DIRECT EVALUATION OF THE IMMUNODOMINANCE OF A MAJOR ANTIGENIC SITE OFFOOT-AND-MOUTH-DISEASE VIRUS IN A NATURAL HOST

The immunodominance of a major antigenic site of foot-and-mouth diseas e virus (FMDV) (serotype C; clone C-s8cl) in a natural host has been e valuated by serum immunoglobulin fractionation. Nineteen sera from eit her convalescent or vaccinated swine were fractionated by affinity chr omatography using a synthetic peptide representing antigenic site A (t he G-H loop of capsid protein VPI) coupled to a Sepharose matrix Antig en-binding and neutralizing activities of serum fractions were quantit ated. On average, about 57 or 27% of the virus-neutralizing activity ( and about 35 or 12% of the virus-binding activity) from convalescent o r vaccinated swine, respectively, corresponded to antibodies against s ite A. The results provide direct evidence of the important contributi on of site A, and also of additional sites unrelated to site A, in the evoking of neutralizing antibodies by FMDV in a natural host. The pro portion of antibodies directed to site A varied greatly among individu al swine. Some animals evoked remarkably low levels of antibodies spec ific for site A although they were competent to raise antibodies again st other antigenic sites of FMDV. Thus, the major antigenic site of FM DV shows heterogeneous dominance in a natural host. Possible implicati ons for evolution of viral quasispecies are discussed. (C) 1995 Academ ic Press, Inc.