Isolation and characterization of an Aves polyomavirus 1 from diseased budgerigars in China

Structural similarity of human papillomavirus E4 and polyomaviral VP4 exhibited by genomic analysis of the common kestrel (Falco tinnunculus) polyomavirus

Polyomaviruses are widely distributed viruses of birds that may induce developmental deformities and internal organ disorders primarily in nestlings. In this study, polyomavirus sequence was detected in kidney and liver samples of a common kestrel (Falco tinnunculus) that succumbed at a rescue station in Hungary. The amplified 5025 nucleotide (nt) long genome contained the early (large and small T antigen, LTA and STA) and late (viral proteins, VP1, VP2, VP3) open reading frames (ORFs) typical for polyomaviruses. One of the additional putative ORFs (named VP4) showed identical localization with the VP4 and ORF-X of gammapolyomaviruses, but putative splicing sites could not be found in its sequence. Interestingly, the predicted 123 amino acid (aa) long protein sequence showed the highest similarity with human papillomavirus E4 early proteins in respect of the aa distribution and motif arrangement implying similar functions. The LTA of the kestrel polyomavirus shared <59.2% nt and aa pairwise identity with the LTA sequence of other polyomaviruses and formed a separated branch in the phylogenetic tree among gammapolyomaviruses. Accordingly, the kestrel polyomavirus may be the first member of a novel species within the Gammapolyomavirus genus, tentatively named Gammapolyomavirus faltin.

Genetic characterization of avian polyomaviruses identified from psittacine birds in South Korea

Budgerigar fledgling disease (BFD) is a contagious disease caused by avian polyomavirus (APV) in psittacine birds and causes high mortality rates. Here, eight APV-positive cases were confirmed from dead parrots or parrot tissue samples by polymerase chain reaction (PCR). Full-length genome sequencing showed high nucleotide identity (98.84-100%) between the APV strains. Phylogenetic analysis revealed that two genogroups were cocirculating in South Korea. The nucleotide sequences of five strains, collected from different parrot species, were identical; however, pathological lesions were observed in only two parrots, both aged 2 months. Pathology included necrotic spots in the liver, subcutaneous haemorrhage, hepatomegaly, ascites, intranuclear inclusion bodies, hepatocyte karyomegaly, hepatic necrosis, and bile duct proliferation. This suggests that the pathogenicity of APV might be host age-dependent regardless of the host species. This study improves our understanding of APV pathogenicity and provides a more detailed genetic characterization of APV strains.RESEARCH HIGHLIGHTS Eight APV strains were identified in South Korea from 2019 to 2021.By phylogenetic analysis, South Korean APV strains were classified into two clades.

Pathogenicity of Avian Polyomaviruses and Prospect of Vaccine Development

Polyomaviruses are nonenveloped icosahedral viruses with a double-stranded circular DNA containing approximately 5000 bp and 5–6 open reading frames. In contrast to mammalian polyomaviruses (MPVs), avian polyomaviruses (APVs) exhibit high lethality and multipathogenicity, causing severe infections in birds without oncogenicity. APVs are classified into 10 major species: Adélie penguin polyomavirus, budgerigar fledgling disease virus, butcherbird polyomavirus, canary polyomavirus, cormorant polyomavirus, crow polyomavirus, Erythrura gouldiae polyomavirus, finch polyomavirus, goose hemorrhagic polyomavirus, and Hungarian finch polyomavirus under the genus Gammapolyomavirus. This paper briefly reviews the genomic structure and pathogenicity of the 10 species of APV and some of their differences in terms of virulence from MPVs. Each gene’s genomic size, number of amino acid residues encoding each gene, and key biologic functions are discussed. The rationale for APV classification from the Polyomavirdae family and phylogenetic analyses among the 10 APVs are also discussed. The clinical symptoms in birds caused by APV infection are summarized. Finally, the strategies for developing an effective vaccine containing essential epitopes for preventing virus infection in birds are discussed. We hope that more effective and safe vaccines with diverse protection will be developed in the future to solve or alleviate the problems of viral infection.

Detection of aves polyomavirus 1 (APyV) and beak and feather disease virus (BFDV) in exotic and native Brazilian Psittaciformes

There are several viral diseases in captive birds. Aves polyomavirus 1 (APyV) and beak and feather disease virus (BFDV) are among the most important in Psittaciformes. The occurrence of these agents has been widely described in various parts of the world; however, little is known about these viruses in South America. APyV and BFDV can cause high morbidity with feather alterations and even mortality. Other variable symptoms could appear depending on the host's age and taxonomic group. The aim of this study was to detect APyV and BFDV in samples of captive exotic and native Psittaciformes in Brazil. Samples from 120 birds with clinical signs compatible with APyV and/or BFDV were examined. In total, 57 (47.5%) positive birds were found, of which 21 (17.5%) had APyV and 41 (34.17%) had BFDV. Five animals (4.17%) presented concurrent infection. Phylogenetic analysis showed a divergent APyV strain and a diversity of Brazilian BFDV strains. Our study shows that these viruses are present at a significant frequency in captive exotic and native Psittaciformes in Brazil. This study also highlights the need for constant epidemiologic surveillance to preserve bird biodiversity with a focus on endangered Psittaciformes species.

Molecular Characterization of a Novel Budgerigar Fledgling Disease Virus Strain From Budgerigars in China

Budgerigar fledgling disease virus (BFDV) is the causative polyomavirus of budgerigar fledgling disease, an important avian immunosuppressive disease in budgerigars (Melopsittacus undulatus). In the current study, we explored the etiological role and molecular characteristics of BFDV. We identified a novel BFDV strain, designated as SC-YB19, belonging to a unique cluster with three other domestic strains (WF-GM01, SD18, and APV-P) and closely related to Polish isolates based on complete sequences. Sequence analysis showed that SC-YB19 had an 18-nucleotide (nt) deletion in the enhancer region, corresponding to the sequence position 164–181 nt, which differed significantly from all other BFDV strains. Based on sequence alignment, three unique nucleotide substitutions were found in VP4 (position 821), VP1 (position 2,383), and T-antigen (position 3,517) of SC-YB19, compared with SD18, WF-GM01, QDJM01, HBYM02, APV7, and BFDV1. Phylogenetic analyses based on complete sequences suggested that SC-YB19, along with the domestic WF-GM01, SD18, and APV-P strains, formed a single branch and were closely related to Polish, Japanese, and American isolates. These results demonstrate that BFDV genotype variations are co-circulating in China, thus providing important insight into BFDV evolution.

Genomic and phylogenetic analysis of avian polyomaviruses isolated from parrots in Taiwan

Avian polyomavirus (APV) is a non-enveloped virus with a circular double-stranded DNA genome approximately 5000 bp in length. APV was first reported in fledgling budgerigars (Melopsittacus undulatus) as the causative agent of budgerigar fledgling disease, resulting in high parrot mortality rates in the 1980s. This disease has been observed worldwide, and APV has a wide host range including budgerigars, cockatoos, lorikeets, lovebirds, and macaws. Twenty APV isolates have been collected from healthy and symptomatic parrots in Taiwan from 2015 to 2019. These isolates were then amplified via polymerase chain reaction, after which the whole genomes of these isolates were sequenced. The overall APV-positive rate was 14.2%, and the full lengths of the APV Taiwan isolates varied from 4971 to 4982 bps. The APV genome contains an early region that encodes two regulatory proteins (the large tumor antigen (Large T-Ag) and the small tumor antigen (Small t-Ag)) and a late region which encodes the capsid proteins VP1, VP2, VP3, and VP4. The nucleotide identities of the VP1 and VP4 genes ranged from 98.7 to 100%, whereas the nucleotide sequence of the Large T-Ag gene had the highest identity (99.2-100%) relative to other APV isolates from the GenBank database. A phylogenetic tree based on the whole genome demonstrated that the APV Taiwan isolates were closely related to Japanese and Portuguese isolates. Recombination events were analyzed using the Recombination Detection Program version 4 and APV Taiwan isolate TW-3 was identified as a minor parent of the APV recombinants. In this study, we first reported the characterization of the whole genome sequences of APV Taiwan isolates and their phylogenetic relationships with all APV isolates available in the GenBank database.

What Animal Cancers teach us about Human Biology

Cancers in animals present a large, underutilized reservoir of biomedical information with critical implication for human oncology and medicine in general. Discussing two distinct areas of tumour biology in non-human hosts, we highlight the importance of these findings for our current understanding of cancer, before proposing a coordinated strategy to harvest biomedical information from non-human resources and translate it into a clinical setting. First, infectious cancers that can be transmitted as allografts between individual hosts, have been identified in four distinct, unrelated groups, dogs, Tasmanian devils, Syrian hamsters and, surprisingly, marine bivalves. These malignancies might hold the key to improving our understanding of the interaction between tumour cell and immune system and, thus, allow us to devise novel treatment strategies that enhance anti-cancer immunosurveillance, as well as suggesting more effective organ and stem cell transplantation strategies. The existence of these malignancies also highlights the need for increased scrutiny when considering the existence of infectious cancers in humans. Second, it has long been understood that no linear relationship exists between the number of cells within an organism and the cancer incidence rate. To resolve what is known as Peto's Paradox, additional anticancer strategies within different species have to be postulated. These naturally occurring idiosyncrasies to avoid carcinogenesis represent novel potential therapeutic strategies.