Recall proliferation potential of memory CD8+ T cells and antiviral protection.

Memory CD8+ T cells play a crucial role in mediating protection from infection with viruses and other intracellular pathogens. Memory T cells are not a homogenous cellular population and may be separated into central memory T cells with substantial recall proliferation capacity and effector memory T cells with limited recall proliferation capacity. It has been suggested that the protective capacity of effector memory T cells is more limited than that of central memory T cells in viral infections. Here, we show that pronounced recall proliferation potential is indeed key for protection against lymphocytic choriomeningitis virus, which replicates in central lymphoid organs and is controlled by contact-dependent lysis of infected cells. In contrast, recall proliferation competence is not sufficient for protection against vaccinia virus, which is replicating in peripheral solid organs and is controlled by cytokines. To protect against vaccinia virus, high numbers of effector-like T cells were required to be present in peripheral tissue before viral challenge. These data indicate that the protective capacity of different subpopulations of memory T cells may vary dependent on the nature and the route of the challenge infection, which must be considered in T cell-based vaccine design.