Expression of yellow jacket and wasp venom Ag5 allergens in bacteria and in yeast.

: Antigen 5 (Ag5), of unknown biological function, is one of the major venom allergens of vespids and fire ants. We have compared the expression of Ag5 in bacteria and in yeast. Recombinant Ag5 from bacteria formed an insoluble intracellular product, which was not properly folded, but that produced in Pichia pastoris was secreted to the extracellular medium. Immunochemical characterizations showed the secreted Ag5 to have the native structure of the natural protein. This is of interest since the B cell epitopes of Ag5 are mainly of the discontinuous type. These studies were made with Ag5s from yellow jacket (Vespula vulgaris) and paper wasp (Polistes annularis), and with hybrid Ag5 molecules that contained partial sequences of these two species. In vitro allergenicity studies with sera from yellow jacket-sensitive patients showed that some of these hybrid molecules had a greatly reduced allergenicity but retained the immunogenicity of the natural allergen. This could be of importance for immunotherapy of this type of allergy.