Selective Targeting of the PD-1+ HIV/SIV reservoir with novel anti-PD-1 chimeric antigen receptor T cells

/Abstract Human immunodeficiency virus infects cells of the immune system and, if left untreated leads to the development of acquired immunodeficiency syndrome and death. With the advent of antiretrovirals, HIV infection has turned into a chronic infection. However, tools and therapeutics to dissect and deplete SIV/HIV latent reservoirs during combination antiretroviral therapy (ART) to interrogate their importance in defining reservoir dynamics are limited and are a focus of this application. Programmed cell death protein 1 (PD-1) is an immune checkpoint protein expressed on latently infected CD4 T cells and in particular T follicular helper (TFH) cells. TFH cells reside in the germinal centers and are enriched with replication-competent human immune deficiency virus 1 (HIV) provirus in people with HIV. Our proposal builds upon the pre-clinical work we performed in non-human primates in which we demonstrated that anti-PD1 chimeric antigen receptor T cells eliminated all detectable PD-1 expressing TFH cells; the first time the elimination of this reservoir of HIV has been reported. Moreover, it also depleted memory CD8+ T cells leading to accelerated disease progression. Here, we engineered novel CAR T cell modalities that are either controllable through an NS3 ON switch modulated by a small molecule inhibitor (Grazoprevir; GZV) or are a more specific CAR by integrating it into a LINK CAR platform that allows true Boolean AND gating by targeting CD4 and PD-1. Ultimately, we will combine these T-cell engineering strategies and build CAR T cells with higher safety and specificity, that are equally suitable for HIV cure interventions as wells as tools for CAR T cell-mediated depletion of cell subsets in the RM model. This will allow to deplete PD-1+ T cells or PD-1+ CD4+ T cell subsets temporarily and selectively. Initially, we will optimize these new CAR modalities in adoptive transfer experiment in uninfected rhesus macaques (RM). These experiments will show strong association of GZV plasma levels with expansion and collapse of the CAR T cell population, which will dovetail with depletion of PD- 1+ cells when CAR T cells are expanding. We will study whether immune reconstitution occurs after temporary PD-1- targeted deletion after cessation of GZV administration by following T cell dynamics and performing vaccination post-CAR T cell infusion. Subsequently, we will use these novel CAR T cells as tools to dissect the role of PD-1 in reservoir dynamics during ART. We will compare temporary and continuous depletion of total PD- 1+ as well as PD-1+ CD4+ T cells. Specifically, it is of interest how PD-1 depletion will affect the latent reservoir in terms of SIV intact proviral genomes. This project has the potential to substantially advance the utility of CAR T cells to dissect the pathology of SIV/HIV and reservoir dynamics in the nonhuman primate model to study the specific role of PD-1 during ART. It will inform and provide new strategies and targets for an HIV cure. Project Number: 1R01AI195020-01 | Fiscal Year: 2025 | NIH Institute/Center: National Institute of Allergy and Infectious Diseases (NIAID) | Principal Investigator: Karsten Eichholz | Institution: FRED HUTCHINSON CANCER CENTER, SEATTLE, WA | Award Amount: $862,398 | Activity Code: R01 | Study Section: Special Emphasis Panel[ZRG1 DCAI-D (03)] View on NIH RePORTER: https://reporter.nih.gov/project-details/1R01AI19502001