Hybrid IgA2/IgG1 antibodies with tailor-made effector functions

Area of Science:

• Immunology
• Protein Engineering
• Biochemistry

Background:

• Immunoglobulin A (IgA) is crucial for mucosal immunity, existing as polymers bound to secretory component.
• Immunoglobulin G (IgG) is the primary antibody in blood, functioning as a monomer.
• Current antibody engineering often focuses on enhancing specific effector functions.

Purpose of the Study:

• To create hybrid antibodies merging IgA and IgG effector functions.
• To investigate the properties and stability of these novel IgA/IgG hybrid antibodies.
• To explore new strategies for engineering antibodies with combined functionalities.

Main Methods:

• Production of IgA2/IgG1 hybrid antibodies by engineering the heavy chain.
• Analysis of polymer formation, J chain incorporation, and polymeric Ig receptor binding.
• Assessment of complement activation, FcgammaRI and Protein A binding.
• Evaluation of in vivo half-life and avidity for murine FcRn.
• Investigation of antibody stability under varying pH conditions by replacing Cgamma1 with Calpha1.

Main Results:

• Successfully produced IgA2/IgG1 hybrid antibodies exhibiting properties of both IgA and IgG.
• Hybrid antibodies formed polymers with J chain and bound the polymeric Ig receptor, similar to IgA.
• These proteins activated complement and bound FcgammaRI and Protein A, like IgG.
• Despite containing Cgamma2 and Cgamma3, hybrid proteins showed a short in vivo half-life, correlating with higher avidity for FcRn.
• Antibodies with Calpha1 replacing Cgamma1 demonstrated resistance to extreme pH, indicating enhanced stability.

Conclusions:

• Engineered hybrid antibodies can successfully combine distinct IgA and IgG effector functions.
• The C-terminal region of the IgG heavy chain influences IgA-like polymerization and receptor binding.
• Shortened in vivo half-life in hybrid antibodies may be linked to FcRn avidity.
• Incorporation of Calpha1 can confer enhanced stability to antibody structures.
• These findings provide a foundation for designing antibodies with tailored effector functions and improved stability.