HHV-6 in Chronic Fatigue Syndrome

Abstract

Publisher Summary This chapter focuses on the relationship between chronic fatigue syndrome (CFS) and human herpesvirus-6 (HHV-6). It discusses two possible subgroups of HHV-6-related CFS: chronic, recurring HHV-6 reactivation in the periphery that precipitates or exacerbates CFS symptoms; and acute or chronic HHV-6 infection in the central nervous system (CNS). CFS is often referred to by other names or used interchangeably with similar disorders, such as chronic fatigue and immune dysfunction syndrome (CFIDS), fibromyalgia (FM), myalgic encephalomyelitis (ME), Gulf War Syndrome, and chronic Epstein–Barr disease. CFS patients often show evidence of immune dysfunction and/or dysregulation, such as low suppressor cell numbers, low numbers and efficacy of NK cells, and abnormal RNase L. Another HHV-6-related subgroup of CFS is that in which patients display CNS symptoms, including neurocognitive difficulties, such as memory impairment, ‘‘mental fog,’’ and diminished concentration. A higher proportion of HHV-6 in the spinal fluid appears to be of the A variant (compared with blood), suggesting that variant A is more neurotropic than variant B. Treatment of CFS with antivirals (e.g. acyclovir, ganciclovir, foscarnet, cidofovir) or immunomodulating therapy (e.g. Poly I: Poly C12U, and IV gammaglobulin) has met with mixed success, further suggesting the need to identify CFS subgroups for whom specific effective treatment can be targeted.