Immunochromatography assays to diagnose tropical viral pathogens using gold nanoparticles

Abstract

Immunochromatography assays are ideal candidates for diagnosis of disease in remote areas, due to their low cost and rapid readout. Moreover, they can be stored at relatively high temperatures, and do not require electric power, specialized personnel, equipment or reagents. We use those devices to diagnose viral mosquito-borne tropical diseases that have caused major epidemics and hospitalization in the last years. By allowing mobile phone readability of the diagnosis results, we enable real-time epidemiologic data on the spread of the disease. lmmunochromatography assays use capillary flow and the accumulation of ligand-coated nanoparticles to detect the presence of target proteins. We build multiplexed diagnostics that allow the detection of the four serotypes of Dengue and Zika, and validate the performance of these diagnostics by using patient samples from endemic areas from the Americas and India. Moreover, we build a multiplexed diagnostic that can detect Dengue, Zika and Chikungunya by using a low volume of patient sample. In order to provide a rapid response to epidemics, lateral flow immunoassays need to be rapidly tested and manufactured. However, years of research are necessary to identify, screen and test disease-specific antibody pairs. To provide a faster response to outbreaks, we explore cross-reactive antibodies developed against a related pathogen. To avoid nonspecific signal from the related pathogens, gold nanoparticles of different colors are combined with cross-reactive antibodies of different affinities and used in order to distinguish between the two infections as well as co-infections. In this context, I present an Ebola and Marburg diagnostic and a Dengue and Zika diagnostic. Limit of detection, as well as sensitivity/specificity are critical issues in the development of rapid diagnostics; these parameters are dependent on the nature of the ligand-target pair and binding thermodynamics when attached on a surface. In this thesis, I explore strategies to increase the sensitivity and specificity of the lateral flow devices. These new, effective, fast, reliable and inexpensive lateral flow devices represent significant improvements to field detection of disease and real-time epidemiology in situations where the lack of specialized personnel, reagents or materials challenge the suitability of the standard diagnosis methods.