New sights on PPR pathogenesis and development of PPR live attenuated DIVA vaccines using reverse genetics approach

Across Africa, Middle East and Asia, Peste des petits ruminants virus (PPRV), places a huge disease burden on agriculture, in particular affecting small ruminant production. The recent outbreaks in Northern Africa, European part of Turkey and Bulgaria represent a significant threat to mainland of Europe, as a source of disease spread.

The current understanding of PPRV pathogenesis has been mainly derived from the closely related rinderpest virus (RPV). There are few studies that have focused on the late stages of pathogenesis of PPRV in the field and very little is known about the processes underlying the early events of pathogenesis. It is believed that PPRV replicates mainly in the respiratory epithelium before disseminating throughout the host. The application of reverse genetics techniques provides a tool to gain a better understanding of the molecular factors underlying virus host range and pathogenesis. Using reverse genetics approach and tagging the virulent PPRV with GFP, it was possible to demonstrate that the virus primarily replicates in dendritic cells inside the pharyngeal tonsil and later on virus replicates in the epithelial cells of respiratory and gastrointestinal tracts.

Although two safe and efficacious live attenuated vaccines are available for PPR control, current serological tests do not enable to differentiate between naturally infected and vaccinated animals (DIVA). This is posing a serious problem for the sero-surveillance programs during ongoing eradication. Further, during the latter stages of any eradication programme ongoing vaccination is only possible if the vaccine used is fully DIVA compliant. Using reverse genetics technique, the existing live attenuated PPR vaccine viruses have been modified to two DIVA vaccines. As a proof of principle, the developed DIVA vaccines have been evaluated in goats in pilot studies and the animals were fully protected similar to the parent vaccines upon virulent PPR virus challenge. It was also possible to differentiate infected from vaccinated animals by two new ELISAs using two recombinant proteins.

The webinar was given by Professor Satya Parida, Laboratory and Vaccine Specialist at the Food and Agriculture Organisation of the United Nations, and Visiting Professor at the Royal Veterinary College, University of London. Professor Parida's talk was followed by a discussion moderated by IVVN Network Management Board member Professor Brian Perry.