West African Anopheles gambiae mosquitoes harbor a taxonomically diverse virome including new insect-specific flaviviruses, mononegaviruses, and totiviruses

Abstract

Anopheles gambiae are a major vector of malaria in sub-Saharan Africa. Viruses that naturally infect these mosquitoes may impact their physiology and ability to transmit pathogens. We therefore used metagenomics sequencing to search for viruses in adult Anopheles mosquitoes collected from Liberia, Senegal, and Burkina Faso. We identified a number of virus and virus-like sequences from mosquito midgut contents, including 14 coding-complete genome segments and 26 partial sequences. The coding-complete sequences define new viruses in the order Mononegavirales, and the families Flaviviridae, and Totiviridae. The identification of a flavivirus infecting Anopheles mosquitoes broadens our understanding of the evolution and host range of this virus family. This study increases our understanding of virus diversity in general, begins to define the virome of a medically important vector in its natural setting, and lays groundwork for future studies examining the potential impact of these viruses on anopheles biology and disease transmission.

A New Clade of Insect-Specific Flaviviruses from Australian Anopheles Mosquitoes Displays Species-Specific Host Restriction

“…fifo seems to be specific to cISFs and is present in all of the cISF sequences investigated to date. With two predicted transmembrane domains, McPV, HaCV, and KRBV (Kim1 strain) follow the consensus established for other ISFs, while KRBV (prototype strain) fifo appears to have only one transmembrane domain (11, 24). …”

“…Coevolution of the Anopheles ISFs with their host species provides an explanation for the narrow host restriction of these viruses and is, to some degree, corroborated by our data, as each virus was detected in a single Anopheles species. This does not preclude the possibility of several viruses being found in the same species in other mosquito populations; two different ISF sequences were detected in A. gambiae from Kenya and Senegal, approximately 8,000 km apart (11, 12). …”

“…So far, cISFs have been isolated predominantly from Aedes or Culex mosquitoes and separate into two phylogenetic clusters according to the genus of their host. Only limited sequencing data have been reported for Anopheles -associated ISFs—one virus from Liberia with two full genome sequences ( Anopheles flavivirus [AnFV]) and four partial sequences from Senegal and Kenya ( Anopheles squamosus flavivirus [AnsFV] and Anopheles gambiae flavivirus [AngFV])—and none have been isolated or characterized (11, 12). …”

Comparative genomics shows that viral integrations are abundant and express piRNAs in the arboviral vectors Aedes aegypti and Aedes albopictus

“…The only arbovirus known to be transmitted by Anophelinae is the alphavirus O’nyong-nyong [9]. Recently, additional RNA viruses have been identified from wild mosquitoes, but their virulence to humans and their impact on vector competence is still uncertain [9–11]. …”

Genomes of viral isolates derived from different mosquitos species

“…During the past decade, advances in DNA sequencing technology have allowed the identification of a wide range of novel viruses associated with mosquitoes (Aguiar et al, 2015; Auguste et al, 2014; Bolling et al, 2015; Carissimo et al, 2016; Chandler et al, 2015; Charles et al, 2016; Cholleti et al, 2016; Coffey et al, 2014; Contreras-Gutierrez et al, 2017; Fauver et al, 2016; Frey et al, 2016; Li et al, 2015a; Li et al, 2015b; Nasar et al, 2012; Ng et al, 2011; Palacios et al, 2015; Pauvolid-Correa et al, 2016; Shi et al, 2015; Simmonds et al, 2017; Vasilakis et al, 2014a; Wang et al, 2015). We examine here, by electron microscopy and metagenomics analysis, 11 mosquito derived viral isolates from the extensive collection of the World Reference Center for Emerging Viruses and Arboviruses (WRCEVA) (https://www.niaid.nih.gov/research/wreceva), whose morphology indicated the likely presence of multi-segmented reoviruses.…”