• N Schwab, J C Ulzheimer, R J Fox, T Schneider-Hohendorf, B C Kieseier, C M Monoranu, S M Staugaitis, W Welch, S Jilek, R A Du Pasquier, W Brück, K V Toyka, R M Ransohoff, and H Wiendl.
• Department of Neurology–Department of Inflammatory Diseases of the Nervous System and Neurooncology,University of Mu¨nster, Germany.
• Neurology. 2012 Feb 14; 78 (7): 458-67; discussion 465.

ObjectivesProgressive multifocal leukoencephalopathy (PML) has become much more common with monoclonal antibody treatment for multiple sclerosis and other immune-mediated disorders.MethodsWe report 2 patients with severe psoriasis and fatal PML treated for ≥3 years with efalizumab, a neutralizing antibody to αLβ2-leukointegrin (LFA-1). In one patient, we conducted serial studies of peripheral blood and CSF including analyses of leukocyte phenotypes, migration ex vivo, and CDR3 spectratypes with controls coming from HIV-infected patients with PML. Extensive pathologic and histologic analysis was done on autopsy CNS tissue of both patients.ResultsBoth patients developed progressive cognitive and motor deficits, and JC virus was identified in CSF. Despite treatment including plasma exchange (PE) and signs of immune reconstitution, both died of PML 2 and 6 months after disease onset. Neuropathologic examination confirmed PML. Efalizumab treatment was associated with reduced transendothelial migration by peripheral T cells in vitro. As expression levels of LFA-1 on peripheral T cells gradually rose after PE, in vitro migration increased. Peripheral and CSF T-cell spectratyping showed CD8+ T-cell clonal expansion but blunted activation, which was restored after PE.ConclusionsFrom these data we propose that inhibition of peripheral and intrathecal T-cell activation and suppression of CNS effector-phase migration both characterize efalizumab-associated PML. LFA-1 may be a crucial factor in homeostatic JC virus control.

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