The in situ analysis of HIV vRNA+ cells and CAR/CXCR5 T cells in spleen led us to discern a likely mechanism contributing to sustained VLs detected in treated animals; we surmise that HIV infection was spread by HIV-infected CD4 T cells, including a subset of CD4+ CAR/CXCR5 T cells, that were present in our product. Here, CXCR5 is linked to HIV infectious disease.