DNA damage and mutagenesis: is it an issue for swine flu?

In virology, many pathogenic viruses can induce DNA damage and can cause mutagenesis. Here, the author would like to discuss on swine fl u virus, a novel H1N1 infl uenza virus that causes worldwide emerging viral infection at present. As a viral infection, the induction of DNA damage might be expected in the case of swine fl u. Indeed, several viruses can cause DNA damage and this might lead to cell death or cellular abnormalities. In the case of classical H1N1 infl uenza virus, there are some publications on its induction of DNA damage. Similar to other viral infections, the DNA damage in infl uenza infection is believed to be due to free radical species and nitric oxide (NO) or its derivatives. The DNA damage due to infl uenza virus infection is believed to relate to apoptosis. However, the exact cellular pathways involved in infl uenza virus induced apoptosis are presently ill defi ned. Uchide et al. reported that typical apoptosis induced by infl uenza virus could be observed in human cell culture and was characterized by DNA ladder formation. In addition, fragmentation of nuclei and chromatin condensation can be observed. Recently, it was reported that this DNA ladder formation could be reduced by supplementation of antioxidative substances. DNA damage and apoptosis caused by infl uenza virus seems to be controlled by the antioxidative system. Focusing on the novel swine fl u, there is no report on DNA damage. However, there is an interesting report on activation of the intrinsic mitochondrial apoptotic pathway in classical swine infl uenza virus. Choi et. al noted that classical swine infl uenza infection increased the cellular levels of TAJ, an activator of the JNKstressing pathway, and the c-Jun protein. Thus, it might be assumed that classical swine infl uenza virus induce apoptosis via the mitochondrial pathway. Nevertheless, there is also no exact study to assess the mutagenesis property of swine fl u virus. Indeed, mutant in infl uenza is widely mentioned however limited reports could be seen on its mutagenesis property.