JCV Seroconversion in a Group of Iraqi Patients with Multiple Sclerosis Receiving Natalizumab

Background: Natalizumab is a well-established therapy for multiple sclerosis (MS) that carries a risk of progressive multifocal leukoencephalopathy (PML) linked to John Cunningham virus (JCV). While JCV seroconversion has been well studied in the western hemisphere, data from the Middle east, including Iraq, are limited. Objective: To assess JCV seroconversion rates and associated risk factors among Iraqi MS patients treated with Natalizumab. Materials and Methods: a retrospective cohort study included patients with MS who were followed at the MS Clinic of Baghdad Medical City between January 2015 and December 2023. Data were collected from 290 patients and included demographics, treatment duration, prior exposure to other disease-modifying therapies (DMTs), and JCV antibody index values. The JCV antibody status was assessed every six months using a two-step enzyme-linked immunosorbent assay (ELISA). Results: In this sample, 18% (n = 52) exhibited persistent JCV seroconversion, corresponding to an annual conversion rate of 5.2%. The seroconversion rate was 25.4% in males and 15.5% in females; which was just short of reaching statistical significance (P-value = 0.06). No significant association was observed between seroconversion and age, treatment duration, or prior exposure to DMTs (P-value > 0.05). Notably, the highest seroconversion rate (20%) was observed in patients who had previously received treatment with interferon-β derivatives. Importantly, no cases of PML were identified during the study period. Conclusion: JCV seroconversion in Iraqi patients on natalizumab was 18% (annual 5.2%), with no significant risk factors identified. JCV monitoring remains crucial, and no cases of PML were detected.