Precipitating antigens associated with Marek's disease viruses and a herpesvirus of turkeys

Precipitating antigens associated with a number of Marek's disease virus strains and with a turkey herpesvirus have been analyzed. The 'A' antigen has been defined as the major soluble antigen in feather follicles of infected chickens, which is identical with the major antigen usually present in supernatants of chicken kidney cell cultures infected with strains of Marek's disease virus. 'BC' antigens are 2 or more antigens which are usually not noted in skin extracts but present in cultured cells infected with Marek's disease virus or turkey herpesvirus, in addition to the 'A' antigen. Some of the virus strains examined were positive and others negative for 'A' antigen, but all contained the 'BC' antigens. Results of agar-gel precipitin tests suggested a serological classification of the group of avian herpesviruses formed by Marek's disease viruses and turkey herpesvirus into 3 types. Pathogenic strains of Marek's disease virus and their attenuated A- variants, represented by the HPRS-16 strain (HPRS-16, JM, GA, VC, Oldenburg). Apathogenic Marek's disease virus, represented by the HPRS-24 strain. Turkey herpesvirus and its A- variants, represented by the FC126 strain. A serological subdivision corresponding to the different grades of pathogenicity of virus strains of the first type was not possible. Differences between antigens associated with the 3 types of virus were apparent from the antigen and antibody titres against homologous and heterologous reagents. Precipitin bands produced by homologous antigen and antibody were stronger than those produced by heterologous reagents. Differences between 'A' antigens of the 3 virus types were characterized by spur patterns of precipitin bands indicating a partial identity. At least 3 'BC' precipitin bands were noted; at least one was group-specific and one appeared to be type-specific.