Isolation and full-length sequence analysis of Armigeres subalbatus totivirus, the first totivirus isolate from mosquitoes representing a proposed novel genus (Artivirus) of the family Totiviridae

During an investigation of arboviruses in China, a novel dsRNA virus was isolated from adult female Armigeres subalbatus. Full genome sequence analysis showed the virus to be related to members of the family Totiviridae, and was therefore named ‘Armigeres subalbatus totivirus’ (AsTV). Transmission electron microscopy identified icosahedral, non-enveloped virus particles with a mean diameter of 40?nm. The AsTV genome is 7510?bp in length, with two ORFs. ORF1 (4443?nt) encodes the coat-protein and a dsRNA-binding domain (which may be involved in the evasion of ‘gene silencing’), while ORF2 (2286?nt) encodes the viral RNA-dependent RNA polymerase (RdRp). The AsTV coat protein shows a higher level of amino acid identity with Drosophila totivirus (DTV, 52?%) than with infectious myonecrosis virus (IMNV, 29?%). Similarly, the RdRp shows higher identity levels with DTV (51?%) than with IMNV (44?%). Identity levels to other members of the family Totiviridae, in either the coat protein or the RdRp, ranged from 6 to 11?%. Based on a recent reassessment of the coding strategy used by IMNV, we suggest that an AsTV coat–RdRp fusion protein could be synthesized via a ?1 frameshift. Elements favouring ?1 frameshift such as ‘slippery heptamers’ and pseudonkots, were identified in the AsTV, DTV and IMNV genomes. AsTV was shown to grow in both mosquito and mammalian cells, suggesting that it is an arbovirus that can infect mammals.