July 02, 2017
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HIV vaccine boost generates higher immune response 6 to 8 years later

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Boosting Thai participants from the RV144 HIV vaccine trial 6 to 8 years after their initial vaccination generated higher immune responses compared with those seen immediately after RV144; however, these humoral and CD4+ T cell responses were short lived and did not grow after subsequent boosting, according to recent data published in The Journal of Infectious Diseases.

These results come from a late-boost follow-up study to RV144, known as RV305, which demonstrated 60% efficacy against HIV acquisition at 1 year and 31.2% efficacy at 3.5 years.

“Because antibody responses waned rapidly after vaccination, we hypothesized that additional boosts given to RV144 vaccines might augment responses inversely correlated with infection risk, providing a rationale to inform the vaccination schedule for future efficacy trials,” study researcher Col. Robert J. O’Connell, MD, chief of retrovirology at the Armed Forces Research Institute of Medical Sciences (AFRIMS) in Bangkok, and colleagues wrote.

Led by researchers from AFRIMS and the Thai Ministry of Health, this randomized, double blind, placebo-controlled trial of late boosts in 162 HIV–negative RV144 vaccine participants examined the responses of using the ALVAC-HIV (Sanofi Pasteur) or AIDSVAX B/E (VaxGen) vaccines, either in combination or alone. Participants received the boosts 6 to 8 years after their RV144 vaccination to determine their safety and immunogenicity at 0 and 24 weeks. They received either ALVAC-HIV plus AIDSVAX B/E, AIDSVAX B/E alone, ALVAC-HIV alone, or placebo.

The results of the RV305 trial showed that the vaccines were safe and well-tolerated among all groups. Participants who received AIDSVAX B/E experienced plasma immunoglobulin (Ig) G, IgA and neutralizing antibody responses at week 2 that were all significantly higher than 2 weeks after the last RV144 vaccination compared with those who did not receive the AIDSVAX B/E boost. However, these responses were transient and their magnitude did not increase with a subsequent boost. IgG titers rose 14-fold compared with 2 weeks after the last RV144 vaccination. Those who received ALVAC-HIV had similar results to placebo recipients.

“We remain grateful to all of the volunteers who returned to participate in this study 6 to 8 years after the original trial,” Sandhya Vasan, MD, science director of the department of retrovirology at AFRIMS, said in the release. “It is a testament to the long-standing joint commitment between Thailand and the United States to ending the HIV epidemic.” – by Savannah Demko

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Disclosure: O’Connell reports no relevant financial disclosures. Please see the full study for a list of all other authors’ relevant financial disclosures.