Active magnetic bead-linked immunoassay for the early diagnosis of West Nile virus

Since its introduction into the Western Hemisphere in 1999, West Nile virus (WNV) has spread rapidly across the entire continental United States, Canada, Mexico, Latin America, and the Caribbean in only 5 years [26-29]. It has been responsible for 19,709 confirmed infections and 785 deaths in the United States alone [26]. It is believed that WNV is still establishing its geographic distribution, suggesting that large epidemics will continue to occur during the next several years [17]. During epidemics it is essential that clinically relevant diagnostic tests are available to quickly and accurately diagnose WNV infection. Furthermore, recent findings have shown that the virus can be transmitted by blood and organ donations [189], breast feeding [85], intrauterine exposure [91], and laboratory procedures [190], emphasizing the importance of developing a rapid and accurate serological assay for diagnosing WNV infection. Currently, the IgM capture immunosorbant assay (MAC-ELISA) is the primary serological assay routinely used for laboratory diagnosis of WNV infection [182-184]. While proven to be a valuable tool for the diagnosis of WNV infection [191], the MAC-ELISA has significant drawbacks that limits the assay's usefulness. It is time consuming, requiring 2-3 working days to yield results, requires a lot of consumables, and is expensive [182]. Therefore, the advent of a more rapid, less expensive, yet equally sensitive test to replace the MAC-ELISA would be of great benefit.; This work describes an active magnetic bead-linked immunoassay on protein microarrays to detect WNV-specific IgM. The approach exploits a conceptually new immunoassay procedure in which slow diffusion-controlled reactions are replaced with active delivery of analytes via the application of an electric field to specific probe molecules immobilized and patterned onto a membrane surface in the form of a microarray [192]. The array surface is then scanned by magnetic beads functionalized with probe molecules that have affinity for the bound molecule of interest [193]. This assay is more advantageous than the current MAC-ELISA for detecting WNV infection due to a significant reduction in assay time and cost yet still maintaining sensitivity. Compared to the MAC-ELISA, this new diagnostic assay had 100% sensitivity while taking only 15 minutes to yield results instead of 3 days required for the MAC-ELISA. The new diagnostic also cost approximately cost 8 times less per test than the MAC-ELISA. This new diagnostic assay can be used to aid physicians and public health workers in the management of epidemics caused by WNV as well as be used in seroepidemiologic studies, and to evaluate blood and organ donations.