THE run-down hospital clinic in Tbilisi, in the Eastern European republic of Georgia, has paint peeling from the walls, and struggles to get many basic drugs that Western doctors take for granted. But the high-tech treatment given to the 70-year-old woman with two deep suppurating bedsores is not available in US or Western European hospitals.
Her doctor carefully unwraps two rectangular patches of a skin-like material, and places one on each wound. The patches are just one example of a remarkable new type of biotherapy, which could herald a revolution in the way the West treats bacterial infections. Only it’s not that new – doctors in Georgia have been using it routinely for years.
The therapy makes use of “bacteriophages”, viruses that hijack the cellular machinery of bacteria and kill them. Western doctors have known about phages for more than 100 years, but largely dismissed them while we still had a full arsenal of antibiotics. However, the rising tide of antibiotic resistance has re-ignited interest in the viruses. If scientists succeed in upgrading them with cunning molecular weaponry, phages could become the treatment of choice against a host of infectious diseases.
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Phages first came to our attention in 1896, when British chemist E. H. Hankin found that water from the River Ganges in India checked the spread of Vibrio cholerae bacteria. But boiling the river water abolished this property, suggesting it was caused by a living entity. Hankin speculated that this was why those who drank the river water were less susceptible to the cholera epidemics raging at the time.
British bacteriologist Frederick Twort identified the likely agent as a virus in 1915, and two years later Canadian microbiologist Félix d’Hérelle came to the same conclusion. He decided to use the virus, which he called a bacteriophage, on some children in a Paris hospital who were dying from dysentery. He and his co-workers swigged several pints of the test solution to check it was safe; feeling fine the next day, they gave it to the patients. The children were literally cured overnight.
As D’Hérelle found, phages are relatively easy to produce. There are millions of different kinds, occurring abundantly wherever bacteria can be found, from sewage to seawater, each making their living from a different species. Early microbiologists brewed them up by mixing some strained sewage, say, with bacteria from the lab. The next day, they would have swarms of phages active against whichever species of bacteria was used.
We now know that phages attach to bacteria’s outer surfaces and inject their own DNA. With its cellular machinery in the thrall of the phage the bacterium must follow the alien DNA’s instructions and make phage proteins, plus more DNA. These self-assemble into new phages, which burst out of the bacterium, destroying it in the process.
After his initial success, D’Hérelle continued exploring phage therapy at the Pasteur Institutes in Paris and Saigon, and later as a health officer to the League of Nations in Egypt. The fame of the new treatment spread, and soon Western drug companies such as Eli Lilly were selling phage therapies. They were taken orally, topically, used in aerosols and enemas, or injected. They were used to treat typhoid, cholera and urinary tract infections, among many others.
But in the craze for phages, quality control was haphazard. D’Hérelle once tested 20 preparations from various sources and not one contained active phages. Unsurprisingly, a major report commissioned by the American Medical Association concluded that evidence for phages’ efficacy was “contradictory”.
Then in 1928 Alexander Fleming came back from a two-week holiday to find that legendary clear spot on a dish of bacteria in his London lab. Penicillin was born and the age of antibiotics had begun. Over the next two decades, phages faded into insignificance.
But in the East, it was a different story. A Georgian microbiologist named George Eliava, who had worked with d’Hérelle in Paris, founded a research institute in Tbilisi in 1923 to continue investigating phages. Despite Eliava’s later execution as “an enemy of the people” (or a love rival with the head of the Georgian KGB, depending on the story), phage therapy flourished in the Eastern bloc for decades.
The collapse of the Soviet Union meant hard times for the Eliava Institute as it battled with power and water cuts. But it still makes a few phage therapies that are used successfully in Georgian hospitals, mostly for intestinal infections and purulent wound infections. Russia and Poland also still produce some phage therapies.
The story of phages might have ended in the crumbling healthcare systems of former Communist states, but for the alarming decline in the powers of antibiotics. Bacterial resistance to these drugs is widely seen as one of the greatest threats to health today, with doctors increasingly having to call on “last resort” antibiotics for common infections.
Could phage therapy be the answer to our prayers? It certainly has its attractions. Unlike most antibiotics, phages are “smart weapons” specific to individual bacterial species – their tail-fibre enzymes, called adhesins, will only interact with particular molecules on the surface of bacteria, unique to each species. That means they do little harm to the “good” bacteria in our guts, which antibiotics can decimate. And while antibiotic levels fall from the moment of administration, phages do the reverse, rapidly breeding into a formidable army. Yet phages are also self-limiting – once their job is done and the harmful bacteria are dead, they die away.
Phages are particularly useful for local infections with poor blood supply, such as bone infections or diabetic ulcers. Antibiotics can’t reach these sites, but because phages multiply and spread through bacterial populations they can penetrate deeply into the infected area. It is this property of phages that impressed microbiologist Elizabeth Kutter of Evergreen State College in Washington state. In 1996, she saw Eliava Institute doctors treat a diabetic patient with severe foot ulcers. Kutter recalls: “My reaction was: ‘How incredible!’ Here in the US we have no real way to treat diabetic feet.” On her return she founded the non-profit PhageBiotics Foundation in Washington, to promote research in the field.
Other pluses are that phage therapies trigger no allergies, have few side effects, and are cheap and easy to produce. Nature, after all, produces them effortlessly: there are an estimated 1032 on Earth. Indeed in Georgia, some doctors use phages almost to the exclusion of antibiotics. Zemphira Alavidze, head of the Eliava Institute’s phage biology lab, says her children have never received antibiotics in their lives. “I use only phages, because I know how effective they are, and they haven’t [any] side effects,” she says.
Yet there are sceptics in the West who think phages’ power has been exaggerated. James Bull, a molecular biologist at the University of Texas, says: “There has been so much hype that the field really needs some objective and quantitative studies to explore where it works, where it doesn’t, and why.”
Phages do have their drawbacks. Their high specificity means a patient who is gravely ill may have to wait 48 hours before their bacterial infection is identified and the correct phage can be used. A partial solution is to use cocktails of different phages against several likely bacterial culprits. For example, Piophage, the Eliava Institute’s treatment for wound infections, consists of phages that target the usual suspects, including pseudomonas, Escherichia coli, streptococci, and staphylococci.
Bacteria can develop resistance to phages, but unlike antibiotics the phages can mutate and fight back against bacterial resistance. Kutter says: “They evolve together, whereas antibiotics are static.” Using cocktails can help here too. “If any bacteria start to develop resistance to one of the phages, they’re likely to be hit by another one,” says Kutter.
But there is another, rather sinister potential problem. Some types of phages have a symbiotic relationship with bacteria rather than a parasitic one. Such phages usually integrate their DNA into that of their host, rather than taking over and killing it. And they sometimes carry genes that increase bacterial virulence, by making toxins, for example. When more than one virus infects the same bacterium, different phage species can swap genes. Suppose a patient gets a batch of phages that carries one of these harmful genes, or even genes for antibiotic resistance?
All these concerns mean that the standard phage therapies used in Georgia are unlikely to get a licence in the rest of Europe and the US in our current regulatory climate, without much further work. The future of phage therapy in the West ultimately depends on whether commercial organisations are prepared to invest in clinical trials using standardised formulations of well-characterised phages. Regulatory bodies may insist that companies sequence the genome of every phage they want to use, although this is still unknown because no firm has yet submitted a licence application.
Despite the uncertainty, several biotech firms are pressing ahead. Baltimore-based Intralytix, for example, is developing the skin-like patches described earlier in collaboration with its Georgian inventors. They comprise a slow-release biodegradable polymer impregnated with Piophage and an antibiotic. One version of the product is on sale in Georgia, and Intralytix is planning US trials when it can muster the funding. CEO John Vazzana says: “The phages are active against three different bacterial infections that are prime candidates for wound infections.”
Another emerging player in the phage game is GangaGen, based in Palo Alto, California, and Bangalore, India. The company’s name, which means “born of the Ganges”, recalls E. H. Hankin’s original discovery of the river’s bactericidal properties. The firm is developing phages that are less likely to provoke antibodies, which would hamper subsequent phage treatments. Founder Ram Ramachandran declines to give details of their techniques, as patents have yet to be granted. But he will say the firm has a library of about 400 phages – mostly isolated from hospital sewage – that are active against bacteria that commonly cause antibiotic-resistant infections in hospitals. The lead candidates for clinical trials are phages against Pseudomonas aeruginosa for burn and wound infections.
Exponential Biotherapies in Port Washington, New York State, is focusing on a different branch of the immune system – cells known as macrophages that clear particles in the phage size-range from the blood. Exponential is developing phages that last longer in the body because they are less visible to the macrophages. The technique is a simple one involving about ten rounds of “artificial selection” in mice for mutants that take longer to be eliminated (Proceedings of the National Academy of Sciences, vol 93, p 3188). The firm now has several long-lasting phages; and although it has not identified the mutation responsible in most of them, this doesn’t stop it from patenting them. The firm’s animal studies look promising, but sceptics point out that mutations that help phages avoid immune clearance in mice may not necessarily have the same effect in humans.
Exponential’s lead product is a phage against Enterococcus faecium. The firm is planning to start efficacy trials later this year in patients seriously ill with blood and skin infections caused by E. faecium that is resistant to the “last resort” antibiotic, vancomycin. Company president Richard Carlton says: “I think they’ll be extremely important – they’ll cure cases of infection that are resistant to all available antibiotics.”
Exponential’s technique was licensed from the National Institutes of Health where molecular biologist Carl Merril has been investigating phages since the 1960s. His team is trying to increase the number of bacterial species that phages can attack, making them more broadly useful. A phage’s host species is determined by the adhesin enzyme linked with its tail fibres, which recognises a specific molecular receptor on the bacterium’s outer surface. The researchers recently isolated and genotyped a highly unusual phage, which could attack two different strains of E. coli (Journal of Virology, vol 75, p 2509). It seems this phage had the genes for the two different adhesins needed and expressed them both. Merril’s team are now trying to modify other phage species to produce extra adhesins, and so extend their range of hosts.
Merril’s team has also used genetic engineering to overcome the problem of seriously ill patients having to wait 48 hours before the lab finds out the exact strain of bacteria with which they are infected. The researchers have created phages containing the gene for luciferase, the enzyme that gives off light in fireflies. If a Petri dish of such phages meet their host bacteria and start reproducing, they light up within a few hours. This technique has also been used by other researchers to allow rapid diagnosis of bacterial infections for treatment with conventional therapies.
The NIH researchers are developing multi-well plates in which each cavity contains a different phage species against bacteria likely to cause similar medical symptoms in humans. If a patient has suspected pneumonia, for example, their sputum could be added to a pneumonia plate, which would require 30 to 40 wells. Within a few hours, the cavity that lit up would identify which phage species was needed.
Will such innovations be sufficient to allow phages to become a standard treatment in the near future? Some long-standing phage researchers think that the current flurry of biotech activity could kick-start the fledgling US phage industry, and bring “big pharma” on board. Unlike our early forays into phage treatment, biotech now has the whole world of molecular biology at its fingertips, says Carl Merril. That makes it possible to figure out the right phages to use, engineer them to be more efficient and make sure they don’t carry the toxin genes.
“We can do this scientifically now,” he says. “The only questions are, do we have the will to do it, and do we have the funds to do it?”
