Wastewater as a back door to serology?

Wastewater surveillance is a powerful tool for monitoring the prevalence of infectious disease in urban populations, with predictive value for upcoming increases in cases and hospitalizations. The approach primarily used in disease surveillance has been to measure the number of viral copies detected in wastewater for a study area of known population, and systems for wastewater monitoring have been put in place worldwide during the SARS-CoV-2 pandemic. However, the potential to measure other biomarkers such as proteins and metabolites in wastewater has not been fully explored. Here we develop an approach to determine antibody optical density and titer measurements from wastewater. We measured abundance of anti-SARS-CoV-2 spike IgG and IgA from typical fresh samples of community wastewater, and from a collection of frozen samples dating from 2020-22. The assay described can be performed with readily available commercial reagents, at a moderate per-sample cost, facilitating non-invasive population level immune surveillance. Our findings demonstrate the feasibility of indirect serological surveillance through wastewater for population level monitoring, and the protocol described will enable the collection of larger data sets and development of models that can be leveraged to anticipate public health needs.