A newly-developed, fast, and cost-effective dipstick test sensitively and specifically identified Zika virus and all four dengue virus subtypes without any detectable cross-reactivity. The developers of the diagnostic say that the platform could not only help with clinical diagnoses for Zika, dengue and other closely-related flaviviruses, but also be applied for emerging pathogens. While both Zika and dengue viruses are transmitted by the same mosquitoes and have similar clinical symptoms, Zika virus alone is linked to severe birth defects. A new test developed by Irene Bosch and colleagues distinguished between Zika and dengue viruses without cross-reactivity (unlike commercially available diagnostics), and also detected viral proteins at far lower concentrations (between 4 and 21 ng/ml, compared to 75 ng/ml). Materials costs for the assay amounted to roughly $5 per strip, and the scientists speculate that the price will decrease as production is scaled up. The tests detected the virus by "sandwiching" a viral protein named NS1 between membrane dipsticks coated with one anti-NS1 antibody and gold nanoparticles connected to a different anti-NS1 antibody - causing visible purple spots to appear only if the NS1 protein was present in samples. To identify antibody pairs, Bosch et al. evaluated 300 combinations for Zika virus and 726 combinations for dengue viruses. They further validated that the method was specific to purified viral proteins and serum from patients with confirmed diagnoses. Importantly, the authors note that their design approach was guided by the World Health Organization's acronym ASSURED, which describes ideal diagnostics: affordable, sensitive, specific, user-friendly, rapid, equipment-free, and delivered to those who need them.
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Journal
Science Translational Medicine