How researchers are using the human immune system to lead fight against viruses
Antibiotics, anaesthetics, simple sanitation. If asked to name the greatest medical breakthroughs of all time, these would figure in anyone’s list.
But there is one that just keeps on getting better: vaccination.
It’s already famed for protecting us against a host of killer diseases, from polio to measles.
Mass vaccination also achieved an astonishing first in 1980 – the elimination of smallpox, a global scourge.
But as scientists will hear at a global conference in Dubai this month, vaccination is driving a fresh wave of triumphs against mass killers, including malaria and even cancer.
Perhaps most astonishing of all is that all this is being made possible by compounds created by just one small pharmaceutical laboratory: our own bodies.
Each year, the pharmaceutical industry spends tens of billions of dollars searching for blockbuster drugs. But it has yet to find any miracle cure as versatile and effective as our disease-fighting immune system.
The product of aeons of evolution, the immune system is a reservoir of complexity, able to defeat illnesses that science has yet to find a cure for – from the common cold to ebola.
Yet evolution cannot be relied on to provide panaceas. Its twin driving forces of random mutation and natural selection are focused on one goal: boosting the chances of organisms living long enough to reproduce.
Fortunately, evolution has given us an immune system with a host of strategies for defeating diseases. And the most impressive of these is the ability to learn from experience.
Credit for discovering this is often given to the 18th-century English physician, Edward Jenner. The reality is more intriguing.
Stories of how smallpox survivors remained untouched by later outbreaks had been noted by physicians for centuries before Jenner. By 1000AD, Chinese physicians were trying to infect healthy patients with weak doses of smallpox to induce protection against the full-blown disease.
But inoculation left little margin for error, and all too often the dose triggered the disease, with lethal results. Not until the 1750s was the solution identified, when researchers investigated folklore claiming it was possible to avoid smallpox by exposure to cowpox, a non-lethal disease contracted from cattle.
Jenner was neither the first to take the claim seriously, nor to carry out human tests. He deserves credit, however, for his determination to have vaccination taken seriously by a deeply sceptical medical community.
By 1801, more than 100,000 people had been vaccinated against smallpox and thus protected from a scourge that killed thousands each year.
Ever since, researchers have sought to mimic this success with other diseases. Today, many viral diseases are no longer the threat that they used to be.
Progress is being made in finding vaccines capable of persuading the immune system to take on ever more complex adversaries. One prime target is the parasite responsible for malaria, which kills about a million people each year.
After decades of success using antimalarial drugs, the parasite is now becoming more resistant, which threatens to undo all the progress made to date. Although far more complex than a virus, the parasite also offers far more potential triggers for an immune response.
More than 20 candidate vaccines are in development and the first might make its debut this year. Code-named RTS,S and developed by GlaxoSmithKline, it uses fragments of proteins from the parasite to provoke the creation of antibodies, but without causing the disease.
In recent trials, about half of those given the vaccine have benefited. Although impressive, this suggests that something more is needed. Last month, researchers in Australia said they might have found at least part of the answer.
According to Prof James Beeson and his colleagues at the Burnet Institute, Melbourne, the trick lies in triggering not just antibodies but also the release of a complex of proteins in the bloodstream called complement. This double whammy appears to be effective at preventing the infection of red blood cells, which causes the disease.
Meanwhile, vaccines against a range of killer bacteria are also making progress.
Drugs maker Pfizer has just won approval for the wider use of Prevnar, which protects against bacteria that cause death from pneumonia among the elderly. This follows the publication last month of a major study of more than 80,000 patients, which showed that the vaccine cuts the risk of such infections by almost half.
But most excitement surrounds the potential of vaccines against cancer. The discovery that some forms of the disease, such as cervical cancer, are infectious has already led to mass vaccination campaigns against the viruses responsible.
Not surprisingly, progress to date has been slow. But last month, a team in the United States announced tentative success with a vaccine that may work with many cancers.
According to the researchers at the Memorial Sloan Kettering Cancer Centre, the vaccine exploits the fact that a protein, code-named WT1, appears in many forms of cancer cells.
By giving patients a vaccine containing disease-fighting cells trained to recognise WT1, the hope is that the cells will target the cancer, while leaving healthy cells untouched.
Safety trials have proved encouraging, and last month it was reported that about half of 15 patients with terminal leukaemia treated in the past three years are still alive.
This could yet prove to be another false dawn. Yet if the history of vaccination is any guide, we should be wary of dismissing the abilities of the miraculous lab within us all.
Robert Matthews is Visiting Reader in Science at Aston University, Birmingham
Updated: April 5, 2015 04:00 AM