Despite the global rise in fungal infections, including those by endemic sp ., there is no licensed fungal vaccine available. This is mainly due to poor understanding of mechanisms of vaccine immunity, and lack of a functional phenotypic marker associated with vaccine efficacy. Opportunistic fungal infections, including those caused by dimorphic fungi, Histoplasma, Coccidiodes and Blastomyces, are rising at an alarming rate in such at-risk individuals. A major limitation in the development of tailored fungal vaccines for the at-risk population is poor understanding of requisite elements of CD8+ T cell responses to mediate vaccine-immunity. Recent advances in the understanding of immune correlates against fungal infections has helped in advancing vaccinology in parallel. T-cell derived IL-17A, IFN?, GM-CSF, IL-22, and TNF? are primarily involved in protection against fungi. Identification of potential targets on host cells can provide novel efficacious vaccine platforms, including for immunocompromised. We have established a mouse model of CD4+ T cell lymphopenia, where CD8+ T cells can be stimulated to produce protective cytokines IL-17A (Tc17) and IFN? (Tc1) to execute a sterilizing immunity against lethal pulmonary fungal infection. We have shown that vaccine-elicited antifungal CD8+ T cells persisted as long-term functional memory. In this proposal, we present seminal findings: 1. GM-CSF+ Tc17 cells bolster vaccine-immunity without pathology; 2. Anti-fungal CD8+ T cells preferentially express O-glycosylated Sialophorin; and 3. Sialophorin is required for differentiation and expansion of CD8+ T cells. Therefore, our central hypotheses are that (1) Sialophorin acts as a co-stimulator for CD8+ T cell responses, (2) retention of Sialophorin is essential for memory CD8+ T-cell homeostasis and recall responses, (3) Sialophorin signaling potentiates cross-presentation to augment CD8+ T cell responses.
Our specific aims are to: 1. Determine and dissect the role of Sialophorin for CD8+ T-cell fungal vaccine responses. We will decipher and delineate the cell- intrinsic role of Sialophorin for vaccine-induced Tc17 and Tc1 cell responses using adoptive transfer and bone- marrow chimera experiments, and using TCR? KO, congenic and crosses of Sialophorin KO mice. 2. Elucidate the role of Sialophorin for memory T cell homeostasis and recall responses during fungal pneumonia. We will define the role of Sialophorin for vaccine-induced memory CD8+ T-cell homeostasis, recall responses, and vaccine-immunity. We will use bone marrow chimera, adoptive transfers, CRISPR-Cas9 gene-editing, in vivo stimulation, and E-selectin blocking to delineate the role of Sialophorin on memory CD8+ T-cell responses. 3. Dissect the role of Sialophorin on dendritic cells for CD8+ T-cell fungal vaccine responses. We will identify the role of CD43 on antigen-presenting cells for activation of CD8+ T cells following vaccination . Our findings will uncover the functional role of Sialophorin for fungal CD8+ T-cell responses and immunity to guide in the design of novel vaccine platforms and test the efficacy of vaccines.
Emerging and recalcitrant fungal infections, especially in immunocompromised patients, have significantly risen in recent years. As no licensed fungal vaccines are available, our work aims to uncover the basis of fungal vaccine immunity, and identity of a protective surface marker that has profound implications of T-cell based vaccine-efficacy. Our work is of translational in nature, and will serve as a guide to other fungal vaccine platforms tailored for immunocompromised individuals.