A cocktail of Mycobacterium bovis BCG recombinants expressing the SIV Nef, Env, and Gag antigens induces antibody and cytotoxic responses in mice vaccinated by different mucosal routes

Recombinant live Mycobacterium bovis BCG strains (rBCG) expressing different human immunodeficiency virus (HIV) or simian immunodeficiency (SIV) antigens could be good candidates for the development of vaccines against AIDS. To develop effective HIV/SIV vaccines, humoral and cellular immune responses directed against multiple antigens may be essential for the control of the infection. In this study we immunized BALB/c mice via different mucosal routes (oral, aerogenic, nasal, and rectal) with a mixture of three rBCG strains expressing, respectively, the entire SIVmac251 Nef protein, and large fragments of the Env and Gag proteins. All routes of immunization studied induced immunoglobulin A (IgA) antibodies against mycobacterial PPD, SIV Env, and SIV Gag antigens in feces and bronchial lavages as well as specific immunoglobulin G (IgG) in serum. Strong, specific cytotoxic responses of splenocytes against Nef, Env, and Gag was observed whatever the mucosal route of immunization. Therefore, mucosal vaccination with a cocktail of rBCG strains induces local, specific IgA, systemic IgG, and systemic CTLs against the three SIV antigens expressed. Rectal and oral routes seemed the most appropriate route of vaccination to be used to protect against SIV infection.