LOCALIZATION OF POTENTIAL BINDING-SITES FOR THE EDEMA DISEASE VEROTOXIN (VT2E) IN PIGS

The purpose of this study was to identify organs and cells to which th e edema disease verotoxin (VT2e) could bind in pigs. Frozen 4-5 mu m t hick sections of organs usually affected in edema disease (colon, spin al cord, cerebellum and eyelid) and organs not usually affected (liver , ileum) from two 5- to 6-week-old weaned pigs were permeabilized with acetone, then exposed to VT2e. Unbound VT2e was removed by washing an d bound VT2e was detected by immunohistochemistry. In the eyelid, doub le-label immuno-fluorescence was used to identify the cells to which V T2e bound. VT2e was shown to bind to all six organs that were examined . The toxin bound to arteries in all organs, to veins in all organs ex cept the liver, and to enterocytes in the ileal crypts. Double labelli ng of eyelid with monoclonal antibodies specific for von Willebrand fa ctor or alpha-smooth actin and VT2e showed that the toxin bound to end othelial and vascular smooth muscle cells. The binding of VT2e to endo thelium is consistent with findings for other verotoxins but binding t o vascular smooth muscle has not been reported for other verotoxins. I t is concluded that i) factors other than the presence of receptors fo r VT2e influence the development of lesions in edema disease, and ii) smooth muscle necrosis, which is characteristic of the vascular lesion s in edema disease, may be due to a direct action of toxin on smooth m uscle cells.