An improved indirect ELISA for specific detection of antibodiesagainst classical swine fever virus based on structurally designed E2protein expressed in suspension mammalian cells

Abstract

AbstractClassical swine fever (CSF), which is caused by classical swine fever virus (CSFV), is a highly contagious disease of pigs.CSFV is genetically and serologically related to bovine viral diarrhea virus (BVDV), a ruminant pestivirus. However, currentlyavailable ELISAs based on the full-length E2 protein of CSFV cannot discriminate anti-CSFV from anti-BVDVantibodies. In this study, a truncated CSFV E2 protein (amino acids 690 to 879) covering antigenic domains B/C/D/A(E2B/C/D/A) was designed based on homologous modeling according to the crystal structure of the BVDV E2 protein. TheE2B/C/D/A protein was expressed in CHO cells adapted to serum-free suspension culture, and an indirect ELISA (iELISA)was established based on the recombinant protein. No serological cross-reaction was observed for anti-BVDV sera in theiELISA. When testing 282 swine serum samples, the iELISA displayed a high sensitivity (119/127, 93.7%) and specificity(143/155, 92.3%), with an agreement of 92.9% (262/282) and 92.2% (260/282) with virus neutralization test and the IDEXXCSFV blocking ELISA, respectively. Taken together, the newly developed iELISA is highly specific and sensitive and ableto differentiate anti-CSFV from anti-BVDV antibodies