Correlation of levels of alpha-defensins determined by HPLC-ESI-MS in bronchoalveolar lavage fluid with the diagnosis of pneumonia in premature neonates

Immature neutrophils in cord blood exert increased expression of genes associated with antimicrobial function

Introduction

The immune systems of both the mother and the newborn face significant challenges during birth. Proper immune regulation after birth is essential for the survival of neonates. Numerous studies have demonstrated that the neonatal immune system is relatively immature, particularly in its adaptive arm, placing the primary responsibility for immune surveillance on innate immunity.

Methods

Given the significant role of neutrophils in protecting the neonate after birth, we conducted a study investigating the properties of neutrophils in newborn cord blood using various methodological approaches.

Results

Our findings demonstrate the presence of immature low-density neutrophils in the cord blood, which are likely responsible for the observed elevated expression of genes coding for proteins essential to antimicrobial response, including myeloperoxidase, neutrophils elastase, and defensins.

Discussion

We propose that these cells function normally and support the protection of newborns early after birth. Furthermore, our results suggest that the mode of delivery might significantly influence the programming of neutrophil function. The presented findings emphasize the importance of distinct neutrophil subpopulations in neonatal immunity and their potential impact on early postnatal health.

Antimicrobial Peptides in Early-Life Host Defense, Perinatal Infections, and Necrotizing Enterocolitis—An Update

Host defense against early-life infections such as chorioamnionitis, neonatal sepsis, or necrotizing enterocolitis (NEC) relies primarily on innate immunity, in which antimicrobial peptides (AMPs) play a major role. AMPs that are important for the fetus and neonate include α and β defensins, cathelicidin LL-37, antiproteases (elafin, SLPI), and hepcidin. They can be produced by the fetus or neonate, the placenta, chorioamniotic membranes, recruited neutrophils, and milk-protein ingestion or proteolysis. They possess antimicrobial, immunomodulating, inflammation-regulating, and tissue-repairing properties. AMPs are expressed as early as the 13th week and increase progressively through gestation. Limited studies are available on AMP expression and levels in the fetus and neonate. Nevertheless, existing evidence supports the role of AMPs in pathogenesis of chorioamnionitis, neonatal sepsis, and NEC, and their association with disease severity. This suggests a potential role of AMPs in diagnosis, prevention, prognosis, and treatment of sepsis and NEC. Herein, we present an overview of the antimicrobial and immunomodulating properties of human AMPs, their sources in the intrauterine environment, fetus, and neonate, and their changes during pre- and post-natal infections and NEC. We also discuss emerging data regarding the potential utility of AMPs in early-life infections, as diagnostic or predictive biomarkers and as therapeutic alternatives or adjuncts to antibiotic therapy considering the increase of antibiotic resistance in neonatal intensive care units.

Association of high levels of α-defensins and S100A proteins with Candida mannan detection in bronchoalveolar lavage fluid of preterm neonates

BACKGROUND

Candida mannan (Mn) detection in bronchoalveolar lavage fluid (BALF) was shown to be useful for earlier identification and preemptive therapy targeting in preterm infants at high risk of invasive Candida infection. We investigated whether early detection of Candida Mn in BALF is associated with the presence of some neutrophilic products, as markers of prenatal infection/inflammation.

METHODS

BALF specimens were collected during the first 48 h of life from mechanically ventilated preterm newborns. Samples were analyzed by high-performance liquid chromatography-electrospray ionization-mass spectrometry. The relative amounts of α-defensins 1-4 and S100A proteins were measured by extracted ion current peak area. Absolute and differential white cell counts in BALF were obtained. Mn antigen concentrations were determined by the Platelia Candida antigen kit.

RESULTS

Twenty-five studied neonates were divided into two groups: Mn-positive group and Mn-negative group. Levels of α-defensins 1-4 and S100A12 were significantly higher in the Mn-positive group than in the Mn-negative group. Moreover, positive significant correlations between the absolute number of neutrophils and the levels of α-defensins 1-4 and S100A8 were observed.

CONCLUSION

The detection of Mn antigen in BALF of preterm infants is consistent with evidence of an innate immune response in their lungs as demonstrated by higher levels of α-defensins and S100A proteins.