Sea anemones use a protein called CARDIB to regulate their immune systems, a discovery that challenges the long-standing idea that animals inherited a single core antiviral system from a common ancestor. Research published in Nature Ecology & Evolution by the Hebrew University of Jerusalem and the University of North Carolina at Charlotte reveals that this protein acts as a “brake” on immune responses, a function that is essential for survival against viral infections in the wild.
How does the CARDIB protein function?
While CARDIB resembles the MAVS protein found in humans, it performs the opposite function. In humans, MAVS helps trigger the immune system so it can respond to the infection. Conversely, CARDIB suppresses immune activity. According to Prof. Yehu Moran, head of the Department of Ecology, Evolution and Behavior at the Hebrew University, researchers initially expected the protein to behave like its human counterpart due to its structural similarity. Instead, experiments proved that suppressing the immune response is a critical mechanism for the anemone’s antiviral defense.
Sea anemones diverged from the evolutionary line leading to humans more than 600 million years ago, making them vital subjects for studying the early evolution of animal immunity.
What happened when the CARDIB gene was removed?
To test the necessity of this suppression, researchers led by PhD candidate Ton Sharoni used CRISPR gene editing to remove the CARDIB gene in sea anemones. Upon exposure to viruses, the modified animals showed a marked increase in susceptibility to infection. Viruses multiplied more rapidly in these anemones, and the animals failed to properly activate their antiviral defenses. Sharoni noted that the results were counterintuitive, as removing the “brake” on the immune system actually hindered the animal’s ability to fight off disease.
Does this immune system work in nature?
The antiviral pathway functions effectively outside of laboratory settings. To verify their findings, researchers moved genetically modified sea anemones into outdoor marine mesocosms. These systems utilized natural estuarine water in South Carolina, exposing the anemones to a diverse range of environmental viruses and microorganisms. Moran stated that this confirmed the pathway is not simply a laboratory phenomenon, but plays a crucial role in helping these animals cope with the viral challenges they face in nature.
Evolutionary Strategies for Viral Resistance
The study suggests that evolution has produced multiple, distinct strategies for resisting viral infections across the animal kingdom. Rather than relying on a single ancestral immune system, different animal groups appear to have developed independent molecular solutions. This finding highlights the importance of studying non-traditional model organisms, as ancient species like sea anemones may harbor evolutionary innovations that would remain hidden if scientists focused only on humans, mice, and other commonly studied species.
When researching evolutionary biology, look beyond common lab models. Ancient marine invertebrates often provide the best clues for understanding the fundamental mechanisms that shaped modern animal immunity.
Frequently Asked Questions
- Why is the CARDIB protein considered “counterintuitive”?
It is counterintuitive because it acts as a suppressor of the immune system. Although CARDIB acts as a brake on the immune system under normal conditions, that brake turns out to be essential for mounting an effective antiviral response. - What does this mean for human immune research?
It suggests that the evolution of immune systems is more diverse than previously thought, indicating that scientists should explore a wider range of species to understand the full breadth of antiviral strategies. - How did researchers confirm the protein’s role?
They used CRISPR gene editing to remove the CARDIB gene and observed that the sea anemones became significantly more vulnerable to viral infections in both lab and natural environments.
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