Changes to the Natural Killer Cell Repertoire after Therapeutic Hepatitis B DNA Vaccination

BackgroundImprovements to the outcome of adaptive immune responses could be achieved by inducing specific natural killer (NK) cell subsets which can cooperate with dendritic cells to select efficient T cell responses. We previously reported the induction or reactivation of T cell responses in chronic hepatitis B patients vaccinated with a DNA encoding hepatitis B envelope proteins during a phase I clinical trial.
Methodology/Principal FindingsIn this study, we examined changes in the peripheral NK cell populations occurring during this vaccine trial using flow cytometry analysis. Despite a constant number of NK cells in the periphery, a significant increase in the CD56bright population was observed after each vaccination and during the follow up. Among the 13 different NK cell markers studied by flow cytometry analysis, the expression of CD244 and NKG2D increased significantly in the CD56bright NK population. The ex vivo CD107a expression by CD56bright NK cells progressively increased in the vaccinated patients to reach levels that were significantly higher compared to chronically HBV-infected controls. Furthermore, modifications to the percentage of the CD56bright NK cell population were correlated with HBV-specific T cell responses detected by the ELISPOT assay.
Conclusions/SignificanceThese changes in the CD56bright population may suggest a NK helper effect on T cell adaptive responses. Activation of the innate and adaptive arms of the immune system by DNA immunization may be of particular importance to the efficacy of therapeutic interventions in a context of chronic infections.
Trial RegistrationClinicalTrials.gov NCT00988767

研究背景：通过诱导可与树突状细胞（dendritic cells, DC）协同筛选高效T细胞应答的特定自然杀伤（natural killer, NK）细胞亚群，可改善适应性免疫应答的结局。本团队此前在一项I期临床试验中报道，对慢性乙型肝炎患者接种编码乙型肝炎包膜蛋白的DNA疫苗后，可诱导或重新激活其T细胞应答。
方法与主要结果：本研究采用流式细胞术（flow cytometry）分析，对该疫苗临床试验期间受试者外周血NK细胞群体的变化进行了检测。尽管外周血NK细胞总数保持稳定，但每次接种疫苗后及随访阶段，CD56bright NK细胞亚群的比例均显著升高。在流式细胞术检测的13种NK细胞标志物中，CD56bright NK细胞群体的CD244与NKG2D表达水平均显著上调。接种疫苗的患者体内，CD56bright NK细胞的离体CD107a表达水平逐渐升高，最终显著高于慢性乙型肝炎病毒（hepatitis B virus, HBV）感染对照组。此外，CD56bright NK细胞亚群比例的变化与通过ELISPOT实验检测到的HBV特异性T细胞应答呈显著相关。
结论与意义：CD56bright NK细胞亚群的上述变化提示，NK细胞可对T细胞适应性应答发挥辅助作用。通过DNA免疫激活免疫系统的先天及适应性免疫分支，或许对慢性感染背景下治疗干预的疗效具有特殊重要性。
试验注册：ClinicalTrials.gov NCT00988767