Cutting Edge: CCR9 Promotes CD8 + T Cell Recruitment to the Brain during Congenital Cytomegalovirus Infection.

CD8 + T lymphocytes infiltrate the brain during congenital CMV infection and promote viral clearance. However, the mechanisms by which CD8 + T cells are recruited to the brain remain unclear. Using a mouse model of congenital CMV, we found a gut-homing chemokine receptor (CCR9) was preferentially expressed in CD8 + T cells localized in the brain postinfection. In the absence of CCR9 or CCL25 (CCR9's ligand) expression, CD8 + T cells failed to migrate to key sites of infection in the brain and protect the host from severe forms of disease. Interestingly, we found that expression of CCR9 on CD8 + T cells was also responsible for spatial temporal positioning of T cells in the brain. Collectively, our data demonstrate that the CMV-infected brain uses a similar mechanism for CD8 + T cell homing as the small intestine.