SIV attacks memory cells

PROFESSORS PIETRO M. MOTTA © TOMONORI NAGURO / PHOTO RESEARCHERS

The paper:

The finding:

Simian immunodeficiency virus (SIV) and HIV are known to reduce CD4+ T cells dramatically. Research by Mario Roederer at the National Institute of Health and his colleagues showed that this happens during acute infection, suggesting that this is an important time to reduce viral load therapeutically.

The follow-up:

CD4+ T cells in SIV-infected infant macaques have the same rate of depletion, according to in press work by Ronald Veazey at Tulane University. What's surprising, he says, is the substantial amount of CD4+ T cells in uninfected infants, perhaps suggesting that "the immune system is cranked up very early after birth."

The application:

Roederer's team reported in 2006 that vaccination reduces CD4+ T cell depletion during acute SIV infection in monkeys, a protection that predicts lifespan. CD4+ T cell counts, he says, can be used as a marker to test the efficacy of vaccines. (See story, p. 46)

Roederer's question:

"Why is it that during the acute phase such a large fraction of memory cells can be infected and destroyed but a few months later, the infection rate is very slow?"