Inhalable viral vaccines

Researchers have developed a new kind of breathable vaccine, a paper released in the journal Science announced this week.

When most of us think of a vaccine, we think of a needle shot in the arm. However, it has been suggested that this might not be the best method of vaccination for many diseases.

The fact is that most viruses do not naturally enter the body through cuts and grazes - as occurs with a hypodermic needle - but are breathed in from the air or even eaten. Because of this, our body is much better evolved to mount an immune response to something that is eaten or inhaled than to something that is injected. This means that, if we can introduce a vaccine into the body in a more natural way - for example, by breathing it in - it might be more effective than if injected.

The problem is that most small particles that are inhaled - including the weakened viruses used for vaccination - are cleared from the airways without ever entering the body or encountering the immune system. This means that they are not around for long enough for the body to develop an immune response to the virus and so are mostly ineffective.

However, a group at the Massachusetts Institute of Technology (MIT) might have found a way around this problem.

The group, which was led Darrell Irvine, created a multi-layered fat capsule which could surround the weakened virus used for vaccination. Although still extremely small - only nanometers across - the drops are larger than the weakened virus alone and their fat composition make them more likely to be taken up by the body.

When compared to inhalation of the weakened virus alone - without the nanocapsule -  or to injection of the virus in nanocapsules, the results of vaccination using inhalation of these nanocapsules were impressive.

Mice vaccinated using inhalation of the nanocapsules almost invariably survived subsequent challenge with the real live virus. In contrast, mice which had been vaccinated using the other techniques did not.

Although this technique has only been tested in mice so far, it provides real hope as a possible new method of vaccination against a variety of diseases in the future.