First mapping of NS4B interactions across eight orthoflaviviruses reveals new antiviral target

For the first time, researchers at Leibniz Institute of Virology have mapped the NS4B interactome across eight orthoflaviviruses. In doing so, they uncovered a conserved and previously unrecognized role for UBA5, the enzyme that initiates the UFMylation pathway, in viral replication—pointing to exciting new avenues for antiviral development.

Mosquitoes and ticks are carrying more than just a nuisance bite: they are the vectors for a growing family of viruses known as orthoflaviviruses. This group includes well-known pathogens such as Dengue virus, Zika virus, Japanese encephalitis virus, Yellow fever virus, West Nile virus and Usutu virus. In recent years, several of these viruses have re-emerged or appeared in regions where they were previously unseen, triggering outbreaks that can range from life-threatening fevers and internal bleeding to severe neurological damage.

While vaccines exist for a few members of this virus family, no antiviral treatments are currently approved, leaving clinicians reliant on supportive care. With global travel and climate change expanding the reach of mosquitoes and ticks, orthoflaviviruses are increasingly recognized as a global health threat.

Understanding exactly how these viruses hijack human cells is therefore critical for developing effective treatments. The new study takes an important step in that direction. Led by Dr. Pietro Scaturro, head of the Systems Arbovirology research group at the Leibniz Institute of Virology, the team used integrated proteomic approaches to systematically map how NS4B, a critical viral protein, interacts with human proteins. The work was a collaborative effort with leading researchers from Duke-NUS Medical School in Singapore the INRS in Quebec Canada.

While previous preclinical studies suggested that NS4B could be one of the most promising drug targets among orthoflaviviruses, surprisingly little was known about its actual function inside infected cells. To fill this gap, the researchers analyzed NS4B from eight representative orthoflaviviruses, generating a high-confidence interaction map—the “NS4Bome”—that reveals how the virus rewires human cellular machinery to support its replication. 

“This is the first time we’ve mapped host interactions of NS4B across multiple orthoflaviviruses,” said Scaturro. “It provides a blueprint for understanding how these viruses hijack human cells and highlights vulnerabilities that could be targeted for drug development.”

The analysis revealed both shared and virus-specific strategies used to manipulate host cells. A key discovery was that UBA5, which initiates UFMylation, plays a conserved role in viral replication. Multiple viral proteins, including NS4B, recruit components of the UFMylation pathway to viral replication sites. There, they support mitochondrial function, the cell’s powerhouse, potentially providing the energy needed for efficient virus production. 

“We discovered that orthoflaviviruses exploit the UFMylation pathway which may lead to energy production in host cells, which is essential for viral replication. Targeting this pathway could offer a new strategy for developing broad-spectrum antivirals.” said Dr. Rajasekharan first author of the study.

Importantly, the researchers demonstrated that blocking UFMylation with small-molecule inhibitors significantly reduced viral replication in cell culture and improved outcomes in animal models, including a zebrafish model of Zika virusinfection. These findings suggest the UFMylation pathway could be a viable target for broad-spectrum antiviral drugs against orthoflaviviruses.

By revealing both conserved and virus-specific strategies, this work offers a framework for developing therapies against this expanding family of emerging viruses.

Original Publication

Rajasekharan, S., Barragan Torres, V.A., Pinheiro Gomes, Y.C. et al. A genus-wide interaction atlas across NS4B orthologues identifies a conserved role for UFMylation in orthoflavivirus replication. Nat Commun (2026). https://doi.org/10.1038/s41467-026-70437-9