Sialophorin is an essential host element for vaccine immunity against pulmonary fungal infections

The global burden of fungal infections is alarming, primarily due to the increasing immune-compromised population. The immuno-preventive/therapeutic measures, including vaccines, are necessary to prevent or control fungal diseases. Identifying a protective host element as a functional phenotypic marker is immensely valuable. We identified a host element, sialophorin, preferentially associated with antifungal memory T cells. We investigated its role in vaccine immunity using a mouse model of pulmonary fungal infection. We found that sialophorin was essential to bolster CD8+ T-cell responses to the vaccine by enhancing their differentiation and expanding cytokine-producing cells required for immunity. Using a gain-of-function approach, activating sialophorin using mAb augmented the CD8+ T cell responses, and sialophorin-sufficient CD8+ T cells were competitively superior in differentiation and expansion to the deficient cells. Sialophorin-mediated vaccine immunity was independent of the T cell trafficking effect. Finally, we show that sialophorin is a potential functional phenotypic marker of fungal vaccine-potency and immunity. Our study revealed that sialophorin is an essential host-target element to bolster vaccine responses and serves as a potential biomarker of fungal immunity. Author Summary Fungal infections have been rising in recent years due to increased immunocompromised individuals. Vaccination of at-risk individuals helps counter the infections. Thus, suitable vaccine platforms are needed with apt adjuvants, and a phenotypic marker of vaccine immunity will bolster the efforts. We identified a phenotypic marker, sialophorin, associated with T cell vaccine immunity to fungal infection. Our findings show an essential role of sialophorin for fungal immunity, as a target of adjuvanticity, and as a potential biomarker of vaccine immunity against many fungal infections. ### Competing Interest Statement The authors have declared no competing interest.