Is a cure for the common cold on the way?
Published: 20th Dec 2011 12:25:49
In the northern hemisphere, cold and flu season is upon us. But the coughing, wheezing and spluttering masses that hit the streets each winter could, some scientists hope, soon be a thing of the past.
The reason for this optimistic thought is the progress being made towards the creation of a drug known as an "antiviral".
Just as antibiotics kill many different types of bacteria, antivirals could kill multiple viruses, from the ubiquitous cold and flu to the life-threatening hepatitis virus and HIV. It could even prove crucial in the case of viral epidemics like Sars and bird flu.
Existing antiviral drugs are tailored to specific diseases - HIV, hepatitis and certain types of flu for example. Vaccinations are also very virus-specific and have to be redeveloped at great cost as a virus evolves.
But Todd Rider, a research scientist at the Massachusetts Institute of Technology, is developing an antiviral drug called Draco, which has proven successful against all 15 viruses to which it has been applied in lab trials with human tissue and mice.
These include the common cold, H1N1 or swine flu, a polio virus, dengue fever and the notorious and fatal Ebola virus.
To produce it, Rider took an unusual approach, "wiring together" two natural proteins - one that detects virus entry, and another that acts as an in-built suicide switch to kill the infected cell.
"I studied both biology and engineering back in the dark ages and really wanted to combine those studies," he says.
Natural proteins in an infected cell detect the presence of a virus. These proteins are sensitive to double stranded RNA, a genetic molecule unique to and present in nearly all viruses.
Todd Rider has taken one of these natural proteins and bound it to another natural protein - also present in all cells - that triggers cell suicide.
To help the new protein penetrate a cell, he added a feature that imitates part of the HIV virus, borrowing that virus' ability to break into cells.
Once administered, the drug travels to every cell in the body but it will only activate in infected cells.
In a matter of hours, the RNA-sensing part of the drug detects the virus and activates the cell suicide part. When the host cell dies, so does the virus.
"Everyone in both departments thought I was crazy."
The dream of a broad-based antiviral drug has for years been a holy grail for microbiologists.
Recent developments in biotechnology - especially the ability of computers to analyse reams of information on DNA and the genetic make-up of viruses - has allowed for great leaps in scientific understanding of how these micro-organisms work.
This has brought a few researchers closer to the goal of a broad-based antiviral, targeting the problem in several different ways.
Last year, a break-through study at Cambridge University showed that cells have an internal system which fights and kills viruses. It was previously thought that once a virus succeeded in entering a cell, infection was inevitable.
The author of this study, Dr Leo James is now working on creating antiviral drugs that can latch on to a virus and destroy it inside the cell.
At Mount Sinai Medical School in New York, Professor Peter Palese has developed an antiviral drug that has so far proven very successful against influenza, though less so against other viruses.
And in a laboratory at the other side of the US, Dr Benhur Lee stumbled across a drug that seemed to be effective against several viruses including various pox viruses and Ebola. He soon realised it only worked against viruses that shared a distinct characteristic, a greasy outer membrane or lipid envelope.
Dr James maintains some scepticism about Rider's study.
"It is potentially very exciting but because the results are so unusual and because it was published in an unusual journal it needs to be proven by others," he says.
PLoS One, the online journal which published the paper doesn't have the peer review system used by other journals and encourages ideas that challenge established thinking.
Draco appears to have a greater range than its rivals, but it will be several years before Draco can be tested on humans. First the drug will have to go through several rounds of testing on larger mammals.
"Translating from the lab to people is really quite hard," says immunologist Hugh Pennington, Professor Emeritus at Aberdeen University.
Viruses and human cells become closely linked on infection, as a result there are many possible side-effects of a drug like this.
In the 1950s scientists thought they had come up with a similar broad-spectrum antiviral wonder drug, interferon.
In 2007 the results of a 20-year study showed that people who took vitamin C every day were no less likely to get a cold than those who didn't. Vitamin C also had no effect on the length of the illness.
Eating chicken soup to combat a cold is an age-old remedy, dating back to 12th Century physician Maimonides - and it may work. Drinking warm liquid soothes the nasal passages while the soup seems to act as an anti-inflammatory. Protein from chicken and antioxidants from vegetables also help the body make virus-killing antibodies.
An extensive study into the herb echinacea showed that people who took the supplement regularly were 65% less likely to get a cold. But later studies have discredited the herb, some claiming it increases mucus production and enhances cold symptoms.
In 2005 a study in the US showed that gargling salt and water three times a day reduced infection of the upper respiratory tract by 40% - but once someone got sick it accentuated symptoms.
The flu vaccine is the only proven medical protection against flu, though it has no effect on the common cold. Contrary to popular myth, the vaccine cannot actually give you the flu. It injects a dead form of the virus into the body.
The drug causes an infected cell to secrete a warning signal to other cells, allowing them to build up their natural defences. However it also triggers the immune system to send white blood cells to the infection, which can cause inflammation of the area, fever, aches and pains.
"Interferons are fantastic drugs," says Wendy Barclay, chair of influenza virology at Imperial College London.
"They are still used to today, to treat hepatitis C virus. But if you had a mild virus infection like a common cold you would not want to take interferon to deal with it because it would make you feel horrible, even worse than the cold was making you feel.
"The problem with using that same approach today to develop a broad-spectrum antiviral is always the worry that something in your strategy is going to trigger that same response."
Like interferon, Draco is a protein and has the potential to provoke an immune response. This could be especially problematic when the drug is administered a second time. But no immune response has been observed in mice so far.
For the average human, who suffers through a cold up to four times a year, antivirals could be the answer to days of misery - for businesses they could save weeks of lost man hours.
But for those on the front line of healthcare it could mean much more.
A broad-based antiviral could obliterate the threat of a global pandemic and mitigate health scares such as that caused by the Sars virus in 2002 or bird flu in 2009.
"No one can say when the next pandemic will occur, it may be next year or it may be in 100 years' time," says Hugh Pennington.
"We're still in the niggling worry scenario even when we are very optimistic… If we had a wonder drug like Draco might be, we could sleep much easier at night."
Find out more about Todd Rider's work and the search for a broad-based antiviral on Discovery from the BBC World Service. Listen to the programme here.
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Harvard CitationBBC News, 2011. Is a cure for the common cold on the way? [Online] (Updated 20th Dec 2011)
Available at: http://www.ukwirednews.com/news/211974/Is-a-cure-for-the-common-cold-on-the-way [Accessed 24th Apr 2014]
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