IgE and IgG antibodies to beta-propiolactone and human serum albumin associated with urticarial reactions to rabies vaccine.

We examined the antibody response to a rabies vaccine doubly inactivated with 0.025% beta-propiolactone and 0.1% tri(n)butyl phosphate and stabilized with 2.5% human serum albumin. Antibodies were measured by using the following four antigen preparations: complete doubly inactivated rabies vaccine, rabies vaccine inactivated only with tri(n)butyl phosphate, beta-propiolactone and human serum albumin, and human serum albumin alone. The fluid phase of the preparation of beta-propiolactone and human serum albumin completely inhibited IgE binding to solid-phase vaccine. Of 21 subjects with urticarial reactions to a booster, 19 had IgE to doubly inactivated vaccine and to beta-propiolactone and human serum albumin. None of 27 immunized subjects without urticaria had detectable IgE. In paired pre- and postimmunization sera, IgE appeared in six of seven of the subjects with urticaria and in one of seven nonreactors. These sera did not contain a significant level of IgE to singly inactivated vaccine or to human serum albumin alone.