Purification and characterization of a CHO cell-elongating toxin produced by Aeromonas hydrophila

A Chinese hamster ovary (CHO) cell-elongating toxin produced by Aeromonas hydrophila was purified from cell-free supernatant fluids by ammonium sulfate precipitation and fast protein liquid chromatography. The purified toxin had an isolelectric point (pl) of 3.7 and a molecular weight of 70,000 in a single band on isoelectric focusing (IEF) gels and SDS-PAGE gels, respectively. The N-terminal sequence, amino acids 1-20, and the amino acid content were determined from Western blots of the 70 kDa band. No homology with any known microbial toxin was found. CHO cell activity was not neutralized by antiserum to cholera toxin (anti-CT), and the toxin did not react with anti-CT on Western blots. The toxin did not increase cyclic AMP, cyclic GMP, or prostaglandin E2 levels in CHO cells. No cytotoxic activity was observed. Intragastric administration of purified toxin (5 x 10(4) and 5 x 10(8) CHO cell units) induced intestinal fluid accumulation in infant mice. These results suggest that this toxin may be a novel cytotonic toxin distinct from previously described toxins produced by A. hydrophila or A. sobria.