Isolation,Identification And Genomic Characterization Analysis Of The Epidemic Strain Of Porcine Reproductive And Respiratory Syndrome Virus

Porcine Reproductive and Respiratory Syndrome(PRRS),an acute infectious disease caused by Porcine Reproductive and Respiratory Syndrome Virus(PRRSV),primarily causes impaired reproductive function in sows,piglet mortality and respiratory disease in finishing pigs.PRRS has always been an important viral infectious disease that seriously threatens the swine industry.Because the virus is prone to mutation and recombination,it is becoming increasingly difficult to prevent and control.To understand the current prevalence of PRRS,this study first tested 315 clinical samples from diseased pigs collected from 2021 to 2023.The test results showed that101 of them were positive for PRRSV,and some of the positive samples were selected for PCR amplification of their Nsp2,Nsp9 and ORF5 genes,and the genetic evolution analysis of their corresponding gene sequences showed that the strains obtained in this study belonged to different lineages of PRRSV.Ten Nsp2 genes,14 Nsp9 genes and 14ORF5 genes were mainly distributed in lineage 1,lineage 5 and lineage 8.To further understand the characteristics of the strains,this study used Macr-145 cells to isolate the strains of some positive samples,and the results showed that 3 strains of viruses were successfully obtained.At the same time,the three PRRSV isolates were named ZJ6/2021,YN3/2022 and SH1/2022,respectively.The results of IFA identification showed that all three viruses could be recognized by monoclonal antibodies against PRRSV N protein,YN3/2022 and SH1/2022 could be recognized by monoclonal antibodies against PRRSV Nsp2 protein,but ZJ6/2021 could not be recognized by antiNsp2 protein monoclonal antibodies.Anti-recognition.Whole-genome sequencing of the three isolated strains showed that the full-length genomes of ZJ6/2021,YN3/2022 and SH1/2022 strains were 15221 bp,15278bp and 15317bp(excluding poly A),respectively.The results of genetic evolution analysis of the full-length gene sequence showed that the ZJ6/2021 strain was in the same branch as lineage 1 and belonged to the MADC30-like strain,and the YN3/2022 and SH1/2022 strains were similar to the HP-PRRSV and CH-1a-like strains of lineage 8.The strains belong to the same clade.The results of recombination analysis showed that the strain ZJhz6/2021 did not undergo recombination,and the strain YN3/2022 was produced by the recombination of the HP-PRRSV-like strain and the CH-1a-like strain within the lineage,and there were 2 recombination breakpoints(nt4903,nt8816)located in the Nsp3 region and Nsp9 region,respectively;the SH1/2022 isolate is a strain produced by recombination between HP-PRRSV-like strains and VR2332-like strains.There are two recombination breakpoints(nt9460,nt11398)in the SH1/2022 genome,located in the Nsp9 and Nsp11 regions,respectively.The genomic characteristics of the above isolated strains are complex and diverse,suggesting that we need to continuously monitor the prevalence dynamics of PRRSV in pig farms.This study analyzed the genetic variation characteristics of PRRSV epidemic strains in some areas of my country in recent years,and isolated two recombinant PRRSV strains with different recombination patterns.The research results will help to understand in depth the genetic variation of PRRSV epidemic strains in my country,which will provide a scientific basis for preventing and controlling the spread of new PRRS mutant strains in the future.