Scientists at Emory University’s Yerkes National Primate Research Center recently published results of a study that detail how vaccines designed to protect against HIV can actually backfire and lead to infection.
The findings, which were published in a recent edition of the "Proceedings of the National Academy of Sciences," show that vaccination may increase the number of immune cells that serve as viral targets.
"One of the reasons why it has been so difficult to make an AIDS vaccine is that the virus infects the very cells of the immune system that any vaccine is supposed to induce," Guido Silvestri, senior author and chief of microbiology and immunology at Yerkes National Primate Research Center, said. "This study shows that if a vaccine induces high levels of activated CD4+ T cells in mucosal tissues, any potential protective effect of the vaccine may be hampered.”
Silvestri, also a professor of pathology and laboratory medicine at Emory and a Georgia Research Alliance Eminent Scholar, co-wrote the paper with first author and senior research specialist Diane Carnathan, and colleagues from the Wistar Institute, Inovio Pharmaceuticals and the University of Pennsylvania.
In the study, scientists and researchers immunized rhesus macaques with five different combinations of vaccines encoding simian immunodeficiency virus (SIV) proteins that are found only on the inside of the virus.
This experimental strategy, a reductionist approach, had the monkeys receive an initial immunization followed by two booster shots at 16 and 32 weeks. The monkeys were then exposed to repeated low-dose intrarectal challenges with SIV once per week, up to 15 times each.
Overall, the immunizations failed to prevent SIV infection.