Detailed immunologic analysis of the structural polypeptides of rubella virus using monoclonal antibodies

A panel of murine monoclonal antibodies prepared against rubella virus is described. Fourteen of these monoclonal antibodies react with the E1 glycoprotein of rubella virus and define a total of six spacially separate epitopes in competitive inhibition assays. Antibodies binding to epitopes E1(a), E1(b), E1(c), or E1(e) inhibit the hemagglutinin function of the virus, while antibodies binding to epitopes E1(d) or E1(f) do not. Monoclonal antibodies binding to epitopes E1(c) or E1(d) prevent virus infectivity and identify antigen in distinct intracytoplasmic vacuoles of rubella virus-infected Vero cells by indirect immunofluorescence. Monoclonal antibody to epitope E1(f) localizes antigen primarily to the plasma membrane of infected cells, while antibodies binding to epitopes E1(a), E1(b), or E1(e) localize antigen throughout the infected cell's cytoplasm. A single monoclonal antibody is described which only reacts with the mature form of the virion E2 glycoprotein after rubella virus is treated with a disulfide-bond reducing agent. This antibody immunoprecipitates a 43,000 MW precursor to the E2 glycoprotein from lysates of infected cells and localizes its antigen throughout the cytoplasm of infected cells. The five remaining monoclonal antibodies react with the rubella virus C polypeptide. They define four topographically separate epitopes on the C polypeptide, C(a), C(b), C(c), and C(d), each of which is diffusely distributed throughout the cytoplasm of rubella virus-infected cells.