Reeg, D. B. | Search bioRxiv

bioRxiv2026

Persistently activated virus-specific CD8 T cells indicate antigen-driven immune aberrations in long COVID

Long COVID (LC) affects millions of people worldwide, yet its driving mechanisms remain incompletely defined and no treatment has been approved. Persistence of SARS-CoV-2 and reactivation of herpesviruses have been implicated in LC, but direct detection of these viral antigens in blood and tissues has been challenging. T cells are exquisitely sensitive to viral antigens, survey organs throughout the body, and can be readily sampled in peripheral blood. Using high-dimensional spectral flow cytometry and single-cell sequencing approaches with multiplexed peptide/HLA tetramers, we profiled virus-specific T cells from hundreds of people with LC and recovered controls. We identified a subset of people with LC that maintained elevated activation of CD8 T cells targeting SARS-CoV-2 spike and/or lytic antigens from Epstein-Barr virus, but not other viral specificities. Spike-specific cells in LC expressed genes linked to TCR stimulation, terminal effector differentiation, and exhaustion and demonstrated reduced functionality upon cognate peptide stimulation ex vivo. Thus, T cells from a subset of people with LC are likely chronically stimulated by persistent SARS-CoV-2 antigens. These findings establish the use of T cells as biosensors of persisting antigen in LC and other disease settings and may help develop new therapeutic strategies for LC.

immunology↗

bioRxiv2025

Divergent ontogeny of Tissue Resident Memory and Tissue Resident Exhausted CD8+ T cells underlies distinct functional potential

Persistent antigen stimulation promotes differentiation of exhausted CD8+ T (TEX) cells. TEX cells are distinct from circulating memory T (TCIRCM) cells but share many features with tissue-resident memory (TRM) cells established following infection resolution. CD8+ T cells co-expressing residency- and exhaustion-associated molecules in chronic diseases often correlate with clinical outcomes. However, the relationship between these cells and conventional TRM or TEX cells remains unclear. Here, we show that chronic antigen stimulation drives development of tissue-resident TEX (TR-TEX) cells that are ontologically and functionally distinct from TRM cells generated after antigen clearance. TR-TEX phenotypically resembled TRM cells but were regulated by distinct transcriptional networks and were uniquely dependent on Tox for residency programming. Although TEX progenitor cells acquired residency features upon entering chronically infected tissues, they failed to generate conventional TRM cells after antigen withdrawal. Conversely, TRM cells were able to differentiate into TEX cells during chronic antigen stimulation. Deriving cell-state specific transcriptional signatures revealed a selective association of TR-TEX cells with patient responses to immune checkpoint blockade, and only TR-TEX but not TRM cells responded to PD-1 pathway inhibition in vivo. These data suggest that TR-TEX and TRM cells are developmentally distinct cell types that share a tissue-residency program but have distinct roles in disease control.

immunology↗