Production of glycosylated human anti-Hepatitis B monoclonal antibodies in the microalgae Phaeodactylum tricornutum

Monoclonal antibodies (mAbs) represent actually the major class of biopharmaceuticals.

They are produced recombinantly using living cells as biofactories. Among the different

expression systems currently available, microalgae represent an emerging alternative

which displays several biotechnological advantages. Indeed, microalgae are classified

as generally recognized as safe organisms and can be grown easily in bioreactors with

high growth rates similarly to CHO cells. Moreover, microalgae exhibit a phototrophic

lifestyle involving low production costs as protein expression is fuelled by

photosynthesis. However, questions remain to be solved before any industrial

production of algae-made biopharmaceuticals. Among them, protein heterogeneity as

well as protein post-translational modifications need to be evaluated. Especially, N-

glycosylation acquired by the secreted recombinant proteins is of major concern since

most of the biopharmaceuticals including mAbs are N-glycosylated and it is well

recognized that glycosylation represent one of their critical quality attribute.

In this paper, we assess the quality of the first recombinant algae-made mAbs

produced in the diatom, Phaeodactylum tricornutum. We are focusing on the

characterization of their C- and N-terminal extremities, their signal peptide cleavage and

their post-translational modifications including N-glycosylation macro- and

microheterogeneity. This study brings understanding on diatom cellular biology,

especially secretion and intracellular trafficking of proteins. Overall, it reinforces the

positioning of P. tricornutum as an emerging host for the production of

biopharmaceuticals and prove that P. tricornutum is suitable for producing homogenous

recombinant proteins bearing high mannose-type N-glycans.