Modification of the Abbott RealTime assay for detection of HIV-1 plasma RNA viral loads less than one copy per milliliter.
ABSTRACT Although commercial tests are approved for detection of HIV-1 plasma viral loads ≥ 20 copies per milliliter (ml), only one specialized research assay has been reported to detect plasma viral loads as low as 1 copy/ml. This manuscript describes a method of concentrating HIV-1 virions from up to 30 ml of plasma, which can be combined with a commercial viral load test to create a widely available, reproducible assay for quantifying plasma HIV RNA levels less than 1 copy/ml. Using this pre-analytically modified assay, samples with a known level of 0.5 copy/ml were detected in 8 of 12 replicates (mean 0.47 copy/ml; 95% confidence interval (CI) 0.14-0.81 copy/ml) and samples with a known level of 1.0 copy/ml were detected in 13 of 13 replicates (mean 1.96 copy/ml; 95% CI 1.42-2.50 copy/ml). By concentrating virus from 30 ml of plasma, HIV RNA could be measured in 16 of 19 samples (84%) from 12 of 12 subjects (mean 2.77 copy/ml; 95% CI 0.86-4.68 copy/ml). The measured viral load correlated inversely (r = -0.78; p = 0.028) with the total duration of viral suppression (viral load<40 copies/ml).
Full-textDOI: · Available from: Joseph K Wong, Jun 17, 2015
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ABSTRACT: The source, significance and optimal management of low-level viraemia during highly active antiretroviral therapy (HAART) are poorly defined. This review highlights recent observations that have implications for clinical practice. The definition of low-level viraemia remains elusive. Whereas evidence obtained with second-generation viral load assays indicates that confirmed detection of plasma HIV-1 RNA above 50 copies/ml predicts negative outcomes, third-generation assays detect HIV-1 RNA below this threshold. In patients monitored with the Abbott RealTime assay, the cutoff that should trigger confirmation of viraemia and clinical review can be revised to 40 copies/ml. Further data are needed on the cost-effectiveness of intervening when RNA detection is observed below this cutoff. Discrepancies among viral load assays prevent generalization of these observations. To further compound the issue, most patients on stably suppressive HAART show residual viraemia at around 1-10 copies/ml using research-based ultrasensitive assays. The source of residual viraemia remains controversial, but neither short nor long-term HAART intensification with antiretrovirals such as raltegravir reduces the viraemia. A transient effect of intravenous immunoglobulin has been reported, and different regimens may vary in their propensity to allow HIV-1 RNA persistence. Further studies are required to clarify the relationship between low-level viraemia and the size of proviral DNA reservoirs, and the contribution of cellular and tissue compartments and cell-to-cell spread to ongoing virus replication during HAART. Understanding the source and clinical significance of HIV-1 RNA persistence in plasma during HAART is required to guide patient care and inform the design of HIV eradication strategies.Current Opinion in Infectious Diseases 12/2011; 25(1):17-25. DOI:10.1097/QCO.0b013e32834ef5d9 · 5.03 Impact Factor
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ABSTRACT: Current real-time PCR-based HIV-1 viral load (VL) assays allow the detection of residual viraemia in antiretroviral-treated patients. The clinical outcome of HIV1 patients experiencing low-level replication (<50 cop/mL) in comparison with fully suppressed patients is currently debated. We analysed variability of 3 VL assays <50 cop/mL, and evaluated the reproducibility of viral blips <100 cop/mL. Three commercial VL assays were tested: Versant HIV-1 RNA 1.0 kPCR (Siemens), Abbott Realtime HIV-1, and Cobas Ampliprep/Cobas Taqman HIV-1 v2.0 (Roche). Ten replicates of a reference sample at 4 low target dilutions were tested to evaluate assay variability. Prospective collection of 181 clinical samples with detectable VL <50 cop/mL was used to evaluate intra-and inter-assay variability by triplicate testing. Samples from 26 patients experiencing a viral blip were retested. All assays showed substantial variability at low VL level: the coefficient of variation at 100, 50, 25 and 12 cop/mL ranged respectively from 32 to 44%, 35 to 68%, 41 to 83% and 33 to 77%. In the intra-assay evaluation of repeatability, 52.5 to 57.5% of detectable VL <50 cop/mL tested in triplicate showed at least one fully undetected result. Variability was similar in the inter-assay arm. The VL blips could only be reproduced in 19% of cases. The most recent versions of widespread commercial VL assays showed substantial variability at low levels and residual viraemia could not be consistently reproduced. Patient outcome studies comparing residual VL to full suppression are therefore biased when using commercial assays.BMC Infectious Diseases 04/2012; 12:100. DOI:10.1186/1471-2334-12-100 · 2.56 Impact Factor
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ABSTRACT: There is intense interest in developing curative interventions for HIV. How such a cure will be quantified and defined is not known. We applied a series of measurements of HIV persistence to the study of an HIV-infected adult who has exhibited evidence of cure after allogeneic hematopoietic stem cell transplant from a homozygous CCR5Δ32 donor. Samples from blood, spinal fluid, lymph node, and gut were analyzed in multiple laboratories using different approaches. No HIV DNA or RNA was detected in peripheral blood mononuclear cells (PBMC), spinal fluid, lymph node, or terminal ileum, and no replication-competent virus could be cultured from PBMCs. However, HIV RNA was detected in plasma (2 laboratories) and HIV DNA was detected in the rectum (1 laboratory) at levels considerably lower than those expected in ART-suppressed patients. It was not possible to obtain sequence data from plasma or gut, while an X4 sequence from PBMC did not match the pre-transplant sequence. HIV antibody levels were readily detectable but declined over time; T cell responses were largely absent. The occasional, low-level PCR signals raise the possibility that some HIV nucleic acid might persist, although they could also be false positives. Since HIV levels in well-treated individuals are near the limits of detection of current assays, more sensitive assays need to be developed and validated. The absence of recrudescent HIV replication and waning HIV-specific immune responses five years after withdrawal of treatment provide proof of a clinical cure.PLoS Pathogens 05/2013; 9(5):e1003347. DOI:10.1371/journal.ppat.1003347 · 8.06 Impact Factor