Can’t remember every viral infection you’ve ever had? Don’t worry, your blood can. A new test surveys the antibodies present in a person’s bloodstream to reveal a history of the viruses they’ve been infected with throughout their life. The method could be useful not only for diagnosing current and past illnesses, but for developing vaccines and studying links between viruses and chronic disease.
Now, researchers wondering whether a patient has a particular viral infection—from herpes and flu to the AIDS virus—test blood samples for one pathogen at a time. Many tests look for antibodies, proteins the immune system produces to recognize invaders, while others hunt for the virus’s own genetic material. Some assays can measure the presence or absence of longer-lasting antibodies that can linger for decades after an infection.
Researchers led by biologist Stephen Elledge of Brigham and Women’s Hospital in Boston and Harvard Medical School wanted to develop a test that could look at every current or past infection in one fell swoop. They first assembled a library of almost a hundred thousand synthetic protein fragments, each of them representing a section of a virus that an antibody might recognize. When the proteins are added to a drop of blood, antibodies attach to matching fragments; researchers can isolate the antibodies and, from the fragments they paired up with, determine which viruses someone has been infected with and what antibodies their body generated in response.
The new test, dubbed VirScan, “allows scientists to ask questions that just couldn’t be asked before,” Elledge says. “You can compare groups of people—young and old or those with a disease and those without—and see whether there’s a difference in their viral histories.” For instance, VirScan could help determine whether viral infections can trigger diabetes or chronic fatigue syndrome.
Elledge admits that, for now, VirScan might miss some viruses, because they’re too small or contain certain modifications that the fragment library can’t include. “We know that we’re probably missing a little bit,” he says. “But we’re still detecting a lot.”
“The work stands out by its breadth and technological innovation,” Ploegh says. “But if you ask an immunologist how many viruses or pathogens you’ve fought in your lifetime and what signatures of those infections remain, the results of this paper wouldn’t be a surprise.” The technology’s real value lies in the new questions scientists can answer, he says. “For sketching the natural history of the human species interacting with viruses, I think this is a very important tool.”
VirScan has yet to be scaled up for commercial use but Elledge hopes it won’t cost much more than existing tests that only look at one pathogen at a time. If so, it could even be used for routine screening at annual physicals, he says. “You could give a drop of blood every few years and they can run it to see if you have any new infections,” he says. This could help diagnose viruses like hepatitis C, which people often don’t know they have.