Figure 4

Reverse transcriptase Inhibitors are less effective inhibitors of HIV-1 cell-to-cell spread compared to cell-free infection. Uninfected target cells were incubated with serial dilutions of A) Nevirapine (NVP), B) Zidovudine (AZT) or C) Tenofovir (TDF) for 1 h and mixed with an equal number of HIV-1 infected donor cells. At 24 h post-mixing, the DNA was extracted and cell-cell spread was measured by qPCR as described in Figure 1. For cell-free infection, virus-containing supernatant harvested from infected donor cells was used to infect target cells in the presence of a serial dilution of the relevant RTI. At 24 h post-infection, the target cells were pelleted, DNA extracted and qPCR was performed. The dose–response curves for both cell-free and cell-to-cell modes of spread were plotted for each drug and curves fitted. Data shown are a representative of three independent experiments. Error bars represent the SD of the mean of triplicates. D) Reducing the virus MOI restores the ability of TDF to inhibit cell-to-cell spread. Co-cultures using ten-fold fewer donor cells were performed in the presence of a high, intermediate (IC50) and low dose concentration of TDF. Data show the means of triplicates and error bars represent the SD of the mean, **** P<0.0001, *** P < 0.001, ns: not significant, Two-way ANOVA with Bonferroni post-test.