Miranda Smith
New test uncovers (more) hidden HIV
Scientists from the US have announced an improved way to detect hidden HIV. The group of Professor Phalguni Gupta at the University of Pittsburgh describe a new test for measuring latent HIV. Published in Nature Medicine, the test could be used to see how effective an HIV cure strategy is.
Why is a new test needed?
With effective antiretroviral treatment, HIV can’t be detected. When treatment stops, cells with hidden HIV release virus and it quickly becomes detectable again. These cells with latent HIV are the barrier to an HIV cure. Detecting and measuring them is vital for knowing if the virus is able to rebound. The problem is that hidden virus is difficult to find and measure. The current gold standard for detecting latent HIV is very complex and time-consuming. It involves activating latent cells and measuring infection levels when they are added to non-infected cells. This test (called the quantitative viral outgrowth assay, or qVOA) detects HIV that can reappear if treatment stops, but it is not perfect. The qVOA uses a large number of cells, takes about two weeks, and only picks up a fraction of latent HIV.
How is the new test different?
The new test, called TZA, like the qVOA test detects replication-competent HIV. Replication-competent HIV means HIV that is able to cause active infection. Not all latent HIV is replication-competent, because sometimes bits of the virus are missing or defective. Replication-competent virus is the real barrier to cure. The TZA test takes latent cells activated in the lab and combines them with a cell line that glows when HIV replicates. The new test uses fewer cells, takes half the time of a qVOA, is cheaper and appears to be much more sensitive. The researchers show that the TZA assay detects up to 70 times MORE HIV than the qVOA test. This suggests that the qVOA test misses a lot of potentially dangerous latent HIV.
Study author Dr. Anwesha Sanyal. Image credit Tim Betler/UPMC
What does this all mean?
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…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. Professor Phalguni Gupta, study lead.
If someone takes part in an HIV cure trial, it’s critical to know whether the trial has worked. One way of finding out is to stop treatment and see if the virus rebounds. A better (and safer) way to evaluate a cure strategy would be to measure the remaining latent HIV. Improved detection of latent HIV is a step towards improved evaluation of cure strategies. The new TZA assay will need more validation before it can be used in trial settings, but it is a promising new tool for detecting latent HIV.
Read the media release here
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