Unique Antiviral Defense System Found in Sea Anemones
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Student summary by Elizabeth Li
Original Source: Sharoni, T. et al., Nature Ecology and Evolution, June 26, 2026
Abstract
Background: Viruses have infected living organisms for hundreds of millions of years, driving the evolution of unique defense systems in different species. Scientists believe that by studying the different types of immune systems in organisms, we can better understand the effects of viruses on our bodies and how to counteract them most effectively.
Objective: Ton Sharoni and Professor Yehu Moran at the Hebrew University of Jerusalem, along with a team of researchers at the University of North Carolina, wanted to examine other species and compare their immune systems to human biological defenses. The researchers wanted to determine the origin of antiviral immunity and its function in early evolution to better understand how the immune system works and evolved.
Method: Scientists identified and studied a protein named CARDIB (CARD Inhibitor Binding protein) from sea anemones, animals that split from our evolutionary pathway more than 600 million years ago and whose protein was structurally very similar to the human protein MAVS (Mitochondrial Antiviral-Signaling protein). They compared CARDIB to MAVS, which is an antiviral defense system in human bodies that activates immune responses when viruses enter the body. To find out how CARDIB worked, they used CRISPR gene-editing to compare how the anemones' immune systems reacted to viruses with and without the gene. They exposed the modified anemones to viruses and tested them in outdoor marine environments to see whether the system worked in real-world situations.
Results: At first, CARDIB appeared very similar to MAVS, suggesting that it was part of the same ancient system that eventually evolved into MAVS. However, under further examination, CARDIB was found to suppress the same antiviral systems that MAVS activates. Surprisingly, animals without the CARDIB gene became more vulnerable and could not mount an effective defense. The research showed that CARDIB had a positive impact on anemones' immune systems despite suppressing antiviral pathways.
Conclusion: These findings challenge the idea that all antiviral systems evolved through the same pathway. Instead, they suggest that different evolutionary families developed unique ways of fighting viruses. Studying ancient animals such as anemones could influence future biomedical research and lead to new scientific discoveries about immunity.
