An adenovirus, FAV-1, isolated from the kidney of a frog (Rana pipiens)

Opportunistic sampling of wild native and invasive birds reveals a rich diversity of adenoviruses in Australia

Little is known about the diversity of adenoviruses in wild birds and how they have evolved and are maintained in complex ecosystems. In this study, 409 samples were collected from woodland birds caught for banding (droppings), birds submitted to a wildlife hospital (droppings and tissues), silver gulls (droppings or tissues), and feral pigeons (Columbia livia; oral, cloacal swabs, or tissues) from the Greater Sydney area in NSW, Australia. Additional samples were from native pigeons and doves (swabs) presented to the Healesville Sanctuary, VIC, Australia. Samples were screened for adenovirus DNA using degenerate primers and polymerase chain reaction. Adenovirus sequences were detected in eighty-three samples representing thirty-five novel amino acid sequences. Fourteen novel sequences were atadenoviruses, seven were aviadenoviruses, twelve were siadenoviruses, and one was a mastadenovirus. Sequences from passerine birds were predominately found to form a single lineage within the atadenoviruses, a second lineage in the siadenoviruses, and a third smaller aviadenovirus lineage. These viruses appeared to have co-evolved with a diverse group of woodland birds that share similar habitat. Evidence for host/virus co-evolution in some viruses and a wide host range in others was observed. A high prevalence of adenovirus infection was found in rainbow lorikeets (Trichoglossus haematodus), galahs (Eolophus roseicapilla), and sulphur-crested cockatoos (Cacatua galerita). Sequences were either identical to or mapped to already established lineages in the Aviadenovirus, Siadenovirus, and Atadenovirus genera, suggesting a possible origin of the psittacine adenoviruses in ancestral Australian psittacine birds. The sequences of passerine and psittacine origin provided insight into diversity and structure of the Atadenovirus genus and demonstrated for the first-time viruses of passerine origin in the Aviadenovirus genus. Four unrelated adenovirus sequences were found in silver gull samples (Chroicocephalus novaehollandiae), including one of pigeon origin, suggesting environmental virus exposure. Three pigeon adenovirus types were detected in feral pigeons and infection prevalence was high. Evidence for host switching between invasive species and native species and native species and invasive species was documented. A variant of a murine adenovirus was detected in kidney tissue from two bird species suggesting mouse to bird transmission.

Dose Effects of Recombinant Adenovirus Immunization in Rodents

Recombinant adenovirus type 5 (rAd) has been used as a vaccine platform against many infectious diseases and has been shown to be an effective vaccine vector. The dose of the vaccine varies significantly from study to study, making it very difficult to compare immune responses and vaccine efficacy. This study determined the immune correlates induced by serial dilutions of rAd vaccines delivered intramuscularly (IM) and intranasally (IN) to mice and rats. When immunized IM, mice had substantially higher antibody responses at the higher vaccine doses, whereas, the IN immunized mice showed a lower response to the higher rAd vaccine doses. Rats did not show dose-dependent antibody responses to increasing vaccine doses. The IM immunized mice and rats also showed significant dose-dependent T cell responses to the rAd vaccine. However, the T cell immunity plateaued in both mice and rats at 10⁹ and 10¹⁰ vp/animal, respectively. Additionally, the highest dose of vaccine in mice and rats did not improve the T cell responses. A final vaccine analysis using a lethal influenza virus challenge showed that despite the differences in the immune responses observed in the mice, the mice had very similar patterns of protection. This indicates that rAd vaccines induced dose-dependent immune responses, especially in IM immunized animals, and that immune correlates are not as predictive of protection as initially thought.

Complete sequence of raptor adenovirus 1 confirms the characteristic genome organization of siadenoviruses

Currently, the family Adenoviridae contains five genera, out of which Siadenovirus is one of the two least densely populated ones. A new member representing a new species in this genus has been detected in various birds of prey. The virus, named raptor adenovirus 1 (RAdV-1), could not be isolated, probably because no appropriate permissive cell-line was available. Partial genomic sequences, obtained by PCR and suggesting that the virus is a new siadenovirus species, have been published earlier. In the present paper, determination and analysis of the complete RAdV-1 genome are reported. This is the first complete genome sequence acquired from a non-isolated adenovirus (AdV). The sole source was a mixture of the internal organs of the diseased and dead birds. Until now, the genomic organization considered characteristic to siadenoviruses had been deduced from the detailed study of only two virus species, one of which originated from birds and the other from a frog. The present analysis of RAdV-1 confirmed the genus-specific genetic content and genomic features of siadenoviruses, and a putative novel gene was found as well. In general, AdVs and most of the AdV genera are thought to be strictly host specific. In the genus Siadenovirus, however, two virus species of rather divergent (avian and amphibian) host origin were present when the genus was found. Although by now the greatest number of known siadenoviruses infect birds, the original hosts of the genus remain unknown.

Confirmation of a novel siadenovirus species detected in raptors: partial sequence and phylogenetic analysis

Partial genome characterisation of a novel adenovirus, found recently in organ samples of multiple species of dead birds of prey, was carried out by sequence analysis of PCR-amplified DNA fragments. The virus, named as raptor adenovirus 1 (RAdV-1), has originally been detected by a nested PCR method with consensus primers targeting the adenoviral DNA polymerase gene. Phylogenetic analysis with the deduced amino acid sequence of the small PCR product has implied a new siadenovirus type present in the samples. Since virus isolation attempts remained unsuccessful, further characterisation of this putative novel siadenovirus was carried out with the use of PCR on the infected organ samples. The DNA sequence of the central genome part of RAdV-1, encompassing nine full (pTP, 52K, pIIIa, III, pVII, pX, pVI, hexon, protease) and two partial (DNA polymerase and DBP) genes and exceeding 12 kb pairs in size, was determined. Phylogenetic tree reconstructions, based on several genes, unambiguously confirmed the preliminary classification of RAdV-1 as a new species within the genus Siadenovirus. Further study of RAdV-1 is of interest since it represents a rare adenovirus genus of yet undetermined host origin.

Amphibian virology

Amphibians are a diverse group of species; much work remains to be done to elucidate the viruses of amphibians. Viral diseases may play an important role in wild and captive amphibian populations. Iridoviruses are a leading cause of wild amphibian mortality events in the United States and are a common cause of amphibian mortality events worldwide. In addition to frank viral diseases, viral infections may play a role in the establishment of bacterial, fungal, and parasitic diseases and are an underlying cause of neoplasia. It is important for the amphibian clinician to recognize disease syndromes and pathology that are consistent with viral etiology.

First molecular evidence for the existence of distinct fish and snake adenoviruses

From adenovirus-like viruses originating from a fish and a snake species, a conserved part of the adenoviral DNA polymerase gene was PCR amplified, cloned and sequenced. Phylogenetic analysis showed that the snake adenovirus is closely related to the members of the proposed genus Atadenovirus, whereas the fish isolate seems to represent a separate cluster, likely a new genus.

Genomic and phylogenetic analyses of an adenovirus isolated from a corn snake (Elaphe guttata) imply a common origin with members of the proposed new genus Atadenovirus

Approximately 60% of the genome of an adenovirus isolated from a corn snake (Elaphe guttata) was cloned and sequenced. The results of homology searches showed that the genes of the corn snake adenovirus (SnAdV-1) were closest to their counterparts in members of the recently proposed new genus ATADENOVIRUS: In phylogenetic analyses of the complete hexon and protease genes, SnAdV-1 indeed clustered together with the atadenoviruses. The characteristic features in the genome organization of SnAdV-1 included the presence of a gene homologous to that for protein p32K, the lack of structural proteins V and IX and the absence of homologues of the E1A and E3 regions. These characteristics are in accordance with the genus-defining markers of atadenoviruses. Comparison of the cleavage sites of the viral protease in core protein pVII also confirmed SnAdV-1 as a candidate member of the genus ATADENOVIRUS: Thus, the hypothesis on the possible reptilian origin of atadenoviruses (Harrach, Acta Veterinaria Hungarica 48, 484-490, 2000) seems to be supported. However, the base composition of DNA sequence (>18 kb) determined from the SnAdV-1 genome showed an equilibrated GC content of 51%, which is unusual for an atadenovirus.

DNA sequence of frog adenovirus

The genome of frog adenovirus (FrAdV-1) was sequenced and found to be the smallest of all known adenovirus genomes. The sequence obtained was 26163 bp in size and contains a substantial direct repeat near the right terminus, implying that it was derived by recombination from a parental genome of only 25517 bp. The closest relative of FrAdV-1 proved to be turkey adenovirus 3, an avian adenovirus with no previously known near relative. Sequence comparisons showed that the two viruses have equivalent gene complements, including one gene the product of which is related to sialidases. Phylogenetic analyses supported the establishment of a fourth adenovirus genus containing these two viruses, in addition to the established genera Mastadenovirus: and Aviadenovirus: and the proposed genus Atadenovirus: Sixteen genes were identified as being conserved between these four lineages and were presumably inherited from an ancestral adenovirus.

Pathological and microbiological findings from incidents of unusual mortality of the common frog (Rana temporaria)

In 1992 we began an investigation into incidents of unusual and mass mortalities of the common frog (Rana temporaria) in Britain which were being reported unsolicited to us in increasing numbers by members of the public. Investigations conducted at ten sites of unusual mortality resulted in two main disease syndromes being found: one characterized by skin ulceration and one characterized by systemic haemorrhages. However, frogs also were found with lesions common to both of these syndromes and microscopic skin lesions common to both syndromes were seen. The bacterium Aeromonas hydrophila, which has been described previously as causing similar lesions, was isolated significantly more frequently from haemorrhagic frogs than from those with skin ulceration only. However, as many of the latter were euthanased, this may have been due to differences in post mortem bacterial invasion. An iridovirus-like particle has been identified on electron microscopical examination of skin lesions from frogs with each syndrome and iridovirus-like inclusions have been detected in the livers of frogs with systemic haemorrhages. Also, an adenovirus-like particle has been cultured from one haemorrhagic frog. A poxvirus-like particle described previously from diseased frogs has now been found also in control animals and has been identified as a melanosome. Both the prevalence of the iridovirus-like particle and its association with lesions indicate that it may be implicated in the aetiology of the disease syndromes observed. Specifically, we hypothesize that primary iridovirus infection, with or without secondary infection with opportunistic pathogens such as A. hydrophila, may cause natural outbreaks of 'red-leg', a disease considered previously to be due to bacterial infection only.

Regulation of the DNA-binding and transcriptional activities of Xenopus laevis NFI-X by a novel C-terminal domain

The nuclear factor I (NFI) family consists of sequence-specific DNA-binding proteins that activate both transcription and adenovirus DNA replication. We have characterized three new members of the NFI family that belong to the Xenopus laevis NFI-X subtype and differ in their C-termini. We show that these polypeptides can activate transcription in HeLa and Drosophila Schneider line 2 cells, using an activation domain that is subdivided into adjacent variable and subtype-specific domains each having independent activation properties in chimeric proteins. Together, these two domains constitute the full NFI-X transactivation potential. In addition, we find that the X. laevis NFI-X proteins are capable of activating adenovirus DNA replication through their conserved N-terminal DNA-binding domains. Surprisingly, their in vitro DNA-binding activities are specifically inhibited by a novel repressor domain contained within the C-terminal part, while the dimerization and replication functions per se are not affected. However, inhibition of DNA-binding activity in vitro is relieved within the cell, as transcriptional activation occurs irrespective of the presence of the repressor domain. Moreover, the region comprising the repressor domain participates in transactivation. Mechanisms that may allow the relief of DNA-binding inhibition in vivo and trigger transcriptional activation are discussed.

Physicochemical properties and cytopathogenicity of an adenovirus-like agent isolated from corn snake (Elaphe guttata)

A virus isolated from the internal organs of a moribund corn snake (Elaphe guttata) replicated in reptilian cell cultures (IgH-2, TH-1 cells) between 10 and 30 degrees C. Highest infectivity titers of 10(5.5) TCID50/ml were obtained in IgH-2 cells at 25 degrees C. Infected IgH-2 cells showed the development of three morphologically different intranuclear inclusion bodies. During viral assembly the particles formed typical crystalline aggregates in the nucleus. About 64 h after infection progressive desintegration of the nuclear membrane was evident and virus particles were released into the cytoplasm. Different fish cell lines (CLC, CHSE-214, BF-2, PG, RTG-2) were not capable of propagating the virus. The DNA containing agent proved to be stable at pH3, more or less at pH 12 and to treatment with chloroform, but it was rapidly inactivated at 56 degrees C. Electron microscopy revealed nonenveloped icosahedral particles with a diameter of 65-70 nm.

The presence of the Lucké herpesvirus genome in induced tadpole tumors and its oncogenicity: Koch-Henle postulates fulfilled

Herpesvirus extracted from a naturally occurring frog renal carcinoma (Lucké tumor) induced virus-free Lucké tumors in developing frogs. Herpesvirus recovered from an induced tumor after incubation at low temperature of tumor fragments cultured in vitro was oncogenic when injected into developing frog embryos. With the exception of the "pure culture" requirement, this experiment fulfills Koch-Henle postulates for the identification of the causative agent of the Lucké tumor.