Novel CARDIB Protein in Starlet Sea Anemone Reveals an Ancient Antiviral Strategy

Researchers at the Hebrew University of Jerusalem and the University of North Carolina at Charlotte have characterized a previously unknown protein, CARDIB (CARD Inhibitor Binding protein), in the starlet sea anemone (*Nematostella vectensis*). The protein, unlike the well-studied mitochondrial antiviral-signaling protein (MAVS), suppresses antiviral defenses under baseline conditions but is required for an effective response to viral infection.

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• N. vectensis* has an immune system dating back at least 648 million years to the Cryogenian “snowball Earth” period. Prior assumptions held that antiviral mechanisms were largely conserved across animal lineages; the discovery of CARDIB challenges this view by demonstrating an independent evolutionary solution.

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• Ton Sharoni – lead author, Hebrew University of Jerusalem.

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• Yehu Moran – experimental biologist, co-lead author, Hebrew University of Jerusalem.

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• University of North Carolina at Charlotte – partner laboratory providing field-testing facilities.

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• June 2024 – Study published in *Nature Ecology & Evolution*.

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• Early 2024 – CRISPR-mediated knockout of the CARDIB gene created in laboratory anemones.

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• Mid-2024 – Field experiment conducted in estuary water from Georgetown, South Carolina; observations recorded over 96 hours.

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• CARDIB-deficient anemones displayed markedly higher viral susceptibility compared with wild-type counterparts.

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• In native estuary water, CARDIB-producing anemones survived and thrived within 96 hours, whereas knockout individuals showed rapid decline.

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• CARDIB-expressing animals exhibited reduced apoptosis, indicating a “slower but sustained antiviral response.”

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The work suggests that distinct antiviral pathways can evolve independently, expanding the repertoire of immune strategies available for study. Understanding CARDIB’s mechanism may inform novel antiviral therapeutics and highlight the value of non-model organisms in biomedical research.

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The investigators emphasized that CARDIB functions as a regulatory brake, essential for mounting a balanced antiviral response. They noted that the protein’s activity is not an artifact of laboratory conditions but a critical component of the anemone’s natural defense in its estuarine habitat.

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Scientists placed both CARDIB-competent and CARDIB-deficient anemones in water samples collected from the Georgetown, South Carolina estuary. Within four days, the survival advantage of CARDIB-producing individuals became evident, confirming the protein’s ecological relevance.

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While the study demonstrates CARDIB’s functional importance, the precise molecular interactions by which it modulates antiviral signaling remain undefined. No alternative interpretations were presented in the source material.

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• “Humans and sea anemones both need protection from viruses, but this work shows that evolution can organize those defenses in fundamentally different ways,” — Yehu Moran, experimental biologist, co-lead author

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• “Everything about CARDIB suggested it should function like MAVS,” — Yehu Moran

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• “Rather than activating antiviral defenses,” — Yehu Moran

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• “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.” — Ton Sharoni, lead author

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• “It plays a crucial role in helping these animals cope with the viral challenges they face in nature.” — Yehu Moran

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The team plans to investigate CARDIB’s molecular partners and assess whether analogous proteins exist in other taxa. Such work could uncover additional ancient immune mechanisms with potential translational applications for human viral diseases.

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