Common drugs may help dangerous viruses spread through the body

Medications are designed to treat diseases and relieve symptoms, but some can also produce unintended effects that put patients at risk. While side effects are common with many treatments, researchers have identified a particularly concerning possibility involving drugs used to control inflammation.

Scientists at the Norwegian University of Science and Technology (NTNU) have discovered that a widely used class of anti-inflammatory medications may make it easier for certain viruses to infect cells and spread throughout the body.

"We have found a surprising and potentially serious side effect of a class of anti-inflammatory drugs. They can help viruses spread more easily in the body," says Denis Kainov, a professor at the Department of Clinical and Molecular Medicine at the Norwegian University of Science and Technology (NTNU).

The medications at the center of the findings belong to a class called Janus kinase inhibitors, or JAKs. These drugs are widely prescribed to control inflammation, but their effects on the immune system may also leave the body more vulnerable to viral infections.

"Among the viruses that more easily affect the body with the help of these drugs are Rift Valley fever virus, influenza A, adenovirus and SARS-CoV-2, the virus that causes COVID-19," Kainov says.

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In a new study published in NAR Molecular Medicine, Kainov and his colleagues investigated how JAK inhibitors influence the body's ability to defend itself against viruses.

"JAK inhibitors are often prescribed for autoimmune diseases and inflammatory conditions such as rheumatoid arthritis," says Erlend Ravlo, a PhD research fellow at NTNU and first author of the article.

Although these medications can be highly effective at reducing inflammation, their benefits come with an important trade-off. By suppressing certain immune responses, they can also interfere with the mechanisms that normally protect the body from viral infections.

This pathway plays a central role in coordinating the body's response when viruses attempt to infect healthy tissue.

The research team found that JAK inhibitors, including the medication baricitinib, can reduce the activity of genes involved in fighting viral infections.

"These genes play a crucial role in the body's response to viral infections," said Aleksandr Ianevski, an NTNU researcher and coauthor of the new paper.

When JAK inhibitors interfere with this immune signaling system, they weaken an important layer of antiviral protection. Without the usual defensive response, viruses may find it easier to establish an infection and spread between cells.

To investigate these effects, the scientists combined advanced virology methods with gene expression analysis and organoid technology. Their experiments included cells from the lungs, eyes and brain, along with miniature organ models grown in the laboratory.

"Although JAK inhibitors are effective in the treatment of inflammation, this shows that they can pose a hidden risk for patients who have latent or active viral infections," says Ravlo.

The results highlight the importance of carefully considering the risks associated with JAK inhibitors, particularly when patients may already have a viral infection or when outbreaks are occurring.

However, the same immune-suppressing properties that create potential risks for patients could also offer advantages in certain research settings. Under controlled laboratory conditions, these effects may help scientists develop vaccines or evaluate potential antiviral medications.

The researchers hope their findings will encourage greater awareness of how JAK inhibitors influence the immune system and support further investigations into their safest and most effective uses.

Professor Magnar Bjørås of the Department of Clinical and Molecular Medicine provided significant scientific expertise and secured most of the funding for the research. Additional financial support came from the Central Norway Regional Health Authority, the South-Eastern Norway Regional Health Authority, the Research Council of Norway and the Swedish Research Council.