One cycle infection assay was carried out using normalized pseudoviruses as described previously [20] . Briefly, Jurkat cells (0.5610 6 ) were infected with viral supernatants containing 250 ng p24, which was measured by Vironostika HIV-1 antigen MicroELISA kit (Biomerieux bv Boxtel, Netherlands). The virus and cells mixture was spun at 1,800 g at 30uC for 2 h. After the 2h spin infection, Jurkat cells were washed with 2 ml culture medium twice, then cultured in 24-well plates at 37uC for 48 h. The cells were collected and washed twice with PBS. After the cells were fixed with 1% paraformaldehyde in PBS for 30 min on ice, the infected cells, as determined by the expression of GFP, were measured using a FACSCalibur instrument (Becton Dickinson, USA) and analyzed with Cell Quest software (Becton Dickinson, USA) as described previously [20] .