Enhanced production of human influenza virus in PBS-12SF cells with a reduced interferon response.

Influenza is one of the most important infectious diseases in humans. The best way to prevent severe illness caused by influenza infection is vaccination. Cell culture-derived influenza vaccines are being considered in addition to the widely used egg-based system in order to support the increasing seasonal demand and to be prepared in case of a pandemic. Cell culture based systems offer increased safety, capacity, and flexibility with reduced downstream processing relative to embryonated eggs. We have previously reported a chick embryo cell line, termed PBS-12SF, that supports replication of human and avian influenza A viruses to high titers (>10(7) PFU/ml) without the need for exogenous proteases or serum proteins. Viral infections in cells are limited by the Interferon (IFN) response typified by production of type I IFNs that bind to the IFNα/β receptor and activate an antiviral state. In this study, we investigated how neutralizing the interferon (IFN) response in PBS-12SF cells, via shRNA-mediated knock-down of IFNAR1 mRNA expression, affects influenza virus production. We were successful in knocking down ∼90% of IFNAR1 protein expression by this method, resulting in a significant decrease in the response to recombinant chIFNα stimulation in PBS-12SF cells as shown by a reduction in expression of interferon-responsive genes when compared to control cells. Additionally; IFNAR1-knock-down cells displayed enhanced viral HA production and released more virus into cell culture supernatants than parental PBS-12SF cells.