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Updated: May 24, 2026
Mosquito-Associated Virus Isolation from Field-Collected Mosquitoes
Published on: August 31, 2022
Internally deleted WNV genomes isolated from exotic birds in New Mexico: function in cells, mosquitoes, and mice
Kendra N Pesko1, Kelly A Fitzpatrick, Elizabeth M Ryan
1Department of Pathology, University of New Mexico School of Medicine, Albuquerque, NM, USA. Kendra.Pesko@yale.edu
Abstract:
Most RNA viruses exist in their hosts as a heterogeneous population of related variants. Due to error prone replication, mutants are constantly generated which may differ in individual fitness from the population as a whole. Here we characterize three WNV isolates that contain, along with full-length genomes, mutants with large internal deletions to structural and nonstructural protein-coding regions. The isolates were all obtained from lorikeets that died from WNV at the Rio Grande Zoo in Albuquerque, NM between 2005 and 2007. The deletions are approximately 2kb, in frame, and result in the elimination of the complete envelope, and portions of the prM and NS-1 proteins. In Vero cell culture, these internally deleted WNV genomes function as defective interfering particles, reducing the production of full-length virus when introduced at high multiplicities of infection. In mosquitoes, the shortened WNV genomes reduced infection and dissemination rates, and virus titers overall, and were not detected in legs or salivary secretions at 14 or 21 days post-infection. In mice, inoculation with internally deleted genomes did not attenuate pathogenesis relative to full-length or infectious clone derived virus, and shortened genomes were not detected in mice at the time of death. These observations provide evidence that large deletions may occur within flavivirus populations more frequently than has generally been appreciated and suggest that they impact population phenotype minimally. Additionally, our findings suggest that highly similar mutants may frequently occur in particular vertebrate hosts.
Insights
Large deletions in West Nile virus (WNV) genomes occur frequently in lorikeets. These WNV mutants, while affecting virus replication in cell culture and mosquitoes, did not alter disease severity in mice.
Area of Science:
- Virology
- Molecular Biology
- Genetics
Background:
- RNA viruses, including West Nile virus (WNV), exist as heterogeneous populations with constantly generated mutants due to error-prone replication.
- These mutants can exhibit varying fitness levels compared to the overall viral population.
Purpose of the Study:
- To characterize WNV isolates from deceased lorikeets containing full-length genomes alongside mutants with large internal deletions.
- To investigate the functional impact of these internally deleted WNV genomes in cell culture, mosquitoes, and mice.
Main Methods:
- Isolation and characterization of WNV from infected lorikeets.
- Analysis of viral genomes for large internal deletions (approx. 2kb) affecting structural and nonstructural protein-coding regions.
- Assessment of WNV mutant replication and interference in Vero cell culture.
- Evaluation of WNV mutant infection, dissemination, and titers in mosquitoes.
- Pathogenesis studies of WNV mutants in mice.
Main Results:
- Three WNV isolates contained genomes with approximately 2kb in-frame deletions, eliminating the envelope, prM, and NS-1 proteins.
- In cell culture, deleted WNV genomes acted as defective interfering particles, reducing full-length virus production at high multiplicities of infection.
- In mosquitoes, shortened WNV genomes decreased infection, dissemination rates, and overall virus titers, with no detection in legs or salivary secretions at 14-21 days post-infection.
- In mice, inoculation with internally deleted genomes did not attenuate pathogenesis compared to full-length WNV, and deleted genomes were undetectable at the time of death.
Conclusions:
- Large internal deletions can occur frequently within flavivirus populations, potentially more often than previously recognized.
- These deletions appear to have minimal impact on the overall population phenotype.
- Highly similar WNV mutants may frequently arise in specific vertebrate hosts.
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