Immunodiffusion studies of purified equine infectious anemia virus

Antigenicity of purified equine infectious anemia (EIA) virus was examined by immunodiffusion against sera obtained from horses experimentally infected with EIA virus. The purified virus reacted with the infected horse serum, and virus-specific precipitating antibody was demonstrated. Furthermore, it was found that purified EIA virus reacted against the serum of horses infected with all strains of EIA virus which were antigenically different from one another. From the result, group-specific components of the virus rather than strain-specific ones were considered to be involved in the reaction. Serological reactivity was lost by adding antiserum from the infected horse to the antigen. The precipitating antibody usually appeared in the serum 1 to 2 weeks after the first febrile attack of EIA and remained for a longer period. Some characteristics of the purified antigen and specificity of the reaction for EIA are described.