An HIV Viral Load Assay for the Point-Of-Care

项目总结

Project Summary HIV remains a global health crisis: more than 1.2 million people died from the disease in 2014. While there has been significant progress in the last ten years—more than 15 million people currently receive effective antiretroviral therapy (ART) worldwide—our ability to monitor and provide high-quality care to HIV/AIDS patients is still limited, in part, by the available diagnostics tools. High-quality diagnostic tools are available in the U.S. and developed nations. However, while the advent of rapid HIV diagnostic tests (RDTs) has catalyzed an increase in case finding rates—ultimately increasing the number of people on ART—, low- and middle- income countries still suffer from the lack of simple, affordable diagnostic tests to monitor treatment efficacy, by measuring the amount of circulating virus. Determining viral load – the count of virions in the blood – is critical to the determination of treatment failure, due to either drug-resistant strains of virus or patient non-compliance. Viral load testing is also critical to diagnosing infants, for whom antibody tests are not sufficient. Most molecular biology-based tests (generally using PCR) are, to-date, complex and out of reach in most global-health settings. The Daktari HIV VL test will build upon Daktari's existing platform of POC diagnostic tests, which are designed for global health environments: rugged, portable, battery-powered, and with built-in connectivity for secure data transmission. Specifically, the Daktari HIV VL test will be based on Daktari's ViPr platform, designed to detect circulating proteins and virions directly from whole blood. The test requires a small volume of whole blood, which can be drawn via fingerstick by a minimally-trained healthcare worker, and returns results in 30 minutes, allowing clinical decisions to be made immediately. All the necessary sample preparation steps are incorporated into the automated assay, eliminating hands-on steps for the user. The first product in the Daktari ViPr platform is a Hepatitis C (HCV) Viral Load Test, which is well into the development phase. The principle of operation of the HIV Viral Load is analogous to that of the HCV product. First, HIV virions are extracted from whole blood using magnetic particles, which concentrate the purified virions into a small volume. Next, the virions are treated with lysis buffer to release the target analyte (p24 protein), and the amount of released p24 protein is quantified using a sandwich immunoassay that employs silver nanoparticles as the label. Finally, the amount of silver bound is measured using anodic stripping voltammetry. At this time, we have finished the proof-of-concept work to de-risk the program (ability to pull-down HIV virions from blood at high efficiency and a 1 fM limit of detection for p24) and have demonstrated feasibility of detecting and quantifying HIV virions from HIV samples. The HIV VL program is ready to enter the development phase. In this Direct-to-Phase-II proposal, we will first optimize HIV-specific reagents and will combine all assay steps to show that the assay provides the required limit of detection of 1,000 copies/mL when starting from whole blood samples. Next, we will integrate the HIV VL assay into the Daktari ViPr platform (cartridge and instrument). Finally, we will evaluate performance of the integrated HIV ViPr Viral Load system in a small field study at our Kenyan site. The final deliverable of this Phase II program is a prototype HIV Viral Load system capable of quantification of HIV viral loads directly from 50 µL of whole blood and with > 99% sensitivity to detect viral loads > 1,000 copies/mL, and a > 5% CV at 5,000 copies/mL.