4.2. Phage Cocktails 4.2.噬菌体鸡尾酒
Most naturally occurring phages exhibit narrow host ranges in laboratory settings, which may limit their usefulness in single (monophage) therapy due to frequent mismatches between a phage and the various genotypes (strains) of the infectious bacterium. To address the limited host range, multiple phages with complementary (nonoverlapping) host ranges can be combined into a cocktail preparation. Phage cocktails can be designed to target different genotypes of the same bacterial species or to attack multiple species. Thus, by spanning a broader host range, cocktails may be more effective at maximizing killing in a bacterial infection, especially when treating uncharacterized polymorphic or polymicrobial infections.
在实验室环境中，大多数天然噬菌体的宿主范围很窄，这可能会限制它们在单一（单噬菌体）疗法中的作用，因为噬菌体与感染性细菌的不同基因型（菌株）之间经常出现不匹配。为了解决宿主范围有限的问题，可以将宿主范围互补（不重叠）的多种噬菌体组合成鸡尾酒制剂。噬菌体鸡尾酒可针对同一细菌种类的不同基因型或攻击多个种类。因此，鸡尾酒噬菌体的宿主范围更广，可以更有效地最大限度地杀死细菌感染，尤其是在治疗未定性的多态或多微生物感染时。
Phage cocktails have been the most popular and widely used strategies for phage therapy. Since the 1930s, phage cocktails have been commercially available as over-the-counter medications in many eastern European countries. These mixtures contain roughly 20–30 phages that target multiple bacterial species, and are periodically updated to ensure activity against emerging epidemiological strains. In the United States and Europe, there has been increasing use of phage cocktails in emergency and compassionate therapy cases, and within clinical trials testing phage safety and efficacy (12).
噬菌体鸡尾酒一直是噬菌体疗法中最流行、使用最广泛的策略。自 20 世纪 30 年代以来，噬菌体鸡尾酒已作为非处方药在许多东欧国家上市。这些混合物包含大约 20-30 种针对多种细菌的噬菌体，并定期更新，以确保对新出现的流行病菌株具有活性。在美国和欧洲，鸡尾酒噬菌体越来越多地用于紧急治疗和同情治疗病例，以及测试噬菌体安全性和有效性的临床试验中（12）。
Traditionally, phage cocktails have been designed mainly to broaden host range, but this might not be sufficient to meet clinical needs. A major concern in devising cocktails is to choose wisely which phages are combined, such that therapy success is not undermined by easy ability for the bacteria to evolve resistance to one phage that permits cross-resistance to others present in the cocktail. Multiple studies show that rational design of phage cocktails may help to minimize evolution of phage resistance in target bacteria (65, 66) and to increase the chances of clinical success.
传统上，噬菌体鸡尾酒的设计主要是为了扩大宿主范围，但这可能不足以满足临床需求。设计鸡尾酒的一个主要问题是明智地选择噬菌体的组合，这样就不会因为细菌容易对一种噬菌体产生抗药性而影响治疗的成功，因为这种抗药性会使噬菌体对鸡尾酒中的其他噬菌体产生交叉抗药性。多项研究表明，合理设计噬菌体鸡尾酒有助于最大限度地减少目标细菌对噬菌体产生抗药性（65、66），并增加临床成功的机会。
An approach to avoid emergence of phage-resistant bacteria is to ensure that the phages in a cocktail target different bacterial receptors. This way, phage-resistant bacteria should be selected to evolve multiple rescue mutations in genes for two (or more) receptors independently, which should occur with a lower probability. For example, if the rate of bacterial mutation to phage resistance at a single locus is 10−6 mutations per bacterium per cell division, acquiring two mutations independently would occur at a rate of 10−6 × 10−6 = 10−12 mutations per bacterium per cell division (67). However, choosing candidate phages that target different receptors requires prior characterization of said receptors, which may be laborious and time-consuming.
避免出现抗噬菌体细菌的方法是确保鸡尾酒中的噬菌体针对不同的细菌受体。这样，抗噬菌体细菌就会在两个（或更多）受体基因中独立进化出多种拯救突变，而这种突变发生的概率较低。例如，如果细菌在单个基因座上产生噬菌体抗性的突变率为每个细菌每次细胞分裂产生 10 −6 个突变，那么独立获得两个突变的发生率为 10 −6 × 10 −6 = 10 −12 。× 10 −6 = 10 −12 突变 ( 67)。然而，选择针对不同受体的候选噬菌体需要事先对所述受体进行特征描述，这可能既费力又费时。
Aside from characterizing each individual phage’s host range and receptor, developing phage mixtures also requires careful evaluation of their activity when combined as a cocktail. Niu et al. (68) demonstrated that the activity of individual phages does not necessarily predict their performance when they are mixed in a cocktail. The in vitro efficacy of some phage combinations was synergistic, whereas for others the effects were neutral or antagonistic (68). Also, as more phages are combined in a cocktail, the manufacturing process may become more time-consuming, complex, and expensive, and complex phage combinations are likely to cause pharmacokinetics and pharmacodynamics outcomes to be less predictable. Finally, the likelihood of eliciting a response from the patient’s immune system is also expected to increase with a greater number or variety of phages. To limit these shortcomings and to increase the likelihood of clinical success, phage cocktails must be rationally designed and characterized, with combinations of phages that are known to maximize the host range, act synergistically, and minimize the emergence of evolved phage-resistant bacteria.
除了确定每种噬菌体的宿主范围和受体特征外，开发噬菌体混合物还需要仔细评估它们组合成鸡尾酒时的活性。Niu 等人（68）证明，单个噬菌体的活性并不一定能预测它们混合成鸡尾酒时的表现。一些噬菌体组合的体外疗效具有协同作用，而另一些噬菌体组合的效果则是中性或拮抗的（68）。此外，随着鸡尾酒中噬菌体的增多，生产过程可能会变得更加耗时、复杂和昂贵，而复杂的噬菌体组合很可能导致药代动力学和药效学结果的可预测性降低。最后，随着噬菌体数量或种类的增加，引起患者免疫系统反应的可能性也会增加。为了限制这些缺点并增加临床成功的可能性，必须合理设计噬菌体鸡尾酒并对其进行鉴定，噬菌体的组合应能最大限度地扩大宿主范围，发挥协同作用，并最大限度地减少噬菌体抗性细菌的出现。