Identification of B-cell epitopes in the NSP1 protein of porcine reproductive and respiratory syndrome virus

Porcine reproductive and respiratory syndrome virus (PRRSV) was divided into North American and European genotypes. NSP1 was an important non-structural protein of PRRSV, which was auto-cleaved from the replicase polyprotein into NSP1 alpha and NSP1 beta subunits and played an important role in the immune suppression. In this study, six monoclonal antibodies (MAbs) against the recombinant PRRSV NSP1, expressed in Escherichia coli system, were screened out and identified. Western blot and IFA results indicated that 4 out of 6 MAbs recognized the recombinant NSP1 alpha and 2 MAbs recognized NSP1 beta. Epitope mapping results indicated that MAb 4H2 recognized the linear epitopes E(54)EPLRW(59) in NSP1 alpha, MAbs (2G5, 3E11 and 4D4) recognized the epitopes H(157)VLTNLP(163) in NSP1 alpha, and MAbs 3C7 and 1H7 reacted with the epitopes 185aa to 232aa in NSP1 beta. Protein sequence alignment of NSP1 indicated E(54)EPLRW(59) was conserved in all North American PRRSV strains, whereas European type strains has variable amino acids in this region. The epitope H(157)VLTNLP(163) was relatively conserved among all PRRSV strains, except for a L162 -> S162 change in European type strains. The epitope 185-232aa was variable among North American PRRSV strains. These results may facilitate future investigations into the function of NSP1 of PRRSV and diagnostic methods for PRRSV infection. (C) 2011 Elsevier B.V. All rights reserved.