Modulation of the subcellular localization of T-bet and Eomes alters CD8 exhaustion during chronic LCMV infection

Abstract Following acute viral infection, effector CD8 T-cells (TE) differentiate into long-lived memory cells (TMEM) required for secondary viral clearance. Due to persisting antigen in chronic infection, rather than differentiating into TMEM, TE progressively lose their functional abilities and become exhausted (TEX), expressing high levels of the inhibitory receptor PD1. Differentiation into TE, TMEM, and TEX is driven by transcription factors including T-bet and Eomes. In TMEM, T-bet represses PD1 while Eomes drives memory formation. In PD1+ TEX, T-betand Eomes are also expressed leading to the question of how these factors are able to play differing roles in TMEM and TEX. Using the LCMV infection model, we show that T-bet and Eomes are differentially localized during acute and chronic infection where T-bet is more cytoplasmic and Eomes is more nuclear during chronic Clone 13 infection compared to Armstrong. Additionally, nuclear T-bet in TMEM is associated with low PD1 and nuclear Eomes correlates with high PD1 in TEX. Interestingly, a higher Eomes to T-bet ratio in the nucleus correlates with TEX and blocking PD1 during chronic infection reverses this ratio. We also found that post aPD1-treated tumor-infiltrating lymphocytes from human melanoma patients have more T-bet in the nucleus compared to Eomes. Taken together, these data suggest the subcellular localization of T-bet and Eomes impacts exhaustion: nuclear Eomes is associated with high PD1 and nuclear T-bet correlates with low PD1. Importantly, these data also reveal the ratio of nuclear Eomes to T-bet influences CD8 TMEM and TEX formation and blocking PD1 signaling impacts T-bet and Eomes localization suggesting that dampening its expression might be key to reversing exhaustion.