Paper-Based Test Diagnose Zika Within 20 Minutes

Researchers at MIT have developed a paper-based test that can diagnose Zika infection within 20 minutes, offering an easy-to-use, cheap and portable test.
Researchers at MIT have developed a paper-based test
that can diagnose Zika infection within 20 minutes,
offering easy-to-use, cheap and portable diagnostics. 
Credit: Courtesy of the researchers
MIT researchers have developed a paper-based test that can diagnose Zika infection within 20 minutes. Unlike existing tests, the new diagnostic does not cross-react with Dengue virus, a close relative of the Zika virus that can produce false positives on many Zika tests.

This test could offer an easy-to-use, cheap, and portable diagnostic in countries where Zika and Dengue are both prevalent and the gold-standard test that measures viral RNA in the bloodstream is not available.

One of the biggest challenges in diagnosing Zika is that many of the tests are based on antibodies that interact with a viral protein called NS1, which is found in the bloodstream of infected patients. Unfortunately, many other viruses from the same family, known as flaviviruses, have similar versions of NS1 and can produce a false positive. Flaviviruses include West Nile virus and the virus that causes yellow fever, as well as Dengue virus.

In an effort to create a more precise diagnostic, the MIT team set out to find antibodies that would interact exclusively with NS1 protein produced by the Zika virus, as well as antibodies specific to NS1 from each of the four different strains of the Dengue virus.

To achieve this, the researchers exposed mice to Zika and Dengue viruses and then screened the resulting antibodies, in pairs, against every flavivirus' version of the NS1 protein. This allowed them to identify pairs of antibodies that react only with one version of NS1 and not any of the others.

The researchers used these pairs to create five separate tests, one for each virus. They coated strips of paper with one antibody from each pair, while the second antibody was attached to gold nanoparticles. After adding the patient's blood sample to a solution of these nanoparticles, the paper strip is dipped into the solution. If the target NS1 protein is present, it attaches to the antibodies on the paper strip as well as the nanoparticle-bound antibodies, and a colored spot appears on the strip within 20 minutes. This approach requires five test strips per sample to test for each virus, but the researchers are now working on a version that would test for all five with one strip.

They found that their results were comparable to those obtained by polymerase chain reaction (PCR) tests, which detect viral RNA in the bloodstream. PCR tests are not widely used in areas where Zika virus is found because they require trained personnel and lab equipment that are not available everywhere.

The researchers believe that their approach should also enable them to quickly develop diagnostic tests for other related viruses that might emerge in the future. They are now working on a diagnostic for the emerging Powassan virus, which is carried by the same tick that spreads Lyme disease. Powassan, found mainly in the northeastern United States and the Great Lakes region, causes a severe form of encephalitis.

The research was published in the journal Science Translational Medicine.