Introduction: Presence of anti-JC-virus antibodies (JCVAbs) is associated with the increased risk of natalizumab (NAT)-related progressive multifocal leukoencephalopathy (PML). Little is known about seroconversion rate and time to seroconversion in relapsing-remitting multiple sclerosis (RRMS) patients treated with NAT in Poland. The aim of the study was to assess the true risk of PML, seroconversion rate, and time to seroconversion in all JCVAb-negative RRMS patients treated with NAT in Poland. Methods: Demographic and clinical data of all Polish RRMS patients treated with NAT reimbursed by National Health Fund (NFZ) were prospectively collected in electronic files using the Therapeutic Programme Monitoring System provided by NFZ. The assessment of JCVAb presence (without collection of JCVAb index value) in serum (Unilabs, STRATIFY JCV: anti-JCV antibody ELISA) was done at the beginning of therapy and then repeated every 6 months. The maximum follow-up time was 4 years. In Poland, since 2013, according to the NFZ drug program guidance, only patients with negative JCVAb test have started treatment with NAT. Results: In all Polish multiple sclerosis centers, 210 negative JCVAb RRMS patients with at least 9 (±3) months of observation (146 females, 64 males, and the median age at baseline: 33 years) were included in the study. During the follow-up period, JCVAb status changed from negative to positive in 34 patients (16.2%). For half of the patients, the seroconversion was diagnosed 1 year after starting NAT treatment. In 4 patients (1.9%) during follow-up, JCVAb status changed again from positive to negative. In Poland, before establishment of NFZ drug program, 4 cases of PML in patients treated with NAT in clinical trials were diagnosed. In the NFZ drug program, since 2013, no patient treated with NAT has been diagnosed with PML. Conclusions: NAT therapy in JCV-seronegative RRMS patients is safe and results in the absence of PML cases. In Poland, JCV seroconversion rate is similar to that observed in other European countries.

中文翻译：

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John Cunningham 病毒状态、血清转化率和波兰 John Cunningham 病毒血清阴性复发缓解型多发性硬化患者进行性多灶性白质脑病的风险

简介：抗 JC 病毒抗体 (JCVAb) 的存在与那他珠单抗 (NAT) 相关进行性多灶性白质脑病 (PML) 的风险增加有关。在波兰接受 NAT 治疗的复发缓解型多发性硬化 (RRMS) 患者的血清转化率和血清转化时间知之甚少。该研究的目的是评估波兰所有接受 NAT 治疗的 JCVAb 阴性 RRMS 患者的 PML 真实风险、血清转化率和血清转化时间。方法：使用 NFZ 提供的治疗计划监测系统，前瞻性地将所有波兰 RRMS 患者的人口统计学和临床​​数据收集到电子文件中，这些数据由国家健康基金 (NFZ) 报销。评估血清中 JCVAb 的存在（不收集 JCVAb 指数值）（Unilas，STRATIFY JCV：抗 JCV 抗体 ELISA）在治疗开始时进行，然后每 6 个月重复一次。最长随访时间为 4 年。在波兰，自2013年以来，根据NFZ药物项目指南，只有JCVAb检测阴性的患者才开始进行NAT治疗。结果：在所有波兰多发性硬化症中心，研究包括 210 名观察了至少 9 (±3) 个月的阴性 JCVAb RRMS 患者（146 名女性，64 名男性，基线中位年龄：33 岁）。在随访期间，34 名患者 (16.2%) 的 JCVAb 状态从阴性变为阳性。对于一半的患者，在开始 NAT 治疗后 1 年诊断出血清转化。在随访期间，4 名患者 (1.9%) 的 JCVAb 状态再次从阳性变为阴性。在波兰，在建立 NFZ 药物计划之前，在临床试验中接受NAT治疗的患者中诊断出4例PML。在 NFZ 药物项目中，自 2013 年以来，没有接受过 NAT 治疗的患者被诊断出患有 PML。结论：JCV 血清阴性 RRMS 患者的 NAT 治疗是安全的，并且不会出现 PML 病例。在波兰，JCV 血清转化率与在其他欧洲国家观察到的相似。