An Rv1471-expressing chimpanzee adenovirus vaccine confers protection against tuberculosis by inducing alveolar macrophage trained immunity and polyfunctional T-cell responses

The limited protection afforded by Bacille Calmette-Guérin (BCG) against pulmonary tuberculosis (TB) underscores the critical need for novel vaccine strategies. Alveolar macrophages (AMs), as the primary sentinel cells encountering inhaled Mycobacterium tuberculosis (Mtb), play a decisive role in early infection outcomes, yet their potential as a direct vaccine target remains largely untapped. Here, we developed a chimpanzee adenovirus vaccine expressing the Mtb antigen Rv1471 (rAd-Rv1471), which we previously identified for its unique capacity to induce innate immune memory. In murine models, intranasal rAd-Rv1471 administration reprogrammed AMs into a trained state, characterized by enhanced production of pro-inflammatory cytokines, elevated surface expression of MHC II and CD86, and improved cell-intrinsic control of intracellular mycobacterial growth. Transcriptomic analysis revealed upregulation of key immunometabolic pathways, including Akt/mTOR/HIF-1α signalling and glycolysis. Concurrently, intranasal rAd-Rv1471 administration induced potent antigen-specific, polyfunctional T cells in the lung. This dual engagement of innate and adaptive immunity conferred significant protection against aerosol Mtb challenge. Furthermore, rAd-Rv1471 acted as an effective heterologous booster, enhancing protection in BCG-primed mice. Our findings establish rAd-Rv1471 as a synergistic mucosal vaccine candidate that concurrently induces trained immunity in AMs and polyfunctional T-cell responses, highlighting a promising dual-targeting strategy for next-generation TB vaccines.