Recovered peripheral and mucosal CD4⁺ T cells are susceptible to productive X4 HIV infection. PBMC and MMC obtained 24 months after CCR5Δ32/Δ32 SCT were activated with PHA and IL-2 and then incubated with the CCR5-tropic HIV-1 strain JR-CSF or the CXCR4-tropic HIV-1 strain NL4-3 at a multiplicity of infection of 0.001. Viral replication was quantified by measuring the amount of HIV core protein p24 in the cell-free supernatants of cultures. No virus production was observed in the mock controls. Similar results were obtained with peripheral lymphocytes purified at 9.5 and 34.5 and months after CCR5Δ32/Δ32 SCT.