Protective function of ex vivo-expanded CD8 T cells in a mouse model of adoptive therapy for cytomegalovirus infection depends on integrin beta 1 but not CXCR3, CTLA4, or PD-1 expression.

The adoptive transfer of virus-specific T cells (VSTs) represents a therapeutic option for viral infection treatment in immunocompromised patients. Before administration, ex vivo culture enables VST expansion. However, it is unclear how ex vivo expansion affects the circulation, homing, and intra-tissue migration of administered VSTs. We established a model of VST immunotherapy of acute cytomegalovirus infection using adoptive transfer of ex vivo-expanded OT-I CD8 T cells (recognizing SIINFEKL peptide) into Rag2-/- mice infected with murine cytomegalovirus (MCMV) encoding for the SIINFEKL peptide. Ex vivo expansion induced an effector T cell phenotype and affected the expression of integrins and chemokine receptors. CRISPR/Cas9-mediated gene deletions enabled us to address the role of selected genes in the homing of VSTs following intravenous administration. We found that deletion of Itgb1, encoding for integrin beta 1, prevented OT-I cells from entering infected organs and drastically reduced their number in blood, suggesting that adoptively transferred VSTs primarily expand in the infected tissues. By contrast, Cxcr3-/- OT-I cells provided equal protection as their Cxcr3+/+ counterparts, indicating that this chemokine receptor does not contribute to VST entry into infected organs. Further, Pdcd1 and Ctla4 deletion did not impair the transferred OT-I cells' ability to protect mice from MCMV, arguing against quick exhaustion of VSTs with an effector T cell phenotype. Together, these data indicate that ex vivo expansion affects migration and activation properties of VSTs and suggest that future clinical evaluation of adoptive T cell therapy efficacy should include homing molecule expression assessment.