Influence of BCG Immunization on Immune Responses and Disease Progression in South African HIV Exposed and Infected Infants

In sub-Saharan Africa (SSA), more than 300,000 babies with HIV die each year. HIV-infected children develop AIDS and die faster in SSA than those in developed countries. Bacille Calmette-Guerin (BCG) vaccine is given to infants at birth in SSA to protect them from severe forms of TB. BCG is known to cause immune cells to be active and replicate faster. The immune system of neonates also responds differently to BCG that to other vaccines and infections. We hypothesize that the routine immunization of neonates with BCG contributes to generalized immune activation in HIV-exposed infants resulting in skewed immune responses to vaccines and infections and increased rates of disease progression in those infants that become HIV-infected. However, delaying BCG until HIV testing is completed would result in operational difficulties, and may not induce the appropriate immune response. Delayed BCG would also render many HIV-exposed uninfected infants at high risk for disseminated TB. We plan to assess immune cells in infants to determine the impact of the timing of BCG vaccination on immune responses to tuberculosis (TB) and other vaccines. We will also compare the immune activation and disease progression of those infants that become HIV-infected in the BCG or control arms. Our results will provide key insights into the effect of BCG vaccination on immune responses to HIV as well as inform the optimal timing of BCG vaccination for HIV-exposed infants.