Nav: Home

How hepatitis B and delta viruses establish infection of liver cells

June 18, 2019

Princeton University researchers have developed a new, scalable cell culture system that allows for detailed investigation of how host cells respond to infection with hepatitis B (HBV) and delta virus (HDV). The paper describing their findings was published online on June 18, 2019 in the journal Hepatology.

HBV causes an acute illness that is usually rapidly cleared by adults with intact immune systems, but young children and people with HIV are at particular risk of chronic HBV infection, which can lead to cirrhosis or cancer of the liver. Infection with HBV also renders a person vulnerable to infection with HDV, which can cause acute liver failure and/or accelerate the progression to cirrhosis or cancer. Fortunately, an effective vaccine exists for HBV, and because HDV requires HBV in order to reproduce, both can be considered preventable diseases. However, the expense and limited availability of the vaccine leaves millions at risk for infection worldwide.

A better understanding of how the viruses affect the cells they infect would assist in the development of drugs to combat or even cure infection, but HBV and HDV only infect liver cells (hepatocytes) from humans and chimpanzees. Such cells are difficult to obtain, and when grown outside the body in cell culture, they undergo a process called de-differentiation: over the course of just a few days, they lose their specialized characteristics and functionality. When this happens, they also lose the ability to be infected with HBV and HDV, creating a significant obstacle to studying chronic viral infection.

"Attempts have been made since the mid-1980s to establish robust - and, importantly, persistent - infection in primary human hepatocytes (PHHs) with limited success," said Alexander Ploss, an associate professor in the Department of Molecular Biology at Princeton and leader of the study.

Studies with other tissues have shown that specialized cell types sometimes require the support of other types of cells in order to maintain their differentiated status. Hepatocytes make up the majority of cells in the liver, but the tissue also contains many other cell types, which are collectively referred to as "non-parenchymal cells." Recently, graduate student Benjamin Winer, together with colleagues in Ploss' lab and at the Hurel Corporation, demonstrated that freshly isolated human hepatocytes can be grown together with non-parenchymal cells on a supporting surface made of collagen. In this cell culture system, which the researchers call a self-assembling co-culture of primary human hepatocytes (SACC-PHH), the hepatocytes retain their differentiated state and can support chronic HBV infection for up to 40 days.

"This system has created unprecedented opportunities to study host responses to hepatitis virus, especially in the context of persistent infection," Ploss said.

In the new study, Winer and colleagues investigated how hepatocytes respond to infection with HBV and HDV. First, they tested whether SACC-PHH can support infection with both viruses. HBV hijacks the cell's protein-making machinery to make viral proteins, and HDV co-opts HBV proteins to assemble itself. Therefore, HDV can only reproduce when it infects cells at the same time as HBV (co-infection) or in cells already chronically infected with HBV (super-infection). The researchers found that both of these scenarios can occur in SACC-PHH, even when the culture system has been scaled down to tiny 384 microwell culture plates -- a development that makes the system well suited for high-throughput screening of candidate drugs. Accordingly, the team showed that prophylactic treatment with two candidate antivirals, entecavir and Myrcludex B, could reduce levels of both hepatitis viruses in SACC-PHH.

Viral infection provokes many changes in the host cell, ranging from metabolic adaptations to the activation of innate immune defenses that can recognize and destroy a virus inside the cell. To explore what changes hepatocytes experience in response to HBV/HDV infection, the authors looked at which genes were being expressed using a technique called RNA-Seq analysis. The data showed that cells infected with HBV exhibit elevated expression of genes involved in oxidative phosphorylation and interaction with the extracellular environment. By contrast, cells additionally infected with HDV had similar gene expression patterns as uninfected cells.

Interestingly, even though the hepatocytes' innate immune signaling pathways were intact and could be stimulated by addition of chemicals such as poly(I:C), HBV infection did not activate these defenses. On the other hand, treatment with poly(I:C) helped suppress HBV growth, suggesting the virus flies under the radar of cells' defenses to establish persistent infection.

How innate immune defenses affect HBV/HDV co-infection appears more nuanced. Stimulation of innate immune pathways with poly(I:C) had little effect on HDV. HBV/HDV co-infection also failed to activate defense pathways in the hepatocytes of most human donors studied, but one donor showed innate immune activation upon co-infection, indicating a person's genetic makeup may influence their ability to combat the infection.

"We believe that our optimized, high-throughput SACC-PHH platform is a unique resource for investigating hepatotropic pathogens, and that our data will help advance understanding persistent infections by HBV and HDV," Ploss said.
The study was funded by the National Institutes of Health, the Burroughs Wellcome Fund, the National Institute of Diabetes and Digestive and Kidney Diseases, the National Institute of Allergy and Infectious Diseases, and the New Jersey Commission on Cancer Research.

The study, " Analysis of host responses to hepatitis B and delta viral infections in a microscalable hepatic coculture system," by Benjamin Y. Winer, Jenna M. Gaska, Gabriel Lipkowitz, Yaron Bram, Amit Parekh, Lance Parsons, Robert Leach, Rohit Jindal, Cheul H. Cho, Anil Shrirao, Eric Novik, Robert E. Schwartz and Alexander Ploss, was published online in the journal Hepatology on June 18, 2019.

Princeton University

Related Hepatitis Articles:

Nanotechnology delivers hepatitis B vaccine
X-ray imaging shows that nanostructured silica acts as a protective vehicle to deliver intact antigen to the intestine so that it can trigger an immune response.
Checkmate for hepatitis B viruses in the liver
Researchers at Helmholtz Zentrum München and the Technical University of Munich, working in collaboration with researchers at the University Medical Center Hamburg-Eppendorf and the University Hospital Heidelberg, have for the first time succeeded in conquering a chronic infection with the hepatitis B virus in a mouse model.
How common is Hepatitis C infection in each US state?
Hepatitis C virus infection is a major cause of illness and death in the United States and injection drug use is likely fueling many new cases.
New strains of hepatitis C found in Africa
The largest population study of hepatitis C in Africa has found three new strains of the virus circulating in the general population in sub-Saharan Africa.
High stability of the hepatitis B virus
At room temperature, hepatitis B viruses (HBV) remain contagious for several weeks and they are even able to withstand temperatures of four degrees centigrade over the span of nine months.
Findings could lead to treatment of hepatitis B
Researchers have gained new insights into the virus that causes hepatitis B -- a life-threatening and incurable infection that afflicts more than 250 million people worldwide.
How to cure more hepatitis C patients
The cost of cures for hepatitis C have been prohibitive, but experts who served on an NAS panel have a solution that will save more patients and incentivize drug innovation.
Hepatitis C: A novel point-of-care assay
One of the major challenges identified by the WHO in efforts to eradicate the hepatitis C virus is the diagnosis of chronic cases that are generally asymptomatic.
Countries risk 'running out' of hepatitis C patients to treat, says World Hepatitis Alliance
The latest data on the global hepatitis C epidemic, released today at the World Hepatitis Summit in Sao Paulo, Brazil, reveal that most countries (especially high-income countries) are running out of patients to treat because of the low diagnosis rates worldwide.
Australia currently on track to eliminate hepatitis C by 2030, but challenges remain for hepatitis B
New data released at this year's World Hepatitis Summit in Sao Paulo, Brazil, shows that Australia is currently on track to eliminate hepatitis C thanks to its huge efforts to enable population-wide access to treatment.
More Hepatitis News and Hepatitis Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

Why do we revere risk-takers, even when their actions terrify us? Why are some better at taking risks than others? This hour, TED speakers explore the alluring, dangerous, and calculated sides of risk. Guests include professional rock climber Alex Honnold, economist Mariana Mazzucato, psychology researcher Kashfia Rahman, structural engineer and bridge designer Ian Firth, and risk intelligence expert Dylan Evans.
Now Playing: Science for the People

#541 Wayfinding
These days when we want to know where we are or how to get where we want to go, most of us will pull out a smart phone with a built-in GPS and map app. Some of us old timers might still use an old school paper map from time to time. But we didn't always used to lean so heavily on maps and technology, and in some remote places of the world some people still navigate and wayfind their way without the aid of these tools... and in some cases do better without them. This week, host Rachelle Saunders...
Now Playing: Radiolab

Dolly Parton's America: Neon Moss
Today on Radiolab, we're bringing you the fourth episode of Jad's special series, Dolly Parton's America. In this episode, Jad goes back up the mountain to visit Dolly's actual Tennessee mountain home, where she tells stories about her first trips out of the holler. Back on the mountaintop, standing under the rain by the Little Pigeon River, the trip triggers memories of Jad's first visit to his father's childhood home, and opens the gateway to dizzying stories of music and migration. Support Radiolab today at