For the past 50 years or so, chicken eggs have played a vital role in producing the flu vaccine. Now scientists report another application for the breakfast staple: manufacturing fully functional human monoclonal antibodies, molecules that mimic the immune system to fight specific invaders.

Among the cells in the immune system's arsenal are the so-called B lymphocytes, each of which makes a specific antibody. By cloning a single B lymphocyte, researchers can mass produce identical antibody molecules that will attack a single, specific target. "Monoclonal antibodies have demonstrated great success as human therapeutics, with over 25 approved for human therapeutic use and an increasing number of these proteins in clinical development," remarks Robert J. Etches of Origen Therapeutics. "We expect the demand for more potent anticancer monoclonal antibodies and for lower production costs to increase at a rate that will tax existing cell culture production systems."

In a bid to manufacture the antibodies in a more cost-efficient manner, Etches and his colleagues recruited chickens to man the production lines. First, they inserted genes encoding one antibody, as well as genes that controlled its expression, into chicken embryonic stem cells. These stem cells were then introduced into developing chick embryos. When the resulting animals themselves laid eggs, they contained milligram amounts of the desired antibodies. According to a report published in the September issue of Nature Biotechnology, the resulting monoclonal antibodies also demonstrated a 10- to 100-fold increase in cell-killing ability compared to those produced by conventional cell culture approaches. The egg production method also offers a relatively short eight-month production time and a good starting point for isolation of the protein from the stable and sterile environment provided by the egg, the scientists say, adding that many good manufacturing practices are long-established from vaccine production facilities that use eggs.

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