Frequent HHV-6 reactivation in multiple sclerosis (MS) and chronic fatiguesyndrome (CFS) patients

Background: HHV-6 is a ubiquitous virus and its infection usually occurs in childhood and then becomes a latent infection. HHV-6 reactivation has been shown to play a role in the pathogenesis of AIDS and several other disease s. Objectives: To determine what role HHV-6 infection or reactivation plays in the pathogenesis of multiple sclerosis (MS) and chronic fatigue syndrom e (CFS). Results: Twenty-one MS and 35 CFS patients were studied and follow ed clinically. In these patients, we measured HHV-6 IgG and IgM antibody le vels and also analyzed their peripheral blood mononuclear cells (PBMCs) for the presence of HHV-6, using a short term culture assay. In both MS and CF S patients, we found higher levels of HHV-6 IgM antibody and elevated level s of IgG antibody when compared to healthy controls. Seventy percent of the MS patients studied contained IgM antibodies for HHV-6 late antigens (caps id), while only 15% of the healthy donors (HD) and 20% of the patients with other neurological disorders (OND) had HHV-6 IgM antibodies. Higher freque ncy of IgM antibody was also detected in CFS patients (57.1%) compared to H D (16%). Moreover, 54% of CFS patients exhibited antibody to HHV-6 early pr otein (p41/38) compared to only 8.0% of the HD. Elevated IgG antibody titer s were detected in both the MS and the CFS patients. PBMCs from MS, CFS and HD were analyzed in a short term culture assay in order to detect HHV-6 an tigen expressing cells and to characterize the viral isolates obtained as e ither Variant A or B. Fifty-four percent of MS patients contained HHV-6 ear ly and late antigen producing cells and 87% of HHV-6 isolates were Variant B. Isolates from CFS, patients were predominately Variant A (70%) and isola tes from HD were predominately Variant B (67%). Moreover, one isolate from OND was also Variant B. Persistent HHV-6 infection was found in two CFS pat ients over a period of 2.5 years and HHV-6 specific cellular immune respons es were detected in PBMCs from ten CFS patients. Conclusions: In both MS an d CFS patients, we found increased levels of HHV-6 antibody and HHV-6 DNA. A decrease in cellular immune responses was also detected in CFS patients. These data suggest that HHV-6 reactivation plays a role in the pathogenesis of these disorders. (C) 2000 Elsevier Science B.V. All rights reserved.