Low Api m 10 in Commercial Honeybee Venom AIT Products Fails to Induce Prominent Humoral Responses in BALB/c Mice

Background: Honeybee venom (HBV) allergy is a serious, potentially life-threatening, and highly prevalent immediate-type hypersensitivity reaction in humans. It can be treated with allergen-specific immunotherapy (AIT). Api m 10 is one of the major allergens in HBV and is thought to be under-represented in HBV AIT products. Objective: We used a mouse model to investigate whether the Api m 10 amounts contained in marketed HBV AIT products are sufficient to induce humoral immune responses in vivo. Methods: BALB/c mice were immunized subcutaneously with either (1) increasing amounts of untagged recombinant (r) Api m 10 (0.1-50 µg), with or without aluminum hydroxide or (2) 4 aqueous HBV AIT products (0.001-50 µg total HBV protein). Levels of antibody against rApi m 10 and other HBV allergens were investigated using indirect ELISA. Results: Administration of isolated rApi m 10 induced humoral immune responses (allergen-specific pan-IgG, IgG1, IgG2a, IgG2b, IgG3, and IgE; cumulative threshold dose, 1.5-3.1 µg) in BALB/c mice, which were able to block human IgE. HBV AIT products induced production of antibody towards rApi m 1, nApi m 4, and, albeit inconsistently, rApi m 3. By contrast, no prominent humoral immune responses to rApi m 10 were observed in mice repeatedly immunized with HBV AIT products. Conclusions: While isolated rApi m 10 is immunogenic in BALB/c mice, the amount of Api m 10 in complex HBV AIT products is insufficient to induce prominent antibody responses.