When is someone “cured” of HIV? If there is such a state reachable with drug therapies, how can a doctor tell? The problem stems from HIV’s tendency to hide dormant inside of immune cells - CD4+ T cells specifically - that make remaining viruses leftover after antiviral treatment difficult to detect.
From the University of Pittsburgh Schools of the Health Sciences, researchers have published a new study in the journal Nature Medicine describing their new test design for detecting dormant HIV.
"Globally there are substantial efforts to cure people of HIV by finding ways to eradicate this latent reservoir of virus that stubbornly persists in patients, despite our best therapies," said senior author Phalguni Gupta, PhD. "But those efforts aren't going to progress if we don't have tests that are sensitive and practical enough to tell doctors if someone is truly cured."
The existing test most experts rely on is the “quantitative viral outgrowth assay” or “Q-VOA.” Its shortcomings? Q-VOA requires a large volume of blood, is labor-intensive, time-consuming, and expensive, and the estimate the test provides usually doesn’t tell the whole story.
The Pittsburgh researchers instead offer the new “TZA” test to detect dormant HIV, which improves upon virtually all of Q-VOA’s weaknesses. The test works by detecting activity of a unique gene that is only expressed when HIV is currently replicating. TZA produces results in one week - Q-VOA takes two - and is one-third of the cost of Q-VOA. TZA also requires a much smaller amount of blood for testing and is less labor-intensive.
Thanks to the new test, the Pittsburgh researchers discovered that the amount of dormant HIV existing in “nearly cured” people is 70 times as much as experts previously thought.
"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," Gupta explained. "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."
The new TZA test could soon be the most commonly-used test to detect specific numbers of latent HIV in the body. With these measurements made, doctors can alter an HIV patient’s treatment plan to send them on a better, more specialized path to a true “cure.”