Eventual Viral Escape From Cytotoxic T Cells May Limit Vaccine Efficacy.(Brief Article)

2002 FEB 6 - (NewsRx.com & NewsRx.net) -- by Michael Greer, senior medical writer - HIV vaccines based on the induction of cytotoxic T cell responses may not provide long-term protection, researchers in the United States warn.

"Potent virus-specific cytotoxic T lymphocyte (CTL) responses elicited by candidate AIDS vaccines have recently been shown to control viral replication and prevent clinical disease progression after pathogenic viral challenges in rhesus monkeys," according to Dr. Dan H. Barouch and colleagues at Harvard

Medical School in Boston, Northwestern University Medical School in Chicago, Duke University Medical Center in Durham, North Carolina, and the nonprofit Southern Research Institute in Frederick, Maryland.

However, the protection conferred by these vaccines can be quickly overcome by resourceful viruses, Barouch and coworkers found.

They studied rhesus macaques infected with a highly virulent hybrid of the simian and human immunodeficiency viruses known as SHIV, according to the report. This virus is so pathogenic that some researchers question its validity as an accurate model of HIV infection.

A single mutation in a gene coding for an epitope of the SHIV Gag protein easily recognized by CTLs enabled the mutated strain to avoid destruction by T cells. Although the infected animal had maintained undetectable viral loads until this mutation, it quickly succumbed to the rapid burst of viral replication and CD4 cell depletion ...