Infectivity of various HIV-1 strains containing the gp41 N616Q glycan deletion. C8166 (A) and U87.CD4.CXCR4.CCR5 (B) cells were infected with WT and mutant gp41 virus particles of strains NL4.3, IIIB, HE and ADA. After 3 and 5 days respectively, viral infectivity was determined using flow cytometric detection of eGFP expression in the infected cells. The HIV-1HXB2 amino acid numbering was used (N616Q), which corresponds to N614Q in HIV-1NL4.3, N616Q in HIV-1IIIB, N603Q in HIV-1HE and N628Q in HIV-1ADA. Data are the means ± SEM of 2 independent experiments. The difference between WT and mutant gp41 virus was considered to be significant when the p value calculated using the student’s t-test was <0.05 (* = p < 0.05, ** = p < 0.005).