A lentiviral vector expressing a dendritic cell-targeting multimer induces mucosal anti-mycobacterial CD4 T-cell immunity.

Most viral vectors, including the potently immunogenic lentiviral vectors (LVs), only poorly direct antigens to the MHC-II endosomal pathway and elicit CD4 T cells. We developed a new generation of LVs encoding antigen-bearing monomers of collectins substituted at their C-terminal domain with the CD40 ligand ectodomain to target and activate antigen-presenting cells. Host cells transduced with such optimized LVs secreted soluble collectin-antigen polymers with the potential to be endocytosed in vivo and reach the MHC-II pathway. In the murine tuberculosis model, such LVs induced efficient MHC-II antigenic presentation and triggered both CD8 and CD4 T cells at the systemic and mucosal levels. They also conferred a significant booster effect, consistent with the importance of CD4 T cells for protection against Mycobacterium tuberculosis. Given the pivotal role of CD4 T cells in orchestrating innate and adaptive immunity, this strategy could have a broad range of applications in the vaccinology field.