CD4 cells, one of the white blood cell types that HIV attacks, serve as a sort of bellwether for the progression of an HIV infection. A patient’s CD4 cell values help a physician determine their risk for specific opportunistic infections, evaluate if the patient should be placed on anti-retrovirals, and help indiciate if the treatment provided is effective. In other words, knowing an HIV positive patient’s CD4 cell values is more or less critical to efficient and proper treatment.
The current method of counting CD4 involves flow cytometry, a process where a big expensive ($50 – 100K+) machine shoots a laser at a thin stream of fluid containing cells and counts them. It works, it’s accurate, but it’s expensive and most people in the developing world don’t have access to such machines.
A new technology, pioneered by Daktari Diagnostics, a company out of Arlington, MA, is set to enter clinical trials next month (July) and has promise to provide an inexpensive, point of care, CD4 cell counting machine for the developing world. It works via principles of microfluidics and has tiny channels that shuttle small blood samples over detectors. The detectors at the end of these channels, In addition to using antibodies that capture CD4 cells, make use of an electrical contact that detects the impedance of the cell. Impedance is, roughly, a measurement of the resistance of an object to the flow of electricity through it, and cells have unique impedance fingerprints. CD4 cells, for example, have a different impedance than red blood cells. This allows the detector to determine how many CD4 cells are in the sample.
The device will be low cost and will not need pipetting, labels, or any reagents at all. It’s a dramatic shift in CD4 counting and, if the trials are successful, is lined up to have a broad impact in the treatment of HIV.
Website: Daktari Diagnostics…
PloS paper: A Microchip CD4 Counting Method PLoS Med 2(7): e182. doi:10.1371/journal.pmed.0020182