Infrequent detection of human herpesvirus 6 DNA in peripheral blood mononuclear cells from multiple sclerosis patients

Several studies have suggested an association between human herpesvirus 6 (HHV‐6) infection and multiple sclerosis. As HHV‐6 is predominantly a T‐cell tropic virus, we examined the frequency of detection of HHV‐6 genome in peripheral blood mononuclear cells from relapsing–remitting (n = 32) and chronic progressive (n = 14) patients and from healthy (n = 17) and neurological (n = 7) controls. Two sensitive polymerase chain reaction assays were used to target different regions within the HHV‐6 genome. Depending on the polymerase chain reaction assay used, the detection of HHV‐6 genome ranged from 11.7 to 23.5% (controls), 3.1 to 23.0% (relapsing–remitting), and 14.2 to 28.5% (chronic progressive). Although these observations do not exclude a pathogenic role for HHV‐6 in multiple sclerosis, they indicate a lack of correlation between HHV‐6 infection of peripheral blood mononuclear cells and the development of multiple sclerosis.