Project 3 - Modulation of Antiviral Immunity and T cell Exhaustion by Inhibitory Receptors

University Of Pittsburgh At Pittsburgh, Pittsburgh PA

Investigators

Linked publications, trials & patents

Abstract

CD8+ T cell exhaustion is central to chronic infections, cancer, and autoimmunity. High expression of the inhibitory receptors (IR) PD1 and LAG3 is a central feature of exhausted CD8+ T cells (Tex), and these IRs have emerged as major clinical targets. Nevertheless, not all patients treated with IR targeting therapies have durable benefit, and the molecular mechanisms connecting PD1 and LAG3 to downstream changes in CD8+ T cell differentiation and function are unclear. Indeed, there are fundamental gaps in knowledge about how these IRs control antiviral CD8+ T cells. These gaps include defining the role of these IRs on different subsets of antiviral CD8 T cells, discovering how synergy between PD1 and LAG3 functions, and determining how PD1 and LAG3 regulate chimeric antigen receptor (CAR) T cells compared to conventional T cells given the distinct architecture of a CAR versus a T cell receptor. Moreover, most data that exist on how PD1 and LAG3 control antiviral CD8 T cell biology in vivo are generated several weeks after loss-of-function and the early primary molecular circuits remain unknown. Moreover, we lack understanding of which of these changes associated with PD1 and/or LAG3 loss-of-function are causal. Project 3 will address these questions for antiviral CD8+ T cells. Thus, our central hypothesis is that PD1 and LAG3 engage distinct proximal molecular circuits in different subsets of antiviral effector-phase CD8+ T cells and, during established chronic infection, Tex cells and that testing causality of these changes will reveal new mechanisms by which these IRs control antiviral CD8+ T cell biology. AIM 1: What causal circuits downstream of PD1 and/or LAG3 control subsets of antiviral effector-phase CD8+ T cells during the first week of acute or chronic infection? PD1/LAG3 are expressed by different subsets of antiviral effector-phase CD8+ T cells. Yet the molecular mechanisms by which these IRs, separately or together, contribute to differentiation, function, and downstream lineage development are unknown. We hypothesize that applying transcriptionally guided, focused CRISPR screens will define the causal circuits and mechanisms underlying the role of PD1/LAG3 on different subsets of effector phase antiviral CD8+ T cells. AIM 2: What causal circuits downstream of PD1 and/or LAG3 control subsets of antiviral CD8+ Tex cells? Preliminary data reveal distinct, proximal transcriptional circuits engaged by PD1 pathway blockade for the three main Tex subsets: TexProg, TexInt, and TexTerm, yet the causality and downstream mechanisms are unknown. We will test the hypothesis that casual pathways and molecular mechanisms of PD1/LAG3 and their synergy for different subsets of Tex will be discovered using transcriptionally guided, focused CRISPR screens and cellular lineage tracing experiments. IR-PPG Interactions: Since the central molecular program of exhaustion is conserved in chronic viral infections, tumors, and autoimmunity, P3 will connect extensively with P1 and P2 and extensively used Cores A-D to dissect the nature of T cell exhaustion and the role of PD1/LAG3 across diseases. .