In a new test method, a single vial of blood could detect any viruses a person has ever had, enabling improved diagnosis of disease. VirScan, as the test is called, not only shows viral infections that the immune system is fighting actively, but also gives a history of an individual’s past infections.
Costing only a fraction of the cost of existing tools, $25 it also uses smaller samples of blood, researchers say. The still experimental test could someday evolve into an important research tool.
Tracking patterns of disease in various populations, helping epidemiologists contrast different segments of a region’s population, or comparig groups of people in different parts of the world would all become more precise, easier and less expensive.
“We’ve developed a screening methodology to basically look back in time and see what viruses they have experienced. Instead of testing for one individual virus at a time, which is labour intensive, we can assay all of these at once. It’s one-stop shopping.”
The test is able reveal past exposure to over 1,000 strains of viruses from 206 species.
This covers more or less the complete human “virome,” in other words, every virus known to infect people. The test works by detecting antibodies, the exceptionally specialized Y-shaped proteins that the immune system produces in response to viruses.
In trials with 569 people in South Africa, the United States, Peru, and Thailand, the blood test found that most had been exposed to about 10 species of virus. They were for the most part common viruses, such as those causing flu, colds, gastrointestinal illness and other common ailments.
People in South Africa, Peru, and Thailand, tended to have antibodies for a greater number of viruses than people in the United States.
Elledge says his team was surprised to see that antibody responses for specific viruses were surprisingly similar between individuals, with different people’s antibodies recognizing identical amino acids in the viral peptides.
“In this paper alone we identified more antibody/peptide interactions to viral proteins than had been identified in the previous history of all viral exploration,” he says.
The amazing reproducibility of the interactions enabled the team to refine their analysis and improve VirScan’s sensitivity. Elledge adds the method will continually improve as his team analyzes more samples. Their findings on viral epitopes may also have important implications for vaccine design.
Illustration: Immunoprecipitation and high-throughput DNA sequencing reveal the peptides recognized by antibodies in the sample. The color of each cell in the heatmap depicts the relative number of antigenic epitopes detected for a virus (rows) in each sample (columns). Credit: Figure from the print summary of Xu et al., “Comprehensive serological profiling of human populations using a synthetic human virome” SCIENCE, 348:1105 (5 June 2015).