Prenatal and postnatal production of IgM and IgA antibodies to rubella virus studied by antibody capture immunoassay.

Rubella virus-specific IgM and IgA antibodies were quantitated by antibody capture immunoassay in adults after primary infection and after experimentally induced reinfection. Antibodies to rubella virus were also detected in fetuses whose mothers had rubella before week 18 of pregnancy. IgM and IgA concentrations in fetal blood were determined by radial immunodiffusion and enzyme immunoassay, respectively. In primary postnatal infection, IgM antibodies were consistently found until week 8 after onset of the disease, and after week 14 these antibodies were usually no longer detected. The time of disappearance of rubella virus-specific IgA varied with each individual. After vaccination of previously immune volunteers, no change was noted in level of IgA antibody, and no IgM antibody was detected. In infected fetuses, total IgM and IgA concentrations rose significantly, and rubella virus-specific IgM and IgA antibodies were detected as early as week 22 of pregnancy.