Background: Progressive multifocal leukoencephalopathy (PML) is a severe complication of natalizumab (NTZ) treatment in multiple sclerosis (MS) patients. Based on the analysis of cryopreserved cells, several reports have showed that CD62L+ CD4+ T-cells percentage drops before PML onset.
Objective: To analyze CD62L and CD45RA expression on fresh-blood CD4+ and CD8+ T-cells from NTZ-treated patients, according to their estimated PML risk.
Methods: We prospectively enrolled 74 MS patients, including 62 NTZ-treated, and stratified them into low, intermediate and high PML risk groups. Circulating naïve and memory T-cell subsets were analyzed by flow cytometry.
Results: We found no correlation between the percentage of CD62L+ CD4+ T-cells and PML risk. In contrast, the repartition of CD8+ T-cells subpopulations was altered in the high risk group: both the percentage and absolute count of CD8+ CD62L- CD45RA- effector memory T- cells (TEM) was significantly higher compared to patients at lower risk despite similar CD3+ and CD8+ T-cell counts. One high-risk patient with elevated CD8+ TEM and CD62L+ CD4+ T-cell levels developed PML six months after sampling.
Conclusion: Our results suggest that CD8+ TEM cells should be evaluated in larger studies as a potential surrogate marker of PML risk in NTZ-treated patients.
Keywords: Biomarker; Lymphocytes; Multiple sclerosis; Progressive multifocal leukoencephalopathy.
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