Methods for purification of viruses

A method of purifying respiratory syncytial virus from virus-infected cells, wherein the method comprises:

• a) clarifying a viral harvest to form a clarified viral harvest, wherein clarifying comprises:
• i. filtering the viral harvest by direct flow filtration (DFF) through at least one clarification filter having a pore size of between about 3 micrometers to about 10 micrometers;
• ii. treating the viral harvest with a non-specific endonuclease;
• and
• iii. filtering the viral harvest by DFF through at least one clarification filter having a pore size of between about 0.45 micrometers to about 3 micrometers;
• b) stabilizing the clarified viral harvest with a stabilization buffer comprising sucrose, phosphate or Tris with NaCl salt or KCl salt to form a stabilized viral harvest;
• c) concentrating the stabilized viral harvest by tangential flow filtration (TFF) and performing buffer exchange by diafiltration (DF) using a hollow fiber cartridge with a molecular weight cut off (MWCO) of 500 kDa to form a concentrated viral harvest;
• and
• d) after (c), sterilizing the concentrated viral harvest by DFF through at least one clarification filter having a pore size of between about 0.8 micrometers to about 0.45 micrometers to form a sterilized viral harvest;
• whereby the respiratory syncytial virus is purified from the virus-infected cells and has a final viral infectivity titer of at least 5.7 log10 FFU/mL.