Test Sums Up Viral History

A new technology requires just a simple drop of human blood to provide a detailed roadmap of a person’s viral history.

Developed by the Howard Hughes Medical Institute (HHMI), Brigham and Women's Hospital (BWH), and Harvard Medical School, the VirScan method uses phage immunoprecipitation sequencing (PhIP-seq) technology to test blood for antibodies against more than 200 species of viruses known to cause infection in humans.

"VirScan is a little like looking back in time: using this method, we can take a tiny drop of blood and determine what viruses a person has been infected with over the course of many years," said Stephen Elledge, PhD, an HHMI investigator at BWH and Gregor Mendel professor of genetics and of medicine at Harvard Medical School, in a statement from BWH.

Commonly known blood tests such as enzyme-linked immunosorbent assays (ELISA) are limited in that they can only detect a singular pathogen at a time and have not been developed against all viruses. VirScan enables scientists to run a single test to determine a patient’s viral history—including viruses an individual’s immune system may be fighting currently.

The far-reaching scale of the VirScan test is what makes it unique, Elledge said. Doctors often have to guess what viruses may have infected their patients and run individual tests. VirScan’s single test has the capacity to look for nearly all viruses—even rare ones.

The hope is a simple, reproducible test such as VirScan will help researchers create new hypotheses “and understand the interplay between the virome and the host's immune system, with implications for a variety of diseases,” Elledge explained.

An article in the June 5 issue of Science describes how Elledge and his colleagues from BWH and Harvard Medical School used the VirScan method to analyze the blood of 569 individuals in the United States, South Africa, Thailand, and Peru. The researchers developed and then drew from a “library” of peptides that represented thousands of viral strains to investigate the viral histories of their test subjects.

On average, the test subjects were found to have antibodies to 10 different viral species. In at least two individuals, 84 species were found.

Factors such as HIV status, age, and geographic location caused variations in specific virus exposure among the test subjects. Nevertheless, researchers “observed strong similarities in antibody responses across individuals. In particular, we found multiple instances of single peptides that were recurrently recognized by antibodies in the vast majority of donors,” according to the article’s abstract.

The sensitivity range of this test was high—from 95% to 100%, according to Elledge. “We didn't falsely identify people who were negative. That gave us confidence that we could detect other viruses, and when we did see them we would know they were real,” he said in a statement issued by HHMI. The researchers found that VirScan was comparable to ELISA in terms of specificity, sensitivity and cost.