The virus titer was calculated within each individual experiment using the method of Reed and Muench [12] . In the virus dilution series, doses ranged between those infecting all cultures (100%) to those infecting none (0%). Wells giving an OD.0.3, against a background of 0.03-0.05 in the ELISA, were considered to be infected. The infectious virus titer was calculated following virus incubation with mAb/plasma. The reduction in titer was calculated as a percentage of the virus titer following exposure to either IgG or plasma which was pooled from 100 HIV-1 negative donors. Purified IgG from this pool was used as the control for mAbs. Correlations were calculated using the Spearman Rank correlation test using Prism version 5.0. Differences or correlations between sets of data were considered significant if p#0.05 and r.0.5.