FIG. 1.

Reactivities of anti-F monoclonal antibodies with escape mutants of the Long strain. Each monoclonal antibody (MAb) was tested with an enzyme-linked immunosorbent assay (ELISA) using as the antigen extracts of HEp-2 cells (12) infected with the different escape mutants listed at the top. Antibodies included in antigenic areas I, II, and IV were classified previously by their competition for antigen binding (12) and reactivities with escape mutants (2). Mutants resistant to antibodies 47F, AK13A2, 7C2, B4, 19, and 20 have been described previously (2). Antibody 7.957 and those below it on the chart have also been described elsewhere (30). Viruses resistant to antibodies 7.936 and 9.432 are new to this study. Absorbance results: ▪, >75% of the value obtained with Long-infected cell extracts; ▨, between 25 and 75%; □, <25%.