笹原 鉄平

Phage therapy has emerged as a promising alternative to conventional antimicrobial therapy for antimicrobial-resistant bacterial infections, but concerns about uncontrolled phage proliferation have limited its use. To address this issue, we established a nonproliferative phage-based DNA delivery system, called bacteria-targeting capsid particle (B-CAP), for the development of antimicrobial agents which effectively prevented phage spread while maintaining bactericidal activity. B-CAP is principally a T7 phage capsids packaged with a partial T7 phage genome, giving it the allowance to accommodate large foreign DNA up to 18 kb in length. We confirmed the efficacy of B-CAP in targeting and injecting its genome into bacteria, analogous to the wild-type phage. To demonstrate proof-of-concept and potential for developing an antimicrobial agent, we loaded colicin E1 operon onto the B-CAP system, resulting in the construction of B-CAP_ColE1, an antimicrobial agent capable of boosting colicin E1-based bacterial killing against Escherichia coli. Although no therapeutic effect was observed for B-CAP, B-CAP_ColE1 exhibited strong bactericidal activity against carbapenem-resistant E. coli both in vitro and in vivo, and significantly improved the survival of mice in an infection mouse model experiment. Finally, B-CAP_ColE1 is biologically contained or inert, reducing potential biological hazards during therapeutic use. Our results demonstrate that the B-CAP system offers a new strategy for developing nonreplicative phage-based antimicrobial agents against bacterial infections.

Leishmaniasis is caused by an obligate intracellular protozoa of the genus Leishmania. Its clinical manifestations include cutaneous, mucocutaneous, and visceral forms. Sporotrichoid cutaneous leishmaniasis (SCL) is an atypical and rare form of cutaneous leishmaniasis (CL) reported mainly in the Old World. This case report describes SCL in a Japanese man infected with Leishmania (Viannia) peruviana in Peru. His lesions occurred on both feet, with the left foot lesion being a simple CL that resolved spontaneously. However, the lesion on the right foot did not cure by itself; instead, it progressed centrally along the lymph nodes, eventually forming an SCL. Amastigotes were detected in both feet and genetically identified as L. (V.) peruviana. The lesions gradually resolved after treatment with intravenous liposomal amphotericin B. Here, we report the first case of SCL caused by L. (V.) peruviana.

In response to the escalating antibiotic resistance in multidrug-resistant pathogens, we propose an innovative phagemid-based capsid system to generate CRISPR-Cas13a-loaded antibacterial capsids (AB-capsids) for targeted therapy against multidrug-resistant Staphylococcus aureus. Our optimized phagemid system maximizes AB-capsid yield and purity, showing a positive correlation with phagemid copy number. Notably, an 8.65-fold increase in copy number results in a 2.54-fold rise in AB-capsid generation. Phagemids carrying terL-terS-rinA-rinB (prophage-encoded packaging site genes) consistently exhibit high packaging efficiency, and the generation of AB-capsids using lysogenized hosts with terL-terS deletion resulted in comparatively lower level of wild-type phage contamination, with minimal compromise on AB-capsid yield. These generated AB-capsids selectively eliminate S. aureus strains carrying the target gene while sparing non-target strains. In conclusion, our phagemid-based capsid system stands as a promising avenue for developing sequence-specific bactericidal agents, offering a streamlined approach to combat antibiotic-resistant pathogens within the constraints of efficient production and targeted efficacy.

Phage therapy, the use of bacteriophages (phages) to treat bacterial infections, is regaining momentum as a promising weapon against the rising threat of multidrug-resistant (MDR) bacteria. This comprehensive review explores the historical context, the modern resurgence of phage therapy, and phage-facilitated advancements in medical and technological fields. It details the mechanisms of action and applications of phages in treating MDR bacterial infections, particularly those associated with biofilms and intracellular pathogens. The review further highlights innovative uses of phages in vaccine development, cancer therapy, and as gene delivery vectors. Despite its targeted and efficient approach, phage therapy faces challenges related to phage stability, immune response, and regulatory approval. By examining these areas in detail, this review underscores the immense potential and remaining hurdles in integrating phage-based therapies into modern medical practices.