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A novel attenuated enterovirus A71 mutant with VP1-V238A,K244R exhibits reduced efficiency of cell entry/exit and augmented binding affinity to sulfated glycans.

ABSTRACT: Enterovirus A71 (EV-A71) is one of the major etiological agents of hand, foot, and mouth disease, and its infection occasionally leads to fatal neurological complications in children. However, only inactivated whole virus vaccines against EV-A71 are commercially available in Mainland China. Furthermore, the mechanisms underlying the infectivity and pathogenesis of EV-A71 remain to be better understood. By adaptation of an EV-A71 B5 strain in monkey Vero cells in the presence of brilliant black BN (E151), an anti-EV-A71 agent, a double mutant with VP1-V238A,K244R emerged to be E151 enhanced infection. The growth of reverse genetics (RG) mutant RG/B5-VP1-V238A,K244R (RG/B5-AR) was promoted by E151 in Vero cells, but inhibited in other human and murine cells; while its parental wild type RG/B5-wt was strongly prevented by E151 from infection in all tested cells. In the absence of E151, RG/B5-AR exhibited defective cell entry/exit, resulting in reduced viral transmission and growth in vitro. It had augmented binding affinity to sulfated glycans, cells and tissue/organs, which probably functioned as decoys to restrict viral dissemination and infection. RG/B5-AR was also attenuated with 355 times higher 50% lethal dose and shorter timing of virus clearance than RG/B5-wt in suckling AG129 mice. It, however, remained highly immunogenic in adult AG129 mice to protect their suckling mice from lethal EV-A71 challenges through maternal neutralizing antibodies. Overall, discovery of the attenuated mutant RG/B5-AR contributes to better understanding of virulence determinants of EV-A71 and further development of novel vaccines against EV-A71. Importance Enterovirus A71 (EV-A71) is highly contagious in children and has been responsible for thousands of deaths in Asia-Pacific region since 1990s. Unfortunately, the virulence determinants and pathogenesis of EV-A71 are not fully clear. We discovered that a novel EV-A71 mutant VP1-V238A,K244R showed growth attenuation with reduced efficiency of cell entry/exit. In Vero cell line which has been approved for manufacturing EV-A71 vaccines, the growth defects of the mutant were compensated by a food dye brilliant black BN. The mutant was also with augmented binding affinity to sulfated glycans and other cellular components which probably restricted the viral infection and dissemination. Therefore, it was virulence attenuated in a mouse model but still retained its immunogenicity. Our findings suggest the mutant as a promising vaccine candidate against EV-A71 infection.

SUBMITTER: Meng T

PROVIDER: S-EPMC8549518 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Enterovirus A71 (EV-A71) is a major pathogen that causes hand-foot-and-mouth disease (HFMD), which occasionally results in severe neurological complications. In this study, we developed four EV-A71 (rgEV-A71) strains by reverse genetics procedures as possible vaccine candidates. The four rgEV-A71 viruses contained various codon-deoptimized VP1 capsid proteins (VP1-CD) and showed replication rates and antigenicity similar to that of the wild-type virus, while a fifth virus, rg4643C4VP-CD, was unable to form plaques but was still able to be examined by median tissue culture infectious dose (TCID50) titers, which were similar to those of the others, indicating the effect of CD on plaque formation. However, the genome stability showed that there were some mutations which appeared during just one passage of the VP1-CD viruses. Thus, we further constructed VP1-CD rgEV-A71 containing high-fidelity determinants in 3D polymerase (CD-HF), and the number of mutations in CD-HF rgEV-A71 was shown to have decreased. The CD-HF viruses showed less virulence than the parental strain in a mouse infection model. After 14 days postimmunization, antibody titers had increased in mice infected with CD-HF viruses. The mouse antisera showed similar neutralizing antibody titers against various CD-HF viruses and different genotypes of EV-A71. The study demonstrates the proof of concept that VP1 codon deoptimization combined with high-fidelity 3D polymerase decreased EV-A71 mutations and virulence in mice but retained their antigenicity, indicating it is a good candidate for next-generation EV-A71 vaccine development.IMPORTANCE EV-A71 can cause severe neurological diseases with fatality in infants and young children, but there are still no effective drugs to date. Here, we developed a novel vaccine strategy with the combination of CD and HF substitutions to generate the genetically stable reverse genetics virus. We found that CD combined with HF polymerase decreased the virulence but maintained the antigenicity of the virus. This work demonstrated the simultaneous introduction of CD genome sequences and HF substitutions as a potential new strategy to develop attenuated vaccine seed virus. Our work provides insight into the development of a low-virulence candidate vaccine virus through a series of genetic editing of virus sequences while maintaining its antigenicity and genome stability, which will provide an additional strategy for next-generation vaccine development of EV-A71.

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A novel attenuated enterovirus A71 mutant with VP1-V238A,K244R exhibits reduced efficiency of cell entry/exit and augmented binding affinity to sulfated glycans.

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