Biotechnological challenges of phage therapy

The challenges for successful launching of a profitable phage therapeutic product include intellectual property rights, safety issues, reproducibility, stability and robustness of the product. A successful and marketable product would be a highly purified bacteriophage preparation containing one or several fully characterized phages, accompanied by optimized methods of administration and backed up by properly controlled efficacy and safety studies.     

History of phage research as viewed by a European

Abstract: The history of phage research as the origin of molecular biology is related as seen by a scientist located at that critical time in Geneva. The preponderant influence of Max Delbrück on these developments is traced as a consequence of his personal charisma. Jean Weigle, former professor of experimental physics in Geneva and later research fellow with Delbrück, acted as an important ambassador to the European groups.     

The regulatory region of phage fr replicase cistron. III. Initiation activity of specific fr RNA fragments.

RNA fragments from phage fr covering the complete or part of the replicase cistron initiation region have been used as templates in the formation of a ribosomal initiation complex in vitro. The results so obtained together with our earlier findings in a similar approach applied to fragments of the structurally related RNA from phage MS2 have allowed us to pinpoint the boundaries of the replicase cistron initiation region on phage RNA. A structural model of the above initiation region has been provided which shows that besides the minimal initiation region (comprises the Shine-Dalgarno sequence and initiator AUG), the flanking regions are also involved and are responsible for additional interactions with the ribosome. The flanking regions possibly contribute to the stability of specific contact between the ribosome and template realized by the minimal initiation region.     

Population and evolutionary dynamics of phage therapy

Following a sixty-year hiatus in western medicine, bacteriophages (phages) are again being advocated for treating and preventing bacterial infections. Are attempts to use phages for clinical and environmental applications more likely to succeed now than in the past? Will phage therapy and prophylaxis suffer the same fates as antibiotics--treatment failure due to acquired resistance and ever-increasing frequencies of resistant pathogens? Here, the population and evolutionary dynamics of bacterial-phage interactions that are relevant to phage therapy and prophylaxis are reviewed and illustrated with computer simulations.     

Evidence for an early regulatory function in phage P22

Summary A temperature sensitive mutant of P22 phage (ts X) was isolated and studied.This mutant seems to have a basic regulatory function: it is defective in an early function like the typical DNA^- mutant ts 12.1; it is unable to direct the phage DNA synthesis and does not lyse infected or induced cells.Unlike ts 12.1, the mutation ts X seems to involve a gene product necessary for the expression of any vegetative function, since no phage protein synthesis, no alteration of host DNA synthesis, and no cell killing can be observed under non-permissive conditions.The possible functional similarity between the N-cistron of the phage and the present X-cistron in P22 is discussed.     

Characterization of the Pseudomonas aeruginosa transposable phage D3112 [corrected] left-end regulatory region.

The nucleotide sequence (2682 bp) of the left end of the Mu-like transposable bacteriophage D3112 cts15 from Pseudomonas aeruginosa was determined. A 720 bp open reading frame (ORF) is located on the bottom strand (positions 892-173), potentially encoding a polypeptide of 240 residues (Mr = 26,329). Specific binding of Escherichia coli Integration Host Factor (IHF) to a site located 907-922 bp from the D3112 left end suggests the existence of a P. aeruginosa IHF and its role, as in Mu, in the regulation of phage development.     

Optimal bacteriophage mutation rates for phage therapy

The mutability of bacteriophages offers a particular advantage in the treatment of bacterial infections not afforded by other antimicrobial therapies. When phage-resistant bacteria emerge, mutation may generate phage capable of exploiting and thus limiting population expansion among these emergent types. However, while mutation potentially generates beneficial variants, it also contributes to a genetic load of deleterious mutations. Here, we model the influence of varying phage mutation rate on the efficacy of phage therapy. All else being equal, phage types with historical mutation rates of approximately 0.1 deleterious mutations per genome per generation offer a reasonable balance between beneficial mutational diversity and deleterious mutational load. We determine that increasing phage inoculum density can undesirably increase the peak density of a mutant bacterial class by limiting the in situ production of mutant phage variants. For phage populations with minimal genetic load, engineering mutation rate increases beyond the mutation-selection balance optimum may provide even greater protection against emergent bacterial types, but only with very weak selective coefficients for de novo deleterious mutations (below approximately 0.01). Increases to the mutation rate beyond the optimal value at mutation-selection balance may therefore prove generally undesirable.     

噬菌体抗菌治疗安全性评估体系的建立

人类已经进入后抗生素时代,噬菌体治疗近年来重新备受重视,噬菌体制剂不同于传统抗菌药物,已有对传统抗菌药物的安全性评估体系不适合用于对噬菌体治疗制剂的评估,需要建立对噬菌体治疗安全性评估的体系。本文就噬菌体治疗所涉及的安全性问题进行系统分析研究,通过噬菌体本身的选择、噬菌体制剂制备、制剂形式、制剂给予途径、剂量和频次等,以及噬菌体治疗细菌感染性疾病患者选择等所涉及的安全性和噬菌体治疗对周围微环境的影响等进行全面分析。建立噬菌体治疗安全性评估体系,为噬菌体治疗尽早进入临床奠定基础。     

Virus, phage, transposon and their regulatory small non-coding RNAs

Many reports have been accumulated describing not a few microRNAs (miRNAs) in eukaryotes target viral genomes, whereas a number of viruses also encode miRNA genes. These small RNAs play important roles on viral infection and their replication. In germ cells, another small RNA, piRNA is reported to repress endogenous transposons. Furthermore, CRISPR RNA target virus/phage genomes in both archaea and bacteria. Therefore, small RNA is deeply involved in a broad range of biological defense systems. This system may be applied not only to control replication of viruses or phages but also provide implication on regulating the growth of microorganisms including pathogenic bacteria.     

噬菌体疗法在疾病中的应用进展

随着耐药菌在世界范围内不断传播,应用噬菌体作为有效的抗生素替代疗法重新受到研究者的关注。另一方面,人体微生物群与宿主健康的相互作用研究不断深入,靶向调控微生物群来影响人体健康成为多项研究的关注焦点,利用噬菌体靶向降低与疾病发展正相关的特征性细菌的丰度,成为肿瘤、酒精性肝病及糖尿病等非感染性疾病更精准的预防或辅助治疗策略。本文对噬菌体疗法在感染性和非感染性疾病中的应用进展进行了综述。     

Overcoming the phage replication threshold: a mathematical model with implications for phage therapy

Prior observations of phage-host systems in vitro have led to the conclusion that susceptible host cell populations must reach a critical density before phage replication can occur. Such a replication threshold density would have broad implications for the therapeutic use of phage. In this report, we demonstrate experimentally that no such replication threshold exists and explain the previous data used to support the existence of the threshold in terms of a classical model of the kinetics of colloidal particle interactions in solution. This result leads us to conclude that the frequently used measure of multiplicity of infection (MOI), computed as the ratio of the number of phage to the number of cells, is generally inappropriate for situations in which cell concentrations are less than 10(7)/ml. In its place, we propose an alternative measure, MOI(actual), that takes into account the cell concentration and adsorption time. Properties of this function are elucidated that explain the demonstrated usefulness of MOI at high cell densities, as well as some unexpected consequences at low concentrations. In addition, the concept of MOI(actual) allows us to write simple formulas for computing practical quantities, such as the number of phage sufficient to infect 99.99% of host cells at arbitrary concentrations.