Is this the reason why RV144 HIV ‘Thai trial’ didn’t protect more participants?

The RV144 ‘Thai trial' of an HIV vaccine candidate resulted in an unprecedented 31% protection rate among participants – a result that sparked something of a revival in the HIV vaccine field. Despite this encouraging result, the protection rate was still considered to be too low for the vaccine to be useful. Since then, many HIV vaccines have come and gone – with the NIAID's HVTN 505 trial being the latest casualty in the drive to stem the HIV pandemic. However, researchers at the Duke Human Vaccine Institute have published researched in Proceedings of the National Academy of Sciences (May 6th 2013) which pinpoints a previously unknown interaction between IgA and IgG antibodies as the cause of a lack of response to the RV144 vaccine.

“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,” said Georgia Tomaras, PhD, director of the Laboratory of Immune Responses and Virology at DHVI, in a press release. “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."

The ratio of virus-specific IgA to IgG may be a marker for vaccine effectiveness, as higher levels of specific IgA in blood samples compared to IgG appeared to correlate with a decreased vaccine effect.

Do you think that this development will be significant for understanding how to induce effective antibody responses and thus developing an effective HIV vaccine? You can join our discussion on LinkedIn or leave a comment below, I'd love to hear what you think.

HIV vaccine design and clinical trials were discussed at the World Vaccine Congress USA 2013 – Read more here >> If you want to know more about strategy and innovation in vaccines, you might be interested in attending the World Vaccine Congress Asia 2013, 17-20 June 2013, Singapore.

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