Viral Control After Early Antiretroviral Treatment May Guide Vaccine Research.

2001 OCT 24 - (NewsRx.com & NewsRx.net) -- by Michael Greer, senior medical writer - Antiretroviral treatment given during acute simian immunodeficiency virus (SIV) infection enables natural viral control after therapy cessation, researchers in the United States report.

"Transient antiretroviral treatment with tenofovir...begun shortly after inoculation of rhesus macaques with the highly pathogenic [SIV] isolate SIVsmE660, facilitated the development of SIV-specific lymphoproliferative responses and sustained effective control of the infection following drug discontinuation," explained Jeffrey D. Lifson and colleagues at the National Cancer Institute in Frederick, Maryland, the New England Regional Primate Research Center in Southborough, Massachusetts, the National Institutes of Health in Rockville, Maryland, Beth Israel Deaconess Medical Center in Boston, Centocor, Inc., Malvern, Pennsylvania, Gilead Sciences, Inc., Foster City, California, and Princeton University in Princeton, New Jersey.

Although the mechanisms behind this viral control remain somewhat of a mystery, this phenomenon may help guide researchers developing vaccines to prevent HIV infection, Lifson and coworkers report.

Animals that showed consistent viral control in the absence of antiretroviral drugs were rechallenged with homologous and heterologous SIV strains, in some cases more than a year after the original infection. Although these macaques displayed undetectable levels of neutralizing antibodies, they were still resistant to SIV challenge, the researchers found.

Viral loads rose dramatically after cytotoxic T lymophocyte depletion, by as much as 5 logs, study data showed. Restoration of CD8 cells reduced viremia to ...