Studies on Complement-potentiated Neutralizing Antibodies (C'-PNAb) Induced in Rabbits Inoculated with Japanese Encephalitis Virus (JEV). I. The Nature of C'-PNAb

The C'-PNAb induced by JEV grown in porcine kidney stable (PS) cells [JEV(PS)] inactivate not only the corresponding virus, hut also Western equine encephalitis (WEE), Eastern equine encephalitis (EEE), vesicular stomatitis (VS) and Sindbis viruses grown in PS cells or primary hamster kidney (HK) cell cultures in the presence of complement. The degree of complement-potentiated neutralizing (C'-PN) ability varies for each virus. The C'-PNAb do not, inactivate these viruses grown in mouse brain, even JEV. The C'-PN activity against viruses other than JEV(PS) is completely removed by absorption with the microsomal fraction of PS or HK cells, but not of mouse brain. The antibodies in fraction IgM induced by the microsomal fraction of PS or HK cells inactivate the viruses grown in PS cells to a different degree in the presence of complement, but not viruses grown in mouse brain. The activity of C'-PNAb against JEV(PS) is reduced to 2% of the original activity by absorption with sheep red cells. After absorption, the remaining C'-PNAb are not further reduced by absorption with the microsomal fraction of PS cells, nor do they inactivate the other viruses grown on PS cells. The early rabbit hemagglutination-inhibition (HI) antibodies in fraction IgM induced by JEV(PS) could not only inhibit hemagglutination with JE, WEE, EEE, and Sindbis viruses grown on PS cells in the absence of complement, but could also facilitate HI in the presence of complement. However, they could not inhibit hemagglutination with these viruses grown in mouse brain, in the presence or absence of complement. This activity of HI could also be removed by absorption with the microsomal fraction of PS cells. These findings suggest that C'-PNAb are induced by host cell components associated with the virus, and that the early HI antibodies in fraction IgM are the same entities as C'-PNAb.