Neutralizing Monoclonal Antibody to the E1 Glycoprotein Epitope of Rubella Virus Mediates Virus Arrest in VERO Cells

The best-known mechanism of action of antibody-mediated virus neutralization is to impede the entrance of viruses to host cells, as determined by neutralization assays. Antibodies may also inhibit the exit of rubella virus (RV) from infected host cells; in this case, the interaction of the antibodies with their domains must occur on the plasma membrane, because antibodies cannot enter the cells. In the present study, we were able to block temporally the exit of virions from RV-infected cells by the binding of monoclonal antibody (mAb) H3 to their surface. The objective was accomplished in three steps: first, we determined the duration of the viral replication cycle; then we established the kinetics of the presence of the domains defined by our mAbs in the cytoplasm of RV-infected VERO cells; and, finally, we assessed the release of viral particles to the supernatant of infected VERO cells in the presence or absence of mAbs or positive and negative mice sera. RV-specific mice sera and mAb H3, which binds to the amino acid sequence 208–239 of the RV-E1 glycoprotein, were able to delay for 24 hours the release of virions from infected cultures, suggesting that the reaction of mAb H3 with its epitope may arrest any change necessary for the assembly and/or release of virions. In conclusion, the neutralizing domain recognized by mAb induces antibodies that can block the viral replication by several mechanisms of action, such as the obstruction of virus entry into cells and the delay of viral release. All of these mechanisms are intimately involved in the critical virus–host cell interactions that allow self-limitation of the infection.