New Study Reframes Hepatitis B Viral Mechanics, Could Unlock First True Mouse Model for Drug Testing

Data from a new study published in PNAS, led by Charles M. Rice, PhD, head of the Laboratory of Virology and Infectious Disease at The Rockefeller University, reveal that it is only partially correct that mouse liver cells cannot support hepatitis B virus (HBV) infection; the true barrier lies not in the formation of the virus' genetic reservoir but in a previously unrecognized disruption of the viral entry process.^1,2

A Persistent Public Health Challenge

Chronic HBV infection remains one of the most consequential infectious diseases globally. An estimated 240 million individuals are living with chronic HBV infection, representing approximately 2.9% of the global population, and fewer than 5% of those eligible for treatment are receiving it. The disease is frequently asymptomatic for decades, only to emerge as advanced cirrhosis or hepatocellular carcinoma. In 2022 alone, chronic HBV was responsible for an estimated 1.1 million deaths, predominantly from cirrhosis and liver cancer.^3,4

Current standard-of-care therapies—including reverse transcriptase inhibitors and interferons—can suppress viral replication, but control of infection and clearance of the viral genome are rarely achieved, requiring lifelong daily dosing. Progress toward a functional cure has been substantially hampered by the lack of a practical small-animal model that supports the full HBV life cycle.²

The cccDNA Problem

HBV's persistence is driven by a stable form of viral genetic material, covalently closed circular DNA (cccDNA). Once established in the nucleus of a hepatocyte, cccDNA serves as a durable template for viral gene expression and replication and is notoriously difficult to eliminate. It is the primary reason chronic HBV remains largely incurable and a central target for next-generation antiviral strategies.^1,2

For approximately 30 years, the prevailing view was that mouse liver cells could not produce cccDNA, making mice an unsuitable host for studying the complete HBV life cycle. As a result, researchers have largely relied on humanized mice, engineered to carry human liver cells, which are expensive and difficult to scale for high-throughput drug testing.^1,2

Overturning the Assumption

The study used a novel method to create stable cell lines that bypassed the entry step entirely, demonstrating that mouse liver cells are fully capable of forming cccDNA at levels comparable to those observed in human cells. Further experiments incorporating the HBV receptor into mouse liver cells helped narrow the likely barrier to a late step during viral entry, occurring before nucleocapsid uncoating—the moment the virus releases its DNA payload toward the cell nucleus.^1,2

"This tells us that mouse liver cells can form the HBV's cccDNA, but to detect it, there has to be an abundance of them," Xupeng Hong, PhD, MS, first author on the study and a postdoc in the Rice lab, said in the news release. "My theory is that these have been in the cells all along but were unobserved due to low numbers."²

Implications for Drug Development

The study authors noted that the timing and location of nucleocapsid uncoating are important. If uncoating occurs prematurely, the viral genome becomes visible to the host's antiviral defenses, whereas if it occurs too late or in the wrong compartment, the virus cannot establish cccDNA and the infection stalls. Identifying what triggers this misfire in mouse cells could reveal exploitable therapeutic targets in humans.^1,2

“This new understanding of the mechanisms behind human HBV’s inability to infect mice provides a foundation for the development of fully HBV-susceptible mouse models,” Rice said in a news release. “Being able to model HBV’s infection processes, host response, and disease progression could enable the design of new therapies for what is now a largely incurable disease.”²

A Much-Needed Testing Ground

Developing a robust mouse model that supports both the formation and maintenance of cccDNA is essential for advancing HBV research and evaluating novel therapeutic approaches to cure chronic HBV infection. Such a model would enable scalable, reproducible preclinical testing that the field lacks.^4,5

"A next-generation model would not only allow us to finally study the infection and host-virus interaction in detail, but it would also provide a much-needed testing ground for new therapies," Rice added.²

With the Rice lab now focused on pinpointing the precise molecular factors responsible for the entry block, overcoming this barrier could accelerate the development of cccDNA-targeting antivirals and bring researchers closer to the ultimate goal of permanently eliminating cccDNA from infected individuals.^1,2

REFERENCES

1. Hong X, Brousseau G, Chen HA, et al. Hepatitis B virus covalently closed circular DNA formation in murine hepatic cells uncovers a late entry block. Proc Natl Acad Sci U S A. 2026;123(17) e2603476123. doi:10.1073/pnas.2603476123

2. New clues to hepatitis B species restriction could help build a novel model for studying infection and testing therapies. News release. The Rockefeller University. April 22, 2026. Accessed May 8, 2026. https://www.eurekalert.org/news-releases/1125332

3. World Health Organization. Global hepatitis report 2026. World Health Organization. 2026. https://www.who.int/teams/global-hiv-hepatitis-and-stis-programmes/hepatitis/reports/global-hepatitis-report-2026

4. Easterbrook PJ, Luhmann N, Bajis S, et al. WHO 2024 hepatitis B guidelines: an opportunity to transform care. Lancet Gastroenterol Hepatol. 2024;9(6):493-495. doi:10.1016/S2468-1253(24)00089-X

5. Broeckhoven E, Dallmeier K. Mouse models for chronic hepatitis B: old challenges, novel approaches. Cell Mol Gastroenterol Hepatol. 2025;19(1):101421. doi:10.1016/j.jcmgh.2024.101421