Recombinant Newcastle Disease Viruses Expressing Canine Distemper Virus F And H Glycoprotein

Canine distemper (CD) is an acute and highly contagious disease caused by canine distempervirus(CDV). CDV has a wide rang of hosts and infects most of the carnivorous species includingCanidae, Mustelidae, Procyonidaeb and some Felidae. CD is a multisystemic disease andcharacterized by100%morbidity and80%mortality in infected animals. Over the past decades, CDVhas caused several fatal outbreaks in wild carnivores and vaccination is the most important treatment ofcontrol and prevention this disease. But current modified-live vaccine against CD have many defects,such as poor thermal stability, subjected to interference of maternal antibody, sufficient virulence tocause death in more susceptible species. These have resulted in increasing interest in a safe and efficientCDV vaccine.CDV is a member of the genus Morbillivirusgenus in the Paramyxoviridae family. It is anenveloped RNA virus that contains a single-stranded negative-sense genome. The viral envelopecontains two integral membrane proteins, the fusion (F) and hemagglutinin (H) proteins. They are themajor antigens inducing virus neutralizing antibodies and protective immunity in host. Newcastledisease virus (NDV) LaSota vaccine strain has host range restriction and does not infect mammals. Itssafety and efficacy as a vaccine vector has also been evaluated in many primate experiments.We successfully constructed and rescued two recombinants NDV expressing CDV Rockborn-20/8strain F and H glycoprotein respectively, named rLa-CDV-F and rLa-CDV-H, by reverse geneticstechniques. The expression of CDV F or H protein in recombinant virus was confirmed by Western blotand indirect immunofluorescence assay. rLa-CDV-F and rLa-CDV-H retained the parent strain’shigh-titer growth property and low pathogenicity in embryonated chicken eggs. The CDV-specific IgGantibody level induced by rLa-CDV-H in mice serum is significantly higher than that elicited byrLa-CDV-F, so was the level of CDV virus neutralizing antibodies(VNA) induced in dogs. rLa-CDV-Hand rLa-CDV-F+rLa-CDV-H induced similar level of CDV VNA after priming and boosting, and theVNA titers were boosted significantly after the second dose. Adult dogs with low CDV VNA titers,previous vaccinated with commercially available vaccines, developed an evident enhancement ofanamnestic immune response after immunizing with rLa-CDV-H or rLa-CDV-F+rLa-CDV-H. Theseresults indicated rLa-CDV-H have the potential of being novel CDV vaccines.