2 - Competition Radioimmunoassays for Characterization of Antibody Reactions to Viral Antigens

Publisher Summary Characterizations of viral antigens and antibody responses to these are performed by a variety of precipitation, immunological, and biological tests such as double immunodiffusion, complement fixation, enzyme inhibition, and hemagglutination inhibition assays. Each of these methods has at least two potential disadvantages. First, only a portion of an antibody response to an antigen is measured and second, no data on the nature of the antigenic determinants mediating the cross-reaction are provided. Because competition radioimmunoassays assays can overcome both of these disadvantages, its utilization for assessments of antigenic relationships has increased dramatically. In general, the solid-phase type of assay is not as versatile and quantitative as the radioimmunoprecipitation (RIP) method for the assessment of an antibody–antigen reaction. This is mainly attributable to the use of non-purified antigens and the technical problem in controlling the antigen concentration in the test system. In virology, hepatitis B virus provided the initial stimulus for the application of this type of methodology to the study of a viral agent. The development of competition RIP assays led to the acquisition of a considerable body of knowledge on the definition of antigenic determinants of the hepatitis surface antigen. With the advent of techniques to produce protein antigens in a highly purified form, the competition RIP method was adapted to the study of other viruses. This chapter describes the methods of competition RIP assay as developed for immunological assessments of adenoviruses and influenza viruses. It presents a technical background that can be used for the performance of the same methods with other viral protein antigens and the type of information that can be generated from their application.