The neonatal immune system

Nanoparticle-Induced Augmentation of Neutrophils' Phagocytosis of Bacteria

Despite the power of antibiotics, bacterial infections remain a major killer, due to antibiotic resistance and hosts with dysregulated immune systems. We and others have been developing drug-loaded nanoparticles that home to the sites of infection and inflammation via engineered tropism for neutrophils, the first-responder leukocytes in bacterial infections. Here, we examined how a member of a broad class of neutrophil-tropic nanoparticles affects neutrophil behavior, specifically questioning whether the nanoparticles attenuate an important function, bacterial phagocytosis. We found these nanoparticles actually augment phagocytosis of non-opsonized bacteria, increasing it by ∼50%. We showed this augmentation of phagocytosis is likely co-opting an evolved response, as opsonized bacteria also augment phagocytosis of non-opsonized bacteria. Enhancing phagocytosis of non-opsonized bacteria may prove particularly beneficial in two clinical situations: in hypocomplementemic patients (meaning low levels of the main bacterial opsonins, complement proteins, seen in conditions such as neonatal sepsis and liver failure) or for bacteria that are largely resistant to complement opsonization (e.g., Neisseria). Additionally, we observe that; 1) prior treatment with bacteria augments neutrophil uptake of neutrophil-tropic nanoparticles; 2) neutrophil-tropic nanoparticles colocalize with bacteria inside of neutrophils. The observation that neutrophil-tropic nanoparticles enhance neutrophil phagocytosis and localize with bacteria inside neutrophils suggests that these nanoparticles will serve as useful carriers for drugs to ameliorate bacterial diseases.

Escherichia Coli Specific Secretory IgA and Cytokines in Human Milk from Mothers of Different Ethnic Groups Resident in Northern Italy

Breast milk supplies many bioactive components. Neonates protection from pathogenic bacteria is mainly attributable to secretory IgA antibodies present in human milk in an amount depending on previous antigenic exposure. To bring new details into the field of immunological memory in secretory immunity, we evaluated the production of s-IgA specific for E. coli (E. coli s-IgA), and of proinflammatory (IL-6 and IL-8) or anti-inflammatory (IL-10) cytokines in the milk of mothers of different ethnic groups exposed in the past to poor conditions, but nowadays living in Italy in adequate conditions. Mothers from Italy, Africa, Asia and Eastern European Countries were included in the study. Anti- E. coli s-IgA, IL-6, IL-8 and IL-10 were determined by ELISA. Breast milk of all the foreign mothers presented higher levels of E. coli s-IgA than Italians, and for Asian and African mothers were significative (p=0.031 and p=0.015, respectively). Milk from women of Eastern European Countries revealed the highest IL-8 levels (p=0.026), while milk from Asian women presented the greatest concentration of IL-6 (p=0.04); however, the Africans reported the lowest concentrations of IL-10 (p=0.045). Since all the mothers had been living in Italy for some time, we believe that the presence of high levels of E. coli s-IgA, supported by high levels of pro-inflammatory cytokine, is part of a persisting immunological secretory memory.

Factors of the lectin pathway of complement activation and their clinical associations in neonates

This paper summarizes the data concerning soluble defense lectins (mannan-binding lectin, M-ficolin, L-ficolin, and H-ficolin) with the unique ability to activate complement and their associated serine proteases (MASPs) in neonates. The clinical importance of deficiencies of these immune factors is presented in aspects of perinatal mortality, premature births, and low birthweight. Prenatal serum concentrations of L-ficolin, H-ficolin, and MASP-2 (and probably M-ficolin) correlate with gestational age and birthweight. The relationship of serum MBL to gestational age is controversial. The MBL2 genotypes XA/O and O/O (associated with low-serum MBL) are associated with perinatal infections, whereas the high serum MBL-conferring A/A genotypes may be associated with prematurity. Low-serum L-ficolin concentrations, but not low-serum H-ficolin concentrations, are also associated with perinatal infections. Much of the literature is inconsistent, and the relationships reported so far require independent confirmation at both gene and protein levels. Our preliminary conclusion is that these soluble defense lectins play a protective role in the neonate, and that insufficiency of such factors contributes to the adverse consequences of prematurity and low birthweight.

Recurrent infection in children: when and how to investigate for primary immunodeficiency?

While the impact of infectious diseases in developed countries has been diminished by improved nutrition, hygiene, vaccination coverage and health care, infections remain common, and even the healthiest children may suffer frequent infections, occasionally necessitating admission to hospital. When investigating a child with recurrent infections, it is therefore important to know the frequency, severity, infectious syndrome and infecting organisms which a normal child might experience, and to understand the impact of the child's underlying health on their susceptibility to infection. This paper examines infectious susceptibility in the healthy and immunocompromised child and explores the respective presentations of some primary immunodeficiencies.

Two factors of the lectin pathway of complement, l-ficolin and mannan-binding lectin, and their associations with prematurity, low birthweight and infections in a large cohort of Polish neonates

Ficolins and one collectin, mannan-binding lectin (MBL), are the only factors known to activate the lectin pathway (LP) of complement. There is considerable circumstantial evidence that MBL insufficiency can increase susceptibility to various infections and influence the course of several non-infectious diseases complicated by infections. Much less information is available concerning l-ficolin. We report the results of a prospective study to investigate any association between either MBL deficiency or l-ficolin deficiency with prematurity, low birthweight or perinatal infections in a large cohort of Polish neonates, representing an ethnically homogenous population (n=1832). Cord blood samples were analysed to determine mbl-2 gene variants, MBL concentrations and MBL-MASP-2 complex activities (MBL-dependent lectin pathway activity) as well as l-ficolin levels. Median concentrations of l-ficolin and MBL were 2500 and 1124 ng/ml, respectively, while median LP activity was 272 mU/ml. After genotyping, 60.6% of babies were mbl-2 A/A, 35.4% were A/O and 4% were O/O genotypes. We found relative l-ficolin deficiency to be associated with prematurity, low birthweight and infections. l-Ficolin concentration correlated with gestational age and with birthweight, independently of gestational age. Preterm deliveries (<38 weeks) occurred more frequently among neonates with low LP activity but not with those having low serum MBL levels. Similarly, no association of serum MBL deficiency with low birthweight was found, but there was a correlation between LP activity and birthweight. Genotypes conferring very low serum MBL concentrations were associated with perinatal infections, and high-MBL-conferring genotypes were associated with prematurity. Our findings suggest that l-ficolin participates in host defence during the perinatal period and constitute the first evidence that relative l-ficolin deficiency may contribute to the adverse consequences of prematurity. Some similar trends were found with facets of MBL deficiency, but the observed relationships were weaker and less consistent.

Outcome and prognostic factors in neonates with septic shock

OBJECTIVE

Few accurate data are available on the outcome of septic shock in the neonatal period. The objective was to describe outcome and to determine variables associated with death or adverse outcome in neonates with septic shock.

DESIGN

Retrospective cohort study.

SETTING

A tertiary neonatal intensive care unit in a university hospital.

PATIENTS

All patients admitted to the neonatal intensive care unit over a 6-yr period meeting the following criteria: hypotension and/or need for intravenous fluid administration or vasoactive drugs, in the presence of proven or highly probable infection.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Main outcomes were 28-day mortality and adverse outcome at 18 months of corrected age, defined as death or severe sequelae (cerebral palsy, severe developmental delay, hearing impairment, blindness, or short bowel syndrome). Forty-eight infants were included. Follow-up data at 18 months were obtained for 46 of 48 infants. The 28-day mortality was 40% (19 deaths). Adverse outcome at 18 months of corrected age was observed in 24 of 46 infants (52%; death = 19, severe sequelae = 5). Twenty-eight percent of the infants were alive and had a normal examination at 18 months. Infants with adverse outcome had significantly lower gestational age, birth weight, Apgar score, weight at onset of sepsis, and pH and more often had gram-negative infection, fetal growth restriction, hypoglycemia, and thrombocytopenia. Significant predictors (multivariate analysis) of 28-day mortality and of adverse outcome at 18 months of corrected age were weight (kg) at the onset of sepsis (odds ratio 0.14, 95% confidence interval 0.03-0.55; odds ratio 0.21, 95% confidence interval 0.06-0.74, respectively) and gram-negative infection (odds ratio 10.1, 95% confidence interval 1.5-65.7; odds ratio 45.5, 95% confidence interval 3-637, respectively).

CONCLUSIONS

Septic shock in the neonatal period has a very poor outcome. Data underscore the extreme vulnerability of very low birth weight infants to septic shock, particularly to gram-negative species.

Total hydroperoxide and biological antioxidant potentials in a neonatal sepsis model

Oxidant/antioxidant imbalance plays an important role in septic shock. The present study examined changes in circulating oxidative components in a neonatal sepsis model. Subjects were 14 newborn mixed-strain piglets randomly divided into two groups: a cecal ligation and perforation (CLP) model (n = 7) and sham (n = 7). Blood samples for total hydroperoxide (TH), biological antioxidant potential (BAP), tumor necrosis factor (TNF) alpha, interleukin (IL)-6, and IL-10 were collected pre-CLP and at 1, 3, and 6 h post-CLP. TH and BAP levels at 1 h post-CLP were significantly higher in the CLP group than in the sham group. In the CLP group, TH decreased gradually and reached baseline levels by 6 h post-CLP, while BAP remained elevated. Linear correlations were identified between serum TH and BAP at 1 h post-CLP, serum TH and TNF-alpha at 1 h post-CLP, and BAP and IL-6 at 6 h post-CLP. Changes in and correlations between circulating oxidative and inflammatory state components in a neonatal sepsis model were clarified. This is the first study to reveal that the presence of oxidant/antioxidant imbalance in sepsis and septic shock changes during the disease course.

Effect of hemoperfusion using polymyxin B-immobilized fiber on IL-6, HMGB-1, and IFN gamma in a neonatal sepsis model

To evaluate effects of polymyxin B direct hemoperfusion (PMX-DHP) on a neonatal sepsis cecal ligation and perforation (CLP) model, in 24 anesthetized and mechanically ventilated 3-d-old piglets, 16 were assigned to CLP and an arteriovenous extracorporeal circuit from 3 h until 6 h post-CLP, with a PMX-column in PMX-DHP-treated group (8 piglets) and 8 as sham. Plasma lipopolysaccharide (LPS) was measured at before CLP and at 3 and 9 h. Changes in mean systemic blood pressure (mSBP), mean pulmonary blood pressure, serum IL-6, tumor necrosis factor alpha, interferon gamma, and highly mobile group-1 box protein were measured before CLP and at 1, 3, 6, and 9 h. LPS was lower in the sham and PMX-DHP groups than in the control at 9 h. The mSBP was higher in the sham and PMX-DHP groups than in the control at both 6 h. IL-6 was lower in the sham and PMX-DHP groups than in the control at 6 h. HMGB-1 was lower in the PMX-DHP group than in the control at 6 h. IFN-gamma was only detected in the control group at 9 h. Survival times in the PMX-DHP group were longer than in the control. Thus, PMX-DHP improved septic shock in a neonatal septic model.

DEVELOPMENT AND CHARACTERIZATION OF A NOVEL PORCINE MODEL OF NEONATAL SEPSIS

Sepsis and its sequela remain a major source of morbidity and mortality in neonates despite advances in antimicrobials and aggressive supportive care. Many models of neonatal sepsis have been developed for investigating the pathophysiology of this disease and application of therapy, and a model with an infectious focus is closer to clinical reality. To establish an animal model that mimics the clinical characteristics of neonatal sepsis, the cecal devascularization and perforation procedure was implemented on 15 mixed-strain newborn piglets, which produced an infectious focus that acted as a continuous source of microorganisms to the peritoneal cavity. The mean survival time in animals with sepsis was 10.4 h (range 5.5-17.9 h), whereas all of the sham-operated control animals survived more than 24 h. Animals with sepsis showed a gradual significant decrease in the mean systemic blood pressure (mSBP; 71 +/- 3 mmHg in sepsis vs. 64 +/- 3 mmHg in control at 3 h, 38 +/- 7 mmHg in sepsis vs. 59 +/- 4 mmHg in control at 6 h, mean +/- SEM). They also showed an increase of serum levels of endotoxin (5.6 x 10 +/- 4.5 x 10 pg/mL in sepsis vs. 6.0 x 10 +/- 3.8 x 10 pg/mL in control at 6 h). Serum levels of TNF-alpha in the animals with sepsis became significantly higher than the control animals at 0 h (96 +/- 31 pg/mL in sepsis vs. 12 +/- 1 pg/mL in control) and remained significantly higher than all through the experiment. Serum levels of IL-6 in animals with sepsis showed a gradual increase (484 +/- 231 pg/mL in sepsis in its peak at 6 h vs. 24 +/- 5 pg/mL in control), however, there were no significant differences in serum IL-10 levels between the groups. Microorganisms detected in the blood of animals with sepsis were gram-negative enteric and anaerobic organisms. These results suggested that this model mimics the clinical state of neonatal sepsis and hence may have significant implications for the treatment of sepsis, including its use as a model in further investigations.

Two-color flow cytometric analysis of preterm and term newborn lymphocytes

Immune system maturation proceeds postnatally in humans. Therefore, newborns, especially those of a lower gestational age, are not fully immunocompetent and are more likely to acquire perinatal infections. In order to investigate the neonatal immune system status, the major lymphocyte subpopulations were studied in newborns of different gestational age, comparing term newborns and adults. The cord blood from 66 newborns and the peripheral blood from 23 adults were analyzed using fluorochrome labelled monoclonal antibodies and two-color flow cytometry. The newborns were divided into three groups according to their gestational age. Ten prematures were under 32 weeks of gestation, 35 were of 32-37 weeks and there were 21 term newborns. The percentage of cytotoxic T lymphocytes (CD4 CD8+) was lower in term newborns as compared to the adult controls (17.8 versus 30.3%), and so were the percentages of activated T lymphocytes (CD3+Ia+; 0.3 versus 3.7%), cytotoxic non-MHC restricted T lymphocytes (CD3+CD16+CD56+; 0.2 versus 1.8%) and NK cells (CD3-CD16+CD56+; 4.8 versus 15.5%). On the contrary, the proportions of unlabelled cells were increased in term cord blood. The expression of CD45R0 marker on neonatal lymphocytes was very low (1%). In comparison to the higher-gestation newborns, the lower gestation prematures had reduced percentages of T lymphocytes (CD3+; 43 versus 65%), mostly helper T lymphocytes (CD4+CD8-; 35 versus 50%), and increased percentages of unlabelled cells. The percentages of NK cells (CD3+CD16+CD56+) and B lymphocytes (CD3-CD19+; CD3-Ia+) did not differ among the tested newborn groups. There were no significant differences in major lymphocyte subpopulations between the group of highest-gestation prematures and the group of term newborns that differed significantly when compared to adults. The lowest-gestation newborns showed the most immature lymphocyte phenotype with the highest percentages of unlabelled cells.

Nursing the preterm surgical neonate

The preterm neonate's response to surgery manifests in all body systems. Necrotising Enterocolitis (NEC) is an acute gastro-intestinal emergency requiring surgical intervention. Severe NEC may require the removal of infarcted bowel. Examining the response to surgery in the preterm neonate with NEC offers nurses a rationale for their post-operative care. Both physiological and psychological responses need to be understood in the light of family centred care.

The development of the complement system after 28 weeks' gestation

OBJECTIVE

To assess the levels and development of the various complement components in preterm infants, particularly among those born before 34 weeks' gestation.

SUBJECTS AND METHODS

We measured the complement system's activities (CH50 and AP50) as well as its various components (C1q,r,s, C2-C9, Factor B, and properdin) in 25 preterm infants [gestational age (GA) 28-33 weeks], 35 preterm infants (GA 34-36 weeks), 50 full-term newborn infants (GA 37-42 weeks), and 49 healthy adults as control subjects.

RESULTS AND CONCLUSIONS

The results of these studies are: (i) complement levels and activity were significantly reduced in preterm and full-term neonates when compared with adult levels, with the exception of C7 which was within the normal range in most infants. C8 and C9 were the most markedly reduced at all gestational ages. (ii) Complement levels correlated significantly with gestational age, but not with birth-weight, type of delivery, or gender. (iii) Between 28 and 33 weeks' gestation, there appeared to be almost no development of the complement system.