Neonatal immunology

The immunogenetic basis of severe herpes simplex infections in neonates and children: a review

Human herpes simplex virus (HSV) is a double stranded DNA virus with two distinct types, HSV-1 and HSV-2. The global burden of HSV is high with an estimated 2/3 of the adult population seropositive for at least one of these types of HSV. HSV rarely causes life-threatening disease in immunocompetent children and adults. However, in neonates and children with a developmentally immature immune system it can cause disseminated disease and herpes simplex encephalitis (HSE). Recent studies in children and neonates suggest that genetic risk-factors can contribute to severe HSV phenotypes in neonates and children. In particular, genetic defects in the Toll Like Receptor 3 (TLR3) signaling pathway that attenuate the type I interferon response to HSV are being increasingly recognized in children with severe phenotypes of HSV. In this review, we discuss the epidemiology and immunological aspects of HSV disease in neonates and children and provide an in-depth review of the studies characterizing the role of inborn errors in the TLR3 pathway and other immune genes in HSV. We highlight the need for future research to identify the immunogenetic basis of severe or recurrent HSV disease in neonates and children. IMPACT: Review the epidemiology and phenotypes of herpes simplex virus (HSV) infection in neonates and children. Discuss the mechanisms of immunity against HSV highlighting the developmental vulnerability of neonates and infants to severe HSV disease. Explore in depth the genes and immune pathways that underlie genetic predisposition to severe HSV disease in neonates and children, and outline strategies for multi-disciplinary clinical evaluation of severe disease.

Risk Factors for Dehiscence of Operative Incisions in Newborns after Laparotomy

BACKGROUND

 Surgical wound dehiscence (SWD) in neonates is a life-threatening complication. The aim was to define risk factors of postoperative incision dehiscence in this population.

METHODS

 Data of 144 patients from 2010 to 2020 were analyzed retrospectively. All full-term newborns or preterm newborns up to 42 weeks of amenorrhea (adjusted) who had a laparotomy within 30 days were included. Descriptive patient information and perioperative data were collected. SWD was defined as any separation of cutaneous edges of postoperative wounds.

RESULTS

 Overall, SWD occurred in 16/144 (11%) patients, with a significantly increased incidence in preterm newborns (13/59, 22%) compared with full-term newborns (3/85, 4%; p < 0.001). SWD was significantly associated with exposure to postnatal steroids (60% vs. 4%, p < 0.001) and nonsteroidal anti-inflammatory drugs (25% vs. 4%, p < 0.01), invasive ventilation duration before surgery (median at 10 vs. 0 days, p < 0.001), preoperative low hemoglobin concentration (115 vs. 147 g/L, p < 0.001) and platelet counts (127 vs. 295 G/L, p < 0.001), nonabsorbable suture material (43% vs. 8%, p < 0.001), the presence of ostomies (69% vs. 18%, p < 0.001), positive bacteriological wound cultures (50% vs. 6%, p < 0.001), and relaparotomy (25% vs. 3%, p < 0.01). Thirteen of 16 patients with SWD presented necrotizing enterocolitis/intestinal perforations (81%, p < 0.001).

CONCLUSION

 This study identified prematurity and a number of other factors linked to the child's general condition as risk factors for SWD. Some of these can help physicians recognize and respond to at-risk patients and provide better counseling for parents.

Early Appearance of Functional Plasma Cells (CD138+CD98+) in Non-immunized Neonate Mice

Plasma cells (PCs) are terminally differentiated antibody-secreting cells, derived from activated B-lymphocytes in response to either T-independent or T-dependent antigens. The plasma cell population is scarce in circulation in non-immunized individuals. It is established that neonates are incapable of mounting an efficient immune response due to the immaturity of the immune system. However, this disadvantage is well overcome through the antibodies neonates receive from breastmilk. This implies that neonates will be only protected against antigens the mother had previously encountered. Thus, the child might be potentially susceptible to new antigens. This issue prompted us to seek for the presence of PCs in non-immunized neonate mice. We found a PC population identified as CD138+/CD98+ cells since day one after birth. These PCs were positive for Ki67 and expressed Blimp-1, B220, and CD19, which suggests the populations are plasmablasts and PCs with heterogeneous phenotype. These PCs were also determined to secrete antibodies, although mainly isotype IgM. Altogether, the results indicated that neonate PCs can produce antibodies against antigens they encounter in the first weeks of life, most likely coming from food, colonizing microbiota, or the environment.

External Validation of a Vancomycin Population Pharmacokinetic Model and Developing a New Dosage Regimen in Neonates

BACKGROUND AND OBJECTIVE

Vancomycin is the drug of choice in the treatment of MRSA infections. In a published vancomycin population pharmacokinetic study on neonates in Singapore healthcare institutions, it was found that vancomycin clearance was predicted by weight, postmenstrual age, and serum creatinine. The aim of this study was to externally validate the vancomycin population pharmacokinetic model to develop a new dosage regimen in neonates, and to compare this regimen with the existing institutional and NeoFax^® dosage regimens.

METHODS

A retrospective chart review of neonates who received vancomycin therapy and therapeutic drug monitoring was conducted. The median prediction error percentage was calculated to assess bias, while the median absolute prediction error percentage and the root mean squared error percentage were calculated to assess precision. The new dosage regimen was developed using Monte Carlo simulation.

RESULTS

A total of 20 neonates were included in the external validation dataset. Eighteen of them were premature, with a median gestational age of 27.7 (25.9-31.5) weeks and postmenstrual age of 30.5 (27.3-34.3) weeks at the point of vancomycin initiation. No apparent systematic bias was found in the predictions of the model. The external validation performed in the current study found the model to be generally unbiased. Our new vancomycin dosage regimen was able to achieve target trough concentrations and area under the curve (AUC₂₄) at a greater proportion as compared to existing institutional and NeoFax^® dosage regimens.

CONCLUSION

The pharmacokinetic model built in the previous study can be used to conduct reliable population simulations of our Asian neonatal population in Singapore. The new dosage regimen was able to achieve target trough concentrations and AUC₂₄ better than existing institutional and NeoFax^® dosage regimens.

Human Breast Milk: From Food to Active Immune Response With Disease Protection in Infants and Mothers

Breastfeeding is associated with long-term wellbeing including low risks of infectious diseases and non-communicable diseases such as asthma, cancer, autoimmune diseases and obesity during childhood. In recent years, important advances have been made in understanding the human breast milk (HBM) composition. Breast milk components such as, non-immune and immune cells and bioactive molecules, namely, cytokines/chemokines, lipids, hormones, and enzymes reportedly play many roles in breastfed newborns and in mothers, by diseases protection and shaping the immune system of the newborn. Bioactive components in HBM are also involved in tolerance and appropriate inflammatory response of breastfed infants if necessary. This review summarizes the current literature on the relationship between mother and her infant through breast milk with regard to disease protection. We will shed some light on the mechanisms underlying the roles of breast milk components in the maintenance of health of both child and mother.

Diagnosis and Surveillance of Neonatal Infections by Metagenomic Next-Generation Sequencing

Microbial infections cause significant morbidity and mortality in neonates. Metagenomic next-generation sequencing is a hypothesis-free and culture-free test that enables broad identification of pathogens and antimicrobial resistance genes directly from clinical samples within 24 h. In this study, we used mNGS for etiological diagnosis and monitoring the efficacy of antibiotic treatment in a cohort of neonatal patients with severe infections. The median age was 19.5 (3–52) days, median gestational age was 37.96 (31–40⁺³) weeks, and the median birth weight was 3,261 (1,300–4,300) g. The types of infectious diseases included pneumonia, sepsis, and meningitis. mNGS reported microbial findings in all cases, which led to changes in antibiotic treatment. These included cases of Mycobacterium tuberculosis, Legionella pneumophila, and Bacillus cereus. Eight of ten infants recovered after antibiotic adjustment and showed normal development during follow-up. On the other hand, neurological retardation was seen in two infants with meningitis. mNGS enabled etiological diagnosis and guided antibiotic therapy when all conventional methods failed to discover the culprit. It has the potential to cut down the overall cost and burden of disease management in neonatal infections.

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.

Recurrent neonatal sepsis and progressive white matter injury in a premature newborn culture-positive for group B Streptococcus: A case report

RATIONALE

Group B Streptococcus (GBS) remains a principal pathogen causing neonatal sepsis and meningitis, particularly in premature infants with relatively insufficient immunity. Recurrence may occur uncommonly, largely associated with subclinical mucosal persistence or repetitive exposure to exogenous sources. White matter injury (WMI) including cystic periventricular leukomalacia (PVL) has been associated with intrauterine infection/inflammation, and neonatal infection as a more significant predictor including postnatal sepsis and recurrent infection, even without microbial neuroinvasion. Furthermore, clinical and experimental evidence of WMI by some bacteria other than GBS without central nervous system invasion has been reported. However, there is little evidence of WMI associated with neonatal GBS sepsis in the absence of meningitis in the literature.

PATIENT CONCERNS

A newborn at 30+4 weeks' gestation with low birthweight presented with 2 episodes (with a 13-day interval with no antibiotic therapy) of neonatal sepsis culture-proven for GBS with early-onset presentation after clinical chorioamnionitis via vertical GBS transmission and the associated conditions including prematurity-related neonatal immunodeficiency and persistent mucosal GBS carriage after the first antibiotic treatment. The perinatal GBS infection was complicated by progressive WMI presenting with ventriculomegaly and cystic PVL without a definite evidence of meningitis, intraventricular hemorrhage, and documented cerebral hypoxia or hypoperfusion conditions including septic shock.

DIAGNOSES

Recurrent group B streptococcal sepsis and cystic PVL with ventriculomegaly.

INTERVENTIONS

Two episodes of GBS sepsis were treated with 15-day parenteral antibiotic therapy, respectively.

OUTCOMES

Resolution of the recurrent GBS sepsis without further relapses, however, complicated by WMI and subsequent about 6 months delay in motor development at 12 months' corrected age.

LESSONS

This case suggests WMI associated with GBS bacteremia without central nervous system entry by viable GBS and also shows that in premature infants, intrauterine GBS infection with no interventions may lead to extensive and persistent GBS colonization, early-onset and recurrent GBS disease, and WMI. Postnatal as well as intrauterine infection/inflammation controls with maternal prophylaxis may be pivotal for prevention and limiting the magnitude of neurologic injury.

Cancer progression as a sequence of atavistic reversions

It has long been recognized that cancer onset and progression represent a type of reversion to an ancestral quasi-unicellular phenotype. This general concept has been refined into the atavistic model of cancer that attempts to provide a quantitative analysis and testable predictions based on genomic data. Over the past decade, support for the multicellular-to-unicellular reversion predicted by the atavism model has come from phylostratigraphy. Here, we propose that cancer onset and progression involve more than a one-off multicellular-to-unicellular reversion, and are better described as a series of reversionary transitions. We make new predictions based on the chronology of the unicellular-eukaryote-to-multicellular-eukaryote transition. We also make new predictions based on three other evolutionary transitions that occurred in our lineage: eukaryogenesis, oxidative phosphorylation and the transition to adaptive immunity. We propose several modifications to current phylostratigraphy to improve age resolution to test these predictions. Also see the video abstract here: https://youtu.be/3unEu5JYJrQ.

Achieving Vancomycin Troughs Within Goal Range in Low Birth Weight Neonates

OBJECTIVE

Vancomycin is commonly used in the neonatal population to treat Gram-positive bacterial infections. Despite frequent use, consensus on the ideal dosing regimen in low birth weight (LBW) neonates is lacking. The objective of this research is to determine how frequently vancomycin troughs within goal range (10-20 mg/L) are achieved with empiric dosing in critically ill neonates and infants weighing less than 2500 g.

METHODS

This retrospective review evaluated LBW infants who were admitted to a level IV NICU from January 2015 to December 2016. Patients were included if they had a vancomycin trough sample collected at steady state (after at least 3 doses). Three trough cohorts (subtherapeutic: <10 mg/L, therapeutic: 10-20 mg/L, and supratherapeutic: >20 mg/L) were compared with 1-way ANOVA for continuous data and a chi-square analysis for categorical data.

RESULTS

A total of 74 patients were included, with a mean birth weight (BW) of 819.7 ± 355.4 g and a mean gestational age (GA) of 26.4 ± 3.7 weeks. Only 27 patients (36.5%) had therapeutic vancomycin trough concentrations. Subtherapeutic troughs were recorded in 40 patients (54.1%), while supratherapeutic troughs were recorded in 7 patients (9.5%). Although there was no difference between the initial dose, initial frequency was significantly different between cohorts (p = 0.04).

CONCLUSION

Empiric dosing regimens do not produce vancomycin troughs within the goal range in most LBW patients.

The Multiple Functions of B Cells in Chronic HBV Infection

Chronic hepatitis B virus (HBV) infection is one of the main causes of liver diseases, of which the natural history and clinical outcomes are associated with the role of B cells. As humoral immune cells, B cells play a critical role in the process of anti-HBV antibody production. In addition, some studies have also characterized other B cell subsets involved in antigen presentation and regulating the immune response beyond antibody secretion. However, not all B cell subsets play a positive role in the immune response to chronic HBV infection, and various B cell subsets jointly mediate persistent HBV infection, tolerance, and liver damage. Thus, we further sought to elucidate the multiple functions of B cells to gain novel insight into the understanding of chronic hepatitis B (CHB) pathogenesis. We also reviewed the current immunotherapies targeting B cells to explore novel therapeutic interventions for the treatment of chronic HBV infection.

Precision immunization: a new trend in human vaccination

Vaccination has been one of the major revolutions in the history of human health. Vaccination programs have targeted entire populations such as infants or elderly subjects as a matter of being efficient with time and resources. These general populations are heterogeneous in terms of factors such as ethnicity, health status, and socio-economics. Thus, there have been variations in the safety and effectiveness profiles of certain vaccinations according to current population-wide strategies. As the concept of precision medicine has been raised in recent years, many researchers have suggested that vaccines could be administered more precisely in terms of particular target populations, vaccine formulations, regimens, and dosage levels. This review addresses the concept and framework of precision immunization, summarizes recent and representative clinical trials of among specific populations, mentions important factors to be addressed in customizing vaccinations, and provides suggestions on the establishment of precision immunization with the goal of maximizing the effectiveness of vaccines in general.

Impact of vaccination during pregnancy and staphylococci concentration on the presence of Bacillus cereus in raw human milk

OBJECTIVE

This study aimed to determine whether vaccination during pregnancy, prematurity, and staphylococci concentration influenced the presence of B. cereus or staphylococcal enterotoxins (SEs) in raw human milk from healthy mothers.

STUDY DESIGN

Human milk samples were collected from 152 healthy women. B. cereus, S. aureus and coagulase-negative staphylococci (CNS) were enumerated using selective agar culture media. The detection of B. cereus spores and SEs were determined using ELISA.

RESULTS

CNS and B. cereus concentrations in milk from non-vaccinated mothers were higher than that from mothers vaccinated during pregnancy, but S. aureus did not differ. Prematurity did not affect B. cereus or staphylococci in human milk. S. aureus and CNS concentrations in human milk with the presence of B. cereus were higher than that with the absence of B. cereus. Viable B. cereus was present in 9.2% of raw human milk samples whereas SEs were not detected in any samples.

CONCLUSIONS

Vaccination during pregnancy and low concentration of staphylococci could reduce the risk of B. cereus in raw human milk. The screening of B. cereus in raw human milk must be performed before pasteurization to reduce the risk of B. cereus infection in preterm infants.

Early antiretroviral therapy in neonates with HIV-1 infection restricts viral reservoir size and induces a distinct innate immune profile

Neonatal HIV-1 infection is associated with rapidly progressive and frequently fatal immune deficiency if left untreated. Immediate institution of antiretroviral therapy (ART), ideally within hours after birth, may restrict irreversible damage to the developing neonatal immune system and possibly provide opportunities for facilitating drug-free viral control during subsequent treatment interruptions. However, the virological and immunological effects of ART initiation within hours after delivery have not been systematically investigated. We examined a unique cohort of neonates with HIV-1 infection from Botswana who started ART shortly after birth and were followed longitudinally for about 2 years in comparison to control infants started on treatment during the first year after birth. We demonstrate multiple clear benefits of rapid antiretroviral initiation, including an extremely small reservoir of intact proviral sequences, a reduction in abnormal T cell immune activation, a more polyfunctional HIV-1-specific T cell response, and an innate immune profile that displays distinct features of improved antiviral activity and is associated with intact proviral reservoir size. Together, these data offer rare insight into the evolutionary dynamics of viral reservoir establishment in neonates and provide strong empirical evidence supporting the immediate initiation of ART for neonates with HIV-1 infection.

Leptin and adiponectin supplementation modifies mesenteric lymph node lymphocyte composition and functionality in suckling rats

At birth, when immune responses are insufficient, there begins the development of the defence capability against pathogens. Leptin and adiponectin, adipokines that are present in breast milk, have been shown to play a role in the regulation of immune responses. We report here, for the first time, the influence of in vivo adipokine supplementation on the intestinal immune system in early life. Suckling Wistar rats were daily supplemented with leptin (0·7 μg/kg per d, n 36) or adiponectin (35 μg/kg per d, n 36) during the suckling period. The lymphocyte composition, proliferation and cytokine secretion from mesenteric lymph node lymphocytes (on days 14 and 21), as well as intestinal IgA and IgM concentration (day 21), were evaluated. At day 14, leptin supplementation significantly increased the TCRαβ + cell proportion in mesenteric lymph nodes, in particular owing to an increase in the TCRαβ + CD8+ cell population. Moreover, the leptin or adiponectin supplementation promoted the early development CD8+ cells, with adiponectin being the only adipokine capable of enhancing the lymphoproliferative ability at the end of the suckling period. Although leptin decreased intestinal IgA concentration, it had a trophic effect on the intestine in early life. Supplementation of both adipokines modulated the cytokine profile during (day 14) and at the end (day 21) of the suckling period. These results suggest that leptin and adiponectin during suckling play a role in the development of mucosal immunity in early life.

Enhancement of immune maturation in suckling rats by leptin and adiponectin supplementation

Leptin and adiponectin, adipokines present in breast milk, have shown immunomodulatory properties. The current study aimed to ascertain whether a nutritional supplementation with leptin or adiponectin in neonatal rats was able to influence the maturation of the systemic immune response in early life. To achieve this, suckling Wistar rats were supplemented with either leptin (0.7 μg/kg/day) or adiponectin (35 μg/kg/day) during the whole suckling period. Plasmatic immunoglobulins were quantified, and spleen lymphocyte composition and their ability to proliferate and release cytokines were evaluated during (day 14) and at the end (day 21) of the suckling period. Rats fed with either adipokine showed higher plasma IgM and IgG1 concentrations and adiponectin supplementation also increased IgG2a at both studied days (P < 0.05). With regard to the lymphocyte composition, both adipokine supplementations increased T cell proportion and both CD4⁺ and CD8⁺ T cell subsets after two weeks of supplementation (P < 0.05). Moreover, only leptin administration increased NK and NKT cell proportions at the end of the suckling period. Finally, both adipokines influenced the cytokine secretion pattern by splenocytes. In conclusion, these results suggest that leptin and adiponectin play a role in the maturation of the systemic immune response during the suckling period.

Anti-bacterial Monoclonal Antibodies

The failing efficacy of antibiotics and the high mortality rate among high-risk patients calls for new treatment modalities for bacterial infections. Due to the vastly divergent pathogenesis of human pathogens, each microbe requires a tailored approach. The main modes of action of anti-bacterial antibodies are virulence factor neutralization, complement-mediated bacterial lysis and enhancement of opsonophagocytic uptake and killing (OPK). Gram-positive bacteria cannot be lysed by complement and their pathogenesis often involves secreted toxins, therefore typically toxin-neutralization and OPK activity are required to prevent and ameliorate disease. In fact, the success stories in terms of approved products, in the anti-bacterial mAb field are based on toxin neutralization (Bacillus anthracis, Clostridium difficile). In contrast, Gram-negative bacteria are vulnerable to antibody-dependent complement-mediated lysis, while their pathogenesis rarely relies on secreted exotoxins, and involves the pro-inflammatory endotoxin (lipopolysaccharide). Given the complexity of bacterial pathogenesis, antibody therapeutics are expected to be most efficient upon targeting more than one virulence factor and/or combining different modes of action. The improved understanding of bacterial pathogenesis combined with the versatility and maturity of antibody discovery technologies available today are pivotal for the design of novel anti-bacterial therapeutics. The intensified research generating promising proof-of-concept data, and the increasing number of clinical programs with anti-bacterial mAbs, indicate that the field is ready to fulfill its promise in the coming years.

Nosocomial outbreak of Candida parapsilosis sensu stricto fungaemia in a neonatal intensive care unit in China

BACKGROUND

Candida parapsilosis is a common agent of fungaemia, but few outbreaks of Candida parapsilosis infection have been reported in China.

AIM

To elaborate an outbreak of nosocomial Candida parapsilosis sensu stricto fungaemia in a neonatal intensive care unit (NICU) of a comprehensive hospital in China from July to October 2017.

METHODS

Epidemics and characteristics of fungaemia cases were investigated. Surveillance samples were collected. Vitek 2 Compact System, internal transcribed spacer sequencing, and random amplified polymorphic DNA (RAPD) typing were conducted to identify the isolates. Antifungal susceptibility test was performed for all bloodstream isolates.

FINDINGS

Sixteen neonates were diagnosed as Candida parapsilosis sensu stricto fungaemia during this period. Presenting symptoms included leucopenia, thrombocytopenia, and respiratory crackles. Fifteen cases were cured whereas one case who suffered from severe concomitant diseases died. The isolates were susceptible to fluconazole, amphotericin B, itraconazole, voriconazole, and 5-fluorocytosine. A total of 313 surveillance samples were collected, and Candida parapsilosis sensu stricto was identified from 16 environmental samples and one sample from an ultrasonographer's hand. The colonized locations included wiping cloths, faucets, sinks, operating table, puddles in the bathroom, a ventilator, and an ultrasonic probe. The RAPD patterns of all the Candida parapsilosis sensu stricto isolates from bloodstream and surveillance samples were identical. The outbreak was controlled after a series of infection control measures.

CONCLUSION

Contaminated environment was associated with this outbreak. Close attention to immunocompromised patients, thorough environmental disinfection and hand hygiene should be strengthened in NICU.

A critical assessment of the "sterile womb" and "in utero colonization" hypotheses: implications for research on the pioneer infant microbiome

After more than a century of active research, the notion that the human fetal environment is sterile and that the neonate's microbiome is acquired during and after birth was an accepted dogma. However, recent studies using molecular techniques suggest bacterial communities in the placenta, amniotic fluid, and meconium from healthy pregnancies. These findings have led many scientists to challenge the "sterile womb paradigm" and propose that microbiome acquisition instead begins in utero, an idea that would fundamentally change our understanding of gut microbiota acquisition and its role in human development. In this review, we provide a critical assessment of the evidence supporting these two opposing hypotheses, specifically as it relates to (i) anatomical, immunological, and physiological characteristics of the placenta and fetus; (ii) the research methods currently used to study microbial populations in the intrauterine environment; (iii) the fecal microbiome during the first days of life; and (iv) the generation of axenic animals and humans. Based on this analysis, we argue that the evidence in support of the "in utero colonization hypothesis" is extremely weak as it is founded almost entirely on studies that (i) used molecular approaches with an insufficient detection limit to study "low-biomass" microbial populations, (ii) lacked appropriate controls for contamination, and (iii) failed to provide evidence of bacterial viability. Most importantly, the ability to reliably derive axenic animals via cesarean sections strongly supports sterility of the fetal environment in mammals. We conclude that current scientific evidence does not support the existence of microbiomes within the healthy fetal milieu, which has implications for the development of clinical practices that prevent microbiome perturbations after birth and the establishment of future research priorities.

The Importance of Human Milk for Immunity in Preterm Infants

The immune system of preterm infants is immature, placing them at increased risk for serious immune-related complications. Human milk provides a variety of immune protective and immune maturation factors that are beneficial to the preterm infant's poorly developed immune system. The most studied immune components in human milk include antimicrobial proteins, maternal leukocytes, immunoglobulins, cytokines and chemokines, oligosaccharides, gangliosides, nucleotides, and long-chain polyunsaturated fatty acids. There is growing evidence that these components contribute to the lower incidence of immune-related conditions in the preterm infant. Therefore, provision of these components in human milk, donor milk, or formula may provide immunologic benefits.

Pattern of Infectious Morbidity in HIV-Exposed Uninfected Infants and Children

Background

Almost 30% of children in Southern Africa are HIV exposed but uninfected (HEU) and experience exposures that could increase vulnerability to infectious diseases compared to HIV unexposed (HU) children. The mechanisms of HEU infant vulnerability remain ill-defined. This review seeks to appraise the existing clinical evidence of the pattern of HEU infant infectious morbidity to aid understanding of the potential mechanism of susceptibility.

Methods

A systematic search was conducted of scientific literature databases and conference proceedings up to December 2015 for studies comparing adequately defined HEU (in whom HIV-infection had been excluded through age-appropriate testing) and HU infants for all-cause mortality, all-cause hospitalization, or an infection-related morbidity. The systematic review was complemented by a narrative review of additional studies detailing the pattern of infectious morbidity experienced by HEU children without comparison to HU children or without conclusive exclusion of HIV-infection in HIV-exposed infants.

Results

Only 3 of 22 eligible identified studies were designed to primarily compare HEU and HU infants for infectious morbidity. Fourteen were conducted prior to 2009 in the context of limited antiretroviral interventions. Three patterns emerge: (1) causes of morbidity and mortality in HEU infants are consistent with the common causes of childhood morbidity and mortality (pneumonia, diarrheal disease, and bacterial sepsis) but occur with greater severity in HEU infants resulting in higher mortality, more frequent hospitalization, and more severe manifestations of disease; (2) the greatest relative difference between HEU and HU infants in morbidity and mortality occurs beyond the neonatal period, during mid-infancy, having waned by the second year of life; and (3) HEU infants are at greater risk than HU infants for invasive streptococcal infections specifically Group B Streptococcus and Streptococcus pneumonia.

Conclusion

To definitively understand HEU infant infectious morbidity risk, substantially larger prospective studies with appropriate HU infant comparison groups are necessary. HEU children would benefit from collaboration among researchers to achieve the quality of evidence required to improve HEU infant outcomes globally. HEU infant health and well-being, beyond avoiding HIV-infection, deserves a more prominent position in the local and international HIV research agendas.

Lactobacillus Sepsis and Probiotic Therapy in Newborns: Two New Cases and Literature Review

Many term and preterm infants are commonly supplemented with probiotics to prevent adverse effects of antibiotic administration and necrotizing enterocolitis and they are believed to be safe. However, the supplementation with Lactobacillus rhamnosus GG has been associated with the development of sepsis with a cause-effect relationship in six newborns and children. In this study, we report two further cases and discuss the emerging issue of probiotic supplementation safety in neonates. We conclude that physicians must be aware that supplementation with L. rhamnosus GG can cause sepsis in high-risk patients on rare occasions.

Oral cyclosporine A in neonatal swines for transplantation studies

The purpose of this study is to define the optimal dose of oral cyclosporine A (CsA) microemulsion in newborn swine for transplantation studies and to describe its pharmacokinetics and acute renal effects in short-term administration. Thirteen neonatal pigs were randomized into four groups: one control and three groups with CsA administration at 4, 8 and 12 mg/kg/d for 15 days (D). Blood samples were collected on D 0, 2, 4, 9 and 14 to determine the changes of the CsA trough concentrations, the creatinine (Cr) and blood urea nitrogen (BUN) serum concentrations. On D 14, blood samples were collected every hour from 1 h to 10 h after CsA administration to determine the area under the curve (AUC). On D 15, kidneys were removed for histological analysis. We observed a stabilization of CsA trough concentrations from D 4 to D 14. On D 14, in the three treated groups, CsA trough concentrations were 687 ± 7, 1200 ± 77 and 2211 ± 1030 ng/ml, respectively; AUC (0-10 h) were 6721 ± 51 ng·h/ml in group 4 mg/kg/d, 13431 ± 988 ng·h/ml in group 8 mg/kg/d and 28264 ± 9430 ng·h/ml in group 12 mg/kg/d. Cr concentrations were not significantly different among the four groups; but compared to control group, BUN concentrations of the three treated groups increased significantly. CsA was well tolerated; neither acute, severe adverse event nor renal histological abnormality was observed. In conclusion, a 15-d course of oral CsA treatment ranged from 4 to 12 mg/kg/d is safe for newborn pigs, which need much lower CsA dose than adult pigs to reach comparable trough level and AUC. As immunosuppressive therapy in newborn pigs, we recommend a CsA dose of 4 mg/kg/d to achieve a trough blood concentration between 400 and 800 ng/ml.

The equine immune responses to infectious and allergic disease: a model for humans?

The modern horse, Equus caballus has historically made important contributions to the field of immunology, dating back to Emil von Behring's description of curative antibodies in equine serum over a century ago. While the horse continues to play an important role in human serotherapy, the mouse has replaced the horse as the predominant experimental animal in immunology research. Nevertheless, continuing efforts have led to an improved understanding of the equine immune response in a variety of infectious and non-infectious diseases. Based on this information, we can begin to identify specific situations where the horse may provide a unique immunological model for certain human diseases.

A review of the innate immune defence of the human foetus and newborn, with the emphasis on antimicrobial peptides

At birth, the foetus makes the transition from the uterus to a world full of microbes. The newborn baby needs protection against potential invading pathogens and needs to establish a normal microbiota.

CONCLUSION

Antimicrobial peptides and proteins are key effector molecules of innate immunity and are also important immunomodulators. Their presence in the cells and tissues of the uterus, foetus and the neonate indicates an important role in immunity during pregnancy and in early life.

Elucidation of pathways driving asthma pathogenesis: development of a systems-level analytic strategy

Asthma is a genetically complex, chronic lung disease defined clinically as episodic airflow limitation and breathlessness that is at least partially reversible, either spontaneously or in response to therapy. Whereas asthma was rare in the late 1800s and early 1900s, the marked increase in its incidence and prevalence since the 1960s points to substantial gene × environment interactions occurring over a period of years, but these interactions are very poorly understood (1-6). It is widely believed that the majority of asthma begins during childhood and manifests first as intermittent wheeze. However, wheeze is also very common in infancy and only a subset of wheezy children progress to persistent asthma for reasons that are largely obscure. Here, we review the current literature regarding causal pathways leading to early asthma development and chronicity. Given the complex interactions of many risk factors over time eventually leading to apparently multiple asthma phenotypes, we suggest that deeply phenotyped cohort studies combined with sophisticated network models will be required to derive the next generation of biological and clinical insights in asthma pathogenesis.

Restoration of MBL-deficiency: redefining the safety, efficacy and viability of MBL-substitution therapy

MBL-deficiency is a commonly occurring deficiency of the innate immune system, affecting a substantial part of the population and has been extensively studied. MBL appears to function as a disease modifier. The role of MBL in different conditions is context-dependent. Many clinical studies show conflicting results, which can be partially explained by different definitions of MBL-deficiency, including phenotype- and genotype-based approaches. In this review we give an overview of literature of MBL, its role in different pathologies, diseases and patient populations. We review MBL replacement studies, and discuss the potential of MBL substitution therapy. We finally suggest that new MBL substitution trials should be conducted within a predefined patient population. MBL-deficiency should be based on serum levels and confirmed by genotyping.

T-cell subpopulations αβ and γδ in cord blood of very preterm infants: the influence of intrauterine infection

Preterm infants are very susceptible to infections. Immune response mechanisms in this group of patients and factors that influence cord blood mononuclear cell populations remain poorly understood and are considered insufficient. However, competent immune functions of the cord blood mononuclear cells are also described. The aim of this work was to evaluate the T-cell population (CD3⁺) with its subpopulations bearing T-cell receptor (TCR) αβ or TCR γδ in the cord blood of preterm infants born before 32 weeks of gestation by mothers with or without an intrauterine infection. Being a pilot study, it also aimed at feasibility check and assessment of an expected effect size. The cord blood samples of 46 infants age were subjected to direct immunofluorescent staining with monoclonal antibodies and then analyzed by flow cytometry. The percentage of CD3⁺ cells in neonates born by mothers with diagnosis of intrauterine infection was significantly lower than in neonates born by mothers without infection (p = 0.005; Mann–Whitney U test). The number of cells did not differ between groups. Infection present in the mother did not have an influence on the TCR αβ or TCR γδ subpopulations. Our study contributes to a better understanding of preterm infants’ immune mechanisms, and sets the stage for further investigations.

Genome-wide study of association and interaction with maternal cytomegalovirus infection suggests new schizophrenia loci

Genetic and environmental components as well as their interaction contribute to the risk of schizophrenia, making it highly relevant to include environmental factors in genetic studies of schizophrenia. This study comprises genome-wide association (GWA) and follow-up analyses of all individuals born in Denmark since 1981 and diagnosed with schizophrenia as well as controls from the same birth cohort. Furthermore, we present the first genome-wide interaction survey of single nucleotide polymorphisms (SNPs) and maternal cytomegalovirus (CMV) infection. The GWA analysis included 888 cases and 882 controls, and the follow-up investigation of the top GWA results was performed in independent Danish (1396 cases and 1803 controls) and German-Dutch (1169 cases, 3714 controls) samples. The SNPs most strongly associated in the single-marker analysis of the combined Danish samples were rs4757144 in ARNTL (P=3.78 × 10(-6)) and rs8057927 in CDH13 (P=1.39 × 10(-5)). Both genes have previously been linked to schizophrenia or other psychiatric disorders. The strongest associated SNP in the combined analysis, including Danish and German-Dutch samples, was rs12922317 in RUNDC2A (P=9.04 × 10(-7)). A region-based analysis summarizing independent signals in segments of 100 kb identified a new region-based genome-wide significant locus overlapping the gene ZEB1 (P=7.0 × 10(-7)). This signal was replicated in the follow-up analysis (P=2.3 × 10(-2)). Significant interaction with maternal CMV infection was found for rs7902091 (P(SNP × CMV)=7.3 × 10(-7)) in CTNNA3, a gene not previously implicated in schizophrenia, stressing the importance of including environmental factors in genetic studies.

Humanized mice, a new model to study the influence of drug treatment on neonatal sepsis

Bacterial infection with group B Streptococcus (GBS) represents a prominent threat to neonates and fetuses in the Western world, causing severe organ damage and even death. To improve current therapeutic strategies and to investigate new approaches, an appropriate in vivo model to study the immune response of a human immune system is needed. Therefore, we introduced humanized mice as a new model for GBS-induced sepsis. Humanized mice feature deficiencies similar to those found in neonates, such as lower immunoglobulin levels and myeloid cell dysfunction. Due to the husbandry in specific-pathogen-free (SPF) facilities, the human immune cells in these mice also exhibit a naive phenotype which mimics the conditions in fetuses/neonates. Following infection, cytokine release and leukocyte trafficking from the bone marrow to the lymphoid organ (spleen) and into the peritoneum (site of infection) as well as bacterial spreading and clearance were traceable in the humanized mice. Furthermore, we investigated the effects of betamethasone and indomethacin treatment using this novel sepsis model. Although both drugs are commonly used in perinatal care, little is known about their effects on the neonatal immune system. Treatment of infected humanized mice not only induced the reduction of human leukocytes in the spleen but also increased the bacterial load in all analyzed organs, including the brain, which did not show infiltration of live GBS in untreated controls. These studies demonstrate the utility of the humanized mice as a new model to study an immature human immune response during bacterial infection and allow the investigation of side effects induced by various treatments.

Lactose in human breast milk an inducer of innate immunity with implications for a role in intestinal homeostasis

Postpartum, infants have not yet established a fully functional adaptive immune system and are at risk of acquiring infections. Hence, newborns are dependent on the innate immune system with its antimicrobial peptides (AMPs) and proteins expressed at epithelial surfaces. Several factors in breast milk are known to confer immune protection, but which the decisive factors are and through which manner they work is unknown. Here, we isolated an AMP-inducing factor from human milk and identified it by electrospray mass spectrometry and NMR to be lactose. It induces the gene (CAMP) that encodes the only human cathelicidin LL-37 in colonic epithelial cells in a dose- and time-dependent manner. The induction was suppressed by two different p38 antagonists, indicating an effect via the p38-dependent pathway. Lactose also induced CAMP in the colonic epithelial cell line T84 and in THP-1 monocytes and macrophages. It further exhibited a synergistic effect with butyrate and phenylbutyrate on CAMP induction. Together, these results suggest an additional function of lactose in innate immunity by upregulating gastrointestinal AMPs that may lead to protection of the neonatal gut against pathogens and regulation of the microbiota of the infant.

Human β-defensin 2 expression in ELBW infants with severe necrotizing enterocolitis

BACKGROUND

The aim of this study was to analyze whether the mucosal innate immune response of extremely-low-birth-weight (ELBW) infants might play a role in the development of necrotizing enterocolitis (NEC).

METHODS

Between April 2008 and December 2009 antimicrobial peptides were prospectively measured in fecal samples of ELBW infants. In cases requiring abdominal surgery, full-thickness gut biopsies were analyzed for expression of human β-defensin 2 (hBD2), interleukin-8 (IL-8), villin, MD2, and Toll-like receptor 4 (TLR4).

RESULTS

Fecal hBD1 concentrations were consistently low in all patients, whereas hBD2 concentrations were high in meconium, particularly in clinical chorioamnionitis, and then dropped, followed by a steady increase after day 14. Infants with moderate NEC showed significantly increased fecal hBD2 concentrations before clinical symptoms, in contrast to infants developing severe NEC. Analysis of intestinal resection material obtained from patients with severe NEC revealed low hBD2 mRNA and protein levels, and increased expression of the inflammatory cytokine IL-8.

CONCLUSION

High hBD2 concentrations, reflecting strong intestinal immune responses, were associated with moderate courses of the disease. In severe NEC, low hBD2 expression was accompanied by low TLR4/MD2 expression, suggesting an inadequate response to luminal bacteria, possibly predisposing those infants to the development of NEC.

Clinical pharmacokinetics of vancomycin in the neonate: a review

Neonatal sepsis is common and is a major cause of morbidity and mortality. Vancomycin is the preferred treatment of several neonatal staphylococcal infections. The aim of this study was to review published data on vancomycin pharmacokinetics in neonates and to provide a critical analysis of the literature. A bibliographic search was performed using PubMed and Embase, and articles with a publication date of August 2011 or earlier were included in the analysis. Vancomycin pharmacokinetic estimates, which are different in neonates compared with adults, also exhibit extensive inter-neonatal variability. In neonates, several vancomycin dosing schedules have been proposed, mainly based on age (i.e., postmenstrual and postnatal), body weight or serum creatinine level. Other covariates [e.g., extracorporeal membrane oxygenation (ECMO), indomethacin or ibuprofen, and growth restriction] of vancomycin pharmacokinetics have been reported in neonates. Finally, vancomycin penetrates cerebrospinal fluid (range = 7-42%). Renal function drives vancomycin pharmacokinetics. Because either age or weight is the most relevant covariate of renal maturation, these covariates should be considered first in neonatal vancomycin dosing guidelines and further adjusted by renal dysfunction indicators (e.g., ECMO and ibuprofen/indomethacin). In addition to the prospective validation of available dosing guidelines, future studies should focus on the relevance of therapeutic drug monitoring and on the value of continuous vancomycin administration in neonates.

Neonatal antibodies to infectious agents and risk of bipolar disorder: a population-based case-control study

OBJECTIVE

There is a substantial evidence base linking prenatal exposure to infectious agents and an increased risk of schizophrenia. However, there has been less research examining the potential for these exposures to also contribute to risk for bipolar disorder. The aim of this study was to examine the association between neonatal markers of selected prenatal infections and risk for bipolar disorder.

METHODS

Using population-based Danish registers, we examined 127 individuals with a diagnosis of bipolar disorder, and 127 sex and day-of-birth individually matched controls. Based on neonatal dried blood spots, we measured antibodies to herpes simplex virus type 1 (HSV-1) and 2 (HSV-2), cytomegalovirus (CMV), and Toxoplasma gondii. Relative risks were calculated for the matched pairs when examined for optical density units for antibodies to each of the infectious agents.

RESULTS

There was no association between any of the neonatal markers of prenatal infection and risk of bipolar disorder.

CONCLUSIONS

In contrast with studies of schizophrenia, our analysis does not support maternal infection with HSV-1, HSV-2, CMV, or Toxoplasma gondii as risk factors for bipolar disorder. However, larger study samples are needed, and data on, for example, specific serotypes of Toxoplasma and indicators of the timing of maternal infection are still warranted.

IgG placental transfer in healthy and pathological pregnancies

Placental transfer of maternal IgG antibodies to the fetus is an important mechanism that provides protection to the infant while his/her humoral response is inefficient. IgG is the only antibody class that significantly crosses the human placenta. This crossing is mediated by FcRn expressed on syncytiotrophoblast cells. There is evidence that IgG transfer depends on the following: (i) maternal levels of total IgG and specific antibodies, (ii) gestational age, (iii) placental integrity, (iv) IgG subclass, and (v) nature of antigen, being more intense for thymus-dependent ones. These features represent the basis for maternal immunization strategies aimed at protecting newborns against neonatal and infantile infectious diseases. In some situations, such as mothers with primary immunodeficiencies, exogenous IgG acquired by intravenous immunoglobulin therapy crosses the placenta in similar patterns to endogenous immunoglobulins and may also protect the offspring from infections in early life. Inversely, harmful autoantibodies may cross the placenta and cause transitory autoimmune disease in the neonate.

Betamethasone effects on the endocervical inflammatory cytokines in preterm labor: a randomized clinical trial

OBJECTIVE

This study aimed to investigate the effect of betamethasone treatment on the endocervical concentration of IL-1β, IL-4, IL-6, and TNF-α in preterm labor patients.

STUDY DESIGN

We studied 68 prime-gravid women in preterm labor between 34 and 37 weeks of gestation without clinical infection. Endocervical concentrations of inflammatory cytokines were assessed; immediately on admission and 48 h after administration of two doses of intramuscular betamethasone (12 mg/kg). Wilcoxon and Mann-Whitney tests along with χ(2) and Student's t tests were utilized for statistical analysis.

RESULTS

In the betamethasone group IL-1β and TNF-α significantly decreased (P<0.001), and IL-6 and IL-4 increased (P: NS). Among patients delivered before or on the 7th day of admission IL-6 and TNF-α were higher at the most significant levels (P<0.001) compared to IL-1β and IL-4 (P: 0.001, 0.002 in respect).

CONCLUSION

Betamethasone can help induce the down regulation of endocervical inflammatory cytokines in patients with preterm labor.

Direct gene transfer to the CNS prevents emergence of neurologic disease in a murine model of mucopolysaccharidosis type I

The mucopolysaccharidoses (MPSs) are a group of 11 storage diseases caused by disruptions in glycosaminoglycan (GAG) catabolism, leading to their accumulation in lysosomes. Resultant multisystemic disease is manifested by growth delay, hepatosplenomegaly, skeletal dysplasias, cardiopulmonary obstruction, and, in severe MPS I, II, III, and VII, progressive neurocognitive decline. Some MPSs are treated by allogeneic hematopoietic stem cell transplantation (HSCT) and/or recombinant enzyme replacement therapy (ERT), but effectiveness is limited by central nervous system (CNS) access across the blood-brain barrier. To provide a high level of gene product to the CNS, we tested neonatal intracerebroventricular (ICV) infusion of an adeno-associated virus (AAV) serotype 8 vector transducing the human α-L-iduronidase gene in MPS I mice. Supranormal levels of iduronidase activity in the brain (including 40× normal levels in the hippocampus) were associated with transduction of neurons in motor and limbic areas identifiable by immunofluorescence staining. The treatment prevented accumulation of GAG and GM3 ganglioside storage materials and emergence of neurocognitive dysfunction in a modified Morris water maze test. The results suggest the potential of improved outcome for MPSs and other neurological diseases when a high level of gene expression can be achieved by direct, early administration of vector to the CNS.

T cell cytokines and the risk of blood stream infection in extremely low birth weight infants

Cytokines mediate the host immune response to infectious micro-organisms. The objective of this study was to determine whether immune regulatory interleukins (IL-4, IL-5, IL-6, and IL-10) and inflammatory cytokines (Interferon-γ [INF-γ], tumor necrosis factor-β [TNF-β], IL-2, and IL-17) are associated with an increased risk of developing blood stream bacterial/fungal infection (BSI) in extremely low birth weight (ELBW) infants. ELBW infants from 17 NICHD Neonatal Research Network centers without early onset sepsis were studied. Cytokines were measured from blood on days 1, 3, 7, 14, and 21 after birth. 996 ELBW infants contributed a minimum of 4080 unique measurements for each cytokine during the five sampling periods. Infants with BSI had lower levels of the inflammatory cytokines IL-17 (p=0.01), and higher levels of the regulatory cytokines, IL-6 (p=0.01) and IL-10 (p<0.001). Higher levels of regulatory cytokines relative to pro-inflammatory cytokines were associated with increased risk of BSI even after adjusting for confounding variables. In ELBW infants, the ratio of immune regulatory cytokines to inflammatory cytokines was associated with development of BSI. Altered maturation of regulatory and inflammatory cytokines may increase the risk of serious infection in this population.

A Danish National Birth Cohort study of maternal HSV-2 antibodies as a risk factor for schizophrenia in their offspring

BACKGROUND

Several studies have implicated early infections, including maternal infection with herpes simplex virus 2 (HSV-2), as an environmental risk factor for schizophrenia.

METHODS

A case-control study nested within the national Danish birth cohort constituted by the PKU Biobank covering all children born in Denmark since 1981. 602 cases of schizophrenia (ICD-10 F20) were ascertained in the Danish Psychiatric Central Register, covering all in- and out-patient contacts in Denmark, and 602 controls were matched individually on gender, exact date of birth and living in Denmark on the date the case became a case. Incidence rate ratio for schizophrenia was estimated using conditional logistic regression. Main exposure was HSV-2 IgG antibody levels. Confounders and potential interacting factors included family history of mental illness, place of birth and gestational age at time of birth.

RESULTS

Elevated levels of maternal HSV-2 IgG were associated with schizophrenia risk (IRR 1.56; 95% CI 1.17-2.07, p=0.002). This association was not confounded by a maternal or sibling history of psychiatric illness, place of birth, parental age, gestational age, or immigrant status of the parents. However, adjustment for paternal psychiatric history reduced risk slightly (IRR 1.43; 95% CI 1.06-1.92, p=0.02).

CONCLUSIONS

The study replicates an association between maternal HSV-2 IgG levels and schizophrenia risk. Since the confounding by familial risk factors is confined to paternal mental illnesses not belonging to the schizophrenia spectrum, we hypothesize that this confounding may be partly due to other risk factors, e.g., other sexually transmitted infections, rather than reflecting variations in genetic liability to develop schizophrenia.

Role of mannose-binding lectin in nosocomial sepsis in critically ill neonates

We investigated the association of mannose-binding lectin (MBL) serum levels with nosocomial sepsis (NS), their changes overtime during infection, their relation with pathogens, with the MBL2 genotype and their relationship with mortality. In a prospective observational study, we included 365 critically ill neonates: 261 had no infection and 104 had at least 1 septic event. The median MBL serum concentration was significantly lower in infected than in noninfected neonates (p < 0.001). Low MBL levels on admission increased the risk of infection, independently from gestational age and invasive procedures. The median peak MBL level during infection was higher than the median level on admission (p < 0.001) and was correlated with it (r(2) = 0.83, p < 0.001). Moreover, MBL levels on admission were not associated with death (OR = 0.80, 95% CI = 0.56-1.14, p = 0.21). Similarly, no association was found between MBL peak levels during infection and death among infected neonates (OR = 1.10, 95% CI = 0.78-1.57, p = 0.57). In 127 neonates (42 infected) genotyped for exon-1 and -221 promoter MBL2 variants, we did not find significant difference in the frequencies of MBL2 genotypes between infected and noninfected neonates. Moreover, no association was found between MBL2 genotypes and death.