The Genome of Canarypox Virus

Abstract

Here we present the genomic sequence, with analysis, of a canarypox virus (CNPV). The 365-kbp CNPV genome contains 328 potential genes in a central region and in 6.5-kbp inverted terminal repeats. Comparison with the previously characterized fowlpox virus (FWPV) genome revealed avipoxvirus-specific genomic features, including large genomic rearrangements relative to other chordopoxviruses and novel cellular homologues and gene families. CNPV also contains many genomic differences with FWPV, including over 75 kbp of additional sequence, 39 genes lacking FWPV homologues, and an average of 47% amino acid divergence between homologues. Differences occur primarily in terminal and, notably, localized internal genomic regions and suggest significant genomic diversity among avipoxviruses. Divergent regions contain gene families, which overall comprise over 49% of the CNPV genome and include genes encoding 51 proteins containing ankyrin repeats, 26 N1R/p28-like proteins, and potential immunomodulatory proteins, including those similar to transforming growth factor ␤ and ␤-nerve growth factor. CNPV genes lacking homologues in FWPV encode proteins similar to ubiquitin, interleukin-10-like proteins, tumor necrosis factor receptor, PIR1 RNA phosphatase, thioredoxin binding protein, MyD116 domain proteins, circovirus Rep proteins, and the nucleotide metabolism proteins thymidylate kinase and ribonucleotide reductase small subunit. These data reveal genomic differences likely affecting differences in avipoxvirus virulence and host range, and they will likely be useful for the design of improved vaccine vectors.Within the Chordopoxvirinae subfamily (poxviruses of vertebrates) of the Poxviridae, Avipoxvirus is the only characterized genus to infect nonmammalian hosts (57, 60), including more than 60 species of wild birds representing 20 families (60, 97). Variable restriction enzyme profiles suggest significant genomic differences among avipoxviruses (32,97,98). Crossinfection studies also suggest genetic differences among avipoxviruses, as specific virus-host combinations may not be cross-protective and result in a wide range of pathogenic effects, from absence of clinical disease to generalized infection and death (8,97).Canarypox virus (CNPV) is an avipoxvirus and etiologic agent of canarypox, a disease of birds both in the wild and in commercial aviaries, where significant losses result (15,16,33,45). Canarypox has been described broadly as the poxviral disease of passeriform (song) birds, efficiently causing disease in passerine hosts compared to galliform (domestic fowl) and columbiform (pigeon) hosts (8,15,22,33). However, passerine host preferences exist, and current International Committee on Taxonomy of Viruses classification differentiates between CNPV and several other passerine isolates (60, 97). CNPV produces clinical signs similar to generalized poxviral infections of other birds, including both cutaneous and diptheretic disease forms caused by the prototypical galliform avipoxvirus, fowlpox virus (FWPV), and incl...

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