CD8+ T cells in chronic viral infections like HIV develop functional defects such as loss of IL-2 secretion and decreased proliferative potential that are collectively termed exhaustion1. Exhausted T cells express increased levels of multiple inhibitory receptors, such as Programmed Death 1 (PD-1). PD-1 inhibition contributes to impaired virus-specific T cell function in chronic infection because antibody-mediated blockade of its ligand, Programmed Death Ligand 1 (PD-L1) is sufficient to improve T cell function and reduce viral replication in animal models. Reversing PD-1 inhibition is therefore an attractive therapeutic target, but the cellular mechanisms by which PD-1 ligation results in T cell inhibition are not fully understood. PD-1 is thought to limit T cell activation by attenuating T cell receptor (TCR) signaling. It is not known whether PD-1 ligation also acts by upregulating genes in exhausted T cells that impair their function. Here, we analyzed gene-expression profiles from HIV-specific CD8+ T cells in patients with HIV and show that PD-1 coordinately upregulates a program of genes in exhausted CD8+ T cells from humans and mice. This program includes upregulation of basic leucine transcription factor, ATF-like (BATF), a transcription factor in the AP-1 family. Enforced expression of BATF was sufficient to impair T cell proliferation and cytokine secretion, while BATF knockdown reduced PD-1 inhibition. Silencing BATF in CD4+ and CD8+ T cells from chronic viremic patients rescued HIV-specific T cell function. Thus inhibitory receptors can cause T cell exhaustion by upregulating genes – such as BATF – that inhibit T cell function.

We sorted HIV-specific CD8+ T cells from 18 progressors and 24 controllers, cohorts with a two-log difference in mean viral load