HNP-1 synergizes with neutralizing antibodies to gp41 and with HIV serum in inhibiting HIV-1 fusion.

HXB2 pseudoviruses were pre-bound to human PBMCs in the cold, and fusion was initiated in the absence or in the presence of indicated antibodies by shifting to 37°C. Data are normalized to the extent of fusion (measured by the BlaM assay) in the absence of defensin or antibodies (control). Addition of 24 µM HNP-1 in HBSS with 10% human serum did not affect HXB2 fusion. The following concentrations of antibodies were used: D5 (25 µg/ml), bF-3674 (12 µg/ml), 2F5 (2.5 µg/ml), PG9 (20 µg/ml). HIV-1 neutralizing serum was diluted 1∶15 prior to adding to cells. Experiments were performed either in the absence (black bars) or in the presence (red bars) of 24 µM HNP-1 in 10% human serum. Experiment with 3 µM C52L were used as a negative control. Data points are means and SEM from two independent experiments (D5, bF-3674 and HIV serum) or a representative experiment (PG9 and 2F5) performed in triplicate. **, P<0.005; ***, P<0.001 based on the two-tailed t-test.