A receptor on human immune cells that normally detects virus infections can be “switched off” due to HIV-1 infection. These findings, reported online this week in Nature Immunology, may help in our understanding of how HIV goes undetected by the immune system.

David Hafler and colleagues find that when TLR7, a receptor on human CD4+ T immune cells, is triggered they become unresponsive. CD4+ T cells are the primary targets for HIV-1 and are typically deactivated following infection. The authors report that in the absence of TLR7, the responsiveness of these immune cells can be restored. Furthermore, human CD4+ T cells lacking TLR7 also show reduced infection by HIV-1 in vitro. HIV-1 therefore seems to co-opt TLR7 for its normal life-cycle and uses it to deactivate a key cell of the immune system.