Résumé
Adenoviruses are common pathogens in vertebrates, infecting a wide range of hosts, but only having rarely been detected and correlated with disease in cetaceans. This article describes the first complete genomic sequence of a cetacean adenovirus, bottlenose dolphin adenovirus 1 (BdAdV-1), detected in captive bottlenose dolphin population (Tursiops truncatus) suffering from self-limiting gastroenteritis. The complete genome sequence of BdAdV-1 was recovered from data generated by high-throughput sequencing and validated by Sanger sequencing. The genome is 34,080bp long and has 220 nucleotides long inverted terminal repeats. A total of 29 coding sequences were identified, 26 of which were functionally annotated. Among the unusual features of this genome is a remarkably long 4380bp E3 ORF1, that displays no sequence homology with the corresponding E3 regions of other adenoviruses. In addition, the fiber protein only has 26% identity with fiber proteins described in other adenoviruses. Three hypothetical proteins were predicted. The phylogenetic analysis indicates that the closest known relative to BdAdV-1 is an adenovirus detected in bottlenose dolphin (KR024710), with an amino acid sequence identity between 36 and 79% depending on the protein. Based on the phylogenic analysis, the BdAdV-1 appears to have co-evolved with its host.
The results indicate that BdAdV-1 belongs to the Mastadenovirus genus of the Adenoviridae family, however, it is clearly different from other adenoviruses, especially in the 3′-end of the viral genome. The high degree of sequence divergence suggests that BdAdV-1 should be considered as a novel species in the Mastadenovirus genus. The study also demonstrates the usefulness of high-throughput sequencing to obtain full-length genomes of genetically divergent viruses.
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•This is the first complete genomic sequence of a cetacean adenovirus, discovered in bottlenose dolphin with gastroenteritis.•Phylogenetic analysis shows that it is a Mastadenovirus, however, clearly different from other adenoviruses.•The phylogenetic analysis indicates co-evolution of this adenovirus with its host.•The large ORF predicted in the E3 region is highly divergent.•High-throughput sequencing can successfully be applied to obtain full-length genomes of genetically divergent viruses.