Eden, J.-S. | bioRxiv Science

bioRxiv2018

A divergent hepatitis D-like agent in birds

Hepatitis delta virus (HDV) is currently only found in humans, and is a satellite virus that depends on hepatitis B virus (HBV) envelope proteins for assembly, release and entry. Using meta-transcriptomics, we identified the genome of a novel HDV-like agent in ducks. Sequence analysis revealed secondary structures that were shared with HDV, including self-complementarity and ribozyme features. The predicted viral protein shares 32% amino acid similarity to the small delta antigen of HDV and comprises a divergent phylogenetic lineage. The discovery of an avian HDV-like agent has important implications for the understanding of the origins of HDV and subviral agents.\n\nImportanceHepatitis delta virus (HDV) is currently only found in humans, and coinfections of HDV and Hepatitis B virus (HBV) in humans result in severe liver disease. There are a number of hypotheses for the origin of HDV, although a key component of all is that HDV only exists in humans. Here, we describe a novel deltavirus-like agent identified in wild birds. Although this agent is genetically divergent, it exhibits important similarities to HDV, such as the presence of ribosymes and self-complementarity. The discovery of an avian HDV-like agent challenges our understanding of both the origin and the co-evolutionary relationships of subviral agents with helper viruses.

molecular biology↗

bioRxiv2018

Extensive Diversity of RNA Viruses in Australian Ticks

Understanding the microbiome of ticks in Australia is of considerable interest given the ongoing debate over whether Lyme disease, and its causative agent the bacterium Borrelia burgdorferi senso lato, are present in Australia. The diversity of bacteria infecting Australian ticks has been the subject of a number of studies using both culture and metagenomics based techniques. However, little is known about the virome of Australian ticks, including those that may have the potential to infect mammalian species. We used a meta-transcriptomics approach to reveal the viral diversity within Australian ticks collected from two locations on the central-east coast of Australia, including metropolitan Sydney. From this we identified 19 novel species of RNA virus belonging to 10 families, as well as one previously described RNA virus. The majority of these viruses clustered phylogenetically with arthropod-associated viruses suggesting that they do not utilize mammalian hosts. However, two novel viruses discovered in ticks feeding on bandicoot marsupials clustered closely within the mammalian associated Hepacivirus and Pestivirus genera (Flaviviridae). Notably, another bandicoot tick yielded a novel Coltivirus (Reoviridae) - a group of largely tick-associated viruses containing the known human pathogen Colorado tick fever virus and its relative Eyach virus. Importantly, our transcriptomic data provided no evidence for the presence of B. burgdorferi s.l.. in any tick sample, providing further evidence against the presence of Lyme Disease in Australia. In sum, this study reveals that Australian ticks harbor a diverse virome, including some viruses that merit additional screening in the context of emerging infectious disease.\n\nIMPORTANCEEach year a growing number of individuals along the east coast of Australia experience debilitating disease following tick bites. As there is no evidence for the presence of the causative agent of Lyme disease, Borrelia Burgdorferi seno lato, in Australian ticks, the etiological basis of this disease syndrome remains controversial. To characterize the viruses associated with Australian ticks, particularly those that might be associated with mammalian infection, we performed unbiased RNA sequencing on 146 ticks collected across two locations along the coast of New South Wales, Australia. This revealed 19 novel RNA viruses from a diverse set of families. Notably, three of these viruses were related to known mammalian viruses, including one that fell within the genus Coltivirus and related to the human pathogen, Colorado tick fever virus.

microbiology↗