Natalizumab and Immune Cells

First-line natalizumab in multiple sclerosis: rationale, patient selection, benefits and risks

Natalizumab (NTZ) is a highly effective disease modifying therapy for the treatment of relapsing forms of multiple sclerosis (MS). Despite evidence to support its use as first-line therapy, risk of NTZ-associated progressive multifocal leukoencephalopathy (PML) has largely contributed to it being relegated to a second-line position. Recent preliminary data may allow for a more accurate analysis of JC virus (JCV) risk stratification of a given patient's PML risk. Herein we propose an algorithm to help guide clinicians through this decision-making process. We recommend that NTZ be considered for first-line use in JCV antibody negative MS patients, JCV 'low positive' MS patients without prior exposure to immunosuppression and for a limited period (12-24 months) in JCV 'high positive' MS patients with an aggressive disease course . We caution against first-line use in JCV antibody 'high positive' patients beyond 12-24 months and any JCV antibody positive patient with a history of prior immunosuppression.

Reactivation of human herpesvirus-6 in natalizumab treated multiple sclerosis patients

The alpha(4) integrin antagonist natalizumab was shown to be effective in patients with immune-mediated disorders but was unexpectedly associated with JC polyomavirus associated progressive multifocal leukoencephalopathy (PML) in two multiple sclerosis (MS) and one Crohn's disease patients. Impaired immune surveillance due to natalizumab treatment may have contributed to the JCV reactivation. As HHV-6 has been suggested to play a role in MS, we asked whether this virus could also have been reactivated during natalizumab therapy. Matched sera and CSF from a limited set of MS patients treated with and without natalizumab were examined for evidence of HHV-6. In addition, we also superinfected a persistent JC virus infected glial cell with HHV-6A to determine if JC virus can be increased. Elevated serum HHV6 IgG and HHV-6A DNA was detected in the CSF of a subset of patients but not controls. We confirmed that superinfection with HHV-6 of a JC virus infected glial cells increased expression of JCV. These results support the hypothesis that treatment with natalizumab may be associated with reduced immune surveillance resulting in reactivation of viruses associated with MS pathogenesis.