A general system for targeting MHC class II-antigen complex via a single adaptable loop.

Area of Science:

• Immunology
• Structural Biology
• Protein Engineering

Background:

• Major histocompatibility complex class II (MHCII) molecules present peptide antigens to CD4+ T cells, crucial for immune responses.
• Targeting peptide-MHCII complexes with T cell receptors (TCRs) or TCR-like antibodies shows therapeutic potential for autoimmune diseases and microbiome tolerance.

Purpose of the Study:

• To introduce a general and rapid method, TRACeR-II, for developing peptide-specific MHCII binders.
• To create versatile binders with a small scaffold and single recognition loop for targeting diverse MHCII antigens.

Main Methods:

• Development of targeted recognition of antigen-MHC complex reporter for MHCII (TRACeR-II) binders.
• Utilizing a small helical bundle scaffold with a single recognition loop for peptide-MHCII interaction.
• Employing computational protein design for in silico generation of specific binding sequences.

Main Results:

• Demonstrated rapid generation of TRACeR-II binders with affinities in the low-nanomolar to low-micromolar range.
• Achieved binding affinities comparable to established TCRs and antibodies.
• Successfully designed specific binding sequences computationally from a SARS-CoV-2 peptide sequence.

Conclusions:

• TRACeR-II offers a straightforward and versatile approach for targeting antigen-MHCII complexes.
• This method bypasses the need for combinatorial selection on complementarity-determining region loops.
• TRACeR-II facilitates the development of novel therapeutics for immune-related conditions.