Anti-JCV antibody serostatus and longitudinal evaluation in a Portuguese Multiple Sclerosis population.

Multiple Sclerosis (MS) treatment with natalizumab is associated with Progressive Multifocal Leukoencephalopathy (PML). The risk of PML being related to the anti-JCV antibody index is well established, but there is less known about seroconversion rates in natalizumab-treated patients and longitudinal variation in the anti-JCV antibody index. Our objective was to assess anti-JCV antibody prevalence in an MS population and to evaluate the evolution of the anti-JCV antibody index in natalizumab-treated patients. To assess anti-JCV antibody prevalence, we included all patients who had the anti-JCV antibody test in our consultation, regardless of the treatment. To evaluate the evolution of the anti-JCV antibody index and seroconversion, only natalizumab-treated patients with at least two samples were selected. Demographic characteristics were evaluated. From a total of 371 patients included, 68.19% (n=253) were seropositive for anti-JCV antibodies (JCV+). There was a significant difference in anti-JCV antibody seropositivity concerning gender (male 76.27% vs. female 64.43%, p=0.023), but not age. To evaluate seroconversion, 85 patients who were initially seronegative (JCV-) were selected. The annual rate of seroconversion in the first two years was stable, but after that there was a significant increase with treatment duration (ρ=0.90, p=0.037): in the first year it was 5.88% (n=5/85); in the second, 5.71% (n=4/70); in the third, 6.82% (n=3/44); in the fourth, 10.34% (n=3/29); and in the fifth, 15.0% (n=3/20). The mean index variability was higher in patients who experienced seroconversion (1.16±0.97), followed by JCV+ patients (0.44±0.48), compared to JCV- patients (0.08±0.05). In conclusion, anti-JCV antibody prevalence in our population is comparable to other reported cohorts. The seroconversion rate increased with treatment duration. We found a high fluctuation in the antibody index in JCV+ patients.

Long-term effectiveness and safety of natalizumab in a Portuguese population.

OBJECTIVES: Natalizumab long-term effectiveness data in real-world relapsing-remitting multiple sclerosis (RRMS) is needed. Our objective is to report the long-term effectiveness and safety of natalizumab in a cohort of RRMS patients. METHODS: This is a retrospective study of natalizumab treatment for two years or longer in RRMS. Annualized relapse rate, Expanded Disability Status Scale (EDSS), brain magnetic resonance imaging T2 lesion volume, JC virus antibody status, previous treatments and adverse events were analysed. RESULTS: Seventy-one patients were included with a mean treatment duration of 44.86±17.39months. Over the treatment duration there was a significant decrease in annualized relapse rate (88.37%) and EDSS (28.57%); no evidence of clinical disease activity in 73.24% and 61.97% after one and two-years respectively; and brain magnetic resonance imaging T2 lesion volume remained stable. Forty patients suspended natalizumab, in 85% due to high risk of developing progressive multifocal leukoencephalopathy (PML). The major complication was PML (n=3). CONCLUSIONS: Natalizumab showed effectiveness in the long-term follow up period of our cohort, with reduction of ARR, EDSS, and MRI lesion load stabilization. PML was the major complication.