Antibody complementarity-determining regions (CDRs): a bridge between adaptive and innate immunity

Area of Science:

• Immunology
• Molecular Biology
• Infectious Diseases

Background:

• Complementarity determining regions (CDR)-related peptides can exhibit antimicrobial, antiviral, and antitumor activities, independent of the native antibody's specificity.
• Understanding the non-specific functions of antibody fragments is crucial for developing novel immunomodulatory agents.

Purpose of the Study:

• To investigate the immunomodulatory effects of a synthetic V(H)CDR3 peptide derived from a mouse monoclonal antibody.
• To explore the therapeutic potential of this peptide against systemic candidiasis.

Main Methods:

• A synthetic peptide identical to the V(H)CDR3 of a mouse monoclonal antibody specific for difucosyl human blood group A was synthesized.
• Macrophage uptake and subsequent cellular responses, including cytokine production, PI3K-Akt pathway activation, and TLR-4 expression, were analyzed.
• Therapeutic efficacy against systemic candidiasis was evaluated in vivo.

Main Results:

• The synthetic V(H)CDR3 peptide was readily taken up by macrophages.
• Uptake led to stimulation of proinflammatory cytokine production, activation of the PI3K-Akt pathway, and increased TLR-4 expression.
• The V(H)CDR3 peptide demonstrated therapeutic effects against systemic candidiasis without direct candidacidal activity.

Conclusions:

• Antibody fragments, such as V(H)CDR3 peptides, can modulate cellular anti-infective immune responses.
• These findings suggest a potential role for antibody fragments as regulatory peptides influencing innate immunity.
• This opens new avenues for therapeutic strategies targeting infectious diseases by leveraging antibody-derived peptides.