Neutralizing monoclonal antibody to the E1 glycoprotein epitope of rubellavirus mediates virus arrest in VERO cells

The best-known mechanism of action of antibody-mediated virus neutralizatio n is to impede the entrance of viruses to host cells, as determined by neut ralization assays. Antibodies may also inhibit the exit of rubella virus (R V) from infected host cells; in this case, the interaction of the antibodie s with their domains must occur on the plasma membrane, because antibodies cannot enter the cells. In the present study, we were able to block tempora lly the exit of virions from RV-infected cells by the binding of monoclonal antibody (mAb) H3 to their surface. The objective was accomplished in thre e 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 asses sed the release of viral particles to the supernatant of infected VERO cell s 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 w ith its epitope may arrest any change necessary for the assembly and/or rel ease of virions. In conclusion, the neutralizing domain recognized by mAb i nduces antibodies that can block the viral replication by several mechanism s of action, such as the obstruction of virus entry into cells and the dela y of viral release. All of these mechanisms are intimately involved in the critical virus-host cell interactions that allow self-limitation of the inf ection.