Perfusion filtration systems

1. A method of filtering a cell culture media comprising passing a cell culture media comprising mammalian cells at a viable cell density of at least 10×10 6 cells per mL and a virus through a plurality of tubular porous membranes of a filter element enclosed within a casing,

wherein each tubular porous membrane filter element comprises a plurality of tubular porous membranes, wherein at least 95% of the pores in each of the plurality of tubular porous membranes are between 5 μm and 15 μm in size and wherein the internal diameter of each of the plurality of tubular porous membranes is between about 1 mm to about 10 mm,

wherein the mammalian cells are retained within the tubular porous membranes and a permeate comprising the virus flows through the pores of the tubular porous membranes into the casing.

2. The method of claim 1 , wherein at least 99% of the pores in each of the plurality of tubular porous membranes are between 5 μm and 15 μm in size.

3. The method of claim 1 , wherein at least 95% of the pores in each of the plurality of tubular porous membranes are between of 7 μm and 12 μm in size.

4. The method of claim 1 , wherein the internal diameter of each of the plurality of tubular porous membranes is between about 1 mm and about 5 mm.

5. The method of claim 1 , wherein the virus is a lentivirus, an adeno-associated virus (AAV), and/or an influenza virus.

6. The method of claim 1 , wherein the casing has an internal diameter of about 1 to about 30 CM.

7. The method of claim 1 , wherein the plurality of tubular porous membranes comprises at least 9 tubular porous membranes.

8. The method of claim 1 , wherein the method is a tangential flow filtration perfusion method or an alternating tangential flow perfusion method.

9. The method of claim 1 , wherein the virus is a lentivirus.

10. The method of claim 1 , wherein the mammalian cells are at a viable cell density of at least 20×10 6 cells per mL.

11. The method of claim 1 , wherein the mammalian cells are at a viable cell density of at least 40×10 6 cells per mL.

12. The method of claim 1 , wherein the mammalian cells are at a viable cell density of at least 50×10 6 cells per mL.

13. The method of claim 1 , wherein the mammalian cells are at a viable cell density of at least 60×10 6 cells per mL.

14. The method of claim 1 , wherein the mammalian cells are at a viable cell density of at least 70×10 6 cells per mL.

15. The method of claim 1 , further comprising performing an affinity chromatography step on the permeate comprising the virus.

16. The method of claim 1 , further comprising performing an hydrophobic interaction chromatography step on the permeate comprising the virus.

17. The method of claim 1 , wherein the mammalian cells have a viability of at least 90%.

18. The method of claim 1 , wherein the mammalian cells have a viability of at least 95%.

19. The method of claim 14 , wherein the method is a tangential flow filtration perfusion method or an alternating tangential flow perfusion method.

20. The method of claim 15 , wherein the method is a tangential flow filtration perfusion method or an alternating tangential flow perfusion method.