Sulfated polyanions have been successfully
significant advantage of this system is the high expresused to rapidly obtain and maintain stable single-cell sussion levels which can be achieved much more quickly pension of BTI-TN5B1-4 cells, a cell line which has a high than mammalian cell lines where gene amplification usuintrinsic capacity for recombinant protein production but ally requires an extended period of time. Insect cells clumps severely in suspension reducing its effectiveness perform most of the post-translational modifications of as a host for foreign protein production with the baculovirus expression vector system. The efficacy of inducing mammalian cells, including glycosylation, and most of single-cell suspension correlated positively with the inthe proteins expressed retain biological function. crease in sulfation of the added polyanion. Unsulfated High levels of some recombinant proteins have been polyanions, neutral polymers, polycations, disaccharides, achieved, approaching the levels of the native polyheand monosaccharides were ineffective in inducing singledrin protein from the baculovirus (1000 mg/L). Howcell suspension. ever, expression of glycosylated, secreted proteins in Elimination of clumping in suspension culture by adding a dispersing agent can lead to enhanced recombinant the commonly used Spodoptera frugiperda cell lines SF9 protein production. Inducing single-cell suspension with and SF21 is much lower (Luckow, 1990). SF9 is a clonal dextran sulfate, a highly sulfated polyanion, resulted in isolate of SF21 but in general produces about the same a four-fold increase in volumetric yield of the recombinant levels of recombinant proteins (Davis et al., 1993; Hink glycosylated protein, human secreted alkaline phospha- et al., 1991;. Many secreted glycotase, and a two-fold increase in volumetric yield of the recombinant cytoplasmic protein, โค-galactosidase. High sylated proteins are produced in SF9 cells at levels below yields of 82 U/mL (ca. 110 mg/L) for alkaline phosphatase, 10 mg/L Steiner et al., 1988; Woj-and 705 U/mL (ca. 2.3 g/L) for โค-galactosidase under elechowski et al., 1987). vated oxygen have been obtained. The optimum volumet-Recently, an attachment-dependent cell line, Triric yield of alkaline phosphatase in BTI-TN5B1-4 dextran choplusia ni BTI-TN5B1-4 (hereafter referred to as sulfate cells under elevated oxygen but unsupplemented medium is 6 to 11-fold higher than attached cultures, and TN5B1-4), has been shown to be superior to SF9 for 3-fold higher than the best yield obtained for SF21 cells expression of both cytoplasmic and secreted glycosylin suspension at elevated oxygen and with nutrient supated proteins. TN5B1-4 optimally produced 7-fold more plementation. More importantly, cells can be infected at โค-galactosidase, 26-fold more human-secreted alkaline high density without complications from aggregation, phosphatase (SEAP), and 28-fold more soluble tissue which has important implications for scale-up.