A virus must go through the viral replication cycle in order to propagate throughout the body and cause illness. The UNC School of Medicine researchers studied that cycle in the hepatitis A virus (HAV) and found that replication necessitates particular interactions between the human protein ZCCHC14 and a family of enzymes termed TENT4 poly(A) polymerases.
Additionally, they discovered that the oral drug RG7834 halted viral replication at a critical stage, preventing liver cell infection.
These findings are the first to show that pharmacological treatment for HAV is effective in an animal model of the illness and were published in the Proceedings of the National Academy of Sciences.
“Our research demonstrates that targeting this protein complex with an orally delivered, 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 the means to stop the spread of hepatitis A in outbreak settings,” said senior author Stanley M. Lemon, MD, professor in the UNC Department of Medicine and UNC Department of Microbiology & Immunology, and member of the UNC Institute for Global Health and Infectious Diseases.
The first inactivated HAV vaccine to be given to humans was produced by a research team at the Walter Reed Army Medical Center in the 1970s and 1980s, according to Lemon. After the vaccine became widely available in the mid-1990s, research on HAV slowed down.
As vaccination rates soared in the 2000s, the number of cases fell. The hepatitis B and C viruses, which differ greatly from HAV and also cause chronic disease, caught the interest of researchers.
“It’s like comparing apples to turnips,” Lemon said. “The only similarity is that they all cause inflammation of the liver.”
Our research demonstrates that targeting this protein complex with an orally delivered, 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 the means to stop the spread of hepatitis A in outbreak settings.
Stanley M. Lemon
Hepatitis B and C viruses are not even members of the same viral family as HAV. Despite the high efficacy of the HAV vaccination, hepatitis A outbreaks have increased since 2016.
Lemon emphasized that not everyone receives vaccinations and that HAV can linger for a very long time in the environment, including on our hands, in food, and in water, causing more than 44,000 infections, 27,000 hospitalizations, and 400 fatalities in the US since 2016, according to the CDC.
Over the past few years, there have been a number of outbreaks, including one that killed 20 people and sickened 600 people in San Diego in 2017. This outbreak was mostly caused by homelessness and drug use.
A minor outbreak associated with organic strawberries occurred in several states in 2022 and resulted in roughly a dozen hospitalizations. In 2019, fresh blackberries were related to yet another outbreak.
Tens of millions of HAV infections take place annually throughout the world. Fever, stomach ache, jaundice, nausea, as well as loss of taste and appetite, are some of the symptoms. There is no cure once you are sick.
Lemon and colleagues discovered in 2013 that the hepatitis A virus undergoes significant modifications within the human liver. As it exits liver cells, the virus snares pieces of the cell membrane to disguise itself from antibodies that may have otherwise contained it before it spread far in the bloodstream.
This research, which was published in Nature, revealed how much is still unknown about the virus that was first identified 50 years ago and is thought to have been the source of disease as far back as ancient times.
A few years ago, scientists discovered that the hepatitis B virus needed TENT4A/B to replicate. While this was going on, investigations conducted in Lemon’s lab sought out human proteins that HAV need to replicate, and they discovered ZCCHC14, a specific protein that interacts with zinc and attaches to RNA.
“This was the tipping point for this current study,” Lemon said. “We found ZCCHC14 binds very specifically to a certain part of HAV’s RNA, the molecule that contains the virus’s genetic information. And as a result of that binding, the virus is able to recruit TENT4 from the human cell.”
TENT4 participates in an RNA modification pathway during cell proliferation in typical human biology. TENT4 is essentially taken over by HAV, which then uses it to reproduce its own genome.
According to this research, preventing TENT4 recruitment could halt viral replication and reduce illness. The substance RG7834, which had previously been demonstrated to actively stop the Hepatitis B virus by targeting TENT4, was then put to the test in Lemon’s lab.
In the PNAS article, the researchers provided specific information on how oral RG7834 affects HAV in the liver and feces as well as how the virus’s capacity to produce liver damage is significantly reduced in mice that have been genetically modified to acquire HAV infection and disease.
According to the research, the substance was safe at the dosage and study duration employed in this acute case.
“This compound is a long way from human use,” Lemon said, “But it points the path to an effective way to treat a disease for which we have no treatment at all.”
In a phase 1 trial, Hoffmann-La Roche, a pharmaceutical company, tested RG7834 on people to see if it may treat chronic hepatitis B infections. However, animal tests indicated that it might be too hazardous for long-term usage.
“The 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.”
The Lemon lab worked together on this project with Jason Whitmire’s group, a genetics professor at the UNC School of Medicine. Members of the UNC Lineberger Comprehensive Cancer Center are Lemon and Whitmire.
The first authors of the PNAS paper 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 Pathology Services Core 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.
