In some parts of sub-Saharan Africa, more than one in four people have HIV. However, one of the biggest problems in treating the disease is the ability to work out what stage it is at.
That’s because current monitoring tests are too slow and too expensive, meaning doctors don’t know when to administer drugs.
People living with HIV have to undergo many different types of tests: from initial diagnostic tests, which may not show results until up to six months after infection, to tests of so-called CD4 white blood cells that tell doctors when antiretroviral therapy treatment should be started, or viral load tests which monitor how much of the HIV virus is in the blood.
European researchers are currently developing a method of counting CD4 cells which requires smaller amounts of expensive antibodies than present methods, and the disposable parts of the test can be manufactured using an inkjet printer.
Low counts of CD4 cells indicate the disease progressing, so doctors need to use these tests to decide when to initiate antiretroviral therapy. In some cases, where other testing methods are not available, CD4 tests can also be used to monitor antiretroviral therapy, so that doctors can determine what type of treatment to prescribe.
‘The goal is to make it very simple,’ said Dr Markus Beck of the University of Twente in the Netherlands, who leads the INSTANTCOUNT project, which is funded by the European Research Council (ERC). The new fabrication method will mean that it is possible to produce tests in large numbers at a low cost, which can then be transported to the relevant regions. ‘The test is simple, compact and robust.’
“'More accurate and rapid assays (tests) are urgently required at low cost so that they could be applied in developing countries with a high incidence of HIV infection.'
Once the blood is taken it is allowed to flow into a counting chamber. As gel inside the chamber swells with blood, it releases antibodies which bind to the CD4 cells. After about 30 minutes, the gel is inserted into an imager which takes fluorescent pictures. The pictures pick up the CD4 cells that have bound to an antibody so that the number of CD4 cells can be determined easily.
The innovation lies in being able to print out a layer of the antibody-laced gel. ‘It’s basically like printing ink, but the ink is not to make colours,’ said Dr Beck. ‘It deposits a layer of, for example, gelatin. We need that gelatin layer in order to delay the release (of the antibodies) otherwise the samples would get washed away completely with the inflowing blood.’
Researchers on the INSTANTCOUNT project are hoping that their device will be tested on patient samples within one to three years. ‘So far we’ve only tested it with blood from healthy volunteers,’ said Dr Beck. ‘We simulated low CD4 counts by separating and re-mixing different blood components. We are planning to have some patient tests very soon.’
HIV tests for EUR 10
It can be important to test for HIV quickly, especially in the case of babies as 24 % of those born to an untreated HIV-positive mother go on to develop the disease. However, HIV-positive babies benefit greatly from immediate treatment.
The EU-funded CAPHIV project is in the early stages of developing an alternative blood test for diagnosing HIV which focuses on detecting parts of HIV proteins called antigens as opposed to HIV antibodies.
That can hurry things up as typically antibodies arrive in the patient’s bloodstream two to six weeks after initial infection, and in newborns their antibodies are often masked by their mother’s. The problem is that so-called antigen tests are usually too expensive for widespread use in many parts of the world.
However, the CAPHIV project hopes to be able to make a test that costs just EUR 10. This test is sensitive enough that the antigens don’t need to be amplified, a process that raises the cost of existing tests because cells are cultivated so that there is a larger number of them to be tested.
They’ve already built four prototypes which will be tested in the clinic in the upcoming DEMO-CAPHIV project. ‘HIV poses one of the major medical challenges in the history of humanity, with millions of individuals becoming infected each year,’ said Attila Uderszky, project coordinator of CAPHIV.
‘More accurate and rapid assays (tests) are urgently required at low cost so that they could be applied in developing countries with a high incidence of HIV infection.’
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