Chimeric CD47-CD63 Enables Small Extracellular Vesicles to Evade the Undesirable Phagocytosis

Area of Science:

• Biotechnology and Nanomedicine
• Cellular and Molecular Biology
• Immunology

Background:

• Extracellular vesicles (EVs), particularly small EVs (sEVs), are crucial for cell communication and show promise as drug delivery systems (DDSs).
• Therapeutic applications of EVs are hindered by rapid immune clearance by the mononuclear phagocyte system (MPS), leading to short circulation times and organ accumulation.

Purpose of the Study:

• To engineer sEVs with enhanced immune evasion properties for improved therapeutic efficacy.
• To investigate the potential of a chimeric CD47-CD63 protein to confer immune tolerance to sEVs.

Main Methods:

• A truncated CD63 protein was utilized to direct the sorting of a chimeric CD47-CD63 protein into sEVs.
• The binding of the CD47 extracellular domain to SIRPα was leveraged to activate the "do not eat me" phagocytic signal.
• In vitro assays were performed using activated macrophages and blood-derived mononuclear phagocytes to assess phagocytosis and uptake.

Main Results:

• sEVs enriched with the chimeric CD47-CD63 protein demonstrated effective evasion of phagocytosis by activated macrophages.
• The CD47-CD63 enrichment significantly reduced the uptake of sEVs by mononuclear phagocytes in vitro.
• Enriched sEVs exhibited a markedly prolonged circulating half-life and reduced accumulation in the liver, spleen, and lungs in vivo.

Conclusions:

• The chimeric CD47-CD63 protein successfully confers immune evasion properties to sEVs.
• This strategy represents a promising approach to overcome the limitations of MPS-mediated clearance for EV-based therapeutics.
• Engineered sEVs with immune evasion capabilities hold significant potential for advancing clinical applications in drug delivery.