Glycomodification and characterization of anti-colorectal cancer immunotherapeutic monoclonal antibodies in transgenic tobacco

초록

Anti-colorectal cancer mAb CO17-1A (IgG(2a)) recognizes the antigen GA733, which is highly expressed on the surface membrane of human colorectal carcinoma cells. In this study, a transgenic tobacco system for the production of mAb CO17-1A was developed. The mAb construct included a KDEL sequence, an endoplasmic reticulum (ER) retention signal attached to the C-terminus of the heavy chain, to target accumulation of mAb into ER. An immunoblot showed significantly enhanced levels of expression of the plant-derived mAbK (mAb(P)K) CO17-1A compared to mAb(P) CO17-1A mAb without the KDEL sequence. An ELISA assay using human colorectal carcinoma cells confirmed that expression of mAb(P)K was also significantly higher than that of mAb(P). Glycosylation analysis revealed that mAb(P) had plant-specific glycans; whereas, mAb(P)K primarily had oligomannose glycans. FACS showed that the Fc domains of both mAb(P)K and mammalian-derived mAb (mAb(M)) had similar binding activity to the Fc gamma RI receptor (CD64). However, the Fc domains of the mAb(P) had slightly lower binding activity to the Fc(gamma)RI receptor than both mAb(P)K and mAb(M). The antibody-dependent cell cytotoxicity of mAb(P)K, against human colorectal cancer cells, was as efficient as mAb(M); whereas mAb(P) was very low. These results suggest that KDEL localized and accumulated mAb(P) in the ER and eventually enhanced the expression of mAb(P) with oligomannose glycan and similar anti-cancer biological activity to the parental mAb(M).

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