title: A new quantitative HIV load assay based on plasma virion reverse transcriptase activity for the different types, groups and subtypes.
abstract: BACKGROUND
  Plasma viral load monitoring is an integral part of the standard of care for HIV-infected patients in industrialized countries. In developing countries, viral load assay is either unaffordable or hindered by on-site maintenance and/or technical problems.
  
  
  OBJECTIVE
  To evaluate a new and simple quantitative assay for plasma HIV reverse transcriptase (RT) activity; and to compare RT activity-based and RNA-based quantification in plasma samples from patients infected by different subtypes of HIV-1 group-M, HIV-1 group-O and HIV-2.
  
  
  METHODS
  The RT-based viral load assay involves separation of the virion-protected RT and quantification of its activity with an enzyme immunoassay. Plasma viraemia was quantified both by RT activity and by RNA copies in 322 samples from 236 HIV-1 group M-infected patients, including serial samples from 54 patients. Samples from 49 patients infected by HIV-1 group O or HIV-2 were also tested.
  
  
  RESULTS
  RT activity and RNA copies were detected in 70% of plasma samples; respectively 25% and 1% of samples contained detectable RNA copies or RT activity alone. Measured RT activity corresponded to 48%, 96% and 100% of samples with 1.7-4.0 log(10), 4.1-4.8 log(10) and 4.9-6.7 log(10) RNA copies/ml, respectively. The values of the two assays correlated independently of the HIV subtype (P < 0.0001) and group/type (P < 0.03). Patient follow-up showed a similar pattern of viraemia with the two assays.
  
  
  CONCLUSIONS
  Plasma RT activity assay is a simple, cheap and reliable alternative for HIV viral load determination. As such, it could be particularly valuable for diagnosis and treatment monitoring in developing countries.
authors.affiliation: Laboratoire de Virologie, Biostatistique, Centre Hospitalier Charles Nicolle, 1 rue de Germont, 76031 Rouen cedex, France.
authors.forename: Joséphine
authors.initials: J
authors.lastname: Braun
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Plantier
authors.forename: Marie-France
authors.initials: MF
authors.lastname: Hellot
authors.forename: Edouard
authors.initials: E
authors.lastname: Tuaillon
authors.forename: Marie
authors.initials: M
authors.lastname: Gueudin
authors.forename: Florence
authors.initials: F
authors.lastname: Damond
authors.forename: Anders
authors.initials: A
authors.lastname: Malmsten
authors.forename: Gary E
authors.initials: GE
authors.lastname: Corrigan
authors.forename: François
authors.initials: F
authors.lastname: Simon
mesh_terms: D015658:HIV Infections / Q000175:diagnosis* / Q000821:virology; D054303:HIV Reverse Transcriptase / Q000097:blood*; D006801:Humans; D012367:RNA, Viral / Q000097:blood; D012194:RNA-Directed DNA Polymerase / Q000097:blood*; D012680:Sensitivity and Specificity; D019562:Viral Load / Q000379:methods*
chemical_list: D012367:RNA, Viral; C072416:reverse transcriptase, Human immunodeficiency virus 2; D054303:HIV Reverse Transcriptase; D012194:RNA-Directed DNA Polymerase