Assessing the role of SP140 in enhanced resistance to Cryptococcus neoformans

Project Abstract The HIV/AIDS associated fungal pathogen Cryptococcus neoformans (Cn) is responsible for 20% of global HIV-related mortality and has been designated on the World Health Organization Critical Fungal Patho- gens list. Cn is the causative agent of cryptococcal meningitis (CM), a severe infection of the central nervous

system that causes irreversible neurological damage and death. Mortality rates from CM are >30% depending upon global region. To reduce global mortality from CM, a greater understanding of host immune responses and better in vivo models are needed to produce clinically translatable findings. Cn is found ubiquitously in the

environment and inhalation of Cn spores leads to infection of the alveoli and deep pulmonary tissue. In immu- nocompetent individuals, Cn infection is contained within pulmonary granulomas leading to containment of Cn cells. Granulomas are formed through signaling between the innate and adaptive immune responses, specifi-

cally between macrophages and CD4+ T cells. Advanced HIV coinfection causes depletion of CD4+ T cells and disrupts the signaling needed to maintain granuloma structure. Granuloma breakdown leads to fungal es- cape and disseminated CM disease. Better understanding of granuloma formation and breakdown can lead to

the development of therapeutics to prevent dissemination in immunocompromised individuals. However, cur- rent in vivo models do not replicate human the necrotic Cn granulomas observed in humans. My preliminary data identified C3HeB/FeJ mice as producing Cn granulomas that better recapitulate necrotic granulomas in

humans. In addition, these mice have better survival when infected with Cn compared to C57Bl/6 (B6) mice. However, the mechanism and genes that drive this phenotype are unknown. Previous studies using Mycobac- terium tuberculosis (Tb) showed that deficiencies in the immune regulating gene Sp140 is involved in the

C3HeB/FeJ necrotic granuloma response against Tb. Therefore, my central hypothesis is that sp140-deficieny is responsible for the production of necrotic Cn granulomas and increased resistance against Cn. To test my hypothesis I propose the following Aims: Aim 1) Determine the role of sp140-deficiency in the immune re-

sponse against Cn by measuring differences in survival, fungal burden, Cn blood antigen level, cytokine abun- dances, and immune cell populations; Aim 2) Define the histological and transcriptional profiles of sp140-defi- cient Cn granulomas over time using microscopy and spatial transcriptomics, and determine the mechanisms

by which CD4+ T cell depletion leads to granuloma breakdown. These findings will expand our understanding of protective host immune responses against Cn, establish a method for modeling human-like Cn granulomas in mice, and provide insight into the mechanism of granuloma degradation during advanced HIV coinfection.