EFFECTS OF LONG-TERM PASSAGING OF BTI-TN5B1-4 INSECT CELLS ON GROWTH AND RECOMBINANT PROTEIN-PRODUCTION

The BTI-Tn-5B1-4 insect cell line from Trichopulsi ni has enabled bett er secretion and higher productivity of recombinant proteins in the ba culovirus expression system. An early passage stock of this cell line is compared here to the commercially available ''High Five'' cell line stock. The early passage Tn5B1-4 cells grew to over 11 x 10(6) cells/ mL and expressed 2.5-fold more recombinant secreted alkaline phosphata se (SEAP) than the High Five cells. While the specific productivity on a cell number basis was only slightly higher, the early passage Tn5B1 -4 cells maintained this productivity at higher cell densities, increa sing their volumetric productivity to 50 mu g/mL under elevated oxygen conditions. We propose that the difference in these two stocks of cel ls is the length of time they have been cultured, 130 total passages f or the early passage versus 360 passages for the High Five cells. This conclusion is supported by the facts that the early passage Tn5B1-4 c ells are smaller in diameter by 4 mu m, smaller in cellular protein co ntent (206 versus 270 mu g of protein/10(6) cells), have an increased propensity to clump in suspension culture, and are less susceptible to dispersion of these clumps by dextran sulfate compared to the High Fi ve cells.