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Defining molecular circuits of CD8+ T cell responses in tissues during latent viral infection

ABSTRACT: Latent viral infections rely on a precise coordination of the immune response to control sporadic viral reactivation. CD8+ T cells play a crucial role in controlling viral latency by generating diverse memory responses in an epitope-specific manner. Among these distinct responses, conventional and inflationary memory responses have been described during herpesvirus infections. Using a newly generated T cell receptor transgenic mouse strain, we investigated the transcriptomic and epigenetic remodeling of distinct epitope-specific CD8+ T cells during cytomegalovirus (CMV) infection across tissues at both population and single-cell levels. Our findings reveal that whereas the transcriptomic and epigenetic landscape of conventional and inflationary memory responses diverge in the spleen and liver, these molecular programs converge in the salivary gland, a site of CMV persistence. Thus, we provide evidence that the dynamics of memory CD8+ T cell responses are nuanced and exquisitely distinct between tissues.

ORGANISM(S): Mus musculus

PROVIDER: GSE291432 | GEO | 2025/05/01

REPOSITORIES: GEO

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Project description:Reconstitution of cytomegalovirus (CMV)-specific immunity following transplant remains a primary clinical objective to prevent CMV disease, and adoptive immunotherapy of CMV-specific T cells can be an effective therapeutic approach. Due to the persistence of CMV, most CMV-specific CD8+ T cells become terminally differentiated effector cells (TEFF). However, a minor subset retains a memory phenotype (TM). Interestingly, recent studies suggest that CMV-specific CD8+ T cells with different phenotypes may have different abilities to reconstitute sustained immunity following transfer. The immunology of human CMV (HCMV) infections is reflected in the mouse model of MCMV infection. We found that HCMV- and MCMV-specific T cells displayed shared genetic programs, validating the MCMV model for studies of CMV-specific T cells in vivo. After transfer, the proliferative capacity of MCMV-specific TM cells was vastly superior to TEFF cells. Strikingly, TM cells expanded and established sustained and diverse T cell populations even after multiple challenges. Although both TEFF and TM cells could protect Rag-/- mice, only TM cells could consistently survive after transfer into immune replete, latently infected recipients and respond if recipient immunity was lost. These data show that CMV-specific TM cells retain memory function during persistent infection and can re-establish CMV immunity when necessary. C57BL/6 mice were infected intraperitoneally (i.p.) with MCMV strain MW97.01 between 6-16 weeks of age. Splenocytes were isolated from chronically-infected mice and co-stained with three PE-conjugated tetramers loaded with the antigenic peptides from M38, m139 and IE3, all of which promote memory inflation. Cells were then stained with fluorescently conjugated antibodies and sorted on a MoFlo cell sorter. Naïve CD8+ cells were identified as CD44lo. MCMV-specific T cells were identified as CD8+, CD44hi and tetramer binding and then further segregated into memory and effector cells subsets by their expression of KLRG1 and CD127.

Project description:The avidity of the T-cell receptor (TCR) for antigenic peptides presented by the MHC (pMHC) on cells is an essential parameter for efficient T cell-mediated immunity. Yet, whether the TCR-ligand avidity can drive the clonal evolution of virus antigen-specific CD8 T cells, and how this process is determined in latent Cytomegalovirus (CMV)- against Epstein-Barr virus (EBV)-mediated infection remains largely unknown. Here, we quantified monomeric TCR-pMHC dissociation rates on CMV- and EBV-specific individual TCR-alpha-beta clonotypes and polyclonal CD8 T cell populations in healthy donors over a follow-up time of 15-18 years. Within CMV/pp65-specific T cell repertoires, a progressive contraction of clonotypes with high TCR-pMHC avidity and low CD8 binding dependency was observed, leading to an overall avidity decline during long-term antigen exposure. We identified a unique transcriptional signature preferentially expressed by high-avidity CMV/pp65-specific T cell clonotypes, including the inhibitory receptor LILRB1. Interestingly, T cell clonotypes of high-avidity showed higher LILRB1 expression than the low-avidity ones and LILRB1 blockade moderately increased T cell proliferation. Similar findings were made for CD8 T cell repertoires specific for the CMV/IE-1 epitope. There was a gradual in vivo loss of high-avidity T cells with time for both CMV specificities, corresponding to virus-specific CD8 T cells expressing enhanced LILRB1 levels. In sharp contrast, the EBV/BMFL1-specific T cell clonal composition and distribution, once established, displayed an exceptional stability, unrelated to TCR-pMHC binding avidity or LILRB1 expression. Together, these findings reveal an overall long-term avidity decline of CMV- but not EBV-specific T cell clonal repertoires, highlighting the differing role played by TCR-ligand avidity over the course of these two latent herpesvirus infections. Our data suggest that the inhibitor receptor LILRB1 potentially restricts the clonal expansion of high-avidity CMV-specific T cell clonotypes during latent infection. We propose that the mechanisms regulating the long-term outcome of CMV- and EBV-specific memory CD8 T cell clonotypes in humans are distinct.

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Defining molecular circuits of CD8+ T cell responses in tissues during latent viral infection

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