Enteric Pathogen Force of Infection among Children using Serology

Enteric pathogen infections are a leading cause of the global disease burden, with the largest burden among children in low-resource settings. Stool-based PCR methods have dramatically improved our ability to measure enteric infections, but the challenge of collecting stool and need for near-continuous monitoring to detect many globally important pathogens has thwarted broader use in large-scale surveillance. Large-scale, population- based surveys now regularly collect blood to monitor transmission and burden of diseases such as HIV, malaria and dengue. Broader testing of blood collected in such surveys with multiplex assays represents a new opportunity to measure enteric pathogen transmission and burden. Antibody-based measures could complement stool-based PCR testing because antibody responses remain elevated for many months after infection, thus providing more information in studies with infrequent measurements. Our team has developed multiplex bead assays that measure immunoglobulin G (IgG) response to diverse enteric pathogens. In preliminary studies we have shown that IgG levels can be used to measure heterogeneity in enteric pathogen transmission between populations. We have also shown the results generalize to pathogens that span taxa. In this application, we propose to complete a series of studies that address key next steps to advance the seroepidemiology of enteric pathogens in low-resource settings. We will conduct a longitudinal birth cohort in Ecuador that pairs high resolution, multiplex stool-based PCR infection with longitudinal, multiplex IgG and IgA measurements. Our 17- year research history at the site has documented substantial variation in enteric pathogen infection across a rural-urban gradient, making it an ideal setting for the research. The cohort will enroll 600 children from three sites across a rural-urban gradient, and measure them frequently from birth to 24 months. On the Luminex platform, we will pair multiplex PCR assessment for 15 enteric pathogens with IgG and IgA assessment in a multiplex bead assay that includes antigens to 7 enteric pathogens: Campylobacter jejuni, enterotoxigenic Escherichia coli, Salmonella enterica, Giardia duodenalis, Cryptosporidium parvum, Entamoeba histolytica, and norovirus. In Aim 1, we will use molecular and antibody-based measures to study force of infection of the enteric pathogens across a rural-urban gradient. This will represent the first broad-based comparison of seroepidemiologic measures against patent infection for enterics. In Aim 2, we will estimate enteric pathogen force of infection by applying current-status models to population-based, cross-sectional serology surveys in the region, and will benchmark the cross-sectional estimates against those obtained in the concurrent longitudinal study. In Aim 3, we will study IgG and IgA kinetics following infection for each of the 7 pathogens, and develop models to accurately predict recent infections and incidence from antibody levels measured in cross-sectional serology surveys. Completion of these aims will result in generalizable seroepidemiologic methods that have the potential to transform measurement of enteric pathogen transmission and burden in low-resource settings.