Purification and Partial Characterization of a Vibrio fetus Immunogen

An antigen released into broth culture medium (2 mg/100 ml of culture medium) during 20-hr growth of Vibrio fetus was removed from the growth medium by salt precipitation [50 g of (NH(4))(2)SO(4)/100 ml of broth] and centrifugation. About 30 mg of the postgrowth broth (PGB) antigen protein was removed from other salt precipitable material during one polyacrylamide gel electrophoretic run. The PGB antigen was further purified by using gel filtration on Sephadex G-200, and a molecular weight of 135,000 was established. The purified PGB antigen was shown to contain protein and carbohydrate but not lipid and was a glycoprotein. The antigen had an isoelectric point at pH 4.2 and an R(F) value of 0.30 on acrylamide gel electrophoresis. At least one PGB antigen was detected in all (31) V. fetus isolants tested. These antigens were heat labile.