Abstract
Newborns are at increased risk of infection due to genetic, epigenetic, and environmental
factors. Herein we examine the roles of the neonatal innate immune system in host
defense against bacterial and viral infections. Full-term newborns express a distinct
innate immune system biased toward TH2-/TH17-polarizing and anti-inflammatory cytokine production with relative impairment in
TH1-polarizing cytokine production that leaves them particularly vulnerable to infection
with intracellular pathogens. In addition to these distinct features, preterm newborns
also have fragile skin, impaired TH17-polarizing cytokine production, and deficient expression of complement and of antimicrobial
proteins and peptides (APPs) that likely contribute to susceptibility to pyogenic
bacteria. Ongoing research is identifying APPs, including bacterial/permeability-increasing
protein and lactoferrin, as well as pattern recognition receptor agonists that may
serve to enhance protective newborn and infant immune responses as stand-alone immune
response modifiers or vaccine adjuvants.
Keywords
adjuvants - neonatal sepsis - pathogen recognition receptors - innate immunity