Figure 4.

Detection of anti-RSV antibodies using LIPS-G_A and -G_B assays versus plaque reduction neutralization (PRN) testing. Human immune globulin (huIgG, BEI NR-21973) was used neat or serially diluted 10-fold into IgΔ from 10% to 0.00001% IgG. Samples were tested in triplicate in immunoprecipitation assays and in duplicate in plaque reduction neutralization assays against Ruc-G_A antigen and RSV-A2, respectively (panel A) or against Ruc-G_B antigen and RSV-B1, respectively (panel B). The results of testing in the immunoprecipitation assay are shown by the black lines in each figure. Cutoff values for a positive result in the immunoprecipitation assays were five standard deviations above the mean value of the negative control (IgΔ) and are shown as horizontal red (Ruc-G_A) and blue lines (Ruc-G_B). In the PRN test, a reduction in the mean plaque count of ≥50% (in wells containing huIgG) relative to the mean plaque count seen in virus control wells (in the absence of huIgG) was considered significant.