CD4/CD8 ratio during natalizumab treatment in multiple sclerosis patients

•Natalizumab is an effective treatment for multiple sclerosis but it is associated to progressive multifocal leukoencephalopathy occurrence.•Natalizumab can affect peripheral blood lymphocyte subsets preventing their migration in the CNS.•Although anti-JCV antibodies index has greatly improved the risk assessment for PML, other biological markers of PML risk have been sought.•CD4/CD8 ratio is related to JCV index, suggesting that it might be involved in anti JCV immune response.

Although improved, the risk of progressive multifocal leukoencephalopathy is a constant threat for patient affected by multiple sclerosis treated with natalizumab.We performed a 24 months longitudinal study aimed to evaluate the total WBC and lymphocytes subsets modifications and their correlations with anti-JCV antibody index after 1 and 2 years of natalizumab treatment.Natalizumab induced an increase of WBC, total and C19 + lymphocytes together with a decrease of CD3 +, CD4 + T lymphocytes and CD4/CD8 ratio, which was positively related to anti-JCV antibodies index at month 0, 12 and 24.Our study confirms that lymphocytes subsets are modified under NAT therapy. Implications of lymphocyte subsets alterations in the pathogenesis of PML are under analyses.

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