Department of Experimental Medicine and Surgery, University of Rome Tor Vergata, Rome, Italy.
Hepatology. 2015 Mar;61(3):823-33. doi: 10.1002/hep.27604. Epub 2015 Jan 28.
Hepatitis B virus (HBV) reactivation during immunosuppression can lead to severe acute hepatitis, fulminant liver failure, and death. Here, we investigated hepatitis B surface antigen (HBsAg) genetic features underlying this phenomenon by analyzing 93 patients: 29 developing HBV reactivation and 64 consecutive patients with chronic HBV infection (as control). HBsAg genetic diversity was analyzed by population-based and ultradeep sequencing (UDS). Before HBV reactivation, 51.7% of patients were isolated hepatitis B core antibody (anti-HBc) positive, 31.0% inactive carriers, 6.9% anti-HBc/anti-HBs (hepatitis B surface antibody) positive, 6.9% isolated anti-HBs positive, and 3.4% had an overt HBV infection. Of HBV-reactivated patients, 51.7% were treated with rituximab, 34.5% with different chemotherapeutics, and 13.8% with corticosteroids only for inflammatory diseases. In total, 75.9% of HBV-reactivated patients (vs. 3.1% of control patients; P<0.001) carried HBsAg mutations localized in immune-active HBsAg regions. Of the 13 HBsAg mutations found in these patients, 8 of 13 (M103I-L109I-T118K-P120A-Y134H-S143L-D144E-S171F) reside in a major hydrophilic loop (target of neutralizing antibodies [Abs]); some of them are already known to hamper HBsAg recognition by humoral response. The remaining five (C48G-V96A-L175S-G185E-V190A) are localized in class I/II-restricted T-cell epitopes, suggesting a role in HBV escape from T-cell-mediated responses. By UDS, these mutations occurred in HBV-reactivated patients with a median intrapatient prevalence of 73.3% (range, 27.6%-100%) supporting their fixation in the viral population as a predominant species. In control patients carrying such mutations, their median intrapatient prevalence was 4.6% (range, 2.5%-11.3%; P<0.001). Finally, additional N-linked glycosylation (NLG) sites within the major hydrophilic loop were found in 24.1% of HBV-reactivated patients (vs. 0% of chronic patients; P<0.001); 5 of 7 patients carrying these sites remained HBsAg negative despite HBV reactivation. NLG can mask immunogenic epitopes, abrogating HBsAg recognition by Abs.
HBV reactivation occurs in a wide variety of clinical settings requiring immune-suppressive therapy, and correlates with HBsAg mutations endowed with enhanced capability to evade immune response. This highlights the need for careful patient monitoring in all immunosuppressive settings at reactivation risk and of establishing a prompt therapy to prevent HBV-related clinical complications.
研究免疫抑制期间乙型肝炎病毒（HBV）再激活的现象，分析导致这种现象的乙肝表面抗原（HBsAg）遗传特征。
我们分析了 93 例患者：29 例发生 HBV 再激活，64 例连续慢性 HBV 感染患者（作为对照）。通过基于人群的和超深度测序（UDS）分析 HBsAg 遗传多样性。在 HBV 再激活之前，51.7%的患者单独乙型肝炎核心抗体（抗-HBc）阳性，31.0%为非活动携带者，6.9%抗-HBc/抗-HBs（乙型肝炎表面抗体）阳性，6.9%单独抗-HBs 阳性，3.4%为显性 HBV 感染。在 HBV 再激活的患者中，51.7%接受利妥昔单抗治疗，34.5%接受不同的化疗药物治疗，13.8%仅因炎症性疾病接受皮质类固醇治疗。共有 75.9%的 HBV 再激活患者（vs. 3.1%的对照组患者；P<0.001）携带定位于免疫活性 HBsAg 区域的 HBsAg 突变。在这些患者中发现的 13 种 HBsAg 突变中，13 种中的 8 种（M103I-L109I-T118K-P120A-Y134H-S143L-D144E-S171F）位于主要亲水环（中和抗体的靶标）中；其中一些已被证明会阻碍体液免疫对 HBsAg 的识别。其余 5 种（C48G-V96A-L175S-G185E-V190A）定位于 I 类/II 类受限的 T 细胞表位，提示其在 HBV 逃避 T 细胞介导的反应中起作用。通过 UDS，这些突变发生在 HBV 再激活患者中，患者个体内的中位流行率为 73.3%（范围为 27.6%-100%），支持它们作为主要种在病毒群体中固定下来。在携带这些突变的对照组患者中，其个体内的中位流行率为 4.6%（范围为 2.5%-11.3%；P<0.001）。最后，在 24.1%的 HBV 再激活患者中发现主要亲水环内的额外 N 连接糖基化（NLG）位点（vs. 慢性患者的 0%；P<0.001）；尽管 HBV 再激活，但 7 名携带这些位点的患者中有 5 名 HBsAg 仍为阴性。NLG 可以掩盖免疫原性表位，从而阻止 Abs 对 HBsAg 的识别。
HBV 再激活发生在需要免疫抑制治疗的广泛临床环境中，与具有增强逃避免疫反应能力的 HBsAg 突变相关。这突出表明，需要在所有存在 HBV 再激活风险的免疫抑制环境中密切监测患者，并及时进行治疗，以预防 HBV 相关的临床并发症。
