RUBELLA REIMMUNIZATION - COMPARATIVE-ANALYSIS OF THE IMMUNOGLOBULIN-GRESPONSE TO RUBELLA-VIRUS VACCINE IN PREVIOUSLY SERONEGATIVE AND SEROPOSITIVE INDIVIDUALS

Rubella virus (RV)-specific immunoglobulin G (IgG) antibodies were stu died in military recruits undergoing unselected immunization with live attenuated measles, mumps, and rubella virus (MMR) vaccine. Three dif ferent whole-RV enzyme immunoassays (EIAs) and an epitope-specific EIA with a synthetic peptide (BCH 178c) representing a neutralization dom ain on the RV E1 envelope protein were used. Before vaccination, 84.2, 87.7, and 84.5% of the subjects tested (n = 399) were found to be ser opositive (>10 IU/ml or assay equivalent) by the three whole-RV EIAs, respectively, while only 82.5% were seropositive by the BCH-178c EIA. Although prevaccination seropositivity rates were similar for the whol e-RV EIAs (sensitivity, 94 to 100%), many sera considered seropositive by the whole-RV EIAs had E1 peptide EIA antibody levels of <10 IU/ml (sensitivity, 77.4 to 80.7%). One month after vaccination, 97.8, 97.2, and 93.5% of the subjects who were followed (n = 356) were seropositi ve by the three whole-RV EIAs, respectively, while 89% had BCH-178c pe ptide-specific IgG titers of >10 IU/ml. After vaccination, depending o n the assay used, up to 20.6% of initially seropositive individuals ex hibited a greater than fourfold increase in RV-specific IgG, while up to 47.3% showed a greater than twofold increase. Increased antibody ti ters after vaccination (seroboosting) were most frequently associated with low levels of BCH-178c peptide-specific IgG before vaccination. R V protein-specific IgG was also studied by immunoblot assays in a subs et (n = 56) of individuals receiving the MMR vaccine, Of these, 89.4 a nd 91.1% exhibited RV protein (E1, E2, and C protein)-specific IgG bef ore and after vaccination, respectively. Seroboosting (two- to fourfol d increase in EIA titers of individuals seropositive by the whole-RV E IA before vaccination) was usually accompanied by a shift in the IgG i mmunoblot pattern from a single (E1) to multiple (E1-E1, E1-C, or E1-E 2-C) specificities, suggesting exposure of new epitopes as a result of viral replication.