Abstract: A serum-free suspension culture Marc-145 cell line was established through domestication, and the effects of domestication on cell characteristics were analyzed to provide basis for mass production of host cells for vaccines. The serum concentration in the slow drop culture medium was used to subculture for 50 generations, and the serum-free medium was used for suspension culture and domestication. The morphology, doubling time, growth curve and sensitivity to PRRSV of P10, P20, P30, P40 and P50 passage cells during passage and domestication were compared and analyzed. Results showed that Marc-145 cells grew like flat polygons. The doubling time of P10 passage cells was 34.15 h, while the doubling time of P50 passage cells was 36.16 h, and the doubling time of P50 passage cells was slightly prolonged, but the difference was not significant. The growth curves of P10, P20, P30, P40 and P50 Marc-145 cells were “S” type, and the chromosome numbers of P10 and P50 passage cells were between 88 and 90. After inoculating the virus, there was no significant difference in TCID₅₀ values between P10, P20, P30, P40 and P50 cells, indicating that there were no significant change in cell characteristics after 50 generations of cell passage. Therefore, P50 cells were cultured and domesticated in serum-free suspension culture. After 48 h of serum-free suspension culture, the cell density of P50 cells reached 4.14×10⁶ mL^-1.

Key words: Marc-145, serum-free acclimation, passage characteristics