Role of PD-1 in HIV pathogenesis and as target for therapy.

Major advances in Antiretroviral Therapy (ART) have resulted in a dramatic decline in HIV-related deaths. However, no current treatment regimen leads to viral eradication or restoration of HIV-specific immune responses capable of durable viral control after cessation of ART. Thus, there is a need for novel interventions that could complement ART in order to eliminate virus or reach a state of "functional cure." It has been shown in murine models and humans that the negative co-signaling molecule programmed-death 1 (PD-1) plays an active and reversible role in mediating T-cell exhaustion in chronic infections. This review summarizes recent advances in our understanding of the PD-1 pathway in HIV infection, and the lessons learned from studies in the SIV model and cancer. We discuss the potential of immunotherapeutic interventions targeting PD-1 in order to augment immune responses or facilitate viral eradication. We also present the challenges to therapies targeting immunoregulatory networks.