Expression and characterization of an anti‐(hepatitis B surface antigen) glycosylated mouse antibody in transgenic tobacco (Nicotiana tabacum) plants and its use in the immunopurification of its target antigen

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Abstract
Transgenic plants expressing recombinant immunoglobulins have arisen as an alternative technology for the large‐scale production of antibodies useful in therapeutics and in industrial processes. In the present paper we report the expression in transgenic tobacco (Nicotiana tabacum) of an anti‐HBsAg [anti‐(hepatitis B virus surface antigen)] mouse IgG1 mAb (monoclonal antibody), currently used for the industrial purification of the recombinant vaccine antigen. Using the sweet potato sporamin signal peptide, a KDEL (Lys‐Asp‐Glu‐Leu) ER (endoplasmic reticulum) anchorage domain, and a heavy‐ and light‐chain gene tandem construction, we generated F1 plants in which the expression of the antibody accounted for 0.5% of the total soluble proteins. The ‘plantibody’ (functional IgG antibody produced in plants) was easily purified by Protein A–Sepharose chromatography with a yield of ≈35 μg/g of fresh leaf material, and its glycosylation indicated that, irrespective of the KDEL signal, the molecule is modified in both the ER and Golgi. Finally, a successful comparison of the plantibody with the ascites‐derived mAb in the immunoaffinity purification of the vaccine recombinant HBsAg was performed. Taken as a whole, our results show that the large‐scale production of this antibody of industrial relevance in transgenic tobacco is feasible.