Microfluidic CD4+ and CD8+ T Lymphocyte Counters for Point-of-Care HIV Diagnostics Using Whole Blood

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Science Translational Medicine  04 Dec 2013:
Vol. 5, Issue 214, pp. 214ra170
DOI: 10.1126/scitranslmed.3006870

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Tiny T Cell Counter for HIV

The amount of CD4 and CD8 T cells in a blood sample can tell a doctor the status of the patient’s immune system and HIV infection. Current methods of counting aren’t always available in resource-poor settings, such as Sub-Saharan Africa, so Watkins et al. created a microfluidic chip for these point-of-care (POC) settings, which incorporates all steps of sample preparation and accurate T cell counting.

The microfluidic differential T cell counter is based on the Coulter counter principle: In the device, cells are flowed through a tiny pore that has a current passing through it; the cell, which doesn’t conduct electricity, then blocks the current and causes a “spike” in signal. The number of spikes told Watkins et al. how many cells traveled through the pore. The device also integrated sample preparation and cell selection. Red blood cells were lysed and removed from the sample, leaving primarily white blood cells (including T cells). Antibodies decorated the microfluidic channels, to capture the population of choice—either CD4 or CD8 T cells. Thus, by obtaining a total cell count at the beginning and a final count at the end, the authors were able to quantify the number of T cells in the sample. Blood samples from HIV-infected donors and healthy volunteers were tested and compared to the gold standard, flow cytometry. Watkins and colleagues found that their differential T cell counter worked as well as flow cytometry in counting CD4+ and CD8+ T cells, thus suggesting that it is a viable platform for tracking HIV infection.

Unique to this device is the ability to monitor not only CD4 cells but also CD8 T cells, which can give a more complete picture of infection. By integrating all steps of POC detection—sample preparation, purification, and analysis—and costing less per test than certain flow cytometers, it is possible that this device will be useful in resource-limited settings. Nevertheless, more testing on patients over time will be necessary to determine the device’s clinical utility.

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