The majority of infants in most markets receive a variety of mandatory vaccines around the age of six weeks in order to provide them with an immune boost and protection against various diseases.
However, when these infants come into contact with antibiotic usage whether at the neonatal (during pregnancy) or post-natal stage (via breastfeeding mothers), this has been found to negatively impact their natural immune response and antibody production.
“Based on a study conducted on over 250 full-term infants that were delivered naturally, we found that antibody titers (a representation of antibody levels in a blood sample) were decreased in infants with early antibiotic exposure,” South Australian Health and Medical Research Institute(SAHMRI) Systems Immunology Laboratory Head and Programme Director Professor David Lynn told the floor at the recent Growth Asia Summit 2024.
“This was found when analysing stool samples of the infants at both seven months and 15 months of age, and was especially significant in those that had experienced neonatal exposure to antibiotics.
“These findings are important as the efficacy and protection of vaccines is usually seroprotective [which means that the] antibody levels would affect the levels of protection afforded to the vaccinated subject.”
The team also linked these immunogenic responses to the gut health of the infants, suggesting a potential pathway where gut microbiota improvement would be able to also improve immune protection in those that had been exposed to antibiotics.
“To determine the changes induced in the gut microbiota by antibiotic exposure, we collected stool specimens at week one of life and then just prior to vaccine administration at week six of life,” Prof Lynn said.
“Based on our analysis using metagenomic sequencing, we found that infants can actually be grouped into six major microbiota community types, with the classification tending to differ based on their antibiotic exposure levels.”
A link was also found between the levels of bifidobacterium or probiotics in the guts of the infants, and their immune response to vaccination.
“Neonatal antibiotic exposure was associated with a significantly reduced relevant abundance of Bifidobacteriaceae, [and conversely] a relative abundance of Bifidobacterium at six weeks of age was associated with better antibody responses to vaccination,” he added.
“As such, the working hypothesis here is that if there is a way to restore the gut microbiome for those infants that have been exposed to antibiotics, this will then improve their antibody response to vaccination.”
“In line with this, we have started a study where we have isolated gut microbiota cultures from infants that have or have not been exposed to antibiotics and are colonising these in germ-free mice – these mice are then immunised with vaccines to observe their antibody generation.
“What we found was that the colonisation of these mice with a probiotic containing Bifidobacteriaceae led to significant antibody responses [including in] those that with antibiotic exposure].
“The indication here for antibiotic-exposed infants is that certain probiotics have the potential to restore their mechanism of antibody immune response.”
Infant study
Moving forward, the researchers are recruiting 500 infants for a randomised controlled trial to further assess the effects of probiotic intervention on immune responses to vaccination.
“The focus will be on infants that are already exposed to antibiotics [and getting a vaccination],” Prof Lynn said.
“The trial will be randomised such that some of them will get the placebo and the others the probiotic, and from there we will be able to analyse the impact of the probiotic on antibody generation during the immune response.”
