Neisseria spp. potently induce HIV-1 LTR expression in CD4+ T cells. HIV-1 LTR expression in Jurkat 1G5 CD4+ T cells was quantified by luciferase assay. Data represent the fold induction of expression over uninfected cells. (A) TLR5 neutralization. Jurkat 1G5 cells were preincubated with no antibody (black bars), with anti-TLR5 (gray bars), or with isotype control (white bars). Data shown are the average of triplicate samples ± SD, representing three experiments. *P < 0.05; ANOVA, Bonferroni. (B) The potent HIV-1 LTR induction effect is unique to infection with Neisseria spp. MOI = 10. Data shown are the mean of three independent experiments ± SEM. *P < 0.05; ANOVA, Dunnett. (C) The HIV-1 LTR induction effect is a common among Neisseria spp. Jurkat 1G5 cells were either grown in 75% (vol/vol) culture supernatants (white bars) or infected with an MOI = 10 (black bars). Data shown are the mean of three independent experiments ± SEM. *P < 0.05; ANOVA, Bonferroni. Ec, E. coli; Nl, N. lactamica; Ui, uninfected.