The vaccinia virus(vSC 8) expression system was employed for the production of β-galactosldase as a model heterologous protein. HeLa S3 cells were used as a host cell line for their higher production and scale-up potential. The β-galactosldase production could be substantially increased by increasing virus infectivity and host cell activity. The virus infectivity was determined by staining the producing cells using Xgal as substrate. When HeLa S3 cells were infected with 5MOI, the infectivity was usually 20-35%. As infection media, serum, polylysine concentration and buffers were tested for the investigation of the effects on virus infection. The optimal serum concentration and buffer were determined to be 1% of calf serum and HBSS, respectively. The virus infectivity and β-galactosldase production were increased only by 10% and 25% respectively when 2-25mg/L polylysine was added in DMEM containing 2.5% calf serum as infection medium. When HeLa S3 cells were treated with 0.0010.1μM of methotrexate for 24 hours prior to infection, the β-galactosldase production and specific productivity were increased by 2.5 -3 times, respectively.
