DEVELOPING AN IN VIVO BIOASSAY FOR EVALUATION OF G-CSF BIOLOGICAL POTENCY
Recombinant granulocyte-colony stimulating growth factor (G-CSF) is being widely used for the treatment of chemotherapy-induced neutropenia. The activity of recombinant G-CSF is regularly assessed using an in vitro bioassay based on the stimulation of leukemia cell proliferation. However, an accurate in vivo bioassay is also required to verify the efficiency of G-CSF in neutropenia treatment as well as to examine the response of the whole body to the recombinant protein. Therefore, in this study, we developed an in vivo bioassay for evaluating the biological potential of G-CSF using an immunosuppressed mouse model. We found that a single shot of 200 mg/kg cyclophosphamide was sufficient to induce immunosuppression in mice. The injection of G-CSF into the immunosuppressed mice at the dose of 5 µg/kg G-CSF was suitable to determine the biological activity of G-CSF. In addition, the daily multiple injections of 5 µg/kg G-CSF for 4 days in association with leukocyte counting for 7 days could be used to demonstrate the neutropenia treatment efficiency of recombinant G-CSF.