Innate sensing of WT or Vpu-defective HIV-infected T cells requires Env-dependent viral fusion and is largely dependent on TLR7.

<p>MT4 cells were mock-infected (m) or infected with GFP-encoding NL4.3 variants (WT or dU) as indicated. <b>(A-B)</b> Cells were left un-treated (no Tx) or were treated with T-20 prior to co-culture with PBMCs. To assess the effect of inhibiting reverse transcription, PBMCs were treated with 3TC prior to co-culture with infected MT4 cells. As a positive control, CpG was added to inhibitor-treated or untreated mock-infected cells. A representative example of absolute levels <b>(A)</b> or relative percentages <b>(B)</b> of IFN-I detected after co-culture of WT or dU HIV-infected MT4 cells with PBMCs in the presence or absence of inhibitors are shown. Results are expressed relative to values obtained in the no-Tx samples (n = 8). <b>(C-F)</b> PBMCs were pre-treated with either TLR9 or TLR7/8/9 antagonists (antag.) or their respective controls (antag. Ctrl) prior to TLR agonist treatment <b>(C-D)</b> or to co-culture with the indicated infected cells <b>(E-F)</b>. A representative example of absolute levels of IFN-I detected after treatment with either TLR9 agonist (CpG-A) <b>(C)</b> or TLR7 agonist (R848) <b>(D)</b> is shown. A representative example of absolute levels <b>(E)</b> or relative percentages <b>(F)</b> of IFN-I produced in the indicated co-cultures in the presence of TLR antagonists or controls are shown. The amount of IFN-I released by PBMCs in contact with dU HIV-infected cells in the presence of the TLR7/8/9 antagonist control was set at 100% (n = 3). Two-tailed paired <i>t</i>-test was used. (*** p<0.001, * p<0.05, ns not significant (p>0.05)). Error bars represent SD.