Four transgenic Nicotiana tabacum plants were generated that expressed a murine monoclonal antibody kappa chain, a hybrid immunoglobulin A-G heavy chain, a murine joining chain, and a rabbit secretory component, respectively. Successive sexual crosses between these plants and filial recombinants resulted in plants that expressed all four protein chains simultaneously. These chains were assembled into a functional, high molecular weight secretory immunoglobulin that recognized the native streptococcal antigen I/II cell surface adhesion molecule. In plants, single cells are able to assemble secretory antibodies, whereas two different cell types are required in mammals. Transgenic plants may be suitable for large-scale production of recombinant secretory immunoglobulin A for passive mucosal immunotherapy. Plant cells also possess the requisite mechanisms for assembly and expression of other complex recombinant protein molecules.
A functional comparison was made between a monoclonal secretory antibody generated in transgenic plants and its parent murine IgG antibody.The affinity constants of both antibodies for a Streptococcus mutans adhesion protein were similar. However the secretory antibody had a higher functional affinity due to its dimeric structure. In the human oral cavity, the secretory antibody survived for up to three days, compared with one day for the IgG antibody. The plant secretory antibody afforded specific protection in humans against oral streptococcal colonization for at least four months. We demonstrate that transgenic plants can be used to produce high affinity, monoclonal secretory antibodies that can prevent specific microbial colonization in humans. These findings could be extended to the immunotherapeutic prevention of other mucosal infections in humans and animals.
Two genes of Agrobacterium tumefaciens encode enzymes that together produce indoleacetic acid (IAA). The first gene, iaaM, encodes tryptophan monooxygenase which converts tryptophan to indoleacetamide (IAM). The second gene, iaaH, encodes indoleacetamide hydrolase which converts IAM to IAA. We have engineered each of the two genes to be expressed at either high constitutive levels or in a tissue-specific manner. These chimeric Recent advances in plant transformation and regeneration technology make plants ideal subjects for studying the interactions of different organs and cell types in a developmental system. Plants consist of a large number of distinct tissues and organs. The coordination of these many tissue types as a unit and the continuous develop~ment of new organs requires a complex system of communication. Several classes of phytohormones, including the cytokinins and auxins, can greatly influence the patterns of differentiation. The ability to manipulate the relative levels of phytohormones and observe the consequent effects would be extremely useful in elucidating the roles of these compounds in the processes of differentiation.Agrobacterium tumefaciens is the causative agent of crown gall disease, a neoplastic growth that affects many dicotyledonous plant species. It has been demonstrated that Agrobacterium transfers a portion of its DNA, the T-DNA, to the plant where it is integrated into plant nuclear DNA (for a review, see Fraley et al. 1986). Expression of several genes in the T-DNA results tPresent address:
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