Phylogenetic analysis of the hexon and protease genes of a fish adenovirus isolated from white sturgeon (Acipenser transmontanus) supports the proposal for a new adenovirus genus.

The organisation of the central part of the genome of a fish adenovirus (AdV) isolated from white sturgeon (Acipenser transmontanus) was studied. The putative genes identified between those of the viral DNA polymerase and the pVIII protein showed no significant difference in size or localisation compared to other known non-mastadenoviral genomes. The complete nucleotide sequences of the hexon and the viral protease genes and the intergenic region in the white sturgeon adenovirus (WSAdV-1) were compared with members of the four official AdV genera. In the case of WSAdV-1, merely two nucleotides separated the hexon and the protease genes, while in the other AdVs certain genus-specific features were recognised. In distance analyses based on complete sequence of the hexon or the protease proteins, the clear separation of five groups was seen corresponding to the four accepted AdV genera and WSAdV-1. Although there were slight differences between the topologies of the phylogenetic trees, the results unambiguously confirmed the distinctness of WSAdV-1 thus supporting the establishment of a new, fifth AdV genus.