American researchers, including one of Indian origin, have developed a test that is sensitive enough to detect "hidden" HIV and yet is faster, less labour-intensive and less expensive than the current "gold standard" test.

HIV virus has a knack for lying dormant in immune cells at levels undetectable to all but the most expensive and time-consuming tests."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, Professor at University of Pittsburgh in the US."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," Gupta said. 

HIV spreads by infecting CD4+ T cells, which are a type of white blood cell that plays a major role in protecting the body from infection. 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.The new test that Gupta's team developed is faster, less labour intensive, and less expensive, according to the study published in the journal Nature Medicine. 

Called 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.It also requires a much smaller volume of blood, the study said."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 said.