Unlike experiments that utilised R5 EGFP HIV, when experiments were performed with an X4 EGFP reporter virus, latent infection was detected in the resting CD4+ T cells cultured alone (87 (51, 155) EGFP+ cells/104 cells; n = 4; Fig. 2 F). This evidence concerns the gene CD4 and disease arising from reactivation of latent virus.