Defining molecular determinants of resident memory T cell differentiation and persistence

About This Grant

PROJECT SUMMARY CD8+ resident memory T cells (TRM) play a crucial role in the defense against infection and cancer. Following antigenic challenge, TRM develop and surveil non-lymphoid tissues (NLTs) such as the liver and small intestine to provide long-lasting durable immunity. Within these NLTs, TRM progenitors initiate a universal residency program that is dependent upon induction of the homologous transcription factors BLIMP-1 and Hobit (encoded by Zfp683). These transcription factors are essential for TRM development, as they suppress the expression of egress-supporting molecules like S1PR1 to enforce residency. Although BLIMP-1 is expressed in circulating, conventional effector CD8+ T cells, Hobit expression is restricted to resident immune cells in NLTs including TRM. This suggests that Hobit uniquely facilitates TRM adaptation or survival within peripheral tissues. Despite the critical role of Hobit in TRM differentiation, the mechanism by which Hobit is induced is poorly defined. It is well known that cell-extrinsic factors—including IL-15, TGF-β, and retinoic acid—support the TRM fate; however, how these factors regulate Hobit expression remains unknown. Preliminary data demonstrate that several elements within the Zfp683 locus are accessible and bound by transcription factors downstream of these signals including T-bet, STAT5, and RUNX3. Therefore, I hypothesize that cell-extrinsic tissue cues cooperate with cis-regulatory elements in the Zfp683 locus to induce the expression of Hobit to support the TRM fate. In a preliminary experiment, ablation of one of these candidate cis-regulatory elements resulted in significantly reduced Zfp683 mRNA expression level in liver-resident CD8 T cells and led to a competitive disadvantage in generating TRM cells. Besides cell-extrinsic tissue factors, the presence of antigen and inflammation is also known to regulate TRM development. Previous studies using acute infection models such as LCMV Armstrong have demonstrated that TRM cells persist and expand in rechallenge contexts. However, little is known how persistent stimulation contexts such as chronic infection and autoimmunity influence TRM development and maintenance. Since BLIMP- 1 remains highly expressed during chronic infection but not acute infection, I hypothesize that contexts of persistent TRM activation alter the transcriptional requirement for Hobit during TRM development and persistence, since BLIMP-1 and Hobit play semi-redundant roles in TRM differentiation. Furthermore, I will dissect how antigen presence and inflammation differentially impact TRM responses using a novel model of neoantigen expression in the liver. This research proposal seeks to address critical gaps in our understanding of TRM biology by investigating (1) how cis-regulatory elements integrate tissue-specific cues to drive Hobit expression and (2) how chronic stimulation contexts impact the development and maintenance of TRM identity. By better understanding how TRM development is programmed at the molecular level, therapeutic interventions and vaccination strategies relevant to infection, cancer, and autoimmunity may be improved to further alleviate human disease.