Is a cure for the common cold on the way?
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. They 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.
The microscope images above show that DRACO successfully treats viral infections. In the left set of four photos, rhinovirus (the common cold virus) kills untreated human cells (lower left), whereas DRACO has no toxicity in uninfected cells (upper right) and cures an infected cell population (lower right). Similarly, in the right set of four photos, dengue hemorrhagic fever virus kills untreated monkey cells (lower left), whereas DRACO has no toxicity in uninfected cells (upper right) and cures an infected cell population (lower right). (Credit: Todd H. Rider et al)To produce it, Mr Rider took an unusual approach, “wiring together” two natural proteins - one that detects virus entry, and another that acts as a suicide switch that kills the infected cell.
“I studied both biology and engineering back in the dark ages and really wanted to combine those studies,” he says.
“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 breakthrough 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.
Dr Leo James, the author of this study, 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 Mr 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 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.