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Preventive and Therapeutic HIV Vaccine Data Presented at AIDS Vaccine 2011


The AIDS Vaccine 2011 conference, which concluded last week in Bangkok, brought together more than 800 researchers, public health officials, advocates, and others to hear the latest findings on vaccines intended to prevent HIV infection and control disease progression.

RV 144 Follow-up

Among the most eagerly anticipated reports was further data from the RV 144 vaccine trial. As reported in September 2009, this large trial in Thailand was the first to demonstrate proof of concept that a preventive vaccine could work, though the effect was modest, with a risk reduction of 31%.

Since that time, an international collaboration has further examined the findings, looking for clues about how the vaccine provided protection against HIV in the hopes of developing more effective candidates.

Barton Haynes from Duke University, who coordinated the extensive collaborative effort, reported that 2 types of immune response were significantly correlated with changes in risk of HIV infection among RV 144 vaccine recipients:

  • Immunoglobulin G (IgG) antibodies that bind to the V1/V2 variable loop of HIV envelope were associated with a 43% risk reduction (the lowest infection rate), which rose to 71% for vaccine recipients with high-level V1/V2 response. 
  • Immunoglobulin A (IgA) antibodies in plasma that bind to the HIV envelope were associated with a 54% increase in risk of infection (the highest infection rate), suggesting that high-level IgA response somehow interferes with vaccine efficacy.

Haynes hypothesized that IgA antibodies may block antibody-dependent cellular cytotoxicity, a mechanism for eliminating HIV-infected cells. Researchers did not have samples available to examine mucosal IgA responses.

Further analysis of the data is ongoing, and some RV 144 vaccine recipients will be given a booster vaccine to see if this can increase or extend protective immunity. Forthcoming trials will look at a prime-boost vaccine strategy (similar to that used in RV144) in different at-risk patient populations.

Bionor Vacc-4x

Researchers also presented findings from one the furthest advanced trials of a therapeutic vaccine candidate designed to reduce disease progression among people already infected with HIV.

Jan van Lunzen from University Medical Centre Hamburg-Eppendorf presented data on Bionor Pharma's Vacc-4x, which is designed to boost immune response to a conserved domain of HIV's p24 core protein.

According to findings announced at a press conference and released by Bionor, participants who received Vacc-4x experienced a 70% viral load decrease relative to their level before starting antiretroviral therapy (ART), compared with no notable reduction among placebo recipients.

Vacc-4x recipients also showed significantly greater reductions in viral load set-point at week 28 compared with placebo recipients, and more people who received the active vaccine were able to delay ART initiation.

“These results prove that Vacc-4x acts like a flashlight, lighting the way for the immune system to address the virus at its Achilles heel -- a proven conserved domain of HIV,” van Lunzen explained. 



AIDS Vaccine Conference Ends with Eye to Future. CDC HIV/Hepatitis/STD/TB Prevention News Update. September 19, 2011.

K Cullinan. Two clues revealed about how Thai vaccine worked. September 14, 2011.

KJ Kresge. Researchers Present Much-Anticipated Correlates Data From RV144 Vaccine Trial. IAVI Report. September 13, 2011.

IRIN. HIV/AIDS: RV144 vaccine trial - what happens next? IRIN Global. September 14, 2011.

Bionor Pharma. Results from Phase IIB Placebo Controlled Study of Bionor Pharma's Vacc-4x Show Excellent Safety Profile, Statistically Significant Viral Load Reduction in Patients with HIV who Suspend Antiretroviral Therapy. September 14, 2011.