Int Conf AIDS. 1998;12:787 (abstract no. 41225). Unique Identifier :
BACKGROUND: A line probe assay has been developed for the simultaneous
detection of the common mutations of the reverse transcriptase gene of
HIV-1 which have been associated with resistance to zidovudine (AZT),
lamivudine (3TC), didanosine (ddI) and zalcitabine (ddC). The assay
detects the presence of both consensus wild type and resistant genotypes
at codons 41, 69, 70, 74, 75, 184 & 215. The test is based on the
amplification of the reverse transcriptase gene using biotinylated
primers followed by reverse hybridisation of the amplicon with a series
of complementary probes bound to a nitro-cellulose strip. Signal
generation is accomplished using a streptavidin-alkaline phosphatase
conjugate and BCIP/NBT substrate. We assessed the ability of LiPA HIV-1
RT to determine if an increase in the proportion of resistant virus for
a particular codon correlates with increase in viral load. METHODS:
Plasma samples from 19 patients were tested using the Murex-Innogenetics
HIV-1 RT LiPA assay and Roche Amplicor HIV-1 Monitor viral load test. A
semi-quantitative estimate of LiPA signal intensity at each codon was
determined. RESULTS: The results show a correlation between an
increasing viral load and the emergence of mutations which are
associated with resistance to AZT. LiPA analysis illustrates the
presence of a mixture of mutant and wild type consensus sequence in the
plasma virus population. The subsequent outgrowth of mutant virus as the
apparently dominant quasi-species as measured by relative LiPA signal
intensity correlated with an increase in the viral load. CONCLUSIONS:
Our results suggest that the signal intensity of both wild type and
resistant lines on the LiPA strip may be used to determine the relative
proportions of wild type and mutant virus present in the total virus
population. The relative increase in signal intensity of the mutant
probe compared to the wild type probe correlates with outgrowth of the
resistant species which in turn accounts for an increase in viral load.
MEETING ABSTRACTS Anti-HIV Agents/PHARMACOLOGY Drug Resistance,
Microbial/GENETICS Human HIV Infections/BLOOD/*VIROLOGY
HIV-1/*ENZYMOLOGY/GENETICS HIV-1 Reverse Transcriptase/*GENETICS
*Mutation Nucleic Acid Hybridization Reagent Kits, Diagnostic Reverse
Transcriptase Inhibitors/PHARMACOLOGY Zidovudine/PHARMACOLOGY