title: Detection of human herpesvirus-6 in cerebrospinal fluid of patients with encephalitis.
abstract: OBJECTIVE
  Virus infections are the most common causes of encephalitis, a syndrome characterized by acute inflammation of the brain. More than 150 different viruses have been implicated in the pathogenesis of encephalitis; however, because of limitations with diagnostic testing, causative factors of more than half of the cases remain unknown.
  
  
  METHODS
  To investigate whether human herpesvirus-6 (HHV-6) is a causative agent of encephalitis, we examined for evidence of virus infection by determining the presence of viral sequence using polymerase chain reaction and assessed HHV-6 antibody reactivity in the cerebrospinal fluid of encephalitis patients with unknown cause. In a cohort study, we compared virus-specific antibody levels in cerebrospinal fluid samples of patients with encephalitis, relapsing-remitting multiple sclerosis, and other neurological diseases.
  
  
  RESULTS
  Our results demonstrated increased levels of HHV-6 IgG, as well as IgM levels, in a subset of encephalitis patients compared with other neurological diseases. Moreover, cell-free viral DNA that is indicative of active infection was detected in 40% (14/35) of encephalitis patients, whereas no amplifiable viral sequence was found in either relapsing-remitting MS or other neurological diseases patients. In addition, a significant correlation between polymerase chain reaction detection and anti-HHV-6 antibody response was also demonstrated.
  
  
  CONCLUSIONS
  Collectively, these results suggested HHV-6 as a possible pathogen in a subset of encephalitis cases.
authors.affiliation: Viral Immunology Section, Neuroimmunology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Karen
authors.initials: K
authors.lastname: Yao
authors.forename: Somayeh
authors.initials: S
authors.lastname: Honarmand
authors.forename: Alex
authors.initials: A
authors.lastname: Espinosa
authors.forename: Nahid
authors.initials: N
authors.lastname: Akhyani
authors.forename: Carol
authors.initials: C
authors.lastname: Glaser
authors.forename: Steven
authors.initials: S
authors.lastname: Jacobson