New research from Harvard Medical School indicates that candidate AIDS vaccines that are currently being tested in clinical trials may cause mutated versions of the virus to emerge and spread in certain populations.
The work is just the latest by Assistant Professor of Medicine Dan Barouch to indicate that this type of hoped-for AIDS vaccine may be limited by the virus’ ability to mutate into different forms and yet remain able to cause disease.

It is that chameleonlike ability that has thwarted predictions of when a safe and effective AIDS vaccine will be developed, from Secretary of Health and Human Services Margaret Heckler as early as 1984, President Bill Clinton in 1997, and Health and Human Services Secretary Tommy Thompson in 2001.

The virus’ ability to change its form and remain potent is an important contributing factor to its rise as a major global health threat despite a worldwide scientific effort aimed at understanding, treating, and preventing the disease.

In 2004, an estimated 3.1 million people died of AIDS while 5 million new infections occurred. Roughly 40 million people worldwide are thought to be living with either AIDS or HIV, the virus that causes AIDS, according to December 2004 statistics from the Joint United Nations Programme on HIV/AIDS.

Dozens of candidate vaccines against HIV, the human immunodeficiency virus, have been developed over the years using many different approaches. The type of candidate AIDS vaccine explored by Barouch and colleagues at Harvard Medical School and the National Institutes of Health uses bits of HIV DNA to trick the body into producing proteins found in the AIDS virus.

The hope is that the body will recognize the proteins as foreign and mount an immune response, particularly by one of the body’s many defensive cells, called killer T cells. Killer T cells attack and destroy cells containing the AIDS virus and have proven critically important in controlling the virus’ spread. The initial immune response would prime the body’s defenses to HIV, speeding the response of killer T cells should an individual become infected.

While initial tests in a monkey model of AIDS showed this type of vaccine may be effective in controlling AIDS virus replication, Barouch’s past research shows that the vaccine works for a time, but then the virus may mutate into a form that is not recognized by the killer T cells.