Host response to fungal infections - how immunology and host genetics could help to identify and treat patients at risk.

In spite of the ever-increasing incidence and poor outcome of invasive fungal infections in immune compromised patients, there is currently no reliable method to accurately predict the risk, to monitor the outcome and to treat these infections. Protective immunity against Candida and Aspergillus depends on a highly coordinated interaction between the innate and adaptive immune systems. Genetic and immunological defects in components of these networks result in increased risk of invasive fungal infections among patients undergoing chemotherapy or transplant recipients. We review the most important genetic and immunological factors that influence human susceptibility to Candida and Aspergillus infections and discuss the potential role of basic research to promote precision medicine for infectious diseases. We discuss how immunogenetic studies can help to provide tools for improved identification of high-risk patients and the development of tailored antifungal therapies

Immune recovery in HIV-infected patients after candida esophagitis is impaired despite long-term antiretroviral therapy.

OBJECTIVE Candida esophagitis belongs to the most common AIDS-defining diseases, however, a comprehensive immune pathogenic concept is lacking. DESIGN We investigated the immune status of 37 HIV-1-infected patients from the Swiss HIV cohort study at diagnosis of Candida esophagitis, 1 year before, 1 year later and after 2 years of suppressed HIV RNA. We compared these patients to 3 groups: 37 HIV-1-infected patients without Candida esophagitis but similar CD4 counts as the patients at diagnosis (advanced HIV group), 15 HIV-1-infected patients with CD4 counts >500 cells/μl, CD4 nadir >350 cells/μl and suppressed HIV RNA under combination antiretroviral therapy (cART) (early cART group), and 20 healthy individuals. METHODS We investigated phenotype, cytokine production and proliferative capacity of different immune cells by flow cytometry and ELISpot. RESULTS We found that patients with Candida esophagitis had nearly abolished CD4 proliferation in response to C. albicans, significantly increased percentages of dysfunctional CD4 cells, significantly decreased cytotoxic NK-cell counts and peripheral innate lymphoid cells and significantly reduced IFN-γ and IL-17 production compared to the early cART group and healthy individuals. Most of these defects remained for more than 2 years despite viral suppression. The advanced HIV group without opportunistic infection showed partly improved immune recovery. CONCLUSIONS Our data indicate that Candida esophagitis in HIV-1-infected patients is caused by an accumulation of multiple, partly Candida-specific immunological defects. Long-term immune recovery is impaired, illustrating that specific immunological gaps persist despite cART. These data also support the rationale for early cART initiation to prevent irreversible immune defects

Dectin-1 isoforms contribute to distinct Th1/Th17 cell activation in mucosal candidiasis

We thank Dr. Cristina Massi Benedetti for digital art and editingRecognition of β-glucans by dectin-1 has been shown to mediate cell activation, cytokine production and a variety of antifungal responses. Here, we report that the functional activity of dectin-1 in mucosal immunity to Candida albicans is influenced by the genetic background of the host. Dectin-1 was required for the proper control of gastrointestinal and vaginal candidiasis in C57BL/6 but not BALB/c mice, the latter actually showing increased resistance in the absence of dectin-1. Susceptibility of dectin-1-deficient C57BL/6 mice to infection was associated with defective IL-17A, aryl hydrocarbon receptor-dependent IL-22 production as well as adaptive Th1 responses. In contrast, resistance of dectin-1-deficient BALB/c mice was associated with increased IL-17A and IL-22 production, and the skewing towards Th1/Treg immune responses that provide immunological memory. Disparate canonical/noncanonical NF-κB signaling pathways downstream dectin-1were activated in the two different mouse strains. Thus, the net activity of dectin-1 in antifungal mucosal immunity is dependent on the host’s genetic background that affects both the innate cytokine production as well as the adaptive Th1/Th17 cell activation upon dectin-1 signaling.The studies were supported by the Specific Targeted Research Project “ALLFUN” (FP7−HEALTH−2009 contract number 260338 to LR) and the Italian Project AIDS 2010 by ISS (Istituto Superiore di Sanità - contract number 40H40 to LR) and Fondazione Cassa di Risparmio di Perugia Project n. 2011.0124.021. AC and CC were financially supported by fellowships from Fundação para a Ciência e Tecnologia, Portugal (contracts SFRH/BPD/46292/2008 and SFRH/BD/65962/2009, respectively)

Lack of association of the CIITA -168A→G promoter SNP with myasthenia gravis and its role in autoimmunity

<p>Abstract</p> <p>Background</p> <p>The major histocompatibility complex class II transactivator (CIITA) regulates MHC class II gene expression. A promoter SNP -168A→G (rs3087456) has previously been shown to be associated with susceptibility to several immune mediated disorders, including rheumatoid arthritis (RA), multiple sclerosis (MS) and myocardial infarction (MI). Myasthenia gravis (MG) is an autoimmune disorder which has previously been shown to be associated with polymorphisms of several autoimmune predisposing genes, including <it>IL-1</it>, <it>PTPN22</it>, <it>TNF-α </it>and the <it>MHC</it>. In order to determine if allelic variants of rs3087456 increase predisposition to MG, we analyzed this SNP in our Swedish cohort of 446 MG patients and 1866 controls.</p> <p>Results</p> <p>No significant association of the SNP with MG was detected, neither in the patient group as a whole, nor in any clinical subgroup. The vast majority of previous replication studies have also not found an association of the SNP with autoimmune disorders.</p> <p>Conclusions</p> <p>We thus conclude that previous findings with regard to the role of the <it>CIITA </it>-168A→G SNP in autoimmunity may have to be reconsidered.</p

The impact of the Fungus-Host-Microbiota interplay upon Candida albicans infections : current knowledge and new perspectives

ACKNOWLEDGEMENTS: We thank our friends and colleagues in the medical mycology, fungal immunology and microbiota fields for many thought-provoking discussions. FUNDING: We received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie action, Innovative Training Network: FunHoMic; grant N° 812969. CdE received funding from the French Government ‘Investissement d’Avenir’ program (Laboratoire d’Excellence Integrative Biology of Emerging Infectious Diseases, ANR-10-LABX-62-IBEID), the Agence Nationale de la Recherche (ERA-Net Infect-ERA, FUNCOMPATH, ANR-14-IFEC-0004), the EU Horizon2020 consortium “Host-Directed Medicine in invasive FUNgal infections” - HDM-FUN (Grant Agreement 847507). SLL and CdE received funding from the Swiss National Science Foundation (Sinergia program, #CRSII5_173863). BIOASTER received funding from the French Government ‘Investissement d’Avenir’ program (Grant No. ANR-10-AIRT-03). MSG was supported by a Humboldt Research Fellowship for Postdoctoral Researchers by the Alexander von Humboldt-Foundation and the Deutsche Forschungsgemeinschaft (DFG) Emmy Noether Program (project no. 434385622 / GR 5617/1-1). BH was supported by the Deutsche Forschungsgemeinschaft (DFG) project Hu 532/20-1, project C1 within the Collaborative Research Centre (CRC)/Transregio 124 FungiNet and the Balance of the Microverse Cluster under Germany´s Excellence Strategy – EXC 2051 – Project-ID 390713860, the EU Horizon2020 consortium “Host-Directed Medicine in invasive FUNgal infections” - HDM-FUN (Grant Agreement 847507), the Leibniz Association Campus InfectoOptics SAS-2015-HKI-LWC and the Wellcome Trust (215599/Z/19/Z). IDJ was supported by the Deutsche orschungsgemeinschaft (DFG) project C5 within the Collaborative Research Centre (CRC)/Transregio 124 FungiNet and the Balance of the Microverse Cluster under Germany´s Excellence Strategy – EXC 2051 – Project-ID 390713860, the Leibniz Association Campus InfectoOptics SAS-2015-HKI-LWC and the Wellcome Trust (Grant 215599/Z/19/Z). CM received funding from the the Instituto de Salud Carlos III/FEDER. MGN was supported by an ERC Advanced Grant (#833247) and a Spinoza grant of the Netherlands Organization for Scientific Research. CAM was supported by EU Horizon2020 consortium “Host-Directed Medicine in invasive FUNgal infections” -HDM-FUN (Grant Agreement 847507) and the Wellcome Trust Strategic Award for Medical Mycology and Fungal Immunology (097377/Z/11/Z). AWW receives core funding support from the Scottish Government’s Rural and Environment Science and Analytical Services (RESAS). AJPB was supported by a programme grant from the UK Medical Research Council (MR/M026663/1) and by the Medical Research Council Centre for Medical Mycology at the University of Exeter (MR/N006364/1).Peer reviewedPublisher PD

Dectin-1: a role in antifungal defense and consequences of genetic polymorphisms in humans

The clinical relevance of fungal infections has increased dramatically in recent decades as a consequence of the rise of immunocompromised populations, and efforts to understand the underlying mechanisms of protective immunity have attracted renewed interest. Here we review Dectin-1, a pattern recognition receptor involved in antifungal immunity, and discuss recent discoveries of polymorphisms in the gene encoding this receptor which result in human disease

PPARγ Controls Dectin-1 Expression Required for Host Antifungal Defense against Candida albicans

We recently showed that IL-13 or peroxisome proliferator activated receptor γ (PPARγ) ligands attenuate Candida albicans colonization of the gastrointestinal tract. Here, using a macrophage-specific Dectin-1 deficient mice model, we demonstrate that Dectin-1 is essential to control fungal gastrointestinal infection by PPARγ ligands. We also show that the phagocytosis of yeast and the release of reactive oxygen intermediates in response to Candida albicans challenge are impaired in macrophages from Dectin-1 deficient mice treated with PPARγ ligands or IL-13. Although the Mannose Receptor is not sufficient to trigger antifungal functions during the alternative activation of macrophages, our data establish the involvement of the Mannose Receptor in the initial recognition of non-opsonized Candida albicans by macrophages. We also demonstrate for the first time that the modulation of Dectin-1 expression by IL-13 involves the PPARγ signaling pathway. These findings are consistent with a crucial role for PPARγ in the alternative activation of macrophages by Th2 cytokines. Altogether these data suggest that PPARγ ligands may be of therapeutic value in esophageal and gastrointestinal candidiasis in patients severely immunocompromised or with metabolic diseases in whom the prevalence of candidiasis is considerable

Selective C-Rel Activation via Malt1 Controls Anti-Fungal TH-17 Immunity by Dectin-1 and Dectin-2

C-type lectins dectin-1 and dectin-2 on dendritic cells elicit protective immunity against fungal infections through induction of TH1 and TH-17 cellular responses. Fungal recognition by dectin-1 on human dendritic cells engages the CARD9-Bcl10-Malt1 module to activate NF-κB. Here we demonstrate that Malt1 recruitment is pivotal to TH-17 immunity by selective activation of NF-κB subunit c-Rel, which induces expression of TH-17-polarizing cytokines IL-1β and IL-23p19. Malt1 inhibition abrogates c-Rel activation and TH-17 immunity to Candida species. We found that Malt1-mediated activation of c-Rel is similarly essential to induction of TH-17-polarizing cytokines by dectin-2. Whereas dectin-1 activates all NF-κB subunits, dectin-2 selectively activates c-Rel, signifying a specialized TH-17-enhancing function for dectin-2 in anti-fungal immunity by human dendritic cells. Thus, dectin-1 and dectin-2 control adaptive TH-17 immunity to fungi via Malt1-dependent activation of c-Rel

Neutrophil-specific deletion of the CARD9 gene expression regulator suppresses autoantibody-induced inflammation in vivo

Neutrophils are terminally differentiated cells with limited transcriptional activity. The biological function of their gene expression changes is poorly understood. CARD9 regulates transcription during antifungal immunity but its role in sterile inflammation is unclear. Here we show that neutrophil CARD9 mediates pro-inflammatory chemokine/cytokine but not lipid mediator release during non-infectious inflammation. Genetic deficiency of CARD9 suppresses autoantibody-induced arthritis and dermatitis in mice. Neutrophil-specific deletion of CARD9 is sufficient to induce that phenotype. Card9(-/-) neutrophils show defective immune complex-induced gene expression changes and pro-inflammatory chemokine/cytokine release but normal LTB4 production and other short-term responses. In vivo deletion of CARD9 reduces tissue levels of pro-inflammatory chemokines and cytokines but not LTB4. The CARD9-mediated signalling pathway involves Src-family kinases, Syk, PLCγ2, Bcl10/Malt1 and NFκB. Collectively, CARD9-mediated gene expression changes within neutrophils play important roles during non-infectious inflammation in vivo and CARD9 acts as a divergence point between chemokine/cytokine and lipid mediator release

Chronic mucocutaneous candidiasis in APECED or thymoma patients correlates with autoimmunity to Th17-associated cytokines

Chronic mucocutaneous candidiasis (CMC) is frequently associated with T cell immunodeficiencies. Specifically, the proinflammatory IL-17A–producing Th17 subset is implicated in protection against fungi at epithelial surfaces. In autoimmune polyendocrinopathy candidiasis ectodermal dystrophy (APECED, or autoimmune polyendocrine syndrome 1), CMC is often the first sign, but the underlying immunodeficiency is a long-standing puzzle. In contrast, the subsequent endocrine features are clearly autoimmune, resulting from defects in thymic self-tolerance induction caused by mutations in the autoimmune regulator (AIRE). We report severely reduced IL-17F and IL-22 responses to both Candida albicans antigens and polyclonal stimulation in APECED patients with CMC. Surprisingly, these reductions are strongly associated with neutralizing autoantibodies to IL-17F and IL-22, whereas responses were normal and autoantibodies infrequent in APECED patients without CMC. Our multicenter survey revealed neutralizing autoantibodies against IL-17A (41%), IL-17F (75%), and/ or IL-22 (91%) in >150 APECED patients, especially those with CMC. We independently found autoantibodies against these Th17-produced cytokines in rare thymoma patients with CMC. The autoantibodies preceded the CMC in all informative cases. We conclude that IL-22 and IL-17F are key natural defenders against CMC and that the immunodeficiency underlying CMC in both patient groups has an autoimmune basis