GSE168282
cDC1 retain a niche for precursor exhausted T cells during chronic viral infection
Tumors and chronic infections result in sustained antigen exposure, which promotes impaired functional responsiveness in T cells referred to as exhaustion. Checkpoint immunotherapy can induce the reinvigoration of cellular immunity by activating a recently identified precursor of exhausted T (TPEX) cell population. This activation requires cellular interactions between TPEX cells and professional antigen-presenting cells, likely conventional dendritic cells (cDC). Currently, it is unknown where cDC - TPEX cell interactions take place and which cDC subsets are involved. To address these questions, we first mapped the differentiation trajectory of TPEX cell subsets via transitory cellular states towards terminally exhausted T (TEX) cells, identified transcriptionally distinct subpopulations and defined their localization in the spleen during chronic viral infection. We found that cDC were required for TPEX cell proliferation, differentiation and viral control during PD-L1 treatment. In particular cDC1, a specialized subset of dendritic cells, colocalized with TPEX cells and regulated their maintenance by promoting the functionality of stromal cells that support TPEX cell survival. Additionally, during PD-L1 treatment, the splenic cDC1 network was significantly reorganized at the marginal zone, a site of TPEX cell differentiation. As a consequence, viral control during checkpoint immunotherapy and cellular integrity of the marginal zone depended on the presence of cDC1. Since cDC2 were sufficient to drive initial TPEX cell proliferation and TEX cell generation but not viral control, our data suggest a new concept in which cDC1 decelerate the speed of differentiation of TPEX cells via transitory cellular states and thereby generate a therapeutic window for effective immunotherapy. Together, our findings reveal how the dynamic spatial organization of the DC network supports cellular niches that guide the maintenance and differentiation of TPEX cells and opens new avenues to optimize checkpoint immunotherapy. Overall design: B/6 Mice were infected with 2x10^6 IU LCMV clone13 after 2 times CD4 T cell depletion (d2 and d0) with 300µg GK1.5 antibody. At the chronic infection phase (> d30), splenocytes were isolated and CD8+, PD-1+, Tim-3 low cells were sorted using FACS AriaIII. Treated mice were injected i.p. 200µg aPD-L1 antibody (clone 10F.9G2) 24h before sacrificing the mice. Cells were pooled form 4 mice per group.