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Irish scientists find distinct immune system in newborn babies

Researchers identify ‘danger signals’ efficient at triggering immune response in infants.

Newborn babies do not respond optimally to most vaccines due to their immature immune system. Photograph: Nicole S Young/E+/Getty

Irish scientists have discovered a distinct immune response system in newborn babies, which could lead to a reduction in the age at which vaccines can be first administered and in the need for “multiple booster” shots.

Researchers from TCD School of Medicine and the National Children’s Research Centre (NCRC), attached to Our Lady’s Children’s Hospital, Crumlin, have identified what they describe as “a class of danger signals” that are highly efficient at triggering an immune response in young infants.

As infection remains the most common cause of death in early life, vaccination is by far the most effective intervention at preventing infectious disease. Newborn babies (neonates), however, do not respond optimally to most vaccines due to their immature immune system, explained researcher Dr Sarah Doyle of the NCRC.

For this reason immunisations are scheduled over the first 13 months of life to coincide with the maturation of the infants’ immune system. This leaves a window of vulnerability where newborns and young infants are susceptible to vaccine-preventable infections, especially for vaccines such as the MMR that are only administered when a child is one year old.

“Vaccines have two key components, one of which is an ‘adjuvant’,” Dr Doyle added. “These adjuvants are ‘danger signals’ that instruct the immune system to mount a response to the infection, which in the case of a vaccine is usually an attenuated, inactive form, or fragment of the bacteria or virus.”

Response

The adjuvant is critical not only for triggering the immune system into action, but also in directing the type of response best suited to fight a particular infection.

“Many adjuvants used in vaccines today were developed in adults, however babies and children are not simply little adults, and because of this, a child’s immune system responds differently than an adult’s immune system does,” said Dr Kiva Brennan of TCD School of Medicine, lead author of their study which has been published in Journal of Immunology.

As a result, the key to improving vaccine efficacy is the design of adjuvants that specifically target and kick the newborn immune response into action.

“We know that the formation of the microbiome (natural microbes that live mainly in intestines) is a critical step in a baby’s development, where ‘good bacteria’ in the gut and on the skin establish and start functioning, and it is thought that newborns do not mount strong immune responses to allow for such colonisation by these good bacteria.”

The scientists suspected newborns may retain a more robust immune response to viruses. By exploring this theory, they found a class of adjuvants that activate specialised sensors, which are critical in the response, and drove a very strong immune response in newborns where other microbial infections arise.

Dr Doyle added: “These sensors are normally activated in response to viral infection and direct the immune system to clear viral infections. Harnessing these efficient anti-viral immune responses will help in the design of targeted adjuvants for paediatric vaccines by directly activating immune responses that are fully functional in neonates and infants.”

She welcomed confirmation Children’s Medical & Research Foundation, a charity attached to the Crumlin hospital, has committed to funding further research in this area.

“Paediatric research is seriously underfunded in Ireland. Less than 2 per cent of overall medical research funding in Ireland is for paediatrics. The funding they provide is absolutely vital and the results of this research could impact hundreds of thousands of children,” she added.

Parents and children attending the National Maternity Hospital, Holles Street and Our Lady’s Children’s Hospital, Crumlin, participated in the study.

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