A $5 dipstick test may offer a practical solution for rapidly detecting Zika and dengue without the risk of cross-reactivity. A study in Science Translational Medicine describes how scientists used this approach to differentiate between and identify flaviviruses in human serum samples from Central and South America and India.

Cross-reactivity among flaviviruses poses a conundrum because the viral protein, NS1, is very similar among dengue and Zika viruses, which are transmitted by the same types of mosquitos. “Among the four dengue serotypes and with Zika, they are over 70% similar in sequence, making it challenging to find antibodies that do not cross-react,” study co-author Kimberly Hamad-Schifferli, PhD, an associate professor with the University of Massachusetts Boston’s department of engineering, told CLN Stat. Despite their similarities, only Zika has been associated with serious birth defects.

The dipstick test developed by Irene Bosch, PhD, and colleagues uses antibodies in pairs that recognize the NS1 biomarker of interest in dengue and Zika. “One antibody is immobilized onto a paper strip, and the other is bound to gold nanoparticles. If the biomarker is present, then red nanoparticles will accumulate at the test area. This results in a visual red spot,” Hamad-Schifferli explained. Each test has a dipstick for each of the different flavivirus diseases.

Investigators were able to find noncross-reactive antibodies by screening a large number of them, which was very labor intensive, she added. Overall, they tested 300 Zika combinations and 726 dengue combinations to identify antibody pairs and successfully distinguish between the four dengue serotypes and Zika viruses.The test operates similar to a pregnancy test, taking 10 to 15 minutes to provide an answer. Users add a biological fluid such as blood serum that wicks through the paper strip via capillary action, producing the results. “It’s self-contained in that it does not require any additional special reagents and can be operated by a nonexpert. In addition, it does not require any power for operation or readout,” according to Hamad-Schifferli.

Next steps are to work on novel ways of readout by engineering the nanoparticle properties, she said. “In addition, we are also applying the test to biomarkers of other closely related diseases. Currently we are taking steps towards commercialization,” Hamad-Schifferli said. The Massachusetts Institute of Technology currently has the patent applications for this technology. Commercial tests may be available in about a year or so, Hamad-Schifferli said.