Envelope proteins of avian infectious bronchitis virus: Purification and biological properties

Immunoadsorbents, made with monoclonal antibodies, were used to purify the spike and membrane proteins of infectious bronchitis virus (IBV). The purified proteins were inoculated into rabbits to produce antisera. The rabbit anti-spike sera neutralized the infectivity of the virus whereas the anti-membrane sera did not. IBV-infected chickens produced antibodies to both the spike and membrane proteins. Both these antibodies were at their highest concentration about 9–11 days after inoculation, whereas neutralizing antibodies were present only at very low concentrations at that time. Neutralizing antibodies were at their highest concentration 21 days after inoculation. A second inoculation of virus at 42 days induced an anamnestic antibody response to the spike and membrane proteins and also for the neutralizing antibodies. The neutralizing, anti-spike and anti-membrane antibodies all reached highest concentrations 7–11 days after this inoculation. The advantages of purifying viral proteins using affinity chromatography with monoclonal antibodies are discussed.