Expression of Recombinant Antibodies

Frenzel, André; Hust, Michael; Schirrmann, Thomas

Filamentous fungi of the genera Trichoderma and Aspergillus have the capacity to secrete large amounts of proteins and metabolites into the medium (117). They are widely used in the food and biotechnological industry, for example A. niger for citric acid production. Moreover, A. niger (subgenus A. awamori) and Aspergillus oryzae gained obtained GRAS status. Two promoters are typically used for the expression of antibodies in fungi: the glucoamylase promoter (glaA) (118) and the endoxylanase A promoter (exlA) (119). Antibody chains are usually fused to the aminoterminus of glucoamylase in Aspergillus and cellobiohydrolase I in Trichoderma spec., respectively, in order to obtain optimal secretion (120). Moreover, protease cleavage sites like KexB are introduced to release the antibody from glucoamylase before secretion (118). Yields of up to 1.2 g/L IgG were achieved in A. niger when both antibody chains were fused to glycoamylase. In Trichoderma reesei, 150 mg/L of a Fab fragment was obtained when both chains were fused with cellobiohydrolase I increasing yields 100-fold higher than with its natural signal peptide (121). A. awamori was used for the production of several scFvs, llama VHHs and antibody enzyme fusion proteins (117, 119, 122). A yield of 73.8 mg/L of an anti-EGFR-VHH was achieved in A. oryzae by using a Taka-amylase A signal sequence and 28 amino acids from the aminoterminal region of Rhizopus oryzae lipase (123).