1.52-15.89; OR = 2.75 95%CI 1.27-5.95; OR = 2.70 95%CI 1.24-5.90; OR = 2.39 95%CI 1.09-5.22 and OR = 2.05 95%CI 1.00-4.22, respectively). There was also a significantly increased frequency of galactomannan positivity among patients carrying the Dectin-1(rs3901533_T) allele and Dectin-1(rs7309123_G/G) genotype. In addition, healthy individuals with this latter genotype showed a significantly decreased level of Dectin-1 mRNA expression compared to C-allele carriers, suggesting a role of the Dectin-1(rs7309123) polymorphism in determining the levels of Dectin-1 and, consequently, the level of susceptibility to IPA infection. SNP-SNP interaction (epistasis) analysis revealed significant interactions models including SNPs in Dectin-1, Dectin-2, CCL2 and CCR2 genes, with synergistic genetic effects. Although these results need to be further validated in larger cohorts, they suggest that Dectin-1, DC-SIGN, Dectin-2, CCL2 and CCR2 genetic variants influence the risk of IPA infection and might be useful in developing a risk-adapted prophylaxis.