A novel approach to generating morbillivirus vaccines: Negatively marking the rinderpest vaccine

The eradication of rinderpest virus (RPV) from the globe was possible through the availability of a safe and effective live attenuated vaccine and a suitable companion diagnostic test. However, the inability to serologically ‘Differentiate between naturally Infected and Vaccinated Animals’ (DIVA) meant that both the time taken to complete the eradication programme and the economic burden on countries involved was significantly greater than if a vaccine and companion diagnostic test that fulfilled the DIVA concept had been available. During the RPV eradication campaign serosurveillance for RPV was primarily based on a competitive ELISA using a RPV specific (C1) monoclonal antibody (mAb) directed against the viral haemagglutinin (H) protein but this test was not able to meet DIVA requirements. To provide proof of concept for the generation of novel morbillivirus DIVA vaccines we have identified, by phage display, and mutated residues critical for C1 mAb binding and assessed the functionality of mutants in an in vitro fusion assay. Finally we have incorporated mutated epitopes into a full length clone and rescued recombinant RPV using reverse genetics techniques. Here we describe a novel mechanism of marking morbillivirus vaccines, using RPV as a proof of concept, and discuss the applicability of this method to the development of marked vaccines for peste des petits ruminants virus (PPRV).

► The RPV diagnostic ELISA relies on a monoclonal antibody (C1) targeting the haemagglutinin protein.
► RPV haemagglutinin protein can be mutated so it is no longer detected by the C1 monoclonal antibody.
► Two mutations, H309S G311S, are sufficient to prevent C1 binding to H by immunofluorescence.
► These two mutations are maintained in a recombinant live virus over numerous passages.
► This proof of concept work suggests its suitability for application for novel PPRV vaccines.