Effect of the 5'-untranslated region of pestivirus genome on the host range

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The genus Pestivirus of the family Flaviviridae is represented by four established species ; Bovine viral diarrhea virus 1 (BVDV-1), Bovine viral diarrhea virus 2 (BVDV-2), Border disease virus (BDV) and Classical swine fever virus (CSFV) and a tentative "Giraffe" species. Although these viral species are identified mostly according to the animal host species from which they are isolated, there is an extensive antigenic cross reactivity among them, and they can cross the host species barrier and infect different animal species within the cloven-footed animals. Serological data indicate that the host range of pestiviruses includes most even-toed ungulates. Pestiviruses have been isolated not only from domestic animals but also from wildlife, such as deer or giraffe. Taxonomic study on these isolates from wildlife will provide useful information on the ecology and evolution of pestiviruses. The 5'-untranslated region (UTR) of pestivirus genome is highly conserved among all members within … More the genus Pestivirus, thus being useful for the characterization of species or genotypes. Although the nucleotide sequence of the 5'-UTR is well conserved among the members of the Pestivirus genus, the 5'-UTR has been known to contain at least three variable loci. The nucleotide substitutions at these variable loci are particularly important because the 5'-UTR of positive-sense RNA viruses generally includes regulatory motifs, which are indispensable to viral survival. Therefore, random mutations at the 5'-UTR have a high probability of incompatibility with viral survival. Thus stable nucleotide variations at this level assume high importance in terms of virus evolutionary history. Nucleotide sequences at the three variable loci in the 5'-UTR of pestiviruses have been shown to be palindromic and capable of forming a stable stem-loop structure peculiar to each Pestivirus species. Nucleotide substitutions in the stem regions always occur to maintain the palindromic sequence and thereby form a stable stem-loop structure. Thus, this type of mutation was referred to palindromic nucleotide substitutions (PNS). On the basis of the PNS at the 5'-UTR, five species (BVDV-1, BVDV-2, CSFV, BDV and "Giraffe") were distingushed in the genus Pestivirus. Less