By Robert Yule
Today, Dr. Heather Jaspan – a recipient of an EGPAF Pediatric HIV Vaccine Program Grant – released late-breaking results from her study at the International AIDS Conference.
The study investigated whether early administration of the Bacille Calmette-Guerín (BCG) vaccine for tuberculosis could be associated with an increased risk of HIV infection for HIV-exposed, breastfed infants in South Africa.
Dr. Jaspan presents the results of her study and their implications below:
Bacille Calmette-Guerín (BCG) vaccine is given to infants at birth in high Tuberculosis (TB) burdened areas such as Southern Africa to protect them from severe forms of TB.
BCG given to monkeys causes immune cells to be active and replicate faster. HIV preferably infects cells that are actively replicating and have the HIV receptors CD4 and CCR5 on their surface. People who are frequently exposed to HIV yet remain negative have lower numbers of these HIV target cells in their blood.
We hypothesized that the routine immunization of neonates with BCG contributes to generalized immune activation in HIV-exposed infants, resulting in increased HIV target cells and increased risk for HIV transmission via breastfeeding.
We randomly assigned HIV-exposed and uninfected newborns to BCG vaccination at birth versus at 8 weeks of age. We determined the proportion of HIV target cells (activated CD4+CCR5+ cells).
Babies in the early BCG group had significantly higher HIV target cells in their blood than those in the delayed arm. This difference persisted at 8 weeks, despite immune stimulation from routine immunizations at 6 weeks in all babies.
No other cells were activated and no other markers of inflammation increased, suggesting the effect of BCG is isolated to CD4 T cells. Therefore BCG vaccination may increase the risk of HIV infection for HIV-exposed, breastfed infants.
However, other results not presented today show that infants with higher target cell activation had better responses to tetanus vaccine given at 6 weeks of age. This suggests that, in addition to protection against severe TB, BCG may have other benefits for HIV-exposed infants.
Therefore, the potential risks and benefits of BCG need further evaluation and investigation.
Our results can inform policy for the optimal timing of BCG vaccination for HIV-exposed infants, and have implications for the use of related vaccines – such as live, weakened bacterial vaccines – as potential future HIV vaccine strategies for newborns.
Dr. Heather Jaspan is a Senior Lecturer at the University of Cape Town and a Senior Scientist at Seattle BioMedical Research Institute.