o The Frog Blog: Irish Times BANG - A Cure For The Common Cold

Wednesday, 15 December 2010

Irish Times BANG - A Cure For The Common Cold


We’ve all been there: runny nose; aching muscles; sore throat; a nasty cough; shivering; severe headache; violent sneezing; fever – all the typical symptoms of the “common cold”. But how come, in this the age of modern medicine, no one has come up with a cure for this nasty little infection?

On average, every Irish adult gets infected by cold-causing organisms twice a year and every Irish child is infected an astonishing six times a year, making the cold the most common viral infection in humans and the number-one reason why most people go to the doctor (and miss school).

A typical cold lasts for around a week and, while not life threatening, can be an awful experience. Most colds are caused by a group of complicated viruses called rhinoviruses. These microscopic pathogens are pretty much found everywhere and, from time to time, can break through the protective lining of your nose and throat when you inhale them.

When you are infected, your body produces chemicals called histamines which are responsible for most of the symptoms of the cold. The rhinoviruses are not able to live in your body for very long so generally can’t cause serious problems such as pneumonia.

There are 115 types of rhinovirus, that constantly change and mutate, which means that producing a vaccine that provides protection from the common cold is very difficult. But your body fights in its own way, producing specialised proteins called antibodies, which help protect your mucous membranes (nose, throat, eyes, mouth) from infection.

The group of antibodies produced in these areas is called immunoglobulin A (or IgA) and these antibodies are very good at dealing with these tiny invaders. But the IgA response is quite short lived and doesn’t offer long-term immunity.

So why no cure? The main reason is because of the many variations of rhinoviruses (and the other types of virus that cause colds) and because of the short-term immunity that IgA gives our body. Antibiotics have no effect on rhinoviruses (or any virus for that matter) and all we can do is treat the symptoms of our viral infection.

Medicines like aspirin, paracetamol or decongestants relieve the symptoms but can’t destroy the virus – your body does a pretty good job at that. Many people take herbs, honey, lemon or vitamin C when they have a cold and some even find chicken soup helps relieve the symptoms.

In fact, chicken soup can relieve congestion (a blocked nose) as it contains a mucus-thinning amino acid called cysteine, which helps control congestion-causing white cells called neutrophils (the same ones that make up pus).

Is there any hope of finding a cure? Maybe. A recent study, by scientists in Cambridge, has revealed a previously unknown way in which our bodies respond to viral infections.

Up until now scientists believed that antibodies could only destroy viruses when they were outside our cells. But the Cambridge scientists have discovered that antibodies can also fight viruses, such as those that cause a cold, from within infected cells.

The discovery of this previously unknown mechanism means treatments could be created to “supercharge” the human immune system, helping it to fight off viruses when they strike.

The researchers believe the findings could lead to a new type of antiviral drug which could be ready for clinical tests in a matter of years and might even take the form of a nasal spray or inhaler.

In other research, a group of scientists in the US are mapping the genome (genetic makeup) of all known virus strains that cause the common cold.

This will lead to a greater understanding of how these viruses function and should help us develop medicines to fight them in the future.

So, while no cure for the cold currently exists, there may be hope on the horizon. But in the meantime, I’d keep well stocked up with Kleenex and Calpol.

3 comments:

Stephen Curry said...

This is a very interesting blogpost. If I may, I'd like to add my tuppence worth since I have worked on picornaviruses - the group of viruses that includes human rhinovirus. People may be interested to know that this group also contains nasties such as poliovirus and foot-and-mouth disease virus. What that means is that all these viruses are built the same way: they consist of a roughly spherical shell of protein molecules that contains the virus genes.

In the case of human rhinovirus, it is true that one of the difficulties in formulating a good vaccine arises from the sheer variety of 'serotypes' - over 100 in total as was stated in the post. Effectively this means that a useful vaccine — which often consists of whole virus particles — would have to contain particles from all 100+ serotypes of rhinovirus. That's difficult to achieve.

One of the reasons that there is a very good vaccine for poliovirus is that it has only 3 serotypes. I have never had a satisfactory answer to the question of why rhinovirus — which is very similar in construction to poliovirus — should have so many serotypes. Perhaps it is due to the fact that they infect different parts of the body and so interact with the immune system in different ways?

So what about drugs? The struggle to produce drugs that are effective against the common cold has been an interesting one. Plenty of companies have tried but no-one has succeeded. Here the main problem (I think) is that the common cold is a mild, self-limiting condition. In other words, it's not usually very serious and you will get better by yourself in a few days. Drugs have been developed (for example, see here), but they're just not effective enough.

What was found in the study I linked to — if I remember correctly — was that if you took the drug after symptoms appeared (which is how you would normally dose yourself), there was no significant benefit: you didn't get better any quicker. The drug did help to prevent infection if people took it before they were infected. But this is not good enough for such a mild disease. Who is going to start popping pills from Autumn to Spring on the off-chance that you might come across a rhinovirus?

Stephen Curry said...

This is a very interesting blogpost. If I may, I'd like to add my tuppence worth since I have worked on picornaviruses - the group of viruses that includes human rhinovirus. People may be interested to know that this group also contains nasties such as poliovirus and foot-and-mouth disease virus. What that means is that all these viruses are built the same way: they consist of a roughly spherical shell of protein molecules that contains the virus genes.

In the case of human rhinovirus, it is true that one of the difficulties in formulating a good vaccine arises from the sheer variety of 'serotypes' - over 100 in total as was stated in the post. Effectively this means that a useful vaccine — which often consists of whole virus particles — would have to contain particles from all 100+ serotypes of rhinovirus. That's difficult to achieve.

One of the reasons that there is a very good vaccine for poliovirus is that it has only 3 serotypes. I have never had a satisfactory answer to the question of why rhinovirus — which is very similar in construction to poliovirus — should have so many serotypes. Perhaps it is due to the fact that they infect different parts of the body and so interact with the immune system in different ways?

So what about drugs? The struggle to produce drugs that are effective against the common cold has been an interesting one. Plenty of companies have tried but no-one has succeeded. Here the main problem (I think) is that the common cold is a mild, self-limiting condition. In other words, it's not usually very serious and you will get better by yourself in a few days. Drugs have been developed (for example, see here), but they're just not effective enough.

What was found in the study I linked to — if I remember correctly — was that if you took the drug after symptoms appeared (which is how you would normally dose yourself), there was no significant benefit: you didn't get better any quicker. The drug did help to prevent infection if people took it before they were infected. But this is not good enough for such a mild disease. Who is going to start popping pills from Autumn to Spring on the off-chance that you might come across a rhinovirus?

Humphrey Jones said...

Thanks for that Stephen - always good to have people working within the area giving us input. Thanks for the link too!