Betenbaugh The inability of insect cells to generate glycoproteins similar in carbohydrate composition to those of mammalian cells has limited the wider application of insect cells as vehicles for the production of glycoproteins of mammalian origin. While mammalian cells often produce glycoproteins containing complex oligosaccharides terminating in sialic acid, insect cells typically generate glycoforms containing short truncated oligosaccharides terminating in mannose or N-acetylglucosamine. The composition of these covalently-attached carbohydrates, especially the presence of sialic acid, can significantly affect a glycoprotein's structure, stability, biologicaal activity, and in vivo circulatory half-life. Consequently, the objective of this project is to manipulate carbohydrate processing pathways in insect cells in such a way that these cells will produce sialylated glycoproteins. This inter-disciplinary and inter-agency project will involve participating scientists and engineers from Johns Hopkins University, the University of Wyoming, the Food and Drug Administration (FDA), the National Institutes of Health (NIH), and the Forest Service of the Department of Agriculture (USDA).