Butcherbird polyomavirus isolated from a grey butcherbird (Cracticus torquatus) in Queensland, Australia

Abstract

A novel avian polyomavirus was detected in peri-ocular skin lesions collected from a grey butcherbird (Cracticus torquatus), using a combination of multiply primed rolling circle amplification, nested PCR and long range PCR. The sequence of Butcherbird polyomavirus was determined by combining next generation sequencing and primer walking techniques. The circular double-stranded DNA genome of Butcherbird polyomavirus consisted of 5084 bp, and encoded six open reading frames (ORF-X, VP2, VP3, VP1, small T-antigen and large T-antigen). Phylogenetic analysis placed it amongst other members of the genus Avipolyomavirus, most closely related to Crow polyomavirus. Next generation sequencing enabled the detection of DNA fragments similar to, but distinct from, Canarypox virus within the same lesion from which Butcherbird polyomavirus was amplified, thus confirming an avipolyomavirus-avipoxvirus co-infection in the peri-ocular skin lesions of this grey butcherbird.

Introduction

Members of the family Polyomaviridae are non-enveloped, icosahedral viruses measuring 40–45 nm in diameter (Imperiale and Major, 2007). Their capsids contain a single circular molecule of double stranded DNA of approximately 5000 bp, in which they encode structural proteins (VP1, VP2, VP3, and sometimes others) on one strand and transforming proteins (large, small and occasionally other T-antigens) on the opposite strand (Imperiale and Major, 2007, Johne et al., 2011). Between the start codons of these two genome regions lies a non-coding control region (NCCR), which contains the origin of DNA replication and regulatory sequences (Imperiale and Major, 2007, Johne et al., 2011).

Over the last few years, there has been a significant increase in the number of known polyomavirus (PyV) isolates from a wide range of vertebrate hosts including birds (Johne et al., 2006, Johne and Müller, 2007, Halami et al., 2010), bats (Misra et al., 2009, Fagrouch et al., 2012, Tao et al., 2013), humans (Allander et al., 2007, Gaynor et al., 2007, Feng et al., 2008, van der Meijden et al., 2010, Scuda et al., 2011, Buck et al., 2012, Lim et al., 2012, Siebrasse et al., 2012, Yu et al., 2012, Korup et al., 2013), non-human primates (Johne et al., 2005, Verschoor et al., 2008, Deuzing et al., 2010, Groenewoud et al., 2010, Leendertz et al., 2011), carnivores (Wellehan et al., 2011, Duncan et al., 2013), horses (Renshaw et al., 2012), rodents (Orba et al., 2011), and a dolphin (Anthony et al., 2013). Three genera have now been erected within the family: Orthopolyomavirus and Wukipolyomavirus for the known PyVs of mammals, and Avipolyomavirus for the known PyVs of birds (Johne et al., 2011).

Butcherbirds are mid-sized, black-grey and white, passerine birds classified within the genus Cracticus (Gillies, 1984). The genus includes seven species, all of which are native to Australasia (Kearns et al., 2013). The grey butcherbird, Cracticus torquatus, is an inhabitant of every State and Territory of Australia (Kearns et al., 2013). It is regarded as common, and listed by the IUCN as a species of least concern (http://www.iucnredlist.org).

This manuscript reports the complete genetic characterisation of Butcherbird polyomavirus, a novel member of the genus Avipolyomavirus, in the context of co-infection with an unknown Avipoxvirus species.