PD-1 expression on HIV-specific T cells is associated with T-cell exhaustion and disease progression

Blocking a protein called PD-1 (programmed death 1) might provide a way to boost the immune function of T cells crippled by HIV infection. A study published earlier this year showed that blocking of PD-1 function in virally infected mice could restore the function of exhausted T cells and help fight infection. Now the phenomenon has been found to occur in humans. The T cells in HIV patients were found to have many more PD-1 receptors on their surface than is normal; the degree of PD-1 production correlates with markers of disease progression including the extent to which T cells are disabled and the levels of virus within the body. An antibody that blocks this receptor promotes the immune response to HIV in laboratory experiments, suggesting that a similar strategy might work to fight the disease in humans.