Scientists at Caltech have demonstrated that a technique they had developed to protect mice from a lab strain of HIV delivered intravenously also works against the real-world form of HIV usually transmitted across mucosal surfaces.
The study (“Vectored immunoprophylaxis protects humanized mice from mucosal HIV transmission”), which appears in an advance online publication of Nature Medicine, suggests that the delivery method might be effective in preventing vaginal transmission of HIV between humans, according to the researchers.
“The method that we developed has now been validated in the most natural possible setting in a mouse,” says David Baltimore, Ph.D., president emeritus and the Robert Andrews Millikan Professor of Biology at Caltech. “This procedure is extremely effective against a naturally transmitted strain and by an intravaginal infection route, which is a model of how HIV is transmitted in most of the infections that occur in the world.”
The new delivery method, Vectored ImmunoProphylaxis, or VIP for short, is not exactly a vaccine. Vaccines introduce substances such as antigens into the body to try to get the immune system to mount an appropriate attack—to generate antibodies that can block an infection or T cells that can attack infected cells. In the case of VIP, a small, harmless virus is injected and delivers genes to the muscle tissue, instructing it to generate specific antibodies.
“Here we demonstrate [using broadly neutralizing antibodies] that VIP is capable of protecting humanized mice from intravenous as well as vaginal challenge with diverse HIV strains despite repeated exposures,” wrote the investigators. “Moreover, animals receiving VIP that expresses a modified VRC07 antibody were completely resistant to repetitive intravaginal challenge by a heterosexually transmitted founder HIV strain, suggesting that VIP may be effective in preventing vaginal transmission of HIV between humans.”
The researchers emphasize that the work was done in mice and that the leap from mice to humans is large. The team is now working with the Vaccine Research Center at the NIH.