Abstract
Mosquito viruses cause unpredictable outbreaks of disease. Recently, several unassigned viruses isolated from mosquitoes, including the Omono River virus (OmRV), were identified as totivirus-like viruses, with features similar to those of the Totiviridae family. Most reported members of this family infect fungi or protozoans and lack an extracellular life cycle stage. Here, we identified a new strain of OmRV and determined high-resolution structures for this virus using single-particle cryo-electron microscopy. The structures feature an unexpected protrusion at the five-fold vertex of the capsid. Disassociation of the protrusion could result in several conformational changes in the major capsid. All these structures, together with some biological results, suggest the protrusions’ associations with the extracellular transmission of OmRV.
Highlights
Mosquitoes carry a variety of viruses, some of which spread only among mosquitoes, while others are transmitted from mosquitoes to humans or other hosts, causing severe diseases of hosts [1,2]
Current researches have reported the extracellular transmission ability of Omono River virus (OmRV), which is lacked in most members of Totiviridae
Several novel unassigned mosquito-specific viruses, such as Omono River virus (OmRV) [7], or mosquito-borne viruses, such as Armigeres subalbatus totivirus (AsTV) [8], were identified as being related to the viral family Totiviridae based on phylogenetic analyses and temporarily nominated as “totivirus-like viruses”
Summary
Mosquitoes carry a variety of viruses, some of which spread only among mosquitoes (mosquitospecific), while others are transmitted from mosquitoes to humans or other hosts (mosquitoborne), causing severe diseases of hosts (e.g., dengue virus) [1,2]. Several novel unassigned mosquito-specific viruses, such as Omono River virus (OmRV) [7], or mosquito-borne viruses, such as Armigeres subalbatus totivirus (AsTV) [8], were identified as being related to the viral family Totiviridae based on phylogenetic analyses and temporarily nominated as “totivirus-like viruses”. Members of Totiviridae infect either fungi or a number of medically important protozoan parasites, such as Trichomonas, Leishmania and Giardia [9,10,11,12,13], and most of them are incapable of extracellular transmission; rather, they are transmitted vertically through cell division or cell fusion [10,11,12,13]. Several “totivirus-like viruses” (including the mosquito viruses OmRV and AsTV mentioned above) have been found to be infectious in metazoan cell cultures or individual organisms, suggesting that they are capable of extracellular transmission [7,8,15,16,17]
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