Claire Smith

Early life response to infection

Purpose of review Sepsis is a serious complication in preterm and term infants, yet our understanding of how neonates respond to infection remains poorly defined. Recent findings We describe our current clinical, cellular and molecular understanding of the neonatal host systemic response to infection. We find that host resilience essentially relies on innate immune mechanisms despite there being a complete repertoire of cellular components of the adaptive immune arm. The functional interplay between metabolism, immunity and microbiome further suggests that neonatal vulnerability to infection is not simply due to immaturity of the immune system but how immune homeostasis is regulated. Further research is required for exploring regulatory homeostatic mechanisms between innate and adaptive responses and microbiome colonization at birth, but which can impart an adverse trajectory to infection. Summary The vulnerability and resilience against infection in neonates, including extreme preterm infants, still remains poorly understood. We advance the view that greater consideration should be given to understanding the set point in the regulation of homeostatic control of innate and adaptive immunity and its interplay with metabolism and the newly acquired microbiome.

Identification of a human neonatal immune-metabolic network associated with bacterial infection

Understanding how human neonates respond to infection remains incomplete. Here, a system-level investigation of neonatal systemic responses to infection shows a surprisingly strong but unbalanced homeostatic immune response; developing an elevated set-point of myeloid regulatory signalling and sugar-lipid metabolism with concomitant inhibition of lymphoid responses. Innate immune-negative feedback opposes innate immune activation while suppression of T-cell co-stimulation is coincident with selective upregulation of CD85 co-inhibitory pathways. By deriving modules of co-expressed RNAs, we identify a limited set of networks associated with bacterial infection that exhibit high levels of inter-patient variability. Whereas, by integrating immune and metabolic pathways, we infer a patient-invariant 52-gene-classifier that predicts bacterial infection with high accuracy using a new independent patient population. This is further shown to have predictive value in identifying infection in suspected cases with blood culture-negative tests. Our results lay the foundation for future translation of host pathways in advancing diagnostic, prognostic and therapeutic strategies for neonatal sepsis.

Whole blood gene expression profiling of neonates with confirmed bacterial sepsis.

Neonatal infection remains a primary cause of infant morbidity and mortality worldwide and yet our understanding of how human neonates respond to infection remains incomplete. Changes in host gene expression in response to infection may occur in any part of the body, with the continuous interaction between blood and tissues allowing blood cells to act as biosensors for the changes. In this study we have used whole blood transcriptome profiling to systematically identify signatures and the pathway biology underlying the pathogenesis of neonatal infection. Blood samples were collected from neonates at the first clinical signs of suspected sepsis alongside age matched healthy control subjects. Here we report a detailed description of the study design, including clinical data collected, experimental methods used and data analysis workflows and which correspond with data in Gene Expression Omnibus (GEO) data sets (GSE25504). Our data set has allowed identification of a patient invariant 52-gene classifier that predicts bacterial infection with high accuracy and lays the foundation for advancing diagnostic, prognostic and therapeutic strategies for neonatal sepsis.

Quantitative assessment of human whole blood RNA as a potential biomarker for infectious disease

Infection remains a significant cause of morbidity and mortality especially in newborn infants. Analytical methods for diagnosing infection are severely limited in terms of sensitivity and specificity and require relatively large samples. It is proposed that stringent regulation of the human transcriptome affords a new molecular diagnostic approach based on measuring a highly specific systemic inflammatory response to infection, detectable at the RNA level. This proposition raises a number of as yet poorly characterised technical and biological variation issues that urgently need to be addressed. Here we report a quantitative assessment of methodological approaches for processing and extraction of RNA from small samples of infant whole blood and applying analysis of variation from biochip measurements. On the basis of testing and selection from a battery of assays we show that sufficient high quality RNA for analysis using multiplex array technology can be obtained from small neonatal samples. These findings formed the basis of implementing a set of robust clinical and experimental standard operating procedures for whole blood RNA samples from 58 infants. Modelling and analysis of variation between samples revealed significant sources of variation from the point of sample collection to processing and signal generation. These experiments further permitted power calculations to be run indicating the tractability and requirements of using changes in RNA expression profiles to detect different states between patient groups. Overall the results of our investigation provide an essential first step toward facilitating an alternative way for diagnosing infection from very small neonatal blood samples, providing methods and requirements for future chip-based studies.

Patent ductus arteriosus: time to grasp the nettle?

The management of patent ductus arteriosus is controversial, and there are diverse approaches to treatment, ranging from very conservative management through to early and aggressive securing of ductus closure, either pharmacologically or surgically. This lack of consensus on best management reflects a paucity of high quality randomised controlled trials, with many published studies focusing on establishing points of treatment, rather than looking for benefits of intervention over more conservative management. Despite this lack of good evidence views on ductus management can be entrenched, with accompanying loss of equipoise. This review looks at our current situation with regard to ductus arteriosus management and the need for good quality trials especially in the light of other published studies, concerning postnatal steroids, caffeine and oxygen which have demonstrated unexpected benefits – or sometimes unexpected harm – from long-familiar drugs.

Management of meconium aspiration syndrome

meconium aspiration syndrome (maS) affects 0.43–2.1 in 1000 live births and can be life-threatening. a variety of treatment strategies is used, many of which do not have a solid evidence base to support them, but do appear to be effective. Routine suction of the fetal pharynx prior to delivery of the shoulders is not effective in reducing the incidence of maS and neither is routine suction of the trachea after birth in vigorous infants. tracheal suction after birth is still recommended for infants who are not vigorous. after delivery close attention must be paid to the management of the respiratory status of these infants. Some will require ventilation, and surfactant, inhaled nitric oxide and high frequency oscillatory ventilation may all be of benefit in some cases. For the most severely affected, extracorporeal life support has been shown to be effective in reducing the mortality of this condition.

Draft Genome Sequences of Six Different Staphylococcus epidermidis Clones, Isolated Individually from Preterm Neonates Presenting with Sepsis at Edinburgh's Royal Infirmary

ABSTRACT Herein, we report the draft genome sequences of six individual Staphylococcus epidermidis clones, cultivated from blood taken from different preterm neonatal sepsis patients at the Royal Infirmary, Edinburgh, Scotland, United Kingdom.

80 Microarray Investigation of Host Rna Expression Profiles in Neonatal Infection

Background and aims: Infection causes significant neonatal morbidity and mortality. Currently available methods for diagnosing infection are unreliable. We aimed to examine differences in host RNA expression profiles between infants with confirmed infection and control infants using microarray technology. Methods: RNA was extracted from neonatal whole blood taken from infants with confirmed infection and from controls using a modified PAXgene™ Blood RNA system protocol. High quality RNA was run on Illumina® Human Whole-Genome Expression BeadChip microarrays. Normalised, validated microarray data was analysed to examine differences between control and infected samples. Functional annotation according to gene ontology and pathway analysis was performed. Results: 28 infected and 35 control samples were examined. Differential gene expression between infected and control groups was analysed: 448 features had >2-fold up-regulation and 341 features >2-fold down-regulation (p< 0.001) in infected compared to control infants. There was significant immune-related differential gene expression. Up-regulated genes in the infected group included genes involved in cytokine, complement, interferon and Toll Like Receptor related processes. Down-regulated genes included genes involved in antigen processing, MHC II activity and T cell activation and signalling. Conclusions: There is immune-related differential gene expression between infected and control infants. Many of our results corroborate findings previously published for adult and paediatric populations. In addition, these results provide evidence that neonates are capable of mounting a substantial immune response to infection. It is likely that, with larger studies and, with examination of training sets of data, immune gene expression signatures for neonatal infection can be defined.