Secretion of Fusion Proteins into Milk by Transgenic Mouse Mammary Epithelium

Mammary epithelial cell processing may be more efficient than that found in traditional cell cultures. Certain fusion proteins were not efficiently secreted from traditional cell culture, which includes COS and BHK cells. Yields of the proteins were very low and sometimes undetectable. The same proteins were secreted into milk by animals transgenic for the constructs at typical levels of 1 mg per ml active protein. The fusion proteins are antibodies fused to enzymes and heterologous proteins, as well as protein fusions to β-casein. Transgenics has enabled the secretion of proteins not normally secreted and has permitted the secretion ofcomplex proteins that remain a significant challenge for cell culture.