Highly efficient transient expression of functional recombinant antibodies in lettuce

An efficient, scalable transient expression system has been developed and characterized for production of recombinant antibodies in lettuce. The transient expression system utilizes lettuce (Lactuca sativa L.) vacuum-infiltrated with Agrobacterium tumefaciens bearing antibody genes cloned into a single or two separate expression vectors. The lettuce can be obtained commercially (grocery stores or directly from growers), so plant growth facilities are not required. Compared to previously described systems, this transient expression system is extensively modified to reduce cost and manipulations and provides for significantly increased levels of antibody production. The optimized agro-infiltration procedure produced as much as 20-80 mg of functional antibody per kilogram of fresh lettuce leaf tissue in less than a week. This procedure has been used to produce a humanized IgG1 κ anti-tissue factor antibody (hOAT) as well as other antibodies. The results demonstrate that transient expression of recombinant antibodies in lettuce is very efficient, inexpensive and readily scalable. Thus, it is a useful tool for small-scale production of functionally active antibodies and other pharmaceutically important proteins and can be used to facilitate humanization or optimization of antibodies or to produce quantities of antibody (in the range of 100 mg) sufficient for in vivo studies.