# Delineating the impact of human karyopherins on hepatitis B virus species tropism

> **NIH NIH F31** · PRINCETON UNIVERSITY · 2024 · $32,974

## Abstract

Project summary
Worldwide, over 257 million people are chronically infected with hepatitis B virus (HBV), which can lead liver
cirrhosis and/or hepatocellular carcinoma (HCC). The scarcity of small animal models has hampered curative
therapy development and a mechanistic understanding of viral pathogenesis since HBV has a narrow host
tropism limited to humans and chimpanzees, which is poorly understood. Our lab and others have previously
shown that expression of human sodium taurocholate co-transporting polypeptide (hNTCP), the HBV receptor,
facilitates viral uptake into murine cells and the intranuclear conversion of HBV relaxed-circular DNA (rcDNA)
into covalently closed circular DNA (cccDNA) is fully supported in mouse cells and yields infectious virions. These
data suggest that a late post-entry step, presumably capsid disassembly and/or nuclear import, constitutes a key
barrier in the murine HBV life-cycle. Prior work showed that heterokaryons formed from mouse and human
hepatoma cells expressing hNTCP are susceptible to HBV infection, suggesting that human-specific factors
critical for the HBV life cycle are missing in mouse hepatocytes rather than (dominant) restriction factor being
present in mouse cells. This prompted us to investigate the role of nuclear import proteins in restricting the murine
HBV life-cycle. My proposal is founded on strong preliminary data from our lab demonstrating that the expression
of several human karyopherin alphas and betas renders mouse Hepa1.6-hNTCP cells susceptible to HBV
infection. Excitingly, our data further show that human, but not mouse, KPNA2 expression increases the
susceptibility to HBV, establishing firmly that the observed increases are not simply due to the higher abundance
of KPNA2 but to the expression of the human orthologues. I now hypothesize that incompatibilities between one
or more karyopherins and the virus preclude efficient import of the HBV genome into mouse nuclei and thereby
block the viral life-cycle in mice. To test this hypothesis, I will first extend our analysis to all karyopherins involved
in nuclear import; I will systematically compare the ability of the respective mouse and human orthologues to
facilitate infection in mouse cells and map subsequently the species-tropism defining regions in KPNA2 and
putatively other karyopherins. Results from this aim will highlight the human-specific dependency factors needed
to break the species barrier for HBV infection in murine cells. Secondly, I aim to determine how human
karyopherins enhance HBV infection in murine cells mechanistically. I hypothesize that human but not mouse
KPNA2, and other karyopherins, can facilitate the import of rcDNA HBV capsids into the nucleus through direct
physical interactions. To test this systematically, I will visualize the subcellular localization of HBV capsids in the
presence of human versus mouse KPNA2 by confocal microscopy. I will further test the relative ability of human
and mouse KPNA2 to bi...

## Key facts

- **NIH application ID:** 10902325
- **Project number:** 1F31AI183827-01
- **Recipient organization:** PRINCETON UNIVERSITY
- **Principal Investigator:** Jenny Nneka Ijoma
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $32,974
- **Award type:** 1
- **Project period:** 2024-05-01 → 2025-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10902325

## Citation

> US National Institutes of Health, RePORTER application 10902325, Delineating the impact of human karyopherins on hepatitis B virus species tropism (1F31AI183827-01). Retrieved via AI Analytics 2026-05-27 from https://api.ai-analytics.org/grant/nih/10902325. Licensed CC0.

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