Biology subjects

Meya, D. B.

Publications and source records attributed to Meya, D. B..

5 recordsLinked to original sources

bioRxiv2025

Global proteomic analysis of Cryptococcus neoformans clinical strains reveals significant differences between latent and lethal infection

To predict the outcomes of disseminated fungal disease, a deeper understanding of host-pathogen interactions at the site of infection is needed to identify targets for clinical intervention and diagnostic development. Cryptococcus neoformans is the causative agent of cryptococcosis, the largest infectious killer of individuals living with HIV. Cryptococcal infection begins in the lungs, with loss of immunological control leading to disseminated central nervous system disease and death. Using advanced mass spectrometry-based proteomic techniques, in vivo infection models, and patient-derived clinical strains, we explored the proteomic profiles of C. neoformans infections related to differences in strain virulence. Our findings reveal that non-lethal latent infection produces a proteomic response that differs significantly from the response caused by lethal infections, and that the proteomic profiles of typical and hypervirulent infections are markedly similar despite differences in time-to-death. Overall, the mouse pulmonary proteomic response in latent infection is defined by enrichment of proteins and pathways involved in extracellular matrix organization, cell adhesion, and structural changes, while the lethal infection is dominated by host-defense, translation, and metabolic processes. These results provide clinically relevant information on how infections caused by different Cryptococcus strains may produce significantly different outcomes. We also identified abundant fungal proteins that could be future drug targets in latent and lethal cryptococcal infection. IMPORTANCECryptococcus neoformans is a fungal pathogen that causes substantial morbidity and mortality in immunocompromised individuals. The initial infection begins in the lungs after exposure to inhaled spores after which local immune cells respond by either killing or containing the fungal cells. Immunosuppression weakens the immune system and allows fungal cells in the lungs to escape through the circulatory system and invade the central nervous system and cause fatal disease. However, differences between fungal strains influence the severity of disease manifestation. Our group has previously described genetic differences that contribute to strain-specific disease manifestations. In this study, we expanded our analysis to investigate the proteomic differences between strains of C. neoformans to identify candidate proteins and pathways that contribute to disease manifestation. We found that latent infection differs significantly from lethal disease from both the host and pathogen proteomic perspectives and have identified several fungal protein targets for future study.

microbiology↗

bioRxiv2024

Pulmonary granuloma formation during latent Cryptococcus neoformans infection in C3HeB/FeJ mice involves progression through three immunological phases

Cryptococcus neoformans is a fungal pathogen that can cause lethal disease in immunocompromised patients. Immunocompetent host immune responses, such as formation of pulmonary granulomas, control the infection and prevent disseminated disease. Little is known about the immunological conditions establishing the latent infection granuloma in the lungs. To investigate this, we performed an analysis of pulmonary immune cell populations, cytokine changes, and granuloma formation during infection with a latent disease-causing clinical isolate in C3HeB/FeJ mice over 360 days. We found that latently infected mice progress through three phases of granuloma formation where different immune profiles dominate: an early phase characterized by eosinophilia, high IL-4/IL-13, and C. neoformans proliferation in the lungs; an intermediate phase characterized by multinucleated giant cell formation, high IL-1/IFN{gamma}, granuloma expansion, and increased blood antigen levels; and a late phase characterized by a significant expansion of T cells, granuloma condensation, and decreases in lung fungal burden and blood antigen levels. These findings highlight a complex series of immune changes that occur during the establishment of granulomas that control C. neoformans in the lungs and lay the foundation for studies to identify critical beneficial immune responses to Cryptococcus infections. IMPORTANCECryptococcus neoformans is a fungal pathogen that disseminates from the lungs to the brain to cause fatal disease. Latent C. neoformans infection in the lungs is controlled by organized collections of immune cells called granulomas. The formation and structure of Cryptococcus granulomas are poorly understood due to inconsistent human pathology results and disagreement between necrotic granuloma-forming rat models and non-necrotic granuloma-forming mouse models. To overcome this, we investigated granuloma formation during latent C. neoformans infection in the C3HeB/FeJ mouse strain which forms necrotic lung granulomas in response to other pathogens. We found that latent C. neoformans granuloma formation progresses through phases that we described as early, intermediate, and late with different immune response profiles and granulomatous characteristics. Ultimately, we show that C3HeB/FeJ mice latently infected with C. neoformans form non-necrotic granulomas and could provide a novel mouse model to investigate host immune response profiles.

microbiology↗

bioRxiv2019

B cell Compartmentalisation in Blood and Cerebrospinal Fluid of HIV- Infected Ugandans with Cryptococcal Meningitis

BackgroundActivated B cells modulate infection by differentiating into pathogen-specific antibody-producing effector plasmablasts/plasma cells, memory cells and immune regulatory B cells. In this context, the B cell phenotypes that infiltrate the central nervous system during HIV and cryptococcal meningitis co-infection are ill defined.\n\nMethodsWe characterized clinical parameters, mortality and B cell phenotypes in blood and CSF by flow cytometry in HIV-infected adults with cryptococcal (n=31), and non-cryptococcal meningitis (n=12), and heathy control subjects with neither infection (n=10).\n\nResultsActivation of circulating B cells (CD21low) was significantly higher in blood of subjects with HIV infection compared with healthy controls, and greater yet in matched CSF B cells (p<0.001). Among B cell subsets, elevated frequencies of memory and plasmablasts/plasma cells most clearly distinguished the CSF from blood compartments. With cryptococcal meningitis, lower frequencies of expression of the regulatory protein PD-1 on plasmablasts/plasma cells in blood (median 7%) at presentation was associated with significantly decreased 28-day survival (29% (4/14 subjects)), whereas higher PD-1 expression (median 46%) characterized subjects with higher survival (88% (14/16 subjects)).\n\nConclusionWith HIV infection, B cell differentiation and regulatory markers are discrete elements of the circulating and CSF compartments with clinical implications for cryptococcal disease outcome, potentially due to their effects on the fungus and other local immune cells.

immunology↗

bioRxiv2019

Identification of pathogen genomic differences that impact human immune response and disease during Cryptococcus neoformans infection

Patient outcomes during infection are due to a complex interplay between the quality of medical care, host immunity factors, and the infecting pathogens characteristics. To probe the influence of pathogen genotype on human immune response and disease, we examined Cryptococcus neoformans isolates collected during the Cryptococcal Optimal ART Timing (COAT) trial in Uganda. We measured human participants immunologic phenotypes, meningitis disease parameters, and survival. We compared this clinical data to whole genome sequences from 38 C. neoformans isolates of the most frequently observed sequence type (ST) ST93 in our Ugandan participant population, and an additional 18 strains from 9 other sequence types representing the known genetic diversity within the Ugandan Cryptococcus clinical isolates. We focused our analyses on 652 polymorphisms that: were variable among the ST93 genomes, were not in centromeres or extreme telomeres, and were predicted to have a fitness effect. Logistic regression and principal component analyses identified 40 candidate Cryptococcus genes and 3 hypothetical RNAs associated with human immunologic response or clinical parameters. We infected mice with 17 available KN99 gene deletion strains for these candidate genes and found that 35% (6/17) directly influenced murine survival. Four of the six gene deletions that impacted murine survival were novel. Such bedside-to-bench translational research provides important candidate genes for future studies on virulence-associated traits in human Cryptococcus infections.\n\nAuthor SummaryEven with the best available care, mortality rates in cryptococcal meningitis range from 20-60%. Disease is often due to infection by the fungus Cryptococcus neoformans and involves a complex interaction between the human host and the fungal pathogen. Although previous studies have suggested genetic differences in the pathogen impact human disease, it has proven quite difficult to identify the specific C. neoformans genes that impact the outcome of the human infection. Here, we take advantage of a Ugandan patient cohort infected with closely related C. neoformans strains to examine to role of pathogen genetic variants on several human disease characteristics. Using a pathogen whole genome sequencing approach, we showed that 40 C. neoformans genes are associated with human disease. Surprisingly, many of these genes are specific to Cryptococcus and have unknown functions. We also show deletion of these genes alters disease in a mouse model of infection, confirming their role in disease. These findings are particularly important because they are the first to identify C. neoformans genes associated with human cryptococcal meningitis and lay the foundation for future studies that may lead to new treatment strategies aimed at reducing patient mortality.

genetics↗

bioRxiv2019

Closely related Cryptococcus neoformans strains possess differential virulence both in humans and the mouse inhalation model

Cryptococcal meningitis (CM) causes high rates of HIV-related mortality, yet Cryptococcus factors influencing patient outcome are not well understood. Pathogen-specific traits, such as the strain genotype and degree of antigen shedding, are associated with clinical outcome but the underlying biology remains elusive. In this study, we examined factors determining disease outcome in HIV-infected cryptococcal meningitis patients infected with C. neoformans strains with the same multi-locus sequence type. Both patient mortality and survival were observed during infections with the same sequence type. Disease outcome did not correlate with underlying patient immune deficiencies. Patient mortality was associated with higher antigen levels, fungal burden in the CSF, and low CSF fungal clearance. Virulence of a subset of clinical strains with the same sequence type were analyzed using the mouse inhalation model of cryptococcosis. We showed a strong correlation between human and mouse mortality rates, demonstrating the mouse inhalation model recapitulates human infection. Similar to human infection, the ability to multiply in vivo, demonstrated by high fungal burden in the lung and brain tissues, was associated with mouse mortality. Mortality rate was not associated with single C. neoformans virulence factors in vitro or in vivo; rather, a trend in mortality rate correlated with a suite of traits. These observations show that genotype similarities between C. neoformans strains do not necessarily translate into similar virulence either in the mouse model or in human patients. In addition, our results show that in vitro assays do not fully reproduce in vivo conditions that influence C. neoformans virulence.

microbiology↗