A test which rapidly detects the presence of Zika virus in blood has been developed by researchers at Washington University in St. Louis.
Current Zika testing means a blood sample needs to be refrigerated and shipped to a medical center or laboratory, delaying diagnosis and possible treatment. The new technology has not yet been produced for use in medical situations, but the test’s results can be determined in minutes.
Not only that, but the materials required for the test do not require refrigeration and may be applicable in testing for other emerging infectious diseases.
One of the reasons such a test is needed, researchers say, is that often people infected with Zika don’t know they’re infected. Even though symptoms include fever, joint pain, muscle pain and rash, many people don’t feel ill after being bitten by an infected mosquito.
Testing is especially vital for pregnant women because Zika infection can cause congenital Zika syndrome, which contributes to several neurologic problems in the fetus or newborn infant.
No False Positives
Researchers from Washington University School of Medicine and the School of Engineering & Applied Science tested blood samples taken from four people who had been infected with Zika virus and compared it to blood from five people known not to have the virus.
Blood from Zika-infected patients tested positive, but blood from Zika-negative controls did not. The assay produced no false-positive results.
“Zika infection is often either asymptomatic or mildly symptomatic. The most effective way to diagnose the disease is not to wait for people to develop symptoms but to do population screening,”
said Evan D. Kharasch, MD, PhD, who is one of the study’s three senior investigators. The strategy requires inexpensive, easy-to-use and easy-to-transport tests.
Qisheng Jiang (left) works with senior author Jerry Morrissey, PhD. Credit: James Byard
Kharasch collaborated with Srikanth Singamaneni, PhD, an associate professor of mechanical engineering & materials science, and Jeremiah J. Morrissey, PhD, a research professor of anesthesiology, to create the test. It uses gold nanorods mounted on paper to detect Zika infection within a few minutes.
“If an assay requires electricity and refrigeration, it defeats the purpose of developing something to use in a resource-limited setting, especially in tropical areas of the world,” said Singamaneni. “We wanted to make the test immune from variations in temperature and humidity.”
The test takes advantage of a protein produced by the Zika virus that causes an immune response in infected individuals.
The protein is attached to tiny gold nanorods mounted on a piece of paper. The paper then is completely covered with tiny, protective nanocrystals. The nanocrystals allow the diagnostic nanorods to be shipped and stored without refrigeration prior to use.
To use the test, a technician rinses the paper with slightly acidic water, removing the protective crystals and exposing the protein mounted on the nanorods. Then, a drop of the patient’s blood is applied. If the patient has come into contact with the virus, the blood will contain immunoglobulins that react with the protein.
Nanorods are a type of nanoscale object. Each of their dimensions range from 1–100 nm. The researchers estimate that the cost of the gold used in each test would be 10 to 15 cents.
“We’re taking advantage of the fact that patients mount an immune attack against this viral protein,” said Morrissey. “The immunoglobulins persist in the blood for a few months, and when they come into contact with the gold nanorods, the nanorods undergo a slight color change that can be detected with a hand-held spectrophotometer.”
As other infectious diseases emerge around the world, similar ideas could potentially be used to create tests to detect the presence of viruses that may become problematic, the researchers suggest.