Sensitivity of immunoassays for detecting cross-reactivity of homologous venom proteins of yellow jackets.

The venoms of yellow jackets of Vespula flavopilosa, V. pennsylvanica, V. squamosa, and V. vulgaris have similar proteins. Their major components comprise antigen 5, hyaluronidase, and phospholipase A1. The homologous venom proteins share very similar biochemical properties. With the exception of antigen 5 and phospholipase of V. squamosa, they also have very similar antigenic properties. The venom proteins of V. squamosa and V. vulgaris were equally effective in inducing secondary antibody responses in mice that were primed with V. squamosa proteins. No cross-reaction of V. squamosa and V. vulgaris venom proteins was detected on immunodiffusion with specific mouse antisera. A very weak cross-reaction was detected by inhibition of ELISA, and a moderate cross-reaction was detected by direct ELISA. The varying cross-reactivity is a consequence of the different sensitivities of the assays. The sensitivity of the direct ELISA is apparently caused by a greater enhancement of the binding of low-affinity antibodies for the solid-phase antigen than that of high-affinity antibodies. Most untreated yellow jacket-sensitive patients tested had about tenfold higher levels of IgG specific for V. vulgaris proteins than those specific for V. squamosa proteins. This pattern of antibody specificity can be accounted for on the basis of cross-reactivity of these yellow jackets as suggested by the results with the mouse system.