Long-term modifications of the peripheral immune repertoire after switching from sequestering disease-modifying treatments in multiple sclerosis

Background: Scarce data are available on the long-term immunological effects of multiple sclerosis (MS) disease-modifying treatments (DMTs).Objectives: This study aimed to investigate the long-term modifications of the peripheral immune repertoire on interruption of a sequestering DMT (natalizumab, fingolimod) and switch to another high-efficacy DMT.Methods: Lymphocyte subpopulations were assessed, every 6 months up to 48 months, in patients switched from fingolimod or natalizumab to ocrelizumab, and in patients switched from fingolimod to natalizumab, compared to patients switched to ocrelizumab or natalizumab from a moderate-efficacy DMT and to naive patients.Results: We included 389 MS patients (200 ocrelizumab and 189 natalizumab). After adjusting for baseline variables, patients switched from fingolimod to ocrelizumab showed lower CD3 + and CD4 + lymphocytes up to 48 months after switch (with lower percentage of naive CD4 +), and increased odds of total, CD3+, CD4+ lymphopenia. Patients switched from natalizumab to ocrelizumab showed higher CD3 + lymphocytes up to 36 months after switch, and higher CD4+, CD8+ lymphocytes up to 24 months. The frequency of infections was not influenced by previous treatment.Conclusions: A long-term persistence of the residual effects of the exposure to sequestering DMTs (fingolimod and less natalizumab) on the peripheral immune repertoire was observed after switching to another high-efficacy DMT.