EVALUATION OF THE SERUM-FREE MEDIUM MDSS2 FOR THE PRODUCTION OF POLIOVIRUS ON VERO CELLS IN BIOREACTORS

The serum-free medium MDSS2 (Merten et al., 1994), was used for cultiv ating Vero cells as well as for producing poliovirus (Sabin type 1) in static and in perfused microcarrier cultures. At slightly different g rowth rates of 0.0120/h and 0.0106/h, respectively, static cultures in serum-containing (SCM) and serum-free (SFM) medium produced titers of 10(6.75) and 10(6.67) TCID50 per 50 mu l; signifying a specific produ ctivity of 0.89 and 1.07 TCID50/c. Serum-free bioreactor cultures of V ero cells on DEAE-dextran microcarriers at 6.25 g/l produced cell dens ities of about 1.5 x 10(6)c/ml. After infection with virus (multiplici ty of infection (MOI) 0.1-0.3) titers of about 6.3 x 10(8) TCID50/ml w ere obtained, signifying an average specific productivity of 7.1 TCID5 0/c.h. Although these values were 4 and 2 fold, respectively, higher t han in classical resum-based production processes (Montagnon et al., 1 981), a reference culture, for which cell growth was done in SCM and o nly virus production was done in SFM, produced 2 x 10(9) TCID/ml with an average specific virus production rate of 18.9 TCID50/c.h. The diff erences between the fully serum-free and our reference process were ma inly due to physiological differences of cells grown in SCM and SFM an d also due to strongly modified consumption kinetics after virus infec tion leading to limitations of one or several essential medium compoun ds, like glucose and amino acids. Avoiding these limitations by increa sing the residual concentration of glucose, glutamine, histidine, and SH-amino acids, led to specific virus production rates (of about 17.9 TCID50/c.h.) comparable to those found in the reference virus producti on process. The optimisation of the production of the poliovirus (Sabi n 1) will be described with respect to the modification of the medium composition.