title: Elevated cerebrospinal fluid kynurenic acid levels in patients with tick-borne encephalitis.
abstract: BACKGROUND
  Kynurenic acid (KYNA) is a neuroactive metabolite of tryptophan that is thought to regulate cognitive functions. Previous studies have shown that levels of KYNA increase during virus infection and that this metabolite interacts with the immune system.
  
  
  OBJECTIVE
  The aim of the study was to investigate whether patients with tick-borne encephalitis (TBE), a viral infectious disease associated with long-term cognitive impairment, have increased levels of KYNA in the cerebrospinal fluid (CSF).
  
  
  METHODS
  CSF KYNA was analysed using high-performance liquid chromatography in 108 patients with TBE and 52 age-matched controls. Patients were classified according to the severity of TBE: mild (47%), moderate (44%) or severe (9%).
  
  
  RESULTS
  Concentrations of CSF KYNA were considerably higher in patients with TBE (5.3 nmol L(-1) ) than in control subjects (0.99 nmol L(-1) ). KYNA concentration in the CSF varied greatly amongst individuals with TBE and increased (P < 0.05) with the severity of disease.
  
  
  CONCLUSIONS
  This is the first study to demonstrate increased levels of CSF KYNA in patients with TBE. The importance of brain KYNA in both immune modulation and neurotransmission raises the possibility that abnormal levels of the compound in TBE might play a part in the pathophysiology of the disease. A detailed knowledge of endogenous brain KYNA during the course of CNS infection might yield further insights into the neuroimmunological role of the compound and may also provide new pharmacological approaches for the treatment of cognitive symptoms.
authors.affiliation: Department of Physiology & Pharmacology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Holtze
authors.forename: A
authors.initials: A
authors.lastname: Mickiené
authors.forename: A
authors.initials: A
authors.lastname: Atlas
authors.forename: L
authors.initials: L
authors.lastname: Lindquist
authors.forename: L
authors.initials: L
authors.lastname: Schwieler
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D004675:Encephalitis, Tick-Borne / Q000134:cerebrospinal fluid*; D005260:Female; D006801:Humans; D007736:Kynurenic Acid / Q000134:cerebrospinal fluid*; D008297:Male; D008875:Middle Aged; D055815:Young Adult
chemical_list: D007736:Kynurenic Acid