Deep in the long history of animal life, a humble sea anemone has revealed that the body's defenses against viruses need not be written in a single script. Researchers at the Hebrew University of Jerusalem and the University of North Carolina at Charlotte found that these ancient marine animals rely on a protein, CARDIB, which resembles the human antiviral messenger MAVS yet works in the opposite direction, restraining immune signals while still being indispensable to fighting infection. The finding, published in Nature Ecology & Evolution, suggests that evolution has arrived at protection aga
Sea Anemones Use a Different Antiviral Playbook Than Humans, Study Finds
That brake turns out to be essential for mounting an effective antiviral response.
Deep in the long history of animal life, a humble sea anemone has revealed that the body's defenses against viruses need not be written in a single script. Researchers at the Hebrew University of Jerusalem and the University of North Carolina at Charlotte found that these ancient marine animals rely on a protein, CARDIB, which resembles the human antiviral messenger MAVS yet works in the opposite direction, restraining immune signals while still being indispensable to fighting infection. The finding, published in Nature Ecology & Evolution, suggests that evolution has arrived at protection against viruses by more than one road, and that the immune systems we know best may be only one chapter of a wider story.
Researchers moved sea anemones from their laboratory aquaria into outdoor tanks in South Carolina, filled with natural estuarine water. There, the animals met the full range of viruses and microbes they would face in the wild, and the differences appeared within days. Anemones that had been genetically edited to lack a protein called CARDIB carried substantially more viruses than unmodified animals, and the same held for those missing related antiviral genes.
The study, led by PhD candidate Ton Sharoni and Prof. Yehu Moran at the Hebrew University of Jerusalem with colleagues at the University of North Carolina at Charlotte, began with a familiar piece of human biology. In humans, the protein MAVS helps trigger the immune response when a virus is detected. Sea anemones split from the line leading to humans more than 600 million years ago, so the team hoped they might reveal how old such systems are. In the anemones they found CARDIB, a protein that looked strikingly like MAVS and was expected to do the same job. Instead, it does the opposite: it normally suppresses antiviral defenses.
That paradox prompted experiments using CRISPR to remove the gene. Animals without CARDIB struggled, with viruses multiplying faster and their defenses failing to activate properly. The brake, it turned out, was essential to mounting an effective response.
The authors see the result as a challenge to the long-held idea that animals inherited one core antiviral system from a common ancestor. Different lineages may have built distinct molecular solutions to the same problem. As Moran put it, evolution can organize protection from viruses in fundamentally different ways. The work also argues for studying ancient organisms alongside the usual model species, since innovations like this could stay hidden otherwise. What comes next is finding out how far this alternative reaches across the animal kingdom.
The sea anemones in this study were moved out of their laboratory aquaria and into outdoor tanks in South Carolina, filled with natural estuarine water. It was a deliberate test. In that water, the animals met the full range of viruses and microorganisms they would face in the wild. Within days, the difference was obvious.
The anemones in question had been genetically edited to lack a protein called CARDIB. Compared with unmodified animals, they accumulated substantially more viruses. The same was true of anemones missing related antiviral genes. The result confirmed what the team had seen under controlled conditions, and it added a wrinkle: one immune gene that looked only moderately important in laboratory tests proved clearly important in natural conditions.
The work was led by PhD candidate Ton Sharoni and Prof. Yehu Moran at the Hebrew University of Jerusalem, in collaboration with scientists at the University of North Carolina at Charlotte. It was published in Nature Ecology & Evolution. Moran heads the university's Department of Ecology, Evolution and Behavior.
The starting point was a familiar piece of human biology. In humans and other vertebrates, a protein called MAVS is a key part of antiviral defense: when a virus is detected, MAVS helps trigger the immune system to respond. The researchers wanted to know how old that kind of system might be, so they turned to sea anemones. These marine animals split from the evolutionary line leading to humans more than 600 million years ago. They are also close relatives of corals and jellyfish, which makes them a useful window onto early animal immunity.
In the anemones, the team found a protein no one had described before and named it CARDIB, short for CARD Inhibitor Binding protein. It looked strikingly like MAVS, and the researchers expected it to do the same job. It did not. "Everything about CARDIB suggested it should function like MAVS," Moran said. "Instead, we discovered that it does the exact opposite." Rather than switching antiviral defenses on, CARDIB normally suppresses them.
That raised an obvious question: why would an animal hold back its own immune response? To find out, the team used CRISPR gene editing to remove the CARDIB gene from sea anemones, then exposed the animals to viruses. Those without CARDIB became much more susceptible. Viruses multiplied faster, the animals failed to properly activate their antiviral defenses, and their ability to fight infection dropped dramatically. Sharoni called the results completely counterintuitive. Under normal conditions CARDIB acts as a brake on the immune system, he said, yet that brake turns out to be essential for mounting an effective antiviral response.
Taken together, the experiments show that sea anemones depend on an antiviral pathway fundamentally different from the human one, even though the two systems contain molecular parts that look very much alike. The authors read this as a challenge to the long-standing idea that animals inherited a single core antiviral system from a common ancestor. Different animal groups may instead have developed distinct molecular systems for detecting viruses and stopping their spread. "Humans and sea anemones both need protection from viruses," Moran said, "but this work shows that evolution can organize those defenses in fundamentally different ways."
The study also makes a case for looking beyond the usual laboratory animals. Ancient organisms like sea anemones can preserve innovations that would stay hidden if researchers studied only humans, mice and other common model species. What to watch next is how far the finding extends, and whether other animal lineages turn out to have their own versions of the immune playbook.
Citações Notáveis
Humans and sea anemones both need protection from viruses, but this work shows that evolution can organize those defenses in fundamentally different ways.— Prof. Yehu Moran, Hebrew University of Jerusalem
The results were completely counterintuitive.— Ton Sharoni, PhD candidate, Hebrew University of Jerusalem
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