Production of antisera against the enterotoxin of Bacteroides fragilis and their use in a cytotoxicity neutralization assay of HT-29 cells.

To study the enterotoxin of Bacteroides fragilis, the colon carcinoma cell line HT-29 was used in a standard cytotoxicity assay. We produced high-titer neutralizing antisera in rabbits and goats against both crude and purified toxin and developed a cytotoxicity neutralization assay for use in confirming enterotoxin activity in culture filtrates and stools. The neutralization titers of the antisera on the colon carcinoma cell line HT-29 ranged from 1,600 to 2,400. In an antibody screening enzyme-linked immunosorbent assay, titers ranged from 10(4) to 10(5). The antisera produced against the highly purified toxin also neutralized the enterotoxic activity of the toxin and were monospecific by immunoelectrophoresis.