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Objective@#To investigate the best amount of TPCK trypsin in Madin Darby canine kidney (MDCK) cell suspension for the culture of H7N9 avian influenza virus.@*Methods@#Different concentrations of TPCK trypsin were added during the periods of cell growth and virus production. Their effects on cell growth, viability, glucose and lactate metabolism, and hemagglutination titer were monitored every 12 h. Inter-batch differences were analyzed. The amount of trypsin added in the cell growth phase was 0, 1 μg/ml, 2 μg/ml, 4 μg/ml, 6 μg/ml, 8 μg/ml, 10 μg/ml and 15 μg/ml. The amount of trypsin added during the virus production period was 0, 0.5 μg/ml, 1 μg/ml, 1.5 μg/ml, 2 μg/ml and 2.5 μg/ml. When the hemagglutination titers were same, the adding amount was further optimized at different multiplicity of infection (MOI) of 0.001, 0.005, 0.025 and 0.05.@*Results@#No significant linear effects of TPCK trypsin concentration on cell number, viability, and glucose and lactate metabolism were observed. No toxicity to cell growth was observed when TPCK trypsin concentration reached 15 μg/ml. After the inoculation of H7N9 avian influenza virus, the hemagglutination titers in the 1 μg/ml, 1.5 μg/ml, 2 μg/ml and 2.5 μg/ml TPCK trypsin groups reached the peaks at 48 h, which were 1∶26.5. At 60 h, the hemagglutination titers of the latter two groups decreased faster than those of the former two groups. When the MOI was 0.005, the hemagglutination titer of the 1.5 μg/ml group at 48 h was 26.5 higher than 26 in the 1 μg/ml group under the same condition. There were differences between different batches of TPCK trypsin.@*Conclusions@#Adding 1 μg/ml and 1.5 μg/ml of trypsin could better promote the proliferation of H7N9 avian influenza virus, and 1.5 μg/ml of trypsin had a wider range of MOI applicability.
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Objective To reduce the residual proteins and DNA of host cells in the preparation of H5N1 influenza A virus. Methods Core 700 was firstly used to remove residual host cell proteins, and then Capto Q was used to remove host cell DNA. Several batches of H5N1 influenza A virus cultured in Ma-din-Darby canine kidney ( MDCK) cells were purified using this method. The efficiency of purification was evaluated using many methods including quantitative real-time PCR, hemagglutination ( HA) test and single radial immunodiffusion assay. Moreover, Benzonase nuclease was used for comparison. Results Without the use of Benzonase nuclease, the overall removal rates of host cell DNA and residual proteins were 99. 62％ and 98. 1％, and the HA antigen recovery rate was 66. 96％. Conclusions This study established a purification strategy with good effect for cell-based influenza vaccines. It can efficiently remove host cell DNA and proteins and achieve a high HA recovery rate. The purification result is no worse than that of adding Benzonase nuclease, suggesting the potential of its application in actual vaccine production.
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Objective@#To reduce the residual proteins and DNA of host cells in the preparation of H5N1 influenza A virus.@*Methods@#Core 700 was firstly used to remove residual host cell proteins, and then Capto Q was used to remove host cell DNA. Several batches of H5N1 influenza A virus cultured in Madin-Darby canine kidney (MDCK) cells were purified using this method. The efficiency of purification was evaluated using many methods including quantitative real-time PCR, hemagglutination (HA) test and single radial immunodiffusion assay. Moreover, Benzonase nuclease was used for comparison.@*Results@#Without the use of Benzonase nuclease, the overall removal rates of host cell DNA and residual proteins were 99.62% and 98.1%, and the HA antigen recovery rate was 66.96%.@*Conclusions@#This study established a purification strategy with good effect for cell-based influenza vaccines. It can efficiently remove host cell DNA and proteins and achieve a high HA recovery rate. The purification result is no worse than that of adding Benzonase nuclease, suggesting the potential of its application in actual vaccine production.