A longitudinal study of JC virus serostatus stability among multiple sclerosis patients.

BACKGROUND: Anti-JC virus (JCV) antibody testing has been used increasingly to stratify multiple sclerosis (MS) patients into different disease modifying therapies.

OBJECTIVES: We assessed JCV serostatus stability longitudinally in MS patients who were regularly tested for anti-JCV antibody and examined the demographic and clinical factors associated with JCV serostatus.

METHODS: The data of MS patients who were screened for anti-JCV antibody using the two-step second-generation ELISA were collected between 1st October 2014 and 31st October 2015 at the MS clinic, Kuwait. Demographics, disease characteristics and JCV serostatus, including antibody index (AI), were obtained for patients with at least 12-months of follow-up results. Stable JCV serostatus was defined as anti-JCV antibody status that remained consistently negative or positive throughout the observation period. A change in serostatus was confirmed by a follow-up test at 6 months. Patients were labeled as JCV seroconverters (negative to positive), JCV seroreverters (positive to negative) or intermittently seropositive.

RESULTS: This study included 168 MS patients with anti-JCV antibody results for at least 1 year. Mean age and mean disease duration were 33.4 ± 9.8 and 8.1 ± 5.6 years respectively. In this cohort, 94% (n = 158) patients received natalizumab treatment with a mean of 27.2 ± 13.8 infusions. JCV stable serostatus (positive or negative) was observed in 84.5% (n = 142) with a mean follow-up duration of 23.8 ± 7.0 months. In this longitudinal study, relatively high frequencies of seroconverters (11.5%), intermittently seropositive (9.7%) and seroreverters (3.6%) were recorded. Age, gender, disease duration and number of natalizumab infusions did not influence JCV serostatus stability. JCV seroconversion risk was low with persistent AI < 0.9 beyond 18 months of initial testing.

CONCLUSION: Anti-JCV antibody index at baseline predicted stable negative as well as stable positive JCV serostatus over the observational period. The AI < 0.9 appeared to have a significant implication in the longitudinal stability of JCV AI in patients who were intermittently seropositive.