Tests with a hybrid PV1-39, containing residues 1-39 of Vv5 from yellow jacket (Vespula vulgaris) and residues 40-204 of Pa5 from paper wasp (Polistes annularis), suggest the N-terminal region to be immunodominant. This region was studied further with hybrids PV1-18 and 18-39.

Hybrids were prepared by expression in yeast. Their antigenicity was tested by binding of Vv5-specific mouse monoclonal (mc) and polyclonal (pc) Abs, immunogencity by stimulation of Vv5-specific Ab responses in mice, and allergenicity by up-regulation of cell surface marker CD203c from basophils of yellow jacket-sensitive patients.

Two Vv5-specific mcAbs showed binding of PV1-39 and 18-39 but not PV1-18, and a third mcAb showed the opposite. Hybrid antigenicity with pcAb, and hybrid immunogencity, were in the order of Vv5 > PV1-39 > PV1-18 18–39. Allergenicity data from a single patient showed a similar order and tests with additional patients are being made.

The data with mcAbs suggest the presence of at least two adjacent epitope regions in PV-1-39. Each epitope region alone is less efficient than the bivalent PV1-39 to bind Vv5-specific pcAb as well as to stimulate such a response. The findings are relevant in the design of hybrids, with reduced allergenicity but retaining immnogenicity of natural allergen, for possible use as vaccines.