Bordetella PT IgA ELISA

Enzyme immunoassay for the quantitative determination of IgA class antibodies against Bordetella pertussis in human serum or plasma (citrate). Bordetella pertussis is a respiratory pathogen that causes pertussis, commonly known as whooping cough, a localized infection of the ciliated epithelium of the bronchial tree. Pertussis is characterized by a prolonged paroxysmal cough often accompanied by an inspiratory whoop. The disease affects mainly children, but adults have also been increasingly reported to be affected. The pathogen produces toxins which cause local damage to the cilia of epithelial cells, which leads to prolonged illness and pertussis. Disease presentation varies with age and history of previous exposure or vaccination. Severe disease is infrequent in healthy, vaccinated persons. Infants, particularly those who have not received the primary vaccination series against pertussis, are at risk for complications and mortality. In addition to B. pertussis, three other Bordetella species can cause disease in humans: B. parapertussis, B. holmesii, and B. bronchiseptica. B. parapertussis causes a pertussis-like illness that is generally milder than pertussis because the bacteria do not produce pertussis toxin. Co-infection of B. pertussis and B. parapertussis is not unusual. B. pertussis is of worldwide prevalence. Globally, 20-40 million cases of pertussis occur each year, 90 % of which are in developing countries, and there are up to 400,000 fatalities each year, mostly in young infants. Transmission of B. pertussis occurs primarily via close direct contact with an infected person or inhalation of airborne droplets. Symptoms develop following inhalation of the airborne pathogen. The organism is highly contagious, with up to 90 % of household contacts developing the disease. Infected persons are most contagious in the catarrhal and the paroxysmal stages. The incubation period is usually seven to 10 days, with a range of 4-21 days. Typical pertussis symptoms occur in three different stages: catarrhal, paroxysmal, and convalescent. The catarrhal stage lasts for about 1-2 weeks, and is characterized by non-specific symptoms such as rhinorrhea, sneezing, low-grade fever and cough. The second stage is the paroxysmal stage, lasting for about 4-6 weeks, and is characterized by various pathognomonic symptoms of pertussis such as episodes of paroxysmal cough with a characteristic whooping sound. The final stage is the convalescent stage. During this stage, the respiratory symptoms gradually decrease although cough can continue for months. Many factors can alter the usual course of pertussis, causing an atypical presentation. Previously vaccinated adolescents and adults may have less severe paroxysmal symptoms. The quantitative immunoenzymatic determination of IgA-class antibodies against B. pertussis toxin (PT) is based on the ELISA (Enzyme-linked Immunosorbent Assay) technique. Microtiter strip wells are coated with B. pertussis toxin (PT) antigens to bind corresponding antibodies of the specimen. After washing the wells to remove all unbound sample material horseradish peroxidase (HRP) labelled anti-human IgA conjugate is added. This conjugate binds to the captured B. pertussis toxin (PT)-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 (PT)-specific IgA 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.