Abstract
Mosquitoes are colonized by a little-studied natural virome. Like the bacterial microbiome, the virome also probably influences the biology and immunity of mosquito vector populations, but tractable experimental models are lacking. We recently discovered two novel viruses in the virome of wild Anopheles and in colonies of the malaria vector Anopheles coluzzii: Anopheles C virus and Anopheles cypovirus. Here, we describe biological interactions between these two viruses and An. coluzzii mosquitoes. Viral abundance varies reproducibly during mosquito development. DNA forms of these viruses were not detected, and thus viral persistence is likely based on vertical transmission of RNA genomes. At least Anopheles C virus is vertically transmitted by an intraembryonic route. Relative abundance of the two viruses is inversely correlated in individual mosquitoes. One possible mechanism for this could be interactions with host immunity, and functional genomic analysis indicated differential influence of at least the Toll and JAK/STAT immune signaling pathways upon the viruses. The nonrandom distributions and interactions with host immunity suggest that these and other members of the natural virome may constitute a source of unrecognized heterogeneity in mosquito vector populations.
Highlights
Anopheles species are the main vectors of human malaria
It was previously shown that Anopheles C virus (AnCV) and Anopheles cypovirus (AnCPV) are present in the natural virome of wild Anopheles, and in Anopheles laboratory colonies, including all colonies of An. coluzzii tested to date[16]
Despite the presence of at least 51 viruses detected in Anopheles species worldwide[5], AnCV and AnCPV were the only RNA viruses detected in the Ngousso colony of An. coluzzii[16], and the biology of these two viruses is the topic of the current study
Summary
Anopheles species are the main vectors of human malaria. In addition to Plasmodium, Anopheles mosquitoes transmit filarial worms and arboviruses[1,2]. Anopheles-RNA virus interactions have been relatively unexamined, and it is unknown why Anopheles are efficient vectors of human malaria but do not transmit viruses as well as Aedes and Culex mosquitoes. Deep sequencing has recently facilitated discovery of replicating RNA viruses in insects, by identifying viral RNA (viRNA) products of siRNA cleavage of the double-stranded RNA intermediates of active viral replication[15,16] By this approach, we recently identified two viruses in An. coluzzii: Anopheles C virus (AnCV) and Anopheles cypovirus (AnCPV)[16]. Wild Anopheles of diverse species collected in Senegal and Cambodia were positive for AnCPV, and AnCV was present in samples from Senegal Both viruses belong to the natural virome of Anopheles
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