Genetic relatedness of the caliciviruses: San Miguel sea lion and vesicular exanthema of swine viruses constitute a single genotype within the Caliciviridae.

The San Miguel sea lion viruses (SMSV) and vesicular exanthema of swine viruses (VESV) are related morphologically and antigenically, but little has been done to determine their genotypic relationship to each other and to other caliciviruses. To examine this relationship, reverse transcriptase PCRs were performed by using oligonucleotide primer sets designed to amplify portions of the 2C RNA helicase-like and RNA-dependent RNA polymerase regions with total cellular RNA purified from virus-infected cell cultures as a template. The 2C RNA helicase primers directed the amplification of this region from eight SMSV serotypes, five VESV serotypes, and four related viruses. The RNA polymerase primer sets amplified products from all these viruses except one. Phylogenetic comparison of the caliciviruses demonstrated that SMSV, VESV, and four related viruses are closely related while being distinct from feline calicivirus, the human caliciviruses (small, round-structured viruses), and rabbit hemorrhagic disease virus and that they should be classified as a single genotype within the Caliciviridae.