Vaccine induces HIV-specific immune response in chronic infection.

2003 JUN 11 - (NewsRx.com & NewsRx.net) -- A controversial vaccine against HIV has been shown to stimulate a critical part of the HIV-specific immune response in chronically infected patients.

The small study conducted by researchers at Massachusetts General Hospital (MGH) finds that a vaccine made from an inactivated form of the AIDS virus (Remune) induces the proliferation of CD4 cells - also called T helper cells - that specifically target HIV.

Appearing in the June 2003 issue of the journal AIDS, the study is the first clear demonstration of the potential reconstitution of the immune response in chronic HIV infection. However, this pilot study was not designed to tell whether or not the vaccine would have any effect on the eventual course of the disease.

When the human body is infected by a typical virus, the immune system mounts a response that starts with the production of T helper cells specifically targeted against the particular virus. T helper cells are the immune system's "generals," directing the activity of T killer cells (also called cytotoxic T lymphocytes or CTLs) that attack the invading virus. But when the virus is HIV, the T helper cells themselves are destroyed by the virus.

"A hallmark of HIV infection is the absence of immune cells that recognize the virus and develop an antiviral response," said Gregory Robbins, MD, MPH, of the MGH infectious disease division and the Partners AIDS Research Center, the paper's lead author. "Our carefully controlled study showed that this vaccine was able to induce one aspect of a normal response against HIV in patients who previously did not have such a response."

One of several potential vaccines being tested against HIV, Remune is made from killed, inactivated HIV from which the outer protein envelope has been removed. It is designed to be a therapeutic vaccine that could increase the body's defenses against a pre-existing infection, rather than a preventive vaccine to keep infection from occurring. An earlier study of the vaccine did not find an effect on disease progression.

However, that study was stopped prematurely due to the decrease in AIDS-related illness resulting from the introduction of more effective antiviral drug combinations. In addition, the study was not well controlled. Participants differed in terms of the antiviral medications they were taking, and many changed their medications during the course of that study, making interpretation of the findings problematic.