Past and Future of Phage Therapy and Phage-Derived Proteins in Patients with Bone and Joint Infection

Abstract

Phage-derived therapies comprise phage therapy and the use of phage-derived proteins as anti-bacterial therapy. Bacteriophages are natural viruses that target specific bacteria. They were proposed to be used to treat bacterial infections in the 1920s, before the discovery and widespread over-commercialized use of antibiotics. Phage therapy was totally abandoned in Western countries, whereas it is still used in Poland, Georgia and Russia. We review here the history of phage therapy by focusing on bone and joint infection, and on the development of phage therapy in France in this indication. We discuss the rationale of its use in bacterial infection and show the feasibility of phage therapy in the 2020s, based on several patients with complex bone and joint infection who recently received phages as compassionate therapy. Although the status of phage therapy remains to be clarified by health care authorities, obtaining pharmaceutical-grade therapeutic phages (i.e., following good manufacturing practice guidelines or being "GMP-like") targeting bacterial species of concern is essential. Moreover, multidisciplinary clinical expertise has to determine what could be the relevant indications to perform clinical trials. Finally "phage therapy 2.0" has to integrate the following steps: (i) follow the status of phage therapy, that is not settled and defined; (ii) develop in each country a close relationship with the national health care authority; (iii) develop industrial-academic partnerships; (iv) create academic reference centers; (v) identify relevant clinical indications; (vi) use GMP/GMP-like phages with guaranteed quality bioproduction; (vii) start as salvage therapy; (vii) combine with antibiotics and adequate surgery; and (viii) perform clinical trials, to finally (ix) demonstrate in which clinical settings phage therapy provides benefit. Phage-derived proteins such as peptidoglycan hydrolases, polysaccharide depolymerases or lysins are enzymes that also have anti-biofilm activity. In contrast to phages, their development has to follow the classical process of medicinal products. Phage therapy and phage-derived products also have a huge potential to treat biofilm-associated bacterial diseases, and this is of crucial importance in the worldwide spread of antimicrobial resistance.

Keywords: ANSM drug-safety agency; bacteriophages; bone and joint infection; compassionate use; lysin; osteoarticular infection; osteomyelitis; phage therapy; phage-derived enzyme; prosthetic joint infection.

Figure 1

The two phage cycles: lysogenic, not causing bacterial lysis but inducing genetic remodeling and possible acquisition of genes heightening pathogenicity; and lytic, leading to self-maintained bacterial lysis, with production of lysin that disrupts the bacterial cell wall and facilitates phage dissemination; Purple: Bacteria; Green: Bacteriophage; Red: Phage DNA; Yellow: Lysin.

Figure 2

In the 1930–1940s, “ready-made” phage cocktails dedicated to specific clinical syndromes were produced and marketed by the Bacteriophage Laboratory (a). As these “ready-made” cocktails were considered not fully and constantly active, personalized phage therapy based on demonstrating the activity of the phage on the patient’s strain was developed to treat the American Western actor Tom Mix, who was cured during the movie Destry Rides Again (1932) that came out 1 year after he received abdominal phage therapy injection for life-threatening peritonitis (b). In the 1970s, Pr. Bertoye’s team (c) at the Infectious Diseases Clinic of the Lyon Croix-Rousse Hospital (d) identified patients in clinical failure for treatment, in partnership with the Lyon Institut Pasteur. Potentially active phages were selected and trained before use. This “personalized medicine” was used to treat 70 patients a year. Original pictures c and d are the property of T. Ferry, and have already been published in the journal Virologie (John Libbey Eurotext).

Figure 3

“Ready-made” cocktails currently produced in Eastern European countries: the Pyo-bacteriophage cocktail of the Eliava institute, Georgia (a) containing various titers of phages targeting Staphylococcus spp., Streptococcus spp., E. coli, Pseudomonas aeruginosa and Proteus spp.; and a bacteriophage targeting Staphylococcus spp. (b) produced in Russia by the company Microgen.

Figure 4

Phagogram and phage preparation techniques. PFUs visualized by spot test using solid medium and optic microscopy (a): For the lowest phage suspension dilutions (pure, and 10-1 to 10-3 dilutions: first lines), PFUs are confluent and uncountable. Further dilution allows some PFUs to be counted (4th and 5th lines), and the number of PFUs in the solution to be deduced. The killing assay studies temporal progression of DO600nm in liquid medium (b), monitoring bacterial multiplication with and without phages, indicating susceptibility/resistance: bacterial multiplication without phages (blue line with square); inactive phage (red line with square); active phage with slight delayed inhibition of the bacterial growth (turquoise line with cross); active phage, but with delayed bacterial growth (purple line with cross); fully active bacteriophage totally inhibiting bacterial growth (green line with triangle). Preparation in a Lyon hospital pharmacy of an extemporaneous phage solution in sterile conditions at time of surgery (c).

Figure 5

Post-traumatic left tibial chronic osteomyelitis in a French patient in failure of phage treatment administered in Georgia. A ready-made cocktail was administered locally and per os for several weeks. Bone exposure persisted (a) with large skin adherences (b) to underlying sclerotic bone (c) X-ray without any abscess or intramedullary cavity on CT-scan (d); transverse view of both legs; on the left the leg without infection, on the right the infected leg, with sclerotic bone and densification of the medulla). Heavy high-tech surgery in a CRIOAc reference center is preferably indicated, with bone curettage (only means of eradicating infected necrotic bone), resection of the large skin area around the exposed bone, related to chronic inflammation and unable to recover, with free-flap cover followed by prolonged antimicrobial therapy. Intraoperative and postoperative phage administration is clearly not feasible in such a patient.

Figure 6

The whole process required for phage therapy: phage discovery; phage banking (that has to be implemented and maintained) with various phages targeting different bacteria; relevant clinical indication; phage therapy using a fixed cocktail, with a certain likelihood that some of the phages will not be not active; phage selection based on the phagogram (currently performed in France), with cocktail preparation and administration in hospital (green option); phage selection based on the phagogram, with phage training on the patient’s strain, which is not currently performed and is more time consuming than the previous options.