Method for large-scale production of lentivirus by using GMP-level serum-free suspension cells

1. A method for producing lentivirus using serum-free suspension cells, which comprises the steps of:

(a) providing a seed solution of packaging cells for the production of lentivirus, wherein the packaging cells are packaging cells that grow in suspension;

(b) inoculating the seed solution in a first culture medium placed in a culture container to obtain a first culture, wherein the first culture medium is a serum-free cell culture medium, and the inoculation density is 1×10 6 -5×10 6 cells/ml, and the volume of the first culture medium is 3-100 liters;

(c) carrying out subculture of the packaging cells of the first culture, wherein the subculture conditions are set at a temperature of 30-38° C., a dissolved oxygen concentration of 35-55%, a CO 2 concentration of 2-10% and a pH of 6.9-7.4, and monitoring the real-time pH value of the first culture during the subculture process, and controlling dissolved oxygen and/or CO 2 concentrations based on the real-time pH value to maintain the pH between 6.9-7.4;

(d) starting a liquid change operation when liquid change trigger conditions are met,

wherein the liquid change trigger conditions comprise:

(s1) the real-time pH is ≤6.9 or ≤7.0 or ≤7.05;

(s2) the real-time pH value is still showing a downward trend by adjusting the concentration of oxygen, air, nitrogen and/or CO 2 ; and

(s3) the subculture time is ≥72 hours;

wherein, the liquid change operation comprises: discharging the cell-free supernatant in the culture from the culture container, wherein the volume of the culture before discharging the supernatant is Vq1, while the volume of the culture after discharging the supernatant is Vh1, and the ratio of Vq1/Vh1 is 3-15; then, adding the culture medium to the culture container to form a packaging cell culture;

(e) repeating steps (c) and (d) n times, wherein n is 1, 2, or 3;

(f) starting a transfection operation when transfection trigger conditions are met,

wherein, the transfection trigger conditions comprise:

(t1) the total number of cells is 0.05-2×10 11 cells;

(t2) the cell density is 0.5-5×10 6 cells/ml;

(t3) the cell viability rate is ≥90%; and

(t4) the total culture time is ≥72 hours;

wherein, the transfection operation comprises: mixing a production plasmid used for producing the lentivirus with a transfection reagent, and adding the mixture to the culture container for introduction to the packaging cells to form transfected packaging cells;

(g) optionally carrying out post-transfection liquid change;

(h) culturing the transfected packaging cells, wherein the culture conditions are set at a temperature of 30-37° C., a dissolved oxygen concentration of 35-55%, a CO 2 concentration of 2-10% and a pH of 6.9-7.4, and monitoring the real-time pH value of the first culture during the subculture process, and controlling dissolved oxygen and/or CO 2 concentrations based on the real-time pH value to maintain the pH between 6.9-7.4;

(i) starting a harvest and liquid change operation when liquid change trigger conditions are met,

wherein the liquid change trigger conditions comprise:

(s1) the real-time pH is ≤6.9;

(s2) the real-time pH value is still decreasing by adjusting the concentration of oxygen, air, nitrogen and/or CO 2 ; and

(s3) the subculture time is ≥72 hours;

wherein the liquid change operation comprises: recovering the cell-free virus-containing feed liquid from the culture, wherein the volume of the culture before recovering the feed liquid is Vq2, while the volume of the culture after recovering of the supernatant is Vh2, and the ratio of Vq2/Vh2 is 3-15;

(j) repeating steps (h) and (i) m times, wherein m is 1, 2, or 3, and before repeating, adding culture medium to the culture container to form a transfected cell culture;

(k) mixing the recovered liquids from each recovery to obtain a combined virus-containing supernatant; and

(l) purifying the mixed virus-containing supernatant to obtain a purified lentiviral vector;

wherein, the culture medium used in all the above steps is a serum-free cell culture medium.

2. The method of claim 1 , wherein in step (c) and/or (h), the culture is performed under a shaking condition.

3. The method of claim 1 , wherein in step (c) and/or (h), the pH is maintained between 7.0 and 7.35.

4. The method of claim 1 , wherein in step (d) and/or (i), the ratio of Vq1/Vh1 is 5-10.

5. The method of claim 1 , wherein the total time of steps (c), (d) and (e) is 72-216 hours.

6. The method of claim 1 , wherein in step (f), the multi-plasmid transfection comprises three-plasmid transfection and four-plasmid transfection.

7. The method of claim 1 , wherein the culture container is a disposable culture container.

8. The method of claim 1 , wherein the total number of viruses contained in the mixed virus-containing supernatant is 1×10 12 Tu.

9. The method of claim 1 , wherein the packaging cells are human embryonic kidney epithelial cells.

10. The method of claim 1 , wherein in step (1), the purification comprises: ultrafiltration and chromatography.