Quantitative and qualitative characterization of virus envelope proteins and specific polyclonal antibodies

A method for simultaneous qualitative and quantitative characterization of virus envelope proteins and virus-neutralizing antibodies is described. The quantitative estimate is based solely on the precipitation of the antibody/antigen (Ab/Ag) complexes at equivalence under equilibrium conditions. The qualitative analysis is performed by determining the diffusion coefficients, i.e., molecular masses of antigen and antibodies. Isolation, purification, labelling of antigen and antibodies and use of any standards are not required. The analyses are carried out directly in crude biological fluids in which antigen and antibodies naturally occur. The results obtained are independent on the avidity of the Ab/Ag system to be analysed. The method was tested by using antigenic subunits of Newcastle disease virus (NDV) and four chicken anti-NDV immune sera of different avidities.