Role of virus-induced apoptosis in a host defense mechanism against virus infection.

Many animal viruses are known to induce apoptosis in infected cells. This virus-induced apoptosis has been often described as a mechanism of host defense against virus infection, based on the finding that mutants of an insect virus with the ability to induce extensive apoptosis in some cells cannot grow in the same cells. In animal virus infection, we have shown that (1) viruses can somehow overcome this defense mechanism and that (2) virus multiplication in the apoptotic cells is not as completely suppressed as in the insect virus infection. These results suggest that, in the case of animal viruses, the virus-induced apoptosis does not play the same role in the host defense system as in insect cells. However, by examining the virus infection under the conditions comparable to the infection in vivo, we demonstrated the defensive role of apoptosis in animal virus infection.