Most vaccines include an adjuvant. The main ingredient of the vaccine whether it is a dead or disabled pathogen, or just a part of the virus or bacteria causing the disease primes the body's immune system so it knows what to attack in case of infection. But the adjuvant is needed as well to stimulate this process.
While the need for adjuvants in vaccines has been recognised for nearly 100 years, the way adjuvants work has only recently been understood. The result has been that only a small set of adjuvants is used in current vaccines, often for historical reasons.
The most common adjuvant by far is alum, an aluminium-containing compound that has been given in many different vaccines worldwide for decades. However, alum is not the most potent adjuvant for many vaccine designs.
'There is a need to develop new adjuvants to get the most appropriate immune response from vaccines,' says Professor Sattentau, who is also a James Martin Senior Fellow at the Oxford Martin School, University of Oxford.
The Oxford University team found that PEI, a standard polymer often used in genetic and cell biology, has strong adjuvant activity.
When included in a vaccine with a protein from HIV, flu or herpes virus, mice subsequently mounted a strong immune response against that virus. The immune response was stronger than with other adjuvants that are currently being investigated.
The team also showed that PEI is a potent adjuvant in rabbits, showing the effect is not just specific to mice and could be general.
Another potential advantage of PEI is that it works well as an adjuvant for 'mucosal vaccines'. These vaccines are taken up the nose or in the mouth and absorbed through the mucus-lined tissues there, getting rid of any pain and anxiety from a
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