RÉSUMÉ
Objective To construct a universal influenza mRNA vaccine and evaluate its immunogenicity.Methods The antigen sequence of hemagglutinin(HA),nucleoprotein(NP)and matrix protein 2 ectodomain(M2e)in influenza A/California/04/2009 was optimized.HA,NP and 3 tandem M2e(3M2e)were cloned into pcDNA3.1 vector,respectively.Then the mRNAs were synthesized by linearization,in vitro transcription,enzymatic capping and enzymatic tailing,and named as mRNA-HA,mRNA-NP and mRNA-3M2e,respectively.The protein expression of the 3 kinds of mRNAs in 293T cells was detected by immunofluorescence assay.Comb-mRNA vaccine was prepared by enveloped mRNA-HA,mRNA-NP and mRNA-3M2e with lipid nanoparticles,respectively,and the particle size and potential were identified.Twenty-eight 6-week-old female BALB/c mice(18~22 g)were randomly divided into LNP group(n=14)and Comb-mRNA group(n=14).Hemagglutination inhibition(HI)method and microneutralization(MN)test were used to evaluate the serum antibody titer induced by Comb-mRNA vaccines.The mice were infected by 5LD50 wild-type H1 N1 influenza virus to evaluate the protective efficacy.Results The mRNA-HA,mRNA-NP and mRNA-3M2e were successfully constructed,and the 3 mRNAs could be expressed in 293T cells.The average size of mRNA encapsulated by lipid nanoparticles was 119.53±6.5 nm,and the average potential was-8.23±1.3 mV.The geometric mean titer(GMT)of HI and MN in the Comb-mRNA group were 179.6 and 201.6,compared with the LNP group.The ratio of IFN-γ+CD4+/CD8+Tcells was increased.The Comb-mRNA group could provide protection against 5LD50 wild type influenza H1 N1 virus after 2 weeks of booster immunization.Conclusion Comb-mRNA,an influenza vaccine candidate,can induce immune responses and protect mice from influenza virus challenge.