Production of mouse interferon with high titers in a large-scale suspension culture system.

Abstract

ABSTRACT L-MS cells, adapted to grow in suspension, were obtained by selection from a high interferon (IF)-producing line of mouse L cell monolayers. A large volume of L-MS cells (20 liters or more; 1-2 †~ 101° cells) was readily grown in a spinner culture, retaining their ability to produce high yields of IF in serum-free medium following induction with Newcastle disease virus (NDV). The optimal condition for the production of IF in the suspension culture of L-MS cells was established. The system also proved itself to be susceptible to IF induction by polyinosinic-polycytidylic acid (Poly I †E Poly C) and by NDV inactivated with ultraviolet light (NDV-UV). By employing the present system, large quantities of mouse IF of a high titer could be routinely prepared. Recent improvements in suspension culture techniques have enabled us to grow mam- malian cell lines in a large-scale system. These culture systems seem to be suitable for preparing large quantities of cells or cell products. However, in production and preparation of interferon (IF) from cultured cells, the monolayer culture system has been widely used, although it does not appear to be suitable for handling and growing a large volume of cells. Earlier, Cantell and Pau- cker [2] reported the production and release of mouse IF in L cells grown in suspension after induction with Newcastle disease virus (NDV), but the titer was very low. Later, there have been only a few reports [5, 13] on the suspension culture system of mammalian cells for IF production except that of human leukocytes [6, 16]. Graff et al [5] prepared. NDV-induced IFfrom L-929 cells propa- gated in a relatively large-scale suspension system. Their system was a dialysis cultureusing a special cytogenerator, and the IF titer obtained fluctuated within a wide range. Mogensen et al [13] reported that mouse LS cells, adapted to grow in a protein-free medium [1], produced both Poly I - Poly C-and NDV-UV-induced IF in a spinner culture system, but the titers obtained were still very low as compared with other mouse IF produced in the monolayer system [9, 14]. Nevertheless, the system offered several technical advantages and suggested a possi-bility of producing large quantities of IF with high-specific activities. The LS cells used may have been a low IF producer. Alter- natively, the adaptation of the cells to growth in suspension may have caused an alteration in the IF-producing ability. Using a spinner culture technique intro-duced by Eagle [3] and Salzman [15], we have adapted a high IF-producing line of mouse L cells to grow stably in a large-scale suspension, which could yield large quantities of mouse IF in a suspension system. This paper details conditions for the production of a high-titered IF in the system. MATERIALS AND METHODS Cells and media. L-MS cells, adapted to grow in suspension, were derived from a high