Progress in the development of a heat-stable recombinant rinderpest vaccine using an attenuated vaccinia virus vector.

Rinderpest is a fatal infectious disease of cattle and buffalo, and is prevalent in many parts of the developing world. Eradication campaigns are at present under way in Africa, the Middle East and South Asia. As these regions have very hot climates, it is difficult and expensive to establish reliable cold chains to deliver heat-sensitive vaccines and, for this reason, many previous vaccination/eradication campaigns have been ineffective. To overcome the problem of vaccine heat-lability, a recombinant rinderpest vaccine (RRV) has been developed by inserting the haemagglutinin gene of rinderpest virus into the attenuated smallpox vaccine (vaccinia virus) and using this as heat-stable vaccine vector system to deliver the foreign antigens. This rinderpest vaccine, as with the smallpox vaccine, could be used for the global eradication campaign, without the need to establish a cold chain. Both the efficacy and the safety of the RRV have been confirmed in experiments in cattle. In addition to heat stability, the RRV has several other advantages over the current rinderpest tissue-culture vaccine. DNA viruses have greater genetic stability than RNA viruses (this may be easily checked by restriction enzyme analysis), and the use of RRV enables vaccinated animals to be distinguished from naturally-infected animals, as the vaccine generates a more restricted antigenic response to rinderpest virus. The current situation in relation to the efficacy and safety of the RRV is discussed.