Nanoparticle trick 'boosts body's vaccine response'

Nanoparticles in the lymph node after injection
Image caption Nanoparticles (green) pictured in the lymph node (red) just half an hour after injection

Tiny capsules engineered to mimic part of the body's immune system could strengthen its response to vaccines, say researchers.

The nanoparticles, described in the journal Nature Materials, are a message sent from cells in the skin to warn of a threat.

Scientists from Duke University in the US said mice given them as part of a vaccine coped with otherwise lethal infections.

They could soon be suitable for humans.

Vaccination involves priming the immune system to recognise particular bacteria or viruses, so that it is ready to counter-attack quickly in the event of a genuine infection.

As well as a deactivated or weakened version of the bacteria or virus in question, many vaccines contain "adjuvants" - extra ingredients designed to enhance this priming process.

The Duke University team aimed to hijack a natural immune response involving cells called mast cells found in the skin.

These cells are a key part of the driving force behind the itching and swelling during an allergic reaction, but are also thought to play a role in the "innate immune system" which reacts to infection.

It is believed that when they encounter certain bacteria and viruses, they release small capsules called "granules", which contain a body chemical called tumour necrosis factor (TNF).

These travel to nearby lymph nodes, where the immune response to the infection can begin to be mobilised.

The researchers produced their own granule, also carrying TNF, designed to behave in the same way.

When injected at the same time as the vaccine, they are set up to travel to the lymph node and release the chemical, as if sent by an activated mast cell, and hopefully producing a more powerful immune response to the vaccine contents.

To test this, they vaccinated mice against influenza A, adding the nanoparticle "granules".

When exposed to a level of the virus which would normally prove lethal, the vaccinated mice had an improved survival rate.

The researchers said it would be possible to add different immune system chemicals to the nanoparticles to tailor the response to exactly the type of vaccine involved.

Dr Soman Abraham, who led the team, said that the individual chemicals used were already approved for use in humans in the US.

He said: "There is a lot of interest in nanoparticle-based therapy, but we are basing our materials on our observation of mast cells in nature.

"This is an informed application to deliver the right material to the right place in the body to get the most effective immune reaction."

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