Phage Therapy

Abstract

Phage therapy refers to the use of bacteriophages (phages bacterial viruses) as therapeutic agents against infectious bacterial diseases. This therapeutic approach emerged in the beginning of the 20th century but was progressively replaced by the use of antibiotics in most parts of the world after the second world war. More recently however, the alarming rise of multidrug-resistant bacteria and the consequent need for antibiotic alternatives has renewed interest in phages as antimicrobial agents. Several scientific, technological and regulatory advances have supported the credibility of a second revolution in phage therapy. Nevertheless, phage therapy still faces many challenges that include: i) the need to increase phage collections from reference phage banks; ii) the development of efficient phage screening methods for the fast identification of the therapeutic phage(s); iii) the establishment of efficient phage therapy strategies to tackle infectious biofilms; iv) the validation of feasible phage production protocols that assure quality and safety of phage preparations; and (v) the guarantee of stability of phage preparations during manufacturing, storage and transport. Moreover, current maladapted regulatory structures represent a significant hurdle for potential commercialization of phage therapeutics. This article describes the past and current status of phage therapy and presents the most recent advances in this domain. History of Phage Therapy Origins of Phage Therapy In 1915, Frederick Twort, a medically trained bacteriologist from England, reported a bacteriolytic phenomenon and advanced the hypothesis that it may be due to a virus. However, excitement with the possibilities of bacteriophage can be said to have begun six months before when Félix d'Hérelle, a microbiologist at the Pasteur Institute, was sent 50 miles from the Western Front to Maisons-Laffitte to investigate an outbreak of dysentery among 10 French mounted infantrymen. Returning with samples he described a soon eponymous novel bacillus. However, in his investigations of this bacteria over the next 18 months, he found that some seemingly sterile Chamberland filtrates of it were capable of effecting the killing (lysis) of another dysentery bacillus (likely Shigella). In one of the great scientific works of the twentieth century, d'Herelle described in two short pages the experiments that he performed demonstrating that this lytic property could be serially passaged from one culture to the next by transferring 10 dilutions to new cultures fifty times. Any toxin would be too diluted after fifty passages to have a biological effect. Similarly, he showed that no dilution of these lysed cultures would produce partial growth inhibition when added over a lawn of bacteria like an antibacterial toxin would, but instead would display a number of clear glassy holes (called "plaques") equal to the concentration that would lyse a liquid culture. From these observations, d'Hérelle radically intuited that he had discovered "un microbe invisible antagoniste des bacilles dysentériques" described it as "un bactériophage obligatoire" ("an invisible microbe antagonistic to dysentery bacilli"), suggesting that his other bacteria would also be infected by these pathogens of pathogens, and (perhaps too radically) posited that these bacteriophage were the true awiki journal gent of natural immunity. [a] Centre of Biological Engineering, University of Minho, Braga, Portugal [b] Queen Astrid Military Hospital, Brussels, Belgium Centre of Biological Engineering, University of Minho, Braga, Portugal [d] G. Eliava Institute of Bacteriophages, Microbiology [e] Polish Academy of Sciences, Wrocław, Poland [f] Division of Gene Technology, KU Leuven, Heverlee, Belgium [g] Vésale Bioscience, Vésale Pharma, Noville-Sur-Mehaigne, Belgium [i] Author correspondence: jazeredo@deb.uminho.pt ORCID: [0000-0002-5180-7133] Licensed under: CC-BY-SA Received 06-08-2020; accepted 15-12-2021 WikiJournal of Medicine, 2021, 8(1):4 doi: 10.15347/wjm/2021.[004] Encyclopedic Review Article 2 of 18 | WikiJournal of Medicine Phage Therapy in the West Soon after this seminal publication, d'Hérelle and others began experimenting with the use of phage as an antimicrobial therapeutic for infections, beginning with the treatment of chicken typhoid. In 1919, d'Hérelle used phages to successfully treat four children dysentery at the "Hôpital des Enfants-Malades" in Paris. These were probably the first clinical applications of phages in humans. However, the results of his experiments were not published at that time, and so the first published use of phages to treat bacterial infections in humans was reported in 1921 by Richard Bruynoghe and Joseph Maisin. They had used phages to treat a staphylococcal infection in surgical lesions and were able to report a regression of the infections within 24 to 48 hours. The contemporary paucity of effective antimicrobial treatments and the exciting promise of these early results produced an enthusiastic ‘early period’ of phage therapy. However, sober hindsight was provided by a deeply critical and widely read report by two physicians, Eaton and Bayne-Jones, commissioned by the American Medical Association in 1934. This report demonstrated clearly that this period was largely characterized by inconsistent results, unrealistic claims, and unreliable companies. In an era lacking even a basic understanding of the nature of bacteriophages, phage preparations were marketed as treatments of implausible ailments such as gallstones, herpes, kidney stones and various cancers. Commercial preparations, even from major pharmaceutical companies, were found to be devoid of phages active against the target pathogens. Sometimes these defects were due to practical considerations, like deleterious sterilization procedures or inactivation in storage. However, some phage preparations were targeted against the wrong pathogen or were restricted to only a limited set of strains of the right pathogen. Nevertheless, even decades after the 1934 Eaton/Bayne-Jones report, phage therapy was still in sporadic use in the West into the 1950s and 1960s, and only ended in France in the 1990s. However, phages continued to be studied as tools to uncover life processes. Phages were also instrumental in the advent of genetic engineering, cancer biology and the discovery of CRISPR. Phage Therapy in the East and Central Europe Around 1934, d'Hérelle was invited by a Georgian microbiologist George Eliava to help expand a scientific institute in Tbilisi, in what is now the Republic of Georgia, for the production of both vaccines and phage preparations. This institute, now called the George Eliava Institute of Bacteriophage, Microbiology and Virology, along with others across the Soviet Union, were tasked with providing the Red Army, public health officials, and the general public with preparations that could be used to prevent and treat intestinal and purulent infections. The institute began rapidly isolating, and then industrially producing phage preparations for a variety of military and civilian purposes, with bacteriophages used as part of the standard of care for a wide variety of diseases. Although just three years later Eliava and his wife were accused of implausible crimes against the state and executed after a show trial, the institute thrived and expanded under the leadership of the primarily female scientists who both men trained. The structure of the Soviet healthcare system and the distinct intellectual framing of infectious disease by Soviet scientists provided several particular advantages in exploring phage therapy compared with the West. Indeed, the centralised control of the Soviet healthcare system allowed for the creation of comprehensive centralised banks of bacteria from infected patients from the USSR. This allowed phage scientists to maintain libraries of phages that would be active against the most current pathogens in a particularly tailored way. At the same time the way that Soviet microbiologists precociously framed bacterial infection as, in part, an ecological problem, made the ecological solution offered by phages particularly natural. Also, importantly, the ideological blinders demanded of Soviet researchers very effectively insulated phage scientists from the criticism that was dominating Western discussions about phage therapy. Moreover, antibiotics (particularly specialised antibiotics) were not available in quantities that were considered necessary for a functioning Western medical system, leading to a need for alternatives. At its peak in the 1980s, Soviet phage production reached 2 tons per week, primarily as formulated tablets against intestinal indications, for the Red Army as well as Central Asian Republics. Notably, the concept was widely considered to be conclusively demonstrated in the 60s after extensive testing, although most of the early phage therapy related scientific work was published in Russian, Georgian or Polish and thus not easily available in the West. Today, researchers from across the Former Soviet Union including the Eliava Institute publish their results and clinical experience in English, but these do not yet include RCTs (Randomized Clinical Trials) that would be considered necessary by EU and US authorities for medicines for marketing authorization. In 2012, a book was published in English that comprehensively reviews the publications on phage therapy that were found in the library of the Eliava Institute. WikiJournal of Medicine, 2021, 8(1):4 doi: 10.15347/wjm/2021.[004] Encyclopedic Review Article 3 of 18 | WikiJournal of Medicine Although the design and quality of old Soviet clinical trials and scientific publications do not conform with current international standards, they often contain valuable information that should not be neglected by current phage therapy stakeholders. One of the largest and most imaginative studies was conducted in