Humanized antibodies: enhancing therapeutic utility through antibody engineering

Area of Science:

• Immunology
• Biotechnology
• Therapeutic Antibodies

Background:

• Monoclonal antibody technology and antibody humanization have expanded therapeutic potential.
• Antibody humanization transfers mouse antibody binding sites into human genes, aiming for non-immunogenic human antibodies.
• Antibody effector functions can be enhanced by manipulating antibody constant region genes.

Purpose of the Study:

• To produce a humanized version of the OKT3 antibody using human IgG4 and kappa constant regions.
• To evaluate the in vitro characteristics and therapeutic potential of the humanized OKT3 antibody.
• To investigate the impact of Fc receptor (FcR) binding modification on T cell activation.

Main Methods:

• Humanization of the OKT3 antibody by incorporating human IgG4 and kappa constant regions.
• In vitro assessment of cytokine release and T cell activation markers.
• Affinity measurements comparing murine and humanized OKT3.
• Engineering an FcR mutant of humanized OKT3 by substituting leucine with glutamic acid at residue 235.

Main Results:

• Humanized OKT3 retained in vitro characteristics of murine OKT3, including cytokine release and T cell activation.
• Humanized OKT3 exhibited comparable affinity to murine OKT3 (1.4 x 10(9) M-1 vs. 1.2 x 10(9) M-1).
• The FcR mutant demonstrated abrogated FcR I binding and significantly reduced T cell activation.

Conclusions:

• Humanized OKT3 maintains key biological functions of the murine form.
• Modification of FcR binding in humanized OKT3 can modulate T cell activation.
• The engineered FcR mutant of humanized OKT3 presents potential as an improved therapeutic for transplantation and autoimmune diseases.