Abstract:

Acute simian immunodeficiency virus (SIV) infection is associated with a high rate of infection and subsequent loss of memory CD4+ T cells in mucosal tissues, new research reveals (Nature; published online March 27, 2005; DOI 10.1038/nature03501 and DOI 10.1038/nature03513). Mario Roederer (National Institutes of Health, Bethesda, MD, USA) and colleagues infected healthy monkeys with SIV and found that within 10 days of the infection, 30–60% memory CD4+ cells in various tissues became infected with SIV. However, by day 14, 80% of the infected cells disappeared. In an accompanying study, researchers show that SIV also kills memory CD4+ T cells without directly infecting these cells. Louis Picker of Oregon Health and Science University believes it is likely that the enormous viral replication and extensive CD4+ memory T-cell destruction during acute infection cripples the immune system at the outset of infection and sets the stage for its eventual failure, contrary to previous views that immune competence declines slowly. “The chronic phase may simply be the progressive decompensation of system that was severely ‘wounded’ in the first weeks of infection”, he said. As this phenomenon has been shown by previous research to occur in human beings, “the major implication is that patients are likely have immune deficits right from the outset of infection”.