4.3. Phages and Autoimmune Diseases of the Nervous System
4.3.噬菌体与神经系统自身免疫疾病
Recent data from our and other groups suggest that phages possess immunomodulating activities that may have the potential to control aberrant immune responses, including autoimmune reactions [15,183]. Autoimmune disorders of the nervous system (e.g., inflammatory demyelinating diseases, myasthenia gravis, etc.) pose a significant medical challenge as their treatment is not always satisfactory while side effects of currently available therapy may be serious and sometimes life-threatening [184,185]. Therefore, in those clinical settings one could envisage the potential therapeutic action of selected phages with proven anti-inflammatory and immunosuppressive activity and a virtual lack of side effects [186].
我们和其他研究小组的最新数据表明，噬菌体具有免疫调节活性，有可能控制异常免疫反应，包括自身免疫反应[ 15, 183]。神经系统的自身免疫性疾病（如炎症性脱髓鞘疾病、重症肌无力等）是一项重大的医学挑战，因为其治疗效果并不总是令人满意，而现有疗法的副作用可能很严重，有时甚至危及生命[ 184, 185]。因此，在这些临床环境中，我们可以考虑使用经证实具有抗炎和免疫抑制活性且几乎没有副作用的特定噬菌体进行潜在治疗[ 186]。
5. Potential of Phage Application in Targeted Therapy for Brain Cancers
5.噬菌体在脑癌靶向治疗中的应用潜力
Glioblastoma—the most abundant and highly aggressive primary brain tumor in adults—is characterized with a rising incidence rate, currently ranging from 0.59 to 5 per 100,000 persons internationally [187], with a median life expectancy of approximately 14–16 months [188], and only 5% of all patients surviving to 5 years post diagnosis [189]. In terms of risk factors, glioblastoma is poorly understood. Due to the low frequency of the tumor worldwide, it was suggested that the brain demonstrates a higher degree of protection from genotoxic stress than other organs [190]. Because brain cells are protected from mutagens by the BBB, it was postulated that brain tumors, especially glioblastoma, arise from a small pool of adult neuronal stem and progenitor cells (NSPC), which are located in the subventricular zone, subcortical white matter, but also in the dentate gyrus of the hippocampus [191,192,193]. These cells retain the ability to enter mitosis and play a crucial role in learning and memory [194]. Of all these cells, glioma-initiating cells or glioma stem-like cells are the most important; they can self-renew, differentiate, and form secondary tumors in xenotransplantation [195]. The progeny of glioma-initiating cells mostly resembles astrocytes, but some cells were also noted to have features of endothelial cells or pericytes [196,197,198]. In most cases of glioblastoma, tumors are located in the frontal, temporal, and parietal lobes, and rarely in the occipital-lobe, cerebellar, brainstem, and spinal cord [189]. The current standard of care involves surgery, followed by radiotherapy in combination with chemotherapy [195]). In recent years, molecular targeted therapy was suggested as an alternative treatment option in glioblastoma, and this topic was comprehensively reviewed by Le Rhun et al. (2019). Possible targets are molecules involved in oncogenic signaling via tyrosine receptor kinases, cell cycle control, and susceptibility to apoptosis. Repurposing of drugs conventionally used in other diseases, e.g., metformin or the anti-epileptic drug valproic acid, is also considered.
胶质母细胞瘤是成人中发病率最高、侵袭性最强的原发性脑肿瘤，其发病率呈上升趋势，目前国际发病率为每 10 万人中有 0.59 到 5 例[187]，中位预期寿命约为 14-16 个月[188]，只有 5%的患者能在确诊后存活 5 年[189]。人们对胶质母细胞瘤的风险因素了解甚少。由于胶质母细胞瘤在全球的发病率较低，有人认为大脑比其他器官对基因毒性应激的保护程度更高[190]。由于脑细胞受到 BBB 的保护而不受突变物的影响，有人推测脑肿瘤，尤其是胶质母细胞瘤，来源于一小部分成年神经元干细胞和祖细胞（NSPC），这些细胞位于室管膜下区、皮质下白质以及海马齿状回[191, 192, 193]。这些细胞保持着有丝分裂的能力，在学习和记忆中发挥着至关重要的作用[194]。在所有这些细胞中，胶质瘤启动细胞或胶质瘤干样细胞最为重要；它们可以自我更新、分化，并在异种移植中形成继发性肿瘤[195]。胶质瘤始发细胞的后代大多类似星形胶质细胞，但也有一些细胞具有内皮细胞或周细胞的特征[196, 197, 198]。在大多数胶质母细胞瘤病例中，肿瘤位于额叶、颞叶和顶叶，很少位于枕叶、小脑、脑干和脊髓[189]。目前的标准治疗方法包括手术，然后结合化疗进行放疗[195]）。近年来，分子靶向疗法被认为是胶质母细胞瘤的另一种治疗选择，Le Rhun 等人（2019 年）对这一主题进行了全面综述。可能的靶点包括通过酪氨酸受体激酶参与致癌信号转导的分子、细胞周期控制以及对细胞凋亡的敏感性。此外，还考虑对用于其他疾病的常规药物（如二甲双胍或抗癫痫药物丙戊酸）进行再利用。
Even though many different drugs that potentially target glioblastoma have been investigated, none of them have entered clinical practice, possibly because most glioblastomas are far from a single-pathway driven disease [195]. As reported, glioma stem-like cells are resistant to radiotherapy and chemotherapy for yet undefined reasons [199,200,201,202,203,204,205]. Especially in the case of brain tumors, the therapeutic effect is difficult to achieve because of the presence of the BBB, which impedes the penetration of drug particles. Moreover, the glioma stem cells (GSCs) turned out to be capable of self-renewal and resistant to standard treatment [202]. This provides an unmet need to create innovative solutions that would allow difficulties in the delivery, pharmacokinetics, and therapeutic use of currently available drugs to be overcome, but also the development of new vectors and novel methods of administration, diagnosis, and monitoring of treatment responses. Bacteriophages may have the potential to meet these conditions.
尽管针对胶质母细胞瘤的多种药物已被研究，但没有一种药物进入临床实践，这可能是因为大多数胶质母细胞瘤远非单一途径驱动的疾病[195]。据报道，胶质瘤干样细胞对放疗和化疗有抵抗力，原因尚不明确[199, 200, 201, 202, 203, 204, 205]。特别是在脑肿瘤的情况下，由于存在BBB，阻碍了药物颗粒的渗透，因此很难达到治疗效果。此外，胶质瘤干细胞（GSCs）具有自我更新能力，对标准治疗具有抗药性[202]。这就提出了一个尚未满足的需求，即创造创新解决方案，克服现有药物在给药、药代动力学和治疗使用方面的困难，同时开发新的载体和新的给药、诊断和治疗反应监测方法。噬菌体有可能满足这些条件。
Filamentous, rod-shaped phages such as f1, fd, and most importantly M13 are widely used in a variety of biochemical and biomedical applications. Recent studies suggest that these phages can greatly impact the development of new therapeutic strategies due to their ability to self-assemble into nanoscale structures [203]. Moreover, rod-shaped nanoparticles possess higher selectivity and specificity as well as targeting abilities to endothelial cells and brain endothelium compared to their spherical counterparts [204]. Filamentous capsids are also robust and monodisperse [205,206]. However, the greatest advantage of these phages comes from their genetic flexibility and easy-to-manipulate structure [206]. One recent breakthrough was the use of bacteriophage nanoparticles in neuronal regeneration and the specific development of biomimetic scaffolds for tissue engineering purposes. Therefore, they may have enormous potential in creating bioactive constructs as a scaffold for repairing and regenerating injured tissues in the nervous system.
丝状、杆状噬菌体（如 f1、fd 以及最重要的 M13）被广泛应用于各种生化和生物医学领域。最近的研究表明，由于这些噬菌体能自我组装成纳米级结构，因此能极大地影响新治疗策略的开发[ 203]。此外，与球形纳米粒子相比，杆状纳米粒子具有更高的选择性和特异性，以及对内皮细胞和脑内皮细胞的靶向能力[204]。丝状囊壳也具有坚固性和单分散性 [ 205, 206]。不过，这些噬菌体的最大优势来自其遗传灵活性和易于操纵的结构[206]。最近的一项突破是将噬菌体纳米颗粒用于神经元再生和组织工程生物仿生支架的特定开发。因此，噬菌体纳米颗粒在创建生物活性构建物作为修复和再生神经系统损伤组织的支架方面具有巨大潜力。
The phage display method was developed in order to obtain recombinant, exogenous peptides or proteins exposed on the surface of phage virions [207]. This allows for the preparation of a diverse library of phages presenting peptides/proteins that can be screened to select clones with the highest affinity to the target molecule. Nowadays, phage display technology is commonly used for drug development because it allows for an easy and effective screening of large pools of peptides or antibody variable domains. The development of the method paved the way for a wider use of bacteriophages in nanotechnology and biomedical studies [208]. The phage display technique is a promising tool that may be useful in the treatment of glioma. Targeted therapy, cytotoxic effect, and neuroimaging is achievable [209].
噬菌体展示法的开发是为了获得暴露在噬菌体病毒表面的重组外源肽或蛋白质[ 207]。这样就可以制备出多种呈现多肽/蛋白质的噬菌体库，通过筛选，选出与目标分子亲和力最强的克隆。如今，噬菌体展示技术已被普遍用于药物开发，因为它可以方便有效地筛选大量肽或抗体可变域。该方法的开发为噬菌体在纳米技术和生物医学研究中的广泛应用铺平了道路[ 208]。噬菌体展示技术是一种很有前途的工具，可用于治疗胶质瘤。可以实现靶向治疗、细胞毒性效应和神经成像[ 209]。