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Disrupting host protein blocks enterovirus infections in mice

The enterovirus EV-D68, which has been linked to acute flaccid myelitis, was one of the enteroviruses used in the study. Cynthia S. Goldsmith and Yiting Zhang, CDC

Enteroviruses cause millions of infections each year in the United States. Most of the resulting diseases, like the common cold, are mild. But some enteroviruses can cause serious or even deadly conditions. Recently, an enterovirus was linked with cases of acute flaccid myelitis, a mysterious condition that causes paralysis.

There are over a hundred types of enteroviruses. That makes development of a vaccine or virus-specific treatments challenging. Researchers have been studying how the viruses interact with their hosts. Targeting proteins in the human body that the viruses depend on may be an effective way to treat enterovirus infections.

A team led by Dr. Jan Carette from Stanford University has been working to identify human proteins that are essential for viral infection. In their new study, they examined whether breaking the link between an enterovirus protein and an essential host protein could stop infection in human cells and in mice.

The research was funded in part by NIH’s National Institute of General Medical Sciences (NIGMS) and National Institute of Allergy and Infectious Diseases (NIAID). Results were published on September 16, 2019, in Nature Microbiology.

The researchers first did a genome-wide genetic screen. They used a gene-editing technology called CRISPR-Cas9 to disrupt single genes at a time in laboratory cells. They then infected the modified cells with one of two enteroviruses.

Three genes were critical for both viruses to replicate (make copies) inside the cells. Two of the genes were previously described. The third, SETD3, codes for a protein that helps regulate the cell’s internal structures.

The scientists found that other families of viruses didn’t need this protein to replicate. However, all of the enteroviruses tested did. Additional research showed that enteroviruses could get into cells that lacked SETD3 but weren’t able to reproduce and spread.

Further work showed that SETD3 interacts with a viral protein called 2A. This affinity between the two proteins was seen in all tested enteroviruses. When the researchers prevented 2A from binding to SETD3, the virus wasn’t able to replicate.

The scientists then investigated the effects of removing SETD3 from human cells and mice. Human lung cells engineered to lack SETD3 had a 100-fold reduction in viral replication after infection compared to normal lung cells. Mice engineered to lack SETD3, which were able to grow and develop, showed no symptoms of infection after injection of deadly enteroviruses.

Additional experiments showed that enteroviruses don’t rely on the activity of the SETD3 protein that’s required for its normal function in the human body.

“This gives us hope that we can develop a drug with broad antiviral activity against not only the common cold but maybe all enteroviruses, without even disturbing SETD3’s regular function in our cells,” Carette says.

Such an approach to drug development would aim to disrupt the interaction between SETD3 and 2A instead of shutting down SETD3 itself.

—by Sharon Reynolds