Application of purified recombinant antigenic spike fragments to the diagnosis of avian infectious bronchitis virus infection

• DOI: 10.1007/s00253-012-4143-8
• Publication Date: 2012-06-20T14:49:42Z
• Authors: Kuan-Hsun Lin; Chuen-Fu Lin; Shyan-Song Chiou; Ai-Ping Hsu; Min-Shiuh Lee; Chao-Chin Chang; Tien-Jye Chang; Jui-Hung Shien; Wei-Li Hsu
• Keywords: 0301 basic medicine; Membrane Glycoproteins; Infectious bronchitis virus; Molecular Sequence Data; Enzyme-Linked Immunosorbent Assay; Sequence Analysis, DNA; Antibodies, Viral; Sensitivity and Specificity; Recombinant Proteins; 3. Good health; 03 medical and health sciences; Viral Envelope Proteins; Spike Glycoprotein, Coronavirus; Animals; Amino Acid Sequence; Coronavirus Infections; Antigens, Viral; Chickens; Poultry Diseases

The spike (S) protein, containing two subunits, S1 and S2, is the major immunity-eliciting antigen of avian infectious bronchitis virus (IBV), a highly contagious disease of chickens. Several immunogenic regions, mainly located within the S1 subunit, have been identified. Nonetheless, these immune-dominant regions were defined using selected monoclonal antibodies or using a short peptide approach that involves only certain limited regions of the S protein. In addition, some immune-dominant regions are located in hypervariable regions (HVRs) which are not present in all serotypes. Hence, the aim of this study was to determine a broader range of antigenic regions that have strong antibody eliciting ability; these could then be applied for development of an IBV-diagnostic tool. Initially, the S1 and part of the S2 subunit protein (24-567 amino acids) were expressed as five fragments in prokaryotic system. The antigenicity was confirmed using IBV immunized sera. Performance of the S subfragments was evaluated by ELISA using a panel of field chicken sera with known IBV titres determined by a commercial kit. This indicated that, among the five antigenic recombinant proteins, the region S-E showed the highest specificity and sensitivity, namely 95.38 % and 96.29 %, respectively. The κ value for the in-house ELISA using the S-E fragment compared to a commercial kit was 0.9172, indicating a high agreement between these two methods. As region S-E harbors strong immunogenicity within the spike protein, it has the potential to be exploited as an antigen when developing a cost-effective ELISA-based diagnosis tool.