Effects of exogenous agents on the action of Bordetella parapertussis heat-labile toxin on guinea pig skin

The BvgAS two-component system of Bordetella spp.: a versatile modulator of virulence gene expression

Bordetella pertussis and the closely related species B. parapertussis and B. bronchiseptica colonize the respiratory tract and cause related diseases in man or mammalian species, respectively. Expression of virulence factors by these pathogens is coordinately regulated by the BvgAS two-component system according to changes in the growth conditions. Signal transduction by the BvgAS system is characterized by a complex His-Asp-His-Asp phosphorelay. This system controls the expression of two distinct subsets of genes either in a positive (vag genes) or in a negative (vrg genes) manner. Most of the known virulence factors such as several toxins and adhesins are encoded by vag genes, whereas the functions of most vrg genes and the biological significance of the vrg regulon are not yet clear. This review discusses the current knowledge about the molecular mechanisms of virulence regulation and their relevance for infection by these respiratory pathogens.

Dermonecrotic activity of a cell wall preparation from Fusobacterium necrophorum

A cell wall preparation of Fusobacterium necrophorum induced haemorrhagic necrosis in the skins of guinea pigs and rabbits. Effects in mice and rats were weak or absent. The toxic activity of the cell wall preparation was not reduced by heat treatment. A dermonecrotic toxin was isolated from the cell wall preparation with sodium dodecylsulphate and concentrated by precipitation with ethanol. A preparation of the bacterial cytoplasm from Fus. necrophorum induced mainly erythema.

Heat-labile toxin from Bordetella parapertussis induces contraction of smooth muscle cells in culture

The ability of Bordetella heat-labile toxin (HLT) to contract various types of cells in culture was examined. HLT from B. parapertussis induced contraction of cultured smooth muscle cells from trachea, intestine, uterus and vas deferens as well as from aorta. The time required for contraction decreased as the dose of B. parapertussis HLT increased from 3 to 100 MID/ml. Upon exposure of cells to concentrations of toxin greater than 100 MID/ml, at least 2 hr was required for contraction. HLT from B. parapertussis did not affect cultured cardiac or skeletal muscle cells within 8 hr after the exposure to HLT (100 MID/ml). No effect on other types of primary culture cells or established cells such as Chinese hamster ovary (CHO) cells has been described. These data indicate that the primary target cells for HLT might be smooth muscle cells.

Purification and characterization of the heat-labile toxin of Bordetella pertussis

A procedure is described for purification of pertussis heat-labile toxin (PEHLT) from cells of Bordetella pertussis. The purification procedure, performed in the cold and in the presence of protease inhibitors, gives 1,350-fold purification with yields of about 60%. The toxin was shown to be a single-chain polypeptide of 140 kDa, pI 6.02. It was completely inactivated by heating at 56 degrees C for 60 min. Rabbit antiserum prepared against PEHLT neutralized the toxin and gave a single precipitin line on immunodiffusion. In immunodiffusion assays, this anti-PEHLT serum did not react with pertussis toxin, filamentous hemagglutinin, or preparations of pertussis adenylate cyclase. Purified PEHLT elicited dermonecrosis and atrophy of the spleen. PEHLT is extraordinarily active; 0.4 X 10(-12) g caused necrotic lesions in newborn mice, and with 18- to 20-g mice the 50% lethal dose was about 11 X 10(-9) g.

Inhibition of heat-labile toxin from Bordetella parapertussis by fatty acids

The ability of heat-labile toxin (HLT) from Bordetella parapertussis to induce skin lesions in guinea pigs was found to be inhibited by lipids isolated from skin layers of adult mice, which are refractory to the lesion-inducing activity of HLT. These lipids were identified as linoleic and oleic acids. Other long-chain unsaturated fatty acids were also found to inhibit HLT; however, fatty alcohols, neutral lipids, phospholipids, cholesterol, prostaglandin, and leukotriene had no measurable effects on HLT action. The data presented in this report indicate that the ability of HLT to induce skin lesions in animals may depend, at least in part, on the free fatty acid content of the skin layer.