Apoptosis and Virus Infection

Programmed cell death is any process by which cells participate in their own death. Cell suicide programs are facilitated by the actions of gene products encoded by the cell destined to die. Insufficient or excessive cell death characterizes most human disease states, including virus infections. Perturbation of the cell can lead to activation of programmed cell death as a host defense mechanism to eliminate aberrant or damaged cells. Similarly, virus infection of a cell usually triggers the activation of programmed cell death. The ability of cells to recognize intruding viruses and to activate cell suicide provides an important host defense mechanism for eliminating viruses by eliminating virus-infected cells. However, viruses have developed myriad mechanisms to regulate cellular death processes. Consequently, many viruses cause disease primarily by inducing host cell death. There are nearly as many strategies by which viruses interface with the cell death/survival machinery of host cells as there are viruses, from initial recognition of a virus to the ultimate proteolytic dismantling of the cell by proteases. Common themes uncovered through the study of virus-modulated cell death have proved to be broadly applicable to biology as well as to the study of virus infection, pathogenesis, and evolution.