Serological conservation and location of the adhesin of avian Escherichia coli type 1 fimbriae.

By inoculation of mice with purified type 1-like fimbriae isolated from an avian Escherichia coli strain, a monoclonal antibody (mAb G5) was obtained. mAb G5 reacted in an enzyme-linked immunosorbent assay (ELISA) with type 1-like and type 1A fimbriae differing in the molecular masses of their major fimbrial subunit and isolated from several avian E. coli strains. The specificity of mAb G5 for type 1 fimbriae was assessed in a whole bacteria ELISA with 16 reference E. coli strains expressing different types of fimbriae. Immunoblotting experiments showed that mAb G5 recognized the 29 kDa minor component of reference type 1A fimbriae which has been identified as the adhesin. mAb G5 also recognized the 29 kDa component of type 1-like and type 1A fimbriae expressed by avian E. coli strains, suggesting that the adhesin is antigenically conserved among these fimbriae. Immunoelectron microscopic studies gave evidence that the adhesin could be located mainly at the tip or both at the tip and along the fimbriae, depending on the strain.