Results of enzyme-linked immunosorbent assay of the reaction between heat-inactivated isolates of K88ab + , K88ac + , K99, or Fas + ETEC and serum collected before and after vaccination of rabbits to produce antibodies specific to the recombinant fimbrial antigens. Data are expressed as mean optical density ± standard deviation (SD) from 3 experiments done in duplicate. Asterisks indicate a significant difference ( P