Detection of influenza virus induced ultrastructural changes and DNA damage

The influenza virus generally causes damage to epithelial cells of respiratory tract and infection of cells with this virus often results in cell death with apoptotic characteristics. Reports are available implicating influenza virus as a causative agent of chromosomal aberrations in cells and culture. The objective of this study was to analyze the process of cell death caused by influenza virus (A/Udorn/317/72, H3N2) infection in cultured HeLa cells by electron microscopy and comet assay. The apoptotic study was performed using light microscopy electron microscopy and comet assay to observe the changes in cell morphology and DNA fragmentation. HeLa cells, infected with influenza virus were harvested at various time periods to observe the ultrastructural changes. This infection gave rise to nuclear fragmentation and chromatin condensation accompanied by chromosomal DNA fragmentation into oligonucleosomes. The pattern of comet assay revealed that the apoptosis occurred due to fragmentation of the DNA of the cells which reached the maximum level at 36 h post infection. Ultrastructural study showed extensive chromatin condensation and nuclear fragmentation which are the characteristic features of apoptosis.