Contamination with adventitious viruses is controlled by using well characterized cell lines and qualified raw materials and consumables that have been demonstrated to be free of contaminants.  The final product is also tested for the presence of adventitious viruses. Bacterial/microbial contamination of the Lentiviral  product is controlled by using closed systems and sterile single-use consumables whenever possible. Aseptic technique for all operations should be used wherever possible. Finally, the downstream unit operations, including first clarification through a 0.5 µm filter and finally sterile filtration with a 0.2 µm filter ensure sterility of the final product. Additionally in-process samples for bioburden and endotoxin are taken at bulk harvest and following other downstream unit operations, and the final product is also tested for sterility and endotoxin.