Stephen Elledge remembers the feeling of finally seeing the full picture. For years, virologists had been studying viruses one by one, like detectives examining clues from a single crime scene. But Elledge, a professor at Harvard Medical School, wanted something bigger: a way to study nearly every virus that threatens humans, all at once.
Now, his team has built exactly that. They created the largest library of viral proteins ever made — a collection of 13,000 DNA sequences that code for about 9,000 proteins from 513 different viruses, ranging from the Andes hantavirus to Ebola to Zika. The work was described in the journal Cell on July 2, 2026.
"This library reveals how viruses manipulate human cells on a scale that simply wasn't possible before," Elledge said.
Understanding viral proteins matters because these tiny molecules are what allow viruses to spread and cause disease. When a virus enters your body, its proteins work like tools — some disarm your immune system, some hijack your cells' machinery to make copies of the virus. By studying these proteins, scientists can find weak spots to target with vaccines or treatments.
The challenge is that nearly 300 viruses are known to infect humans, but most have barely been studied. Scientists tend to focus on a handful that cause serious illness, like influenza or HIV, while dozens of others remain mysteries. Previous protein libraries, built by other research groups, contained only 100 or 200 sequences each and focused on single viruses or small families.
"Most viruses have never been studied in detail, yet evolution has already performed countless experiments for us," Elledge said. "This library gives us a way to read the results of those experiments across the viral world."
The new library is called a viral ORFeome — named after the DNA sequences that carry protein instructions. Researchers can take any combination of the 13,000 DNA constructs and insert them into cells in the lab. Each cell then makes one specific viral protein, allowing scientists to observe exactly what that protein does and how it interacts with human cells.
The team has already used the library to identify hundreds of viral proteins that interfere with immune responses. In a second paper published in Science on July 9, they showed how some viruses hijack cells' natural garbage-disposal systems to hide from immune attack.
The library was designed with safety in mind. The DNA sequences cannot reassemble into working viruses or infect cells — they only carry instructions for making individual proteins. This means researchers who didn't specialize in virology can now join the effort to study viral threats.
"This is a biosafe way to study viral proteins individually instead of studying a whole virus," said Caleb Glassman, a research fellow at Brigham and Women's Hospital and co-author of the study.
Elledge sees the library as a new foundation for understanding emerging diseases. As new viruses jump from animals to humans — something scientists expect to continue — researchers will be able to study their proteins faster than ever before, potentially giving humanity a head start in developing defenses.