The objective of this proposal is to develop a new point-of-care test (POCT)?the D4 assay?for early field- detection of Ebola virus (EBOV) infection. Currently, EBOV is diagnosed by RNA detection using reverse transcriptase-polymerase chain reaction (RT-PCR). RT-PCR requires a makeshift BSL-4 grade laboratory in the field, expensive equipment, and highly trained personnel. Other POCTs, including the user-friendly lateral-flow assay (LFA), lack the sensitivity for early detection that is critical for timely intervention with the available antibody cocktail that yields 90% survival rates for patients with low viremia. Our objective is motivated by an urgent clinical need for a POCT that (1) detects EBOV infection in the field quickly and reliably, (2) requires little on-field infrastructure, (3) yields results in 30 min, and (4) matches or exceeds the performance of RT-PCR. To achieve these goals, we have designed an integrated POCT the D4 assay that has four simple steps?dispense, dissolve, diffuse, and detect that require limited handling and skill to perform. This new-frontier technology takes advantage of the presence of an unmistakable, viral secreted glycoprotein sGP that is present in the serum of infected patients very early in infection. We have generated customized monoclonal antibodies (Abs) for sGP to use in the D4 assay. The current prototype D4 assay that we have designed detects EBOV infection at least one day earlier than RT-PCR in infected monkeys and at a far lower cost than RT-PCR or LFA. In this proposal, we plan to advance our development and improve the sensitivity of the D4 assay further as well as reduce the assay time from 60 min to 30 min. Our strategy is to increase the equilibrium binding constant of our current Ab pair from ~10-9 M to ~10-11 M with antibody affinity maturation techniques and high-throughput screening of antibody pairs. The enhanced D4 assay kit will have inkjet-printed capture and detection antibodies on a protein and cell-resistant polymer brush on a glass plate encased in a passive capillarity microfluidics chip. The assay output will be fluorescence of microspots on the D4 chip. We have developed a portable handheld fluorescence detector to capture and image the spots and automatically convert them into the concentration of analytes for quantitation and uploaded to a secure server. The design will be rigorously tested and validated with samples from infected human cells and laboratory-challenged non-human primates. At the completion of this project, we will have a field-ready, user-friendly, and highly sensitive POCT that will allow healthcare workers to detect EBOV in serum, blood, or other bodily fluids in 30 min. The new design will push the current boundaries of EBOV detection and facilitate more expedient deployment of infection control and patient support measures that can yield 90% survival rates or better if implemented early in infection. Because the D4 POCT is multiplexable, it will set a precedent for broader utility beyond EBOV to diagnose many other infectious diseases.
The proposed research will develop a low-cost, easy-to-use, and highly sensitive point-of-care clinical diagnostic for Ebola virus?the D4 assay?with an antibody pair that binds with a new protein biomarker of Ebola. In this assay, a drop of blood is added to the surface of a protein and cell-resistant polymer film, which dissolves fluorescently labeled detection antibodies that are printed as ?soluble? spots that then diffuse and bind to ?stable? spots of capture antibodies. The chip is encased in a microfluidics cassette that runs the assay without user intervention and is read by a handheld detector that images the fluorescence spots and gives a result in 30 minutes.
