Mária Benko

Detection and Analysis of Six Lizard Adenoviruses by Consensus Primer PCR Provides Further Evidence of a Reptilian Origin for the Atadenoviruses

ABSTRACT A consensus nested-PCR method was designed for investigation of the DNA polymerase gene of adenoviruses. Gene fragments were amplified and sequenced from six novel adenoviruses from seven lizard species, including four species from which adenoviruses had not previously been reported. Host species included Gila monster, leopard gecko, fat-tail gecko, blue-tongued skink, Tokay gecko, bearded dragon, and mountain chameleon. This is the first sequence information from lizard adenoviruses. Phylogenetic analysis indicated that these viruses belong to the genus Atadenovirus, supporting the reptilian origin of atadenoviruses. This PCR method may be useful for obtaining templates for initial sequencing of novel adenoviruses.

Molecular Evolution of Adenoviruses

New advances in the field of genetic characterization of adenoviruses originating from different animal species are summarized. Variations seen in the host range and specificity, pathogenicity, genomic arrangement or gene complement are much wider than expected based on previous studies of human adenoviruses. Several exceptional adenoviruses from the two traditional conventional genera are now removed, and proposed to form at least two new genera. The eventual host origin of the new genera, however, is not clarified. Novel results from the genomic and phylogenetic analyses of adenoviruses originating from lower vertebrate species (including reptiles, amphibians and fish) seem to imply that probably five major clusters of adenoviruses exist corresponding to the five major classes of Vertebrata. Adenoviruses, which are now suspected to have common origin with enterobacterium phages from the family Tectiviridae, are perhaps very ancient indeed, and may have undergone a co-evolution with vertebrate hosts.

A proposal for a new (third) genus within the family Adenoviridae

SummaryThis article presents a proposal for the establishment of a new adenovirus genus to accommodate certain bovine, ovine, and avian adenoviruses with special characteristics which differentiate them from members of the existing genera Mastadenovirus and Aviadenovirus. This proposal has been developed from earlier versions with advice from the Adenovirus Study Group of the International Committee on Taxonomy of Viruses (ICTV).

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

ABSTRACT 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.

Phylogenetic Analysis of Adenovirus Sequences

Members of the family Adenoviridae have been isolated from a large variety of hosts, including representatives from every major vertebrate class from fish to mammals. The high prevalence, together with the fairly conserved organization of the central part of their genomes, make the adenoviruses one of (if not the) best models for studying viral evolution on a larger time scale. Phylogenetic calculation can infer the evolutionary distance among adenovirus strains on serotype, species, and genus levels, thus helping the establishment of a correct taxonomy on the one hand, and speeding up the process of typing new isolates on the other. Initially, four major lineages corresponding to four genera were recognized. Later, the demarcation criteria of lower taxon levels, such as species or types, could also be defined with phylogenetic calculations. A limited number of possible host switches have been hypothesized and convincingly supported. Application of the web-based BLAST and MultAlin programs and the freely available PHYLIP package, along with the TreeView program, enables everyone to make correct calculations. In addition to step-by-step instruction on how to perform phylogenetic analysis, critical points where typical mistakes or misinterpretation of the results might occur will be identified and hints for their avoidance will be provided.

Analysis of the hexon gene sequence of bovine adenovirus type 4 provides further support for a new adenovirus genus (Atadenovirus).

The putative hexon gene of bovine adenovirus type 4 (BAV-4), encoding 910 amino acid residues, has been identified and sequenced. A characteristic codon usage biased towards the use of AT-rich triplets was observed. Comparative analysis with other hexon sequences detected a high level of amino acid identity in the regions corresponding to the pedestals of the hexon. Substitutions, insertions and deletions were identified mainly in the variable regions forming the loops which are exposed on the outer surface of the virion. In these variable regions, BAV-4 shared similarity only with egg drop syndrome (EDS) virus and ovine adenovirus isolate 287 (OAV287). The close relationship of these viruses was also demonstrated by phylogenetic analysis of the hexon gene. In addition to the two groups of the Mastadenovirus and Aviadenovirus genera, a third cluster appeared comprising BAV-4, OAV287 and EDS virus.

Completion of the genome analysis of snake adenovirus type 1, a representative of the reptilian lineage within the novel genus Atadenovirus

Genome sequencing and analysis of snake adenovirus type 1 (SnAdV-1), originating from corn snake, were completed. This is the first full genomic sequence of an adenovirus from reptilian hosts. The presence of characteristic genus-common genes and transcription units, showed that SnAdV-1 shares similar genome organisation with members of the recently established genus Atadenovirus. Three novel open reading frames of yet unknown functions were found. One of these seemed to be related to a putative gene, the so-called 105R that has recently been described from the genome of the tree shrew adenovirus. The other two putative genes were found to be unique for SnAdV-1. On phylogenetic trees, SnAdV-1 clustered within the atadenovirus clade. Thereby the hypothesis on the reptilian origin of atadenoviruses was further strengthened. Interestingly, however, one of the most striking features of atadenoviruses, namely the base content heavily biased towards A+T, is not characteristic for SnAdV-1 having a genome of balanced composition with a G+C value of 50.21%.

Reovirus identified as cause of disease in young geese.

The pathology, epizootiology and aetiology of a specific disease of young geese, which has been seen in Hungary for more than three decades, were investigated. The disease was characterised by splenitis and hepatitis with miliary necrotic foci during the acute phase, and epicarditis, arthritis and tenosynovitis during the subacute/chronic phase. Clinical signs usually appeared at 2 to 3 weeks of age and persisted for 3 to 6 weeks. From different organs of the affected birds, a reovirus was isolated in embryonated eggs and tissue cultures ofMuscovy duck or goose origin, as well as in Vero cells. In experimental infections, the dominant features of thedisease were reproduced in day-old and young goslings. The biological and partial molecular characterisation ofone of the isolated strains (D15/99) showed that it was related to the reovirus described as the cause of a similardisease of Muscovy ducks. An RT-PCR method suitable for the detection of reoviruses was also elaborated andtested. This is the first report on the involvement of reovirus in arthritis of geese.

Toward an Integrated Human Adenovirus Designation System That Utilizes Molecular and Serological Data and Serves both Clinical and Fundamental Virology

Towards an integrated human adenovirus designation system that utilizes molecular and serological data and serves both clinical and fundamental virology