Studies on neutralization of Japanese encephalitis virus (JEV). I. Further neutralization of the resistant virus fraction by an interaction between antivirus IgG antibody and IgG heterotype or allotype antibody.

When JE viruses interact with anti-JEV mouse IgG antibody (anti-JEV antibody), a resistant virus fraction remains which is not neutralized further by the antibody. This resistant virus fraction was neutralized by anti-mouse IgG rabbit IgG antibody (heterotype antibody) or anti-mouse IgG mouse IgG antibody (allotype antibody). The kinetics of this secondary neutralization was of the first order, as was that of the first neutralization by anti-JEV antibody. The rate of the secondary neutralization was proportional to the concentration of the heterotype or allotype antibody. The first neutralization could be reversed in part by dilution, and the susceptibility of the resistant virus fraction to anti-JEV antibody was increased upon dilution. On the contrary, the susceptibility of the resistant virus fraction to the heterotype or allotype antibody decreased with dilution. These findings suggested that the secondary neutralization of the resistant virus fraction was resulted in the interaction between reversibly combined anti-JEV antibody and the heterotype or allotype antibody.