The authors discuss studies on the low-cost viral load assays that are currently available and their potential for use in resource-limited settings.

Human immunodeficiency virus (HIV) type 2 infection is characterized by slower disease progression to acquired immunodeficiency syndrome than results from HIV-1 infection. To better understand the biological factors underlying the different natural histories of infection with these 2 retroviruses, we examined the relationship between HIV RNA and DNA levels and the rate of CD4(+) T cell decline among 472 HIV-1- and 114 HIV-2-infected individuals from Senegal. The annual rate of CD4(+) T cell decline in the HIV-2 cohort was approximately one-fourth that seen in the HIV-1 cohort. However, when the analysis was adjusted for baseline plasma HIV RNA level, the rates of CD4(+) T cell decline per year for the HIV-1 and HIV-2 cohorts were similar (a rate increase of approximately 4% per year for each increase in viral load of 1 log(10) copies/mL). Therefore, plasma HIV load is predictive of the rate of CD4(+) T cell decline over time, and the correlation between viral load and the rate of decline appears to be similar among all HIV-infected individuals, regardless of whether they harbor HIV-1 or HIV-2.

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We evaluated the performance of three HIV-1 RNA quantitation methods (Amplicor HIV-1 MONITOR-1.0, NASBA, and Quantiplex HIV RNA 2.0 [branched DNA (bDNA)]) using plasma specimens (N = 60) from individuals from Asia and Africa infected with one of three HIV-1 subtypes (A, Thai B [B'] or E; N = 20 each). Our results demonstrate that of the 20 subtype A specimens, 19 were quantifiable by the bDNA assay compared with 15 by the MONITOR-1.0 and 13 by NASBA. Of those quantifiable, the mean log10 difference was 0.93 between bDNA and MONITOR-1.0 and 0.46 between bDNA and NASBA. For subtype B' specimens, the correlation among methods was better with only 2 specimens missed by NASBA and 3 by the bDNA assay. However the missed specimens had viral burden near the lower limit (1000 copies/ml) for these assays. For the 20 subtype E specimens, MONITOR-1.0 and NASBA quantified RNA in 17 and 14 specimens, respectively, as compared with 19 specimens quantified by the bDNA assay. The correlation among different assays, especially between bDNA/NASBA and MONITOR-1.0/NASBA, was poor, although the mean log10 difference for subtype E specimens was 0.4 between bDNA and MONITOR-1.0 and only 0.08 between bDNA and NASBA. The addition of a new primer set, designed for non-B HIV-1 subtypes, to the existing MONITOR assay (MONITOR-1.0+) resulted in RNA detection in all 60 specimens and significantly improved the efficiency of quantitation for subtypes A and E. Our data indicate that HIV-1 subtype variation can have a major influence on viral load quantitation by different methods. Periodic evaluation and modification of these quantitative methods may be necessary to ensure reliable quantification of divergent viruses.

To describe prevalence of antiretroviral (ARV) drug-resistant HIV-1 strains among patients with a history of earlier treatment with ARV drugs in Abidjan, Côte d'Ivoire, we determined mutations that confer HIV-1 ARV drug resistance by sequencing the viral reverse-transcriptase and protease genes derived from plasma viral RNA of 68 individuals consecutively enrolled in the Joint United Nations Program on AIDS Drug Access Initiative (UNAIDS-DAI) with a history of earlier ARV drug treatment in Abidjan between August 1998 and April 1999. Phenotypic ARV drug resistance was assessed using a recombinant virus assay. Primary mutations associated with ARV drug resistance to at least one of the reverse-transcriptase inhibitors or protease inhibitors were detected in 39 (57.4%) of the 68 patients. The prevalence of mutations associated with resistance to ARV drugs was: 29 (42.6%) to zidovudine, 10 (14.7%) to lamivudine, one (1.5%) to didanosine, one K103N mutation (associated with resistance to delavirdine, nevirapine, and efavirenz), one Y181C mutation (associated with resistance to delavirdine and nevirapine), two to both indinavir (M46I/L and V82A) and saquinavir (G48V and L90M), and one each to ritonavir (V82A) and nelfinavir (D30N). Phenotypic resistance to at least one nucleoside reverse transcriptase inhibitor (RTI) was seen in 25 (39.7%) patients, to nonnucleoside RTIs in 5 (8%) patients, and to protease inhibitors in 4 (6%) patients. The high prevalence we observed in this study may limit in future the effectiveness of ARV programs in the Côte d'Ivoire.