title: Molecular determinants of mouse neurovirulence and mosquito infection for Western equine encephalitis virus.
abstract: Western equine encephalitis virus (WEEV) is a naturally occurring recombinant virus derived from ancestral Sindbis and Eastern equine encephalitis viruses. We previously showed that infection by WEEV isolates McMillan (McM) and IMP-181 (IMP) results in high (∼90-100%) and low (0%) mortality, respectively, in outbred CD-1 mice when virus is delivered by either subcutaneous or aerosol routes. However, relatively little is known about specific virulence determinants of WEEV. We previously observed that IMP infected Culex tarsalis mosquitoes at a high rate (app. 80%) following ingestion of an infected bloodmeal but these mosquitoes were infected by McM at a much lower rate (10%). To understand the viral role in these phenotypic differences, we characterized the pathogenic phenotypes of McM/IMP chimeras. Chimeras encoding the E2 of McM on an IMP backbone (or the reciprocal) had the most significant effect on infection phenotypes in mice or mosquitoes. Furthermore, exchanging the arginine, present on IMP E2 glycoprotein at position 214, for the glutamine present at the same position on McM, ablated mouse mortality. Curiously, the reciprocal exchange did not confer mouse virulence to the IMP virus. Mosquito infectivity was also determined and significantly, one of the important loci was the same as the mouse virulence determinant identified above. Replacing either IMP E2 amino acid 181 or 214 with the corresponding McM amino acid lowered mosquito infection rates to McM-like levels. As with the mouse neurovirulence, reciprocal exchange of amino acids did not confer mosquito infectivity. The identification of WEEV E2 amino acid 214 as necessary for both IMP mosquito infectivity and McM mouse virulence indicates that they are mutually exclusive phenotypes and suggests an explanation for the lack of human or equine WEE cases even in the presence of active transmission.
authors.affiliation: Arthropod-borne and Infectious Diseases Laboratory, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, United States of America.
authors.forename: Eric C
authors.initials: EC
authors.lastname: Mossel
authors.forename: Jeremy P
authors.initials: JP
authors.lastname: Ledermann
authors.forename: Aaron T
authors.initials: AT
authors.lastname: Phillips
authors.forename: Erin M
authors.initials: EM
authors.lastname: Borland
authors.forename: Ann M
authors.initials: AM
authors.lastname: Powers
authors.forename: Ken E
authors.initials: KE
authors.lastname: Olson
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D002645:Chickens / Q000821:virology; D003465:Culex / Q000821:virology*; D004667:Encephalitis Virus, Western Equine / Q000235:genetics* / Q000254:growth & development / Q000472:pathogenicity*; D020241:Encephalomyelitis, Western Equine / Q000235:genetics / Q000821:virology*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009420:Nervous System / Q000473:pathology* / Q000821:virology*; D017354:Point Mutation / Q000235:genetics; D016415:Sequence Alignment; D040521:Subcutaneous Tissue / Q000821:virology; D014766:Viremia; D014774:Virulence / Q000235:genetics
chemical_list: D000596:Amino Acids
references.citation: J Virol. 1993 Sep;67(9):5117-25
references.pmid: 7688818
references.citation: Proc Natl Acad Sci U S A. 2004 Aug 3;101(31):11344-9
references.pmid: 15277679
references.citation: PLoS One. 2009 Aug 31;4(8):e6835
references.pmid: 19718263
references.citation: Vector Borne Zoonotic Dis. 2011 Mar;11(3):269-75
references.pmid: 21395409
references.citation: J Virol. 2008 Mar;82(6):2966-74
references.pmid: 18160430
references.citation: J Gen Virol. 2007 May;88(Pt 5):1545-1554
references.pmid: 17412985
references.citation: Nature. 2010 Dec 2;468(7324):705-8
references.pmid: 21124457
references.citation: J Virol. 1991 Sep;65(9):4654-64
references.pmid: 1714515
references.citation: EMBO J. 2011 Aug 09;30(18):3854-63
references.pmid: 21829169
references.citation: J Virol. 2005 Aug;79(16):10420-8
references.pmid: 16051834
references.citation: Virology. 2008 Oct 25;380(2):170-2
references.pmid: 18801549
references.citation: Am J Trop Med Hyg. 1997 Aug;57(2):240-4
references.pmid: 9288823
references.citation: PLoS Pathog. 2011 Dec;7(12):e1002412
references.pmid: 22174678
references.citation: Structure. 2006 Jan;14(1):63-73
references.pmid: 16407066
references.citation: J Gen Virol. 2006 Aug;87(Pt 8):2353-2361
references.pmid: 16847131
references.citation: J Virol. 1988 Jul;62(7):2329-36
references.pmid: 2836615
references.citation: J Med Entomol. 2001 May;38(3):393-9
references.pmid: 11372964
references.citation: J Virol. 2010 Oct;84(19):10004-15
references.pmid: 20668087
references.citation: Am J Trop Med Hyg. 2008 Apr;78(4):681-6
references.pmid: 18385369
references.citation: Science. 1931 Aug 28;74(1913):227-8
references.pmid: 17834966
references.citation: Nature. 2010 Dec 2;468(7324):709-12
references.pmid: 21124458
references.citation: J Gen Virol. 2009 Aug;90(Pt 8):1848-1858
references.pmid: 19403754
references.citation: Virology. 2011 Feb 5;410(1):216-27
references.pmid: 21131014
references.citation: PLoS Negl Trop Dis. 2013;7(1):e1931
references.pmid: 23359824
references.citation: J Virol. 2002 Jun;76(12):6302-10
references.pmid: 12021363
references.citation: Am J Trop Med Hyg. 1993 Sep;49(3):322-8
references.pmid: 8103970
references.citation: J Gen Virol. 1991 Oct;72 ( Pt 10):2431-5
references.pmid: 1919525