Recombinant Dirofilaria immitis-derived antigen can suppress passive cutaneous anaphylaxis reactions

Background: High levels of antigen-nonspecific IgE are produced in animals infected with helminth parasites. Generally, the increase in IgE is thought to exacerbate allergic reactions. However, high levels of antigen-non-spec ific IgE may alter some features of anaphylactic reactions. To investigate the molecular mechanisms of antigen-nonspecific IgE production induced duri ng filarial infections, we previously constructed rDiAg (recombinant Dirofi laria immitis-derived antigen) in Escherichia coli. In the present study, w e examined the effect of rDiAg on the production of antigen-nonspecific IgE and on allergic cutaneous reactions in rats. Methods: Osmotic pumps filled with 200 mug of rDiAg or with 200 mul of PBS (control) were subcutaneously implanted in Wister rats, and plasma samples were collected weekly thereaf ter. IgE levels were determined by ELISA. Homologous passive cutaneous anap hylaxis (PCA) reactions with anti-DNP-As IgE were examined 21 days after im plantation. I-125-IgE binding assays were examined on peritoneal mast cells from rDiAg-infused rats and control rats. Results: Antigen-nonspecific IgE production was induced in rDiAg-infused rats. PCA reactions were suppresse d in rDiAg-infused rats in spite of high levels of IgE and a markedly incre ased expression of Fc epsilon RI. I-125-IgE did not bind to mast cells deri ved from rDiAg-infused rats, but it bound dose dependently to mast cells de rived from control rats. Conclusion: The present data support the hypothesi s that antigen-nonspecific IgE might protect aga inst antigen-specific IgE by means of competition for mast cell receptors. rDiAg is an essential fact or to induce antigen-nonspecific IgE in helminth infections. Copyright (C) 2001 S. Karger AG, Basel.