HIV is a wily infection that has found many ways to slip out of the immune system’s grasp, making it a tricky target for a preventive vaccine. A successful vaccine, experts envision, will trigger our bodies to make antibodies, a specialized type of immune protein, which can block a wide swath of HIV variants from infecting target cells. Occasionally, people infected with HIV naturally develop these broadly neutralizing antibodies — but only years after exposure and much tweaking by the immune system. An effective vaccine must protect within months, not decades.
The team drew on samples taken from infants in Nairobi born to HIV-positive mothers prior to the advent of antiretroviral drugs.
Infants can produce broadly neutralizing antibodies within the first year of HIV infection, requiring much less somatic hypermutation to generate a broadly neutralizing antibody than would be expected in adults. Additionally, this antibody response is not dominated by just a single antibody, but it appears to be polyclonal, which may make it harder to evade.
In contrast to work in adults, “we could document a case in infants where a broadly neutralizing antibody developed in a time frame and in a way that is something that we could consider mimicking with a vaccine,” Overbaugh said.
Overbaugh leads efforts in the HIV field to examine broadly neutralizing antibodies in infants. The findings demonstrate that key differences in the infant immune response to HIV, or the viruses transmitted to infants, could shed light on ways to improve HIV vaccine design.
The study describes the generation of broadly neutralizing antibodies after natural HIV infection, but does it not show that such antibodies would protect against infection.