Along with soulful eyes and warm fuzzy coats, llamas have a far less appreciated feature: They make an array of immune system antibodies so tiny they can fit into crevices on the surface of an invading virus.

That could one day protect humans from entire families of flu viruses that bedevil scientists with their unpredictable ways. All, potentially, with a once-a-year puff up the nose.

In a study in the journal Science, a team from the Scripps Research Institute in La Jolla and international colleagues have taken a major step toward the long-sought goal of developing a universal influenza vaccine.

When they tested their formulation in mice, it quickly conferred complete protection against a raft of human flu strains adapted to mice. Those include A viruses, such as the H1N1 “swine flu” and B viruses, which occur only in humans. Against H1N1, a dose of the vaccine was shown to protect for at least 35 days.

The team borrowed techniques from immunology, microbiology, nanotechnology and genetic engineering. They vaccinated llamas against a number of strains of influenza. Then they took blood samples to collect any antibodies.

Among them were four uniquely small antibodies that showed an ability to destroy many different strains of influenza. From those little powerhouses, the researchers engineered a single protein capable of squeezing into spaces on a virus’ surface that are too small for most proteins. The resulting “multidomain antibody MD3606” could confer protection against pretty much any strain of flu that nature could throw in humankind’s way, the study authors said.

Getting any such vaccine to the public, however, “will take years,” said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases. “But if fully successful — a majestic leap right now — it could essentially eliminate the need from season to season” to divine which of possible flu viruses will rear up.