Specific targeting of MR1-antigen complexes using nanobodies

Area of Science:

• Immunology
• Structural Biology
• Biotechnology

Background:

• T cell receptor mimic (TCRm) antibodies offer therapeutic potential by targeting peptide-MHC complexes on tumor cells.
• MR1, an MHC class-I-like molecule, presents conserved microbial metabolites like 5-OP-RU.
• The generation of antibodies targeting MR1-metabolite complexes was previously unclear.

Purpose of the Study:

• To develop high-affinity nanobodies targeting the MR1-5-OP-RU complex.
• To characterize the molecular interactions and specificity of these nanobodies.
• To evaluate the therapeutic potential of MR1-targeting nanobodies and bispecific engagers.

Main Methods:

• Yeast display technology and in vitro affinity maturation were employed to generate nanobodies.
• In vitro and in vivo assays were used to assess the inhibition of MAIT cell responses.
• Crystal structures of MR1 in complex with ligands and nanobodies were solved.

Main Results:

• A nanobody with high affinity and specificity for the MR1-5-OP-RU complex was successfully generated.
• These nanobodies inhibited MAIT cell responses in vitro and in vivo.
• Crystal structures revealed the nanobody's co-binding mechanism with MR1 and 5-OP-RU.
• Engineered bispecific antibodies targeting MR1-5-OP-RU and CD3 demonstrated T cell-mediated killing of infected and tumor cells.

Conclusions:

• Nanobodies targeting the MR1-5-OP-RU complex can be generated with high affinity and specificity.
• These nanobodies can modulate MAIT cell responses, indicating therapeutic potential.
• Bispecific antibodies targeting MR1 offer a novel strategy for cancer and infectious disease immunotherapy.