Interleukin-23 instructs protective multifunctional CD4 T cell responses after immunization with the Mycobacterium tuberculosis subunit vaccine H1 DDA/TDB independently of interleukin-17A.

Interleukin (IL)-17A-producing T helper (Th)17 cells are increasingly being acknowledged to be associated with protective immunity to Mycobacterium tuberculosis (Mtb). Subunit vaccines potently promote protective immune responses against Mtb infection that correlate with an expansion of IL-23-dependent Th17 cells. Previous studies revealed that after vaccination, IL-23 is required for protection against challenge with Mtb but the underlying IL-23-dependent—and possibly IL-17A-mediated—mechanisms remain elusive. Therefore, we here analyzed the early outcome of Mtb infection in C57BL/6, IL-23p19-deficient (−/−), and IL-17A−/− mice after vaccination with the subunit vaccine H1-DDA/TDB to investigate the role of the IL-23-Th17 immune axis for the instruction of vaccine-induced protection. While in IL-23p19−/− mice the protective effect was reduced, protection after vaccination was maintained in IL-17A−/− animals for the course of infection of 6 weeks, indicating that after vaccination with H1-DDA/TDB early protection against Mtb is—although dependent on IL-23—not mediated by IL-17A. In contrast, IL-17A deficiency appears to have an impact on maintaining long-term protection. In fact, IL-23 instructed the vaccine-induced memory immunity in the lung, in particular the sustained expansion of tumor necrosis factor (TNF)+IL-2+ multifunctional T cells, independently of IL-17A. Altogether, a targeted induction of IL-23 during vaccination against Mtb might improve the magnitude and quality of vaccine-induced memory immune responses.