title: IRES-driven expression of the capsid protein of the Venezuelan equine encephalitis virus TC-83 vaccine strain increases its attenuation and safety.
abstract: The live-attenuated TC-83 strain is the only licensed veterinary vaccine available to protect equids against Venezuelan equine encephalitis virus (VEEV) and to protect humans indirectly by preventing equine amplification. However, TC-83 is reactogenic due to its reliance on only two attenuating point mutations and has infected mosquitoes following equine vaccination. To increase its stability and safety, a recombinant TC-83 was previously engineered by placing the expression of the viral structural proteins under the control of the Internal Ribosome Entry Site (IRES) of encephalomyocarditis virus (EMCV), which drives translation inefficiently in insect cells. However, this vaccine candidate was poorly immunogenic. Here we describe a second generation of the recombinant TC-83 in which the subgenomic promoter is maintained and only the capsid protein gene is translated from the IRES. This VEEV/IRES/C vaccine candidate did not infect mosquitoes, was stable in its attenuation phenotype after serial murine passages, and was more attenuated in newborn mice but still as protective as TC-83 against VEEV challenge. Thus, by using the IRES to modulate TC-83 capsid protein expression, we generated a vaccine candidate that combines efficient immunogenicity and efficacy with lower virulence and a reduced potential for spread in nature.
authors.affiliation: Institute for Human Infections and Immunity, Sealy Center for Vaccine Development, and Department of Pathology, University of Texas Medical Branch, Galveston, Texas, United States of America.
authors.forename: Mathilde
authors.initials: M
authors.lastname: Guerbois
authors.forename: Eugenia
authors.initials: E
authors.lastname: Volkova
authors.forename: Naomi L
authors.initials: NL
authors.lastname: Forrester
authors.forename: Shannan L
authors.initials: SL
authors.lastname: Rossi
authors.forename: Ilya
authors.initials: I
authors.lastname: Frolov
authors.forename: Scott C
authors.initials: SC
authors.lastname: Weaver
mesh_terms: D000330:Aedes; D000818:Animals; D036022:Capsid Proteins / Q000096:biosynthesis* / Q000235:genetics; D002460:Cell Line; D002522:Chlorocebus aethiops; D004195:Disease Models, Animal; D004666:Encephalitis Virus, Venezuelan Equine / Q000235:genetics / Q000276:immunology* / Q000472:pathogenicity; D004685:Encephalomyelitis, Venezuelan Equine / Q000276:immunology / Q000517:prevention & control; D015870:Gene Expression; D042822:Genomic Instability; D006801:Humans; D051379:Mice; D014176:Protein Biosynthesis; D016019:Survival Analysis; D014613:Vaccines, Attenuated / Q000008:administration & dosage / Q000009:adverse effects / Q000235:genetics / Q000276:immunology; D014614:Vaccines, Synthetic / Q000008:administration & dosage / Q000009:adverse effects / Q000235:genetics / Q000276:immunology; D014765:Viral Vaccines / Q000008:administration & dosage / Q000009:adverse effects* / Q000235:genetics / Q000276:immunology*
chemical_list: D036022:Capsid Proteins; D014613:Vaccines, Attenuated; D014614:Vaccines, Synthetic; D014765:Viral Vaccines