Search

Understanding the mechanisms of immune cell migration to multiple sclerosis lesions offers significant therapeutic potential. This study focused on the chemokines CXCL12 (SDF-1) and CXCL13 (BCA-1), both of which regulate B cell migration in lymphoid tissues. We report that immunohistologically CXCL12 was constitutively expressed in CNS parenchyma on blood vessel walls. In both active and chronic inactive multiple sclerosis lesions CXCL12 protein was elevated and detected on astrocytes and blood vessels. Quantitative PCR demonstrated that CXCL13 was produced in actively demyelinating multiple sclerosis lesions, but not in chronic inactive lesions or in the CNS of subjects who had no neurological disease. CXCL13 protein was localized in perivascular infiltrates and scattered infiltrating cells in lesion parenchyma. In the CSF of relapsing–remitting multiple sclerosis patients, both CXCL12 and CXCL13 were elevated. CXCL13, but not CXCL12, levels correlated strongly with intrathecal immunoglobulin production as well as the presence of B cells, plasma blasts and T cells. About 20% of CSF CD4+ cells and almost all B cells expressed the CXCL13 receptor CXCR5. In vitro, CXCL13 was produced by monocytes and at much higher levels by macrophages. CXCL13 mRNA and protein expression was induced by TNFα and IL-1β but inhibited by IL-4 and IFNγ. Together, CXCL12 and CXCL13 are elevated in active multiple sclerosis lesions and CXCL12 also in inactive lesions. The consequences of CXCL12 up-regulation could be manifold. CXCL12 localization on blood vessels indicates a possible role in leucocyte extravasation, and CXCL12 may contribute to plasma cell persistence since its receptor CXCR4 is retained during plasma cell differentiation. CXCL12 may contribute to axonal damage as it can become a neurotoxic mediator of cleavage by metalloproteases, which are present in multiple sclerosis lesions. The strong linkage of CXCL13 to immune cells and immunoglobulin levels in CSF suggests that this is one of the factors that attract and maintain B and T cells in inflamed CNS lesions. Therefore, both CXCL13 and CXCR5 may be promising therapeutic targets in multiple sclerosis.

We report that B cell–activating factor of the tumor necrosis factor (TNF) family (BAFF) is expressed in the normal human brain at ∼10% of that in lymphatic tissues (tonsils and adenoids) and is produced by astrocytes. BAFF was regularly detected by enzyme-linked immunosorbent assay in brain tissue lysates and in normal spinal fluid, and in astrocytes by double fluorescence microscopy. Cultured human astrocytes secreted functionally active BAFF after stimulation with interferon-γ and TNF-α via a furin-like protease-dependent pathway. BAFF secretion per cell was manifold higher in activated astrocytes than in monocytes and macrophages. We studied brain lesions with B cell components, and found that in multiple sclerosis plaques, BAFF expression was strongly up-regulated to levels observed in lymphatic tissues. BAFF was localized in astrocytes close to BAFF-R–expressing immune cells. BAFF receptors were strongly expressed in situ in primary central nervous system (CNS) lymphomas. This paper identifies astrocytes as a nonimmune source of BAFF. CNS-produced BAFF may support B cell survival in inflammatory diseases and primary B cell lymphoma.

The etiology of idiopathic cranial nerve palsies often remains unresolved. It has been hypothesised that viral reactivation of herpesviruses in the corresponding nuclei in the brainstem is the cause. We investigated the distribution of herpes simplex virus type 1 (HSV‐1) and varicella zoster virus (VZV) in nuclei that are associated with peripheral sensory ganglia [oculomotor (nIII), facial (nVII) nuclei] and in nuclei that are not associated with peripheral sensory ganglia [trochlear (nIV), abducens (nVI), and hypoglossal (nXII) nuclei] of five human brainstems. Samples of the cranial nerve nuclei and adjacent control tissue were taken from histological sections after precise identification of every single nucleus and control tissue. DNA and RNA amplification methods were used to determine the prevalence and distribution of HSV‐1 and VZV. The distribution of human herpes virus type 6 (HHV‐6) was also determined and served as a control, since HHV‐6 infection has never been associated with idiopathic cranial nerve palsies. HSV‐1 was distributed at random in all cranial nerve nuclei and control tissue, whereas VZV DNA was not detected in any of the samples examined. Surprisingly, HHV‐6 was present in almost all samples where HSV‐1 was also present, however, the latency associated transcript (LAT) of HSV‐1 was not found in any of the samples positive for HSV‐1 DNA. The absence of LAT in the samples positive for HSV‐1 and the distribution of HSV‐1 and HHV‐6 do not support the hypothesis that idiopathic cranial nerve palsies result from viral reactivation in the brainstem nuclei. J. Med. Virol. 74:102–106, 2004. © 2004 Wiley‐Liss, Inc.

In this study we compared the activation of monocytes by different bacterial products via Toll‐like receptors (TLR), and by different proinflammatory mediators. In response to TLR‐2, ‐4 and ‐5 engagement, ∼50% of monocytes produced TNF‐α, compared to only 5% after induction with IFN‐γ or GM‐CSF. Furthermore, a small proportion of monocytes produced IL‐10 after stimulation via TLR, but not after stimulation with cytokines. Both TLR‐ligands and inflammatory cytokines induced the expression of CD25, CD69, CD80 and, surprisingly, also of CD83, commonly regarded as an activation marker for mature dendritic cells (DC). Conversely, TLR‐ligands downregulated CD38, CD86 and ICOS‐L. Importantly, signaling lymphocytic activation molecule (SLAM; CD150) was identified as a monocyte activation marker that could be induced ex novo via TLR‐2, ‐4 and ‐5, but not by single stimulation with monocyte activators like IL‐1, TNF‐α, IFN‐β, IFN‐γ, GM‐CSF or CD40‐L. SLAM expression was transient and required mitogen activated protein kinase (MAPK) p38, but not ERK or JNK, and was surprisingly independent of NF‐κB. SLAM+ monocytes, which are absent in blood, were detected in spleen and tonsils, where they could be localized to T‐cell areas and germinal centers. Together, by comparing the response of monocytes to TLR‐ligands and inflammatory cytokines, we have identified a monocyte activation marker, SLAM, which differs in its inducibility from other monocyte activation markers. SLAM+ monocytes and macrophages were identified for the first time in vivo. Their presence might be a sign of innate immune activation.

The majority of trigeminal ganglia (TGs) are latently infected with α-herpesviruses [herpes simplex virus type-1 (HSV-1) and varicella-zoster virus (VZV)]. Whereas HSV-1 periodically reactivates in the TGs, VZV reactivates very rarely. The goal of this study was to determine whether herpesvirus latency is linked to a local immune cell infiltration in human TGs. T cells positive for the CD3 and CD8 markers, and CD68-positive macrophages were found in 30 of 42 examined TGs from 21 healthy individuals. The presence of immune cells correlated constantly with the occurrence of the HSV-1 latency-associated transcript (LAT) and only irregularly with the presence of latent VZV protein. In contrast, uninfected TGs showed no immune cell infiltration. Quantitative RT-PCR revealed that CD8, interferon-γ, tumor necrosis factor-α, IP-10, and RANTES transcripts were significantly induced in TGs latently infected with HSV-1 but not in uninfected TGs. The persisting lymphocytic cell infiltration and the elevated CD8 and cytokine/chemokine expression in the TGs demonstrate for the first time that latent herpesviral infection in humans is accompanied by a chronic inflammatory process at an immunoprivileged site but without any neuronal destruction. The chronic immune response seems to maintain viral latency and influence viral reactivation.

Human trigeminal ganglia were tested by double fluorescence in situ hybridization for the presence and distribution of herpes simplex virus type 1 (HSV-1) and varicella-zoster virus (VZV) latency. Latency transcripts of both viruses were detected in common areas within the ganglia. Also, a few single neurons were shown to harbor HSV-1 and VZV together. Ann Neurol 2003;54:678–681

Human trigeminal ganglia were tested by double fluorescence in situ hybridization for the presence and distribution of herpes simplex virus type 1 (HSV‐1) and varicella‐zoster virus (VZV) latency. Latency transcripts of both viruses were detected in common areas within the ganglia. Also, a few single neurons were shown to harbor HSV‐1 and VZV together. Ann Neurol 2003;54:678–681

Herpes simplex virus type 1 (HSV‐1) enters sensory neurons and can remain latent there until reactivation. During latency restricted HSV‐1 gene expression takes place in the form of latency‐associated transcripts (LAT). LAT has been demonstrated to be important not only for latency but also for reactivation, which may cause cranial nerve disorders.

Reactivation of herpes simplex virus type 1 (HSV-1) in the vestibular ganglion (VG) is the suspected cause of vestibular neuritis (VN). Recent studies reported the presence of HSV-1 DNA not only in human VGs but also in vestibular nuclei, a finding that indicates the possibility of viral migration to the human vestibular labyrinth. Distribution of HSV-1 DNA was determined in geniculate ganglia, VGs, semicircular canals, and macula organs of 21 randomly obtained human temporal bones by nested PCR. Viral DNA was detected in 48% of the labyrinths, 62% of the VGs, and 57% of the geniculate ganglia. The potential significance of this finding is twofold: (1) Inflammation in VN could also involve the labyrinth and thereby cause acute unilateral vestibular deafferentation. (2) As benign paroxysmal positional vertigo often occurs in patients who have had VN, it could also be a sequel of viral labyrinthitis.

Multiple sclerosis (MS) can be divided into 4 clinical forms: relapsing‐remitting (RR), primary progressive (PP), secondary progressive (SP), and progressive relapsing (PR). Since PP‐MS is notably different from the other forms of MS, both clinically and pathologically, the question arises whether PP‐MS is immunologically similar to the other forms. The pathogenesis of the PP‐MS remains unclear, partly due to a lack of highly relevant animal models. Using an encephalitogenic peptide from myelin oligodendrocyte glycoprotein (MOG)92–106, we have established animal models that mimic different forms of MS in 2 strains of H‐2smice, SJL/J and A.SW. We induced experimental allergic encephalomyelitis (EAE) using MOG92‐106in the presence or absence of supplemental Bordetella pertussis (BP). Although, SJL/J mice developed RR‐EAE whether BP was given or not, A.SW mice developed PP‐EAE without BP and SP‐EAE with BP. Histologically, SJL/J mice developed mild demyelinating disease with T cell infiltration, while A.SW mice developed large areas of plaque‐like demyelination with immunoglobulin deposition and neutrophil infiltration, but with minimal T cell infiltration. In A.SW mice without BP, high titer serum anti‐MOG antibody was detected and the anti‐MOG IgG2a/IgG1 ratio correlated with survival times of mice. We hypothesized that, in A.SW mice, a Th2 response favors production of myelinotoxic antibodies, leading to progressive forms with early death. Our new models indicate that a single encephalitogen could induce either RR‐, PP‐, or SP‐ forms of demyelinating disease in hosts with immunologically different humoral immune responses.

Theiler's murine encephalomyelitis virus (TMEV) infection and relapsing‐remitting experimental allergic encephalomyelitis (R‐EAE) have been used to investigate the viral and autoimmune etiology of multiple sclerosis (MS), a possibleTh1‐type mediated disease. DNA immunization is a novel vaccination strategy in which few harmful effects have been reported. Bacterial DNA and oligodeoxynucleotides, which contain CpG motifs, have been reported to enhance immunostimulation. Our objectives were two‐fold: first, to ascertain whether plasmid DNA, pCMV, which is widely used as a vector in DNA immunization studies, could exert immunostimulation in vitro; and second, to test if pCMV injection could modulate animal models for MS in vitro.We demonstrated that this bacterially derived DNA could induce interleukin (IL)‐12, interferon (IFN)γ (Th1‐promoting cytokines), and IL‐6 production as well as activate NK cells. Following pCMV injections, SJL/J mice were infected with TMEV or challenged with encephalitogenic myelin proteolipid protein (PLP) peptides. pCMV injection exacerbated TMEV‐induced demyelinating disease in a dose‐dependent manner. Exacerbation of the disease did not correlate with the number of TMEV‐antigen positive cells but did with an increase in anti‐TMEV antibody. pCMV injection also enhanced R‐EAE with increased IFNγ and IL‐6 responses. These results caution the use of DNA vaccination in MS patients and other possible Th1‐mediated diseases.

Animal studies suggest that adult bone marrow cells have the potential to migrate into the brain and generate new neural cells. Because data on this physiologic repair mechanism in humans are lacking, we investigated bone marrow engraftment into the brain of bone marrow recipients after sex-mismatched transplantation. Brain sections of seven allogeneic female bone marrow recipients were examined. The Y-chromosome, which served as a natural marker of donor bone marrow-derived cells after male-to-female transplantation, was identified by in situ hybridization. The neural phenotype of Y-chromosome-positive cells was determined using neural nuclear protein (NeuN) immunohistochemistry. Y-chromosome-positive cells expressing NeuN were found within the first 3 months after transplantation in both the cerebrum and the cerebellum at a frequency of 0.003% to 0.013% of all neurons. These cells were observed only in patients with cerebral lymphocytic infiltration and graft-versus-host disease. Our data suggest that adult bone marrow cells are capable of generating cells that express the neural marker NeuN early after transplantation. Cells with this specific phenotype may contribute to tissue repair in brain regions remote from neurogenic zones.

The immune response to latent herpesvirus infections was compared in human trigeminal ganglia (TG) and dorsal root ganglia (DRG) of 15 dead individuals. On the basis of our previous findings, we hypothesized that T-cells would be attracted to sensory neurons latently infected with herpes simplex virus type 1 (HSV-1), but not to those harboring latent varicella zoster virus (VZV). We showed that the TG contain a positive hybridization signal for HSV-1 latency-associated transcript (LAT), whereas the DRG from the same individuals lack detectable LAT. In contrast, immunohistochemistry revealed that latent VZV protein 62 stained positive in the vast majority of all tested TG and DRG. T-cell infiltrates prominently surrounded individual neurons in the TG but not in the DRG. TaqMan polymerase chain reaction also showed higher expression of CD8 and RANTES transcripts in the TG versus DRG. Only the infiltrates in the TG, but not in the DRG, produced RANTES at the protein level. Because it has been shown that RANTES protein is produced only after T-cell receptor stimulation, we assume that T-cell infiltration is associated with antigen recognition in the TG but not in the DRG.