Detection of a novel RNA virus with hepatitis E virus-like non-structural genome organization in amphibian, agile frog (Rana dalmatina) tadpoles

In recent years, relatives (bastrovirus, hepelivirus) of hepeviruses (family Hepeviridae) have been reported in a variety of vertebrate hosts. Preliminary studies indicated that inter-viral family recombination events at the junction of the genomes that encodes non-structural (ORF1) and structural protein (ORF2) were implicated in the genesis of hepeviruses. Using viral metagenomics, next generation sequencing and RT-PCR techniques a genetically divergent hepevirus-like RNA virus was identified and characterized from agile frog (Rana dalmatina) tadpoles living in aquatic environment in three natural ponds (Mélymocsár, Lake Ilona and Lake Katlan) in the Pilis Mountains, in Hungary. The complete genome of the viral strain agile frog/RD6/2015/HUN (MH330682) is 7188 nt long including a 48-nt 5′ and a 122-nt 3′ non-coding region. Sequence analysis indicated that the agile frog/RD6/2015/HUN genome has potentially three non-overlapping ORFs. ORF1 (4740 nt/1579aa) has a hepevirus-like non-structural genome organization and encodes several hepevirus-like amino acid sequence motifs. The ORF2 is a potential capsid protein. The functions of the ORF3 were not predictable. The study virus was present in 18 (46%) of the 39 faecal specimen pools from agile frog tadpoles. The taxonomic position of this novel virus is presently unknown.