NKFI-6 OTKA K100163 | Study of the diversity of adenoviruses and some other viruses in vertebrate animals

We screened different, mainly poikilothermic animals for novel adenoviruses and other DNA viruses. We perform the genetic characterization and the identification of the taxonomical place of these viruses.

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NKFI-6 OTKA K100163

Our research team has been playing an internationally important role in revealing the diversity of adenoviruses that occur in wild and domesticated animals. We also had a crucial impact on the clarification of the genetic relationships among these viruses, as well as on the reformation of the official taxonomy of the family Adenoviridae. This virus family had previously been divided into two genera (Mastadenovirus and Aviadenovirus). Presently it contains five genera out of which three (Atadenovirus, Siadenovirus, Ichtadenovirus) have been recognized by our group and was officially accepted upon our proposals. More recently, we have provided significant data for the amelioration of the taxonomy of fish herpesviruses. We have proved that, besides the viruses of ictalurid fishes, certain herpesviruses of acipenserid fish should also be classified into the genus Ictalurivirus of the newly established family Alloherpesviridae. We have performed phylogenetic analyses as well as whole genome sequencing projects which allowed the determination of the characteristic features in the genome organization of members of the different taxons (genus or species). Up to now, we have studied primarily the adenoviruses of farm animals having veterinary importance. Our research on the fish herpesviruses was also fuelled by the considerable economic losses these viruses can cause to fish industry. According to the results of our presently ongoing examinations, it is likely that the actual number of different virus types in both virus families might be much higher (perhaps by several orders of magnitude) than that of their members recognized to date. The majority of these yet undiscovered viruses would probably represent a number of yet unknown lineages that should probably be considered as new genera. To find such new viruses, we plan to conduct PCR-based screenings on a sample collection representing the possible widest palette of host animals. The genetic analysis of each new virus that seems to be different enough will be tried to be completed.

For the screenings, the internal organs (liver, spleen, intestines and lungs) of dead animals, or faecal samples or cloacal swabs of live animals will be collected. We will aim to enrich our large collection so that preferably the most exotic groups of vertebrates be also represented. Viral DNA fragments amplified by PCR will be sequenced, and the sequences will be submitted to preliminary phylogenetic calculations. Based on these preliminary results, the viruses most outstanding according to their host origin and/or phylogenetic place will be selected for further detailed genome analyses. The samples can be further screened for the presence of herpes- and parvoviruses, or any other emerging (or eventually zoonotic) viruses. The genomic characterization of the newly detected viruses will be carried out even if the isolation of the virus is not successful. Special attention will be paid to those animals groups (reptiles, birds and bats) that have already proved to be a rich source of different viruses. The viruses carried by fish and amphibians would also be examined. According to our experiences, the infection of these animals is rare; therefore the recognition of new viruses bears greater importance in these animals. Full or partial genome sequence of the new viruses would be determined, analysed and after phylogenetic calculations, proposals for their classification would be made.

The successful performance of the planned studies is expected to result in the discovery of several new adeno-, herpes-, circo- and parvoviruses. There are a couple of examples of adenoviruses switching between taxonomically distant hosts. Generally in such cases, the viruses seem to have an elevated pathogenicity in the new host. This is why knowing the diversity and abundance of viruses occurring in wild living animal is important. There are several, important animal diseases, such as the egg drop syndrome of laying hens or the haemorrhagic enteritis of turkeys, which are caused by adenoviruses significantly different from the lineage (Aviadenovirus) supposed to have coevolved with birds. The parvoviruses of vertebrates belong to the subfamily Parvovirinae of the family Parvoviridae. This subfamily presently contains only mammalian and avian parvoviruses. The snake parvovirus, described by us with Canadian cooperation, is the only parvovirus originating from a lower vertebrate. It is proposed to be a member of the genus Dependovirus in which other animal pathogens, for example the causative agent of the Derzsy’s disease belong. The results of the planned surveys would contribute to the understanding of the genetic and evolutionary relationships among these viruses, and could help in the assessment of the environmental risk menacing farm animals. After careful evaluation of the results, our PCR methods intended for the general detection of members of certain virus families, or for the specific detection of the members of particular genera could be fine-tuned and complemented with recommendations for diagnostic virus typing.

We discovered the representatives of a novel, sixth adenovirus genus in sliders. The picture shows a red-eared slider (Trachemys scripta elegans), an invasive species.

We discovered the representatives of a novel, sixth adenovirus genus in sliders. The picture shows a red-eared slider (Trachemys scripta elegans), an invasive species.

Photo: Benkő, Mária Dr.