Influenza a virus induced apoptosis: inhibition of DNA laddering & caspase-3 activity by zinc supplementation in cultured HeLa cells.

BACKGROUND & OBJECTIVE The pathogenesis of influenza virus infection involves virus replication in epithelial cells of the respiratory tract and the consequent degeneration of infected cells. Influenza virus induces cellular degeneration following infection of cultured cells in vitro, and the cytopathic effect (CPE) occurs principally through apoptotic cell death. This study was undertaken to fi nd out the effect of zinc on influenza virus induced apoptosis in cultured HeLa cells. METHODS The sub-confluent monolayer HeLa cells were used to study the effect of zinc on influenza virus induced apoptosis. The apoptotic markers viz., caspase-3 activity, phagocytic index, morphological changes, and DNA fragmentation were assayed. RESULTS When HeLa cells were infected with a cell adapted pathogenic strain of influenza A (A/Udorn/ 317/72H(3)N(2)) virus, DNA fragmentation was observed in virus infected cells by 24 h post infection and caspase-3 activity was maximum at 4 h post infection after which it reached to plateau. Treatment of cells with 0.1 5mM concentration of zinc till 8 h post infection inhibited DNA fragmentation and also caspase 3 activity was decreased significantly up to 2 h post infection. INTERPRETATION & CONCLUSION When the infected HeLa cells were incubated with adherent macrophages, efficient phagocytosis occurred and the release of virus into the culture medium was inhibited. These results suggested that inhibitory effect on influenza virus induced apoptotic death of cultured cells can be determined at an early stage of the infection by treatment of zinc.