A Single Monoclonal Antibody against the Peanut Allergen Ara h 2 Protects against Systemic and Local Peanut Allergy (1)
For the induction of anaphylaxis, sensitized mice were challenged i.v. with 20 μg roasted peanut extract in 200 μL PBS 2 weeks after sensitization. The local anaphylaxis was assessed by ear prick test. Mice were injected i.v. with 200 μL of Evans blue solution (0.5% in PBS). Afterwards, a drop of peanut extract solution (180 μg/20 μL PBS) was placed onto the outer ear skin of anesthetized mice. Pricks on the ear skin were performed with 23-G (0.6 mm Å∼25 mm) needles.
The antibody isotype is IgG2a, while the antibody has specificity for Ara h 2 and peanut extract as demonstrated by ELISA and dot blot. Cross-reactivity of this mAb to Ara h 1 and Ara h 6 was low.
The binding of immune-complexed anti-Ara h 2 to FcγRIIb was stronger than to free anti-Ara h 2, in line with previous findings showing that immune complexes bind FcγRIIb more ef- fectively than free mAb.
Injection of 200 μg mAbs anti-Ara h 2 into peanut-sensitized mice protected from anaphylactic reactions. In order to visualize extravasation, mice were pretreated i.v. with Evans blue. Allergen challenge by pricking into the ear skin with peanut extract induced vascular leakage in control mice. The protection conferred by passive vaccination with mAbs IgG anti-Ara h 2 was abrogated by systemic injection of FcγRIIb-blocking antibody. A comparable leakage to allergen-challenged mice without prior exposure to mAbs, demonstrating that in- hibitory receptor FcγRIIb is required for protection.
