Background: Virus load (vl) measurements are crucial to understanding HIV pathogenesis and assessing response to treatment, and are among the best markers of HIV prognosis. Furthermore, immune-based therapies, when available, will require vl testing to assess efficacy. However, there are no commercial kits capable of measuring both HIV-2 and HIV-1 vls, while the high price of available HIV-1 assays are beyond the reach of most laboratories in the developing world. Therefore, there is the need to develop reliable and cheaper vl assays for both HIV-1 and HIV-2. We report here on a simple in-house vl assay that we have developed and evaluated, and now use routinely in our laboratory.

Methods: Our assay involves three main stages: 1) extraction of HIV RNA from patients’ (pts) plasma using guanidinium; 2) RT-PCR; and 3) detection of target HIV DNA by enzyme-linked oligonucleotide assay (ELONA). External standards with known RNA copies/ml are used to generate a standard curve from which RNA copies in pts plasma samples are extrapolated. The HIV-1 arm of the assay was evaluated with Roche Amplicor HIV-1 RNA kit version 1.5, while the HIV-2 arm was evaluated by limiting dilution analysis. We have conducted two separate studies using our in-house assay: 1) perinatal HIV transmission in relation to vl of infected pregnant mothers, and 2) pts survival in relation to baseline vl.

Results: Results obtained using our assay were comparable with those obtained using the Roche Amplicor kit, and our assay was about fives times cheaper. In the perinatal transmission study, HIV-1 infected mothers had a mean vl of 15,100 copies/ml and a transmission rate of 25%, while HIV-2 infected mothers had a mean vl of 410 copies/ml and a 4% transmission rate. In the survival study, vl was an independent predictor of death in pts with HIV-2, while both vl and CD4 count were important predictors of survival in HIV-1 infected pts.

Conclusions: Our results have shown that we have a vl assay that is comparable to the Roche commercial kit, but much cheaper. Its potential use in monitoring the effectiveness of anti-retroviral treatment programmes and in therapeutic vaccine evaluation cannot be over-emphasised, particularly in resource-poor settings.