Repetitive vaccination with intravenous BCG is safe and immunogenic in naive and SIV-infected macaques

Abstract Tuberculosis (TB) is the leading cause of death in people with HIV (PWH) on or off antiretroviral therapy (ART); thus, new TB vaccine candidates should be evaluated in the setting of HIV. Mycobacterium bovis Bacillus Calmette-Guerin (BCG), the live attenuated bacterial TB vaccine given intradermally (ID) at birth, is contraindicated in PWH. We recently demonstrated that intravenous (IV) delivery of BCG elicits superior immunity and protection compared to ID delivery against Mycobacterium tuberculosis (Mtb) challenge in rhesus macaques. To assess IV BCG in an animal model of HIV infection, we immunized SIVmac251-infected macaques on suppresive ART (6m) and uninfected controls. Rhesus macaques received three doses of IV BCG, 8wks apart, and were monitored for the presence of BCG colony forming units (CFU) in peripheral blood and bronchoalveolar lavage (BAL) and Mtb-specific T cell responses in BAL. Repetitive IV BCG immunization was well-tolerated in SIV-infected and uninfected animals, with no difference in clinical parameters or BCG CFU in blood or BAL. T cell responses after IV BCG were similar, with both groups displaying a 10–50 fold increase in BAL T cell abundance after initial dose. Mtb-specific CD4 and CD8 responses peaked after the initial IV BCG dose and were maintained by subsequent immunizations for at least 6m. These data indicate that IV BCG is safe and immunogenic in SIV-infected, ART-suppressed macaques and that IV BCG boosting maintains T cell responses at the site of infection. NIH Intramural Program