Does CRISPR-Cas immunity limit the effectiveness of phage therapy?

在全球范围内，对所有主要类别的化疗抗生素的耐药性不断上升，重新引起了人们对利用噬菌体治疗细菌感染的兴趣。与抗生素治疗一样，细菌对噬菌体治疗的耐药性的出现也可能限制基于噬菌体的治疗方法的长期可持续性。我们目前缺乏对细菌如何进化抵抗多种噬菌体组合的机制理解，限制了我们设计限制耐药性的噬菌体组合的能力。重要的是，细菌具有多种不同的机制来防御噬菌体感染，包括表面受体修饰（SRM）和CRISPR-Cas。这些不同的机制在不同的条件下受到青睐，这些条件可能在感染部位有所不同，但CRISPR-Cas对噬菌体治疗耐药性进化的重要性尚不清楚。我们将使用实验室进化实验来确定CRISPR-Cas免疫如何在感染相关的环境条件下影响多噬菌体抗性的进化，预测这些环境条件将打破从SRM到CRISPR-Cas免疫的平衡。然后，我们将使用小鼠急性呼吸道感染模型，通过增强多噬菌体耐药性进化，测试CRISPR-Cas免疫是否会降低体内噬菌体治疗的疗效。这些实验将开发和测试一个进化框架，以了解CRISPR-Cas如何影响多噬菌体耐药性进化和噬菌体治疗的功效。

Globally rising rates of resistance against all major classes of chemotherapeutic antibiotics has renewed interest in the therapeutic use of phages to treat bacterial infections. As with antibiotic treatments, the emergence of bacterial resistance against phage treatments could also limit the long-term sustainability of phage-based therapeutics. We currently lack a mechanistic understanding of how bacteria evolve resistance against combinations of multiple phages, limiting our ability to design phage combinations that limit resistance. Importantly, bacteria possess multiple distinct mechanisms to defend against phage infection, including surface receptor modification (SRM) and CRISPR-Cas. These distinct mechanisms are favoured under different conditions which are likely to vary at the site of infection, but the importance of CRISPR-Cas for the evolution of resistance against phage therapy is unknown. We will use laboratory evolution experiments to determine how CRISPR-Cas immunity affects the evolution of multi-phage resistance across infection-relevant environmental conditions predicted to tip the balance from SRM to CRISPR-Cas immunity. We will then test if, by enhancing multi-phage resistance evolution, CRISPR-Cas immunity reduces the efficacy of phage therapy in vivo using a mouse model of acute respiratory infection. These experiments will develop and test an evolutionary framework for understanding how CRISPR-Cas affects multi-phage resistance evolution and the efficacy of phage therapy.