Ineffectual immunity in a resurrected mouse model of persistent viremia

Viruses that infect a host over long periods of time have evolved unique strategies to evade the host immune system. Of particular interest are viruses that cause persistent infection in the laboratory mouse-the most well-developed tool for studying the mammalian immune system. Here, we resurrected a model of persistent RNA virus infection (lactate dehydrogenase-elevating virus, LDV) and applied modern tools of mouse immunology to further characterize its persistence. We found that host factors that typically have a dramatic effect on viral infections-e.g., the interferon system and lymphocytes-had very little impact on LDV infection. Removing "checks" on immune activation also had little effect on the virus or host health. Altogether, these findings imply that LDV uses a unique and highly effective mechanism to avoid immune clearance. Understanding this mechanism has implications for understanding ways in which the immune system fails.