Effect of natalizumab on circulating CD4+ T-cells in multiple sclerosis.

Lars Börnsen,Finn Sellebjerg,Jeppe Romme Christensen,Helle Bach Søndergaard,Rikke Ratzer,Annette Bang Oturai,Per Soelberg Sørensen,Celia Oreja-Guevara

doi:10.1371/journal.pone.0047578

Abstract

In multiple sclerosis (MS), treatment with the monoclonal antibody natalizumab effectively reduces the formation of acute lesions in the central nervous system (CNS). Natalizumab binds the integrin very late antigen (VLA)-4, expressed on the surface of immune cells, and inhibits VLA-4 dependent transmigration of circulating immune-cells across the vascular endothelium into the CNS. Recent studies suggested that natalizumab treated MS patients have an increased T-cell pool in the blood compartment which may be selectively enriched in activated T-cells. Proposed causes are sequestration of activated T-cells due to reduced extravasation of activated and pro-inflammatory T-cells or due to induction of VLA-4 mediated co-stimulatory signals by natalizumab. In this study we examined how natalizumab treatment altered the distribution of effector and memory T-cell subsets in the blood compartment and if T-cells in general or myelin-reactive T-cells in particular showed signs of increased immune activation. Furthermore we examined the effects of natalizumab on CD4+ T-cell responses to myelin in vitro. Natalizumab-treated MS patients had significantly increased numbers of effector-memory T-cells in the blood. In T-cells from natalizumab-treated MS patients, the expression of TNF-α mRNA was increased whereas the expression of fourteen other effector cytokines or transcription factors was unchanged. Natalizumab-treated MS patients had significantly decreased expression of the co-stimulatory molecule CD134 on CD4+CD26HIGH T-cells, in blood, and natalizumab decreased the expression of CD134 on MBP-reactive CD26HIGHCD4+ T-cells in vitro. Otherwise CD4+ T-cells from natalizumab-treated and untreated MS patients showed similar responses to MBP. In conclusion natalizumab treatment selectively increased the effector memory T-cell pool but not the activation state of T-cells in the blood compartment. Myelin-reactive T-cells were not selectively increased in natalizumab treated MS.

Highlights

Relapses in multiple sclerosis (MS) are caused by focal inflammatory lesions, consisting of activated macrophages and CD4+ and CD8+ T-cells, in the central nervous system (CNS)
Neither did it appear to be due to repression of the genes encoding the very late antigen (VLA)-4 subunits a4 (ITGA4) and b1 (ITGB1) since the expression of these genes was comparable in whole blood samples from untreated and natalizumab-treated MS patients (Figure 1D)
Ex vivo studies showed that natalizumab did not interfere with the binding of the anti-VLA4 antibody used in the flow cytometry studies, suggesting that these antibodies bind to different epitopes, thereby validating the use of this antibody for flow cytometry analysis of VLA-4 expression in natalizumab-treated MS patients (Figure 1E)

Summary

Introduction

Relapses in multiple sclerosis (MS) are caused by focal inflammatory lesions, consisting of activated macrophages and CD4+ and CD8+ T-cells, in the central nervous system (CNS). It is assumed that the primary therapeutic effect of natalizumab relies on an inhibition of VLA-4-mediated extravasation of activated immune cells into the CNS [3] Still, it is not fully understood if natalizumab inhibits transendothelial migration by blocking ligation of VCAM-1 and VLA-4, as decreased levels of VLA-4 have been detected on the T-cell surface in natalizumab-treated MS-patients [1,5,6]. It is not fully understood if natalizumab inhibits transendothelial migration by blocking ligation of VCAM-1 and VLA-4, as decreased levels of VLA-4 have been detected on the T-cell surface in natalizumab-treated MS-patients [1,5,6] This observation could be an artifact due to competitive binding of natalizumab and the antibody used to visualize the VLA-4 molecule for flow cytometry, due to natalizumab induced internalization of VLA-4 or reduction of a4 or b1 integrin chain synthesis

Methods

Results

Conclusion