开放科学(资源服务)标识码(OSID)的开放科学计划以二维码为入口,提供丰富的线上扩展功能,包括作者对论文背景的语音介绍、该研究的附加说明、与读者的交互问答、拓展学术圈等。读者“扫一扫”此二维码即可获得上述增值服务。
结核病是严重危害人类健康的慢性传染病,其治疗以化学药物治疗杀灭结核分枝杆菌(Mycobacterium tuberculosis,MTB)为主。但结核病不仅是一种细菌感染性疾病,也是一种免疫性疾病[1]。宿主固有免疫应答和适应性免疫应答在结核病控制中发挥重要作用。结核病患者通常存在固有免疫和适应性免疫功能方面的异常或免疫功能低下[1-2],对活动性结核病患者应用免疫制剂进行免疫干预治疗是近年来研究的热点之一。为此,中国人民解放军总医院第八医学中心结核病医学部、《中国防痨杂志》编辑委员会、中国医疗保健国际交流促进会结核病防治分会基础和临床学部联合组织专家拟定《活动性结核病患者免疫功能状态评估和免疫治疗专家共识(2021年版)》(简称《共识》)[3],全面介绍了抗结核免疫及结核病患者免疫异常机制,免疫治疗制剂的种类和临床应用,并提供了可供临床借鉴的具体建议。本文就《共识》中结核病患者免疫异常因素,活动性结核病患者免疫辅助治疗的概念,应用免疫制剂进行免疫干预的临床应用及存在问题及建议等进一步解读,供我国结核病临床工作者参考,以适时、合理地对活动性结核病患者进行个性化的免疫干预治疗,提高结核病的治疗成功率、减少复发率。
一、重视活动性结核病患者免疫异常因素
MTB入侵机体后,免疫系统识别MTB抗原,诱导宿主产生固有免疫应答和适应性免疫应答,以清除MTB,发挥重要的抗结核作用。固有免疫应答是先天性免疫应答,是机体抵御病原生物入侵的第一道防线。单核细胞、巨噬细胞、自然杀伤细胞、树突状细胞等固有免疫细胞是机体固有免疫应答的重要组成部分,他们具有吞噬作用,可针对MTB入侵迅速应答产生效应分子,抵抗MTB侵袭,清除巨噬细胞内的MTB,发挥非特异性抗结核免疫防御作用[4⇓⇓-7]。适应性免疫应答中,由T细胞(包括CD4+和CD8+T细胞等)介导的细胞免疫应答及其产生的辅助性T细胞1(Th1)型细胞因子[如γ-干扰素(IFN-γ)和白细胞介素2(IL-2)]发挥主要的抗结核保护性免疫应答作用;而其产生的Th2型细胞因子(如IL-4、IL-5及IL-10和转化生长因子-β)能够抑制Th1型细胞因子介导的保护性免疫应答,促进病变进展,导致坏死、空洞形成及病灶播散。两类细胞因子相互作用,相互制约,保持免疫应答在适当范围内,以保障既杀灭MTB又防止免疫过度造成组织病理损伤,Th1/Th2型细胞因子失衡影响结核病的发生和发展[8⇓⇓-11]。B淋巴细胞和抗体介导的体液免疫应答发挥辅助的抗结核作用。机体抗结核免疫主要依赖于固有免疫和(或)适应性免疫与MTB之间的相互作用,其决定了结核病的发展及预后。如宿主存在免疫功能异常,MTB进入人体后就不能及时清除感染的MTB,导致侵入部位或全身的慢性感染;同时,MTB在组织细胞内大量增殖会引起炎症及免疫损伤而发病。
《共识》指出:遗传因素、MTB诱导的免疫逃逸、导致宿主免疫功能低下的后天因素及衰老是导致抗结核免疫异常的主要因素。全球约有1/3人口感染MTB,只有5%~10%发病,而且结核病发病具有家族聚集倾向。这说明人类在抗MTB感染方面有家族遗传倾向。近年文献报道了较多与结核病发病相关的易感基因,如Toll样受体(Toll-like receptors,TLR)基因(TLR8、TLR4、TLR9、TLR2等)差异导致机体不能很好地激活固有免疫应答以抵抗MTB入侵[12]; 巨噬细胞移动抑制因子基因差异导致单核-巨噬细胞功能异常,肺泡内巨噬细胞吞噬MTB后形成不成熟的吞噬小体,并抑制巨噬细胞活化、吞噬溶酶体成熟,使MTB在巨噬细胞内长期潜伏,随时可能激活而导致发病[13-14];作为调理素促进吞噬作用和增强补体作用的甘露聚糖结合植物凝集素基因遗传缺陷会导致甘露聚糖结合植物凝集素缺乏,而易使结核病感染复发[15];许多结核病的罕见和常见遗传病因都会影响IFN-γ免疫[16],如程序性细胞凋亡1基因突变影响程序性细胞死亡蛋白1(programmed cell death protein 1,PD-1)表达,患者的淋巴细胞在分枝杆菌的刺激下只产生少量的IFN-γ,导致这些患者易患结核病[17],这些遗传因素控制了宿主的免疫应答能力,决定了个体对MTB的抵抗力差异,也为结核病免疫辅助治疗提供了理论基础,包括重组IFN-γ的使用。肺泡巨噬细胞是机体识别、吞噬、杀灭入侵MTB的重要免疫细胞。然而MTB感染机体后,可通过自身菌体成分、产物阻断和抑制机体的免疫应答,逃避机体免疫系统的监视和清除,产生免疫逃逸,从而长期潜伏于巨噬细胞中,形成持续性感染。MTB免疫逃逸机制有:(1)MTB可以通过以下途径抵抗巨噬细胞的杀伤作用:MTB诱导感染细胞组织蛋白酶的表达[18],阻止吞噬溶酶体的成熟,抑制吞噬体与溶酶体的融合[19],抑制巨噬细胞的凋亡[20],诱导或抑制肺泡巨噬细胞表达多种微小RNA(miRNA),调控巨噬细胞自噬过程,从而抑制巨噬细胞的自噬,增强MTB在巨噬细胞内的存活能力等[21-22]。(2)MTB通过抑制巨噬细胞的抗原递呈作用[23]和下调巨噬细胞对IFN-γ刺激应答的敏感性[24]等抑制抗结核适应性免疫应答。(3)MTB通过宿主泛素化系统抑制宿主的免疫防御,诱导免疫逃逸[25]。合并各种基础疾病(如合并艾滋病、糖尿病、尘肺病、恶性肿瘤等严重疾病),使用糖皮质激素、免疫抑制剂和化疗药物等细胞毒性药物,以及营养不良等均会导致MTB感染者免疫功能低下。
充分关注、综合评估结核病患者的免疫功能,对免疫功能异常或缺陷的活动性结核病患者进行早期、合理的免疫辅助治疗干预将提高这类患者的治愈率、病灶吸收率、痰菌阴转率。
二、关注抗结核免疫制剂的临床应用现状
结核病的“免疫治疗”,主要是应用免疫治疗制剂(依据用途可分为免疫增强剂、免疫抑制剂和免疫调节剂)辅助结核病化疗,以调节结核病引起的机体免疫功能低下或免疫异常,增强免疫活性,抑制不利的免疫应答和炎症损伤,达到对机体免疫功能激活、抑制或双向调节的作用,改变免疫应答状况,改善免疫功能,同时减轻免疫病理性损伤。结核病的免疫辅助治疗旨在提高抗结核化疗的效果,包括改善结核病患者临床症状、提高病灶吸收率和空洞闭合率、提高MTB清除率、缩短痰菌阴转时间,从而有助于缩短化疗疗程,减少化疗后复发,控制结核病疫情[26]。结核病免疫辅助治疗与抗肿瘤的免疫治疗有着本质的区别,主要起着辅助结核病化学治疗的作用,以提高疗效为目的。
《共识》通过大量文献检索,将已上市或进入临床试验阶段的结核病免疫辅助治疗制剂按来源分为免疫活性物质、治疗性疫苗、化学制剂、免疫抑制剂、中成药制剂等共5类。各类免疫制剂的具体作用机制,参照《共识》表4。《共识》详细列出了能检索到已上市或正在进入临床研究阶段的各类制剂。其中,免疫活性物质含细胞因子[含重组人γ-干扰素(rhuIFN-γ)和重组人白细胞介素2(rhuIL-2)]和小分子活性肽(胸腺肽、注射用胸腺五肽和胸腺法新)。治疗性疫苗包含灭活疫苗和亚单位疫苗,灭活疫苗由非结核分枝杆菌制备,已获得新药证书用于结核病治疗的有母牛分枝杆菌菌苗和草分枝杆菌菌苗,已进入临床研究阶段的有母牛分枝杆菌口服胶囊制剂(V7)、MIP、DAR-901和RUT1;亚单位疫苗是提取MTB具有免疫活性的细胞组分制成的,在我国获得新药证书并用于临床治疗的只有卡介苗多糖核酸注射液,作为预防性疫苗的4个结核病重组蛋白亚单位疫苗(Mtb72f/ASO1、H56/IC31、ID93/GLA-SE和AEC/BCO2)已进入Ⅰ或Ⅱ期临床试验,尚未见用于结核病治疗的临床研究报道。二甲双胍、左旋咪唑、维生素D、槲皮素和聚乙烯吡咯烷酮、大蒜素、柳氮磺吡啶等许多化学药品经临床试验或动物实验已证明具有免疫干预作用,已应用于抗结核临床研究或动物实验。免疫抑制剂糖皮质激素、沙利度胺具有抗炎和(或)免疫调节作用。中成药治疗肺结核(中医称“肺痨”)可扶助正气,提高机体免疫功能,协同西药发挥抗结核作用,目前临床应用的中成药有肺泰胶囊、芪甲利肺胶囊、结核丸、抗痨胶囊或抗痨丸、疗肺宁片等。上述制剂通过增强免疫功能和(或)免疫调节,或通过免疫抑制起到辅助治疗结核病的作用,但确切机制尚不明确。
《共识》提到rhuIFN-γ(中级证据,强推荐)、rhuIL-2(低级证据,弱推荐)、胸腺肽(中级证据,弱推荐)、注射用胸腺五肽和胸腺法新(中级证据,弱推荐)、母牛分枝杆菌菌苗(高级证据,强推荐)、草分枝杆菌菌苗(中级证据,弱推荐)、中成药制剂(中级证据,强推荐)辅助治疗复治肺结核或耐多药结核病,可能改善患者的临床症状和免疫功能状态,促进痰菌阴转、病灶吸收,提高疗效。其中,所有中、低级证据,弱推荐的制剂辅助抗结核的疗效仍需规范的多中心、大样本随机对照试验进一步证实。
目前,所有免疫辅助治疗制剂的临床应用方案、疗程均需参考相应的药品说明书用药,且大多数尚缺乏治疗结核病的用法和用量的相关建议。
三、把握活动性结核病患者免疫辅助治疗的应用指征
结核病的发生、发展及转归,人体的免疫系统发挥了重要作用。目前,抗结核治疗的主要方案仍是使用化学药物治疗,但是在治疗过程经常存在个体间疗效差异,以及耐多药结核病治疗效果差、药物耐受等问题。针对结核病患者存在的免疫异常或免疫功能低下,选择合适的免疫治疗制剂和方法调节活动性结核病患者的免疫状态,提高其抗结核免疫功能,以达到更好的清除MTB的目的,抗结核的宿主导向治疗(host-directed therapy,HDT)被提出。HDT可能通过激活AMP依赖性蛋白激酶分子,诱导MTB感染细胞的自噬,达到清除MTB作用[27],也可能通过触发多种炎症反应等提高机体抵抗MTB能力。它与结核病免疫辅助治疗概念基本相同。
《共识》最后一节指出,对于通过各种免疫相关检查后评估为抗结核免疫功能低下的结核病患者或年龄≥60周岁、病变广泛、病情严重或复治/耐多药结核病、合并反复和(或)严重感染尤其是HIV感染、合并糖尿病、合并营养不良、有免疫缺陷病家族史的结核病患者应该予免疫辅助治疗。对免疫治疗制剂过敏者、怀孕或哺乳期妇女、正在接受免疫抑制治疗的患者禁止使用免疫辅助治疗。
目前,免疫干预联合抗结核药物治疗结核病已在临床应用并取得一定疗效,但仍有很多问题尚需解决,如:(1)结核病患者的免疫辅助治疗应该个体化,对免疫功能低下、可能会出现MTB播散,甚至发展为播散性结核病的患者应给予免疫增强剂;而对于免疫应答过度者,如干酪性肺炎患者,可以适当给予免疫调节剂;但结核病患者免疫状态的评估方法有待深入研究,目前尚难达到精准的免疫辅助治疗;(2)抗结核免疫及免疫治疗制剂的具体作用机制尚未完全清楚;(3)尚缺乏有效的抗结核免疫制剂选择策略,免疫制剂的应用对象、应用时机、用法、用量、疗程、免疫辅助治疗对免疫功能的影响等尚缺乏深入研究;(4)在临床应用PD-1抑制剂治疗恶性肿瘤的过程中,逐渐出现MTB感染再活动的病例报道[28],探究PD-1信号转导通路在MTB感染免疫中作用及其调控机制,可以探索新的结核病HDT方案;(5)细胞免疫辅助治疗的安全性和有效性已经在抗结核治疗的临床试验中得到确认,动物实验研究发现γδT细胞在调节结核病患者免疫反应方面有重要保护作用,但尚缺乏临床研究加以证实,其有效性、安全性及在体内作用机制尚需进一步研究[29];(6)对于有遗传缺陷的结核分枝杆菌潜伏感染者,给予适当的免疫辅助治疗是否可以防止进展为活动性结核病,尚需进行大规模临床研究。
综上,《共识》全面归纳总结了现已应用于临床或正处于临床研究阶段的免疫制剂及其临床应用情况,并为临床医生就其临床使用适应证及禁忌证给出了指导性建议。随着医学科学研究的进一步深入,相信MTB感染的免疫机制及抗结核HDT,也就是抗结核免疫辅助治疗机制将更加清晰,为抗结核免疫制剂选择及其合理使用提供充分依据。
利益冲突 所有作者均声明不存在利益冲突
作者贡献 安慧茹:起草文章;吴雪琼:指导文章撰写工作、对文章的知识性内容作批评性审阅
参考文献
Immunology of Mycobacterium tuberculosis Infections
Transcriptional landscape of Mycobacterium tuberculosis infection in macrophages
活动性结核病患者免疫功能状态评估和免疫治疗专家共识(2021年版)
Monocyte Subsets: Phenotypes and Function in Tuberculosis Infection
Biphasic Dynamics of Macrophage Immunometabolism during Mycobacterium tuberculosis Infection
Functional and Phenotypic Changes of Natural Killer Cells in Whole Blood during Mycobacterium tuberculosis Infection and Disease
Highly focused T cell responses in latent human pulmonary Mycobacterium tuberculosis infection
Cell-mediated immune responses in tuberculosis
Initiation and regulation of T-cell responses in tuberculosis
Tuberculosis (TB) poses a great challenge to immunologists, as it represents a chronic infection characterized by persistence of the pathogen despite development of antigen-specific immune responses. Among the characteristics of adaptive immune responses to Mycobacterium tuberculosis is a delay in the onset of detectable T-cell responses, in both humans and experimental animals. Recent studies have revealed mechanisms that contribute to this delay, including pathogen inhibition of apoptosis, delayed migration of dendritic cells from the lungs to the local lymph node, and influence of regulatory T cells. In addition, novel features of M. tuberculosis antigen-specific T-cell differentiation have been discovered, which reveal pathways that limit and promote immune control of infection. Taken together, these results highlight the need for additional basic research and provide optimism for the development of TB vaccines with greater efficacy.
Classical CD4 T cells as the cornerstone of antimycobacterial immunity
T helper 2 cytokines inhibit autophagic control of intracellular Mycobacterium tuberculosis
Autophagy is a recently recognized immune effector mechanism against intracellular pathogens. The role of autophagy in innate immunity has been well established, but the extent of its regulation by the adaptive immune response is less well understood. The T helper 1 (Th1) cell cytokine IFN-gamma induces autophagy in macrophages to eliminate Mycobacterium tuberculosis. Here, we report that Th2 cytokines affect autophagy in macrophages and their ability to control intracellular M. tuberculosis. IL-4 and IL-13 abrogated autophagy and autophagy-mediated killing of intracellular mycobacteria in murine and human macrophages. Inhibition of starvation-induced autophagy by IL-4 and IL-13 was dependent on Akt signaling, whereas the inhibition of IFN-gamma-induced autophagy was Akt independent and signal transducer and activator of transcription 6 (STAT6) dependent. These findings establish a mechanism through which Th1-Th2 polarization differentially affects the immune control of intracellular pathogens.
TLR1, 2, 4, 6 and 9 Variants Associated with Tuberculosis Susceptibility: A Systematic Review and Meta-Analysis
Analysis of MIF, FCGR2A and FCGR3A gene polymorphisms with susceptibility to pulmonary tuberculosis in Moroccan population
Mycobacterium tuberculosis and the macrophage: maintaining a balance
Mycobacterium tuberculosis is a highly efficient pathogen, killing millions of infected people annually. The capacity of M. tuberculosis to survive and cause disease is strongly correlated to their ability to escape immune defense mechanisms. In particular, M. tuberculosis has the remarkable capacity to survive within the hostile environment of the macrophage. Understanding M. tuberculosis virulence strategies will not only define novel targets for drug development but will also help to uncover previously unknown signaling pathways related to the host's response to M. tuberculosis infection.
Association of Mannose-binding Lectin Polymorphisms with Tuberculosis Susceptibility among Chinese
The monogenic basis of human tuberculosis
Inherited PD-1 deficiency underlies tuberculosis and autoimmunity in a child
Role of Cathepsins in Mycobacterium tuberculosis Survival in Human Macrophages
Interplay between mycobacteria and host signalling pathways
LpqT improves mycobacteria survival in macrophages by inhibiting TLR2 mediated inflammatory cytokine expression and cell apoptosis
microRNA与结核分枝杆菌感染的致病机制研究进展
microRNA在结核分枝杆菌抗细胞自噬作用中的研究进展
Mycobacterium tuberculosis EsxH inhibits ESCRT-dependent CD4+ T-cell activation
Mycobacterium tuberculosis (Mtb) establishes a persistent infection, despite inducing antigen-specific T-cell responses. Although T cells arrive at the site of infection, they do not provide sterilizing immunity. The molecular basis of how Mtb impairs T-cell function is not clear. Mtb has been reported to block major histocompatibility complex class II (MHC-II) antigen presentation; however, no bacterial effector or host-cell target mediating this effect has been identified. We recently found that Mtb EsxH, which is secreted by the Esx-3 type VII secretion system, directly inhibits the endosomal sorting complex required for transport (ESCRT) machinery. Here, we showed that ESCRT is required for optimal antigen processing; correspondingly, overexpression and loss-of-function studies demonstrated that EsxH inhibited the ability of macrophages and dendritic cells to activate Mtb antigen-specific CD4(+) T cells. Compared with the wild-type strain, the esxH-deficient strain induced fivefold more antigen-specific CD4(+) T-cell proliferation in the mediastinal lymph nodes of mice. We also found that EsxH undermined the ability of effector CD4(+) T cells to recognize infected macrophages and clear Mtb. These results provide a molecular explanation for how Mtb impairs the adaptive immune response.
Coinhibitory Pathways in the B7-CD 28 Ligand-Receptor Family
Immune responses need to be controlled for optimal protective immunity and tolerance. Coinhibitory pathways in the B7-CD28 family provide critical inhibitory signals that regulate immune homeostasis and defense and protect tissue integrity. These coinhibitory signals limit the strength and duration of immune responses, thereby curbing immune-mediated tissue damage, regulating resolution of inflammation, and maintaining tolerance to prevent autoimmunity. Tumors and microbes that cause chronic infections can exploit these coinhibitory pathways to establish an immunosuppressive microenvironment, hindering their eradication. Advances in understanding T cell coinhibitory pathways have stimulated a new era of immunotherapy with effective drugs to treat cancer, autoimmune and infectious diseases, and transplant rejection. In this review we discuss the current knowledge of the mechanisms underlying the coinhibitory functions of pathways in the B7-CD28 family, the diverse functional consequences of these inhibitory signals on immune responses, and the overlapping and unique functions of these key immunoregulatory pathways.Copyright © 2016 Elsevier Inc. All rights reserved.
Host-mediated ubiquitination of a mycobacterial protein suppresses immunity
Current strategies in TB immunotherapy
Vitamin D-A host directed autophagy mediated therapy for tuberculosis
According to the WHO report 2019, Tuberculosis (TB) is an ancient disease of humanity that is curable. TB has caused significant morbidity and mortality even in 2018. The etiological agent of TB, Mycobacterium tuberculosis (MTB) exploits its virulence factors to escape from host immunity and therapeutic drugs. Host Directed Therapy (HDT) is an adjunctive therapy where repurposed drugs, small molecules, vitamins, cytokines, and monoclonal antibodies are used to overcome the pathogen exploited pathways in the host. One of the HDTs, i.e. induction of autophagy is a highly regulated intracellular self-degradative process in which pathogens are sequestered in double-layered autophagosomes and targeted to the lysosome for degradation. Apart from the pathogen clearance, autophagy involves the release of nutrients during starvation, removal of damaged organelles and aggregated proteins, antigen presentation, tumor suppression, and anti-aging mechanisms. Xenophagy is a type of selective autophagy against microbes induced by ubiquitin receptors (p62/SQSTM1, NDP52, NBR1, OPTN, Parkin and Smurf proteins) after pathogen recognition. ULK1/2, Beclin-1, ATG5-ATG12-ATG16 L and LC-II-PE complexes along with two nutrient-sensing protein complexes, mTOR and AMPK activate autophagy mechanisms to limit infection. Pattern Recognition Receptors (PRRs) such as TLR2, recognize lipopolysaccharide (LPS) of MTB and triggers vitamin D activating enzymes. Activated vitamin D induces the synthesis of antimicrobial peptide, LL-37, which further enhances xenophagy. Apart from vitamin D, few micronutrients such as zinc and iron also regulate autophagy. In this review, we discuss current knowledge, advances and perspectives of autophagy against TB.Copyright © 2020 Elsevier Ltd. All rights reserved.
PD-1 inhibitors for non-small cell lung cancer patients with special issues: Real-world evidence
γδT细胞在结核病免疫治疗的研究及其应用前景
京公网安备11010202007215号