Biological activities and chemical composition of purified tracheal cytotoxin of Bordetella pertussis

Abstract

Specific destruction of ciliated epithelial cells lining the large airways is the primary respiratory tract cytopathology associated with human Bordetella pertussis infections. We have purified a single low-molecular-weight glycopeptide, tracheal cytotoxin (TCT), that appears to cause this pathology. By using a combination of solid-phase extraction and reversed-phase high-pressure liquid chromatography, about 700 nmol of biologically active peptide can be isolated from 1 liter of B. pertussis culture supernatant (approximately 60% yield). TCT at concentrations of 1 microM destroyed the ciliated cell population when incubated with respiratory epithelium in vitro. This concentration of TCT is similar to the concentrations found in the culture supernatant of growing B. pertussis. Purified TCT also inhibited DNA synthesis of hamster trachea epithelial cells in a quantitative, dose-dependent fashion. Endotoxin was not detected in the purified material, and neither B. pertussis nor Escherichia coli endotoxin could duplicate the biological activities of TCT. Amino acid and amino sugar analyses of purified TCT revealed the presence of glucosamine, muramic acid, alanine, glutamic acid, and diaminopimelic acid in molar ratios of 1:1:2:1:1. This suggests that TCT, the released ciliostatic principle of B. pertussis, is a disaccharide tetrapeptide subunit of peptidoglycan.