Avidity optimization of a MAGE-A1-specific TCR with somatic hypermutation

Area of Science:

• Immunology
• Cancer Biology
• Molecular Biology

Background:

• Adoptive cell transfer using T-cell receptors (TCRs) can redirect T cells to eliminate cancer cells.
• Cancer testis antigens (CTAs) are promising targets due to their presence in tumors and immune-privileged testes.
• Natural TCRs targeting self-antigens like CTAs often exhibit low avidity due to central tolerance mechanisms.

Purpose of the Study:

• To improve the method of directed evolution of TCR avidity via somatic hypermutation.
• To enhance the avidity of the hT27 TCR, which targets the CTA HLA-A2-MAGE-A1_278-286.
• To evaluate the impact of enhanced TCR avidity on T-cell function and specificity for cancer immunotherapy.

Main Methods:

• Utilized an improved directed evolution method based on somatic hypermutation to engineer TCRs.
• Introduced point mutations into the hT27 TCR to enhance its avidity for the target CTA.
• Transduced human T cells with engineered TCRs and assessed their binding, cytokine production, and cytotoxic activity.

Main Results:

• Identified eight point mutations that significantly improved TCR avidity.
• Engineered TCRs demonstrated enhanced binding to target antigen tetramers.
• Transduced T cells showed increased production of IFN-γ and IL2, and enhanced cytotoxicity against cancer cells.
• Most mutations maintained target specificity, with one mutant exhibiting exceptionally high avidity.

Conclusions:

• Somatic hypermutation is effective in optimizing TCR avidity for cancer immunotherapy.
• Enhanced TCR avidity translates to improved T-cell effector functions against tumors.
• This approach offers a promising strategy for developing more potent TCR-based cancer therapies.