Fecal expression of human β-defensin-2 following birth.

Background: Newborns display high intestinal permeability and a naive adaptive immune system, but infections are rare, indicating strong innate defense mechanisms. Objective: To measure the kinetics of fecal -defensin-2 (HBD2), an induc- ible endogenous antimicrobial peptide produced by intesti- nal epithelial cells, in full-term and preterm infants. Meth- ods: As a first step of this bicentric study, we enrolled 30 healthy full-term infants and 20 healthy preterm infants, with fecal samples collected at days 3, 7 12 and 30 in full-term infants and at days 15, 30 and 60 in preterm infants. As a sec- ond step, we enrolled 10 preterm infants with intestinal dis- tress, either necrotizing enterocolitis (NEC) Bell’s stage III (n = 3) or isolated rectal bleeding (n = 7) and 20 controls, cross-matched for gestational age and age at sampling. Re- sults: HBD2 decreased significantly from day 3 to day 7 (227 ng/g; 14–440 vs. 117 ng/g; 30–470, p = 0.01) then moderate- ly until day 30 (84 ng/g; 10–500) in healthy full-term infants. Healthy preterm infants showed similar high levels between days 15 and 60 (82 ng/g; 30–154 and 85 ng/g; 26–390, respec- tively). No significant variation of fecal HBD2 levels was ob- served between infants with clinical features of intestinal distress (77 ng/g, 2–1,271) and cross-matched controls (56 ng/g, 31–164). However, 2/3 infants with NEC and 1/7 infants with isolated rectal bleeding had HBD2 levels above the maximal level observed in controls. Conclusions: The kinet- ics of fecal HBD2 in the neonatal period indicate that this inducible defensin can be detected at high level in the feces of full-term and preterm infants, independently of gesta- tional age or mode of feeding. The potential role of fecal HBD2 in detecting NEC is suggested