Requirement of Glycosylation of West Nile Virus Envelope Protein for Infection of, but Not Spread within, Culex quinquefasciatus Mosquito Vectors

Abstract

Most of sequenced West Nile virus (WNV) genomes encode a single N-linked glycosylation site on their envelope (E) proteins. We previously found that WNV lacking the E protein glycan was severely inhibited in its ability to replicate and spread within two important mosquito vector species, Culex pipiens and Cx. tarsalis. However, recent work with a closely related species, Cx. pipiens pallens, found no association between E protein glycosylation and either replication or dissemination. To examine this finding further, we expanded upon our previous studies to include an additional Culex species, Cx. quinquefasciatus. The non-glycosylated WNV-N154I virus replicated less efficiently in mosquito tissues after intrathoracic inoculation, but there was little difference in replication efficiency in the midgut after peroral infection. Interestingly, although infectivity was inhibited when WNV lacked the E protein glycan, there was little difference in viral spread throughout the mosquito. These data indicate that E protein glycosylation affects WNV–vector interactions in a species-specific manner.

Vector Competence of Culex neavei and Culex quinquefasciatus (Diptera: Culicidae) from Senegal for Lineages 1, 2, Koutango and a Putative New Lineage of West Nile Virus

“…26,62 Previous studies on mosquito vector competence have shown that glycosylation of WN virus envelope protein can affect the efficiency of viral replication and transmission and is mosquito colony or species dependent. 27,29 In our study, only strains with NYS were detected in mosquito saliva, whereas Koutango and lineage 2, which contain NFS or a deletion of the entire motif, respectively, were never detected in saliva. These data suggest that the presence or absence of the glycosylation site, and also its amino acid composition, could play an important role in vector competence and reinforce previous data.…”

“…These data suggest that the presence or absence of the glycosylation site, and also its amino acid composition, could play an important role in vector competence and reinforce previous data. [27][28][29] However, the absence from Cx. quinquefasciatus saliva of the putative new lineage 8, which contained also NYS motif and the presence of other variable regions through the envelope protein, showed that other viral determinants are also implicated in the vector competence.…”

“…[30][31][32] However, WN virus epidemiology in Africa differs from that seen in the United States or Romania where about one-fifth (20%) of WN virus human infections are symptomatic, and 1 in 150 (0.7%) develops neurological disease. 29,[33][34][35] These rates are much higher than those reported in Egypt and South Africa, where neurological disease is rare. 30,35 In addition, in countries like Senegal, seroprevalence of WN virus antibodies can be up to 80% in humans, horses, birds, and virus repeatedly isolated from mosquitoes and wild vertebrates hosts, however no WN virus outbreak has ever been reported.…”

Invasion Biology ofAedes japonicus japonicus(Diptera: Culicidae)

“…In the United States, Ae. j. japonicus has been found infected with West Nile virus (WNV) and La Crosse encephalitis (LAC) (93, 114) and has been found to be a highly competent vector of several other encephalitis viruses in laboratory studies (84–87, 90, 107, 108). Its role as a primary disease vector in North America or Europe is unclear; however, the impact of Ae.…”

Genetic Determinants of Differential Oral Infection Phenotypes of West Nile and St. Louis Encephalitis Viruses in Culex spp. Mosquitoes

“…For instance, glycosylation of the WNV E protein has been directly correlated with enhanced mosquito infectivity. 13,14 Mutations to the dengue virus 2 FG loop of domain III, the fusion peptide involved in virus attachment and entry, resulted in significantly decreased infection rates in Aedes aegypti RexD mosquitoes. 15 Additionally, studies with yellow fever-17D vaccine virus and related chimeras revealed the importance of specific structural elements for flavivirus dissemination, 16 further supporting the role of flavivirus structural proteins in mosquito infectivity.…”