Determining Why HIV Vaccine Was Not Successful

Despite inducing anti-HIV antibodies, vaccine in HVTN 505 trial still not protective.

A recent study was able to explain why a promising HIV vaccine was unsuccessful in protecting against the virus.

The study, conducted by the National Institute of Allergy and Infectious Diseases and Duke University, evaluated why the candidate vaccine tested in the HVTN 505 clinical trial was not able to protect against HIV infection even while producing anti-HIV antibodies. The researchers found the vaccine stimulated antibodies that identified HIV in addition to microbes that are commonly found in the intestinal tract.

The study results indicate the vaccine boosted an antibody response to the intestinal microbiome, which may be why the HVTN 505 candidate did not protect against infection, the study noted. This discovery may aid research efforts to find a vaccine against HIV and other infectious diseases.

The HVTN 505 study explored a novel regimen that vaccinated patients first with a prime vaccine followed by a booster vaccine.

An examination of samples from participants showed the majority of vaccine-induced antibodies recognized the HIV surface protein gp41 without neutralizing the virus. The antibodies instead recognized other proteins common to bacteria that naturally occur in the intestinal microbiome.

This reaction represents a significant hurdle that vaccine developers must overcome to prevent HIV infection. Further research may be necessary to evaluate how the microbiome impacts the production and efficacy of vaccine-induced antibodies that fight HIV and how it influences vaccine-induced immunity, the study noted.