title: Detection of serum reverse transcriptase activity in patients with ALS and unaffected blood relatives.
abstract: BACKGROUND
  Retroviral involvement in the etiology of sporadic ALS has been suspected for several years since the recognition that both murine and human retroviruses can cause motor neuron disease-like syndromes. In a pilot study, an increased prevalence of a retroviral marker (reverse transcriptase [RT] activity) was demonstrated in the serum of British patients with ALS. The current investigation was designed to confirm and extend these findings in a geographically distinct patient cohort under blinded testing conditions.
  
  
  METHODS
  A highly sensitive product-enhanced RT assay was employed to test coded sera obtained from 30 American patients with sporadic ALS and from 14 of their blood relatives, 16 of their spouses, and 28 nonrelated, nonspousal control subjects.
  
  
  RESULTS
  Serum RT activity was detected in a higher proportion of ALS patients (47%) than in non-blood-related controls (18%; p = 0.008). The prevalence of RT activity in the serum of spousal controls (13%) was similar to that in other non-blood-related controls. Unexpectedly, the prevalence of serum RT activity in blood relatives of ALS patients (43%) approached that in the ALS patients themselves.
  
  
  CONCLUSIONS
  These results confirm that patients with ALS have a significantly higher prevalence of serum reverse transcriptase (RT) activity than that seen in unrelated control subjects. The finding of a similarly increased prevalence in blood relatives of ALS patients raises the possibility that the observed RT activity might be due to an inherited endogenous retrovirus.
authors.affiliation: Centre of Virology, epartment of Infection, University College London, UK.
authors.forename: A J
authors.initials: AJ
authors.lastname: Steele
authors.forename: A
authors.initials: A
authors.lastname: Al-Chalabi
authors.forename: K
authors.initials: K
authors.lastname: Ferrante
authors.forename: M E
authors.initials: ME
authors.lastname: Cudkowicz
authors.forename: R H
authors.initials: RH
authors.lastname: Brown
authors.forename: J A
authors.initials: JA
authors.lastname: Garson
mesh_terms: D000328:Adult; D017668:Age of Onset; D000690:Amyotrophic Lateral Sclerosis / Q000097:blood / Q000235:genetics / Q000821:virology*; D015331:Cohort Studies; D018076:DNA, Complementary / Q000096:biosynthesis; D020077:Endogenous Retroviruses / Q000201:enzymology* / Q000472:pathogenicity; D005190:Family; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics; D012194:RNA-Directed DNA Polymerase / Q000097:blood*; D012680:Sensitivity and Specificity; D016037:Single-Blind Method; D018454:Spouses
chemical_list: D018076:DNA, Complementary; D012333:RNA, Messenger; D012194:RNA-Directed DNA Polymerase