Peak SIV replication in resting memory CD4+ T cells depletes gut lamina propria CD4+ T cells

Two papers in this issue shed light on the early stages of HIV infection. HIV gradually infects and destroys disease-fighting CD4+ T cells in the blood, but also causes loss of CD4+ T cells from mucosal surfaces such as the gut in the initial infection phase. Studies in monkeys infected with simian immunodeficiency virus (SIV) now show that the virus infects and kills memory CD4+ T cells, a T-cell subset responsible for remembering previous infections. Mattapallil et al. found that SIV infects about 50% of memory CD4+ T cells within days of infection. Li et al. show that as well as killing by direct infection, the virus triggers uninfected cells to self-destruct via apoptosis. These findings have clinical implications, stressing the need to reduce viral load at the early stage of infection.