Coussens, P. M., Smith, K. A., Weber, P. S., & Colvin, C. J. (2011). Immortalized chick embryo cell line adapted to serum-free growth conditions and capable of replicating human and reassortant H5N1 influenza strains for vaccine production. Vaccine, 29(47), 8661-8668.
doi: 10.1016/j.vaccine.2011.08.122.

In this study, an immortalized chick embryo cell line was established, termed PBS-12SF, which is adapted toserum-free serum free conditions, and is capable of replicating human and reassortant H5N1 influenza strains to high titers. In many cases, PBS-12SF cells produced higher growth titers of influenza virus than those of primary chick embryo kidney (CEK) cells, Madin-Darby Canine Kidney (MDCK) cells and African green monkey kidney cells (Vero). Additionally, in PBS-12SF cell cultures, influenza virus is released into the culture fluid without need for exogenous proteases, which can simplify downstream processing for vaccine production.

The serum-free medium, OptiPRO SFM, is a commercially available product. The precise formulation is proprietary.