猪急性腹泻综合征冠状病毒核衣壳蛋白新型线性B细胞表位的鉴定OA北大核心

Swine acute diarrhea syndrome coronavirus(SADS-CoV)was a new bat-origin swine enteric coronavirus that can cause diarrhea,vomiting,dehydration and death in newborn piglets.Nucleocapsid(N)protein is the most conserved structure protein,and has a good antigenicity.In the previous study,five monoclonal antibodies(mAbs,1C10,4B10,6G1,6F3 and 6E8,respec-tively)against the SADS-CoV N protein were obtained,among which 6E8 showed the strongest reactivity with SADS-CoV.In this study,truncated and deletion mutant plasmids of N protein were constructed using pET32a expression vector.The 6E8 epitope was located to amino acids 69-QKGQRK-74 by testing the 6E8 for reactivity with series of N truncation and deletion using Western blot.The 6E8 epitope was highly conserved among different SADS-CoV isolated strains and bat coronavirus HKU2.A similar epitope(VKGQRK)was found in porcine transmissible gastroenteritis virus(TGEV)and feline infectious peritonitis virus(FIPV),with one amino acid difference;however,it showed low homology with other coronaviruses.Specific tests showed that the 6E8 could not be reacted with porcine epidemic diarrhea virus(PEDV)and TGEV,de-spite only one amino acid different in the epitope recognized by 6E8 and TGEV,indicating that 69-Q was the key amino acid for 6E8 epitope.Further experiments showed that the 6E8 had a ca-pacity to enhance the infection of SADS-CoV in Huh7 cells when the 6E8 incubated with SADS-CoV before infection,which was called antibody-dependent enhancement(ADE).In summary,the identification of the novel B-cell epitope in the SADS-CoV N protein provides new insights for designing novel SADS-CoV vaccines and developing epitope-related diagnostic reagents.