[Isolation of the IBR virus antigen for immunodiffusion]

A number of physicochemical and immunoelectrophoretic investigations as well as tests were carried out for the standardization of an antigen for immunodiffusion prepared from an IBR virus. The antigen showed strict specificity and maximum activity at a concentration forming a 7.5-8.0 mm diffusion disc in a radical immunodiffusion. It is made up of two antigenic components and shows a pronounced lability. The antigen reacts more intensely with immunoglobulins of the IgM type but is also active with regard to IgG. The antigen makes positive all serums with virus neutralizing antibodies having a titre of 1:16 and above. It is susceptible to standardization and shows stability as regards preservation in a lyophilized state.