The quarter-century-long quest for the Holy Grail of HIV vaccine has suffered yet another major setback. The National Institute of Allergy and Infectious Diseases or NIAID , a part of the National Institutes of Health or NIH on Thursday scrapped a U.S. human trial dubbed PAVE 100, to test a HIV vaccine, saying that more research was needed before the vaccine could be tested on humans.
The PAVE 100 trial was slated to enroll patients in October 2007. But following Merck & Co. Inc.'s (MRK) decision to halt the trial of its much-touted HIV vaccine candidate MRKAd5 or V520, dubbed STEP last September, researchers were doubtful about the future of the PAVE 100 trial. Merck's V520, which focused on T-cells that attack and kill cells infected by HIV, altered the immune system, facilitating infection, rather than providing immunity against the HIV. V520 also failed to prevent HIV infection or reduce viral load of the patients in the STEP trial.
The PAVE 100 trial was initially designed to enroll 8,500 volunteers in the United States, South America, the Caribbean and Eastern and Southern Africa. Based on the analyses of the STEP study results, the NIH decided to scale down the number of participants in the PAVE 100 trial to 2,400.
The experimental vaccine to be tested in the PAVE 100 trial would also have used an adenovirus serotype 5 (Ad5) vector that is similar, though not identical, to the Ad5 vector used in Merck's failed STEP trial.
In a press release issued on July 17, the director of National Institute of Allergy and Infectious Diseases Dr. Anthony Fauci said that the decision to drop the trial was taken "after soliciting and considering broad input from the scientific and HIV advocacy communities."
However, the NIAID has not given up entirely on the PAVE 100 trial. NIAID said it believes the vaccine developed by its Vaccine Research Center scientifically intriguing and sufficiently different from previously tested HIV vaccines. The NIAID is considering testing the experimental vaccine in a smaller, more focused clinical study. In a statement issued by NIAID, it said it will entertain a proposal for an alternative study with one specific goal: to determine if the vaccine regimen significantly lowers viral load - the amount of HIV in the blood of vaccinated individuals who may later become infected with HIV.
The NIH's budget for AIDS vaccine research for this year is $497 million. According to the World Health Organization, about 33.2 million people worldwide are living with HIV. The number of AIDS deaths in 2007 was 2.1 million down from 3.9 million in 2001. Thanks to the HIV programs, which have created awareness among people, the number of new HIV infections has declined to 2.5 million in 2007 from 3.2 million infections in 1998.
A number of HIV vaccines are in various stages of the research process with some having advanced past early-stage safety trials. Only two of the vaccines were tested in large-scale trials, but both have been abandoned.
-- In 2003, Vaxgen, a Brisbane company, halted its AIDS vaccine clinical trial, which enrolled 4,500 North American and European volunteers.
-- In September 2007, Merck abandoned its AIDS vaccine study, which enrolled 3,000 volunteers.
With none of the clinical trials for HIV vaccine yielding positive results, some scientists and HIV research advocacy groups have been calling for the U.S government to suspend funds for testing existing experimental vaccines and re- allocate resources into effective, proven HIV/AIDS prevention, testing and treatment strategies.
The Bush administration's five-year, $15 billion global AIDS program expires in September of this year. Last week, the Senate approved a $48 billion relief bill to fight AIDS, malaria and tuberculosis in Africa and other developing world, over the next five years.
Though Sub-Saharan Africa is the worst hit by the AIDS pandemic, the U.S. is not far behind. Over 565,000 people have died of AIDS and an estimated 1.1 million are living with HIV in the U.S.
The United Nations has set a goal to halt and reverse the spread of HIV by 2015. The recent failures in HIV vaccine development clearly indicate that it still requires fundamental research to understand the basic biology of the AIDS virus and its effects on the human immune system. Until then, a vaccine against HIV remains a distant hope!
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