A protein in sea anemones fights viruses by doing the opposite of what the human immune system does, and it works. Researchers at the Hebrew University of Jerusalem discovered that a protein called CARDIB in the sea anemone Nematostella vectensis normally suppresses antiviral defenses, yet the animal still survives infection. The finding upends a long held assumption that all animals inherited a single core antiviral system from a common ancestor.
A protein that looks familiar but works backwards
CARDIB closely resembles MAVS, a protein that in humans triggers the immune system when a virus is detected. The researchers expected CARDIB to do the same. Instead, they found it suppresses antiviral defenses. To understand why an animal would deliberately slow its own immune response, the team used CRISPR gene editing to remove the CARDIB gene from sea anemones. Without CARDIB, the anemones became much more vulnerable to viruses. Viruses multiplied faster, the animals failed to activate their antiviral defenses properly, and their ability to fight infection dropped sharply.
An ancient animal rewrites immune history
The sea anemone is an ancient marine animal that split from the evolutionary line leading to humans more than 600 million years ago. It is a close relative of corals and jellyfish. The research, led by PhD candidate Ton Sharoni and Prof. Yehu Moran at the Hebrew University of Jerusalem in collaboration with scientists from the University of North Carolina at Charlotte, was published in Nature Ecology & Evolution. It challenges the idea that animals inherited a single antiviral system from a common ancestor and instead points to multiple evolutionary solutions for resisting viral infections.
Why local researchers and the scientific community care
For scientists studying the evolution of immunity, the discovery suggests that nature experimented with different antiviral strategies. The sea anemone's approach, suppressing immunity rather than activating it, works well enough to protect the animal. The finding opens new questions about how other ancient animals defend themselves and whether similar immune suppression strategies exist elsewhere in the animal kingdom. The research was conducted in Israel, where the Hebrew University team continues to study the molecular details of CARDIB's function.
This discovery does not change what is known about human immunity, but it broadens the understanding of how evolution solved the problem of viral infection. The sea anemone offers a glimpse into an alternative antiviral strategy that has persisted for hundreds of millions of years.
