title: Rational design of a flavivirus vaccine by abolishing viral RNA 2'-O methylation.
abstract: Viruses that replicate in the cytoplasm cannot access the host nuclear capping machinery. These viruses have evolved viral methyltransferase(s) to methylate N-7 and 2'-O cap of their RNA; alternatively, they "snatch" host mRNA cap to form the 5' end of viral RNA. The function of 2'-O methylation of viral RNA cap is to mimic cellular mRNA and to evade host innate immune restriction. A cytoplasmic virus defective in 2'-O methylation is replicative, but its viral RNA lacks 2'-O methylation and is recognized and eliminated by the host immune response. Such a mutant virus could be rationally designed as a live attenuated vaccine. Here, we use Japanese encephalitis virus (JEV), an important mosquito-borne flavivirus, to prove this novel vaccine concept. We show that JEV methyltransferase is responsible for both N-7 and 2'-O cap methylations as well as evasion of host innate immune response. Recombinant virus completely defective in 2'-O methylation was stable in cell culture after being passaged for >30 days. The mutant virus was attenuated in mice, elicited robust humoral and cellular immune responses, and retained the engineered mutation in vivo. A single dose of immunization induced full protection against lethal challenge with JEV strains in mice. Mechanistically, the attenuation phenotype was attributed to the enhanced sensitivity of the mutant virus to the antiviral effects of interferon and IFIT proteins. Collectively, the results demonstrate the feasibility of using 2'-O methylation-defective virus as a vaccine approach; this vaccine approach should be applicable to other flaviviruses and nonflaviviruses that encode their own viral 2'-O methyltransferases.
authors.affiliation: Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, China.
authors.forename: Shi-Hua
authors.initials: SH
authors.lastname: Li
authors.forename: Hongping
authors.initials: H
authors.lastname: Dong
authors.forename: Xiao-Feng
authors.initials: XF
authors.lastname: Li
authors.forename: Xuping
authors.initials: X
authors.lastname: Xie
authors.forename: Hui
authors.initials: H
authors.lastname: Zhao
authors.forename: Yong-Qiang
authors.initials: YQ
authors.lastname: Deng
authors.forename: Xiao-Yu
authors.initials: XY
authors.lastname: Wang
authors.forename: Qing
authors.initials: Q
authors.lastname: Ye
authors.forename: Shun-Ya
authors.initials: SY
authors.lastname: Zhu
authors.forename: Hong-Jiang
authors.initials: HJ
authors.lastname: Wang
authors.forename: Bo
authors.initials: B
authors.lastname: Zhang
authors.forename: Qi-Bin
authors.initials: QB
authors.lastname: Leng
authors.forename: Roland
authors.initials: R
authors.lastname: Zuest
authors.forename: E-De
authors.initials: ED
authors.lastname: Qin
authors.forename: Cheng-Feng
authors.initials: CF
authors.lastname: Qin
authors.forename: Pei-Yong
authors.initials: PY
authors.lastname: Shi
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D004195:Disease Models, Animal; D004664:Encephalitis Virus, Japanese / Q000201:enzymology* / Q000235:genetics* / Q000472:pathogenicity; D004672:Encephalitis, Japanese / Q000473:pathology / Q000517:prevention & control* / Q000821:virology; D005260:Female; D022321:Japanese Encephalitis Vaccines / Q000008:administration & dosage / Q000235:genetics* / Q000276:immunology*; D007963:Leukocytes, Mononuclear / Q000276:immunology; D008745:Methylation; D051379:Mice; D008807:Mice, Inbred BALB C; D012367:RNA, Viral / Q000378:metabolism*; D016019:Survival Analysis; D014613:Vaccines, Attenuated / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology; D012359:tRNA Methyltransferases / Q000172:deficiency*
chemical_list: D000914:Antibodies, Viral; D022321:Japanese Encephalitis Vaccines; D012367:RNA, Viral; D014613:Vaccines, Attenuated; D012359:tRNA Methyltransferases