An inherent T cell deficit in healthy males to C. neoformans infection may begin to explain the sex susceptibility in incidence of cryptococcosis

COVID-19 associated with cryptococcosis: a scoping review

Background

There is growing evidence of fungal infections associated with COVID-19. The development of cryptococcosis in these patients has been infrequently reported. However, it can be life-threatening.

Objective

To identify cases of COVID-19 patients who developed cryptococcosis and to compare baseline characteristics and management between those who survived and those who died.

Methods

We conducted a scoping review using PubMed, Scopus, Web of Science, and Embase to identify studies that reported patients with COVID-19 and cryptococcosis. No language restriction was applied. Single case reports, case series, and original articles were included. It is important to note that 'n' refers to the total number of individuals with the specified variable.

Results

A total of 58 studies were included. Among these studies, 51 included individual patient data, detailing information on a total of 65 patients, whereas eight studies reported the proportion of cryptococcosis in COVID-19 patients. One study provided both individual and aggregate case information. From individual patient data, the majority were male (73.9%; n = 48) with a median age of 60 years (range: 53-70). Severe COVID-19 and multiple comorbidities, led by arterial hypertension and diabetes mellitus, were frequently reported, but few had classic immunosuppression factors. On the other hand, HIV status, either negative or positive, was reported in just over half of the patients (61.5%; n = 40). Most were admitted to the intensive care unit (ICU) (58.5%; n = 31), received mechanical ventilation (MV) (50.0%; n = 26), and developed disseminated cryptococcosis (55.4%; n = 36). Secondary infection, mainly bacterial, was reported in 19 patients (29.2%). Mortality was 47.7% (n = 31). Of the studies that reported the proportion of cryptococcosis in COVID-19 cases, the majority were descriptive studies published as conference abstracts.

Conclusion

Cryptococcosis in COVID-19 patients has been reported more frequently. However, it is still not as common as other fungal infections associated with COVID-19. Few patients have some classic immunosuppression factors. The factors associated with mortality were male sex, age, ICU admission, MV, secondary infections, and lymphopenia.

[Sex in infectious diseases-How sex differences influence the immune response to infections]

The humoral and cellular immune responses to antigen stimulation, vaccinations and infections differ between women and men. Genetic, epigenetic and hormonal factors contribute to the sex-specific immunity. The expression of genes on the X‑chromosome and the effect of sex hormones substantially influence the immune defence against infections. Females show stronger cellular and humoral immune responses to infections than males, but the enhanced immune response often leads to aberrant inflammatory reactions and autoimmune diseases. Men are principally more prone to bacterial, viral and fungal infections and more often show severe disease courses. In contrast, a more reactive female immune system results in significantly more adverse reactions to vaccinations. In order to be able to better identify the multiple sex-specific that have an influence on the immune system, sex-specific differences should be investigated in a differentiated way. The better understanding of the sex-specific differences in the immune response will have a long-term influence on the prevention, diagnostics and treatment of infectious diseases, and will ultimately contribute to improving healthcare of both women and men.

Adaptive immunology of Cryptococcus neoformans infections-an update

The fungal genus Cryptococcus comprises a group of pathogens with considerable phenotypic and genotypic diversity that can lead to cryptococcosis in both healthy and immunocompromised individuals. With the emergence of the HIV pandemic, cryptococcosis, mainly meningoencephalitis, afflicts HIV-infected patients with severe dysfunction of T cells. It has also been reported in recipients of solid organ transplantation and in patients with autoimmune diseases who take immunosuppressive agents long-term, as well as in those with unidentified immunodeficiency. The clinical outcome of the disease is primarily determined by the immune response resulting from the interplay between the host immune system and the pathogen. Most human infections are caused by Cryptococcus neoformans, and nearly all immunological studies have focused on C. neoformans. This review provides an updated understanding of the role of adaptive immunity during infection with C. neoformans in human and animal models over the past half-decade.

The Pathological Activation of Microglia Is Modulated by Sexually Dimorphic Pathways

Microglia are the primary immunocompetent cells of the central nervous system (CNS). Their ability to survey, assess and respond to perturbations in their local environment is critical in their role of maintaining CNS homeostasis in health and disease. Microglia also have the capability of functioning in a heterogeneous manner depending on the nature of their local cues, as they can become activated on a spectrum from pro-inflammatory neurotoxic responses to anti-inflammatory protective responses. This review seeks to define the developmental and environmental cues that support microglial polarization towards these phenotypes, as well as discuss sexually dimorphic factors that can influence this process. Further, we describe a variety of CNS disorders including autoimmune disease, infection, and cancer that demonstrate disparities in disease severity or diagnosis rates between males and females, and posit that microglial sexual dimorphism underlies these differences. Understanding the mechanism behind differential CNS disease outcomes between men and women is crucial in the development of more effective targeted therapies.

Trend of pediatric cryptococcosis in a tertiary care centre and review of literature

PURPOSE

Cryptococcosis is one of the most significant systemic fungal infections worldwide. Epidemiological data for pediatric cryptococcosis is very limited. Therefore, we planned this study to determine the burden of cryptococcosis in the pediatric population at our tertiary care center and performed review of literature.

MATERIAL AND METHODS

In this retrospective study, all the patients less than 18 years of age were diagnosed with cryptococcosis, from January 2015-June 2021 were included. Demographic, clinical, and laboratory details of all the patients were noted. Furthermore, PubMed and MedLine databases were comprehensively searched for cases of pediatric cryptococcosis till June 2021.

RESULTS

Of the total 5420 samples from suspected cryptococcosis cases processed at mycology laboratory, a total of 21 episodes of cryptococcosis (0.39%) were identified in 15 pediatric patients. The majority of the patients were apparently immunocompetent (10/15). Central nervous system (CNS) cryptococcosis was the most common presentation, followed by disseminated disease. All the isolates were identified as Cryptococcus neoformans (formerly referred to as C. neoformans var grubii), except one that was identified as Papiliotrema laurentii (formerly referred to as Cryptococcus laurentii). A standard treatment regimen inclusive of induction and maintenance therapy was provided in only five patients. The literature review revealed a total of 125 studies describing 1134 cases, of which 76.4% are reported from outside Asia, the majority (65.7%) restricted to CNS with C. neoformans as the commonest species. The management profile divulged a significantly higher use of standard drug regimen in Asia as compared to the rest of the world. Mortality of 13.32% was noted worldwide.

CONCLUSION

To the best of our knowledge, this is the first clinico-epidemiological study of pediatric cryptococcosis from India and the largest retrospective study worldwide. The rising incidence among immunocompetent individuals, especially in Asia, is a matter of concern. Clinical suspicion and early diagnosis are the cornerstones for the management of cases.

Let's talk about Sex Characteristics - as a Risk Factor for Invasive Fungal Diseases

Biological sex, which comprises differences in host sex hormone homeostasis and immune responses, can have a substantial impact on the epidemiology of infectious diseases. Comprehensive data on sex distributions in invasive fungal diseases (IFDs) is lacking. In this review we performed a literature search of in vitro/animal studies, clinical studies, systematic reviews, and meta-analyses of invasive fungal infections. Females represented 51.2% of invasive candidiasis cases, mostly matching the proportions of females among the general population in the United States and Europe (>51%). In contrast, other IFDs were overrepresented in males, including invasive aspergillosis (51% males), mucormycosis (60%), cryptococcosis (74%), coccidioidomycosis (70%), histoplasmosis (61%), and blastomycosis (66%). Behavioral variations, as well as differences related to biological sex, may only in part explain these findings. Further investigations concerning the association between biological sex/gender and the pathogenesis of IFDs is warranted.

Influence of sex hormones on the immune response to leishmaniasis

The differences in morbidity and mortality patterns and life expectancy between the sexes are well established in different infectious and parasitic conditions, such as in leishmaniases, in which biological, genetic, sexual and hormonal variations can modulate the immune response indicating greater infectivity, prevalence and clinical severity in men. In this regard, in seeking the understanding of factors related to protection and susceptibility to infection, this review aimed to discuss the influence of sex hormones on the immune response to leishmaniases. In the literature, sex hormone variations promote differences in the innate, humoral and cell-mediated immune response, leading to greater susceptibility, mortality and complications in males. Epidemiological estimates confirm these results, showing a predominance of the disease, in its different clinical forms, in men and suggesting that sexual variations influence immunomodulatory mechanisms since the prevalence of cases comprises the post-puberty and adulthood period. In this perspective, the action of sex hormones has been investigated in different clinical models, highlighting the potential of testosterone in immunosuppression, given its association with greater susceptibility and poor control of parasite load and the induction of cell apoptosis and attenuation of pro-inflammatory signalling pathways. Therefore, hormonal variations influence the immune response among males and females against leishmaniases, in which androgens may present immunosuppressive potential, while steroids present immunomodulatory characteristics.

Associations between Cryptococcus Genotypes, Phenotypes, and Clinical Parameters of Human Disease: A Review

The genus Cryptococcus contains two primary species complexes that are significant opportunistic human fungal pathogens: C. neoformans and C. gattii. In humans, cryptococcosis can manifest in many ways, but most often results in either pulmonary or central nervous system disease. Patients with cryptococcosis can display a variety of symptoms on a spectrum of severity because of the interaction between yeast and host. The bulk of our knowledge regarding Cryptococcus and the mechanisms of disease stem from in vitro experiments and in vivo animal models that make a fair attempt, but do not recapitulate the conditions inside the human host. To better understand the dynamics of initiation and progression in cryptococcal disease, it is important to study the genetic and phenotypic differences in the context of human infection to identify the human and fungal risk factors that contribute to pathogenesis and poor clinical outcomes. In this review, we summarize the current understanding of the different clinical presentations and health outcomes that are associated with pathogenicity and virulence of cryptococcal strains with respect to specific genotypes and phenotypes.

The Role of Testosterone and Gibberellic Acid in the Melanization of Cryptococcus neoformans

Cryptococcus neoformans, a spore-producing pathogenic yeast, affects immunocompromised individuals causing meningoencephalitis. Once C. neoformans is introduced via the respiratory tract, it is engulfed by macrophages and other phagocytes. One of C. neoformans's primary virulence factors is the pigment melanin, which is formed in the cell wall and protects the yeast against UV radiation and oxidizing agents produced by macrophages during phagocytosis. To better understand the observed sex bias (3:1; male:female) in C. neoformans infections, the phenotype of various virulence factors was determined in the presence of exogenous sex hormones. C. neoformans melanized faster in the presence of testosterone than it did in the presence of estradiol. Using a combination of RNA sequencing analysis and ELISA results, we identified a growth hormone, gibberellic acid (GA), produced in C. neoformans that was highly upregulated in the presence of testosterone. A variety of knockout strains of genes involved in the GA biosynthesis pathway showed significantly reduced melanization in the presence of testosterone. Additionally, inhibitors of GA also reduced melanization in the presence of testosterone. Thus, these data suggest that the gibberellic biosynthesis pathway is involved in melanization in C. neoformans, and the melanization difference observed in the presence of testosterone may be due to increased production of GA, which may partly explain the sex bias observed in C. neoformans infections.

The Effects of Androgens on T Cells: Clues to Female Predominance in Autoimmune Liver Diseases?

The immune system responds differently in women and in men. Generally speaking, adult females show stronger innate and adaptive immune responses than males. This results in lower risk of developing most of the infectious diseases and a better ability to clear viral infection in women (1–5). On the other hand, women are at increased risk of developing autoimmune diseases (AID) such as rheumatoid arthritis, multiple sclerosis (MS), systemic lupus erythematosus (SLE), Sjögren's syndrome, and the autoimmune liver diseases autoimmune hepatitis (AIH) and primary biliary cholangitis (PBC) (6). Factors contributing to the female sex bias in autoimmune diseases include environmental exposure, e.g., microbiome, behavior, and genetics including X chromosomal inactivation of genes. Several lines of evidence and clinical observations clearly indicate that sex hormones contribute significantly to disease pathogenesis, and the role of estrogen in autoimmune diseases has been extensively studied. In many of these diseases, including the autoimmune liver diseases, T cells are thought to play an important pathogenetic role. We will use this mini-review to focus on the effects of androgens on T cells and how the two major androgens, testosterone and dihydrotestosterone, potentially contribute to the pathogenesis of autoimmune liver diseases (AILD).

Pathogen and host genetics underpinning cryptococcal disease

Cryptococcosis is a severe fungal disease causing 220,000 cases of cryptococcal meningitis yearly. The etiological agents of cryptococcosis are taxonomically grouped into at least two species complexes belonging to the genus Cryptococcus. All of these yeasts are environmentally ubiquitous fungi (often found in soil, leaves and decaying wood, tree hollows, and associated with bird feces especially pigeon guano). Infection in a range of animals including humans begins following inhalation of spores or aerosolized yeasts. Recent advances provide fundamental insights into the factors from both the pathogen and its hosts which influence pathogenesis and disease. The complex interactions leading to disease in mammalian hosts have also updated from the availability of better genomic tools and datasets. In this review, we discuss recent genetic research on Cryptococcus, covering the epidemiology, ecology, and evolution of Cryptococcus pathogenic species. We also discuss the insights into the host immune response obtained from the latest genetic modified host models as well as insights from monogenic disorders in humans. Finally we highlight outstanding questions that can be answered in the near future using bioinformatics and genomic tools.

17-β-Estradiol increases macrophage activity through activation of the G-protein-coupled estrogen receptor and improves the response of female mice to Cryptococcus gattii

Cryptococcus gattii (Cg) is one of the agents of cryptococcosis, a severe systemic mycosis with a higher prevalence in men than women, but the influence of the female sex hormone, 17-β-estradiol (E2), on cryptococcosis remains unclear. Our study shows that female mice presented delayed mortality, increased neutrophil recruitment in bronchoalveolar lavage fluid, and reduced fungal load after 24 hr of infection compared to male and ovariectomised female mice (OVX). E2 replacement restored OVX female survival. Female macrophages have more efficient fungicidal activity, which was increased by E2 and reversed by the antagonist of G-protein-coupled oestrogen receptor (GPER), which negatively modulates PI3K activation. Furthermore, E2 induces a reduction in Cg cell diameter, cell charge, and antioxidant peroxidase activity. In conclusion, female mice present improved control of Cg infection, and GPER is important for E2 modulation of the female response.