Applications
Plasma Viral Load Across HIV Research Programs
Standard and ultrasensitive plasma HIV-1 RNA measurements support distinct but complementary questions across clinical and translational research.
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Molecular & Genomic Testing
HIV Reservoir & Virology
Immunology
Sample Processing & Biobanking
Therapeutic Modalities
Measure HIV-1 plasma RNA at the level your study requires—from clinical monitoring and protocol-defined rebound to residual viremia below the standard reporting range.
Upon initiation of effective antiretroviral therapy (ART), plasma viral load declines in distinct phases: rapid decay of circulating virus, decay of productively infected CD4+ T lymphoblasts, and decay of chronically infected cells, at which point plasma viral load becomes undetectable by standard clinical assays. For routine monitoring of people with HIV (PWH) on ART, standard clinical assays are sufficient to confirm stable suppression of viral replication.
Assays capable of detecting single copies of residual plasma HIV-1 RNA revealed a fourth phase: viremia persists in most PWH despite effective ART, with a half-life on the order of a decade. The source is likely long-lived cells that continually or intermittently express virus, which in most PWH does not result in ongoing rounds of replication. While residual viremia is not a direct measure of latent reservoir size, its level likely reflects the number of persistently infected cells and the transcriptional and translational state of the proviruses they carry. Many translational studies and clinical trials therefore track residual viremia over time to understand latent reservoir dynamics or evaluate novel therapeutics targeting latent HIV-1.
Accelevir offers both levels of sensitivity on the same automated platform in our CAP-accredited, CLIA-certified laboratory in Baltimore, Maryland, under an externally audited, company-wide quality management system. A study can move between the two levels without introducing a platform change into its dataset.
Clinical monitoring + residual viremia
We perform this clinical test on the Hologic Panther system under our HHS certificate of CLIA accreditation for high-complexity molecular testing, using Accelevir standard operating procedures and manufacturer controls.
This is the appropriate test for participant eligibility screening, routine on-study monitoring, confirmation of virologic suppression, protocol-defined rebound detection during treatment interruption, and any endpoint requiring a clinical-grade result.
Sample specification: See the manufacturer’s instructions for use for detailed specifications.
Many studies employ both. Standard testing establishes and confirms suppression and detects protocol-defined rebound, while the ultrasensitive assay resolves what is occurring beneath the clinical threshold at defined study timepoints. Performing both in one laboratory on the same platform removes a source of cross-assay variability that is otherwise difficult to account for in analysis.
A coordinated testing plan can use standard viral load to define suppression and rebound while reserving ultrasensitive measurement for the study timepoints where residual viremia carries the most scientific value.
Standard and ultrasensitive plasma HIV-1 RNA measurements support distinct but complementary questions across clinical and translational research.
Residual viremia measured before interruption is among the better-characterized correlates of rebound timing, particularly in early-treated individuals. A transition to undetectable residual viremia following therapeutic intervention may help identify individuals more likely to experience delayed rebound. Standard clinical viral load then defines rebound against the protocol threshold.
Effective latency reversal is expected to produce a transient increase in plasma HIV-1 RNA. For most single agents evaluated to date, any increase falls at or below the detection limit of standard clinical assays, which is part of why the clinical trial record has been difficult to interpret. An ultrasensitive endpoint can resolve the effect.
Where the question is whether an intensified or novel regimen reduces ongoing virion production below what current ART achieves, residual viremia is the endpoint. Standard clinical viral load cannot address it because both arms are undetectable.
Longitudinal residual viremia can be measured alongside reservoir size in participants who remain clinically suppressed throughout the study.
Ultrasensitive testing supports characterization of elite controllers, post-treatment controllers, and participants in extended remission, in whom the clinically relevant differences fall below the standard reporting range.
Ultrasensitive assays have been applied to characterize low-level viremia in breakthrough infections identified in PrEP trials, where standard clinical testing can be ambiguous.
Higher residual viremia measured before treatment interruption has been associated with faster time to rebound in several cohorts, with the strength of that association varying by timing of ART initiation. When considered together with IPDA® quantification of intact proviruses and sensitive measurements of cell-associated HIV-1 RNA, residual viremia is an important data point for understanding or predicting viral rebound dynamics.
Persistent HIV-1 is a comprehensive term encompassing all forms of integrated proviral DNA that persist for years despite ART. The landscape of persistent proviruses in each infected individual is both diverse and dynamic, and it can be differentiated by genomic fidelity, the ability to be expressed and replicate, and transcriptional state.
Because no single measurement resolves all these dimensions, quantifying changes across several of them is central to HIV cure research and clinical development. Residual viremia is most informative alongside cell-associated RNA and intact proviral DNA, which together help distinguish a reservoir that has become smaller from one that has become less transcriptionally active.
A single-copy assay is an ultrasensitive method for quantifying HIV-1 RNA in plasma at concentrations below the reporting range of standard clinical viral load tests. These assays are used to measure residual viremia in PWH on suppressive ART, in whom clinical tests report virus as not detected.
Earlier assays concentrate virus from a large plasma volume by ultracentrifugation before amplification. The 9-replicate approach instead performs nine independent replicate measurements of the same specimen on an automated platform, deriving concentration by Poisson modeling of positive and negative replicates. It is automated, offers higher throughput, and reproduces more consistently across performing laboratories.
Performance characteristics were established through our analytical qualification, and a qualification report is provided to groups conducting clinical trials on request. We prefer to discuss specific figures in the context of a study design, since the sensitivity that matters in practice depends on input volume and how the result will be used.
Standard clinical viral load using the Hologic Aptima HIV-1 Quant Dx assay is run as a CLIA test under our HHS certificate of CLIA accreditation. The ultrasensitive 9-replicate assay is offered as an analytically qualified assay service to support research and clinical trials.
5 to 6 mL of plasma, frozen and stored at or below -80°C. For standard clinical viral load, see the manufacturer’s instructions for use.
Higher residual plasma viremia measured before treatment interruption has been associated with faster time to rebound in several cohorts, with the strength of the association varying by timing of ART initiation. It is best treated as one input among several, since no single virologic biomarker reliably predicts rebound or remission at the individual level.
Yes. The underlying Aptima test targets two regions of the viral genome and has validated cross-subtype performance, which was among our reasons for selecting it.
Yes. Plasma and cell-based assays are performed in one laboratory under a single quality system, which means one shipping arrangement, one project manager, and one integrated report.
Coco SB, Stone M, Deng X, et al. Comparison of manual and automated ultrasensitive assays for residual HIV-1 in plasma from individuals on suppressive antiretroviral therapy. Journal of Clinical Microbiology. 2025;63(12):e00995-25.
Manufacturer information and instructions for use for the Aptima HIV-1 Quant Dx assay.
Baltimore, Maryland · CAP/CLIA-certified laboratory · One quality system