An Infectomic approach to comprehend the immunopathogenesis of Cryptococcal meningitis in Blood Brain Barrier Endothelium.
In humans, Cryptococcus neoformans and Cryptococcus gattii species complexes are the leading cause of fungal meningitis globally. It is an invasive fungus that majorly causes infection of the CNS leading to fatal consequences in immunocompromised and apparently immunocompetent individuals. To establish CNS infection, Cryptococcus must breach the BBB, primarily comprised of specialized brain microvascular endothelial cells (BMECs), which is the prerequisite for Cryptococci to invade the brain. Our study aimed at understanding the intricate host pathogen interaction during the invasion of Cryptococcus into HBMECs instigating a cascade of immunopathogenic events within the host cell and the pathogen. By employing advanced dual RNASeq high throughput sequencing technology, we comprehensively evaluated the differential expression profile of virulence related genes across clinical and environmental isolates of Cryptococcus during their invasion into HBMECs. Additionally, we investigated the diverse immune signaling pathways activated by host BMECs in response to the invading Cryptococci within in vitro experimental conditions. Our findings demonstrated the functional enrichment of several critical Cryptococcal virulence genes primarily involved in developing strategic mechanisms to evade host immune responses and the various immune signaling pathways elicited by the HBMECs as a counter measure to the cryptococcal invasion. Notably, the interaction between Cryptococcus and HBMECs was characterized by remarkable alterations in the expression profiles of genes associated with diverse host cellular components. Moreover, our study unveiled the enrichment of specific pathways including histidine metabolism, ferroptosis, IL17 and Ras signaling pathways that offer potential molecular targets for antifungal therapy against Cryptococcal meningitis. Previous experimental studies have demonstrated unique expression profiles among different reference or mutant strains of clinical and environmental Cryptococcal isolates across various conditions. However, there is a significant gap in understanding how gene expression profiles with regard to various virulence attributes differ between environmental and clinical isolates of Cryptococcus while invading human BMECs. Our study represents an innovative approach adopted to understand the differential expression profile of environmental Cryptococcal isolates that lack prior exposure to the human host milieu in contrast to the clinical isolates and differences in their impacts on the BBB endothelium. In conclusion environmental Cryptococcus isolates are adequately competent in invading the human BBB endothelium to establish CNS infection compared to clinical isolates with comparable changes in the regulation of gene expression encoding virulence factors.