Neutralizing activity against Clostridium difficile toxin in the supernatants of cultured colostral cells.

Human colostral specimens were obtained from 60 Japanese postpartum women within the first 3 days after delivery. Neutralizing activity against Clostridium difficile toxin was evaluated with Y1 adrenal cells in miniculture. When Y1 adrenal cells were exposed briefly to the toxin, they showed a rounding response in culture, resembling that effected by Escherichia coli enterotoxin; however, preincubation of the toxin with aqueous phase of colostrum significantly reduced its cytopathic effect on Y1 adrenal cells. Of 60 colostral specimens, 17 samples had neutralizing activity against the toxin. Cell-free supernatants of colostral cells cultured for 7 days without mitogens contained significant amounts of both immunoglobulin A (IgA) and IgM, but very small amounts of IgG. Neutralizing activity of cell-free supernatants of cultured colostral cells was evaluated as described above. Neutralizing activity against the toxin was identified in five samples of culture supernatants out of 60 colostral cell specimens. In all five cases, the aqueous phase of colostrum also had a neutralizing effect against C. difficile toxin. Neutralizing activity against the toxin found in five supernatants of cultured colostral cells was completely abolished only by anti-human IgA antibody as assessed by immune precipitation.