A new quantitative HIV load assay based on plasma virion reverse transcriptase activity for the different types, groups and subtypes.
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.
Braun
Joséphine
J
Laboratoire de Virologie, Biostatistique, Centre Hospitalier Charles Nicolle, 1 rue de Germont, 76031 Rouen cedex, France.
Plantier
Jean-Christophe
JC
Hellot
Marie-France
MF
Tuaillon
Edouard
E
Gueudin
Marie
M
Damond
Florence
F
Malmsten
Anders
A
Corrigan
Gary E
GE
Simon
François
F
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*
D012367:RNA, Viral; C072416:reverse transcriptase, Human immunodeficiency virus 2; D054303:HIV Reverse Transcriptase; D012194:RNA-Directed DNA Polymerase