CCR1 Deficiency Increases Susceptibility to Fatal Coronavirus Infection of the Central Nervous System

Abstract

The role of CC chemokine receptor 1 (CCR1) in host defense and disease development was determined in a model of viral-induced neurologic disease. Intracerebral (IC) infection of mice with mouse hepatitis virus (MHV) results in an acute encephalitis followed by a chronic demyelinating disease similar in pathology to the disease multiple sclerosis (MS). No increase in mortality was observed during the acute phase of disease following MHV infection of mice lacking CCR1 (CCR1-/-) as compared to wild-type (CCR1+/+) mice. However, by 21 d post-infection, 74% of CCR1-/- mice had succumbed to death compared to only 32% mortality of CCR1+/+ mice, indicating that chemokine signaling through CCR1 significantly (p <or= 0.04) enhanced survival following IC infection with MHV. Increased mortality in CCR1-/- mice was not associated with increased viral recovery from the CNS, although CCR1 deficiency correlated with reduced T-cell accumulation within the CNS during acute, but not chronic, disease. Despite the reduction in T-cell trafficking into the CNS of CCR1-/- mice during acute disease, components of host defense remained unaltered; T-cell effector functions including cytolytic activity and proliferation and the expression of IFN-gamma within the CNS were not significantly different between CCR1+/+ and CCR1-/- infected mice. In addition, macrophage infiltration into the CNS was unaffected in MHV-infected CCR1-/- mice when compared to CCR1+/+ mice. Furthermore, assessment of neuropathology revealed no difference in the severity of demyelination between CCR1-deficient and wild-type mice. Together, these findings reveal that T-cell and macrophage trafficking are not dependent on CCR1 and highlight an important role for CCR1 signaling in promoting survival during chronic MHV infection.