Rabies and canine distemper are among the most dangerous and lethal viral diseases afflicting carnivores. Rabies can also be transmitted to humans via bite from rabies-infected animals. It attacks the nervous system and can be deadly if not treated immediately.
Cells infected with canine distemper virus fuse to neighboring uninfected cells to form syncytia. Antibodies against canine distemper virus are used to stain the infected cells with a red dye
Rabies vaccines contain inactivated virus particles and have an excellent stability and safety profile. For vaccination against canine distemper virus, which causes a measles-like disease in its hosts, live-attenuated viruses are used. These vaccine viruses replicate in the vaccinated animals to a certain extent and can lead to severe disease in highly susceptible species.
Prof. Dr. Veronika von Messling’s group at the Veterinary Medicine Division, Paul-Ehrlich-Institut, in collaboration with Dr. Matthias Schnell’s group at Thomas Jefferson University genetically engineered the rabies virus vaccine strain to carry one of the canine distemper virus glycoproteins in addition to its own glycoprotein. The protective immune response is directed against these proteins. Candidate vaccines were then produced following the purification and inactivation protocols used for rabies vaccines.
The researchers first demonstrated that a single shot was sufficient to elicit protective rabies antibody titers in ferrets. However, protection against canine distemper was only achieved when animals were immunized with a mix of viruses carrying both canine distemper virus glycoproteins. The researchers conclude that immune responses against both glycoproteins are necessary to protect from canine distemper.
“Our rabies-based vector is a promising platform for the development of new morbillivirus vaccines” explains von Messling. “It eliminates the risk for vaccine-induced disease and at the same time greatly increases the temperature stability compared to live-attenuated morbillivirus vaccines.”