CD8+ T細胞保守性抗原於HLA轉基因小鼠流感病毒感染中之免疫主導階層與保護性研究

Abstract

流感病毒是一種高度變異的 RNA 病毒，具有高突變率與人畜共通感染的潛力，經常引發季節性流行與全球性大流行，對全球公共衛生構成重大威脅。目前市面上的流感疫苗多針對病毒外部蛋白如血球凝集素 (HA) 與神經胺酸酶 (NA) 設計，雖然這樣的設計可提供良好保護力，卻因病毒突變快速而需每年重新預測及更新。相較之下，T 細胞能辨識整個病毒蛋白體中的抗原，增加辨識保守性 T 細胞表位的可能性。T 細胞表位 (epitope) 的免疫優勢性層級 (immunodominance hierarchy) 對免疫反應的效果具有關鍵影響，其免疫原性、抗原表現量以及與 MHC 分子結合親和力的差異，皆可影響表位的優勢程度。免疫優勢表位 (dominant epitope) 通常誘發較強的免疫反應並提供較佳保護，但也可能因選擇壓力反而促使病毒產生逃脫突變株。相對地，次優勢表位 (subdominant epitopes) 雖引發的反應較弱，卻能在優勢表位突變時作為備用目標。瞭解這些保守性表位的免疫優勢性與保護力，是發展出可以廣泛對抗多種流感病毒株同時具有持久免疫力之 T 細胞疫苗的關鍵步驟。因此，本研究旨在利用表達人類常見 HLA 分子的 HLA 轉基因小鼠 (HLA-A02 或 HLA-A11)，去測量本實驗室先前鑑定或他人已發表過之保守性 T 細胞表位的免疫優勢層級與保護效果。首先我們在 HLA 轉基因小鼠量測台灣 2009 年臨床流行株 TW126 (H1N1) 的感染劑量，隨後以細胞內細胞激素染色 (ICS) 與 peptide-MHC 四聚體染色分析病毒感染後的 T 細胞反應，並進一步針對保守性表位分析其所誘發的 T 細胞免疫反應，以評估各表位的免疫優勢層級與保護潛力。未來，我們也將持續探討這些保守表位的保護效果及其開發更有效且具廣效性的流感T細胞疫苗之潛力。

Influenza is a rapidly evolving RNA virus characterized by high mutation rates and zoonotic potential, leading to seasonal outbreaks and pandemics that pose a major threat to global public health. Current influenza vaccines often target external viral proteins, hemagglutinin (HA) and neuraminidase (NA), offering strong protection but requiring annual updates. In contrast, T cells recognize antigens from the entire viral proteome, increasing the likelihood of identifying conserved T cell epitopes. The immunodominance hierarchy of T cell epitopes plays a critical role in shaping immune response effectiveness. Variations in immunogenicity, expression levels, and binding affinities to MHC molecules contribute to distinct dominance patterns, which typically induce stronger immune responses and offer better protection but can also exert selection pressure, leading to escape mutants. In contrast, subdominant epitopes, while eliciting weaker responses, serve as essential backups when mutations occur in dominant epitopes. Understanding the immunodominance hierarchy and protectivity of the conserved T cell epitopes is a key step to develop a universal influenza T cell vaccine to provide durable and cross-strain immunity. Therefore, this study aimed to evaluate the immunodominance hierarchy and protectivity of the conserved T cell epitopes identified in our lab using HLA-transgenic mice that expressing the prevalent human HLAs, either HLA-A02 or HLA-A11. We first titrated the dose of IAV strain TW126 (H1N1), an isolate in 2009 pandemic in Taiwan, in HLA transgenic mice. We then analyzed the T cell response to influenza virus infection using intracellular cytokine staining and pMHC tetramer staining. Furthermore, we evaluated the T cell response to the conserved T cell epitopes to investigate their immunodominance hierarchy and their protective potential. The protective efficacy of these conserved epitopes and their potential in developing a more effective and universal T cell-based influenza vaccine will also be examined in future studies.