Evolutionary and phenotypic analysis of live virus isolates suggests arthropod origin of a pathogenic RNA virus family

Abstract

The evolutionary origins of arboviruses are unknown because their typical dual host tropism is paraphyletic within viral families. Here we studied one of the most diversified and medically relevant RNA virus families, the Bunyaviridae, in which four of five established genera are transmitted by arthropods. We define two cardinally novel bunyavirus groups based on live isolation of 26 viral strains from mosquitoes (Jonchet virus [JONV], eight strains; Ferak virus [FERV], 18 strains). Both viruses were incapable of replicating at vertebratetypical temperatures but replicated efficiently in insect cells. Replication involved formation of virion-sense RNA (vRNA) and mRNA, including cap-snatching activity. SDS/PAGE, mass spectrometry, and Edman degradation identified translation products corresponding to virion-associated RNA-dependent RNA polymerase protein (RdRp), glycoprotein precursor protein, glycoproteins Gn and Gc, as well as putative nonstructural proteins NSs and NSm. Distinct virion morphologies suggested ancient evolutionary divergence, with bunyavirus-typical morphology for FERV (spheres of 60-120 nm) as opposed to an unusual bimorphology for JONV (tubular virions of 60 × 600 nm and spheres of 80 nm). Both viruses were genetically equidistant from all other bunyaviruses, showing <15% amino acid identity in the RdRp palm domain. Both had different and unique conserved genome termini, as in separate bunyavirus genera. JONV and FERV define two novel sister taxons to the superclade of orthobunyaviruses, tospoviruses, and hantaviruses. Phylogenetic ancestral state reconstruction with probabilistic hypothesis testing suggested ancestral associations with arthropods at deep nodes throughout the bunyavirus tree. Our findings suggest an arthropod origin of bunyaviruses.bunyavirus | arbovirus | insect-specific virus | virus evolution | ancestral reconstruction

Diverse Array of New Viral Sequences Identified in Worldwide Populations of the Asian Citrus Psyllid (Diaphorina citri) Using Viral Metagenomics

“…One year later, another group (18) sequenced RNAs extracted from 70 arthropod species in China, and they discovered sequences in the mosquito (Wuhan mosquito virus 1), cockroach (Wuchang cockraoch virus 1), and water strider (Gerridae) (Sanxia water strider virus 2) that displayed high amino acid similarities to phasmaviruses. During preparation of the manuscript, two other novel bunyavirids isolated from mosquito cell lines, Jonchet virus (JONV) and Ferak virus (FERV), were described (85). JONV and FERV phylogenetically branch from an old common ancestor in a similar manner to unclassified Phasmaviruses (85).…”

“…During preparation of the manuscript, two other novel bunyavirids isolated from mosquito cell lines, Jonchet virus (JONV) and Ferak virus (FERV), were described (85). JONV and FERV phylogenetically branch from an old common ancestor in a similar manner to unclassified Phasmaviruses (85). The discovery of this new group of bunyaviruses in distantly related arthropods highlights the importance of these viruses as potential emerging agents.…”

“…The L, M, and S genome segments encode the RdRp, envelope glycoproteins (Gn and Gc), and nucleocapsid protein (N), respectively (69). The family Bunyaviridae includes the genera Orthobunyavirus, Nairovirus, Phlebovirus, Hantavirus, and Tospovirus as well as a recently proposed genus tentatively named Phasmavirus (85,86). We identified several contigs with amino acid similarity to members of the putative genus Phasmavirus (85).…”

“…The family Bunyaviridae includes the genera Orthobunyavirus, Nairovirus, Phlebovirus, Hantavirus, and Tospovirus as well as a recently proposed genus tentatively named Phasmavirus (85,86). We identified several contigs with amino acid similarity to members of the putative genus Phasmavirus (85). Significant hits included the L, M, and S segments of Wuhan mosquito virus 1 (AJG39267), Wuchang cockraoch virus 1 (AJG39258), and Kigluaik phantom virus (AIA24559) (see Table S2).…”

High-Resolution Metatranscriptomics Reveals the Ecological Dynamics of Mosquito-Associated RNA Viruses in Western Australia

“…Although these insect-specific viruses have no direct impact on public health, they may modulate the transmission of viruses that are pathogenic to vertebrates (3). The development of metagenomic sequencing approaches has therefore led to a reevaluation of the mosquito virome, including the recent discovery of viruses of the families Bunyaviridae (4)(5)(6)(7)(8), Rhabdoviridae (6,(9)(10)(11), Orthomyxoviridae (6,12), Flaviviridae (13)(14)(15), Mesoniviridae (16), and Reoviridae (8,17) as well as of the unclassified Chuvirus (6) and Negevirus (18) groups. In addition, metagenomics surveys have discovered viruses in families not previously known to infect mosquitoes, such as the Iflaviridae, Dicistroviridae, Totiviridae, Chrysoviridae, and Narnaviridae (8,(19)(20)(21)(22).…”