Virus-Host Co-Evolution: How Specialized Should a Strain of a Multi-Host Virus Be?

Dec. 11, 2012 — A new study of canine distemper virus (CDV) provides the first evidence that the virus occurs as specialist strains that emerge in response to strong evolutionary selection in the large global domestic dog population, and as generalist strains adapted to infect a broad range of carnivore species that occur as smaller host populations. The study not only unravelled one key mechanism which led to the evolution of specialist and generalist strains, it also showed that specialising on one host species comes at the cost of a reduced ability to infect other host species.

Scientists from the Leibniz Institute for Zoo and Wildlife Research (IZW), the Freie Universität Berlin and the University of Göttingen in Germany, the INRS-Institut Armand-Frappier in Canada and Cornell University in USA investigated the 'lock and key' mechanism used by the canine distemper virus (CDV) to gain entry into host cells. In the case of CDV, this mechanism involves the binding of a specific protein of the virus (the CDV haemagglutinin protein, CDV-H) to a specific receptor molecule on the host cell (the signalling lymphocytic activation molecule, SLAM). The authors investigated differences between SLAM receptors in wild and domestic carnivore species. This revealed that SLAM receptors from different species in the dog family (Canidae) were quite similar but that they differed substantially from those of species in other carnivore families such as the cats (Felidae), hyenas (Hyaenidae), martens (Mustelidae), seals (Phocidae) and walruses (Odobenidae). "As the configuration of the 'lock' on the host cell varies considerably between dogs and their close relatives on the one hand and carnivores from other families on the other, we expected that the 'key' used by different strains of CDV to gain entry to host cells would also show variation. Viruses constantly adapt to improve their ability to infect their different host species" comments Klaus Osterrieder (FU Berlin).

Continued:  http://www.sciencedaily.com/releases/2012/12/121211193120.htm