New mRNA and gene editing tools offer hope for dengue virus treatment

Dengue fever, a painful and sometimes deadly mosquito-borne infection well-known in tropical countries, is spreading rapidly across the planet. Today, 4 billion people live in high-risk areas, such as the southeastern United States, which do not yet have effective antiviral treatment.

A team of researchers led by biomedical engineer Phil Santangelo has developed a breakthrough therapy to target and kill the virus using the gene-editing tool CRISPR-Cas13. The team’s systemic delivery of the treatment successfully treated the dengue virus in mice, the researchers explain in a study published in Microbiology of nature.

Dengue is difficult to treat, in part because there are four different serotypes of the virus, which means four different targets for a vaccine. People infected with one serotype who then contract a second version of the virus can end up with severe illness. This second attack can end up amplifying the first. Symptoms include fever, nausea, rash, pain (including behind the eyes), and in some cases, internal bleeding, shock, and death.

“There are several challenges in treating dengue fever. So we asked ourselves, is it possible to produce an antiviral drug based on mRNA and CRISPR that could be eliminated with a single injection,” said Santangelo, a professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. “And that’s essentially what we’ve shown.”

New use of technology

With the global proliferation of the Aedes mosquito that spreads dengue and other viruses, the timing of such treatment would be fortuitous.

“Unfortunately, climate change is making these virus-carrying mosquitoes more prevalent,” Santangelo said. “So it’s a good idea to be prepared.”

This is the first time that an mRNA-based CRISPR treatment has worked against systemic viral infections in animal models. But Santangelo has demonstrated its effectiveness in previous studies focused on lung diseases, including a treatment for the coronavirus. That was an inhalable treatment using polymer nanoparticles, large, biodegradable molecules that are ideal for delivering drugs directly to the lungs.

To study the dengue virus, the team used lipid nanoparticles (LNPs), which look like tiny bubbles of fat that carry drugs through the bloodstream and into cells. The nanoparticles carried a custom-coded messenger RNA (mRNA) molecule.

The mRNA was encoded with Cas13a (a CRISPR protein that can cut viral RNA) and guide RNAs (to direct Cas13a to the viral RNA to be cut). The process essentially created a set of instructions. When the encoded mRNA was delivered to infected cells via the LNPs, the cell used these instructions to build Cas13a and guide RNAs, which degraded the viral RNA in those targeted cells.

Military precision

A single dose of the treatment was given to mice infected with lethal doses of two dengue virus serotypes, DENV-2 and DENV-3. All of the treated mice survived without unintended damage to their RNA. After treatment, the researchers also looked for traces of the virus in the mice’s brains, but found none.

“It appears that our treatment prevents the virus from entering the brain,” Santangelo said. “This may not be very critical for dengue fever, which is not found in the human brain. But this finding could be very important for Zika virus, Japanese encephalitis, West Nile virus and other viruses that affect the human brain.”

Santangelo’s team is now testing its approach on other dengue serotypes and will study the treatment on other viruses.

“We’re very interested in these types of approaches to eradicate as many viruses as possible with a single powerful treatment,” said Santangelo, whose team included researchers from Georgia State University as well as Emory’s Computational Core. “We’re trying to figure out the most effective way to kill these viruses. We’re not quite there yet, but we’ll get there eventually.”