Inhibition of Interferon Alpha by a Peptide-Conjugated Phosphorodiamidate Morpholino Oligomer Increases Influenza Virus Replication in Chicken Embryo Fibroblast (DF-1) Cells; An Alternative Strategy to Increasing Vaccine Production in Cell Culture

Influenza is a global health issue causing substantial health and economic burdens in affected populations. Routine, annual vaccination for influenza virus is recommended for all persons older than 6 months of age. Propagation of influenza virus for vaccine production is predominantly through embryonated chicken eggs. Many challenges face propagation of the virus, including but not limited to low yields and lengthy production time. The development of a method to increasing vaccine production in eggs or cell lines by suppression of cellular gene expression would be helpful to overcome some of the challenges facing influenza vaccine production. Here we describe the use of a peptide-conjugated phosphorodiamidate morpholino oligomer (PPMO), an antisense molecule, to suppress protein expression of the host gene interferon alpha (INFα) in chicken embryo fibroblast (DF-1) cells. Suppression of INFα by PPMO resulted in significantly reduced levels of INFα protein in treated wells as measured by ELISA and was shown to not have any cytotoxicity to DF-1 cells at the effective concentrations tested. Treatment of the self-directing PPMO increased the ability of the influenza virus to replicate in DF-1 cells. Over a three-fold increase in viral production was observed in PPMO treated wells compared to those of untreated controls, which was observed to be independent of the initial viral input (MOI) studied. The use of PPMO would allow for cell cultures to produce increased levels of influenza for vaccine production or alternatively as a screening tool to cheaply test targets prior to development of permanent knockouts of host gene expression.