Recombinant Antigen Based Sero-Diagnosis of Infectious Bronchitis

Background:
Avian Infectious bronchitis (IB) is a highly contagious viral respiratory infection of chickens, however, the IB virus (IBV) will also infect the urogenital and gastrointestinal tracts. IBV is the prototype species in the family Coronaviridae, genusGammacoronavirus, order Nidovirales. The clinical signs of infectious bronchitis are non-specific and so laboratory tests are required to confirm the diagnosis. Clinical signs are strongly dependent on the tropism (preferred tissue to infect) of the strain, but commonly include coughing, sneezing, and gasping in young birds, loss of appetite, and wet litter. Feed intake decreases sharply and growth is retarded. Mortality in young birds can be high (up to 30%), however minimal mortality is experienced in older birds (> 5 weeks old). Less common strains can cause a sharp drop in egg production in layers, and production usually drops to near zero within a few days. Recovery occurs within 3 – 4 weeks, however, some flocks never regain an economical rate of lay. During an outbreak, small, softshelled, irregular-shaped eggs are produced.:

Technology Details:
This assay is designed to measure the relative levels of antibody to IBV in chicken serum. A micro titration format has been developed in which a recombinant protein derived from IBV is coated onto each well. The antibody specific to IBV forms a complex with the coated virus antigen. After washing away unbound materials from the wells, anti-chicken horseradish peroxidase (HRP) is added and colour development occurs in presence of substrate. The assay is useful to assess the immune status of vaccinated birds and the management of large flocks. The innovation has the following advantages:

1. Recombinant antigen-based single serum dilution ELISA reduces the reagent costs and increases the number of samples to be screened.:
2. Has excellent diagnostic specificity and sensitivity.:
3. A total of 45 sera samples in duplicate can be analyzed and their antibody titres quantified with sufficient accuracy in a single microtitre plate, whereas in serial dilution ELISA only 8 – 10 samples can be analyzed.:
4. The recombinant antigen is non-infectious and free from the risk of bio-hazard. The test is very specific as it avoids cross-reactivity among related proteins.:
5. The recombinant antigen is specific for all pathotypes of the virus.:
6. The kit is available in the form of recombinant antigen-coated ELISA plates with a shelf life of 6 months under refrigerated conditions.