L-Asparaginase-Induced Allergy in Mice: Effects of Concomitant Drugs and Anti-IgE Antibody

BACKGROUND: L-Asparaginase (L-Asp) derived from E. coliis one of the essential drugs for the treatment of acute lymphoblastic leukemia (ALL) and lymphoma. Native L-Asp often causes hypersensitivity reactions, including anaphylaxis, which account for termination and inferior outcome of L-Asp therapy of ALL. Since the characteristics of L-Asp-induced hypersensitivity are not well documented, there is neither suitable treatment for hypersensitivity to L-Asp nor animal model of L-Asp allergy. In addition, some anti-cancer drugs, used concomitantly with L-Asp, affect lymphocyte activities, the role of such drugs on L-Asp hypersensitivity is not known.

Aims:In this study, we induced type I hypersensitivity to E. coliL-Asp in mice in order to investigate the mechanism and treatment of L-Asp allergy. Anti-IgE antibody, binding to Fc region of IgE to block the binding to FcεRI receptor, was used as a candidate for the treatment of L-Asp hypersensitivity. Furthermore, we examined the effects of methotrexate (MTX) and cyclophosphamide (CY). which reportedly impair the functions of Th17 and Treg cells, respectively.

Methods: Male BALB/c mice (7 week old) were intraperitoneally injected L-Asp (10, 20, 100 IU/mouse) with Al (OH)₃gel on days 0 and 14. The right ears of the mice were locally sensitized on days 17, 20, 23 by intradermal injection of L-Asp (1, 2, 10 IU/mouse). Antigen challenge was carried out on day 26 by intradermal injection of L-Asp. MTX (50, 100, 200 mg/kg) and CY (150 mg/kg) were intraperitoneally administrated on day -2 and day 12. On day 25, either anti-IgE antibody (50, 100 mg/mouse) or control IgG was intraperitoneally administered to the sensitized mice. The ear thickness was measured (n=6 or more). H&E and toluidine blue stainings of ear sections were performed.

Results: L-Asp challenge immediately induced ear edema, in a dose-dependent manner. The reaction reached to a peak at 1 hr after stimulation (dosage: sensitization = 100 IU/mouse, challenge = 10 IU/mouse; edema thickness: 31.25±3.8 μm vs control 4.38±1.9 μm, p<0.01), which subsided within 24 hr. Microscopic observations showed eosonophil infiltration (H&E staining; 0.5±0.2 cells/HPF in control ears and 10.4±1.0 cells/HPF in challenged ears, P<0.001) and degranulation of mast cells (toluidine blue staining; 8.4±0.9 % in control ears and 47.6±5.8 % in challenged ear, P<0.001). Anti-IgE antibody significantly inhibited the ear swelling to 7.3±1.2 μm (P<0.01) as well as microscopic changes in eosinophil infiltration and mast cell degranulation. When the mice were treated with anticancer drugs prior to sensitization, the ear swellings were augmented by CY (43.54±4.0 μm, P<0.05) but not MTX (31.67±5.5 μm, not significant). Anti-IgE antibody also inhibited CY-augmented ear swelling.

Conclusions: From these results, we firstly established animal model for type I hypersensitivity to L-Asp. Using this model, we conclude that non-anaphylactogenic neutralizing antibody of IgE, such as omalizumab, can be a candidate drug for the treatment of L-Asp hypersensitivity. Also, CY-induced suppression of Treg function may enhance Th2 responses so as to augment L-Asp hypersensitivity. Further investigations for the detection and avoidance of L-Asp hypersensitivity are under the way.