Preparation of a highly purified allergen from Dirofilaria immitis. Reaginic antibody formation in mice.

A Dirofilaria immitis protein allergen was purified; it had a molecular weight of 15,000-20,000 and a carbohydrate content of 2%. The allergenic activity of adult Dirofilaria extracts was assayed by passive cutaneous anaphylaxis (PCA) in rats using mouse sera obtained by immunization with various fractions. The mouse-Dirofilaria system was used to study the degree of purification of allergen. The purified Dirofilaria allergen appeared as one band after sodium dodecyl sulphate polyacrylamide gel (SDS-gel) electrophoresis and one precipitin arc by immunoelectrophoresis (IEP). It was inclined to aggregate in buffered solution. The results suggested that the allergen--reagin axis was a simple single antigen-antibody interaction. Immunological responses to the purified allergen were compared among four inbred strains, two hybrid strains and two outbred strains of mice. They produced relatively high titres of reaginic antibody but did not produce detectable indirect haemagglutinating test (IHA) antibody. Among the strains tested, BALB/c was a high responder and also contained to produce the reaginic antibody for longer than the other strains.