Production of a Ric c3 hypo-allergen with no IgE binding or anaphylactogenic activity

Area of Science:

• Biochemistry
• Immunology
• Plant Science

Background:

• Castor bean (Ricinus communis L.) is a versatile oilseed with over 700 applications, but its allergens, Ric c1 and Ric c3, can cause allergic reactions.
• Ric c3 cross-reacts with common food and aeroallergens, posing a significant challenge for individuals with multiple sensitivities.

Purpose of the Study:

• To investigate the impact of specific amino acid mutations on the IgE binding and allergenic potential of the Ric c3 protein.
• To engineer a hypoallergenic mutant of Ric c3 for potential use in allergy immunotherapy.

Main Methods:

• Recombinant mutant protein (mrRic c3) was produced in E. coli by substituting key glutamic acid residues with leucine in IgE-binding regions.
• Allergenicity was assessed by measuring IgE, IgG1, and total IgG levels in immunized mice and evaluating mast cell degranulation in rats.

Main Results:

• The mrRic c3 mutant exhibited significantly reduced mast cell degranulation compared to the wild-type protein.
• Mice immunized with mrRic c3 showed lower levels of specific IgE and IgG1 antibodies.
• The mutant protein demonstrated an altered structure, reduced pro-inflammatory response stimulation, and decreased IgE binding, while retaining the ability to induce blocking antibodies.

Conclusions:

• Mutating specific amino acid residues in Ric c3 can create a hypoallergenic variant.
• This hypoallergenic mutant allergen (mrRic c3) holds promise for the development of novel allergy immunotherapy (AIT) strategies.