Balsitis Scott, Gali Volodymyr, Mason Pamela J, Chaniewski Susan, Levine Steven M, Wichroski Michael J, Feulner Michael, Song Yunling, Granaldi Karen, Loy James K, Thompson Chris M, Lesniak Jacob A, Brockus Catherine, Kishnani Narendra, Menne Stephan, Cockett Mark I, Iyer Renuka, Mason Stephen W, Tenney Daniel J
Virology Discovery, Bristol-Myers Squibb, Wallingford, Connecticut, United States of America.
Discovery Toxicology, Bristol-Myers Squibb, Princeton, New Jersey, United States of America.
PLoS One. 2018 Feb 14;13(2):e0190058. doi: 10.1371/journal.pone.0190058. eCollection 2018.
Immune clearance of Hepatitis B virus (HBV) is characterized by broad and robust antiviral T cell responses, while virus-specific T cells in chronic hepatitis B (CHB) are rare and exhibit immune exhaustion that includes programmed-death-1 (PD-1) expression on virus-specific T cells. Thus, an immunotherapy able to expand and activate virus-specific T cells may have therapeutic benefit for CHB patients. Like HBV-infected patients, woodchucks infected with woodchuck hepatitis virus (WHV) can have increased hepatic expression of PD-1-ligand-1 (PD-L1), increased PD-1 on CD8+ T cells, and a limited number of virus-specific T cells with substantial individual variation in these parameters. We used woodchucks infected with WHV to assess the safety and efficacy of anti-PD-L1 monoclonal antibody therapy (αPD-L1) in a variety of WHV infection states. Experimentally-infected animals lacked PD-1 or PD-L1 upregulation compared to uninfected controls, and accordingly, αPD-L1 treatment in lab-infected animals had limited antiviral effects. In contrast, animals with naturally acquired WHV infections displayed elevated PD-1 and PD-L1. In these same animals, combination therapy with αPD-L1 and entecavir (ETV) improved control of viremia and antigenemia compared to ETV treatment alone, but with efficacy restricted to a minority of animals. Pre-treatment WHV surface antigen (sAg) level was identified as a statistically significant predictor of treatment response, while PD-1 expression on peripheral CD8+ T cells, T cell production of interferon gamma (IFN-γ) upon in vitro antigen stimulation (WHV ELISPOT), and circulating levels of liver enzymes were not. To further assess the safety of this strategy, αPD-L1 was tested in acute WHV infection to model the risk of liver damage when the extent of hepatic infection and antiviral immune responses were expected to be the greatest. No significant increase in serum markers of hepatic injury was observed over those in infected, untreated control animals. These data support a positive benefit/risk assessment for blockade of the PD-1:PD-L1 pathway in CHB patients and may help to identify patient groups most likely to benefit from treatment. Furthermore, the efficacy of αPD-L1 in only a minority of animals, as observed here, suggests that additional agents may be needed to achieve a more robust and consistent response leading to full sAg loss and durable responses through anti-sAg antibody seroconversion.
乙型肝炎病毒（HBV）的免疫清除以广泛而强大的抗病毒T细胞反应为特征，而慢性乙型肝炎（CHB）中的病毒特异性T细胞很少，并且表现出免疫耗竭，包括病毒特异性T细胞上程序性死亡1（PD-1）的表达。因此，一种能够扩增和激活病毒特异性T细胞的免疫疗法可能对CHB患者具有治疗益处。与HBV感染患者一样，感染土拨鼠肝炎病毒（WHV）的土拨鼠肝脏中PD-1配体-1（PD-L1）表达增加，CD8+T细胞上的PD-1增加，并且病毒特异性T细胞数量有限，这些参数存在很大的个体差异。我们使用感染WHV的土拨鼠来评估抗PD-L1单克隆抗体疗法（αPD-L1）在多种WHV感染状态下的安全性和疗效。与未感染的对照相比，实验感染的动物缺乏PD-1或PD-L1上调，因此，实验室感染动物中的αPD-L1治疗具有有限的抗病毒作用。相比之下，自然感染WHV的动物表现出PD-1和PD-L1升高。在这些相同的动物中，与单独使用恩替卡韦（ETV）治疗相比，αPD-L1与ETV联合治疗改善了病毒血症和抗原血症的控制，但疗效仅限于少数动物。治疗前WHV表面抗原（sAg）水平被确定为治疗反应的统计学显著预测指标，而外周CD8+T细胞上的PD-1表达、体外抗原刺激（WHV ELISPOT）后T细胞产生的干扰素γ（IFN-γ）以及循环肝酶水平则不是。为了进一步评估该策略的安全性，在急性WHV感染中测试了αPD-L1，以模拟在肝脏感染程度和抗病毒免疫反应预计最大时肝损伤的风险。与感染但未治疗的对照动物相比，未观察到肝损伤血清标志物有显著增加。这些数据支持对CHB患者中PD-1:PD-L1通路阻断进行积极的效益/风险评估，并可能有助于识别最可能从治疗中受益的患者群体。此外，如此处观察到的，αPD-L1仅在少数动物中有效，这表明可能需要额外的药物来实现更强有力和一致的反应，从而通过抗sAg抗体血清转化导致完全sAg丧失和持久反应。
