High interindividual variability in the CD4/CD8 T cell ratio and natalizumab concentration levels in the cerebrospinal fluid of patients with multiple sclerosis.

Strongly decreased leucocyte counts and a reduced CD4/CD8 T cell ratio in the cerebrospinal fluid (CSF) of natalizumab (NZB)-treated multiple sclerosis (MS) patients may have implications on central nervous (CNS) immune surveillance. With regard to NZB-associated progressive multi-focal leucoencephalopathy, we aimed at delineating a relationship between free NZB, cell-bound NZB, adhesion molecule (AM) expression and the treatment-associated shift in the CSF T cell ratio. Peripheral blood (PB) and CSF T cells from 15 NZB-treated MS patients, and CSF T cells from 10 patients with non-inflammatory neurological diseases and five newly diagnosed MS patients were studied. Intercellular adhesion molecule-1 (ICAM-1), leucocyte function antigen-1 (LFA-1), very late activation antigen-4 (VLA-4), NZB saturation levels, and T cell ratios were analysed by flow cytometry. NZB concentrations were measured by enzyme-linked immunosorbent assay (ELISA). Lower NZB saturation levels (P<0.02) and a higher surface expression of ICAM-1 and LFA-1 (P<0.001) were observed on CSF CD8 T cells. CSF T cell ratios (0.3-2.1) and NZB concentrations (0.01-0.42 µg/ml) showed a pronounced interindividual variance. A correlation between free NZB, cell-bound NZB or AM expression levels and the CSF T cell ratio was not found. Extremely low NZB concentrations and a normalized CSF T cell ratio were observed in one case. The differential NZB saturation and AM expression of CSF CD8 T cells may contribute to their relative enrichment in the CSF. The reduced CSF T cell ratio appeared sensitive to steady-state NZB levels, as normalization occurred quickly. The latter may be important concerning a fast reconstitution of CNS immune surveillance.

Natalizumab saturation: biomarker for individual treatment holiday after natalizumab withdrawal?

BACKGROUND: More and more patients with multiple sclerosis (MS) switch from natalizumab to fingolimod because of the risk of progressive multifocal leukoencephalopathy. The duration of the treatment holiday is still under debate referring to a possible recurrence of disease activity. AIM OF THE STUDY: The aim of this study was to evaluate the prognostic value of natalizumab saturation on T cells for the recurrence of clinical and radiological disease activity. METHODS: Cell surface-bound natalizumab saturation (in%) of CD8+ and CD4+ T cells from five patients with MS was determined before initiation of fingolimod by flow cytometry and related to clinical and MRI outcome during a 6-month follow-up. RESULTS: In two patients with either clinical or radiological disease activity, the natalizumab saturation on CD8+ and CD4+ T cells was <30%. In contrast, the remaining three patients with absence of disease activity had a median natalizumab saturation of 70% (range 59-79%) on CD4+ and 66% (range 52-68%) on CD8+ T cells. CONCLUSIONS: The data of this pilot study indicate that clinical and radiological disease activity is closely linked to natalizumab saturation at the time point of switch. The determination of natalizumab saturation may be an essential tool to monitor cessation of natalizumab treatment.

Glatiramer acetate attenuates the pro-migratory profile of adhesion molecules on various immune cell subsets in multiple sclerosis.

An altered expression pattern of adhesion molecules (AM) on the surface of immune cells is a premise for their extravasation into the central nervous system (CNS) and the formation of acute brain lesions in multiple sclerosis (MS). We evaluated the impact of glatiramer acetate (GA) on cell-bound and soluble AM in the peripheral blood of patients with relapsing-remitting MS (RRMS). Fifteen patients treated de novo with GA were studied on four occasions over a period of 12 months. Surface levels of intracellular cell adhesion molecule (ICAM)-1, ICAM-3, lymphocyte function-associated antigen (LFA)-1 and very late activation antigen (VLA)-4 were assessed in T cells (CD3(+) CD8(+) , CD3(+) CD4(+) ), B cells, natural killer (NK) cells, natural killer T cells (NK T) and monocytes by five-colour flow cytometry. Soluble E-selectin, ICAM-1, ICAM-3, platelet endothelial cell adhesion molecule (PECAM)-1, P-selectin and vascular cell adhesion molecule (VCAM)-1 were determined with a fluorescent bead-based immunoassay. The pro-migratory pattern in RRMS was verified by comparison with healthy controls and was characterized by up-regulation of LFA-1 (CD3(+) CD4(+) T cells, B cells), VLA-4 (CD3(+) CD8(+) T cells, NK cells), ICAM-1 (B cells) and ICAM-3 (NK cells). Effects of GA treatment were most pronounced after 6 months and included attenuated levels of LFA-1 (CD3(+) CD4(+) ) and VLA-4 (CD3(+) CD4(+) , CD3(+) CD8(+) , NK, NK T, monocytes). Further effects included lowering of ICAM-1 and ICAM-3 levels in almost all immune cell subsets. Soluble AM levels in RRMS did not differ from healthy controls and remained unaltered after GA treatment. The deregulated pro-migratory expression profile of cell-bound AM is altered by GA treatment. While this alteration may contribute to the beneficial action of the drug, the protracted development and unselective changes indicate more secondary immune regulatory phenomena related to these effects.

Molecular evidence of transient therapeutic effectiveness of natalizumab despite high-titre neutralizing antibodies.

Natalizumab is a humanized monoclonal antibody directed against the alpha-4 integrin subunit of very late activation antigen-4 (VLA-4). Natalizumab neutralizing antibodies (NAB) have been found to significantly reduce beneficial effects of natalizumab treatment in multiple sclerosis. We investigated interactions of NAB with natalizumab by serial measurements of alpha-4 integrin levels on peripheral blood mononuclear cells using flow cytometry. In addition, serum concentrations of soluble vascular cell adhesion molecule-1 (sVCAM-1), the endothelial ligand of VLA-4, and serum NAB were serially determined. Natalizumab infusion led to a transient reduction in alpha-4 integrin levels on immune cells and serum sVCAM-1 levels along with serum negativity of NAB lasting for a few days post-infusion. Apparently, the high-dose effect of freshly infused natalizumab resulted in a transient neutralization of NAB possibly involving a transient therapeutic effectiveness.

Adhesion molecules are promising candidates to establish surrogate markers for natalizumab treatment.

BACKGROUND: Natalizumab is the first monoclonal antibody therapy approved for multiple sclerosis (MS). Its therapeutic mechanism is the blockade of the α4-integrin subunit of the adhesion molecule (AM) very late activation antigen-4 (VLA-4), which leads to an inhibition of immune cell extravasation into the central nervous system (CNS). METHODS: We investigated changes in the expression levels of unblocked α4-integrin and further AM (intercellular adhesion molecule-1, -2, -3 (cICAM-1, -2, -3), leukocyte function associated antigen-1 (LFA-1)) on peripheral blood mononuclear cells (PBMC) determined by flow cytometry from 25 patients with MS before the first natalizumab infusion and before the fourth infusion. In 15 MS patients AM expression was evaluated every 3 months over 1 year. RESULTS: We found a significant decrease (p < 0.0001) of unblocked α4-integrin cell surface expression on all investigated PBMC subsets (T cells -61.7%, B cells -69.1%, monocytes/macrophages -46.4%) in the blood of MS patients after 3 months of natalizumab treatment. Moreover, a continuous decrease (p < 0.05) of unblocked α4-integrin expression levels was seen after 3, 6, 9, and 12 months. As a secondary effect, expression levels of the other investigated AM were differentially affected. CONCLUSIONS: Results show a sustained decrease of unblocked α4-integrin expression not only in all patients but also in all investigated PBMC subsets. This probably results in a continuously decreasing transmigration of PBMC into the CNS and may explain the improved clinical efficacy in the second treatment year and also the increasing risk of progressive multifocal leukoencephalopathy during long-term natalizumab therapy. We conclude that AM expression profiles are promising candidates for the development of a biomarker system to determine both natalizumab treatment response and patients at risk for opportunistic CNS infections.

Ferritin and FasL (CD95L) mediate density dependent apoptosis in primary rat hepatocytes.

Based on a recent description of an apoptosis stimulating property for hepatocyte derived isoferritins, this investigation demonstrates that ferritin, released in vitro from hepatocytes substantially contributes to density dependent apoptosis in primary hepatocytes and is significantly (P < or = 0.05) inhibited by anti-H-ferritin antibody rH02. Furthermore, total protein release and albumin secretion rapidly decline in a time and density dependent mode under serum-free conditions, whereas ferritin secretion, which is upregulated at initial stages of primary culture is not affected by cell density. Supplementation with dexamethasone (DEX) or proliferative stimulation by epidermal growth factor (EGF) and insulin strongly suppresses density dependent apoptosis. Both regimens have previously been shown to inhibit isoferritin mediated apoptosis in hepatocytes, most likely by interrupting proapotitc mitochondrial signalling. Finally, FasL/Fas also participates in density dependent apoptosis, since apoptosis is significantly (P < or = 0.005) reduced in high density cultures supplemented with an anti-FasL antibody. This antibody has also been shown to neutralise ferritin mediated apoptosis in primary hepatocytes, suggesting a linkage of ferritin and Fas in density dependent apoptosis. In conclusion, ferritin contributes to apoptosis in primary hepatocytes in an autocrine, density dependent mode, involving Fas stimulation and proapoptotic mitochondrial signalling. With respect to liver physiology, these findings may indicate that ferritin plays a yet unrecognised role as an acute phase signalling molecule in early stages of tissue repair and liver regeneration, and may also be responsible for the limited ability to propagate human hepatocytes in culture and the limited expansion of donor cells in the recipient liver upon cell transplantation.