Construction And Identification Of Infectious Clone And Chimeric Clone Of Porcine Reproductive And Respiratory Syndrome Virus NADC30-like Strain ZJqz21

Porcine reproductive and respiratory syndrome(PRRS)is caused by PRRS virus(PRRSV).It is an important infectious disease that seriously harms the pig industry all over the world.In 2013,a new strain with high nucleotide homology with American NADC30 strain was isolated in China.This strain and NADC30 strain had a discontinuous deletion of111+1+19 amino acids(aa)in the Nsp2 protein coding region,so it was called NADC-like strain of PRRSV.At present,more and more studies have shown that NADC30-like strain is easy to recombine with other PRRSV strains,which leads to the enhanced virulence of the recombined strains.Especially,there are many cases of gene recombination between NADC30-like strains and PRRSV vaccine strains used in clinic,which has caused huge economic losses to the pig industry and made the effective prevention and control of PRRS more complicated and difficult.Therefore,it is necessary to conduct in-depth molecular biology and virulence analysis of NADC30-like strain.In this study,the full-length infectious clone of NADC30-like ZJqz21 strain was successfully constructed,and the live virus was successfully rescued.There was no significant difference in virological characteristics between rescued virus rZJqz21 and parental virus ZJqz21.Animal experiments shown that rZJqz21 retained similar pathogenicity and could produce typical clinical symptoms similar to those of the parental virus ZJqz21.In this study,the chimeric virus rHuN4-ZJqz21-ORF2-6 substituted with the ORF2-ORF6 sequence of ZJqz21 strain,using HP-PRRSV attenuated vaccine strain vHuN4-F112 as the backbone was successfully constructed and rescued.The chimeric virus was quite different from its parental virus in virus titer and viral protein expression.Taken together,the results of this study provide useful tools for further studying the biological characteristics and pathogenicity of NADC30-like strain,and also lay a solid foundation for constructing PRRSV chimeric vaccine.