CXCR5-dependent entry of CD8 T cells into rhesus macaque B-cell follicles achieved through T-cell engineering

Follicular helper CD4 T cells, T_FH, residing in B-cell follicles within secondary lymphoid tissues, are readily infected by AIDS viruses and are a major source of persistent virus despite relative control of viral replication. This persistence is due at least in part to a relative exclusion of effective antiviral CD8 T cells from B-cell follicles. To determine whether CD8 T cells could be engineered to enter B-cell follicles, we genetically modified unselected CD8 T cells to express CXC chemokine receptor 5 (CXCR5), the chemokine receptor implicated in cellular entry into B-cell follicles. Engineered CD8 T cells expressing human CXCR5 (CD8^hCXCR5) exhibited ligandspecific signaling and chemotaxis in vitro. Six infected rhesus macaques were infused with differentially fluorescent dye-labeled autologous CD8^hCXCR5 and untransduced CD8 T cells and necropsied 48 h later. Flow cytometry of both spleen and lymph node samples revealed higher frequencies of CD8^hCXCR5 than untransduced cells, consistent with preferential trafficking to B-cell follicle-containing tissues. Confocal fluorescence microscopy of thin-sectioned lymphoid tissues demonstrated strong preferential localization of CD8^hCXCR5 T cells within B-cell follicles with only rare cells in extrafollicular locations. CD8^hCXCR5 T cells were present throughout the follicles with some observed near infected T_FH. In contrast, untransduced CD8 T cells were found in the extrafollicular T-cell zone. Our ability to direct localization of unselected CD8 T cells into B-cell follicles using CXCR5 expression provides a strategy to place highly effective virus-specific CD8 T cells into these AIDS virus sanctuaries and potentially suppress residual viral replication.