Development of a Longitudinal, Human Virome-Wide Serological Assay
The average adult is infected with around 10 new viruses per year, each resulting in circulating antibodies that remain in the blood long after the infection is eliminated from the body. Monitoring this immune memory over time provides insight into the progression and level of protection against the different viruses an individual has encountered, and improves the understanding of host immune capacity and the course or onset of chronic disease. The MyImmunity project applies this principle at a population level, allowing us to track how immunity against diverse viruses evolves over time across a population. This is accomplished through the assay of antibodies from weekly dried blood spot (DBS) samples, collected from volunteers over a period of 10 weeks, against a library of 244,000 peptides that covers all viral species that can infect humans. These libraries consist of peptides barcoded by the DNA sequence that generated them, and are used in serological assays to assess what peptides bind to the antibodies in each DBS sample, which are read out by DNA sequencing. Although DBS samples enable longitudinal analysis that is impractical using traditional clinical sampling, one hurdle in applying this technology is that the conditions each DBS encounters before we receive them may result in degradation of the antibodies contained in them. We tested a range of temperatures (25°C, 37°C, 60°C) in triplicate under both dry and humid conditions to identify factors contributing to degradation. We found that DBS stored at 60°C in both dry and humid conditions resulted in a lower signal for the expected peptides than those stored at either 25°C or 37°C. Humidity had no additional detrimental effect. We conclude that storage temperatures above 37°C are not ideal for the DBS, and create identifiable trends in the peptide signal data indicative of antibody degradation.