Soluble human interleukin-6 receptor. Expression in insect cells, purification and characterization

Area of Science:

• Biochemistry and Molecular Biology
• Immunology and Receptor Biology

Background:

• Interleukin-6 (IL-6) is a key cytokine involved in inflammation and immune responses.
• The IL-6 receptor (IL-6R) mediates IL-6 signaling, making its soluble form a target for therapeutic intervention.

Purpose of the Study:

• To express, purify, and characterize the extracellular domain of the human IL-6 receptor.
• To assess the biological activity and binding properties of the soluble IL-6 receptor.
• To investigate the pharmacokinetic profile of the soluble IL-6 receptor in vivo.

Main Methods:

• Expression of soluble human IL-6 receptor in baculovirus-infected insect cells (Sf158).
• Purification via affinity chromatography using immobilized IL-6.
• Characterization using SDS/PAGE, deglycosylation, UV spectroscopy, and real-time interaction analysis.
• Assessment of biological activity on HepG2-IL-6 cells and plasma clearance studies in rats.

Main Results:

• 6 mg of soluble IL-6 receptor was purified per liter of culture medium.
• The purified protein demonstrated binding to IL-6 (Kd = 500 pM) and induced haptoglobin mRNA synthesis in HepG2-IL-6 cells at 10 ng/ml.
• Plasma clearance in rats was biphasic, with IL-6/IL-6R complexes clearing faster than IL-6R alone, showing rapid accumulation in the liver.

Conclusions:

• The recombinant soluble human IL-6 receptor is biologically active and binds IL-6 with low affinity.
• The characterized pharmacokinetic properties provide a basis for potential therapeutic development.
• Monoclonal antibodies targeting specific regions of the soluble IL-6 receptor were generated.