Enhancing detection and mobile monitoring of schistosomiasis with urine-based analyte pre-concentration technology

ABSTRACT Schistosomiasis is a debilitating parasitic disease that infects over 230 million people and causes 280,000 deaths per year. New estimates of global disease burden rank schistosomiasis as the third most impactful infectious disease behind only HIV/AIDS and malaria. Therefore, over the past decade, global health organizations have renewed interest in schistosomiasis control and elimination. Efforts to reduce schistosomiasis-associated morbidities primarily involve mass drug administration (MDA) and measures for interrupting transmission (e.g., via improved access to safe water and snail (vector) control). Critical to both disease control strategies is the ability to detect infected individuals; however, because highly endemic areas often lack basic laboratory infrastructure, it is vital that monitoring be performed in the field or at the point-of-care (POC) to address the vast numbers of sites and individuals needing testing. Current disease monitoring largely depends upon microscopy techniques to identify/quantify eggs that are sporadically shed by adult worms in stool or urine. While highly specific, microscopy methods are laborious, time-consuming, inconsistent, and often have clinical sensitivities under 5%. Alternatives to microscopy include immunoassays that detect schistosome- specific antigens, such as the circulating cathodic antigen (CCA), or the circulating anodic antigen (CAA), from human urine. A POC CCA urine assay has been commercialized and used in surveillance and mapping studies, but is not sensitive enough to detect low-intensity infections, and is only reliably produced by one of the six common Schistosoma species, which limits its use to certain regions. In contrast, CAA is produced by all Schistosoma species and, unlike microscopy, is directly correlated to total worm burden for monitoring therapy response. Therefore, a CAA immunoassay is expected to significantly enhance diagnostic monitoring of schistosomiasis, but no commercially available POC-CAA assay exists. To address this unmet need, we will integrate two complementary technologies that enable ultra-sensitive POC field-testing for schistosomiasis from urine. Our collaborator, Dr. Paul Corstjens, a globally recognized schistosomiasis expert at Leiden University Medical Center, has developed an ultrasensitive Up-Converting Phosphor Lateral Flow Assay (UCP-LFA) for CAA detection. The assay has shown tremendous promise in several studies and clinical trials but still requires time- consuming and resource-intensive sample pre-concentration to reach the sensitivity required to detect the lowest-intensity infections. In parallel, Salus Discovery has developed a new technology, termed FLOW™, that expands upon the operational concepts of LFAs by enabling pre-concentration of analytes from 20 mL of urine into 100 µL prior to detection on an LFA. Recently, Salus and Dr. Corstjens' group developed the first prototype of a device that integrates FLOW urine pre-concentration with a UCP-LFA readout (FLOW-S). The FLOW-S prototype was preliminarily evaluated with a set of 30 clinical samples where it achieved 79% sensitivity and 100% specificity, demonstrating its use as a fundamentally new, POC-friendly, ultra-sensitive CAA-based assay for schistosomiasis. In this SBIR Phase 1 proposal we will build upon our success by optimizing the FLOW-S device to achieve a detection limit of 0.1 pg/mL, enabling detection of even the lowest intensity (i.e., single-worm) infections (Aim 1), and performing a clinical study with fresh urine samples (Aim 2).