Different virus-precipitating activities of neutralizing monoclonal antibodies that recognize distinct sites of poliovirus particles.

Two neutralizing monoclonal antibodies (4 C 4 and 4 F 2) against type 1 poliovirus, Mahoney strain, recognized distinct antigenic sites of the virus particles; 4 C 4 antibody bound to vertices of native and heated (56 degrees C, 30 minutes) virus of Mahoney strain, while 4 F 2 antibody reacted with specific surface protrusions of native virus of Mahoney and Sabin strains. The difference in the location of neutralization epitopes with which the two antibodies react was confirmed in the neutralization reaction by the use of mutants resistant to 4 C 4 and 4 F 2 antibody. In immune electron microscopy, double immunodiffusion and sucrose density gradient analysis of virus-antibody complexes, the two antibodies showed a marked difference in their virus-precipitating activities. The 4 C 4 antibody recognizing vertices of the virus particle had little virus-precipitating activity. In contrast, the 4 F 2 antibody that bound to specific surface protrusions of native virus aggregated virus particle efficiently. In neutralization assays, however, the 4 C 4 antibody exhibited a slightly stronger neutralizing activity than the 4 F 2 antibody. Thus, it was suggested that the strength in precipitating activities of the two antibodies did not correlate with that in their neutralizing activities.