Pd-1 Blockade And Vaccination Provide Therapeutic Benefit Against Siv By Inducing Broad And Functional Cd8(+) T Cells In Lymphoid Tissue

During antiretroviral therapy (ART), most of the human immunodeficiency virus (HIV) reservoirs persist in the B cell follicles (BCFs) of lymphoid tissue. Thus, for HIV cure strategies, it is critical to generate cytolytic CD8(+) T cells that home to BCF, reduce the reservoir burden, and maintain strong antiviral responses in the absence of ART. Here, using a chronic simian immunodeficiency virus (SIV)/rhesus macaque model, we showed that therapeutic vaccination under ART using a CD40L plus TLR7 agonist-adjuvanted DNA/modified vaccinia Ankara vaccine regimen induced robust and highly functional, SIV-specific CD4(+) and CD8(+) T cell responses. In addition, the vaccination induced SIV-specific CD8(+) T cells in the lymph nodes (LNs) that could home to BCF. Administration of PD-1 blockade before initiation of ART and during vaccination markedly increased the frequency of granzyme B+ perforin(+) CD8(+) T cells in the blood and LN, enhanced their localization in germinal centers of BCF, and reduced the viral reservoir. After ART interruption, the vaccine + anti-PD-1 antibody-treated animals, compared with the vaccine alone and ART alone control animals, displayed preservation of the granzyme B+ CD8(+) T cells in the T cell zone and BCF of LN, maintained high SIV antigen-recognition breadth, showed control of reemerging viremia, and improved survival. Our findings revealed that PD-1 blockade enhanced the therapeutic benefits of SIV vaccination by improving and sustaining the function and localization of vaccine-induced CD8(+) T cells to BCF and decreasing viral reservoirs in lymphoid tissue. This work has potential implications for the development of curative HIV strategies.