A Microchip CD4 Counting Method for HIV Monitoring in Resource-Poor Settings

Abstract

BackgroundMore than 35 million people in developing countries are living with HIV infection. An enormous global effort is now underway to bring antiretroviral treatment to at least 3 million of those infected. While drug prices have dropped considerably, the cost and technical complexity of laboratory tests essential for the management of HIV disease, such as CD4 cell counts, remain prohibitive. New, simple, and affordable methods for measuring CD4 cells that can be implemented in resource-scarce settings are urgently needed.Methods and FindingsHere we describe the development of a prototype for a simple, rapid, and affordable method for counting CD4 lymphocytes. Microliter volumes of blood without further sample preparation are stained with fluorescent antibodies, captured on a membrane within a miniaturized flow cell and imaged through microscope optics with the type of charge-coupled device developed for digital camera technology. An associated computer algorithm converts the raw digital image into absolute CD4 counts and CD4 percentages in real time. The accuracy of this prototype system was validated through testing in the United States and Botswana, and showed close agreement with standard flow cytometry (r = 0.95) over a range of absolute CD4 counts, and the ability to discriminate clinically relevant CD4 count thresholds with high sensitivity and specificity.ConclusionAdvances in the adaptation of new technologies to biomedical detection systems, such as the one described here, promise to make complex diagnostics for HIV and other infectious diseases a practical global reality.

Size-Based Separation of Particles and Cells Utilizing Viscoelastic Effects in Straight Microchannels

“…[4][5][6] Microfluidic systems have been proven to be promising tools for particle/cell manipulation with higher sensitivity and accuracy than their macroscale counterparts. The last decade has seen extensive development of microfluidic approaches for particle/cell manipulation that resort to immunocapture, 7 externally applied physical fields, [8][9][10][11][12][13][14][15][16][17][18] microfiltration, 19,20 gravitational sedimentation, 21 or deterministic lateral migration. 22,23 More recently, cross-streamline migration induced by the hydrodynamic effects of carrier media, such as inertia 24,25 and viscoelasticity, 26,27 has shown its promise for effective particle/cell manipulation without need of labeling and external force fields.…”

High throughput genomic and proteomic technologies in the fight against infectious diseases

“…However, the rapid progress in genomics and proteomics and the significant breakthroughs in innovative technologies are creating significant opportunities for the expansion of this field. Promising technologies that are entering the market or are at the late stages of development include: magnetic beads for enrichment of nucleic acids or antigens; isothermal nucleic acid amplification techniques; nanobiosensors; hand-held microfluidic devices enabling multiplex detection of infectious diseases; and robust and costeffective optical instruments for the detection of fluorescent signals, enabling an increase in sensitivity of POC tests [51,52,53,54,55,56,57,58]. The list of tests waived by the Clinical Laboratory Improvement Amendments (CLIA) can be found at http://www.cms.hhs.gov/CLIA/downloads/waivetbl.pdf.…”

HIV Diagnostics: Challenges and Opportunities

“…Antibody, antigen, nucleic acid and cell-counting assays that require multiple reagents, capture molecules, fluid handling and detection (e.g., fluorescence, surface plasmon resonance, surface-enhanced Raman scattering, mass spectrometry, electrophoresis and electrical conductance) modalities can be supported by the devices [115][116][117][118][119][120][121][122]. The challenge of ART monitoring was highlighted previously and there are many MLoCs in development that measure CD4 + T -cell counts out in the field without the need for sophisticated laboratory infrastructures [33,36,115,[123][124][125]. Rapid NAT assays for viral load determination is advancing, but continues to face problems with complexity [107].…”