Because previous studies showed that the HLA-DQB1*06:03 haplotype was also positively associated with JCV-serostatus [13] and that phenylalanine at position 9 of HLA-DQB1 was associated with MS susceptibility in Japanese [48], susceptible HLA alleles other than HLA-DRB1 and -DPB1 may also be related to the immune response against JCV in patients with MS. This evidence concerns the gene HLA-DRB1 and myeloid sarcoma.