Abstract
The baculovirus/insect cell system has proven to be a very powerful tool for the expression of several therapeutics. Nevertheless, these products sometimes suffer from reduced biological activity and unwanted side effects. Several studies have demonstrated that glycosylation can greatly influence the structure, function, half-life, antigenicity and immunogenicity of various glycoproteins. Yet, the glycosylation pattern of insect cell-derived products is not favorable for many applications. Especially, the presence of core α1,3-linked fucose bears the risk of causing immediate hypersensitivity reactions in patients with allergy. In this study, we evaluated the impact of fucose residues on the allergenic potential of an insect cell-expressed vaccine candidate. In order to block the GDP-L-fucose de novo synthesis pathway, we integrated the Pseudomonas aeruginosa GDP-6-deoxy-D-lyxo-4-hexulose reductase (RMD) gene into a baculovirus backbone. This virus was then used for the expression of soluble influenza A virus hemagglutinin (HA). Expression studies showed that the co-expression of RMD did not influence the overall level of recombinant protein secretion. We confirmed the result of our strategy by analyzing PNGase A-released N-glycans using MALDI-TOF-MS. In order to evaluate the biological impact of defucosylation of influenza HA we tested the binding activity of IgE derived from the sera of patients with allergy to the purified antigen. The non-fucosylated HA showed a 10-fold decrease in IgE binding levels as compared to wildtype variants.