INTRACEREBRAL TARGETS AND IMMUNOMODULATION OF MURINE LISTERIA-MONOCYTOGENES MENINGOENCEPHALITIS

In humans, infection with Listeria monocytogenes (L. monocytogenes) ca n severely affect the central nervous system (CNS). In the present stu dy we have employed a murine model of CNS listeriosis to characterize the intracerebral distribution of L. monocytogenes. Following intracer ebral application of a low dose of L. monocytogenes (serovar 1/2a, EGD strain) a severe fatal leptomeningitis, ventriculitis, and encephalit is developed. Listeria were detectable both intracellularly in differe nt cell types of the CNS and extracellularly in the cerebrospinal flui d. Ultrastructural analysis revealed macrophages, granulocytes, plexus epithelial cells, ependymal cells, and neurons as target cells. An in flammatory reaction with macrophages and granulocytes developed in the brains of these animals but was not sufficient to prevent the fatal o utcome of the disease. However, active immunization of mice prior to a n intracerebral challenge infection significantly reduced the mortalit y. Immunized animals showed an early recruitment of a significant numb er of CD8(+) and, to a lesser degree, CD4(+) T cells within 24 hours p .i. as well as a strong activation of microglial cells and macrophages . These findings may provide an interesting model for studies on the p athogenesis of cerebral listeriosis.