Specific antibody productivity of transfectoma during long-term culture and under hyperosmotic stress

Abstract

To design the scheme of large-scale production of chimeric antibody for the post-exposure prophylaxis of hepatitis B virus (HBV) infection, the stability of transfectomas (H69K-1 and 6-31) regarding antibody production was examined during a long-term, repeated-fed batch culture without selection pressure using antibiotics. Although H69K-1 transfectoma was more stable than 6-31 transfectoma, both transfectomas displayed gradual decrease in specific antibody productivity ($q_Ab$) for the first several weeks of cultivations. During this period, $q_Ab$ was decreased by 40-50%. This loss of $q_Ab$ was mainly due to the appearance of a nonproducing population of transfectoma (NP) which was monitored throughout the culture by flow cytometry and limiting dilution method. However, an NP did not overtake the culture and were balanced with a producing population of transfectoma (P), resulting in stable antibody production. The subclones of NP obtained at the end of long-term culture were further characterized by reverse transcription-polymerase chain reaction assay of the heavy and light chain mRNA. All the subclones of NP derived from H69K-1 transfectoma had only light chain mRNA. On the other hand, an NP in 6-31 transfectoma culture was heterogeneous. Some subclones of NP derived from 6-31 transfectoma had only heavy chain mRNA and other subclones had only light chain mRNA. Taken together, the results obtained here suggest that selection pressure is necessary for a long-term, continuous culture, because stable antibody production in a long-term culture was achieved only after a significant loss of antibody productivity. Accordingly, a batch culture appears to be more appropriate for a large-scale chimeric antibody production without selection pressure. In the flow cytometric analysis of the stability of antibody-producing cells, fluorescent antibody probes specific for immunoglobulin heavy chains have been widely utilized to quantify intracellular antibodies. To investi...