RV144, AN ONGOING HIV VACCINE EFFICACY TRIAL IN THAILAND
On Sept. 29, 2003, the U.S. and Royal Thai governments jointly initiated RV144, a clinical efficacy trial to evaluate a novel HIV vaccine strategy commonly referred to as "prime-boost." The main objective of this large-scale, Phase III trial is to determine if a combination vaccine prevents HIV infection; secondarily, whether it controls HIV if infection occurs. More than 500 volunteers have already been enrolled in the trial in two provinces in Thailand.
In a Policy Forum published in the Jan. 16, 2004 issue of Science, Burton et al. opine that RV144 should not be conducted based on a prediction that the combination will not be efficacious; that the underlying immune-based hypothesis has shifted to CD4+ T cells only; and that review and approval processes lacked adequate scientific expertise and judgment. No evidentiary data is provided to support the prediction and assertions.
The U.S. government sponsors, the National Institute of Allergy and Infectious Diseases (NIAID) and the U.S. Army Medical Research & Materiel Command (USAMRMC), strongly disagree with the authors' opinions. A formal rebuttal is being prepared for publication in Science in the near future.
The scientific hypothesis being examined in the study is whether a vaccine combination that induces both arms of the human immune system, cell-mediated immunity and antibody-mediated immunity, will provide protection against HIV. The prime-boost comprises a combination of Aventis Pasteur's ALVAC-HIV (vCP1521) and VaxGen's gp120 (AIDSVAX B/E). In combination, these vaccines induce a repertoire of immune responses quantitatively and qualitatively different from those induced by either component alone. Prime-boost is expected to induce a constellation of immune responses including CD8+ T cells, CD4+ T cells and antibodies in 25 to 100 percent of volunteers, depending on the laboratory measurement employed.
Between 1999 and 2001, Thai and U.S. scientists evaluated the prime-boost in Phase I and II clinical trials and determined that the strategy was safe and induced immune responses meeting pre-defined and thoroughly-vetted milestones; and that these data justified conducting an efficacy evaluation. No laboratory tests or animal models have been demonstrated to predict HIV vaccine efficacy in humans. Thus, only human trials can determine efficacy.
Between 2001 and 2002, the RV144 study plan was reviewed and approved by 11 international scientific/technical, ethical and regulatory review bodies in Thailand, the United States and at the World Health Organization. RV144 is being conducted under the regulations of both Thai and U. S. Food and Drug Administrations.
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