Dr. Anwesha Sanyal holds up two vials with HIV-infected cells that she is preparing for Pitt Public Health’s TZA test. The yellow indicates more stimulated HIV infected cells. Credit: Image courtesy of University of Pittsburgh Schools of the Health Sciences
Scientists at the University of Pittsburgh’s Graduate School of Public Health announced in Nature Medicine that they’ve created a test sensitive enough to detect “hidden” HIV, and yet is faster, less labor-intensive and less expensive than the current “gold standard” test. The new Pitt test also revealed that the amount of virus lurking dormant in people who appear to be nearly cured of HIV is about 70-fold larger than previous estimates.
HIV spreads by infecting CD4+ T cells that plays a major role in protecting the body from infection. Antiretroviral therapies to treat HIV have advanced to the point that people with HIV can have the virus so well-controlled that they could have as little as one infectious virus per million CD4+ T cells. However, the majority of HIV DNA integrated into these cells is defective, meaning it wouldn’t cause infection anyway. Once HIV therapy is working, it becomes critical to determine if the HIV DNA being detected by a test could actually create more virus and cause the person to relapse if therapy is stopped. Therefore, the test must be able to show that the virus it detects can replicate – typically by growing the virus from the sample.
To date, the best test available to do this is called a “quantitative viral outgrowth assay,” or Q-VOA. This test has many drawbacks: It may provide only a minimal estimate of the size of the latent HIV reservoir; requires a large volume of blood; and is labor-intensive, time-consuming and expensive. Gupta’s team developed a test that they call TZA. It works by detecting a gene that is turned on only when replicating HIV is present, thereby flagging the virus for technicians to quantify.
The TZA test produces results in 1 week compared to the 2 weeks needed using the Q-VOA, and at a third of the cost. It also requires a much smaller volume of blood and is less labor-intensive. “Using this test, we demonstrated that asymptomatic patients on antiretroviral therapy carry a much larger HIV reservoir than previous estimates – as much as 70 times what the Q-VOA test was detecting,” said Gupta. “Because these tests have different ways to measure HIV that is capable of replicating, it is likely beneficial to have both available as scientists strive toward a cure.”
Because of its low cell requirement, the TZA also may be useful for quantification of replication-competent HIV-1 in the pediatric population, as well as in the ymph nodes and tissues where the virus persists. http://www.upmc.com/media/NewsReleases/2017/Pages/gupta-hiv-assay.aspx
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