Scientists discover key to hepatitis A virus replication and show drug efficacy

In the absence of current treatments for hepatitis A, UNC School of Medicine scientists led by Stanley M. Lemon, MD, have discovered how a protein and enzymes interact to allow the hepatitis A virus to replicate, and they used a drug known to stop viral replication in an animal. model.

CHAPEL HILL, NC — The viral replication cycle is crucial for a virus to spread inside the body and cause disease. Focusing on this hepatitis A virus (HAV) cycle, UNC School of Medicine scientists found that replication requires specific interactions between the human protein ZCCHC14 and a group of enzymes called TENT4 poly( A) polymerases. They also found that the oral compound RG7834 stopped replication at a key step, preventing the virus from infecting liver cells.

These conclusions, published in the Proceedings of the National Academy of Sciencesare the first to demonstrate an effective drug treatment against HAV in an animal model of the disease.

“Our research demonstrates that targeting this protein complex with an orally administered small molecule therapeutic halts viral replication and reverses liver inflammation in a mouse model of hepatitis A, providing proof of principle for antiviral therapy and ways to stop the spread of hepatitis A in epidemic settings,” said lead author Stanley M. Lemon, MD, professor in the UNC Department of Medicine and the Department of Microbiology and Immunology from UNC, and Fellow of the UNC Institute for Global Health and Infectious Diseases.

Stan Lemon, MD

Lemon, who in the 1970s and 80s was part of a research team at Walter Reed Army Medical Center that developed the first inactivated HAV vaccine given to humans, said HAV research slowed after the vaccine became widely available in the mid-1990s. Cases plummeted in the 2000s as vaccination rates soared. The researchers turned their attention to hepatitis B and C viruses, both of which are very different from HAV and cause chronic disease. “It’s like comparing apples to turnips,” Lemon said. “The only similarity is that they all cause liver inflammation.” HAV is not even part of the same family of viruses as hepatitis B and C viruses.

Hepatitis A outbreaks have been on the rise since 2016, even though the HAV vaccine is highly effective. Not everyone is vaccinated, Lemon pointed out, and HAV can exist for long periods in the environment — like on our hands and in food and water — resulting in more than 44,000 cases, 27,000 hospitalizations. and 400 deaths in the United States since 2016, according to the CDC.

Several epidemics have occurred in recent years, including in San Diego in 2017, primarily due to homelessness and illicit drug use, causing serious illness in approximately 600 people and killing 20. In 2022, it There was a small outbreak linked to organic strawberries in several United States, resulting in a dozen hospitalizations. Another outbreak in 2019 was linked to fresh blackberries. Globally, tens of millions of HAV infections occur each year. Symptoms include fever, abdominal pain, jaundice, nausea, and loss of appetite and sense of taste. Once sick, there is no treatment.

In 2013, Lemon and his colleagues discovered that the hepatitis A virus changes dramatically inside the human liver. The virus hijacks pieces of cell membrane as it leaves liver cells, hiding antibodies that would otherwise quarantine the virus before it spreads widely through the bloodstream. This work has been published in Nature and provided insight into what researchers have yet to learn about this virus which was discovered 50 years ago and likely caused disease dating back to ancient times.

A few years ago, researchers discovered that the hepatitis B virus requires TENT4A/B for its replication. Meanwhile, Lemon’s lab conducted experiments to search for human proteins that HAV needs to replicate, and they found ZCCHC14 – a particular protein that interacts with zinc and binds RNA.

“That was the tipping point of this ongoing study,” Lemon said. “We discovered that ZCCHC14 binds very specifically to a certain part of HAV RNA, the molecule that contains the genetic information of the virus. And thanks to this binding, the virus is able to recruit TENT4 from the human cell. »

In normal human biology, TENT4 is part of a process of RNA modification during cell growth. Essentially, the HAV hijacks TENT4 and uses it to replicate its own genome.

This work suggests that stopping the recruitment of TENT4 could stop viral replication and limit the disease. Lemon’s lab then tested the compound RG7834, which had previously been shown to actively block the hepatitis B virus by targeting TENT4. In the PNAS article, the researchers detailed the precise effects of oral RG7834 on HAV in the liver and feces and how the ability of the virus to cause liver damage is significantly reduced in mice that had been genetically engineered to develop an infection and a HAV disease. The research suggests that the compound was safe at the dose used in this research and during the acute period of the study.

“This compound is a far cry from being used by humans,” Lemon said, “But it opens the door to an effective way to treat a disease that we have no cure for.”

Pharmaceutical company Hoffmann-La Roche developed RG7834 for use against chronic hepatitis B infections and tested it in humans in a phase 1 trial, but animal studies have suggested that it may be too toxic for use over long periods of time.

“Treatment for hepatitis A would be short-term,” Lemon said, “and, more importantly, our group and others are working on compounds that would hit the same target without toxic effects.”

This research was a collaboration between the Lemon lab and the lab of Jason Whitmire, professor of genetics at UNC School of Medicine. Lemon and Whitmire are members of the UNC Lineberger Comprehensive Cancer Center.

The first authors of the PNAS article are You Li and Ichiro Misumi. Other authors, all at UNC, are Tomoyuki Shiota, Lu Sun, Erik Lenarcic, Hyejeong Kim, Takayoshi Shirasaki, Adriana Hertel-Wulff, Taylor Tibbs, Joseph Mitchell, Kevin McKnight, Craig Cameron, Nathaniel Moorman, David McGivern, John Cullen, Jason K. Whitmire and Stanley M. Lemon.

This work was supported by grants from the National Institute of Allergy and Infectious Diseases (R01-AI131685), (R01-AI103083), (R01-AI150095), (R21-AI163606), (R01-AI143894), ( R01-AI138337). The UNC Core Pathology Services and UNC High-Throughput Sequencing Facility were supported in part by a National Cancer Institute Center Core Support Grant (P30CA016086) to the UNC Lineberger Comprehensive Cancer Center.

Media contact: Marc Derewicz919-923-0959

Sara H. Byrd