Complement requirement of neutralizing antibodies in different classes of immunoglobulin appearing in rabbits and guinea pigs after primary and booster immunizations with herpes simplex virus.

Rabbits and guinea pigs were immunized with herpes simplex virus and bled periodically. The sera were fractionated into slow IgG, fast IgG and IgM by DEAE-cellulose column chromatography, and complement-requiring (CRN) and nonrequiring neutralizing (N) antibody activities were estimated. In early sera of rabbits, the two IgG and IgM fractions possessed about equal CRN activities, although some animals showed a slightly lower activity in fast IgG. In guinea pigs, the early CRN activity resided mainly in slow IgS (7 S gamma2). The early IgG antibody of guinea pigs differed from that of rabbits in that it resembled IgM in resistances to heating at 70 C and to 2-merceptoethanol. The level of CRN IgM antibody in rabbits declined following a peak reached in 2 to 3 weeks, whereas such a decline was never observed in guinea pigs. N IgG antibody was developed a few weeks after the first immunization in rabbits and much retarded in guinea pigs. In both species, booster immunization quickly evoked N antibody in the two IgG fractions and also CRN IgM antibody, but in the case of rabbits the IgM antibody disappeared soon. It is concluded that IgG plays an important role in humoral immunity from the initial stage of the immunization course.