2021-09-012024-05-13https://scholars.lib.ntu.edu.tw/handle/123456789/654563B型肝炎病毒（hepatitis B virus, HBV）以一群稱為類種之極相近變異種形式存在於受感染者體內，且有10種約8%趨異性之基因型。HBV感染造成從自發性痊癒至包含肝衰竭、肝硬化、肝腫瘤等嚴重度不同的疾病表現。至今全球有超過2.4億人受慢性B型肝炎（chronic hepatitis B）影響，因此仍為公共衛生的一項挑戰性的議題。曾有研究指出受在台灣主要傳播的HBV基因型B與C感染之慢性B型肝炎有不同的臨床結果。在慢性B型肝炎自然病史中依據不同的免疫狀態所區分的4種疾病階段需要被謹慎地定義。宿主抗HBV免疫力在免疫耐受期可能處於休眠狀態，尤其是此時未能誘發正常之具HBV專一性之T細胞免疫反應。慢性B型肝炎病程中的第一個轉捩點為B型肝炎病毒e抗原（HBeAg）消失伴隨著出現抗HBeAg抗體之陰轉（seroconversion）。此一現象表示由免疫活化期進入低病毒複製（病毒量< 2000 IU/ml）的階段。雖然大部分HBeAg自然陰轉的病人有較佳的臨床結果，然有少部分遭受伴隨著肝炎發生的HBV再活化，定義為病毒量超過2000 IU/ml及正常丙胺酸轉氨&#37238;正常值2倍之HBeAg陰性肝炎（HBeAg-negative hepatitis, ENH）。在人類免疫不全病毒（human immunodeficiency virus, HIV）與C型肝炎病毒（hepatitis C virus, HCV）研究已知在人體內病毒適應毒殺型T細胞免疫力藉由第一型人類白血球抗原（class I human leukocyte antigen, HLA）相關病毒多樣性展現，但此現象尚未在HBV相關研究中清楚地證實。我們在先前的研究中已發現病毒類種變異度可以做為慢性B型肝炎病人的抗病毒免疫力的生物標誌。其可能原因是抗病毒免疫力，尤其是毒殺型T細胞免疫力，可抑制病毒複製與驅動病毒變異，因此變異性大的病毒類種與較佳的病毒控制相關。在此研究計畫中，我們將完成3個目標，第一個目標為尋找HLA相關宿主內單一核酸變異株（intra-host single nucleotide variants, iSNVs）與其同源的T細胞反應；第二個目標將鑑別HBV基因型B與C之保護性與病原性抗原表位（protective/pathogenic epitopes）及其與疾病嚴重度之相關性；第三個目標將利用免疫&#32957;組學與周邊血中毒殺型T細胞免疫反應研究證實具HBV專一性class I HLA限制epitopes之存在。因為病毒類種與宿主後天性免疫反應之內生性連結目前仍有許多尚待釐清之處，藉著研究病毒適應毒殺型T細胞免疫，我們將可發現具保護性或致病性之T細胞 epitopes，可以用來提供發展合適的早期慢性B型肝炎治療與發現以T細胞為基礎的抗病毒治療標的之重要線索。 Hepatitis B virus (HBV) within an infected individual is a swarm of closely related variants known as quasispecies and contains 10 genotypes with approximate 8% of divergence. HBV infection leads to a broad spectrum of disease outcomes, ranging from spontaneous resolution to severe consequences, including hepatic failure, cirrhosis, and hepatocellular carcinoma (HCC). It remains a challenging issue of global public health that more than 240 million people are living with chronic hepatitis B (CHB). It has been reported that CHB patients with genotypes B and C infection, which are the predominant genotypes in Taiwan, exhibit distinct clinical outcomes. Four distinct disease phases corresponding to different immune statuses require to be cautiously defined in the natural history of CHB. In the immune-tolerant phase, the host immunity against HBV, particularly the HBV-specific T cell immunity, is possibly dormant, but is then ignited to cause hepatitis upon entry to the immune-clearance phase. The first turning point of CHB disease progression is the seroconversion of hepatitis B e antigen (HBeAg) defined as loss of HBeAg accompanied by the appearance of anti-HBeAg antibody. It signifies transition from an immune active phase to the relatively low viral replication (viral load < 2,000 IU/ml). Although the majority of patients undergoing HBeAg seroconversion exhibit a favorable outcome, some of them suffer from HBV reactivation with hepatitis activity, termed HBeAg-negative hepatitis (ENH), which is defined as viral load 2000 IU/ml with 2-fold elevation of normal alanine aminotransferase (ALT). Viral adaptation to cytotoxic T cell immunity, evident by class I HLA-associated viral polymorphisms in human population, has been well established in HIV and HCV, but not yet clearly demonstrated in HBV. We have previously reported that viral quasispecies diversity could serve as the biomarker for antiviral immunity in CHB patients. It is possible that antiviral immunity, particularly cytotoxic T cell immunity, suppresses viral replication and drives viral diversification as well, linking the diversified viral quasispecies to better viral control. In this project, we propose three specific aims: (1) to identify HLA-associated intra-host single nucleotide variants (iSNVs) and cognate T cell response; (2) to discriminate protective/pathogenic epitopes between HBV genotypes B and C and the association to disease severity; (3) to verify HBV-specific class I HLA-restricted epitopes by immunopeptidomics and peripheral cytotoxic T cell response. Since the intrinsic connection between viral quasispecies and host adaptive immunity remains largely unknown, by investigating the viral adaptation to cytotoxic T cell immunity, we will identify the protective/pathogenic epitopes which may provide the important clues for optimizing early CHB treatment and identifying potential targets for developing T cell-based antiviral therapy.B型肝炎病毒類種病毒適應宿主內單一核酸變異株毒殺型T細胞免疫以T細胞為基礎的抗病毒治療HBV quasispeciesViral adaptation; intra-host single nucleotide variants (iSNVs)cytotoxic T cell immunityT cell-based antiviral therapy