PS extracts inhibit entry of HIV-1 into the host cell.

<p><i>A</i>, Comparison of time-of-addition (TOA) profiles of PS extract and reference compounds that inhibit HIV-1 entry (i.e. Griffithsin and T-20) and reverse transcription (AZT), respectively. For TOA assays, virus preparations (HIV-1_LAI) were added to LC5-RIC cells and HIV-1 inhibitors added either simultaneously with the virus (time point 0) or at later time points (h.p.i. = hours post infection) at concentrations yielding maximum inhibition (i.e. >5× EC₅₀). Cultures were assayed for reporter expression 48 hours after virus addition and fluorescent signal intensities normalized to those of cultures exposed to virus in the absence of inhibitors. Each time point was measured in triplicate. Mean values and standard deviation of the mean are indicated for each time point. <i>B</i>, Reduction of input HIV-1 viral RNA levels by treatment with PS-extract. LC5-CD4 cells were exposed to HIV-1_LA1 and Efavirenz in the presence or absence of PS extract (50 µg/ml) in triplicate samples. After 4 hours exposure time, RNA was isolated from each sample, cDNA prepared and real-time PCR performed with HIV-1 specific primers to quantify viral RNA levels. HIV-1 transcript levels were normalized to RPII. Relative expression was calculated by the −2^−ΔΔCT method. The data is expressed as fold expression of HIV-1 RNA in HIV-1 exposed/treated samples compared to unexposed/untreated samples. Columns indicate mean values and error bars the standard deviations of the means. <i>C</i>, Reduction of HIV-1 DNA loads in HIV-1-exposed PBMCs by treatment with PS extract. HIV-1 DNA levels were determined by real-time PCR in peripheral blood derived mononuclear cells treated with PS extract during exposure to HIV-1 and in untreated infected cells (analysed in triplicate samples). Columns indicate mean values and error bars the standard deviations of the means. <i>D</i>, Influence of envelope proteins on the inhibition of virus infection by PS extract. LC5-RIC cells were exposed to HIV-1 variants with different HIV-1 envelope proteins representing different virus tropisms (HIV-1_LAI: X4-tropic; HIV-1-AD-8 and HIV-1ΔEnv_JRFL(R5): R5-tropic) or HIV-1 based virus particles pseudotyped with an envelope protein (G-protein) from a heterologous virus (<i>Vesicular Stomatitis Virus</i>; HIV-1ΔEnv_VSVG) in the presence of different concentrations of PS extract. Cultures were assayed for reporter expression 48 hours after virus addition and fluorescent signal intensities normalized to those of cultures exposed to virus without inhibitors. Mean values of triplicate wells and standard deviation of the mean are indicated for each extract concentration.