Biotechnology

A-Maizing Antibodies

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Science  28 Mar 2008:
Vol. 319, Issue 5871, pp. 1735
DOI: 10.1126/science.319.5871.1735c

Monoclonal antibodies that block the binding of HIV to cellular receptors have been shown to neutralize the virus in vitro, to protect monkeys from HIV challenge, and to prevent viral transmission through mucosal tissue. But such antibodies can be produced only at high cost and low capacity through expression in mammalian cells and are therefore not optimal for commercial manufacture. Two studies describe the purification of the anti-HIV antibody 2G12 from genetically engineered maize on a large and cost-effective scale. Rademacher et al. used a fluorescent marker protein to identify and breed transgenic plants that accumulated a high amount of 2G12 in the seed endosperm, the plant's specialized storage tissue. Ramessar et al. purified the antibody from 2G12-expressing maize without using protein A-affinity chromatography, a step typically used for antibody isolation, but toxic if protein A leaches into the final product. Despite differences between mammalian and plant-specific processing of protein-linked carbohydrate, both studies found that glycan modification of maize-produced 2G12 antibodies did not alter antibody binding to the gp120 subunit of the envelope protein of HIV. The HIV-neutralizing properties of mammalian cell- and maize-produced 2G12 were comparable, with the latter being somewhat more potent. Maize-produced 2G12 could be an effective prophylactic mucosal microbicide, and large-scale plant cultivation and prolonged seed storage in the absence of cold temperatures make this method of antibody production economically attractive. — LC

Plant Biotechnol. J. 6, 189 (2008); Proc. Natl. Acad. Sci. U.S.A. 105, 3727 (2008).

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