A single immunization with CAF08 provides newborns with Th1-mediated protection against Respiratory Syncytial Virus infection

Abstract Respiratory Syncytial Virus (RSV) is a leading cause of morbidity and mortality in children, due in part to their distinct immune system, characterized by impaired induction of T-helper 1 (Th1)-immunity. Here we describe cationic adjuvant formulation (CAF)-08, a liposomal vaccine formulation tailored to induce Th1 immunity in early life via synergistic engagement of Toll-like Receptor 7/8 and the C-type lectin receptor Mincle. Quantitative phosphoproteomics applied to human dendritic cells revealed a key role for Protein Kinase C-δ for enhanced Th1 cytokine production in neonatal dendritic cells and identified signaling events resulting in antigen cross-presentation. In vivo, a single immunization at birth with CAF08-adjuvanted RSV pre-fusion antigen protected newborn mice from RSV infection through induction of antigen-specific CD8+ and Th1 cells. Overall, we describe a novel pediatric adjuvant formulation and characterize its mechanism of action providing a promising avenue for development of early life vaccines against RSV and other intracellular pathogens.