Expression and glycoengineering of functionally active heteromultimeric IgM in plants

Area of Science:

• Biotechnology
• Immunology
• Plant Molecular Biology

Background:

• Immunoglobulin M (IgM) antibodies are crucial for innate immunity and emerging as therapeutics.
• Mammalian cell culture for IgM production is expensive, necessitating alternative methods.
• Plants are established systems for recombinant protein production, but their capacity for complex proteins like IgM was unproven.

Purpose of the Study:

• To investigate the feasibility of producing functional monoclonal IgM antibodies in plants.
• To analyze the glycosylation patterns and biological activity of plant-produced IgM.
• To explore plant-based glycoengineering for producing human-like IgM glycosylation.

Main Methods:

• In planta expression of the monoclonal antitumor IgM PAT-SM6 (SM6).
• Analysis of IgM assembly into heterooligomers (pentamers and hexamers).
• Detailed glycosylation analysis and in planta glycoengineering.

Main Results:

• Functionally active monoclonal antitumor IgM (SM6) was successfully generated in plants.
• Plant-produced SM6 assembled correctly and exhibited site-specific complex and oligomannosidic N-glycans.
• In planta glycoengineering produced SM6 with sialylated human-type oligosaccharides, comparable to plasma-derived IgM.
• Biochemical, biophysical, and biological properties of plant-derived SM6 glycoforms matched human-derived counterparts.

Conclusions:

• Plants can successfully produce complex human proteins like IgM antibodies.
• In planta production offers a promising, cost-effective alternative for therapeutic IgM.
• Controlled glycosylation in plants facilitates studies on the role of sugar moieties in IgM function.