3rd International Workshop on HIV Drug Resistance 2-5 August 1994, Kauai, Hawaii, USA

A COMPARISON OF CULTURE AND PCR FOR THE QUANTIFICATION OF HIV-1 LOAD AND ZIDOVUDINE (ZDV) RESISTANCE IN PATIENTS FROM THE CONCORDE TRIAL

Int Wkshop HIV Drug Res 1994 Aug 2-5;3:28 (abstract no. 27)

Clive Loveday on behalf MRC UK Virology Working Party
MRC HIV Clinical Trials Centre, London, UK

The objectives of this study were to compare culture-based and PCR quantitative assays for the measurement of serum and cell HIV-1 viral load, and determination of phenotypic and genotypic resistance to ZDV.

Viral load by quantative in house PCR in serum and proviral DNA was compared with quantitative culture methods in plasma and PBMC. Phenotypic plasma and PBMC resistance was compared with an in house PCR-based point mutation assay (PMA).

Ninety-four patients (CDCII/III) in the Concorde trial for more than 1 year, were selected by the Trial centre in a ratio of 2:1 ZDV to placebo. An extra blood sample was collected from these patients and dispatched to the laboratory for separation and storage within 2 hours. HIV-1 was successfully isolated from 73 sets of frozen lymphocytes (78%). A good correlation (r=0.91) was found between cellular viraemia by culture and quantitative DNA load by PCR in 57 patients; in 13 patients DNA could be quantified only by PCR, and in 3 patients only by culture.

The majority (68) of 74 patients had serum viral load quantified by PCR but not culture, and only 17 specimens contained virus/viral RNA detectable by both methods. Measurement of mutational changes associated with ZDV resistance using serum RNA and PBMC DNA in the PMA showed significant correlation at all 5 codons (p<0.001). Comparison in serum RNA and PBMC DNA of phenotypic resistance by culture (expressed as IC₅₀ and IC₉₀) with single point mutational changes by PMA showed significant correlations (RNA/DNA):c219:p=0.004/0.0005, c215:p=0.001/0.0001, c70:p=0.005/0.0001, c67:p=0.004/0.0001, c41:p=0.065/0.05. The weakest relationship for RNA and DNA at codon 41 was due to the overall low prevalence of mutations at this codon.

The prevalence of codon mutations in serum RNA, tissue culture RNA and proviral DNA from PBMC were ranked by ZDV IC₅₀ RNA genomic resistance showed a correlation with phenotypic resistance, the mutations in RNA preceded that in DNA. The genotypic resistance in RNA derived from tissue culture demonstrated closer ranking with IC₅₀.

This study shows good correlation between viral culture and molecular technologies for the quantification of HIV-1 load and ZDV resistance.

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1994-08-02
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