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Front Cell Infect Microbiol. 2018 Jul 18;8:249. doi: 10.3389/fcimb.2018.00249. eCollection 2018.

Incompatible Translation Drives a Convergent Evolution and Viral Attenuation During the Development of Live Attenuated Vaccine.

Ou X1,2,3, Wang M1,2,4, Mao S1,2, Cao J1,2, Cheng A1,2,4, Zhu D2,4, Chen S1,2,4, Jia R1,2,4, Liu M1,2,4, Yang Q1,2,4, Wu Y1,2,4, Zhao X1,2,4, Zhang S1,2,4, Liu Y1,2,4, Yu Y1,2,4, Zhang L1,2,4, Chen X2,4, Peppelenbosch MP3, Pan Q3.

Author information

1
Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.
2
Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu, China.
3
Department of Gastroenterology and Hepatology, Erasmus MC-University Medical Center, Rotterdam, Netherlands.
4
Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.

Abstract

Live attenuated vaccines are widely used to protect humans or animals from pathogen infections. We have previously developed a chicken embryo-attenuated Duck Hepatitis A Virus genotype 1 (DHAV-1) vaccine (CH60 strain). This study aims to understand the mechanisms that drive a virulent strain to an attenuated virus. Here, we systematically compared five DHAV-1 chicken embryo attenuated strains and 68 virulent strains. Phylogenetic analysis indicated that duck virulent strains isolated from different geographic regions of China undergo a convergent evolution in the chicken embryos. Comparative analysis indicated that the codon usage bias of the attenuated strains were shaped by chicken codons usage bias, which essentially contributed to viral adaption in the unsuitable host driven by incompatible translation. Of note, the missense mutations in coding region and mutations in untranslated regions may also contribute to viral attenuation of DHAV-1 to some extent. Importantly, we have experimentally confirmed that the expression levels of four viral proteins ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mrow><mml:msub><mml:mrow><mml:mtext>2A</mml:mtext></mml:mrow><mml:mn>3</mml:mn></mml:msub></mml:mrow><mml:mrow><mml:mtext>pro</mml:mtext></mml:mrow></mml:msup></mml:mrow></mml:math> , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mrow><mml:msub><mml:mrow><mml:mtext>2A</mml:mtext></mml:mrow><mml:mn>3</mml:mn></mml:msub></mml:mrow><mml:mrow><mml:mtext>pro</mml:mtext></mml:mrow></mml:msup></mml:mrow></mml:math> , 3Cpro, and 3Dpro) in the liver and kidney of ducks infected with an attenuated strain are significantly lower than that infected with a virulent strain, despite with similar virus load. Thus, the key mechanisms of viral attenuation revealed by this study may lead to innovative and easy approaches in designing live attenuated vaccines.

KEYWORDS:

Duck hepatitis A virus; RSCU; attenuation; tRNA; translational selection; vaccine

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