A New Adenovirus Based Vaccine Vector Expressing an <em>Eimeria tenella</em> Derived TLR Agonist Improves Cellular Immune Responses to an Antigenic Target

BackgroundAdenoviral based vectors remain promising vaccine platforms for use against numerous pathogens, including HIV. Recent vaccine trials utilizing Adenovirus based vaccines expressing HIV antigens confirmed induction of cellular immune responses, but these responses failed to prevent HIV infections in vaccinees. This illustrates the need to develop vaccine formulations capable of generating more potent T-cell responses to HIV antigens, such as HIV-Gag, since robust immune responses to this antigen correlate with improved outcomes in long-term non-progressor HIV infected individuals. Methodology/Principal FindingsIn this study we designed a novel vaccine strategy utilizing an Ad-based vector expressing a potent TLR agonist derived from Eimeria tenella as an adjuvant to improve immune responses from a [E1-]Ad-based HIV-Gag vaccine. Our results confirm that expression of rEA elicits significantly increased TLR mediated innate immune responses as measured by the influx of plasma cytokines and chemokines, and activation of innate immune responding cells. Furthermore, our data show that the quantity and quality of HIV-Gag specific CD8+ and CD8− T-cell responses were significantly improved when coupled with rEA expression. These responses also correlated with a significantly increased number of HIV-Gag derived epitopes being recognized by host T cells. Finally, functional assays confirmed that rEA expression significantly improved antigen specific CTL responses, in vivo. Moreover, we show that these improved responses were dependent upon improved TLR pathway interactions. Conclusion/SignificanceThe data presented in this study illustrate the potential utility of Ad-based vectors expressing TLR agonists to improve clinical outcomes dependent upon induction of robust, antigen specific immune responses.【背景】以腺病毒载体（Adenoviral vector）为基础的疫苗平台，仍是对抗包括人类免疫缺陷病毒（HIV）在内的多种病原体的极具潜力的疫苗研发方向。近期多项基于表达HIV抗原的腺病毒载体疫苗的临床试验证实，该类疫苗可诱导细胞免疫应答，但却无法使疫苗接种者免受HIV感染。这一现状凸显出开发新型疫苗制剂的必要性——这类制剂需能够诱导针对HIV抗原（如HIV-Gag）的更强效T细胞应答，因为在HIV长期非进展者中，针对该抗原的强免疫应答与更佳的临床转归密切相关。【方法学/主要研究结果】本研究设计了一种新型疫苗策略：利用携带源自柔嫩艾美耳球虫（Eimeria tenella）的强效Toll样受体激动剂（Toll-like receptor agonist, TLR agonist）的腺病毒载体作为佐剂，以优化基于缺失E1区的腺病毒载体（[E1-]Ad）的HIV-Gag疫苗所诱导的免疫应答。研究结果证实，rEA的表达可显著增强TLR介导的天然免疫应答，这一效应可通过血浆细胞因子与趋化因子的募集、天然免疫应答细胞的活化水平得以量化验证。此外，本研究数据显示，当联合rEA表达时，HIV-Gag特异性CD8+及CD8- T细胞应答的数量与质量均得到显著提升；这类应答同时与宿主T细胞所识别的HIV-Gag来源表位数量显著增加相关。最后，功能实验证实，rEA的表达可在体内显著增强抗原特异性细胞毒性T淋巴细胞（CTL）应答。进一步研究表明，上述免疫应答的改善依赖于TLR信号通路相互作用的增强。【结论与意义】本研究呈现的数据表明，表达TLR激动剂的腺病毒载体，在依赖于诱导强抗原特异性免疫应答的临床场景中，具备潜在的应用价值。