Type O blood group associates with higher anti‐JC polyomavirus antibody levels

BACKGROUND: Patients with multiple sclerosis (MS) and high anti‐JC polyomavirus (JCPyV) antibodies in blood have an increased risk for the development of progressive multifocal leukoencephalopathy (PML) when treated for MS. To test the hypothesis that type O blood group associates with anti‐JCPyV antibody levels and the risk of developing PML, we characterized ABO blood group antigen on blood samples of 62 patients with PML, and 64 MS controls without PML. METHODS: Monocentric retrospective cohort study. Anti‐JCPyV antibody levels in arbitrary units (AU) were determined in sera using an ELISA‐based method, and blood group specific antibodies using standardised test erythrocytes. RESULTS: Anti‐JCPyV antibody levels were higher in individuals with blood group O compared with all other blood groups (O: median AU: 129; not O: median AU: 53; p = .005). This association was not observed for the closely related BK virus. Of the 62 patients with PML, 29 (47%, 95% confidence interval (CI) 35%–59%) were of blood group O, which showed a nonsignificant trend to differ from the expected distribution in the German population (41%), and the MS controls studied (36%, 95% CI 25%–48%). CONCLUSION: The ABO blood group O antigen associates with higher anti‐JCPyV antibody levels and may impact the risk of the later development of PML. The overrepresentation of blood group O in cases with PML was in line with a previous publication. Larger studies are warranted to assess a potential value of host genetic markers, such as the ABO status, for PML risk prediction during immunotherapy.