Rexhouse Catherine, Bailey Jacob T, Moshkani Safiehkhatoon, Cimino Jesse L, Robek Michael D
Department of Immunology and Microbial Disease, Albany Medical College, Albany, New York, USA.
J Virol. 2025 Jul 22;99(7):e0071125. doi: 10.1128/jvi.00711-25. Epub 2025 Jun 12.
Chronic hepatitis B virus (HBV) infection is characterized by dysfunctional HBV-specific CD8+ T cell responses that contribute to viral persistence. Understanding the mechanisms behind this dysfunction is necessary to develop effective immunotherapies. Here, we used the adeno-associated virus (AAV)-HBV mouse model of HBV replication to investigate the development of CD8+ T cell dysfunction during chronic HBV infection. Unlike naïve mice, AAV-HBV mice with intermediate to high viral antigen levels failed to respond to therapeutic immunization against HBV antigens, indicating that failure to initially induce HBV-specific CD8+ T cell responses cannot account for the entirety of the observed CD8+ T cell dysfunction. Similarly, mice challenged with a high dose of AAV-HBV could not control antigenemia despite initially functional CD8+ T cell responses generated by immunization. These mice exhibited rapid CD8+ T cell functional impairment, marked by reduced cytokine production and increased expression of the inhibitory receptor PD-1. In contrast, mice challenged with a lower dose of AAV-HBV effectively controlled viral antigens and maintained CD8+ T cell function. Combination treatment with therapeutic immunization and antibody-mediated PD-1 and CTLA-4 blockade partially reduced HBsAg levels in mice with intermediate but not higher antigen burdens. These findings indicate that during chronic HBV infection, high antigen expression is an important factor driving a CD8+ T cell dysfunction that cannot be easily reversed and may limit the efficacy of some immunotherapeutic approaches.IMPORTANCEDespite available preventative vaccines, chronic hepatitis B virus (HBV) infection remains a major cause of liver disease worldwide, with no adequate cure. Challenges in developing effective immunotherapies include our incomplete understanding of immune dysfunction mechanisms and limited representative animal models. Here, we further characterized CD8+ T cell dysfunction mechanisms in the AAV-HBV mouse model, which shares some immunological features with human chronic HBV infection (CHB). We observed that high but not low antigen levels induced CD8+ T cell dysfunction marked by elevated PD-1 expression and led to viral persistence, despite HBsAg clearance. Additionally, responsiveness to combination immunotherapies was influenced by antigen levels at the time of treatment. This work illustrates the interplay between antigen load, immune checkpoints, and immune tolerance during CHB and may offer insights into potential strategies for enhancing HBV-specific immune responses to promote a functional cure.
慢性乙型肝炎病毒（HBV）感染的特征是HBV特异性CD8 + T细胞反应功能失调，这有助于病毒持续存在。了解这种功能失调背后的机制对于开发有效的免疫疗法至关重要。在这里，我们使用HBV复制的腺相关病毒（AAV）-HBV小鼠模型来研究慢性HBV感染期间CD8 + T细胞功能失调的发展。与未感染的小鼠不同，具有中等至高病毒抗原水平的AAV-HBV小鼠对针对HBV抗原的治疗性免疫无反应，这表明最初未能诱导HBV特异性CD8 + T细胞反应并不能解释观察到的CD8 + T细胞功能失调的全部情况。同样，尽管通过免疫产生了最初具有功能的CD8 + T细胞反应，但用高剂量AAV-HBV攻击的小鼠仍无法控制抗原血症。这些小鼠表现出快速的CD8 + T细胞功能损伤，其特征是细胞因子产生减少和抑制性受体PD-1表达增加。相比之下，用较低剂量AAV-HBV攻击的小鼠有效地控制了病毒抗原并维持了CD8 + T细胞功能。治疗性免疫与抗体介导的PD-1和CTLA-4阻断的联合治疗部分降低了抗原负荷中等但不是更高的小鼠的HBsAg水平。这些发现表明，在慢性HBV感染期间，高抗原表达是驱动CD8 + T细胞功能失调的一个重要因素，这种功能失调不易逆转，可能会限制一些免疫治疗方法的疗效。
重要性
尽管有预防性疫苗可用，但慢性乙型肝炎病毒（HBV）感染仍然是全球肝病的主要原因，且尚无足够的治愈方法。开发有效免疫疗法的挑战包括我们对免疫功能失调机制的不完全理解以及代表性动物模型有限。在这里，我们进一步表征了AAV-HBV小鼠模型中CD8 + T细胞功能失调机制，该模型与人类慢性HBV感染（CHB）具有一些免疫学特征。我们观察到，高抗原水平而非低抗原水平会诱导以PD-1表达升高为特征的CD8 + T细胞功能失调，并导致病毒持续存在，尽管HBsAg已清除。此外，对联合免疫疗法的反应性受治疗时抗原水平的影响。这项工作说明了CHB期间抗原负荷、免疫检查点和免疫耐受之间的相互作用，并可能为增强HBV特异性免疫反应以促进功能性治愈的潜在策略提供见解。
