In situ imaging of honeybee (Apis mellifera) venom components from aqueous and aluminum hydroxide–adsorbed venom immunotherapy preparations

Background Treatment with aqueous and aluminum hydroxide (Al[OH] 3 )–adsorbed purified honeybee (Apis mellifera) venom (HBV) preparations can reduce the incidence of side effects associated with venom immunotherapy. Objective The aim of the present study was to assess these purified HBV immunotherapy preparations in situ . Methods Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) was used to visualize the distribution of HBV components. The preparations were administered on the back legs of naive Wistar rats. The rats were killed, and cryosectioned tissue sections were subjected to hematoxylin and eosin staining and MALDI-MSI analyses. Results Low-density maps of tissue distribution of HBV peptides, such as secapin, mast cell degranulating peptide, and melittin (Api m 4) were detected in the tissue after administration of HBV immunotherapy preparations. In addition, release of biogenic amines, cytokines, and leukotrienes was observed, and the distribution of HBV allergens, such as Api m 1 and Api m 2, was shown. At the 24-hour time point, the major HBV allergen Api m 1 was still detected at the site of Al(OH) 3 -adsorbed HVB injection, whereas in the case of aqueous HBV preparation, all the allergens, as well as most of the biogenic amines, were cleared at the 24-hour time point. Conclusion The present study shows that the majority of low-molecular-weight HBV components are rapidly removed from the site of venom immunotherapy administration. Furthermore, Al(OH) 3 -adsorbed HBV preparation demonstrated a depot effect, prolonging the availability of bee venom allergens at the site of administration.