Innate and adaptive immune interactions in Coccidioides infection

Abstract Protective immunity against the fungal pathogen Coccidioides requires specific T helper cellular responses. Mouse infection and vaccine studies have defined CD4 T helper (Th)1 and Th17 cells in the resolution of infection and in effective protection, while patients with chronic Coccidioides infection demonstrate reduced cellular responses. Several gaps in knowledge preclude our ability to develop new diagnostics and therapeutics for treating this infection. Little is known about the microenvironment in human lung tissue during infection, and the types of immune cells that promote effective control of the fungus within this specialized location. How variations on local immune populations alter disease severity and ability of the fungus to disseminate have not been explored. We recently identified several peripheral blood biomarkers during acute infection that distinguish pediatric patients that resolve infection from those that develop chronic disease. Patients with chronic disease had reduced Th17 and elevated Treg frequencies compared to patients that resolved disease. The inability to clear Coccidioides infection may be a result of elevated Treg frequency and functional capacity, or of skewed effector differentiation. We use mouse Coccidioides infection and in vitro culture assays to uncover the host immune players that promote effective immunity, and to identify fungal morphology changes and fungal burden differences at the innate and adaptive immune interface.