Kruse Robert L, Barzi Mercedes, Legras Xavier, Pankowicz Francis P, Furey Nika, Liao Lan, Xu Janming, Bissig-Choisat Beatrice, Slagle Betty L, Bissig Karl-Dimiter
Center for Cell and Gene Therapy, Texas Children's Hospital, Houston Methodist Hospital, Baylor College of Medicine, Houston, TX, USA.
Center for Stem Cells and Regenerative Medicine, Baylor College of Medicine, Houston, TX, USA.
JHEP Rep. 2021 Feb 6;3(2):100252. doi: 10.1016/j.jhepr.2021.100252. eCollection 2021 Apr.
BACKGROUND & AIMS: Development of new and more effective therapies against hepatitis B virus (HBV) is limited by the lack of suitable small animal models. The HBV transgenic mouse model containing an integrated overlength 1.3-mer construct has yielded crucial insights, but this model unfortunately lacks covalently closed circular DNA (cccDNA), the episomal HBV transcriptional template, and cannot be cured given that HBV is integrated in every cell.
To solve these 2 problems, we generated a novel transgenic mouse (HBV1.1X), which generates an excisable circular HBV genome using Cre/LoxP technology. This model possesses a HBV1.1-mer cassette knocked into the locus and is designed for stable expression of viral proteins from birth, like the current HBV transgenic mouse model, before genomic excision with the introduction of Cre recombinase.
We demonstrated induction of recombinant cccDNA (rcccDNA) formation via viral or transgenic Cre expression in HBV1.1X mice, and the ability to regulate HBsAg and HBc expression with Cre in mice. Tamoxifen-inducible Cre could markedly downregulate baseline HBsAg levels from the integrated HBV genome. To demonstrate clearance of HBV from HBV1.1X mice, we administered adenovirus expressing Cre, which permanently and significantly reduced HBsAg and core antigen levels in the murine liver via rcccDNA excision and a subsequent immune response.
The HBV1.1X model is the first Cre-regulatable HBV transgenic mouse model and should be of value to mimic chronic HBV infection, with neonatal expression and tolerance of HBV antigens, and on-demand modulation of HBV expression.
Hepatitis B virus (HBV) can only naturally infect humans and chimpanzees. Mouse models have been developed with the HBV genome integrated into mouse chromosomes, but this prevents mice from being cured. We developed a new transgenic mouse model that allows for HBV to be excised from mouse chromosomes to form a recombinant circular DNA molecule resembling the natural circular HBV genome. HBV expression could be reduced in these mice, enabling curative therapies to be tested in this new mouse model.
新型且更有效的抗乙型肝炎病毒（HBV）疗法的研发受到缺乏合适小动物模型的限制。包含整合的超长1.3倍体构建体的HBV转基因小鼠模型已产生了关键见解，但不幸的是，该模型缺乏共价闭合环状DNA（cccDNA），即游离型HBV转录模板，并且由于HBV整合在每个细胞中，无法被治愈。
为了解决这两个问题，我们构建了一种新型转基因小鼠（HBV1.1X），它利用Cre/LoxP技术产生可切除的环状HBV基因组。该模型具有敲入特定基因座的HBV1.1倍体盒式结构，并且设计成从出生起就稳定表达病毒蛋白，类似于当前的HBV转基因小鼠模型，直到通过引入Cre重组酶进行基因组切除。
我们证明了在HBV1.1X小鼠中通过病毒或转基因表达Cre可诱导重组cccDNA（rcccDNA）形成，以及在小鼠中用Cre调节HBsAg和HBc表达的能力。他莫昔芬诱导型Cre可显著下调整合的HBV基因组的基线HBsAg水平。为了证明从HBV1.1X小鼠中清除HBV，我们给予表达Cre的腺病毒，其通过rcccDNA切除和随后的免疫反应永久性且显著降低了小鼠肝脏中的HBsAg和核心抗原水平。
HBV1.1X模型是首个可由Cre调节的HBV转基因小鼠模型，对于模拟慢性HBV感染、HBV抗原的新生儿表达和耐受性以及按需调节HBV表达应具有价值。
乙型肝炎病毒（HBV）仅能自然感染人类和黑猩猩。已开发出将HBV基因组整合到小鼠染色体中的小鼠模型，但这使得小鼠无法被治愈。我们开发了一种新的转基因小鼠模型，该模型允许从小鼠染色体中切除HBV以形成类似于天然环状HBV基因组的重组环状DNA分子。在这些小鼠中HBV表达可降低，从而能够在这个新的小鼠模型中测试治愈性疗法。
