A novel polyomavirus (goose hemorrhagic polyomavirus) is the agent of hemorrhagic nephritis enteritis of geese

A review of DNA viral infections in psittacine birds

To date, several DNA viral infections have been reported in psittacine birds. Psittacine beak and feather disease (PBFD) is characterized by symmetric feather dystrophy and loss and development of beak deformities. PBFD is caused by beak and feather virus, which belongs to the Circoviridae, and is the most important infection in psittacine birds worldwide. Avian polyomavirus infection causes acute death, abdominal distention, and feather abnormalities. Pacheco's disease (PD), which is caused by psittacid herpesvirus type 1, is an acute lethal disease without a prodrome. Psittacine adenovirus infections are described as having a clinical progression similar to PD. The clinical changes in psittacine poxvirus-infected birds include serious ocular discharge, rhinitis, and conjunctivitis, followed by the appearance of ulcerations on the medial canthi of the eyes. Internal papillomatosis of parrots (IPP) is a tumor disease characterized by progressive development of papillomas in the oral and cloacal mucosa. IPP has been suggested to caused by papillomavirus or herpesvirus. However, information about these diseases is limited. Here we review the etiology, clinical features, pathology, epidemiology, and diagnosis of these DNA viruses.

Recombinant subunit vaccine elicits protection against goose haemorrhagic nephritis and enteritis

Outbreaks of haemorrhagic nephritis and enteritis of geese (HNEG) have been reported in goose flocks in Hungary, Germany and France since 1969. HNEG is characterized by high morbidity and mortality rates in geese 3 to 10 weeks of age. The causative agent of HNEG is the goose haemorrhagic polyomavirus (GHPV), which has a circular double-stranded DNA genome encoding the structural proteins VP1, VP2 and VP3. In vitro culture of GHPV has been problematic, so the baculovirus system was used to construct a recombinant virus expressing the VP1 gene of GHPV under control of the polyhedrin promoter in Sf9 insect cells. The expression and the identity of recombinant goose polyomavirus VP1 in the crude Sf9 cell extracts were confirmed by mass spectrometry. Experimental oil-emulsion vaccines containing two different doses of antigen were prepared using this crude extract. Goslings were vaccinated either once at 1 day old or twice by boosting 18 days after the primary vaccination, and were challenged with a virulent polyomavirus isolate at 5 weeks of age. A single injection of either vaccine dose induced 95% protection against challenge. Using the booster vaccination regimen, 100% protection was achieved with either vaccine dose.

Novel human polyomaviruses--re-emergence of a well known virus family as possible human carcinogens

Polyomaviruses belong to a family of DNA tumor viruses that frequently cause cancer upon inoculation into heterologous hosts. The rhesus monkey virus SV40 and mouse polyomavirus have been studied in particular detail. Two members of the polyomavirus family, BK and JC viruses, were identified as human pathogens more than 30 years ago. Both are oncogenic when inoculated into newborn rodents. Their possible role in human cancers has been intensively investigated; conclusive results are, however, still missing. During the past year 3 new members of the polyomavirus family have been identified in humans, KI, WU, and MC-Polyomavirus. Whereas the first 2 were only found in respiratory fluids of children with respiratory infections and in healthy individuals, the third virus was found to be specifically linked to Merkel tumors, a rare human cancer of neuroendocrine origin. The positive Merkel cells contain viral DNA in an integrated and clonal form, suggesting an involvement of this virus in the etiology of those tumors. This article will summarize the results of recent polyomavirus isolations from humans and animals and also address the potential role of members of this virus family in other human malignancies. It also makes reference to observations of polyomavirus-like particles in other conditions, particularly in hair-follicle cell-related proliferations.

A very late viral protein triggers the lytic release of SV40

How nonenveloped viruses such as simian virus 40 (SV40) trigger the lytic release of their progeny is poorly understood. Here, we demonstrate that SV40 expresses a novel later protein termed VP4 that triggers the timely lytic release of its progeny. Like VP3, VP4 synthesis initiates from a downstream AUG start codon within the VP2 transcript and localizes to the nucleus. However, VP4 expression occurs approximately 24 h later at a time that coincides with cell lysis, and it is not incorporated into mature virions. Mutation of the VP4 initiation codon from the SV40 genome delayed lysis by 2 d and reduced infectious particle release. Furthermore, the co-expression of VP4 and VP3, but not their individual expression, recapitulated cell lysis in bacteria. Thus, SV40 regulates its life cycle by the later temporal expression of VP4, which results in cell lysis and enables the 50-nm virus to exit the cell. This study also demonstrates how viruses can generate multiple proteins with diverse functions and localizations from a single reading frame.

A novel virus detected in papillomas and carcinomas of the endangered western barred bandicoot (Perameles bougainville) exhibits genomic features of both the Papillomaviridae and Polyomaviridae

Conservation efforts to prevent the extinction of the endangered western barred bandicoot (Perameles bougainville) are currently hindered by a progressively debilitating cutaneous and mucocutaneous papillomatosis and carcinomatosis syndrome observed in captive and wild populations. In this study, we detected a novel virus, designated the bandicoot papillomatosis carcinomatosis virus type 1 (BPCV1), in lesional tissue from affected western barred bandicoots using multiply primed rolling-circle amplification and PCR with the cutaneotropic papillomavirus primer pairs FAP59/FAP64 and AR-L1F8/AR-L1R9. Sequencing of the BPCV1 genome revealed a novel prototype virus exhibiting genomic properties of both the Papillomaviridae and the Polyomaviridae. Papillomaviral properties included a large genome size ( approximately 7.3 kb) and the presence of open reading frames (ORFs) encoding canonical L1 and L2 structural proteins. The genomic organization in which structural and nonstructural proteins were encoded on different strands of the double-stranded genome and the presence of ORFs encoding the nonstructural proteins large T and small t antigens were, on the other hand, typical polyomaviral features. BPCV1 may represent the first member of a novel virus family, descended from a common ancestor of the papillomaviruses and polyomaviruses recognized today. Alternatively, it may represent the product of ancient recombination between members of these two virus families. The discovery of this virus could have implications for the current taxonomic classification of Papillomaviridae and Polyomaviridae and can provide further insight into the evolution of these ancient virus families.

Endothelial cells as active participants in veterinary infections and inflammatory disorders

Endothelial cells were once viewed as relatively inert cells lining the vasculature. They are now recognized as active and responsive regulators of coagulation, platelet adhesion, fluid homeostasis, wound healing, leukocyte extravasation and vascular tone. Endothelial cells play a key role in the host response to infectious agents by regulating leukocyte trafficking, producing inflammatory cytokines and presenting antigen in association with major histocompatibility class II (MHC II) molecules. A number of infectious agents have a tropism for endothelial cells. Infection of endothelial cells can promote thrombosis, vascular leakage, and increased adherence and emigration of leukocytes. Furthermore, activation of a systemic inflammatory response, in the absence of direct endothelial cell infection, can also lead to endothelial cell dysfunction. The purpose of this review is to highlight the interactions between endothelial cells and infectious or inflammatory agents that contribute to coagulation disturbances, vasculitis and edema. A select group of viral and bacterial pathogens will be used as examples to demonstrate how endothelial cell dysfunction contributes to the pathogenesis of infectious and inflammatory disorders.

Avian polyomavirus mutants with deletions in the VP4-encoding region show deficiencies in capsid assembly and virus release, and have reduced infectivity in chicken

Avian polyomavirus (APV) is the causative agent of an acute fatal disease in psittacine and some non-psittacine birds. In contrast to mammalian polyomaviruses, the APV genome encodes the additional capsid protein VP4 and its variant VP4Delta, truncated by an internal deletion. Both proteins induce apoptosis. Mutation of their common initiation codon prevents virus replication. Here, the generation of replication competent deletion mutants expressing either VP4 or VP4Delta is reported. In contrast to infection with wild-type virus, chicken embryo cells showed no cytopathic changes after infection with the mutants, and induction of apoptosis as well as virus release from the infected cells were delayed. Electron microscopy revealed the presence of a high proportion of small particles and tubules in preparations of the VP4 deletion mutant, indicating a scaffolding function for VP4. Wild-type and mutant viruses elicited neutralizing antibodies against APV after intramuscular and intraperitoneal infection of chicken; however, VP4-specific antibodies were only detected after infection with wild-type virus. Using the oculonasal route of infection, seroconversion was only observed in chickens infected with the wild-type virus, indicating a strongly reduced infectivity of the mutants. Based on the biological properties of the deletion mutants, they could be considered as candidates for APV marker vaccines.

Pathology of goose haemorrhagic polyomavirus infection in goose embryos

Goose embryos were infected with goose haemorrhagic polyomavirus (GHPV) onto the chorioallantoic membrane (CAM) in order to examine the effect of GHPV on the embryos and to obtain data on whether embryos could develop into infected, virus-shedding goslings, as well as to present an accurate biological method for virus titration. The reported method of infection could offer a possibility to express the virus titre as the median embryo infective dose (EID(50)). As a special pathological feature of the disease, extensive cerebral haemorrhages were observed, which protruded the skullcap in many cases. Some embryos infected with 10(1.25) or 10(0.25) EID(50)/0.2 ml were able to hatch; however, they were in poor physical condition and died by post-hatching day 4 showing haemorrhagic nephritis and enteritis of geese. Virus shedding was revealed by polymerase chain reaction. The ability of some of the infected goose embryos to hatch may indicate the potency of GHPV to spread vertically, although this needs further study for confirmation.

Generation of virus-like particles consisting of the major capsid protein VP1 of goose hemorrhagic polyomavirus and their application in serological tests

Goose hemorrhagic polyomavirus (GHPV) is the causative agent of hemorrhagic nephritis and enteritis of geese (HNEG), a fatal disease of young geese with high mortality rates. GHPV cannot be efficiently propagated in tissue culture. To provide antigens for diagnostic tests and vaccines, its major structural protein VP1 was recombinantly expressed in Sf9 insect cells and in the yeast Saccharomyces cerevisiae. As demonstrated by density gradient centrifugation and electron microscopy, GHPV-VP1 expressed in insect cells formed virus-like particles (VLPs) with a diameter of 45 nm indistinguishable from infectious polyomavirus particles. However, efficiency of VLP formation was low as compared to the monkey polyomavirus SV-40-VP1. In yeast cells, GHPV-VP1 alone formed smaller VLPs, 20 nm in diameter. Remarkably, co-expression of GHPV-VP2 resulted in VLPs with a diameter of 45 nm. All three types of GHPV-VLPs were shown to hemagglutinate chicken erythrocytes. ELISA and hemagglutination inhibition tests using the VLPs as antigen detected GHPV-specific antibodies in up to 85.7% of sera derived from flocks with HNEG but in none of the sera of a clinically healthy flock. However, GHPV-specific antibodies were also detected in sera from two other flocks without HNEG indicating a broad distribution of GHPV due to subclinical or unrecognised infections.

Comparing phylogenetic codivergence between polyomaviruses and their hosts

Seventy-two full genomes corresponding to nine mammalian (67 strains) and two avian (5 strains) polyomavirus species were analyzed using maximum likelihood and Bayesian methods of phylogenetic inference. Our fully resolved and well-supported (bootstrap proportions > 90%; posterior probabilities = 1.0) trees separate the bird polyomaviruses (avian polyomavirus and goose hemorrhagic polyomavirus) from the mammalian polyomaviruses, which supports the idea of spitting the genus into two subgenera. Such a split is also consistent with the different viral life strategies of each group. Simian (simian virus 40, simian agent 12 [Sa12], and lymphotropic polyomavirus) and rodent (hamster polyomavirus, mouse polyomavirus, and murine pneumotropic polyomavirus [MPtV]) polyomaviruses did not form monophyletic groups. Using our best hypothesis of polyomavirus evolutionary relationships and established host phylogenies, we performed a cophylogenetic reconciliation analysis of codivergence. Our analyses generated six optimal cophylogenetic scenarios of coevolution, including 12 codivergence events (P < 0.01), suggesting that Polyomaviridae coevolved with their avian and mammal hosts. As individual lineages, our analyses showed evidence of host switching in four terminal branches leading to MPtV, bovine polyomavirus, Sa12, and BK virus, suggesting a combination of vertical and horizontal transfer in the evolutionary history of the polyomaviruses.

Characterization of two novel polyomaviruses of birds by using multiply primed rolling-circle amplification of their genomes

Polyomaviruses are small nonenveloped particles with a circular double-stranded genome, approximately 5 kbp in size. The mammalian polyomaviruses mainly cause persistent subclinical infections in their natural nonimmunocompromised hosts. In contrast, the polyomaviruses of birds--avian polyomavirus (APV) and goose hemorrhagic polyomavirus (GHPV)--are the primary agents of acute and chronic disease with high mortality rates in young birds. Screening of field samples of diseased birds by consensus PCR revealed the presence of two novel polyomaviruses in the liver of an Eurasian bullfinch (Pyrrhula pyrrhula griseiventris) and in the spleen of a Eurasian jackdaw (Corvus monedula), tentatively designated as finch polyomavirus (FPyV) and crow polyomavirus (CPyV), respectively. The genomes of the viruses were amplified by using multiply primed rolling-circle amplification and cloned. Analysis of the FPyV and CPyV genome sequences revealed a close relationship to APV and GHPV, indicating the existence of a distinct avian group among the polyomaviruses. The main characteristics of this group are (i) involvement in fatal disease, (ii) the existence of an additional open reading frame in the 5' region of the late mRNAs, and (iii) a different manner of DNA binding of the large tumor antigen compared to that of the mammalian polyomaviruses.

Types of renal disease in avian species

Renal disease in birds is frequently encountered. Like most other animals, birds are susceptible to a full spectrum of renal insults,such as toxins, tumors, infections, and degenerative conditions. Accurate diagnosis of renal disease is based on a complete history,physical examination, and laboratory evaluation of the patient. Because it is often required for a more definitive diagnosis, special attention is given to histopathologic evaluation of renal tissue,whether through a premortem biopsy or collection at gross necropsy.

Complete nucleotide sequence of polyomavirus SA12

The Polyomaviridae have small icosahedral virions that contain a genome of approximately 5,000 bp of circular double-stranded DNA. Polyomaviruses infect hosts ranging from humans to birds, and some members of this family induce tumors in test animals or in their natural hosts. We report the complete nucleotide sequence of simian agent 12 (SA12), whose natural host is thought to be Papio ursinus, the chacma baboon. The 5,230-bp genome has a genetic organization typical of polyomaviruses. Sequences encoding large T antigen, small t antigen, agnoprotein, and the viral capsid proteins VP1, VP2, and VP3 are present in the expected locations. We show that, like its close relative simian virus 40 (SV40), SA12 expresses microRNAs that are encoded by the late DNA strand overlapping the 3' end of large T antigen coding sequences. Based on sequence comparisons, SA12 is most closely related to BK virus (BKV), a human polyomavirus. We have developed a real-time PCR test that distinguishes SA12 from BKV and the other closely related polyomaviruses JC virus and SV40. The close relationship between SA12 and BKV raises the possibility that these viruses circulate between human and baboon hosts.

Frequent detection of polyomaviruses in stool samples from hospitalized children

BACKGROUND

Infection with BK virus (BKV) generally occurs early during life, but its mode of transmission has not been clearly defined. We tested the hypothesis that polyomavirus shedding in stool may be a source of BKV exposure.METHODS. Pediatric stool and rectal swab samples were tested for the presence of polyomavirus DNA by a polymerase chain reaction (PCR) assay that could detect a conserved region in the large T antigen gene of BKV, JC virus (JCV), and simian virus 40 (SV40). The specific viruses detected by this assay were confirmed by DNA sequence analysis of the PCR amplicons.Results. Of 120 samples collected from 99 patients, 54 (45.0%) were positive for polyomavirus DNA. Of the 99 patients, 46 (46.5%) had at least 1 positive sample, with 38 (38.4%) positive for BKV and 8 (8.1%) positive for SV40. JCV was not detected. There was no association between polyomavirus fecal shedding and age, sex, race/ethnicity, immune status, or symptoms of gastrointestinal disease in the children studied. The BKV strains detected displayed polymorphisms in the T antigen sequence.Conclusions. Polyomaviruses are frequently present in stool samples from hospitalized children. These findings suggest that fecal-oral transmission of BKV may play a role in the ubiquity of infection.

Haemorrhagic nephritis and enteritis of geese: pathomorphological investigations and proposed pathogenesis

Haemorrhagic nephritis and enteritis of geese as a new disease was first described in Hungary in 1969. The authors identified the causative agent of the outbreaks occurring in 1969 as a polyomavirus by PCR in 2001. In order to study the pathogenesis of the virus, one-day-old goslings were infected with tissue homogenate that tested positive for polyomavirus by PCR. Morphological, light and transmission electron microscopic (TEM) examinations have revealed that goose haemorrhagic polyomavirus replicates in the endothelial cells of the blood vessels and capillaries of diseased birds. Infection causes damage and necrosis of the endothelial cells. The virus was not observed in the parenchymal cells. Oedema and haemorrhages found throughout the body may be due to the dysfunction or functional deficiency of endothelial cells damaged by the virus.

Pathology of spontaneous and experimental infections by Goose haemorrhagic polyomavirus

Haemorrhagic nephritis enteritis of geese (HNEG) is a fatal disease of geese aged from 3 to 12 weeks. The causative virus, Goose haemorrhagic polyomavirus (GHPV), is a member of the Polyomaviridae family We examined goslings either spontaneously or experimentally infected with GHPV. Tissues were sampled for histology, GHPV DNA detection and electron microscopy. Clinical signs and gross lesions observed in experimentally infected goslings were largely consistent with those noticed in field cases. Histological examination showed that, in the acute phase of HNEG, GHPV replicates in almost all the tissues with a particular tropism for endothelial and lymphoid cells. Haemorrhagic foci were widespread in many tissues, including brain. Ultrastructural features were largely consistent with other polyomavirus infections, with accumulation of virions in the nucleus. Non-typical, double-membraned organelles were observed in the cytoplasm. GHPV DNA distribution was widespread in tissues of infected birds, from day 5 post-infection. GHPV therefore induces a systemic disease in its host, leading to severe vascular dysfunction and immunosuppressive B-cell depletion.

Development and evaluation of a blocking enzyme-linked immunosorbent assay for detection of avian metapneumovirus type C-specific antibodies in multiple domestic avian species

The first cases of infection caused by avian metapneumoviruses (aMPVs) were described in turkeys with respiratory disease in South Africa during 1978. The causative agent was isolated and identified as a pneumovirus in 1986. aMPVs have been detected in domestic nonpoultry species in Europe, but tests for the detection of these viruses are not available in the United States. To begin to understand the potential role of domestic ducks and geese and wild waterfowl in the epidemiology of aMPV, we have developed and evaluated a blocking enzyme-linked immunosorbent assay (bELISA) for the detection of aMPV type C (aMPV-C)-specific antibodies. This assay method overcomes the species-specific platform of indirect ELISAs to allow detection of aMPV-C-specific antibodies from potentially any avian species. The bELISA was initially tested with experimental turkey serum samples, and the results were found to correlate with those of virus neutralization assays and indirect enzyme-linked immunosorbent assay (iELISA). One thousand serum samples from turkey flocks in Minnesota were evaluated by our bELISA, and the level of agreement of the results of the bELISA and those of the iELISA was 94.9%. In addition, we were able to show that the bELISA could detect aMPV-C-specific antibodies from experimentally infected ducks, indicating its usefulness for the screening of serum samples from multiple avian species. This is the first diagnostic assay for the detection of aMPV-C-specific antibodies from multiple avian species in the United States.

Generation of recombinant virus-like particles of human and non-human polyomaviruses in yeast Saccharomyces cerevisiae

OBJECTIVES

Non-viral methods of gene transfer have been preferred in gene therapy approaches for several reasons, particularly for their safety, simplicity and convenience in introducing heterologous DNA into cells. Polyomavirus virus-like particles (VLPs) represent a promising carrier for encapsidation of foreign nucleic acids for gene therapy. For the development of such gene delivery systems as well as for providing reagents for improving virus diagnostics, an efficient yeast expression system for the generation of different polyomavirus VLPs was established.

METHODS

A galactose-inducible Saccharomyces cerevisiae yeast expression system was used. Formation of empty VLPs was confirmed by cesium chloride ultracentrifugation, agarose gel electrophoresis and electron microscopy. Cross-reactivity of the major capsid proteins (VP1) of different polyomaviruses was analyzed by Western blot using rabbit and mice sera raised against the VP1 proteins.

RESULTS

VP1 of polyomaviruses from humans (JC polyomavirus and serotypes AS and SB of BK polyomavirus), rhesus monkeys (simian virus 40), hamsters (hamster polyomavirus), mice (murine polyomavirus) and birds (budgerigar fledgling disease virus) were expressed at high levels in yeast. Empty VLPs formed by all yeast-expressed VP1 proteins were dissociated into pentamers and reassociated into VLPs by defined ion and pH conditions. Different patterns of cross-reactivity of the VP1 proteins with heterologous mice and rabbit sera were observed.

CONCLUSION

The developed heterologous yeast expression system is suitable for high-level production of polyomavirus VLPs. Yeast-derived VLPs are generally free of toxins, host cell DNA and proteins. These VLPs might be useful for the generation of new diagnostical tools, gene delivery systems and antiviral vaccines.

The genome of goose hemorrhagic polyomavirus, a new member of the proposed subgenus Avipolyomavirus

The full-length genome of goose hemorrhagic polyomavirus (GHPV), the ethiologic agent of hemorrhagic nephritis and enteritis of geese, was cloned and sequenced. Transfection of the circular ds DNA with a size of 5256 bp and an organisation typical of polyomaviruses produced viral progeny in cultured goose cells. According to the splicing sites determined by RT-PCR, five open reading frames (ORFs) were found to encode putative proteins with significant similarities to large T antigen and small t antigen as well as VP1, VP2, and VP3 of other polyomaviruses. An additional ORF located in the 5' region of late mRNA, with a coding capacity for 169 amino acids, shows a low degree of homology to VP4 of avian polyomavirus (APV). The alignment of nucleotide sequences and amino acid sequences revealed a relatively close relationship between GHPV and APV. Therefore, grouping of this new polyomavirus into the proposed subgenus Avipolyomavirus is suggested.

Experimental infection of turkeys with avian pneumovirus and either Newcastle disease virus or Escherichia coli

Avian pneumoviruses (APVs) are RNA viruses responsible for upper respiratory disease in poultry. Experimental infections are typically less severe than those observed in field cases. Previous studies with APV and Escherichia coli suggest this discrepancy is due to secondary agents. Field observations indicate APV infections are more severe with concurrent infection by Newcastle disease virus (NDV). In the current study, we examined the role of lentogenic NDV in the APV disease process. Two-week-old commercial turkey poults were infected with the Colorado strain of APV. Three days later, these poults received an additional inoculation of either NDV or E. coli. Dual infection of APV with either NDV or E. coli resulted in increased morbidity rates, with poults receiving APV/NDV having the highest morbidity rates and displaying lesions of swollen infraorbital sinuses. These lesions were not present in the single APV, NDV, or E coli groups. These results demonstrate that coinfection with APV and NDV can result in clinical signs and lesions similar to those in field outbreaks of APV.

Serological status for Chlamydophila psittaci, Newcastle disease virus, avian polyoma virus, and Pacheco disease virus in scarlet macaws (Ara macao) kept in captivity in Costa Rica

From 1998 to 1999, a total of 128 blood samples were collected from scarlet macaws (Ara macao), kept in captivity in 11 different aviaries located in six provinces of Costa Rica. The sera were examined for antibodies directed against Chlamydophila psittaci, Newcastle disease virus (NDV), avian polyoma virus (APV), and Pacheco disease virus (PDV). Testing by enzyme-linked immunosorbent assay (ELISA), showed 16 (12.39%) of the samples (n = 129) exhibited antibodies directed against C. psittaci. Employing haemagglutination inhibition tests for NDV antibodies, all of the samples were found to be negative. The prevalence of antibodies specific for APV was tested with a blocking ELISA and serum neutralization tests (SNT) and 12 of 128 samples (9.37%) were found to be positive with both tests. In SNT, two out of 128 samples (1.56%) were positive for PDV. This is the first description of the serological status in scarlet macaws in captivity in Costa Rica. The study demonstrates the absence of NDV antibodies in the birds investigated on one hand, but also indicates a health hazard for numerous avian species due to the risk of infections with C. psittaci, APV or PDV.