Association of vitamin D serum levels and vitamin D supplementation with B cell kinetics and disease activity in Multiple Sclerosis patients treated with ocrelizumab: an Italian multi-center study

Background: Several observational studies have shown an association between low circulating levels of 25-hydroxy- vitamin D (25(OH)D) and an increase in inflammatory activity in Multiple Sclerosis (MS). Among its immunomodulatory functions, 25(OH)D suppresses proliferation and immunoglobulin production of B cells. 25(OH)D supplementation has been associated with better radiological outcomes in MS patients treated with interferon (IFN)-B, glatiramer acetate, fingolimod, natalizumab and rituximab. Our study is aimed at analyzing the association of 25(OH)D serum levels and supplementation with B cell kinetics and clinical-radiological outcomes of people with MS treated with ocrelizumab. Methods: We have retrospectively collected clinical and radiological data from 136 MS patients who have been treated with ocrelizumab, have undergone at least two treatment cycles and for whom data on serum 25(OH)D levels and intake were available. The patients were divided into three groups according to baseline 25(OH)D serum levels: deficient (≤19,9 ng/ml), insufficient (20-29,9 ng/ml), and normal range 25(OH)D (>30 ng/ml). According to 25(OH)D intake, we divided our population into users and non-users. To explore B cell kinetics at six- and twelve-month follow-ups, the patients were divided into two groups: with fast repopulation (FR) and slow repopulation rate (SR), based on the reappearance or non- appearance of CD19 at each time point. Results: When considering the entire population, the mean 25(OH)D serum level (sd) was 26.27 ng/ml (14.15). 43 (31,62%) patients were classified as deficient, 52 (38,24%) were classified as insufficient, and 41 (30,14%) showed 25(OH)D serum levels within the normal range. 60.29% (82/136) of the patients were classified as users, and 39.70% (54/136) as non-users. Over the eighteen-month treatment period, we observed a significant difference between the 25(OH)D users and the non-users as concerns the number of scans with at least one new/enlarging T2 lesion (2% vs 15.38%, respectively; p= 0.025). In the multinomial regression model, 25(OH)D deficiency (serum levels ≤19,9 ng/ml) was significantly associated with a higher likelihood of disease activity during a follow-up of eighteen months (p = 0.029, RRR = 4.84, Confidence Interval (CI) 1.17 - 20.01). After six months, there were 30/136 FR patients (22,05%), whereas only 22/136 (16,17%) showed early B cell reappearance at twelve month follow up. 86.66% of the patients in the FR group showed 25(OH)D levels lower than 30 ng/ml (25(OH)D deficiency or insufficiency), whereas only 65.09% of the SR patients presented vitamin D levels lower than 30 ng/ml (p= 0.024). In the logistic regression model, 25(OH)D serum levels below 30 ng/ml were associated with a higher likelihood of early B cell reappearance at six month follow up (p= 0.042). Conclusions: 25(OH)D supplementation and serum levels might be associated with B cell kinetics and radiological activity of patients with MS treated with ocrelizumab.