Epitope mapping on the dendritic cell-specific ICAM-3-grabbing non-integrin (DC-SIGN) pathogen-attachment factor

Area of Science:

• Immunology
• Molecular Biology
• Glycobiology

Background:

• Dendritic cell-specific ICAM-3-grabbing non-integrin (DC-SIGN) is a C-type lectin expressed on myeloid cells.
• DC-SIGN recognizes pathogen-associated oligosaccharides, influencing Toll-like receptor (TLR) signaling and T cell responses.
• Polymorphisms in the DC-SIGN neck domain are linked to susceptibility to infections like SARS and HIV.

Purpose of the Study:

• To define structural and functional epitopes on DC-SIGN.
• To investigate the impact of these epitopes on DC-SIGN function, including ligand recognition, signaling, and multimerization.
• To explore the potential for targeted modulation of DC-SIGN-mediated immune responses.

Main Methods:

• Utilized naturally occurring isoforms and chimaeric DC-SIGN molecules.
• Employed antibodies to map seven distinct structural and functional epitopes.
• Assessed epitope exposure, multimerization dependence, and effects of neck domain truncations.
• Investigated antibody-induced microclustering and internalization.

Main Results:

• Identified three epitopes within the carbohydrate-recognition domain (CRD) and four within the neck domain.
• One CRD epitope was multimerization-dependent and monomer-specific.
• Neck domain epitopes were conformation-independent but affected by truncations.
• Neck-specific antibodies showed lower function-blocking but higher internalization-inducing activity.
• Crosslinking different epitopes resulted in varied cell surface microclustering.

Conclusions:

• Defined independent epitopes on DC-SIGN, offering insights into its structure-function relationship.
• Demonstrated that distinct epitopes mediate different functional outcomes, such as internalization versus function blocking.
• Suggests potential for designing reagents that selectively modulate DC-SIGN-expressing cells' immune functions without inhibiting pathogen recognition.