Experimental murine herpes simplex virus (HSV)-1 brain infection stimulates microglial cell-driven proinflammatory chemokine production which precedes the presence of brain-infiltrating systemic immune cells. In the present study, we investigated the phenotypes and infiltration kinetics of leukocyte trafficking into HSV-infected murine brains. Using real-time bioluminescence imaging, the infiltration of luciferase-positive splenocytes, transferred via tail vein injection into the brains of HSV-infected animals, was followed over an 18-day time course. Flow cytometric analysis of brain-infiltrating leukocytes at 5, 8, 14, and 30 days postinfection (d.p.i.), was performed to assess their phenotype. A predominantly macrophage (CD45highCD11b+Ly6Chigh) and neutrophil (CD45highCD11b+Ly6G+) infiltration was seen early during infection, with elevated levels of TNF-α mRNA expression. By 14 d.p.i., the phenotypic profile shifted to a predominantly lymphocytic (CD45highCD3+) infiltrate. This lymphocyte infiltrate was detected until 30 d.p.i., when infectious virus could not be recovered, with CD8+ and CD4+ T cells present at a 3:1 ratio, respectively. This T lymphocyte infiltration paralleled increased IFN-γ mRNA expression in the brain. Activation of resident microglia (CD45intCD11b+) was also detected until 30 d.p.i., as assessed by MHC class II expression. Activated microglial cells were further identified as the predominant source of IL-1β. In addition, infected mice given primed immunocytes at 4 d.p.i. showed a significant increase in mortality. Taken together, these results demonstrate that intranasal infection results in early macrophage and neutrophil infiltration into the brain followed by prolonged microglial activation and T lymphocyte retention. Similar prolonged neuroimmune activation may contribute to the neuropathological sequelae observed in herpes encephalitis patients.

Immunoglobulin in cerebral spinal fluid and antibody secreting cells (ASC) within the central nervous system (CNS) parenchyma are common hallmarks of microbial infections and autoimmune disorders. However, the signals directing ASC migration into the inflamed CNS are poorly characterized. This study demonstrates that CXCR3 mediates CNS accumulation of ASC during neurotropic coronavirus-induced encephalomyelitis. Expansion of CXCR3-expressing ASC in draining lymph nodes prior to accumulation within the CNS was consistent with their recruitment by sustained expression of CXCR3 ligands during viral persistence. Both total and virus-specific ASC were reduced greater than 80% in the CNS of infected CXCR3 ؊/؊ mice. Similar T cell CNS recruitment and local T cell-dependent antiviral activity further indicated that the ASC migration defect was T cell independent. Furthermore, in contrast to the reduction of ASC in the CNS, neither virus-specific ASC trafficking to bone marrow nor antiviral serum antibody was reduced relative to levels in control mice. Impaired ASC recruitment into the CNS of infected CXCR3 ؊/؊ mice coincided with elevated levels of persisting viral RNA, sustained infectious virus, increased clinical disease, and mortality. These results demonstrate that CXCR3 ligands are indispensable for recruitment of activated ASC into the inflamed CNS and highlight their local protective role during persistent infection.

Central nervous system (CNS) infections and autoimmune inflammatory disorders are often associated with retention of antibody-secreting cells (ASC). Although beneficial or detrimental contributions of ASC to CNS diseases remain to be defined, virus-specific ASC are crucial in controlling persistent CNS infection following coronavirus-induced encephalomyelitis. This report characterizes expression kinetics of factors associated with ASC homing, differentiation, and survival in the spinal cord, the prominent site of coronavirus persistence. Infection induced a vast, gamma interferon (IFN-␥)-dependent, prolonged increase in chemokine (C-X-C motif) ligand 9 (CXCL9), CXCL10, and CXCL11 mRNA, supporting a role for chemokine (C-X-C motif) receptor 3 (CXCR3)-mediated ASC recruitment. Similarly, CD4 T cell-secreted interleukin-21, a critical regulator of both peripheral activated B cells and CD8 T cells, was sustained during viral persistence. The ASC survival factors B cell-activating factor of the tumor necrosis factor (TNF) family (BAFF) and a proliferatinginducing ligand (APRIL) were also significantly elevated in the infected CNS, albeit delayed relative to the chemokines. Unlike IFN-␥-dependent BAFF upregulation, APRIL induction was IFN-␥ independent. Moreover, both APRIL and BAFF were predominantly localized to astrocytes. Last, the expression kinetics of the APRIL and BAFF receptors coincided with CNS accumulation of ASC. Therefore, the factors associated with ASC migration, differentiation, and survival are all induced during acute viral encephalomyelitis, prior to ASC accumulation in the CNS. Importantly, the CNS expression kinetics implicate rapid establishment, and subsequent maintenance, of an environment capable of supporting differentiation and survival of protective antiviral ASC, recruited as plasmablasts from lymphoid organs.Virus-specific antibodies (Ab) play an important role in the control of many viral infections of the central nervous system (CNS) (17). Ab are delivered to the CNS either by diffusion across a compromised blood brain barrier (18, 53) or actively by Ab-secreting cells (ASC) which have infiltrated the CNS or differentiated locally in the inflamed tissue. Passage of Ab from serum is inefficient under steady-state conditions, making ASC-mediated Ab secretion at the site of CNS infection a more effective strategy of viral control. For example, Ab production by invading B cells is required to clear rabies virus from the CNS, as passively administered Ab do not mediate virus clearance (22). Furthermore, B cells in the CNS of Sindbis virus-infected mice continue to secrete Ab during viral RNA persistence, supporting the idea that ASC play a role in preventing viral recrudescence (71). In addition, prolonged intrathecal antiviral Ab production and ASC accumulation within the CNS occur following control of Semliki Forest virus (43, 53-55), measles virus (9, 48), and Theiler's murine encephalomyelitis virus (50, 51) infections.The concept of an ASC survival niche in the CNS during chronic infl...

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These results support the potential interest of IP rIFN-gamma as adjuvant treatment in ovarian cancer. Controlled prospective trials are required to determine its place in the therapeutic strategy of this malignancy.