CXCL17 Chemokine-Dependent Mobilization of CXCR8⁺CD8⁺ Effector Memory and Tissue-Resident Memory T Cells in the Vaginal Mucosa Is Associated with Protection against Genital Herpes.

Circulating conventional memory CD8⁺ T cells (i.e., the CD8⁺ effector memory T [T_EM] cell and CD8⁺ central memory T [T_CM] cell subsets) and the noncirculating CD8⁺ tissue-resident memory T (T_RM) cell subset play a critical role in mucosal immunity. Mucosal chemokines, including the recently discovered CXCL17, are also important in mucosal immunity because they are homeostatically expressed in mucosal tissues. However, whether the CXCL17 chemokine contributes to the mobilization of memory CD8⁺ T cell subsets to access infected mucosal tissues remains to be elucidated. In this study, we report that after intravaginal HSV type 1 infection of B6 mice, we detected high expression levels of CXCL17 and increased numbers of CD44^highCD62L^lowCD8⁺ T_EM and CD103^highCD8⁺ T_RM cells expressing CXCR8, the cognate receptor of CXCL17, in the vaginal mucosa (VM) of mice with reduced genital herpes infection and disease. In contrast to wild-type B6 mice, the CXCL17^-/- mice developed 1) fewer CXCR8⁺CD8⁺ T_EM and T_RM cells associated with more virus replication in the VM and more latency established in dorsal root ganglia, and 2) reduced numbers and frequencies of functional CD8⁺ T cells in the VM. These findings suggest that the CXCL17/CXCR8 chemokine pathway plays a crucial role in mucosal vaginal immunity by promoting the mobilization of functional protective CD8⁺ T_EM and CD8⁺ T_RM cells, within this site of acute and recurrent herpes infection.

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