The 40-91 aa sequence of porcine epidemic diarrhea virus ORF3 protein is the key structural domain controlling its location in cytoplasm / 生物工程学报

ORF3 protein, the single accessory protein encoded by porcine epidemic diarrhea virus (PEDV), is related to viral pathogenicity. In order to determine the cytoplasmic location signal of PEDV ORF3, we constructed a series of recombinant plasmids carrying full-length or truncated segments of PEDV DR13 ORF3 protein. When the acquired plasmids were transfected into Vero cells, expression and distribution of the EGFP-fused full-length ORF3 protein and its truncated forms in the cells were observed by laser confocal microscopy. The results showed that ORF3 protein or their truncated forms containing 40-91 aa segment including two transmembrane domains were localized in the cytoplasm, whereas ORF3 truncated peptides without the 40-91 aa segment were distributed in the whole cell (in both cytoplasm and nucleus). This suggests that the 40-91 aa is the key structural domain determining cytoplasmic location of PEDV ORF3 protein. The discovery provides reference for further clarifying intracellular transport and biological function of PEDV ORF3 protein.

Advances in reverse genetics to treat porcine epidemic diarrhea virus / 生物工程学报

Porcine epidemic diarrhea virus (PEDV) is one of the major etiologies responsible for the acute, highly contagious disease in the digestive tract of pigs, especially neonatal piglets. Since PEDV was first identified in Europe in the late 1970s, it has resulted in significant economic losses in many Asian swine-raising countries, including China. Recently, reverse genetics techniques including targeted RNA recombination, bacteria artificial chromosome system and in vitro ligation have been successfully used to manipulate the genome of PEDV, which providing new strategies for the clear delineation of the functions of the viral proteins, the mechanisms behind PEDV pathogenesis and the design of novel vaccines against PEDV. Here, we review the progresses of different reverse genetics platforms developed for PEDV and their applications, covering the roles of trypsin in PEDV propagation, functions of S and ORF3 protein and the development of next generation PED vaccines, and the perspectives of reverse genetics for PEDV.

Molecular epidemiological analysis of ORF3 genes of PEDV endemic strains in Henan province / 中国兽医学报

To understand the genetic origin and variation of porcine epidemic diarrhea virus (PEDV) prevailing in Henan province,a total of 22 PEDV positive samples from suckling piglets with severe diarrhea were collected from 16 pig farms and amplified by RT-PCR.ORF3 genes were then cloned into pMD18-T vector and sequenced.The result of sequencing showed that the length of ORF3 genes all were 675 bp which encoded 224 amino acids.The strains in this study had eight amino acid substitutions when compared with CV777 strain.The nucleotide homologies of the 22 strains were 95.9％-100％ and amino acid homologies were 96.4％-100％.By comparing with those of European strain CV777 and vaccine strain truncated CV777,the nucleotide homologies were 97.1％-97.9％ and 94.8％-95.4％,respectively.Based on the phylogenetic relationship of ORF3 genes,the PEDV field strains and PEDV reference strains could be divided into two groups,and all the field strains identified in this study belong to group 2.It suggested that prevalent PEDV strains in this study seem to be closely related to Henan isolates in previous years,domestic strains,Janpanese strains,American strains as well as Korean strains but differ genetically from European strains or vaccine strains used in China.This experiment analyzed the ORF3 gene sequence features in prevailing of Henan region in recent years,which provides a new support of epidemiology study and protein function research of PEDV ORF3 gene.

Genetic variation analysis of Nsp2, ORF5 and ORF3 of PRRSV SC-GY strain from Sichuan province / 中国兽医学报

To monitor genetic variation of porcine reproductive and respiratory syndrome virus (PRRSV),RT-PCR was used to identify a sample suspected of PRRSV infection.A PRRSV named SC-GY strain was obtained,and its Nsp2,ORF5 and ORF3 genes were used for sequence alignment and phylogenetic tree construction.The results showed that SC-GY strain is highly pathogenic PRRSV American variant strains with Nsp2 gene discontinuous deletion of 30 amino acids,ORF3 gene aa17 a serine (S) insert.Comparing to VR2332,CH-1a,JXA1,HUN4,NADC30,HENAN-XINX and SC2012,the Nsp2,ORF5 and ORF3 of SC-GY shared 70.3％-97.9％,82.4％-97.6％ and 83.1％-98.2％ of nucleotide similarity,and 62.3％-96.3％,78.0％-95.7％ and 81.6％-96.5％ of deduced amino acid similarity;and compared to LV they shared only 18.9％,60.8％ and 63.7％ of nucleotide similarity,and 14.0％,54.9％ and 57.2％ of deduced amino acid similarity.The phylogenetic tree revealed that the SC-GY formed independent small branches although it belonged to the same subgroup as highly pathogenic PRRSV strains.The results showed that in high frequency live vaccine immunization of currently PRRSV,the gene of PRRSV epidemic strain is still in constant variation.Vaccination of live PRRSV vaccines should be reduced and surveillance of PRRSV strains should be enhanced.

Study on Fap1 glycosylation and maturation regulating by ORF3 coded by fap1-orf4 gene locus of Streptococcus parasanguis / 中华微生物学和免疫学杂志

Objective To study whether ORF3 coded by fap1-orf4 gene locus of Streptococcus pa-rasanguis is involved in the regulation of Fap1 glycosylation and maturation and to investigate whether ORF3 influences Streptococcus parasanguis adhesion. Methods A gene replacement strategy was adapted to con-struct orf3 alleic replace mutant of Streptococcus parasanguis. Complementation assay and Western blot were used to test Fap1 expression levels. Whole saliva-coated hydroxyapatite (SHA) adhesion assay was adapted to determine Streptococcus parasanguis adhension. Results (1) Non-polar was found in strain VT1774, the orf3 alleic replace mutant of Streptococcus parasanguis. (2) Western blot showed that mature Fapl (Mr about 220 × 103) disappeared and were substituted with high molecular weight Fapl (Mr about 470 × 103) in strain VT1774, furthermore, complementation assay showed VT1775, the complementation strain of VT1774, re-stored mature Fapl expression. (3) The binding ability reduced significantly in strain VT1774. Conclusion ORF3 coded byfapl-orf4 gone locus was required for Fap1 glycosylation and maturation in Streptococcus pa-rasanguis, orf3 alleic replacment resulted in Fap1 glycosylation and mature disorder and decreasing of adhen-sion ability of Streptococcus parasanguis.