Modeling a human STAT4 mutation that predisposes to disseminated Coccidioidomycosis in mice

Abstract

Abstract Coccidioidomycosis is a common fungal respiratory disease caused by the fungus Coccidioides spp. fungi in Arizona and the central valley of California. Disseminated Coccidioidomycosis (DCM) occurs in 8% of identified cases, causing significant morbidity and mortality. DCM occurred in 3 generations of a family in Tucson, Arizona who all shared a heterozygous missense mutation (p.E626G) in STAT4. Transfection of STAT4 E626G in WT human cells showed dampened responses to STAT4-dependent cytokine gene induction, suggesting the mutation is a dominant negative. To understand the function of E626G mutation, we generated the homologous mutation in Stat4 in B6 mice. Mice carrying E626G were grossly normal with normal numbers of innate and adaptive immune cells in primary and secondary lymphoid organs. To examine the effect of E626G on susceptibility to Coccidioides infection, we infected mice with C. posadasii strain 1038 intranasally. After infection E626G heterozygous mice all died by 50 days post infection (dpi), median time to death 45.5 days; range 30–50 dpi. 87% of WT B6 controls were alive when the experiment ended at a predetermined 70 dpi, resulting in a median time to death of >70 days. Mediastinal lymph nodes in E626G heterozygous mice had reduced numbers of B cells and activated (CD62Llow) T cells compared to B6 controls on 14 dpi. Cells from infected lungs from E626G heterozygotes produced less IFN-gamma after infection on 28, 35 and 42 dpi. Interferon stimulated cytokines (IP-10, MIG, MIP-2) were also significantly reduced compared to WT controls. Ongoing work includes examining the cells requiring STAT4 signaling and IFN-gamma production as well as the mechanism of reduced accumulation of immune cells in the draining lymph nodes.