Study of the anti-JCV antibody levels in a Spanish multiple sclerosis cohort.

Background One of the risk factor to develop progressive multifocal leukoencephalopathy (PML) among natalizumab-treated patients is the presence and high levels of anti-JCV antibodies. Our purpose was to test the association of different clinical and demographic variables with the presence and levels of anti-JCV antibodies in a Spanish cohort of patients with multiple sclerosis (MS) during natalizumab treatment. Materials and methods All patients with MS from two hospitals with at least one measure of the anti-JCV antibodies levels (2011–2014) were recruited, among them were two PML cases. Anti-JCV antibody levels were assessed using two-step ELISA. Results A total of 1061 patients (16 3% natalizumab-treated) participated in this study. The seropositivity rate of anti-JCV antibodies was 58 2%. It increased with age (Pcorrected = 0 00005) and was lower among HLADRB1* 15:01 carriers (Pcorrected = 0 049). The two patients with PML were HLA-DRB1*15:01 carriers. We had at least three quarterly anti-JCV antibody measurements (index value) from 137 patients, whose levels did not increase during natalizumab treatment. However, 5 8% of these patients had an increase of the index value higher of one point in a maximum of 6 months, something that was more frequently observed (P = 0 054) among patients treated with immunosuppressant prior to natalizumab onset. Conclusions Old age and HLA-DRB1*15:01 were the factors that influence positively and negatively, respectively, our anti-JCV antibody prevalence, although our both PML cases were HLA-DRB1*15:01carriers. Most of our patients showed a stable anti-JCV antibody index values during natalizumab treatment.post-print188 K