BCG vaccine elicits both T-cell mediated and humoral immune responses directed against mycobacterial lipid components.

The universe of antigens recognized by alphabeta T cells has recently been expanded to include not only major histocompatibility complex (MHC)-presented protein antigens but also CD1-presented lipid antigens. The significance of lipid-reactive T cells in host defense has been appreciated, using the guinea pig model of human tuberculosis. Here, we show that immunization with Mycobacterium bovis bacillus Calmette-Guerin (BCG), the commonly used anti-tuberculosis vaccine, induces activation of guinea pig cytotoxic T cells recognizing BCG lipids in the context of CD1 molecules. Further, BCG-immunized, but not mock-immunized, guinea pigs mount IgG antibody responses directed against lipoarabinomannnan, an essential cell wall lipid component of mycobacteria. These observations emphasize the ability of BCG to activate the host adaptive immunity to mycobacteria-derived lipids, which could potentially contribute to protection against tuberculosis.