Abstract
Nhumirim virus (NHUV) is an insect-specific virus that phylogenetically affiliates with dual-host mosquito-borne flaviviruses. Previous in vitro co-infection experiments demonstrated prior or concurrent infection of Aedes albopictus C6/36 mosquito cells with NHUV resulted in a 10,000-fold reduction in viral production of West Nile virus (WNV). This interference between WNV and NHUV was observed herein in an additional Ae. albopictus mosquito cell line, C7-10. A WNV 2K peptide (V9M) mutant capable of superinfection with a pre-established WNV infection demonstrated a comparable level of interference from NHUV as the parental WNV strain in C6/36 and C7-10 cells. Culex quinquefasciatus and Culex pipiens mosquitoes intrathoracically inoculated with NHUV and WNV, or solely with WNV as a control, were allowed to extrinsically incubate the viruses up to nine and 14 days, respectively, and transmissibility and replication of WNV was determined. The proportion of Cx. quinquefasciatus mosquitoes capable of transmitting WNV was significantly lower for the WNV/NHUV group than the WNV control at seven and nine days post inoculation (dpi), while no differences were observed in the Cx. pipiens inoculation group. By dpi nine, a 40% reduction in transmissibility in mosquitoes from the dual inoculation group was observed compared to the WNV-only control. These data indicate the potential that infection of some Culex spp. vectors with NHUV could serve as a barrier for efficient transmissibility of flaviviruses associated with human disease.
Highlights
The genus Flavivirus is comprised of 53 virus species of enveloped, single-stranded, positive-sense RNA viruses
Phylogenetic analyses of flaviviruses have demonstrated clustering based on host preference range: insect-specific flaviviruses (ISFs), dual-host tick-borne flaviviruses (TBFVs), viruses with no known vector (NKV), or mosquito-borne flaviviruses (MBFVs) [4,5]
Data presented indicate productive infection and subsequent oral transmission of Nhumirim virus (NHUV) following intrathoracic inoculation in Cx. pipiens and Cx. quinquefasciatus mosquitoes; the relevance of the transmissibility of NHUV orally by salivation has yet to be determined in the context of its potential insect-specific host restrictive phenotype [6]
Summary
The genus Flavivirus (family Flaviviridae) is comprised of 53 virus species of enveloped, single-stranded, positive-sense RNA viruses. A number of studies have assessed the relative potential of different ISFs [Culex flavivirus (CxFV) and Palm Creek virus (PCV)] to interfere with replication of flaviviruses of human health importance in cultured mosquito cells. In a study performed with sequentially infected Culex quinquefasciatus, no differences in infection, dissemination, or transmission were observed When these mosquitoes were co-inoculated with CxFV and WNV, a higher percentage of mosquitoes were observed to transmit WNV while no difference was observed in the other mosquito colony [25]. Results described indicate the potential for in vivo SIE that results in reduced transmissibility of WNV These data indicated the potential modulatory effect of certain pre-existing flaviviruses on the capacity for establishment of WNV superinfection in mosquitoes and highlights a potential method for blocking mosquito infection as a public health measure
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