The results of flow cytometry showed that X4 HIV-1 productively infected all resting subsets, with EGFP expression in 0.50% ± 0.25% (mean ± SD) of TN cells, 1.83% ± 1.99% of CCR5− TM cells, and 1.76% ± 1.43% of CCR5+ TM cells at 3 days post-infection (Fig. 2b, c and Additional file 1). The gene discussed is CCR5; the disease is infection.