AUTHOR=Ou Xumin , Wang Mingshu , Mao Sai , Cao Jingyu , Cheng Anchun , Zhu Dekang , Chen Shun , Jia Renyong , Liu Mafeng , Yang Qiao , Wu Ying , Zhao Xinxin , Zhang Shaqiu , Liu Yunya , Yu Yanling , Zhang Ling , Chen Xiaoyue , Peppelenbosch Maikel P. , Pan Qiuwei 

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

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=8

YEAR=2018

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2018.00249

DOI=10.3389/fcimb.2018.00249

ISSN=2235-2988

ABSTRACT=<p>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 (<inline-formula><mml:math id="M1" 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></inline-formula>, <inline-formula><mml:math id="M2" 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></inline-formula>, 3C<sup>pro</sup>, and 3D<sup>pro</sup>) 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.</p>