Epigenetic Mechanisms in Early Life Viral Respiratory Infections

Early-life respiratory viral infections represent a major global health burden and are key determinants of long-term susceptibility to chronic respiratory diseases. In neonates the immaturity of the immune system contributes to the high incidence and severity of these infections. Because humans are born with a mainly naive adaptive immune system, the host protection in early life greatly relies on the innate immune cells. Interestingly, innate immune cells have been recently shown to develop traits of immune memory. Both adaptive and innate immune memory formation are, among others, mediated by epigenetic mechanisms such as DNA methylation, histone modifications, and non-coding RNAs. This review comprehensively analyzes evidence of the changes in epigenetic modifications before and after respiratory infection in childhood. Understanding how epigenetic programming modulates immune cells in early life may open new avenues for preventive interventions to respiratory viral infection, enhancing antiviral defense in infancy and reducing the long-term consequences of respiratory infections.