Phagocytic clearance of targeted cells with a synthetic ligand

Area of Science:

• Biotechnology
• Immunology
• Cell Biology

Background:

• Phosphatidylserine exposure on dead cells acts as an 'eat-me' signal, recognized by Protein S (ProS) and Mer tyrosine kinase (MerTK) for cell engulfment.
• The ProS-MerTK pathway's potent cell removal capability has not been therapeutically utilized.
• Targeted cell elimination is crucial for treating various diseases, including cancer and autoimmune disorders.

Purpose of the Study:

• To develop a synthetic protein modality, Crunch, for targeted cell elimination by modifying the ProS-MerTK pathway.
• To assess the therapeutic potential of Crunch in preclinical models.

Main Methods:

• Modification of Protein S (ProS) to create Crunch, replacing its phosphatidylserine-binding motif with a nanobody or single-chain variable fragment for specific cell targeting.
• Conjugation of a green fluorescent protein nanobody to Crunch to target and eliminate green fluorescent protein-expressing melanoma cells in mouse models.
• Conjugation of an anti-CD19 single-chain variable fragment to Crunch for eliminating CD19+ B cells, evaluating therapeutic effects in a systemic lupus erythematosus model.

Main Results:

• Crunch effectively eliminated green fluorescent protein-expressing melanoma cells in mouse transplantation models.
• Anti-CD19 fragment-conjugated Crunch successfully eliminated CD19+ B cells, demonstrating a therapeutic effect in a systemic lupus erythematosus model.
• Both mouse and human versions of Crunch proved effective, highlighting its broad applicability.

Conclusions:

• Crunch is a novel synthetic ligand designed for targeted cell elimination, inspired by the ProS-MerTK engulfment pathway.
• This synthetic protein modality shows significant therapeutic potential for eliminating specific cell populations, including cancer cells and autoimmune-related B cells.
• Crunch represents a promising new tool for cell-targeted therapies with demonstrated efficacy in preclinical models.