HIV Vaccine Trial Ends Before It Starts

Less than a year after Merck gave up on its initially promising HIV vaccine trial, the U.S. government announced yesterday that it too was giving up on a massive HIV vaccine trial.

Plans for a large human trial of a promising government-developed H.I.V. vaccine in the United States were canceled Thursday because a top federal official said scientists realized that they did not know enough about how H.I.V. vaccines and the immune system interact.

The decision is a major setback in an effort to develop an H.I.V. vaccine that began 24 years ago when government health officials promised a marketed vaccine by 1987. Health officials have long contended that such a vaccine would be their best weapon to control the AIDS pandemic.

A number of other H.I.V. vaccines are in various stages of testing around the world. But there had been high hopes for the government’s trial because the potential vaccine was among a new class that sought to stimulate the immune system in a different way.

The official who canceled the government trial, Dr. Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases, said it was becoming clearer that more fundamental research and animal testing would be needed before an H.I.V. vaccine was ever marketed.

Scientists say that developing a vaccine against H.I.V. is one of the most difficult scientific endeavors in history because of the uncanny nature of the virus. The government vaccine — known as PAVE, for Partnership for AIDS Vaccine Evaluation — was similar to a much-heralded vaccine that failed last year. That vaccine was developed by Merck, and Dr. Fauci’s agency helped pay for the Merck trials.

The NIH said that it is not completely abandoning the vaccine and will conduct a smaller study first to determine if it reduces HIV in the blood.

In more encouraging news, pathologists in Texas believe they have found the "Achilles heel" of HIV - a weak spot in its protein envelope that must remain constant for it to infect cells. They believe this weak spot may be the key to developing a vaccine.