Many factors influence a child’s subsequent susceptibility to respiratory tract infection (RTI), including breastfeeding, crowded conditions, and exposure to environmental tobacco. Now researchers have found that asymptomatic viral infection in the first days of a baby’s life are linked to a greater risk of respiratory infections in later life.
The new research, published in Nature Microbiology, was conducted as part of the Microbiome Utrecht Infant Study (MUIS), a healthy infant birth cohort study that’s been running for 6 years.
In their study, the authors explained how the respiratory tract is “populated by a specialized microbial ecosystem, which is seeded during and directly following birth,” adding that, “despite recognition of many host and environmental factors known to modulate RTI susceptibility, the mechanism by which a child develops recurrent or severe RTIs, while others remain healthy, remains largely unknown”.
Researchers from the University of Edinburgh and University Medical Centre Utrecht (the Netherlands) examined nasal mucosa samples of 114 babies at various times from birth until 12 months of age. They then analyzed the gene activity of the babies’ nasal mucosa, the microbes present in the lining of the nose, and any viruses that infected the children.
Interferon-related mucosal gene activity
The researchers described how the microbiome – the community of microbes in the body – of a newborn baby can be influenced by many things, including delivery method, breastfeeding, antibiotics and the hospital environment. They highlighted how viruses were found to interact with a newborn’s immune system and microbiome in a way that affected both a child’s risk, and number, of subsequent infections.
They explained how when a viral infection was detected in the first days after birth, which they said largely occurred asymptomatically, specific mucosal genes were activated – genes involved with interferons – coinciding with a change in the composition of the microbiome, promoting the growth of potentially harmful microbes.
“The interferon-related gene activity caused by an early first viral infection is thought to create a proinflammatory environment that makes babies susceptible to future infections,” they said, adding that in their study they have demonstrated that “first asymptomatic viral encounters were associated with increased interferon signaling, and preceded the development of disadvantageous respiratory microbiota profiles and clinical RTIs”.
Proinflammatory and microbiologically perturbed environment
Debby Bogaert, PhD, chair of paediatric medicine at the University of Edinburgh, said: “We were surprised to see viral infections occur so early in life, and go mostly unnoticed, probably because the infant’s immune system is in what is known as a state of tolerance after birth. Despite this, these infections seem to affect a normal immune development, which is important to know.”
The authors wrote that their data supports the hypothesis that first viral encounters trigger an interferon-associated proinflammatory environment, which then further drives airway inflammation and symptomatology in a “self-enforcing positive feedback loop”. They said that this “proinflammatory and microbiologically perturbed environment in turn renders an individual more vulnerable to recurrent viral-induced RTIs”.
Wouter de Steenhuijsen, PhD, postdoctoral investigator at University Medical Centre Utrecht, said: “Although further work will be needed to confirm the causality of our findings, the data from this study indicate that early-life encounters with respiratory viruses – especially during the first days of life – may set the tone for subsequent non-beneficial host-microbe interactions, which are related to an infection risk and possibly long term respiratory health.”
Dr. Bogaert added: “Only from birth onwards will an infant start to develop its microbiome. Limiting the number of viral encounters in those first days to weeks of life might be essential for a healthy immune and microbiome development, and consequently long term respiratory health.”
A version of this article first appeared on Medscape UK.