title: IRES-dependent replication of Venezuelan equine encephalitis virus makes it highly attenuated and incapable of replicating in mosquito cells.
abstract: The development of infectious cDNA for different alphaviruses opened an opportunity to explore their attenuation by extensively modifying the viral genomes, an approach that might minimize or exclude the reversion to the wild-type, pathogenic phenotype. Moreover, the genomes of such alphaviruses can be engineered to contain RNA elements that would be functional only in cells of vertebrate, but not insect, origin. In the present study, we developed a recombinant VEEV that is more attenuated than TC-83 and capable of replicating only in vertebrate cells. This phenotype was achieved by rendering the translation of the viral structural proteins, and ultimately viral replication, dependent on the internal ribosome entry site of encephalomyocarditis virus (EMCV IRES). This recombinant virus was viable, but required additional, adaptive mutations in nsP2 that strongly increased its replication rates. In spite of efficient replication in cultured vertebrate cells, the genetically modified VEEV demonstrated a highly attenuated phenotype in newborn mice, and yet induced protective immunity against VEEV infection.
authors.affiliation: Department of Microbiology and Immunology, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555-1019, USA.
authors.forename: Eugenia
authors.initials: E
authors.lastname: Volkova
authors.forename: Elena
authors.initials: E
authors.lastname: Frolova
authors.forename: Justin R
authors.initials: JR
authors.lastname: Darwin
authors.forename: Naomi L
authors.initials: NL
authors.lastname: Forrester
authors.forename: Scott C
authors.initials: SC
authors.lastname: Weaver
authors.forename: Ilya
authors.initials: I
authors.lastname: Frolov
mesh_terms: D000222:Adaptation, Physiological; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D006224:Cricetinae; D009033:Culicidae; D004666:Encephalitis Virus, Venezuelan Equine / Q000235:genetics* / Q000472:pathogenicity / Q000502:physiology*; D051379:Mice; D009154:Mutation; D041681:NIH 3T3 Cells; D010641:Phenotype; D012367:RNA, Viral / Q000235:genetics; D011995:Recombination, Genetic; D017361:Viral Nonstructural Proteins / Q000235:genetics; D014774:Virulence / Q000235:genetics; D014779:Virus Replication / Q000235:genetics
chemical_list: D012367:RNA, Viral; D017361:Viral Nonstructural Proteins