Alga-made anti-Hepatitis B antibody binds to human Fcγ receptors

Microalgae are unicellular eukaryotic organisms which represent an emerging alternativeto other cell biofactories commonly used to produce monoclonal antibodies. Microalgaedisplay several biotechnological advantages such as their rapid growth rate and theirphototrophic lifestyle allowing low production costs as protein expression is solar-fueled.Recently, a fully-assembled recombinant IgG antibody directed against Hepatitis B surfaceantigen was produced and secreted in the culture medium of the diatom Phaeodactylumtricornutum. A biochemical characterization of this recombinant antibody demonstratedthat the Asn-297 was N-glycosylated by oligomannosides.In the immune system, antibodies interact with effector molecules and cells through theirFc part and the recognition of Fcγ receptors (FcγR) which are important for inducingphagocytosis of opsonized microbes. Interactions between IgG and FcγR are influenced bythe N-glycan structures present on the Asn-297.In this study, we characterized the binding capacity of the anti-hepatitis B recombinantIgG produced in P. tricornutum to two human Fcγ receptors (FcγRI and IIIa) using acellular binding assay and surface plasmon resonance (SPR). This allowed us todemonstrate that the alga-made antibody is able to bind FcγRI with a reduced affinity andengages FcyRIIIa with 3-times higher affinity compared to a control human IgG1.