Factors Influencing Determination of Antigenic Relationships between Western Equine Encephalomyelitis Virus Strains

Summary A number of variables influenced measurements of antigenic relationships between Western equine encephalomyelitis (WEE) strains. These were: a ) the infectious or noninfectious nature of the immunizing antigen, b ) the purity of the antigen, c ) the type of animal used for immune serum source and d ) the type of serologic test employed for measuring antigenic similarities or differences between virus strains. Such variations in immune responses have been interpreted as due in part to the selection by various hosts, during multiplication of the virus, of different antigenic subpopulations of WEE and in part to the measurement of different properties of the viruses by different serologic tests.