Bordetella PT IgG ELISA

Enzyme immunoassay for the quantitative determination of IgG-class antibodies against Bordetella pertussis toxin (PT) in human serum or plasma (citrate). Bordetella species are non-spore-forming encapsulated bipolar, coccoid (pale-staining) Gram-negative bacilli (about 0.3-0.5 μm thick and 1 μm long). The genus consists of the human pathogens B. pertussis and B. parapertussis, and B. bronchiseptica which cause enzootic infections in various wild and domestic animal species. B. pertussis is the pathogenic agent of pertussis and exists only in ill people; B. parapertussis causes 5-20 % of a milder and often clinical unapparent form of pertussis. B. bronchiseptica has seldomly (e. g. close contact with animals) human pathogenic significance as opportunistic secondary infectious agent in mixed infections (bronchitis, pneumonia, wound infection). Pertussis or whooping cough is a bacterial infection of the respiratory system. It is a highly contagious childhood disease which appears seldomly in adults. It is transmitted by airborne droplets. B. pertussis has the ability to stick to the cilia of the epidermal cells of the respiratory system. Fragments of the bacterial cell wall (ExoToxin = tracheal Cytotoxin, TCT) inhibit the movement of the cilia in the tracheal mucosa. After an incubation time of one to three weeks the disease runs through three stages (s. table below). The lethality is 0.6 % and concerns babies in the first six months with more than 70 %. For newborn and premature infants it is higher (1-2 %). In Africa beside measles virus B. pertussis is the main reason for high infant mortality. The distribution of the disease is worldwide. Clinical pertussis is followed by natural acquired immunity which is long-lasting but not permanent. In most countries an active vaccination is recommended which leads to 90 % protection for three to twelve years. Usually the immunization preparation is combined with diphtheria and tetanus toxoids. The quantitative immunoenzymatic determination of IgG-class antibodies to Bordetella pertussis toxin (PT) is based on the ELISA (Enzyme-linked Immunosorbent Assay) technique. Microtiter strip wells are coated with B. pertussis toxin to bind corresponding antibodies of the specimen. After washing the wells to remove all unbound sample material horseradish peroxidase (HRP) labelled anti-human IgG conjugate is added. This conjugate binds to the captured B. pertussis toxin specific antibodies. The immune complex formed by the bound conjugate is visualized by adding tetramethylbenzidine (TMB) substrate which gives a blue reaction product. The intensity of this product is proportional to the amount of B. pertussis toxin specific IgG antibodies in the specimen. Sulphuric acid is added to stop the reaction. This produces a yellow endpoint colour. Absorbance at 450 nm is read using an ELISA microwell plate reader.

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