Scientists have discovered that one of Earth's oldest animals uses a radically different immune strategy to fight viruses, upending the long-held assumption that all animals inherited the same core antiviral toolkit from a common ancestor.
The discovery emerged from research on sea anemones, ancient marine creatures that branched away from the evolutionary line leading to humans over 600 million years ago. A team led by PhD candidate Ton Sharoni and Prof. Yehu Moran at the Hebrew University of Jerusalem, working with collaborators at the University of North Carolina at Charlotte, identified a protein called CARDIB that resembles a crucial human antiviral protein called MAVS, yet works in the opposite way.
The human MAVS protein activates the immune system when a virus is detected. CARDIB, by contrast, suppresses antiviral defenses under normal conditions. Yet when researchers used CRISPR to remove the CARDIB gene from sea anemones and exposed them to viruses, the animals became far more vulnerable to infection.
"Everything about CARDIB suggested it should function like MAVS," Moran said. "Instead, we discovered that it does the exact opposite. Rather than activating antiviral defenses, CARDIB normally suppresses them."
The counterintuitive result revealed that the immune brake CARDIB applies is essential for mounting an effective antiviral response. Without it, viruses multiplied rapidly and the animals' defenses collapsed.
To confirm the finding extended beyond laboratory conditions, researchers moved genetically modified sea anemones into outdoor marine tanks in South Carolina supplied with natural estuarine water. Within days, the anemones lacking CARDIB accumulated substantially more viruses than unmodified animals. Immune genes that appeared only moderately important in controlled experiments became clearly critical in nature.
The implications stretch far beyond sea anemones. The work suggests evolution has not settled on a single universal antiviral strategy. Instead, different animal groups independently developed distinct molecular systems for detecting and resisting viral infections.
"Humans and sea anemones both need protection from viruses, but this work shows that evolution can organize those defenses in fundamentally different ways," Moran said.
The research highlights why studying ancient organisms matters. Sea anemones and their relatives, corals and jellyfish, preserve evolutionary innovations that remain invisible when scientists focus only on humans, mice, and other commonly studied species. The findings were published in Nature Ecology & Evolution.
Author Jessica Williams: "This discovery should shift how scientists think about viral immunity across the animal kingdom, proving that nature found multiple winning solutions to the same problem."
Comments