| Description |
Millions of neonates die each year worldwide with almost half of these deaths caused by severe infections resulting in sepsis. Preterm infants have higher rates of sepsis and may be at increased risk of severe complications, including death. The reports on frequency of early onset sepsis (EOS) and late onset sepsis (LOS) among neonates vary significantly depending on gestational age (GA), weight of newborn, and country of birth. There is no clearly established GA cutoff that separate neonates who are relatively resistant or susceptible to infection. It is thought that newborn susceptibility to infections is due to the immaturity of their immune system. However, recent discovery of residual levels of myeloid derived suppressor cells (MDSC) in the cord blood (CB) of term neonates suggested a potential role for MDSC in neonatal susceptibility to microbial infections. MDSC are best known for their negative role in the development of anti-cancer immune responses. Recently, it has been reported that elevated levels of MDSC are present in the peripheral blood of adult patients with sepsis. We hypothesize that residual MDSC present in the CB of newborns can serve as a biomarker of neonatal infection and specifically, LOS. The main purpose of this project was to establish a GA cutoff point that separates "resistant" and "susceptible" to LOS neonatal cohorts and to develop protocols for detection of various subsets of MDSC. Additionally, protocols for MDSC isolation using microbead technology were developed. Isolated MDSC will be used in future studies to establish iv mechanisms by which MDSC modulate immune responses in septic and healthy neonates. To identify GA cutoff for the selection of suitable participants for future study cohorts, medical record reviews of neonates hospitalized at the University of Utah Hospital from January 1, 2006-September 30, 2015 were conducted and etiologies of LOS were assessed. Lastly, this study collected CB samples from term neonates for MDSC isolation and phenotypic analysis of MDSC subsets. It was determined that GA of 30 weeks is the optimal cutoff point for selecting a cohort to study the association of susceptibility of neonates to LOS and presence of MDSC in their CB. Coagulase negative Staphylococcus (CoNS) was identified as the dominant bacterial strain causing LOS in neonates (47.4%). Vancomycin was found to be the most prescribed antibiotic for treatment of LOS. Evaluation of term neonatal CB identified 4 subsets of MDSC of neonates and a protocol was developed to guide future evaluations. The percentages of MDSC subsets among term neonates varied. The mean percentages were for granulocytic MDSC (G-MDSC) 6.4%, CD14low CD15hi 0.5%, CD14lowCD15low/inter 2.8%, and monocytic MDSC 0.4%. Additionally, an isolation protocol of MDSC and G-MDSC from CB using microbead technology was developed. The results of this research will provide a foundation for future study endeavors to use microbead isolation techniques to determine the suppressive functions of MDSC subsets in CB and provide a platform to explore ideas to differentiate MDSC or block their suppressive activity. |
