Comparison of Pathogenicity-Related Genes in the Current Pseudorabies Virus Outbreak in China

Xue-Hui Cai,Zhi-Jun Tian,Yan-Dong Tang,Ming-Xia Sun,Ji-Ting Liu,Tong-Yun Wang

doi:10.1038/s41598-017-08269-3

Abstract

There is currently a pandemic of pseudorabies virus (PRV) variant strains in China. Despite extensive research on PRV variant strains in the past two years, few studies have investigated PRV pathogenicity-related genes. To determine which gene(s) is/are linked to PRV virulence, ten putative virulence genes were knocked out using clustered regularly interspaced palindromic repeats (CRISPR)/Cas9 technology. The pathogenicity of these mutants was evaluated in a mouse model. Our results demonstrated that of the ten tested genes, the thymidine kinase (TK) and glycoprotein M (gM) knockout mutants displayed significantly reduced virulence. However, mutants of other putative virulence genes, such as glycoprotein E (gE), glycoprotein I (gI), Us2, Us9, Us3, glycoprotein G (gG), glycoprotein N (gN) and early protein 0 (EP0), did not exhibit significantly reduced virulence compared to that of the wild-type PRV. To our knowledge, this study is the first to compare virulence genes from the current pandemic PRV variant strain. This study will provide a valuable reference for scientists to design effective live attenuated vaccines in the future.

Highlights

There is currently a pandemic of pseudorabies virus (PRV) variant strains in China
We used the most effective single-guide RNA (sgRNA) to knock out the corresponding gene
For the thymidine kinase (TK) knockout, it was previously reported that acyclovir could inhibit PRV containing an intact TK gene

Summary

Introduction

There is currently a pandemic of pseudorabies virus (PRV) variant strains in China. Despite extensive research on PRV variant strains in the past two years, few studies have investigated PRV pathogenicityrelated genes. To determine which gene(s) is/are linked to PRV virulence, ten putative virulence genes were knocked out using clustered regularly interspaced palindromic repeats (CRISPR)/Cas[9] technology The pathogenicity of these mutants was evaluated in a mouse model. Despite great efforts to promote PRV vaccination, an unprecedented large-scale outbreak of PRV variants in China has caused great economic losses to the Chinese swine industry[2, 3]. These re-emerging pseudorabies variants belong to genotype II, and their sequences exhibit significant differences from genotype I4, 5. This study uncovered pathogenicity-related genes of re-emerging PRV variants for the first time and will provide a valuable reference for the control of PRV variants

Methods

Results

Conclusion