A highly cytopathogenic influenza C virus variant induces apoptosis in cell culture.

An influenza C virus variant, C/AA-cyt, was identified as the agent responsible for highly effective induction of cytopathogenicity in MDCK cells. The cytopathogenic effect was manifested by cell rounding, cell shrinkage and foci of cell destruction leading finally to disruption of the monolayer in a virus dose-dependent manner. Virus-induced cytopathogenicity was suppressed by temperatures nonpermissive for virus replication. Maintenance of plasma membrane integrity post-infection, in connection with induction of a DNA fragmentation ladder, revealed the characteristic picture of apoptosis. In support of this, quantitative analysis demonstrated high levels of apoptosis-like oligonucleosomal DNA. The results indicate that influenza C viruses can induce programmed cell death, as formerly reported for influenza type A and B viruses.