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Characterization of Fort Morgan virus, an alphavirus of the western equine encephalitis virus complex in an unusual
Abstract:
An alphavirus isolated from nestling Cliff Swallows (Petrochelidon pyrrhonota) and House Sparrows (Passer domesticus) and from cimicid bugs (Oeciacus vicarius) in eastern Colorado, for which we propose the name Fort Morgan (FM) virus, is sensitive to the action of sodium deoxycholate, unstable at pH 2.0-4.0, and demonstrates no characteristics of temperature-sensitive mutants. Unpassaged field strains are nonpathogenic, or of low pathogenicity, for suckling mice; however, plaque-purified FM virus is pathogenic for a variety of laboratory hosts. By hemagglutination-inhibition (HI), complement-fixation, and neutralization tests, cross-reactions were observed between FM virus and members of the western equine encephalitis (WEE) virus antigenic complex. Short-incubation HI tests indicated that the new isolate shared closer antigenic relationships with WEE complex virus strains from the eastern United States (Highlands J virus) than with other WEE complex viruses. On the basis of these serological findings, as well as characterization of the structural polypeptides and oligonucleotides, we suggest that FM is a distinct virus belonging to the WEE antigenic complex. A reconsideration of the taxonomy of the WEE complex and discussion of the epizoologic significance of FM virus are presented.
Insights
A new alphavirus, Fort Morgan virus, was identified in birds and insects in Colorado. This virus is antigenically related to western equine encephalitis virus and may represent a distinct member of this group.
Area of Science:
- Virology
- Arbovirology
- Public Health
Background:
- Alphaviruses are a genus of viruses transmitted by arthropods, some of which can cause significant disease in humans and animals.
- The western equine encephalitis (WEE) virus complex includes several important arboviruses in North America.
Purpose of the Study:
- To characterize a newly isolated alphavirus from avian hosts and insect vectors in eastern Colorado.
- To determine the antigenic relationships and taxonomic position of this novel virus within the WEE virus complex.
Main Methods:
- Isolation and characterization of the virus, including its sensitivity to chemical and physical agents.
- Pathogenicity studies in suckling mice and other laboratory hosts.
- Serological assays such as hemagglutination-inhibition (HI), complement-fixation, and neutralization tests.
- Analysis of structural polypeptides and oligonucleotides.
Main Results:
- A novel alphavirus, named Fort Morgan (FM) virus, was isolated from Cliff Swallows, House Sparrows, and Oeciacus vicarius bugs.
- FM virus exhibited sensitivity to sodium deoxycholate and instability at low pH, but was not temperature-sensitive.
- Plaque-purified FM virus was pathogenic in laboratory hosts, unlike unpassaged strains.
- Serological tests revealed cross-reactions with WEE virus complex members, with closer relationships to eastern US strains (Highlands J virus).
Conclusions:
- FM virus is a distinct alphavirus belonging to the WEE antigenic complex.
- The findings necessitate a reconsideration of the taxonomy within the WEE complex.
- The epizoologic significance of FM virus warrants further investigation.