Identification of an epitope of SARS-coronavirus nucleocapsid protein

Abstract

The nucleocapsid (N) protein of severe acute respiratory syndrome-coronavirus (SARS-CoV) is a major virion structural protein. In this study, two epitopes (N1 and N2) of the N protein of SARS-CoV were predicted by bioinformatics analysis. After immunization with two peptides, the peptides-specific antibodies were isolated from the immunized rabbits. The further experiments demonstrated that N1 peptide-induced polyclonal antibodies had a high affinity to bind to E. coli expressed N protein of SARS-CoV. Furthermore, it was confirmed that N1 peptide-specific IgG antibodies were detectable in the sera of severe acute respiratory syndrome (SARS) patients. The results indicated that an epitope of the N protein has been identified and N protein specific Abs were produced by peptide immunization, which will be usefull for the study of SARS-CoV.

Figure 1

SDS-PAGE of the purified N protein of SARS-CoV and GST control protein. Lane 1: low molecular protein standards. Lane 2: control GST protein (with 26 kD) and Lane 3: the purified N protein of SARS-CoV (with 47 kD). SDS-PAGE was performed on a 12% polyacrylamide gel and stained using Coomassie brilliant blue.

Figure 2

The peptide-induced antibodies were capable of binding to N protein of SARS-CoV measured by western blot analysis. Lanes 1, 3 and 5 with loading of the purified N protein of SARS-CoV. Lanes 2, 4, 6 with loading of GST control protein. Lanes 1-2 were blotted with N1-peptide immunized rabbit serum. Lane 3-4 with N2-peptide immunized rabbit serum and Lane 5-6 with normal rabbit serum. The N protein and control GST protein were subjected to SDS-PAGE, then were transferred to PVDF membrane. The blot was probed with the antiserum (1:1000), and the immunological complex was detected with HRP-conjugated goat-anti rabbits IgG (Southern Biotech).