Serological and immunological relations between the 146S and 12S particles of foot-and-mouth disease virus.

Intact 146S particles of the seven serotypes of foot-and-mouth disease virus (FMDV) produce type-specific precipitating, complement-fixing and neutralizing antibodies in cattle and guinea-pigs. However, the 12S structural subunit, produced from the virus particle by mild acid treatment (pH 6) or by heating at 56 degrees C, although stimulating the production of precipitating and complement-fixing antibodies, produces only low levels of neutralizing antibody. Nevertheless, 12S antibody in guinea-pigs primed with a vaccine prepared from 146S particles. Moreover, heterotypic 12S and 146S particles also boosted the neutralizing antibody response to the first virus. These results point to an antigenic similarity between the 146S particles of each type and to a close antigenic relationship between the 146S and 12S particles.