Chronic Fungal Disease Research Articles

Drivers of diversification in fungal pathogen populations.

To manage and treat chronic fungal diseases effectively, we require an improved understanding of their complexity. There is an increasing appreciation that chronic infection populations are often heterogeneous due to diversification and drift, even within a single microbial species. Genetically diverse populations can contribute to persistence and resistance to treatment by maintaining cells with different phenotypes capable of thriving in these dynamic environments. In chronic infections, fungal pathogens undergo prolonged challenges that can drive trait selection to convergent adapted states through restricted access to critical nutrients, assault by immune effectors, competition with other species, and antifungal drugs. This review first highlights the various genetic and epigenetic mechanisms that promote diversity in pathogenic fungal populations and provide an additional barrier to assessing the actual heterogeneity of fungal infections. We then review existing studies of evolution and genetic heterogeneity in fungal populations from lung infections associated with the genetic disease cystic fibrosis. We conclude with a discussion of open research questions that, once answered, may aid in diagnosing and treating chronic fungal infections.

A MYB family transcription factor TdRCA1 from wild emmer wheat regulates anthocyanin biosynthesis in coleoptile.

As important secondary metabolites in plants, anthocyanins not only contribute to colored plants organs, but also provide protections against various biotic and abiotic stresses. In this study, a MYB transcription factor gene TdRCA1 from wild emmer wheat regulating anthocyanin biosynthesis in wheat coleoptile was identified on the short arm of chromosome 7A in common wheat genetic background. The TdRCA1 overexpression lines showed colored callus, coleoptile, auricle and stem nodes, as well as up regulation of six anthocyanin-related structural genes. The expression of TdRCA1 was activated by light in a temporal manner. While coleoptile color of 48 and 60h dark-grown seedlings changed from green to red after 24h light treatment, those grown in dark for 72 and 96h failed to develop red coleoptiles after light restoration. Interestingly, the over expression of TdRCA1 resulted in increased resistance to Fusarium crown rot, a chronic and severe fungal disease in many cereal growing regions in the world. Our results offer a better understanding of the molecular basis of coleoptile color in bread wheat.

Sporothrix schenckii complex in felines: Analysis of clinical, mycological, environmental and epidemiological factors

Sporotrichosis is an infectious and chronic fungal disease caused by fungi belonging to the Sporothrix schenckii complex that affects humans and animals through traumatic implantation of the fungus in the skin. They are dimorphic, saprophytic and geophilic fungi that are widely distributed in nature, especially in soils rich in organic matter. The aim of this study was to understand the clinical, mycological, environmental and epidemiological aspects of the Sporothrix schenckii complex in felines. In order to meet the objectives of this research, a qualitative, descriptive and exploratory data survey was carried out through a bibliographic review based on works published in the last 23 years. Sporothrix spp. is considered to be a complex of at least six cryptic species, in other words, they have similar morphological characteristics but different genotypes. In cats, the incubation period is variable; it usually lasts 14 days. On penetrating the tissue, the micellar form transforms into yeast, which generates an inflammatory response and proliferation of the microorganism at the site, causing papular and nodular lesions which, in some cases, heal spontaneously. Therefore, it is clear that sporotrichosis is caused by dimorphic fungi of the Sporothrix schenkii complex. It is a zoonotic disease of great importance in the context of public health, since it is still a neglected disease and requires robust measures to control. As well as being the most seriously affected, felines are the main transmitters to humans and animals, making them a key point in controlling outbreaks of the disease.

Essential Oils and their Components in Combating Fungal Pathogens of Human Skin-lipophilic Yeast Malassezia furfur

The most common problem of modern medicine is the development of increasing antifungal drug resistance nowadays including fungal infections of the skin and its appendages caused by dermatomycetes, yeast-like fungi, and molds so, there will be a need for alternative antifungal treatment. Natural substances with high antifungal properties like essential oils and their components show potential in this regard. Citrus lemon and Citrus sinensis essential oils were screened against Malassezia furfur by disc diffusion method and Minimum Inhibitory Concentration was determined by Modified Microdilution method. Citrus lemon (lemon) and Citrus sinensis (orange) show excellent inhibitory effects on the lipophilic, yeast-like fungus Malassezia furfur which causes Pityriasis versicolor, a chronic superficial fungal disease of the skin. The diameter of the inhibition zone was found to be 70 mm and 60 mm respectively. Malassezia furfur was found to be resistant against Clotrimazole & Ketoconazole. The minimum inhibitory concentration (MIC) of lemon and orange oil against Malassezia furfur was found to be 0.6 µl/ml and 0.8 µl/ml. These findings concluded that the use of Citrus lemon (lemon) and Citrus sinensis (orange) oil showed remarkable and excellent antifungal activity, and can be used as a traditional herbal medicine for the control of Pityriasis versicolor infection of the skin after undergoing clinical trials.

Blocking the CTLA-4 and PD-1 pathways during pulmonary paracoccidioidomycosis improves immunity, reduces disease severity, and increases the survival of infected mice.

Immune checkpoint pathways, i.e., coinhibitory pathways expressed as feedback following immune activation, are crucial for controlling an excessive immune response. Cytotoxic T lymphocyte antigen-4 (CTLA-4) and programmed cell death protein-1 (PD-1) are the central classical checkpoint inhibitory (CPI) molecules used for the control of neoplasms and some infectious diseases, including some fungal infections. As the immunosuppression of severe paracoccidioidomycosis (PCM), a chronic granulomatous fungal disease, was shown to be associated with the expression of coinhibitory molecules, we hypothesized that the inhibition of CTLA-4 and PD-1 could have a beneficial effect on pulmonary PCM. To this end, C57BL/6 mice were infected with Paracoccidioides brasiliensis yeasts and treated with monoclonal antibodies (mAbs) α-CTLA-4, α-PD-1, control IgG, or PBS. We verified that blockade of CTLA-4 and PD-1 reduced the fungal load in the lungs and fungal dissemination to the liver and spleen and decreased the size of pulmonary lesions, resulting in increased survival of mice. Compared with PBS-treated infected mice, significantly increased levels of many pro- and anti-inflammatory cytokines were observed in the lungs of α-CTLA-4-treated mice, but a drastic reduction in the liver was observed following PD-1 blockade. In the lungs of α-CPI and IgG-treated mice, there were no changes in the frequency of inflammatory leukocytes, but a significant reduction in the total number of these cells was observed. Compared with PBS-treated controls, α-CPI- and IgG-treated mice exhibited reduced pulmonary infiltration of several myeloid cell subpopulations and decreased expression of costimulatory molecules. In addition, a decreased number of CD4+ and CD8+ T cells but sustained numbers of Th1, Th2, and Th17 T cells were detected. An expressive reduction in several Treg subpopulations and their maturation and suppressive molecules, in addition to reduced numbers of Treg, TCD4+, and TCD8+ cells expressing costimulatory and coinhibitory molecules of immunity, were also detected. The novel cellular and humoral profiles established in the lungs of α-CTLA-4 and α-PD-1-treated mice but not in control IgG-treated mice were more efficient at controlling fungal growth and dissemination without causing increased tissue pathology due to excessive inflammation. This is the first study demonstrating the efficacy of CPI blockade in the treatment of pulmonary PCM, and further studies combining the use of immunotherapy with antifungal drugs are encouraged.

Comparative investigations into the growth details of Histoplasma capsulatum var farciminosum on four different agar media.

Epizootic equine lymphangitis (EEL) is a chronic fungal disease that affects equids. The causative agent is a dimorphic fungus called Histoplasma capsulatum var farciminosum. H. capsulatum var farciminosum field strain 7 (D 2878/2023) isolated from the eye socket of an EEL Ethiopian horse was sub-cultured on 4 different solid media and incubated at 26°C and 37°C for 6 weeks. Details of growth morphology were recorded and shown in images during 6 weeks of incubation. H. capsulatum var farciminosum grew best at 26°C on all 4 agars, but only on sheep blood agar at 37°C as small, white dry colonies.

Mycetoma case series in Somalia.

Mycetoma is a suppurative chronic bacterial or fungal disease inoculated into the body by minor trauma which may penetrate from subcutaneous tissue to bone. Although the lower extremities are most commonly affected, rare forms can also be seen from time to time. The diagnostic triad of swelling in the affected area, multiple sinus formation, and purulent discharge with grains are typical. Definitive diagnosis is made by isolation of the causative pathogen, radiologic imaging, and histopathologic examination. Antifungal and antibacterial options are applied together with surgery. Our aim in this case series is to report and analyze 10 rare cases of mycetoma.

Diagnostic Laboratory Features and Performance of an Aspergillus IgG Lateral Flow Assay in a Chronic Pulmonary Aspergillosis Cohort.

Chronic pulmonary aspergillosis (CPA) is a chronic and progressive fungal disease with high morbidity and mortality. Avoiding diagnostic delay and misdiagnosis are concerns for CPA patients. However, diagnostic practice is poorly evaluated, especially in resource-constrained areas where Aspergillus antibody testing tools are lacking. This study aimed to investigate the diagnostic laboratory findings in a retrospective CPA cohort and to evaluate the performance of a novel Aspergillus IgG lateral flow assay (LFA; Era Biology, Tianjin, China). During January 2016 and December 2021, suspected CPA patients were screened at the Center for Infectious Diseases at Huashan Hospital. A total of 126 CPA patients were enrolled. Aspergillus IgG was positive in 72.1% with chronic cavitary pulmonary aspergillosis, 75.0% with chronic necrotizing pulmonary aspergillosis, 41.7% with simple aspergilloma, and 30.3% with Aspergillus nodule(s). The cavitary CPA subtypes had significantly higher levels of Aspergillus IgG. Aspergillus IgG was negative in 52 patients, who were finally diagnosed by histopathology, respiratory culture, and metagenomic next-generation sequencing (mNGS). Sputum culture was positive in 39.3% (42/107) of patients and Aspergillus fumigatus was the most common species (69.0%, 29/42). For CPA cohort versus controls, the sensitivity and specificity of the LFA were 55.6% and 92.7%, respectively. In a subgroup analysis, the LFA was highly sensitive for A. fumigatus-associated chronic cavitary pulmonary aspergillosis (CCPA; 96.2%, 26/27). Given the complexity of the disease, a combination of serological and non-serological tests should be considered to avoid misdiagnosis of CPA. The novel LFA has a satisfactory performance and allows earlier screening and diagnosis of CPA patients. IMPORTANCE There are concerns on avoiding diagnostic delay and misdiagnosis for chronic pulmonary aspergillosis due to its high morbidity and mortality. A proportion of CPA patients test negative for Aspergillus IgG. An optimal diagnostic strategy for CPA requires in-depth investigation based on real-world diagnostic practice, which has been rarely discussed. We summarized the clinical and diagnostic laboratory findings of 126 CPA patients with various CPA subtypes. Aspergillus IgG was the most sensitive test for diagnosing CPA. However, it was negative in 52 patients, who were finally diagnosed by non-serological tests, including biopsy, respiratory culture, and metagenomic next-generation sequencing. We also evaluated a novel Aspergillus IgG lateral flow assay, which showed a satisfactory performance in cavitary CPA patients and was highly specific to Aspergillus fumigatus. This study gives a full picture of the diagnostic practice for CPA patients in Chinese context and calls for early diagnosis of CPA with combined approaches.

Hypoxia inducible-factor 1 alpha regulates neutrophil recruitment during fungal-elicited granulomatous inflammation.

Chronic pulmonary aspergillosis (CPA) is a devastating disease with increasing prevalence worldwide. The characteristic granulomatous-like inflammation poses as the major setback to effective antifungal therapies by limiting drug access to fungi. These inflammatory lung structures are reported to be severely hypoxic; nevertheless, the underlying mechanisms whereby these processes contribute to fungal persistence remain largely unknown. Hypoxia-inducible factor 1 alpha (HIF-1α), besides being the major cellular response regulator to hypoxia, is a known central immune modulator. Here, we used a model of Aspergillus fumigatus airway infection in myeloid-restricted HIF-1α knock-out (mHif1α-/- ) mice to replicate the complex structures resembling fungal granulomas and evaluate the contribution of HIF-1α to antifungal immunity and disease development. We found that fungal-elicited granulomas in mHif1α-/- mice had significantly smaller areas, along with extensive hyphal growth and increased lung fungal burden. This phenotype was associated with defective neutrophil recruitment and an increased neutrophil death, therefore highlighting a central role for HIF-1α-mediated regulation of neutrophil function in the pathogenesis of chronic fungal infection. These results hold the promise of an improved capacity to manage the progression of chronic fungal disease and open new avenues for additional therapeutic targets and niches of intervention.

S5.1b Antifungal r esistance

S5.1 Antifungal resistance, September 22, 2022, 3:00 PM - 4:30 PMResistance to clinical antimycotics in Aspergillus fumigatus has become an increasing threat in healthcare worldwide over the past two decades. Factors that contribute to this continuing trend are manifold, among others resistance emerge in environmental fungi through selection pressure due to fungicides widely used in agriculture and farming, resistant clones are diffused around the world through global travel and shipping routes, as well as prophylactic and long-term administration of antifungal agents in patients with chronic fungal disease creating selection pressure.Physicians face particular challenges in their patients with invasive aspergillosis, with emerging resistance adding another layer of therapeutic complexity. We are beginning to gain an understanding of the clinical implications of the different patterns of resistance. First international studies have shown that resistance of A. fumigatus to clinical antifungal agents significantly hampers the successful treatment of patients.This presentation aims to highlight the difficulties associated with antifungal resistance in A. fumigatus with a focus on hematological oncological patients.

Experience of Isavuconazole as a Salvage Therapy in Chronic Pulmonary Fungal Disease.

Background: Instances of resistant fungal infection are rising in pulmonary disease, with limited therapeutic options. Therapeutic drug monitoring of azole antifungals has been necessary to ensure safety and efficacy but is considered unnecessary for the newest triazole isavuconazole. Aims: To characterise the prevalence of isavuconazole resistance and use in a tertiary respiratory centre. Methods: A retrospective observational analysis (2016–2021) of adult respiratory patients analysing fungal culture, therapeutic drug monitoring, and outcome post-isavuconazole therapy. Results: During the study period, isavuconazole susceptibility testing was performed on 26 Aspergillus spp. isolates. A total of 80.8% of A. fumigatus isolates had isavuconazole (MIC > 1 mg/L, and 73.0% > 2 mg/L) with a good correlation to voriconazole MIC (r = 0.7, p = 0.0002). A total of 54 patients underwent isavuconazole therapy during the study period (median duration 234 days (IQR: 24–499)). A total of 67% of patients tolerated isavuconazole, despite prior azole toxicity in 61.8%, with increased age (rpb = 0.31; p = 0.021) and male sex (φc = 0.30; p = 0.027) being associated with toxicity. A total of 132 isavuconazole levels were performed with 94.8% > 1 mg/L and 72% > 2 mg/L. Dose change from manufacturer’s recommendation was, however, required in 9.3% to achieve a concentration of >2 mg/L. Conclusion: We describe the use of isavuconazole as a salvage therapy in a chronic pulmonary fungal disease setting with a high prevalence of azole resistance. Therapeutic concentrations at standard dosing were high; however, results reinforce antifungal stewardship for optimization.

High-Frequency Direct Detection of Triazole Resistance in Aspergillus fumigatus from Patients with Chronic Pulmonary Fungal Diseases in India.

Aspergillosis due to azole-resistant Aspergillus fumigatus is a worldwide problem with major therapeutic implications. In patients with invasive aspergillosis, a low yield of fungal cultures results in underestimation of azole resistance. To detect azole resistance in A. fumigatus, we applied the AsperGenius® Resistance multiplex real-time polymerase chain reaction (PCR) assay to detect TR34/L98H, and TR46/T289A/Y121F mutations and the AsperGenius® G54/M220 RUO PCR assay to detect G54/M220 mutations directly in bronchoalveolar lavage (BAL) samples of 160 patients with chronic respiratory diseases in Delhi, India. Only 23% of samples were culture-positive compared to 83% positivity by A. fumigatus species PCR highlighting concerns about the low yield of cultures. Notably, 25% of BAL samples (33/160 patients) had azole resistance-associated mutation by direct detection using PCR assay. Detection of resistance-associated mutations was found mainly in 59% and 43% patients with chronic pulmonary aspergillosis (CPA) and allergic bronchopulmonary aspergillosis (ABPA), respectively. Overall, a G54 mutation, conferring itraconazole resistance, was the predominant finding in 87.5% and 67% of patients with CPA and ABPA, respectively. In culture-negative, PCR-positive samples, we detected azole-resistant mutations in 34% of BAL samples. Azole resistance in chronic Aspergillus diseases remains undiagnosed, warranting standardization of respiratory culture and inclusion of rapid techniques to detect resistance markers directly in respiratory samples.

Pneumonia e leptomeningite criptocócica em felino: relato de caso

A criptococose é uma doença fúngica infecciosa, tegumentar e/ou sistêmica, crônica, de distribuição global, causada por levedura sa­próbia do gênero Cryptococcus que pode infectar humanos, animais silvestres e mamíferos domésticos, especialmente felinos domésticos. Duas espécies estão mais diretamente envolvidas com a doença: o Cryptococcus neoformans e o Cryptococus gattii, porém pacientes imunocomprometidos têm, como principal causador, o Cryptococcus neoformans. Todavia, O Cryptococcus gattii, além de afetar hospedei­ros imunossuprimidos, também pode causar a doença em indivíduos imunocompetentes. Este relato apresenta os achados clínicos e o diagnóstico firmado com o exame histopatológico de um caso de pneumonia e leptomeningite criptocócica em um felino, macho, sem raça definida, de cinco anos de idade, atendido no Hospital Veterinário “Dr. Vicente Borelli” – do Centro Universitário da Fundação de Ensino Octávio Bastos (Unifeob).

Climate change could threaten cocoa production: Effects of 2015-16 El Niño-related drought on cocoa agroforests in Bahia, Brazil

Climate models predict a possible increase in the frequency of strong climate events such as El Niño-Southern Oscillation (ENSO), which in parts of the tropics are the cause of exceptional droughts, these threaten global food production. Agroforestry systems are often suggested as promising diversification options to increase farmers' resilience to extreme climatic events. In the Northeastern state of Bahia, where most Brazilian cocoa is grown in wildlife-friendly agroforests, ENSOs cause severe droughts which negatively affect forest and agriculture. Cocoa (Theobroma cacao) is described as being sensitive to drought but there are no field-studies of the effect of ENSO-related drought on adult cocoa trees in the America's; there is one study of an experimentally-imposed drought in Indonesia which resulted in 10 to 46% yield loss. In our study, in randomly chosen farms in Bahia, Brazil, we measured the effect of the 2015–16 severe ENSO, which caused an unprecedented drought in cocoa agroforests. We show that drought caused high cocoa tree mortality (15%) and severely decreased cocoa yield (89%); the drought also increased infection rate of the chronic fungal disease witches' broom (Moniliophthora perniciosa). Ours findings showed that Brazilian cocoa agroforests are at risk and that increasing frequency of strong droughts are likely to cause decreased cocoa yields in the coming decades. Furthermore, because cocoa, like many crops, is grown somewhat beyond its climatic limits, it and other crops could be the 'canaries in the coalmine' warning of forthcoming major drought effects on semi-natural and natural vegetation.

A review of the most effective medicinal plants for dermatophytosis in traditional medicine

Fungi can evade the immune system via different processes, including recombination, mitosis, and expression of genes involved in oxidative stress responses. These processes can lead to chronic fungal diseases. Despite the growth of health care facilities, the incidence rate of fungal infections is still considerably high. Dermatophytes represent the main cause of cutaneous diseases. Dermatophytes attack keratinized tissues, such as nail, hair, and stratum corneum, due of their gravitation towards keratin, which leads to dermatophytosis. Medicinal plants have long been used to treat different diseases, and in the recent years, use of plant-based products to fight fungal, bacterial, and parasitic infections have attracted extensive attention. This is because the use of medicinal plants has many advantages, such as decreased costs and fewer side effects. This review article was conducted to report medicinal plants with anti-dermatophytosis properties. Seventy-six articles were retrieved from databases Google Scholar, PubMed, ScienceDirect, and Scopus. After exclusion of duplicate and irrelevant articles, 54 articles were selected. Of the remaining articles, 23 articles were screened and included in this study. According to the findings, Azadirachta indica, Capparis spinosa, Anagallisarvensis, Juglans regia, Inula viscosa, Phagnalon rupestre, Plumbago europaea, Ruscus aculeatus, Ruta chalepensis, Salvia fruticosa, Artemisia judaica, Ballota undulate, Cleome amblyocarpa, Peganum harmala, Teucrium polium, Aegle marmelos, Artemisia sieberi, Cuminum cyminum, Foeniculum vulgare, Heracleum persicum, Mentha spicata, Nigella sativa, and Rosmarinus officinalis are the most effective plants against dermatophytes which have been identified to date.

Aspergillus fumigatus viability drives allergic responses to inhaled conidia

BackgroundAspergillus fumigatus–induced allergic airway disease has been shown to involve conidial germination in vivo, but the immunological mechanisms remain uncharacterized. ObjectiveA subchronic murine exposure model was used to examine the immunological mediators that are regulated in response to either culturable or nonculturable A fumigatus conidia. MethodsFemale B6C3F1/N mice were repeatedly dosed via inhalation with 1 × 105 viable or heat-inactivated conidia (HIC), twice per week for 13 weeks (26 exposures). Control mice inhaled high-efficiency particulate arrestor–filtered air. The influence of A fumigatus conidial germination on the pulmonary immunopathological outcomes was evaluated by flow cytometry analysis of cellular infiltration in the airways, assessment of lung messenger RNA expression, quantitative proteomics, and histopathology of whole lung tissue. ResultsRepeated inhalation of viable conidia, but not HIC, resulted in allergic inflammation marked by vascular remodeling, extensive eosinophilia, and accumulation of alternatively activated macrophages (AAMs) in the murine airways. More specifically, mice that inhaled viable conidia resulted in a mixed TH1 and TH2 (IL-13) cytokine response. Recruitment of eosinophils corresponded with increased Ccl11 transcripts. Furthermore, genes associated with M2 or alternatively activated macrophage polarization (eg, Arg1, Chil3, and Retnla) were significantly up-regulated in viable A fumigatus–exposed mice. In mice inhaling HIC, CD4+ T cells expressing IFN-γ (TH1) dominated the lymphocytic infiltration. Quantitative proteomics of the lung revealed metabolic reprogramming accompanied by mitochondrial dysfunction and endoplasmic reticulum stress stimulated by oxidative stress from repetitive microbial insult. ConclusionOur studies demonstrate that A fumigatus conidial viability in vivo is critical to the immunopathological presentation of chronic fungal allergic disease.

An Estimate of Severe and Chronic Fungal Diseases in the Republic of Kazakhstan.

Our work aimed to generate a preliminary estimation of severe and chronic fungal diseases in the Republic of Kazakhstan with a model proposed by LIFE (Leading International Fungal Education). Calculations were carried out on data from 2015. Published results of studies of mycoses in Kazakhstan were identified; in the absence of national data from the scientific literature, the frequency of life-threatening and serious mycoses in defined groups of patients at risk from other countries were taken into account. We also used analogous estimations of mycoses in the Russian Federation. We estimate that 300,824 patients (1.7% of the population) were affected by severe and chronic mycotic diseases. There were an estimated 15,172 cases of acute mycoses, notably tinea capitis in children (11,847), Pneumocystis pneumonia and invasive candidiasis, and 285,652 of chronic fungal diseases. The most frequent were chronic recurrent vulvovaginal candidiasis (273,258 cases) and chronic pulmonary aspergillosis (6231). There is uncertainty about the prevalence of asthma in adults; the official number is 12,478 patients, but a prevalence estimate of 1.47% from a WHO consortium yields a prevalence of ~170,000 affected. We have used the official figures to generate the prevalence of fungal asthma, but it is likely to be a significant underestimate. Conclusion: Results of investigation indicate significant prevalence of severe and chronic mycoses in the Republic of Kazakhstan.

Onychomycosis and Chronic Fungal Disease: Exploiting a Commensal Disguise to Stage a Covert Invasion.

Onychomycosis is a chronic fungal infection that is recalcitrant to treatment and often results in relapse. New evidence suggests that disease prognosis may be linked to pathogens manipulating host immune responses. Therefore, individuals with specific mutations, including those affecting pattern recognition receptors or the interleukin (IL)-17 and IL-22 pathways, may be more susceptible to infection. Moreover, it is recommended that those with a family history of immune mutations or predisposition to fungal disease be treated aggressively for onychomycosis prior to symptom progression. In addition, incorporating genetic testing and new investigational therapy such as IL-33 and interferon-γ may improve treatment outcome.

Anti–PD-1 Antibody Treatment Promotes Clearance of Persistent Cryptococcal Lung Infection in Mice

Activation of immunomodulatory pathways in response to invasive fungi can impair clearance and promote persistent infections. The programmed cell death protein-1 (PD-1) signaling pathway inhibits immune effector responses against tumors, and immune checkpoint inhibitors that block this pathway are being increasingly used as cancer therapy. The objective of this study was to investigate whether this pathway contributes to persistent fungal infection and to determine whether anti-PD-1 Ab treatment improves fungal clearance. Studies were performed using C57BL/6 mice infected with a moderately virulent strain of Cryptococcus neoformans (52D), which resulted in prolonged elevations in fungal burden and histopathologic evidence of chronic lung inflammation. Persistent infection was associated with increased and sustained expression of PD-1 on lung lymphocytes, including a mixed population of CD4+ T cells. In parallel, expression of the PD-1 ligands, PD-1 ligands 1 and 2, was similarly upregulated on specific subsets of resident and recruited lung dendritic cells and macrophages. Treatment of persistently infected mice for 4 wk by repetitive administration of neutralizing anti-PD-1 Ab significantly improved pulmonary fungal clearance. Treatment was well tolerated without evidence of morbidity. Immunophenotyping revealed that anti-PD-1 Ab treatment did not alter immune effector cell numbers or myeloid cell activation. Treatment did reduce gene expression of IL-5 and IL-10 by lung leukocytes and promoted sustained upregulation of OX40 by Th1 and Th17 cells. Collectively, this study demonstrates that PD-1 signaling promotes persistent cryptococcal lung infection and identifies this pathway as a potential target for novel immune-based treatments of chronic fungal disease.

Invasive and chronic fungal lung infections

Fungi are increasingly recognized as a cause of respiratory infection, particularly affecting individuals with either immune deficiency or localised lung destruction. The normal human host response effectively controls airborne fungi, but specific polymorphisms are associated with increased risk of developing fungal lung infection. Invasive fungal disease (IFD) is associated with neutropenia and haematological stem cell transplants. They are difficult to diagnose with certainty though the use of cross-sectional imaging and biomarkers has allowed targeted patient treatment. Mortality rates, though improving with antifungal therapy, remain unacceptably high. Chronic pulmonary fungal disease is associated with chronic respiratory disorders and is also difficult to diagnose with certainty. Treatment is chronic and often poorly tolerated, and even when successful unable to reverse existing lung damage. Further research is required to improve both diagnostics and therapy to improve outcomes in these infectious diseases.