The 2.5 Å structure of CD1c in complex with a mycobacterial lipid reveals an open groove ideally suited for diverse antigen presentation.

CD1 molecules function to present lipid-based antigens to T cells. Here we present the crystal structure of CD1c at 2.5 Å resolution, in complex with the pathogenic Mycobacterium tuberculosis antigen mannosyl-ß1-phosphomycoketide (MPM). CD1c accommodated MPM's methylated alkyl chain exclusively in the A' pocket, aided by a unique exit portal underneath the α1 helix. Most striking was an open F' pocket architecture lacking the closed cavity structure of other CD1 molecules, reminiscent of peptide binding grooves of classical major histocompatibility complex molecules. This feature, combined with tryptophan-fluorescence quenching during loading of a dodecameric lipopeptide antigen, provides a compelling model by which both the lipid and peptide moieties of the lipopeptide are involved in CD1c presentation of lipopeptides.

Outcomes of preterm infants receiving positive pressure support at term corrected gestation.

AIM: To establish the mortality rate to hospital discharge of very preterm infants who remain on positive pressure support (PPS) at term corrected gestation and describe factors that are associated with increased mortality. METHODS: Infants born <30 weeks' gestation between 1 January 2001 and 31 December 2009 who were receiving PPS at 40 weeks' postmenstrual age (PMA) were identified from our database, and their medical records reviewed. The fraction of inspired oxygen (FiO2 ), mean airway pressure and partial pressure of carbon dioxide (PaCO2 ) at 40 weeks' PMA were recorded. Receiver operating characteristic curves for mortality before discharge were generated. RESULTS: One thousand three hundred fifty-nine of 1572 infants survived to term. Forty-nine infants were receiving PPS at 40 weeks' PMA. Of these, 15 (31%) infants died before hospital discharge. All three infants who were ventilated via an endotracheal tube died. Increased oxygen requirement at term was associated with increased risk of death before discharge (area under curve (AUC) 0.75). FiO2 > 0.5 was associated with an 80% risk of death. PaCO2 was not predictive of death (AUC 0.49). CONCLUSIONS: Two thirds of very preterm infants who remained on PPS at 40 weeks' PMA survived to hospital discharge. Risk of death rises with increasing oxygen requirements. All five infants with FiO2 > 0.70 died.

Expression of CD1c enhances human invariant NKT cell activation by α-GalCer.

Invariant natural killer T (iNKT) cells are innate T lymphocytes that specifically recognize α-linked glycosphingolipids (α-GSLs) as antigens presented by CD1d molecules. Activating iNKT cells by administering α-GSLs improves disease outcomes in murine cancer models and, thus, there is great interest in the clinical potential of these lipids for treating human cancers. However, humans possess several other CD1 isoforms that are not present in mice and it is not clear whether these CD1 molecules, which also bind lipids, affect human iNKT cell responses. We demonstrate here that CD1c, which is co-expressed with CD1d on blood dendritic cells and on a fraction of B cells, is able to present α-galactosylceramide (α-GalCer) as a weak agonist to human iNKT cells, and that the presence of CD1c synergistically enhances α-GalCerdependent activation of iNKT cells by CD1d. Primary human B cells expressing CD1c induced stronger iNKT cell responses to α-GalCer than the CD1c- subset, and an antibody against CD1c inhibited iNKT cell cytokine secretion. These results suggest that therapeutic activation of human iNKT cells by α-GSLs will be driven preferentially by CD1c+ cell types. Thus, B cell neoplasias that co-express CD1c and CD1d may be particularly susceptible to α-GSL therapy, and cancer vaccines using α-GSLs as adjuvants may be most effective when presented by CD1c+ antigen-presenting cells.

Neonatal exchange transfusions in the 21st century: a single hospital study.

AIM: In the 21st century, neonatal exchange transfusions (ETs) are uncommon procedures usually performed in tertiary neonatal units. As junior clinical staff now lack familiarity with the procedure, it is important to maintain awareness of its complications in order to manage clinical risks and counsel parents appropriately. The study aims to analyse the ET rate, its indications and its associated complications, in a single tertiary centre in the 21st century. METHODS: This is a retrospective cohort study of all infants receiving ET from 1 January 2001 to 31 December 2010 at the Royal Women's Hospital, Melbourne. RESULTS: Sixty-four ETs were performed in 51 infants, an average of 6.4 ETs per year. Forty-nine (96%) infants were exchanged for hyperbilirubinaemia and two (4%) for anaemia. Thirty-six (71%) infants had Rhesus haemolytic disease of the newborn and six (12%) had ABO incompatibility. Six infants were intubated and mechanically ventilated after ET; these infants were significantly more acidotic during the ET than those who were never on respiratory support (mean pH 7.153 and 7.309 respectively, mean difference -0.156, 95% CI -0.196 to -0.116, t = 7.85, P < 0.001). Overall mortality was 8% (n = 4). CONCLUSIONS: Our current ET rate is very low compared with historical data. It is difficult to ascribe mortality and morbidity directly to ET as the procedure is now often performed on smaller, sicker or more premature infants whose risks of mortality and morbidity are high regardless of ET. Prospective multi-centre studies are needed to provide adequate data to analyse complications in greater detail.

Recognition of lyso-phospholipids by human natural killer T lymphocytes.

Natural killer T (NKT) cells are a subset of T lymphocytes with potent immunoregulatory properties. Recognition of self-antigens presented by CD1d molecules is an important route of NKT cell activation; however, the molecular identity of specific autoantigens that stimulate human NKT cells remains unclear. Here, we have analyzed human NKT cell recognition of CD1d cellular ligands. The most clearly antigenic species was lyso-phosphatidylcholine (LPC). Diacylated phosphatidylcholine and lyso-phosphoglycerols differing in the chemistry of the head group stimulated only weak responses from human NKT cells. However, lyso-sphingomyelin, which shares the phosphocholine head group of LPC, also activated NKT cells. Antigen-presenting cells pulsed with LPC were capable of stimulating increased cytokine responses by NKT cell clones and by freshly isolated peripheral blood lymphocytes. These results demonstrate that human NKT cells recognize cholinated lyso-phospholipids as antigens presented by CD1d. Since these lyso-phospholipids serve as lipid messengers in normal physiological processes and are present at elevated levels during inflammatory responses, these findings point to a novel link between NKT cells and cellular signaling pathways that are associated with human disease pathophysiology.

Lung ultrasound immediately after birth to describe normal neonatal transition: an observational study.

OBJECTIVE: Lung ultrasound (LUS) has shown promise as a diagnostic tool for the evaluation of the newborn with respiratory distress. No study has described LUS during 'normal' transition. Our goal was to characterise the appearance of serial LUS in healthy newborns from the first minutes after birth until airway liquid clearance is achieved. STUDY DESIGN: Prospective observational study. SETTING: Single-centre tertiary perinatal centre in Australia. PATIENTS: Of 115 infants born at ≥35 weeks gestational age, mean (SD) gestational age of 386/7 weeks±11 days, mean birth weight of 3380±555 g, 51 were delivered vaginally, 14 via caesarean section (CS) after labour and 50 infants via elective CS. INTERVENTIONS: We obtained serial LUS videos via the right and left axillae at 1-10 min, 11-20 min and 1, 2, 4 and 24 hours after birth. MAIN OUTCOME MEASURES: LUS videos were graded for aeration and liquid clearance according to a previously validated system. RESULTS: We analysed 1168 LUS video recordings. As assessed by LUS, lung aeration and airway liquid clearance occurred quickly. All infants had an established pleural line at the first examination (median=2 (1-4) min). Only 14% of infants had substantial liquid retention at 10 min after birth. 49%, 78% and 100% of infants had completed airway liquid clearance at 2, 4 and 24 hours, respectively. CONCLUSIONS: In healthy transitioning newborn infants, lung aeration and partial liquid clearance are achieved on the first minutes after birth with complete liquid clearance typically achieved within the first 4 hours of birth. TRIAL REGISTRATION NUMBER: ANZCT 12615000380594.

Lung ultrasound during the initiation of breathing in healthy term and late preterm infants immediately after birth, a prospective, observational study.

INTRODUCTION: Lung ultrasound (LUS) has shown promise for evaluation of newborns with respiratory distress. However, no study has described the appearance of LUS during the initiation of breathing. We used LUS to describe the appearance of the lungs in healthy infants immediately after birth, starting with the infant's first breath, through the first 20min after birth. METHODS: This was a single-center observational study enrolling neonates born at ≥35 weeks. We obtained LUS video recordings with the initiation of breathing. Recordings that captured one of the 1st four breaths after birth were included. We also obtained recordings at 1-10 and 11-20min after birth. Recordings were graded using a modified version of a previously published system, with additional grades to describe the appearance of the lungs prior to establishment of the pleural line. RESULTS: We studied 63 infants, mean gestational age=391/7±2 days, mean weight=3473g±422, 33 infants were delivered vaginally and 30 via cesarean section. We captured the first breath after birth in 28 infants and within the first four breaths from the remaining 35 infants. The pleural line was established by a median of 4 breaths (3-6). At the 1-10min examination, all infants had an established pleural line and 89% demonstrated substantial liquid clearance. At the 11-20min examination, all infants had substantial liquid clearance. CONCLUSION: Establishment of the pleural line, indicating lung aeration and substantial liquid clearance is achieved with the first few breaths after birth in term and near term infants.

Challenges of neurodevelopmental follow-up for extremely preterm infants at two years.

AIM: This study examined the rates of follow-up for a cohort of extremely preterm (EP -<28weeks gestation) and/or extremely low birthweight (ELBW -<1000g) children at two years with related perinatal and geographical factors. The secondary aim was to determine the rates of developmental delay and disability. METHODS: A retrospective review of two year follow-up data for all EP and/or ELBW infants born in a large tertiary neonatal hospital over a two year period was undertaken. Neurodevelopmental outcome was assessed using the Bayley Scales of Infant and Toddler Development Scale - 3rd edition (Bayley-III) and neurosensory disability was assessed by a paediatrician using a standard proforma. Rates of delay (composite score≥1SD below mean) were determined using the Bayley-III test norms and a local cohort normative group. Attrition rates and reasons for loss to follow-up were determined. RESULTS: Only 50% (109/219) of eligible children participated in the follow-up. The follow-up rate for children engaged in an ongoing research project was excellent at 98% (58/59), however it was only 32% (51/160) for children following the clinical pathway. The main reason for not attending the follow-up was loss of contact. Factors associated with attendance included a lower gestation, sepsis and living in the metropolitan areas. The rates of delay in this cohort were greater with reference to local cohort normative data compared to Bayley-III test norms with an overall rate of delay of 72% (95%CI, 63% to 81%) compared to 38% (95%CI, 29% to 50%). CONCLUSIONS: Follow-up of EP/ELBW infants to two years is an important part of clinical care, however the high rate of attrition in routine clinical follow-up and consequent difficulty in accurately determining rates of delay highlight challenges for centres providing ongoing care.

The relationship between ventricular size at 1 month and outcome at 2 years in infants less than 30 weeks' gestation.

BACKGROUND: Cranial ultrasound cerebral biometric measurements have been used in preterm neonates, particularly in cases of ventriculomegaly. While cerebral biometric measures using MRI have been found to correlate with long-term outcome, the relationship between cranial ultrasound biometric measures and neurodevelopmental outcome has not been established. OBJECTIVE: To assess the relationship between ventricular size at 1 month of age using cranial ultrasound and neurodevelopmental outcome at 2 years in very preterm infants. METHOD: Digital cranial ultrasound images taken between 25 and 35 days of age of 44 infants born at less than 30 weeks' gestation were analysed independently by two observers. Infants with significant ultrasound abnormalities were excluded. A range of ultrasound linear measures were correlated with Bayley Scales of Infant and Toddler Development, Third Edition (Bayley-III) motor, language and cognitive composite scores at 2 years using linear regression. RESULTS: Larger lateral ventricular sizes (anterior horn width, ventricular height, midbody ventricular height) and larger ventricular-brain biparietal ratios were related to poorer motor composite score at 2 years. A ventricular-brain ratio of less than 0.3 was reassuring with regard to motor outcome. Poorer language composite scores at 2 years were associated with larger midbody ventricular heights. There was little evidence of a relationship with the cognitive composite score. CONCLUSIONS: Larger lateral ventricles in the parietal region at a month of age were related to poorer motor development at 2 years. Larger ventricular measurements were also related to slower early language development. The role of cranial ultrasound biometric measures as biomarkers of later outcome in very preterm infants warrants further investigation.