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-nonspecific IgE may alter some features of anaphylactic reactions. To investigate the molecular mechanisms of antigen-nonspecific IgE production induced during filarial infections, we previously constructed rDiAg (recombinant Dirofilaria immitis-derived antigen) in Escherichia coli. In the present study, we 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 microg of rDiAg or with 200 microl of PBS (control) were subcutaneously implanted in Wistar rats, and plasma samples were collected weekly thereafter. IgE levels were determined by ELISA. Homologous passive cutaneous anaphylaxis (PCA) reactions with anti-DNP-As IgE were examined 21 days after implantation. (125)I-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 suppressed in rDiAg-infused rats in spite of high levels of IgE and a markedly increased expression of Fc epsilon RI. (125)I-IgE did not bind to mast cells derived from rDiAg-infused rats, but it bound dose dependently to mast cells derived from control rats.


CONCLUSIONS
The present data support the hypothesis that antigen-nonspecific IgE might protect against antigen-specific IgE by means of competition for mast cell receptors. rDiAg is an essential factor to induce antigen-nonspecific IgE in helminth infections.
Furuhashi
Y
Y
Section of Environmental Parasitology, Department of International Health Development, Division of Public Health, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan.
Imai
S
S
Tezuka
H
H
Fujita
K
K
D000818:Animals; D000909:Antibodies, Helminth / Q000096:biosynthesis / Q000276:immunology; D000918:Antibody Specificity; D000937:Antigen-Antibody Reactions; D000947:Antigens, Helminth / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology*; D002630:Chemotactic Factors / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology*; D004183:Dirofilaria immitis / Q000235:genetics / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D015801:Helminth Proteins / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology*; D006636:Histamine Release / Q000187:drug effects; D007073:Immunoglobulin E / Q000096:biosynthesis / Q000276:immunology; D015918:Infusion Pumps, Implantable; D008297:Male; D008407:Mast Cells / Q000276:immunology; D010323:Passive Cutaneous Anaphylaxis / Q000276:immunology*; D010529:Peritoneal Cavity; D051381:Rats; D017208:Rats, Wistar; D011993:Recombinant Fusion Proteins / Q000276:immunology; D020133:Reverse Transcriptase Polymerase Chain Reaction
C118621:22U kDa excretory-secretory protein, Dirofilaria immitis; D000909:Antibodies, Helminth; D000947:Antigens, Helminth; D002630:Chemotactic Factors; C104085:DIPA protein, Dirofilaria immitis; D015801:Helminth Proteins; D011993:Recombinant Fusion Proteins; C083690:neutrophil chemotactic factor, Dirofilaria immitis; D007073:Immunoglobulin E