Polyclonal antibodies to glutathione S-transferase-verotoxin subunit A fusion proteins neutralize verotoxins

The A1 subunits of verotoxin-1 (VT1) and VT2 genes were cloned into pGEX-4T-2 for the expression of glutathione S-transferase (GST) fusion proteins. The N-terminal and the transmembrane regions of the A1 subunits were excluded from the constructs in order to increase the product yields. Polyclonal anti-VT1A1 and anti-VT2A1 antibodies were produced by immunizing rabbits with GST-VT1A1 and GST-VT2A1 fusion proteins, respectively. The antibodies were tested for their ability to neutralize active toxins from 45 W-producing Escherichia coli (VTEC) strains. The antibodies had significantly high neutralizing activities against their homologous toxins. The average percentages of neutralization of VT1 by anti-GST-VT1A1 and anti-GST-VT2A1 were 76.7% +/- 7.9% and 3.6% +/- 2.3%, respectively, and those of VT2 were 1.7% +/- 2.3% and 82.5% +/- 13.9%, respectively. VT2 variant toxin was neutralized by anti-GST-VT2A1, with cross neutralization being a possible consequence of sequence homology between VT2 and a VT2 variant. To our knowledge, this is the first report on the production of polyclonal antibodies from GST-VT fusion proteins. The antibodies were shown to exhibit specific toxin neutralizing activities and may be useful for immunological diagnosis of VTEC infections.