Selective reactivity of antibodies to human immunoglobulins G, M, and A with rubella virus proteins

Abstract

Proteins of purified rubella virus were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, transferred to nitrocellulose and immunoblotted with human sera and Ig class H-chain-specific peroxidase conjugates. The levels of rubella antibodies in these sera were predetermined by the radial hemolysis test, the density gradient centrifugation method for IgM antibodies and IgG-, IgM- and IgA-specific enzyme immunoassays. In immunoblotting, rubella-specific IgG antibodies reacted with both envelope glycoproteins (E1 and E2) and the capsid protein (C). Rubella IgM antibodies reacted predominantly with E1, whereas the specific reactivity of IgA antibodies was directed mainly to the capsid protein. Purified IgM rheumatoid factor added to IgG-positive, IgM-negative serum did not give false-positive reactivity in the immunoblotting test as it did in solid-phase enzyme immunoassays. The Ig class-specific reactivities with the different viral proteins are expected to have diagnostic applications.