Development and optimization of self-collected, field-stable, saliva-based immunoassays for scalable epidemiological surveillance of pathogen-specific immunity

Serological surveillance is fundamental to infectious disease research and informed public-health decision-making. Immunoassays used in the study of pathogen-specific immunity have historically relied on the collection of venous blood. While critical for many public-health applications, this sample collection method is invasive and resource-intensive. The costs and logistical barriers associated with venous blood collection are exacerbated in resource-limited regions, and the shift to less invasive sampling methods would increase sample availability for pathogen surveillance and study of pathogen-specific immunity. To this end, we have developed and optimized a self-collected, saliva-based immunoassay capable of quantifying pathogen-specific antibody binding in saliva samples. Using samples collected from geographically and epidemiologically diverse regions of the world, we compared antigen-specific IgG levels in paired plasma and saliva samples. We observed that levels of IgG against multiple pathogens of public health concern-including SARS-CoV-2 and dengue virus-were highly correlated in plasma and swab-collected saliva. In addition, the decay of maternally derived antibodies in saliva samples collected from infants was readily observed using this immunoassay, demonstrating the assay's sensitivity and potential for use in measuring antibody kinetics. We posit that this assay represents a climate-stable, non-invasive tool that can aid in the surveillance and study of pathogen-specific immunity across a broad range of public-health indications. IMPORTANCE: Traditional serological surveillance relies on venous blood collection, which is invasive, resource-intensive, and particularly burdensome in low-resource settings. To address these limitations, our team has developed and validated a self-collected, saliva-based immunoassay for quantifying pathogen-specific antibody levels. Testing paired plasma and saliva samples from geographically diverse populations, the authors found that IgG levels against SARS-CoV-2 and dengue virus were highly correlated between the two sample types. The assay was sensitive enough to detect the decay of maternally derived antibodies in infant saliva, demonstrating its utility for tracking antibody kinetics over time. The authors conclude that this non-invasive, climate-stable platform offers a practical alternative for broad pathogen surveillance and immune monitoring across a variety of public health contexts.