title: Dissecting the Role of E2 Protein Domains in Alphavirus Pathogenicity.
abstract: Alphaviruses represent a diverse set of arboviruses, many of which are important pathogens. Chikungunya virus (CHIKV), an arthritis-inducing alphavirus, is the cause of a massive ongoing outbreak in the Caribbean and South America. In contrast to CHIKV, other related alphaviruses, such as Venezuelan equine encephalitis virus (VEEV) and Semliki Forest virus (SFV), can cause encephalitic disease. E2, the receptor binding protein, has been implicated as a determinant in cell tropism, host range, pathogenicity, and immunogenicity. Previous reports also have demonstrated that E2 contains residues important for host range expansions and monoclonal antibody binding; however, little is known about what role each protein domain (e.g., A, B, and C) of E2 plays on these factors. Therefore, we constructed chimeric cDNA clones between CHIKV and VEEV or SFV to probe the effect of each domain on pathogenicity in vitro and in vivo. CHIKV chimeras containing each of the domains of the E2 (ΔDomA, ΔDomB, and ΔDomC) from SFV, but not VEEV, were successfully rescued. Interestingly, while all chimeric viruses were attenuated compared to CHIKV in mice, ΔDomB virus showed similar rates of infection and dissemination in Aedes aegypti mosquitoes, suggesting differing roles for the E2 protein in different hosts. In contrast to CHIKV; ΔDomB, and to a lesser extent ΔDomA, caused neuron degeneration and demyelination in mice infected intracranially, suggesting a shift toward a phenotype similar to SFV. Thus, chimeric CHIKV/SFV provide insights on the role the alphavirus E2 protein plays on pathogenesis.
  
  
  OBJECTIVE
  Chikungunya virus (CHIKV) has caused large outbreaks of acute and chronic arthritis throughout Africa and Southeast Asia and has now become a massive public health threat in the Americas, causing an estimated 1.2 million human cases in just over a year. No approved vaccines or antivirals exist for human use against CHIKV or any other alphavirus. Despite the threat, little is known about the role the receptor binding protein (E2) plays on disease outcome in an infected host. To study this, our laboratory generated chimeric CHIKV containing corresponding regions of the Semliki Forest virus (SFV) E2 (domains A, B, and C) substituted into the CHIKV genome. Our results demonstrate that each domain of E2 likely plays a critical, but dissimilar role in the viral life cycle. Our experiments show that manipulation of E2 domains can be useful for studies on viral pathogenesis and potentially the production of vaccines and/or antivirals.
authors.affiliation: Department of Pathobiological Sciences, University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors.forename: James
authors.initials: J
authors.lastname: Weger-Lucarelli
authors.affiliation: Department of Pathobiological Sciences, University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Aliota
authors.affiliation: Department of Medicine, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors.forename: Nathan
authors.initials: N
authors.lastname: Wlodarchak
authors.affiliation: Department of Pathobiological Sciences, University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors.forename: Attapon
authors.initials: A
authors.lastname: Kamlangdee
authors.affiliation: Department of Pathobiological Sciences, University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors.forename: Ryan
authors.initials: R
authors.lastname: Swanson
authors.affiliation: Department of Pathobiological Sciences, University of Wisconsin-Madison, Madison, Wisconsin, USA osorio@svm.vetmed.wisc.edu.
authors.forename: Jorge E
authors.initials: JE
authors.lastname: Osorio
mesh_terms: D000330:Aedes / Q000821:virology; D018354:Alphavirus Infections / Q000473:pathology* / Q000821:virology; D000818:Animals; D001921:Brain / Q000473:pathology; D002646:Chikungunya virus / Q000235:genetics / Q000472:pathogenicity*; D004195:Disease Models, Animal; D004666:Encephalitis Virus, Venezuelan Equine / Q000235:genetics / Q000472:pathogenicity*; D005260:Female; D008297:Male; D008810:Mice, Inbred C57BL; D017434:Protein Structure, Tertiary; D012672:Semliki forest virus / Q000235:genetics / Q000472:pathogenicity*; D014759:Viral Envelope Proteins / Q000235:genetics / Q000378:metabolism*; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D014759:Viral Envelope Proteins; D037521:Virulence Factors