Analysis of the antigenic difference between Vero toxin 2 (VT2) and VT2 variant (VT2vh) of Verotoxin-producingEscherichia coliby a site-directed mutagenesis

Ouchterlony double gel diffusion analysis of the A and B subunits of purified Vero toxin 2 (VT2) and a variant of VT2 (VT2vh) demonstrated that the difference in antigenicity between VT2 and VT2vh is due to the difference in the B subunit of the two toxins. Analysis of mutants of VT2vh prepared by site-directed mutagenesis attributed the antigenic dissimilarity to the difference in the amino acid residue at position 24 of the B subunit.