Isolation And Identification Of A Multilineage Recombinant PRRSV And Analysis Of Its Genomic Characteristics And Pathogenicity

Porcine reproductive and respiratory syndrome(PRRS),caused by porcine reproductive and respiratory syndrome virus(PRRSV),has caused huge economic losses to the global pig industry.The PRRSV was first reported in 1980,and was discovered in Europe in 1991 and the United States in 1992.Currently,the PRRSV is still circulating worldwide.Around 2006,Highly Pathogenic Porcine reproductive and respiratory syndrome virus(HP-PRRSV)emerged in China,which was characterized by the loss of 30 amino acids in the NSP2 region of the genome.Around 2013,a novel NADC30-like PRRSV with 131 Amino acids missing from the NSP2 region of the genome appeared in China.The variation of NADC30-like PRRSV is high and it is easy to be recombined with other PRRSV strains.The recombined PRRSV can occur between or within the pedigree of PRRSV.The homology of NADC30-like PRRSV with other strains of PRRSV is low.The recombination of PRRSV significantly increases the complexity of genome,immunogenicity and pathogenicity of PRRSV,and also brings more challenges to the prevention and control of PRRSV.At present,the NADC30-like PRRSV has become the dominant PRRSV in China,but the research on its genomic characteristics and pathogenicity is still insufficient.In this study,a new PRRSV strain named HN-YL1711 was isolated from a pig farm with severe respiratory symptoms in Henan Province.Genomic analysis showed that the full genome length of HN-YL1711 was 15018 nt,and its homology with VR2332,Ch1 a,JXA1,NADC30,QYYZ and GM2 was 86%,87.3%,88.1%,91.1%,84.2% and 84.1%,respectively.Analysis of amino acid deletion patterns in NSP2 region showed that HN-YL1711 had a characteristic deletion of 131 amino acids similar to NADC30.Evolutionary analysis based on NSP2,ORF5 and whole genome also indicated that HN-YL1711 belongs to the NADC30-like PRRSV.However,further recombination analysis revealed that HN-YL1711 was a recombinant strain of PRRSV derived from multiple recombination of NADC30-like(parent,pedigree 1),JXA1-like(parent,pedigree 8)and QYYZ-like(parent,pedigree 3),seven recombination breakpoints detected in genome.Cell tests showed that HN-YL1711 could infect PAMs,but not MARC-145 cells.To further explore the pathogenicity of HNYL1711,animal regression tests were conducted with HP-PRRSV JXA1 and CA-PRRSV CH1 a as control.The results showed that all PRRSV strains could induce fever,viremia,daily weight gain and lung injury in piglets.The incidence of HN-YL1711 group was less than JXA1 group,but more serious than CH1 a group.This study shows that the recombinant NADC30-like PRRSV is still a key driving force in the evolution of PRRSV,and is also a severe challenge to PRRSV prevention and control.This study provides a new theoretical basis and data support for in-depth analysis of the genetic variation mechanism and evolutionary relationship of PRRSV strains.