HIV vaccine trial shines light on potential virus vulnerabilities
The Duke study, which appeared in Monday's issue of Proceedings of the National Academy of Sciences, announced a new response from antibodies that not only provides insight into how to attack the HIV virus, but also which vaccine to administer to infected persons based on blood samples. The vaccine trial was named RV144 and used two investigational vaccines in combination to produce a 31 percent protection rate.
The success rate fell short for what is needed for approval, but the insight gained during the study shines light on why the vaccines weren't more effective. Georgia D. Tomaras, director of the Laboratory of Immune Responses and Virology at DHVI, led the study.
"We learned that a specific vaccine-induced immunoglobulin A can weaken the protective effect of immunoglobulin G. IgA competes with IgG to bind to the same site on the virus's outer envelope that is exposed on infected cells," Tomaras said. "In work with my colleague here at Duke, Dr. Guido Ferrari, we found that the IgA antibodies can block the activity of natural killer cells activated by IgG, further interfering with the vaccine-induced immune response."
A correlation was found between high immunoglobulin A levels and decrease vaccine efficacy. Tomaras said the ratio of IgA to IgG in blood may be a useful indicator for which vaccine to use on an individual.
"Understanding that certain vaccine-induced immunoglobulin A antibodies in the blood may interfere with an antiviral function of another antibody is a new finding that can lead to further vaccine development on how to induce effective antibody responses," Tomaras said.