Innate immunity of the newborn: basic mechanisms and clinical correlates

Dilemma in prevention of pertussis infection among infants under six months in China

INTRODUCTION

Pertussis poses a significant threat to infants under six months due to their immature immune systems, limited maternal antibody protection, and constraints in the vaccination schedule. Despite vaccination efforts, this group remains highly susceptible to severe complications. Addressing these challenges is crucial for improving the health outcomes of infants in China.

AREAS COVERED

This review examines the primary challenges in preventing pertussis infections among infants under six months in China, focusing on factors such as underdeveloped immune system and inadequate maternal antibody protection. It analyzes limitations in current vaccination strategies and the impact of socio-cultural factors, healthcare resource distribution, and surveillance inadequacies. A comprehensive literature search was conducted to identify potential solutions, including enhancing maternal immunization, adjusting early vaccination strategies, increasing vaccine coverage, and developing new vaccines. The review synthesizes current research findings and data to provide a detailed overview of these issues.

EXPERT OPINION

Infants under six months are particularly vulnerable to pertussis. Early and effective prevention strategies, such as enhanced maternal immunization and adjusted vaccination schedules, are needed. Increasing vaccine coverage and developing safer, more immunogenic vaccines are essential. Policymakers should prioritize these measures to reduce pertussis incidence and complications among infants in China.

Astragalus Extract Mixture HT042 Reverses Cyclophosphamide-Induced Immunosuppression Through Dual Modulation of Innate and Adaptive Immunity

Deficiencies in immune function increase susceptibility to infections and chronic diseases by impairing immune surveillance and tolerance mechanisms, especially in children with immature immune systems. Chronic inflammation associated with immune dysfunction can impair childhood by suppressing the GH-IGF-1. HT042 is composed of Astragalus mongholicus, Eleutherococcus senticosus, and Phlomis umbrosa, which are medicinal herbs that are traditionally utilized in East Asia to promote growth and enhance immune function; thus, HT042 itself holds potential as an immunomodulator. We evaluated the immunomodulatory effects of HT042 in a cyclophosphamide (CYP)-induced immunosuppressed mouse model, as well as in ex vivo primary splenocytes and RAW 264.7 macrophages. HT042 demonstrated remarkable immune-enhancing effects, including the restoration of weight loss and hematological parameters, as well as enhancing NK cell activity. Primary splenocytes treated with HT042 showed increased expression of CD3, CD4, and CD8, along with Th subset transcription factors (T-bet, GATA3, RORγt, Foxp3) and corresponding cytokines (IFN-γ, IL-4, IL-17, IL-10). In RAW 264.7 macrophages, HT042 increased nitric oxide production and upregulated NOS2, COX-2, and inflammatory cytokines (IL-6, IL-1β, TNF-α). It is noteworthy that HT042 enhances both innate and adaptive immune pathways, particularly via T cell modulation and macrophage activation, as this study is among the first to demonstrate such effects in the context of CYP-induced immunosuppression.

Protective immune response against Rhodococcus equi: An innate immunity-focused review

Rhodococcus equi causes pyogranulomatous pneumonia in foals and immunocompromised people. Despite decades of research efforts, no vaccine is available against this common cause of disease and death in foals. The purpose of this narrative review is to summarise the current understanding of interactions between R. equi and the host innate immune system, to describe features of the immune response that are associated with resistance or susceptibility to R. equi infection, and help guide strategies for developing novel approaches for preventing R. equi infections. Virulence of R. equi in foals has been attributed to the virulence associated protein A which allows intracellular survival in macrophages by preventing acidification of R. equi-containing vacuole. Additionally, foal susceptibility to R. equi infection is associated with immaturity and naivety of innate and adaptive immune systems, while adult horses with fully functional immune system are resistant to pneumonia. Specific interaction between R. equi and innate immune cells can result in bacterial survival or death; learning how to manipulate these responses to control infection is critical to prevent pneumonia in foals. Administration of live vaccines and stimulation of innate immune responses appears to improve foals' immune response and has the potential to overcome the challenges of foal active vaccination and elicit protection against pneumonia.

Human models that inform antiretroviral therapy-free remission with perinatally acquired HIV infection

PURPOSE OF REVIEW

Rare persons who achieve disease-control despite high viral loads (viraemic nonprogressors) or maintain virologic control in the absence of antiretroviral therapy (ART) (elite controllers) or following ART interruption (posttreatment controllers) possess protective factors that can be harnessed for interventions to achieve ART-free remission. This review broadly summarizes these phenotypes in adults and children, and updates on findings important in informing strategies for ART-free remission in children with HIV.

RECENT FINDINGS

To date, only a few individual cases of posttreatment control have been described in children. Smaller HIV reservoir size with very early ART initiation in neonates with in-utero acquired HIV associates with improved virological and immunological outcomes. Nine new cases of ART-free remission in children were recently described - 4 from the P1115 trial, and 5 males from the Ucwaningo Lwabantwana study in South Africa. A striking reduction in the decay of intact proviruses was observed over three decades on suppressive ART in two early-treated twins with HIV.

SUMMARY

The unique environment of perinatal HIV infection favours effective restriction and decay of the HIV-1 reservoir with suppressive ART initiated very early. Sex and population differences require consideration in ongoing studies to inform ART-free remission.

Antibody function predicts viral control in newborn monkeys immunised with an influenza virus HA stem nanoparticle

The lack of an approved influenza vaccine for infants <6 months, coupled with the requirement for annual updates of current vaccines, warrants the development of a universal vaccine that can confer protection in young infants. Here we test the ability of a ferritin nanoparticle universal influenza vaccine (H1ssF) containing the stem region of hemagglutinin (HA) adjuvanted with AddaVax to elicit responses in newborn African green monkeys (AGM). Vaccinated newborns show robust HA stem-specific IgG responses but, despite the high antibody levels, viral load in the lung following H1N1 Ca09 challenge is variable among animals. Further analysis indicates that viral clearance is correlated with the presence of antibodies with neutralizing and antibody-dependent cellular phagocytosis activity. Our findings show that newborn AGM can generate functional HA stem-specific antibodies for viral clearance following vaccination with H1ssF+AddaVax and support further investigation of H1ssF as a universal vaccine for this vulnerable human population.

Progress of pediatric liver transplantation: In Japan and beyond

ABSTRACT

Organ transplantation, particularly pediatric liver transplantation (LT), has transformed medical practice over the past six decades, providing life-saving interventions for children with end-stage liver disease. This review demonstrated the historical milestones of pediatric organ transplantation, emphasizing Japan's contributions, mainly through the National Center for Child Health and Development. While early transplantation efforts in the 1950s and 1960s faced significant challenges, breakthroughs in preservation methods, immunosuppressive therapies, surgical techniques, and innovations such as living donor LT in Asia have greatly improved success rates. Japan's pediatric LT landscape is distinct, primarily due to its reliance on living donor LT, shaped by cultural and religious influences that have traditionally restricted deceased donor organ donation. This review manuscript discusses Japan's pioneering role in expanding the indications for pediatric LT to include rare conditions such as inherited metabolic disorders and hepatoblastoma. It highlights recent innovations such as hyper-reduced lateral segment grafts, machine perfusion, and minimally invasive surgery that have further improved outcomes. International collaboration has facilitated the sharing of expertise, advancing pediatric liver transplantation practice worldwide. Despite these achievements, challenges remain, particularly in light of Japan's declining birth rate, which threatens the sustainability of pediatric transplant services. This review emphasizes the need for centralized transplant facilities, greater awareness of brain-dead organ donation, and continued medical advances to ensure that pediatric LT remains a viable, life-saving option for future generations.

Disease resistance is more costly at younger ages: An explanation for the maintenance of juvenile susceptibility in a wild plant

High juvenile susceptibility drives infectious disease epidemics across kingdoms, yet the evolutionary mechanisms that maintain this susceptibility are unclear. We tested the hypothesis that juvenile susceptibility is maintained by high costs of resistance by quantifying the genetic correlation between host fitness and age-specific innate resistance to a fungal pathogen in a wild plant. We separately measured the resistance of 45 genetic families of the wild plant, Silene latifolia, to its endemic fungal pathogen, Microbotryum lychnidis-dioicae, at four ages in a controlled inoculation experiment. We then grew these same families in a field common garden and tracked survival and fecundity over a 2-y period and quantified the correlation between age-specific resistance and fitness in the field. We found significant fitness costs associated with disease resistance at juvenile but not at adult host stages. We then used an age-structured compartmental model to show that the magnitude of these costs is sufficient to prevent the evolution of higher juvenile resistance in models, allowing the disease to persist. Taken together, our results show that costs of resistance vary across host lifespan, providing an evolutionary explanation for the maintenance of juvenile susceptibility.

Cryptococcus albidus fungemia and probable meningitis in very preterm newborn: a case report and review of the literature

BACKGROUND

In pediatric and neonatal age groups, infections from non-neoformans Cryptococcus species, notably Cryptococcus albidus, are rarely encountered. C. albidus is an emerging fungal pathogen that causes severe diseases in immunosuppressed patients; furthermore, it has rarely been reported to cause diseases in immunocompetent patients. Several cases have been described in adults who were severely immunosuppressed. Importantly, the clinical symptoms in these reported cases include fungemia, meningitis, keratitis, pulmonary and cutaneous infections. Individuals at risk include neutropenic patients, those with indwelling intravenous devices, those on prolonged steroid or antibiotic use, and those with impaired immune systems and prematurity. The susceptibility of preterm infants with low birth weight to infections, particularly fungal ones, remains a significant concern. This report presents a rare case of fungemia and meningitis due to C. albidus in a preterm neonate, emphasizing the clinical significance and potential implications for future treatment and management. This report aims to alert physicians of the rarity of C. albidus infections in pediatric patients and to review the clinical significance, pathology, treatment, and outcomes.

CASE PRESENTATION

We report the first case of C. albidus fungemia and meningitis in a very low-birth-weight, preterm infant of 31 weeks. Notably, the patient was admitted for lifesaving treatment from the Alleith Hospital due to prematurity. The patient received surfactant due to ARDS, TPN, and fluconazole prophylaxis. On day 11, features of sepsis were observed and the blood culture grew C. albidus, which was sensitive to liposomal agents. CSF evaluation suggested meningitis. The patient improved following a six-week treatment regimen with liposomal formulations of amphotericin B at a dosage of 5 mg/kg body weight once daily, notably administered without 5-fluorocytosine, and experienced no sequelae.

CONCLUSIONS

This case report underscores the importance of early diagnosis and appropriate antifungal treatment for managing rare fungal infections in vulnerable populations, such as preterm infants. Moreover, it highlights the need for improved diagnostic platforms and comprehensive management protocols for rare pathogens in neonatal settings.

Accuracy of International Guidelines in Identifying Normal Liver Histology in Chinese Patients With HBeAg-Positive Chronic HBV Infection

We evaluated the diagnostic accuracy of various international guideline criteria for identifying HBeAg-positive chronic HBV infection patients with no significant liver disease. A total of 1108 HBeAg-positive CHB patients were retrospectively enrolled. The guidelines assessed included those from the European Association for the Study of the Liver (EASL) 2017, the American Association for the Study of the Liver Disease (AASLD) 2018, the Asian Pacific Association for the Study of the Liver (APASL) 2015 and the Chinese Society of Hepatology (CSH) 2022. The CSH criteria demonstrated a higher proportion of patients with G0-1 and S0-1 (82.9%) compared to the EASL (75.9%), AASLD (75.3%) and APASL groups (58.8%). Additionally, the CSH criteria exhibited a significantly higher predictive value (AUC 0.782, 95% CI 0.754-0.809) than the EASL (AUC 0.765, 95% CI 0.737-0.793), AASLD (AUC 0.749, 95% CI 0.720-0.778) and APASL (AUC 0.720, 95% CI 0.690-0.750) criteria for identifying G0-1 and S0-1. Adding quantitative HBsAg levels (> 104 IU/mL) to the EASL, AASLD and APASL criteria improved diagnostic performance. Consequently, the CSH guideline thresholds showed higher accuracy in identifying Chinese HBeAg-positive patients with no significant liver disease compared to EASL, AASLD and APASL criteria, emphasising the importance of considering quantitative HBsAg in the evaluation of HBeAg-positive chronic HBV infection.

Prenatal Exposure to Proton Pump Inhibitors and Risk of Serious Infections in Offspring During the First Year of Life: A Nationwide Cohort Study

INTRODUCTION AND OBJECTIVE

Proton pump inhibitor (PPI) use in children increases the risk of infections, prompting inquiry into the impact of prenatal PPIs exposure on serious infections in offspring. As a research gap in this area exists, this study aimed to address it by assessing the association between prenatal PPIs exposure and serious infections in infants during their first year of life.

METHODS

Using the French health insurance data warehouse (SNDS) (2013-2018), we conducted a retrospective cohort study on singleton, full-term liveborn non-immunocompromised infants, stratified by PPI use during the first three months of life (early-life use). Proton pump inhibitor dispensing in ambulatory care settings during pregnancy defined exposure. Outcomes concerned any serious infections in offspring aged between 3 and 12 months. Adjusted odds ratios (aORs) were estimated using logistic regression with multivariable models to control for potential confounders.

RESULTS

Of the 2,485,545 infants included, 497,060 (23.3%) were prenatally exposed to PPIs and 97,767 (4.6%) had PPI use during the first three months of life. Prenatal PPI exposure was associated with serious infections in offspring (aOR, 1.09 [95% CI, 1.07-1.10]) in infants without early-life PPIs use. No association was found for infants with early-life PPI use (aOR, 1.05 [95% CI, 1.00-1.11]). Gastrointestinal infections were the sole site with persistent significance.

CONCLUSION

Prenatal PPI exposure is common and is not associated with a major risk of serious infections in infants during their first year. However, even after adjusting for several confounding factors, a weak association remains, especially in infants without early-life PPI use. While offering reassurance, adherence to clinical guidelines is still crucial.

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.

Regulatory T-Cells During Pregnancy Relate to Women's Own Childhood History of Microbial Exposure

OBJECTIVES

Previous studies found that children with siblings, farm residence, and other proxies of greater microbial contacts had lower rates of hyper-responsive immune disorders. Yet, scientific debate persists regarding whether the human immune system is educated in early life primarily as a function of pathogenic or benign microbial exposures, or both. Furthermore, pregnancy relies on women's intrinsic immunosuppressive function, yet it remained unknown how immunoregulation in pregnant women relates to early-life microbial exposures. Here, we conduct a preliminary examination of whether childhood microbial exposures prime women's pregnancy-related immunoregulatory capacity.

METHODS

We administered retrospective questionnaires to estimate 55 pregnant women's early-life exposure to pathogenic (e.g., illness) and benign (e.g., pets; rural residence) microbes. Tolerogenic regulatory T-cells (Tregs) and Treg subtypes were measured by flow cytometry from peripheral blood.

RESULTS

Results show that proxies for both pathogenic and benign exposures were positively associated with Treg concentrations.

CONCLUSIONS

These findings offer insights that may help elucidate the relative contributions of early-life pathogenic ("hygiene hypothesis") and benign ("old friends hypothesis") microbial exposures toward the expansion of the Treg compartment. Human evolutionary history is characterized by changing microbial exposures as human residency patterns, living environments, and subsistence strategies changed. In this context, our findings suggest the possibility of less gestational pathology in human evolutionary past conditions typified by richer diversity of microbial exposure.

Regional and longitudinal dynamics of human milk protein components assessed by proteome analysis on a fast and robust micro-flow LC-MS/MS system

An in-depth exploration of molecular composition of human milk could provide a scientific basis for the development of substitutes. The present study was conducted to analyze human milk proteins from 110 individuals from five regions of China and across three stages of lactation to investigate the change patterns. We developed a micro-flow liquid chromatography tandem mass spectrometry (μLC-MS/MS) system with data-independent acquisition (DIA) proteomics technology that can rapidly and stably characterize the human milk proteome. In total, 2796 proteins were identified. Among these proteins, CPM, ACSL1, and RPL13 changed significantly during lactation, and SCP2, GALK1 and GALE changed significantly between regions. Bioinformatics analysis revealed that human milk is altered by complex interactions between genetic and environmental factors. Our results not only reveal the regional and longitudinal patterns of change in human milk proteome but also provide theoretical basis and technical support for the production and quality control of infant formula.

Maternal derived antibodies and avian β-defensins expression patterns and their correlation in the yolk sac tissue of different chicken breeds (Gallus gallus)

The expression of maternal derived antibodies (MDAs) and avian β-defensins (AvBDs) in yolk sac tissue may be age-specific and influenced by breed, thereby immunological window difference in hatchlings. This study investigated the mRNA expression of MDAs and AvBDs in the yolk sac tissues of Beijing You and Hy-Line Gray chickens from the embryonic day (ED)7 to 3 days after hatch (DAH). Hy-Line showed a higher embryo bodyweight and a lower residual yolk weight at ED17 (P < 0.05). The expression of IgY and FcRY was higher in the Hy-Line (P < 0.05). In Beijing You, IgA level decreased from ED15 to 19 but peaked from day old hatch to 3 DAH. In Hy-Line, IgA increased from ED19 to 3 DAH (P < 0.05). IgY increased from ED17 to day old hatch (DOH), but declined from DOH to 3 DAH in Beijing You, whereas in Hy-Line, it declined from ED9 to 15 and ED19 to 3 DAH (P < 0.05). FcRY expression declined from DOH to 3 DAH in Beijing You and from ED19 to 3 DAH in Hy-Line (P < 0.05). The expression of AvBD5 increased from ED7 to 13 and ED19 to 3 DAH, and decreased from ED13 to 19 in both breeds. A similar expression patterns of AvBD10 was observed in breeds, increased from ED7 to 11, followed by a decline after ED11. AvBD12 expression peaked at ED17 in Beijing You and from ED15 to 17 in Hy-Line (P < 0.05), then declined from ED17 to 3 DAH in both breeds. The study observed temporal expression development patterns of AvBD5 and AvBD10 in both breeds and AvBD12 in Beijing You, with a correlation coefficient of R2 > 0.5. Overall, the lower yolk residue for faster growth of chickens compromised the expression of MDAs and AvBDs, except for IgA and AvBD5. These results suggest a broader immunological window and highlight the need to focus on maintaining specific MDAs and AvBDs in the strategies of embryonic feeding.

Maternal-Newborn ABO Blood Group Congruence Among Consecutive Births and Risk of Serious Neonatal Infection: Retrospective Cohort Study

BACKGROUND

Differing ABO blood groups between a mother and her fetus may confer a lower risk of serious neonatal infection. How sensitization in the first pregnancy influences this phenomenon in a subsequent pregnancy is unclear. Accordingly, this study determined whether maternal-newborn ABO blood group incongruence in a first pregnancy further modifies the risk of serious infection in a subsequent pregnancy marked by ABO incongruency.

METHODS

This population-based retrospective cohort study used linked patient-level datasets in Ontario, Canada, from 2008 to 2022. Included were mothers with 2 consecutive live births, with recorded maternal and newborn ABO blood group data. The exposure considered both first- and second-born siblings' ABO blood group congruency with their mother. The outcome was a serious neonatal infection within 27 days after birth. Logistic regression models generated adjusted odds ratios (aORs) and 95% confidence intervals (CIs), adjusted for gestational age at birth.

RESULTS

Included were 14,739 mother-infant triads. Relative to maternal-newborn congruency in the second pregnancy, incongruent ABO blood groups in the second pregnancy were associated with an aOR of 0.72 (95% CI, 0.53-0.97) for a serious neonatal infection arising in the second-born infant. However, if the first and second siblings each had incongruent ABO blood groups with their mother, the aOR of serious infection in the second-born infant was not significantly lower [0.74 (95% CI, 0.52-1.06)].

CONCLUSIONS

Second-born infants whose ABO blood group was incongruent with that of their mother had a lower risk of serious neonatal infection. However, ABO incongruence from a prior birth did not modify that relation.

Neonatal Immunity to Candida: Current Understanding and Contributions of Murine Models

Neonatal candidiasis poses significant clinical challenges due to its potential for severe morbidity and mortality in vulnerable infants. Due to their underdeveloped immune system, neonates are at a higher risk for infections caused by Candida species. They can vary from mild to severe, including penetrating deep tissues, bloodstream spread, and dissemination to organs. The immune system of newborns is marked by a limited innate immune response, with lower levels of pro-inflammatory cytokines. Adaptive immunity, important for lasting protection, also experiences delayed maturation with weakened Th1 and Th17 responses. These shortcomings result in a higher vulnerability to Candida infections during infancy. Murine models have been crucial in understanding the reasons behind this susceptibility. These models assist in examining how different immune elements, like neutrophils, macrophages, and T cells, and their interactions are involved in Candida infections. Moreover, they offer an understanding of how early-life exposure to Candida affects immune responses and may aid in developing possible therapeutic plans. In this article we review current results from research to provide a thorough summary and critical insights into neonatal immune response to Candida, highlighting the importance of using murine models in this field of study. Understanding these immune dynamics is essential for creating specific treatments and preventive strategies to prevent newborns from Candida infections, ultimately improving neonatal health outcomes.

Surfactant Protein-A and its immunomodulatory roles in infant respiratory syncytial virus infection: a potential for therapeutic intervention?

The vast majority of early-life hospital admissions globally highlight respiratory syncytial virus (RSV), the leading cause of neonatal lower respiratory tract infections, as the major culprit behind the poor neonatal outcomes following respiratory infections. Unlike those of older children and adults, the immune system of neonates looks rather unique, therefore mostly counting on the innate immune system and antibodies of maternal origins. The collaborations between cells and immune compartments during infancy inclines bias toward a T-helper 2 (Th2) immune profile and thereby away from a T-helper 1 (Th1) immune response. What makes it more problematic is that RSV infection also tends to elicit a stronger Th2-biased immune response and drive an aberrant allergy-like inflammation. It is thus evident how RSV infections potentially pave the way for wheezing recurrences and childhood asthma later in life. Surfactant, the essential lung substance for normal breathing processes in mammals, has immunomodulatory properties including lung collectins such as Surfactant Protein-A (SP-A), which is the most abundant protein component of surfactant, and also Surfactant Protein-D (SP-D). Deficiency of SP-A and SP-D has been found to be associated with impaired pathogen clearance and exacerbated immune responses during infections. We therefore conducted a review of the literature to describe pathomechanisms of RSV infections during blunted neonatal immunity potentially facilitating allergy-like inflammatory events within the developing lungs and highlight the potential protective role of the humoral collectin SP-A to mitigate these in the "early in life" pulmonary immune system.

Epicardial pacing outcomes in infants with heart block: Lead and device complications from a multicenter experience

BACKGROUND

Infants with complete heart block (CHB) require epicardial pacemaker (PM) insertion. Prior studies described epicardial pacing outcomes in infants and children, although they were limited by small or heterogeneous populations.

OBJECTIVE

This study aimed to explore patient- and procedure-level associations with device complications in infants with CHB who received a permanent PM.

METHODS

This was a multicenter, retrospective cohort study including infants receiving an epicardial PM between 2000 and 2021 for CHB. The primary outcome was time to device-related adverse event: lead failure requiring revision; pocket infection; exit block requiring increased pacing output; or lead-related coronary artery compression. Time-to-event analysis was performed by the Kaplan-Meier method with a multivariable Cox proportional hazards model.

RESULTS

There were 174 infants who received an epicardial PM (282 bipolar, 39 unipolar leads) for CHB. Median age and weight at PM were 93.5 days and 4.5 kg, respectively. Pacing indication was postoperative CHB in 63% and congenital CHB in 37%. The median follow-up was 2.1 years. The primary outcome occurred in 26 infants at a median time to event of 0.6 year. Age ≤90 days at PM implantation was the most significant risk factor for a device-related adverse event (hazard ratio, 7.02; P < .001), primarily driven by pocket infections. Lead failure occurred in 3% of leads with a 5- and 10-year freedom from failure of 93% and 83%, respectively.

CONCLUSION

Device complications affect 15% of infants receiving a permanent PM for heart block. Age ≤90 days at PM implantation is especially associated with infectious complications. Epicardial lead durability appears similar to previously reported pediatric experiences.

Ontogeny and function of the intestinal epithelial and innate immune cells during early development of chicks: to explore in ovo immunomodulatory nutrition

Intestinal epithelial cells (IECs) and innate immune cells in the gastrointestinal tract (GIT) of chickens play crucial roles in pathogens defense and maintaining gut health. However, their effectiveness influenced with their developmental and functional stages during pre and post hatch periods of chick. During embryonic development, differentiation and migration of these innate immune systems are tightly regulated by diverse cellular and molecular factors. The maturation and functionality of IECs are histologically evident starting embryonic day (ED) 14. Moreover, the innate immun cells, such as dendritic cells (DCs), macrophages, natural killer (NK) cells, and gamma-delta (γδ) T cells have showed developmental expression varation, while most identified by the 3rd days of incubation and capable of responsing to their cognate ligands of pathogens by ED 17, it may not efficient during posthatch period. In modern poultry production, in ovo feeding of bioactive substances is a topic of interest to maximize the protection capability of hatched chicks by enhancing improvement on the development of innate immune systems. However, their actions and effects on each distinct innate immune involved response are inconsistent and not clearly understood. Thus, summarizing the ontogeny and function of IECs, innate immunity systems, and interaction mechanisms of in ovo feeding of bioactive substances could provide baseline information for designing targeted in ovo feeding interventions to modulate cell waise specific innate immune systems.

The Role of Breast Milk Cell-Free DNA in the Regulation of the Neonatal Immune Response

The neonatal period is a critical phase for the development of the intestinal immune system, marked by rapid adaptation to the external environment and unique nutritional demands. Breast milk plays a pivotal role in this transition, yet the mechanisms by which it influences neonatal mucosal immunity remain unclear. This review examines the potential mechanisms by which cell-free DNA (cfDNA) in breast milk may impact neonatal immune development, particularly through Toll-like receptor 9 (TLR9) signalling and gut microbiota interactions. We propose that cfDNA in breast milk interacts with TLR9 on the apical surface of neonatal intestinal epithelial cells, potentially serving as an initial anti-inflammatory stimulus before the establishment of commensal bacteria. This hypothesis is supported by the high concentration and stability of cfDNA in breast milk, as well as the known activation of TLR9 by mitochondrial DNA in breast milk. The review emphasises the need for further empirical research to validate these interactions and their implications for neonatal health, suggesting that understanding these dynamics could lead to improved strategies for neonatal care and disease prevention.

Could P2X7 receptor be a potencial target in neonatal sepsis?

The United Nations Inter-Agency Group for Child Mortality Estimation (UNIGME) estimates that every year 2.5 million neonates die in their first month of life, accounting for nearly one-half of deaths in children under 5 years of age. Neonatal sepsis is the third leading cause of neonatal mortality. The worldwide burden of bacterial sepsis is expected to increase in the next decades due to the lack of effective molecular therapies to replace the administration of antibiotics whose efficacy is compromised by the emergence of resistant strains. In addition, prolonged exposure to antibiotics can have negative effects by increasing the risk of infection by other organisms. With the global burden of sepsis increasing and no vaccine nor other therapeutic approaches proved efficient, the World Health Organization (WHO) stresses the need for new therapeutic targets for sepsis treatment and infection prevention (WHO, A73/32). In response to this unresolved clinical issue, the P2X7 receptor (P2X7R), a key component of the inflammatory cascade, has emerged as a potential target for treating inflammatory/infection diseases. Indeed numerous studies have demonstrated the relevance of the purinergic system as a pharmacological target in addressing immune-mediated inflammatory diseases by regulating immunity, inflammation, and organ function. In this review, we analyze key features of sepsis immunopathophysiology focusing in neonatal sepsis and on how the immunomodulatory role of P2X7R could be a potential pharmacological target for reducing the burden of neonatal sepsis.

Regulation of host metabolism and defense strategies to survive neonatal infection

Two distinct defense strategies, disease resistance (DR) and disease tolerance (DT), enable a host to survive infectious diseases. Newborns, constrained by limited energy reserves, predominantly rely on DT to cope with infection. However, this approach may fail when pathogen levels surpass a critical threshold, prompting a shift to DR that can lead to dysregulated immune responses and sepsis. The mechanisms governing the interplay between DR and DT in newborns remain poorly understood. Here, we compare metabolic traits and defense strategies between survivors and non-survivors in Staphylococcus epidermidis (S. epidermidis)-infected preterm piglets, mimicking infection in preterm infants. Compared to non-survivors, survivors displayed elevated DR during the initial phase of infection, followed by stronger DT in later stages. In contrast, non-survivors showed clear signs of respiratory and metabolic acidosis and hyperglycemia, together with exaggerated inflammation and organ dysfunctions. Hepatic transcriptomics revealed a strong association between the DT phenotype and heightened oxidative phosphorylation in survivors, coupled with suppressed glycolysis and immune signaling. Plasma metabolomics confirmed the findings of metabolic regulations associated with DT phenotype in survivors. Our study suggests a significant association between the initial DR and subsequent DT, which collectively contributes to improved infection survival. The regulation of metabolic processes that optimize the timing and balance between DR and DT holds significant potential for developing novel therapeutic strategies for neonatal infection.

Impact of perinatal administration of probiotics on immune cell composition in neonatal mice

BACKGROUND

Newborns and especially preterm infants are much more susceptible to infections than adults. The pathogens causing infections in newborns are often detectable in the intestinal flora of affected children even before disease onset. Therefore, it seems reasonable to prevent dysbiosis in newborns and preterm infants. An approach followed in many neonatal intensive care units (NICUs) is to prevent infections in preterm infants with probiotics however their mechanisms of action of probiotics are incompletely understood. Here, we investigated the effect of perinatal probiotic exposure on immune cells in newborn mice.

METHODS

Pregnant mice were orally treated with a combination of Lactobacillus acidophilus and Bifidobacterium bifidum (Infloran®) from mid-pregnancy until the offspring were harvested. Immune cell composition in organs of the offspring were analyzed by flow cytometry.

RESULTS

Perinatal probiotic exposure had profound effects on immune cell composition in the intestine, liver and lungs of newborn mice with reduction of myeloid and B cells and induction of T cells in the probiotic treated animals' organs at weaning. Furthermore, probiotic exposure had an effect on T cell development in the thymus.

CONCLUSION

Our results contribute to a better understanding of the interaction of probiotics with the developing immune system.

IMPACT

probiotics have profound effects on immune cell composition in intestines, livers and lungs of newborn mice. probiotics modulate T cell development in thymus of newborn mice. effects of probiotics on neonatal immune cells are particularly relevant in transition phases of the microbiome. our results contribute to a better understanding of the mechanisms of action of probiotics in newborns.

High temperatures are associated with decreased immune system performance in a wild primate

Rising temperatures due to climate change are predicted to threaten the persistence of wild animals, but there is little evidence that climate change has pushed species beyond their thermal tolerance. The immune system is an ideal avenue to assess the effects of climate change because immune performance is sensitive to changes in temperature and immune competency can affect reproductive success. We investigate the effect of rising temperatures on a biomarker of nonspecific immune performance in a wild population of capuchin monkeys and provide compelling evidence that immune performance is associated with ambient temperature. Critically, we found that immune performance in young individuals is more sensitive to high temperatures compared to other age groups. Coupled with evidence of rising temperatures in the region, our results offer insight into how climate change will affect the immune system of wild mammals.

Clinical features and risk factors of Klebsiella pneumoniae infection in premature infants: a retrospective cohort study

BACKGROUND

With the continuous advancement of modern medical technology, the survival rate of premature infants has significantly increased. Klebsiella pneumoniae (K. pneumoniae) is one of the most common pathogens causing neonatal infections, particularly posing a serious risk to premature infants. This study aimed to analyze the clinical characteristics, antibiotic susceptibility profiles, and treatment outcomes of K. pneumoniae infections in these infants.

METHODS

We retrospectively compared cases of K. pneumoniae infection in premature and term infants admitted in a tertiary hospital from January 2017 to December 2022 in China. Clinical and microbiological characteristics were evaluated. Data analysis was performed using the Statistical Package for the Social Sciences (SPSS), with statistical significance defined as P < 0.05.

RESULTS

We enrolled 166 premature infants and 68 term infants. In premature infants, fetal distress, patent ductus arteriosus, patent foramen ovale, enteritis, anemia, hypoproteinemia, bloodstream infections, abdominal infection, mechanical ventilation, nasogastric feeding, drainage tube, parenteral nutrition, and prior exposure to carbapenem antibiotics were identified as significant risk factors for K. pneumoniae infections in univariate analysis. Furthermore, septic shock, bloodstream infections, abdominal infections, indwelling catheters, drainage tubes, parenteral nutrition, and previous exposure to glycopeptide antibiotics were significantly correlated with mortality. Independent risk factors for K. pneumoniae infections in premature infants included fetal distress (OR: 3.702, [95% CI: 1.056-12.986], P = 0.041), enteritis (OR: 4.434, [95% CI: 1.066-18.451], P = 0.041), anemia (OR: 4.028, [95% CI: 1.550-10.466], P = 0.004), bloodstream infections (OR: 1.221, [95% CI: 0.061-1.802], P = 0.022), mechanical ventilation (OR: 4.974, [95% CI: 1.685-14.685], P = 0.004) and prior exposure to carbapenem antibiotic (OR: 14.738, [95% CI: 2.393-90.767], P = 0.004). Additionally, abdominal infections (OR: 8.598, [95% CI: 2.000-36.957], P = 0.004) and indwelling catheters (OR: 7.698, [95% CI: 0.998-59.370], P = 0.050) were positive predictors of mortality.

CONCLUSION

K. pneumoniae isolates exhibit a notable prevalence of infection, poor treatment outcomes, and elevated resistance in preterm neonates. These findings enhance our understanding of K. pneumoniae infections and their association with clinical outcomes among premature infants.

Deleterious intestinal inflammation in neonatal mice treated with TLR2/TLR6 agonists

By providing innate immune modulatory stimuli, the early-life immune system can be enhanced to increase resistance to infections. Activation of innate cell surface receptors called pattern recognition receptors by Toll-like receptor (TLR) ligands is one promising approach that can help to control infections as described for listeriosis and cryptosporidiosis. In this study, the effect of TLR2/TLR1 and TLR2/TLR6 agonists was compared when injected into neonatal mice. Surprisingly, the stimulation of TLR2/TLR6 led to the death of the neonatal mice, which was not observed in adult mice. The TLR2/TLR6 agonist administration induced higher systemic and intestinal inflammation in both adult and neonatal mice when compared with TLR2/TLR1 agonist. The mortality of neonatal mice was interferon γ dependent and involved the intestinal production of interleukin-22 and interleukin-17A. This study clearly demonstrates that targeting TLRs as new control strategy of neonatal infections has to be used with caution. Depending on its heterodimeric form, TLR2 stimulation can induce more or less severe adverse effects relying on the age-related immune functions of the host.

Maternal-Newborn ABO Blood Groups and Risk of Bacterial Infection in Newborns

Importance

Newborn immunity largely relies on maternal-fetal transfer of antibodies in utero. Incongruency in ABO blood groups between a mother and newborn may be associated with protection against serious infections, but data specific to newborn bacterial infections are lacking.

Objective

To ascertain the association between maternal-newborn ABO blood group incongruence and lower risk of bacterial infection in newborns.

Design, Setting, and Participants

This cohort study used linked patient-level datasets for all singleton live births between January 1, 2014, and December 31, 2020, in hospitals and health centers in Ontario, Canada. The cohort comprised maternal-newborn pairs with known ABO blood groups. Data analysis was conducted between February and May 2024.

Exposure

Maternal-newborn ABO blood group incongruence vs congruence.

Main Outcomes and Measures

The primary outcome was a bacterial infection arising in newborns within 30 days of birth. Bacterial infection was cultured from either blood, cerebrospinal fluid, urine, or lung specimen. Secondary outcomes were a bacterial infection with 7 days and 90 days of birth. Modified Poisson regression generated adjusted relative risks (ARRs) and 95% CIs, adjusted for neonatal sex and preterm birth.

Results

A total of 138 207 maternal-newborn pairs (maternal mean [SD] age, 31.8 [5.1] years among those with ABO blood group incongruency and 31.5 [5.1] years among those with ABO blood group congruency; newborn mean [SD] gestational age, 38.5 [2.3] weeks among those with incongruency and 38.4 [2.5] weeks among those with congruency; 19 475 males [51.3%] with incongruency and 52 041 males [51.9%] with congruency) were analyzed. Of these pairs, 37 953 (27.5%) had ABO blood group incongruency and 100 254 (72.5%) had ABO blood group congruency. Within 30 days of birth, 328 (8.6 per 1000) newborns in the incongruent group and 1029 (10.3 per 1000) newborns in the congruent group experienced a bacterial infection, corresponding to an ARR of 0.91 (95% CI, 0.81-1.03). The ARRs for bacterial infection within 7 days and 90 days of birth were 0.89 (95% CI, 0.73-1.09) and 0.86 (95% CI, 0.78-0.94), respectively.

Conclusions and Relevance

This cohort study found no association between maternal-newborn ABO blood group incongruence and risk of bacterial infection in newborns within 30 and 7 days of birth. However, incongruence was associated with a decreased risk of bacterial infection within 90 days of birth.

Preschool-age children maintain a distinct memory CD4+ T cell and memory B cell response after SARS-CoV-2 infection

The development of the human immune system lasts for several years after birth. The impact of this maturation phase on the quality of adaptive immunity and the acquisition of immunological memory after infection at a young age remains incompletely defined. Here, using an antigen-reactive T cell (ARTE) assay and multidimensional flow cytometry, we profiled circulating severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-reactive CD3+CD4+CD154+ T cells in children and adults before infection, during infection, and 11 months after infection, stratifying children into separate age groups and adults according to disease severity. During SARS-CoV-2 infection, children younger than 5 years old displayed a lower antiviral CD4+ T cell response, whereas children older than 5 years and adults with mild disease had, quantitatively and phenotypically, comparable virus-reactive CD4+ T cell responses. Adults with severe disease mounted a response characterized by higher frequencies of virus-reactive proinflammatory and cytotoxic T cells. After SARS-CoV-2 infection, preschool-age children not only maintained neutralizing SARS-CoV-2-reactive antibodies postinfection comparable to adults but also had phenotypically distinct memory T cells displaying high inflammatory features and properties associated with migration toward inflamed sites. Moreover, preschool-age children had markedly fewer circulating virus-reactive memory B cells compared with the other cohorts. Collectively, our results reveal unique facets of antiviral immunity in humans at a young age and indicate that the maturation of adaptive responses against SARS-CoV-2 toward an adult-like profile occurs in a progressive manner.

Human Milk Oligosaccharides in Combination with Galacto- and Long-Chain Fructo-Oligosaccharides Enhance Vaccination Efficacy in a Murine Influenza Vaccination Model

Early-life nutrition significantly impacts vaccination efficacy in infants, whose immune response to vaccines is weaker compared to adults. This study investigated vaccination efficacy in female C57Bl/6JOlaHsd mice (6 weeks old) fed diets with 0.7% galacto-oligosaccharides (GOS)/long-chain fructo-oligosaccharides (lcFOS) (9:1), 0.3% human milk oligosaccharides (HMOS), or a combination (GFH) for 14 days prior to and during vaccination. Delayed-type hypersensitivity (DTH) was measured by assessing ear swelling following an intradermal challenge. Influvac-specific IgG1 and IgG2a levels were assessed using ELISAs, while splenic T and B lymphocytes were analyzed for frequency and activation via flow cytometry. Additionally, cytokine production was evaluated using murine splenocytes co-cultured with influenza-loaded dendritic cells. Mice on the GFH diet showed a significantly enhanced DTH response (p < 0.05), increased serological IgG1 levels, and a significant rise in memory B lymphocytes (CD27+ B220+ CD19+). GFH-fed mice also exhibited more activated splenic Th1 cells (CD69+ CXCR3+ CD4+) and higher IFN-γ production after ex vivo restimulation (p < 0.05). These findings suggest that GOS/lcFOS and HMOS, particularly in combination, enhance vaccine responses by improving memory B cells, IgG production, and Th1 cell activation, supporting the potential use of these prebiotics in infant formula for better early-life immune development.

Early-life infection depletes preleukemic cells in a mouse model of hyperdiploid B-cell acute lymphoblastic leukemia

ABSTRACT

Epidemiological studies report opposing influences of infection on childhood B-cell acute lymphoblastic leukemia (B-ALL). Although infections in the first year of life appear to exert the largest impact on leukemia risk, the effect of early pathogen exposure on the fetal preleukemia cells (PLC) that lead to B-ALL has yet to be reported. Using cytomegalovirus (CMV) infection as a model early-life infection, we show that virus exposure within 1 week of birth induces profound depletion of transplanted E2A-PBX1 and hyperdiploid B-ALL cells in wild-type recipients and in situ-generated PLC in Eμ-ret mice. The age-dependent depletion of PLC results from an elevated STAT4-mediated cytokine response in neonates, with high levels of interleukin (IL)-12p40-driven interferon (IFN)-γ production inducing PLC death. Similar PLC depletion can be achieved in adult mice by impairing viral clearance. These findings provide mechanistic support for potential inhibitory effects of early-life infection on B-ALL progression and could inform novel therapeutic or preventive strategies.

Immune profiling reveals umbilical cord blood mononuclear cells from South India display an IL-8 dominant, CXCL-10 deficient polyfunctional monocyte response to pathogen-associated molecular patterns that is distinct from adult blood cells

Neonate responses to pathogen-associated molecular patterns (PAMPS) differ from adults; such understanding is poor in Indian neonates, despite recognized significant infectious risk. Immune profiling analysis was undertaken of 10 secreted mediators contextualized with cellular source induced by six PAMPs in umbilical cord (CB; n = 21) and adult-blood (PBMC; n = 14) from a tertiary care hospital in South India. Differential cytokine expression analysis (minimum log2-fold difference; adj P-value < 0.05) identified bacterial PAMPs induced higher concentrations of IL-1β, IL-10, TNF-α in adults versus IL-8, GM-CSF, IFN-γ, and IL-2 in CB. CB responded to poly I:C and SARS-CoV-2 lysate with a dominant IL-8 response, whereas in PBMC, CXCL-10 dominated poly I:C, but not SARS-CoV-2, responses, highlighting potential IL-8 importance, in the absence of Type I Interferons, in antiviral CB immunity. Candida albicans was the only PAMP to uniformly induce higher secretion of effectors in CB. The predominant source of IL-8/IL-6/TNF-α/IL-1β in both CB and PBMC was polyfunctional monocytes and IFN-γ/IL-2/IL-17 from innate lymphocytes. Correlation matrix analyses revealed IL-8 to be the most differentially regulated, correlating positively in CB versus negatively in PBMC with IL-6, GM-CSF, IFN-γ, IL-2, consistent with more negatively regulated cytokine modules in adults, potentially linked to higher anti-inflammatory IL-10. Cord and adult blood from India respond robustly to PAMPs with unique effector combinations. These data provide a strong foundation to monitor, explore, mechanisms that regulate such immunity during the life course, an area of significant global health importance given infection-related infant mortality incidence.

Association between endometrial thickness and birthweight of singletons from vitrified-warmed cycles: a retrospective cohort study

RESEARCH QUESTION

What is the association between endometrial thickness (EMT) and the birthweight of singleton infants born from frozen-thawed embryo transfer cycles?

DESIGN

This retrospective cohort study was conducted from January 2016 to December 2019. Participants were categorized into a natural cycle (NC, n = 8132) group and hormone replacement therapy (HRT, n = 4975) group. Only singleton deliveries were included. The primary outcomes were measures of birthweight and relevant indexes. Multivariable logistic regression and multivariable-adjusted linear regression models that incorporated restricted cubic splines were used.

RESULTS

In the HRT group, the risk of delivering a small for gestational age (SGA) infant was increased in women with an EMT <8.0 mm (adjusted odds ratio [aOR] 1.85, 95% confidence interval [CI] 1.17-2.91) compared with women with an EMT of 8.0 to <12.0 mm, and increased with an EMT ≥12.0 mm (aOR 1.85, 95% CI 1.03-3.33). An inverted U-shaped relationship was found between EMT and birthweight in women with HRT. No significant differences were shown in birthweight z-score, or being SGA or large for gestational age, in singletons among the three EMT groups in the natural cycles.

CONCLUSIONS

A thinner endometrium seen in women undergoing HRT cycles was associated with a lower birthweight z-score, as well as a higher risk of SGA. However, no significant association was observed between EMT and birthweight z-score or SGA in the NC group. It is noteworthy that a thicker endometrium was not associated with a higher birthweight in frozen-thawed embryo transfer (FET) cycles. Women with a thin endometrium who achieve pregnancy require specialized attention, particularly if they are undergoing FET with HRT cycles.

Differences in maternal-newborn ABO blood groups and risk of serious infant infection

BACKGROUND

During pregnancy, various maternal IgG antibodies are transferred to the developing fetus, some of which may protect the newborn against infection. If a mother and her fetus have different A, B or O (ABO) blood groups, then transferred maternal antibodies may plausibly protect the infant against infection.

AIM

To determine if maternal-newborn ABO blood group incongruence vs. congruence is associated with a lower risk of serious infection in the infant.

DESIGN

Retrospective population-based cohort.

METHODS

We used linked patient-level datasets for all singleton hospital livebirths from 2008 to 2022 in Ontario, Canada, with known maternal and newborn ABO blood groups. We used a dichotomous exposure state, either ABO blood group congruent (N = 114 507) or incongruent (N = 43 074). The main outcome of interest was the risk of serious infant infection within 27 days, and from 28 to 365 days, after birth. Cox proportional hazard models generated hazard ratios and 95% confidence intervals, and were adjusted for maternal age, world region of origin, residential income quintile and gestational age at birth.

RESULTS

Relative to maternal-newborn congruency, incongruent ABO blood group was associated with an adjusted hazard ratio of 0.88 (95% CI: 0.80-0.97) for serious neonatal infection within 27 days of birth, and 0.93 (95% CI: 0.90-0.96) for serious infection between 28 and 365 days after birth.

CONCLUSIONS

Maternal-newborn ABO incongruence may be associated with a lower relative risk of a serious infant infection within 27 days, and from 28 to 365 days, after birth.

Evaluation of mRNA-LNP and adjuvanted protein SARS-CoV-2 vaccines in a maternal antibody mouse model

Maternal antibodies (matAbs) protect against a myriad of pathogens early in life; however, these antibodies can also inhibit de novo immune responses against some vaccine platforms. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) matAbs are efficiently transferred during pregnancy and protect infants against subsequent SARS-CoV-2 infections. It is unknown if matAbs inhibit immune responses elicited by different types of SARS-CoV-2 vaccines. Here, we established a mouse model to determine if SARS-CoV-2 spike-specific matAbs inhibit immune responses elicited by recombinant protein and nucleoside-modified mRNA-lipid nanoparticle (mRNA-LNP) vaccines. We found that SARS-CoV-2 mRNA-LNP vaccines elicited robust de novo antibody responses in mouse pups in the presence of matAbs. Recombinant protein vaccines were also able to circumvent the inhibitory effects of matAbs when adjuvants were co-administered. While additional studies need to be completed in humans, our studies raise the possibility that mRNA-LNP-based and adjuvanted protein-based SARS-CoV-2 vaccines have the potential to be effective when delivered very early in life.

Implications of neonatal absence of innate immune mediated NFκB/AP1 signaling in the murine liver

BACKGROUND

The developmental immaturity of the innate immune system helps explains the increased risk of infection in the neonatal period. Importantly, innate immune signaling pathways such as p65/NFκB and c-Jun/AP1 are responsible for the prevention of hepatocyte apoptosis in adult animals, yet whether developmental immaturity of these pathways increases the risk of hepatic injury in the neonatal period is unknown.

METHODS

Using a murine model of endotoxemia (LPS 5 mg/kg IP x 1) in neonatal (P3) and adult mice, we evaluated histologic evidence of hepatic injury and apoptosis, presence of p65/NFκB and c-Jun/AP1 activation and associated transcriptional regulation of apoptotic genes.

RESULTS

We demonstrate that in contrast to adults, endotoxemic neonatal (P3) mice exhibit a significant increase in hepatic apoptosis. This is associated with absent hepatic p65/NFκB signaling and impaired expression of anti-apoptotic target genes. Hepatic c-Jun/AP1 activity was attenuated in endotoxemic P3 mice, with resulting upregulation of pro-apoptotic factors.

CONCLUSIONS

These results demonstrate that developmental absence of innate immune p65/NFκB and c-Jun/AP1 signaling, and target gene expression is associated with apoptotic injury in neonatal mice. More work is needed to determine if this contributes to long-term hepatic dysfunction, and whether immunomodulatory approaches can prevent this injury.

IMPACT

Various aspects of developmental immaturity of the innate immune system may help explain the increased risk of infection in the neonatal period. In adult models of inflammation and infection, innate immune signaling pathways such as p65/NFκB and c-Jun/AP1 are responsible for a protective, pro-inflammatory transcriptome and regulation of apoptosis. We demonstrate that in contrast to adults, endotoxemic neonatal (P3) mice exhibit a significant increase in hepatic apoptosis associated with absent hepatic p65/NFκB signaling and c-Jun/AP1 activity. We believe that these results may explain in part hepatic dysfunction with neonatal sepsis, and that there may be unrecognized developmental and long-term hepatic implications of early life exposure to systemic inflammatory stress.

Comparative analysis of within-host dynamics of acute infection and viral rebound dynamics in postnatally SHIV-infected ART-treated infant rhesus macaques

Viral dynamics of acute HIV infection and HIV rebound following suspension of antiretroviral therapy may be qualitatively similar but must differ given, for one, development of adaptive immune responses. Understanding the differences of acute HIV infection and viral rebound dynamics in pediatric populations may provide insights into the mechanisms of viral control with potential implications for vaccine design and the development of effective targeted therapeutics for infants and children. Mathematical models have been a crucial tool to elucidate the complex processes driving viral infections within the host. Traditionally, acute HIV infection has been modeled with a standard model of viral dynamics initially developed to explore viral decay during treatment, while viral rebound has necessitated extensions of that standard model to incorporate explicit immune responses. Previous efforts to fit these models to viral load data have underscored differences between the two infection stages, such as increased viral clearance rate and increased death rate of infected cells during rebound. However, these findings have been predicated on viral load measurements from disparate adult individuals. In this study, we aim to bridge this gap, in infants, by comparing the dynamics of acute infection and viral rebound within the same individuals by leveraging an infant nonhuman primate Simian/Human Immunodeficiency Virus (SHIV) infection model. Ten infant Rhesus macaques (RMs) orally challenged with SHIV.C.CH505 375H dCT and given ART at 8 weeks post-infection. These infants were then monitored for up to 60 months post-infection with serial viral load and immune measurements. We use the HIV standard viral dynamics model fitted to viral load measurements in a nonlinear mixed effects framework. We find that the primary difference between acute infection and rebound is the increased death rate of infected cells during rebound. We use these findings to generate hypotheses on the effects of adaptive immune responses. We leverage these findings to formulate hypotheses to elucidate the observed results and provide arguments to support the notion that delayed viral rebound is characterized by a stronger CD8+ T cell response.

Accelerated CD8+ T cell maturation in infants with perinatal HIV infection

In perinatal HIV infection, early antiretroviral therapy (ART) initiation is recommended but questions remain regarding infant immune responses to HIV and its impact on immune development. Using single cell transcriptional and phenotypic analysis we evaluated the T cell compartment at pre-ART initiation of infants with perinatally acquired HIV from Maputo, Mozambique (Towards AIDS Remission Approaches cohort). CD8+ T cell maturation subsets exhibited altered distribution in HIV exposed infected (HEI) infants relative to HIV exposed uninfected infants with reduced naive, increased effectors, higher frequencies of activated T cells, and lower frequencies of cells with markers of self-renewal. Additionally, a cluster of CD8+ T cells identified in HEI displayed gene profiles consistent with cytotoxic T lymphocytes and showed evidence for hyper expansion. Longitudinal phenotypic analysis revealed accelerated maturation of CD8+ T cells was maintained in HEI despite viral control. The results point to an HIV-directed immune response that is likely to influence reservoir establishment.

Maternal circadian rhythm disruption affects neonatal inflammation via metabolic reprograming of myeloid cells

Disruption of circadian rhythm during pregnancy produces adverse health outcomes in offspring; however, the role of maternal circadian rhythms in the immune system of infants and their susceptibility to inflammation remains poorly understood. Here we show that disruption of circadian rhythms in pregnant mice profoundly aggravates the severity of neonatal inflammatory disorders in both male and female offspring, such as necrotizing enterocolitis and sepsis. The diminished maternal production of docosahexaenoic acid (DHA) and the impaired immunosuppressive function of neonatal myeloid-derived suppressor cells (MDSCs) contribute to this phenomenon. Mechanistically, DHA enhances the immunosuppressive function of MDSCs via PPARγ-mediated mitochondrial oxidative phosphorylation. Transfer of MDSCs or perinatal supplementation of DHA relieves neonatal inflammation induced by maternal rhythm disruption. These observations collectively demonstrate a previously unrecognized role of maternal circadian rhythms in the control of neonatal inflammation via metabolic reprograming of myeloid cells.

In Utero Exposure to Antibiotics and Risk of Serious Infections in the First Year of Life

INTRODUCTION AND OBJECTIVE

Given the high prevalence of antibiotic prescription during pregnancy in France and previous studies suggesting an increased risk of infection in offspring with such exposures, our study aimed to investigate the association between prenatal exposure to systemic antibiotics and serious infections in full-term infants during their first year of life.

METHODS

We conducted a retrospective population-based cohort study on singleton, full-term liveborn non-immunocompromised infants, using the French National Health Data System (SNDS) between 2012 and 2021. Systemic antibiotic dispensing in ambulatory care settings during pregnancy defined the exposure. Outcomes concerned serious infections (i.e., infections requiring hospitalization) in offspring identified between 3 and 12 months of life, hence excluding infections of maternal origin. Adjusted odds ratios (aORs) were estimated using logistic regression with multivariate models to control for potential confounders.

RESULTS

Of 2,836,630 infants included, 39.6% were prenatally exposed to systemic antibiotics. Infants prenatally exposed to antibiotics had a higher incidence of serious infections compared with unexposed infants {aOR 1.12 [95% confidence interval (95% CI) 1.11-1.13]}. Similar associations were observed according to the timing of exposure during pregnancy, antibiotic class, and site of infections. The strongest association was observed when infants were prenatally exposed to three or more antibiotic courses during pregnancy [aOR 1.21 (95% CI 1.19-1.24)]. Limitations include residual confounders, such as genetic susceptibility to infections and the role of the underlying pathogen agent.

CONCLUSION

Prenatal exposure to systemic antibiotics is very common and is associated with a weak yet significant associations with subsequent serious infectious events during the first year of life. While our study revealed associations, it is important to note that causation cannot be established, given the acknowledged limitations, including potential confounding by indication.

Effect of Maternal Coronavirus Disease on Preterm Morbidities

OBJECTIVE

Coronavirus disease (COVID-19) during pregnancy may have an impact on preterm morbidities due to the inflammatory nature of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Exposure to intrauterine inflammation could result in adverse consequences in preterm infants. We aimed to determine the effect of maternal coronavirus disease on preterm morbidities at a tertiary neonatal intensive care unit.

STUDY DESIGN

This observational cohort study compared the clinical outcomes of preterm infants < 37 gestational weeks with and without maternal COVID-19. The study was conducted in a tertiary-level neonatal intensive care unit between March 2020 and December 2021. Demographics and clinical data of the study groups were collected from the medical files.

RESULTS

A total of 254 infants (127 in the maternal COVID-19 group and 127 in the control group) were included in the study. Respiratory distress syndrome, early and late neonatal sepsis, intraventricular hemorrhage, patent ductus arteriosus (PDA), necrotizing enterocolitis, bronchopulmonary dysplasia, and retinopathy of prematurity rates were similar between groups. In the subgroup analysis, the rate of PDA was significantly higher in preterm infants ≤1,500 g with maternal SARS-CoV-2 infection (38 vs. 15% p = 0.023). Presence of maternal COVID-19 was found to be an independent predictor for PDA in very low birthweight infants, as revealed by multivariate analyses (odds ratio: 3.4; 95% confidence interval: 1.12-10.4; p = 0.031). Mortality rates and duration of hospitalization were similar in both groups.

CONCLUSION

Our results suggest that COVID-19 infection during pregnancy seems to have no adverse effect on preterm morbidities and mortality. However, maternal COVID-19 was found to be a risk factor for PDA in preterm infants ≤1,500 g.

KEY POINTS

· The effect of maternal COVID-19 on preterm morbidities still has not well defined.. · Maternal COVID-19 seems to have no adverse effect on preterm morbidities and mortality.. · The exact impact of the COVID-19 on fetal/neonatal health is yet to be clarified..

Diverging patterns in innate immunity against respiratory viruses during a lifetime: lessons from the young and the old

Respiratory viral infections frequently lead to severe respiratory disease, particularly in vulnerable populations such as young children, individuals with chronic lung conditions and older adults, resulting in hospitalisation and, in some cases, fatalities. The innate immune system plays a crucial role in monitoring for, and initiating responses to, viruses, maintaining a state of preparedness through the constant expression of antimicrobial defence molecules. Throughout the course of infection, innate immunity remains actively involved, contributing to viral clearance and damage control, with pivotal contributions from airway epithelial cells and resident and newly recruited immune cells. In instances where viral infections persist or are not effectively eliminated, innate immune components prominently contribute to the resulting pathophysiological consequences. Even though both young children and older adults are susceptible to severe respiratory disease caused by various respiratory viruses, the underlying mechanisms may differ significantly. Children face the challenge of developing and maturing their immunity, while older adults contend with issues such as immune senescence and inflammaging. This review aims to compare the innate immune responses in respiratory viral infections across both age groups, identifying common central hubs that could serve as promising targets for innovative therapeutic and preventive strategies, despite the apparent differences in underlying mechanisms.

Vaccinomics and adversomics: key elements for a personalized vaccinology

Vaccines are one of the most important and effective tools in the prevention of infectious diseases and research about all the aspects of vaccinology are essential to increase the number of available vaccines more and more safe and effective. Despite the unquestionable value of vaccinations, vaccine hesitancy has spread worldwide compromising the success of vaccinations. Currently, the main purpose of vaccination campaigns is the immunization of whole populations with the same vaccine formulations and schedules for all individuals. A personalized vaccinology approach could improve modern vaccinology counteracting vaccine hesitancy and giving great benefits for human health. This ambitious purpose would be possible by facing and deepening the areas of vaccinomics and adversomics, two innovative areas of study investigating the role of a series of variables able to influence the immune response to vaccinations and the development of serious side effects, respectively. We reviewed the recent scientific knowledge about these innovative sciences focusing on genetic and non-genetic basis involved in the individual response to vaccines in terms of both immune response and side effects.

SARS-CoV-2-specific mucosal immune response in vaccinated versus infected children

The anti-COVID-19 intramuscular vaccination induces a strong systemic but a weak mucosal immune response in adults. Little is known about the mucosal immune response in children infected or vaccinated against SARS-CoV-2. We found that 28% of children had detectable salivary IgA against SARS-CoV-2 even before vaccination, suggesting that, in children, SARS-CoV-2 infection may be undiagnosed. After vaccination, only receptor-binding domain (RBD)-specific IgA1 significantly increased in the saliva. Conversely, infected children had significantly higher salivary RBD-IgA2 compared to IgA1, indicating that infection more than vaccination induces a specific mucosal immune response in children. Future efforts should focus on development of vaccine technologies that also activate mucosal immunity.

Ion channel TRPV2 is critical in enhancing B cell activation and function

The function of transient receptor potential vanilloid (TRPV) cation channels governing B cell activation remains to be explored. We present evidence that TRPV2 is highly expressed in B cells and plays a crucial role in the formation of the B cell immunological synapse and B cell activation. Physiologically, TRPV2 expression level is positively correlated to influenza-specific antibody production and is low in newborns and seniors. Pathologically, a positive correlation is established between TRPV2 expression and the clinical manifestations of systemic lupus erythematosus (SLE) in adult and child SLE patients. Correspondingly, mice with deficient TRPV2 in B cells display impaired antibody responses following immunization. Mechanistically, the pore and N-terminal domains of TRPV2 are crucial for gating cation permeation and executing mechanosensation in B cells upon antigen stimulation. These processes synergistically contribute to membrane potential depolarization and cytoskeleton remodeling within the B cell immunological synapse, fostering efficient B cell activation. Thus, TRPV2 is critical in augmenting B cell activation and function.

Life-threatening infections in human newborns: Reconciling age-specific vulnerability and interindividual variability

In humans, the interindividual variability of clinical outcome following exposure to a microorganism is immense, ranging from silent infection to life-threatening disease. Age-specific immune responses partially account for the high incidence of infection during the first 28 days of life and the related high mortality at population level. However, the occurrence of life-threatening disease in individual newborns remains unexplained. By contrast, inborn errors of immunity and their immune phenocopies are increasingly being discovered in children and adults with life-threatening viral, bacterial, mycobacterial and fungal infections. There is a need for convergence between the fields of neonatal immunology, with its in-depth population-wide characterization of newborn-specific immune responses, and clinical immunology, with its investigations of infections in patients at the cellular and molecular levels, to facilitate identification of the mechanisms of susceptibility to infection in individual newborns and the design of novel preventive and therapeutic strategies.

Clinical chorioamnionitis at term: definition, pathogenesis, microbiology, diagnosis, and treatment

Clinical chorioamnionitis, the most common infection-related diagnosis in labor and delivery units, is an antecedent of puerperal infection and neonatal sepsis. The condition is suspected when intrapartum fever is associated with two other maternal and fetal signs of local or systemic inflammation (eg, maternal tachycardia, uterine tenderness, maternal leukocytosis, malodorous vaginal discharge or amniotic fluid, and fetal tachycardia). Clinical chorioamnionitis is a syndrome caused by intraamniotic infection, sterile intraamniotic inflammation (inflammation without bacteria), or systemic maternal inflammation induced by epidural analgesia. In cases of uncertainty, a definitive diagnosis can be made by analyzing amniotic fluid with methods to detect bacteria (Gram stain, culture, or microbial nucleic acid) and inflammation (white blood cell count, glucose concentration, interleukin-6, interleukin-8, matrix metalloproteinase-8). The most common microorganisms are Ureaplasma species, and polymicrobial infections occur in 70% of cases. The fetal attack rate is low, and the rate of positive neonatal blood cultures ranges between 0.2% and 4%. Intrapartum antibiotic administration is the standard treatment to reduce neonatal sepsis. Treatment with ampicillin and gentamicin have been recommended by professional societies, although other antibiotic regimens, eg, cephalosporins, have been used. Given the importance of Ureaplasma species as a cause of intraamniotic infection, consideration needs to be given to the administration of antimicrobial agents effective against these microorganisms such as azithromycin or clarithromycin. We have used the combination of ceftriaxone, clarithromycin, and metronidazole, which has been shown to eradicate intraamniotic infection with microbiologic studies. Routine testing of neonates born to affected mothers for genital mycoplasmas could improve the detection of neonatal sepsis. Clinical chorioamnionitis is associated with decreased uterine activity, failure to progress in labor, and postpartum hemorrhage; however, clinical chorioamnionitis by itself is not an indication for cesarean delivery. Oxytocin is often administered for labor augmentation, and it is prudent to have uterotonic agents at hand to manage postpartum hemorrhage. Infants born to mothers with clinical chorioamnionitis near term are at risk for early-onset neonatal sepsis and for long-term disability such as cerebral palsy. A frontier is the noninvasive assessment of amniotic fluid to diagnose intraamniotic inflammation with a transcervical amniotic fluid collector and a rapid bedside test for IL-8 for patients with ruptured membranes. This approach promises to improve diagnostic accuracy and to provide a basis for antimicrobial administration.

Role of innate T cells in necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a destructive gastrointestinal disease primarily affecting preterm babies. Despite advancements in neonatal care, NEC remains a significant cause of morbidity and mortality in neonatal intensive care units worldwide and the etiology of NEC is still unclear. Risk factors for NEC include prematurity, very low birth weight, feeding with formula, intestinal dysbiosis and bacterial infection. A review of the literature would suggest that supplementation of prebiotics and probiotics prevents NEC by altering the immune responses. Innate T cells, a highly conserved subpopulation of T cells that responds quickly to stimulation, develops differently from conventional T cells in neonates. This review aims to provide a succinct overview of innate T cells in neonates, encompassing their phenotypic characteristics, functional roles, likely involvement in the pathogenesis of NEC, and potential therapeutic implications.

An IL-10/DEL-1 axis supports granulopoiesis and survival from sepsis in early life

The limited reserves of neutrophils are implicated in the susceptibility to infection in neonates, however the regulation of neutrophil kinetics in infections in early life remains poorly understood. Here we show that the developmental endothelial locus (DEL-1) is elevated in neonates and is critical for survival from neonatal polymicrobial sepsis, by supporting emergency granulopoiesis. Septic DEL-1 deficient neonate mice display low numbers of myeloid-biased multipotent and granulocyte-macrophage progenitors in the bone marrow, resulting in neutropenia, exaggerated bacteremia, and increased mortality; defects that are rescued by DEL-1 administration. A high IL-10/IL-17A ratio, observed in newborn sepsis, sustains tissue DEL-1 expression, as IL-10 upregulates while IL-17 downregulates DEL-1. Consistently, serum DEL-1 and blood neutrophils are elevated in septic adult and neonate patients with high serum IL-10/IL-17A ratio, and mortality is lower in septic patients with high serum DEL-1. Therefore, IL-10/DEL-1 axis supports emergency granulopoiesis, prevents neutropenia and promotes sepsis survival in early life.

Fetal CCL2 signaling mediates offspring social behavior and recapitulates effects of prenatal stress

Maternal stress during pregnancy is prevalent and associated with increased risk of neurodevelopmental disorders in the offspring. Maternal and offspring immune dysfunction has been implicated as a potential mechanism by which prenatal stress shapes offspring neurodevelopment; however, the impact of prenatal stress on the developing immune system has yet to be elucidated. Furthermore, there is evidence that the chemokine C-C motif chemokine ligand 2 (CCL2) plays a key role in mediating the behavioral sequelae of prenatal stress. Here, we use an established model of prenatal restraint stress in mice to investigate alterations in the fetal immune system, with a focus on CCL2. In the placenta, stress led to a reduction in CCL2 and Ccr2 expression with a concomitant decrease in leukocyte number. However, the fetal liver exhibited an inflammatory phenotype, with upregulation of Ccl2, Il6, and Lbp expression, along with an increase in pro-inflammatory Ly6CHi monocytes. Prenatal stress also disrupted chemokine signaling and increased the number of monocytes and microglia in the fetal brain. Furthermore, stress increased Il1b expression by fetal brain CD11b+ microglia and monocytes. Finally, intra-amniotic injections of recombinant mouse CCL2 partially recapitulated the social behavioral deficits in the adult offspring previously observed in the prenatal restraint stress model. Altogether, these data suggest that prenatal stress led to fetal inflammation, and that fetal CCL2 plays a role in shaping offspring social behavior.