IgE reactivity to α1 and α2 chains of bovine type I collagen in children with bovine gelatin allergy

Background: Anaphylactic reactions to measles, mumps, and rubella vaccines, including gelatin as a stabilizer, have been reported. It had been found that most of these reactions to live vaccines are caused by the bovine gelatin included in these vaccines. Gelatin mainly includes denatured type I collagen, which consists of α1 and α2 chains. Objective: The current study was designed to investigate the IgE reactivity to α1 and α2 chains of bovine type I collagen in gelatin-sensitive children. Methods: Serum samples were taken from 10 children who had anaphylaxis to the vaccines and high levels of specific IgE to bovine gelatin. Bovine type I collagen was isolated from bovine skin and then separated to aα1 and α2 chains by column chromatography. IgE reactivity to denatured type I collagen and its α1 and α2 chains was analyzed by immunoblotting, ELISA, and histamine release from the mast cells passive sensitized with IgE antibodies in pooled serum of the children. Results: All children had specific IgE to bovine type I collagen. Furthermore, IgE antibodies in their sera reacted with the α2 chain but not with the α1 chain. Similarly, the mast cells sensitized with pooled sera in the children showed α2 chain-specific histamine release but not α1 chain-specific histamine release. Conclusion: In gelatin allergy denatured bovine type I collagen is a major allergen and IgE-binding sites exist in the α2 chain of type I collagen.