Does IVIg administration yield improved immune function in very premature neonates?

Intravenous Immune Globulin Uses in the Fetus and Neonate: A Review

Intravenous immune globulin (IVIG) is made after processing plasma from healthy donors. It is composed mainly of pooled immunoglobulin and has clinical evidence-based applications in adult and pediatric populations. Recently, several clinical applications have been proposed for managing conditions in the neonatal population, such as hemolytic disease of the newborn, treatment, and prophylaxis for sepsis in high-risk neonates, enterovirus parvovirus and COVID-19 related neonatal infections, fetal and neonatal immune-induced thrombocytopenia, neonatal hemochromatosis, neonatal Kawasaki disease, and some types of immunodeficiency. The dosing, mechanism of action, effectiveness, side effects, and adverse reactions of IVIG have been relatively well studied in adults but are not well described in the neonatal population. This review aims to provide the most recent evidence and consensus guidelines about the use of IVIG in the fetus and neonate.

Fetal and neonatal allo-immune response

The components of the immune system may be present in early stages of embryonic and then fetal, then they reach maturity at different stages of pregnancy. Just as the growth and development of the components of the embryonic and then fetal immune system progressively mature, functions are acquired sequentially during the course of pregnancy, both the ability to mount a cell-mediated or antibody-mediated immune response and the tolerance towards a certain group of antigens. The fetus is immunocompetent because during this development, it acquires the ability to generate an immune response. As development takes place, the fetus also generates specific tolerance as it is exposed to genetically foreign and non-inherited maternal antigens. Nonetheless, the fetal immune system does not attack nor harm maternal tissues. At birth, the immune system, although developed, is not mature enough yet. Furthermore, passive transfer of maternal antibodies creates a unique scenario of compatibility that cannot be seen in children or adults. Recent advances in knowledge of fetal and neonatal immunology make it possible to recognize the risks associated with transfusion and how to resolve them.

Why are preterm newborns at increased risk of infection?

One in 10 newborns will be born before completion of 36 weeks' gestation (premature birth). Infection and sepsis in preterm infants remain a significant clinical problem that represents a substantial financial burden on the healthcare system. Many factors predispose premature infants for having the greatest risk of developing and succumbing to infection as compared with all other age groups across the age spectrum. It is clear that the immune system of preterm infants exhibits distinct, rather than simply deficient, function as compared with more mature and older humans and that the immune function in preterm infants contributes to infection risk. While no single review can cover all aspects of immune function in this population, we will discuss key aspects of preterm neonatal innate and adaptive immune function that place them at high risk for developing infections and sepsis, as well as sepsis-associated morbidity and mortality.

Impact of Immunoglobulin Therapy in Pediatric Disease: a Review of Immune Mechanisms

Intravenous immunoglobulin (IVIG) provides replacement therapy in immunodeficiency and immunomodulatory therapy in inflammatory and autoimmune diseases. This paper describes the immune mechanisms underlying six major non-primary immunodeficiency pediatric diseases and the diverse immunomodulatory functions of IVIG therapy. In Kawasaki disease, IVIG plays a major, proven, and effective role in decreasing aneurysm formation, which represents an aberrant inflammatory response to an infectious trigger in a genetically predisposed individual. In immune thrombocytopenia, IVIG targets the underlying increased platelet destruction and decreased platelet production. Although theoretically promising, IVIG shows no clear clinical benefit in the prophylaxis and treatment of neonatal sepsis. Limitations in research design combined with the unique neonatal immunologic environment offer explanations for this finding. Inflammation from aberrant immune activation underlies the myelinotoxic effects of Guillain-Barré syndrome. HIV-1 exerts a broad range of immunologic effects and was found to decrease serious bacterial infections in the pre-highly active anti-retroviral therapy (HAART) era, although its practical relevance in the post-HAART era has waned. Clinical and experimental data support the role of immune mechanisms in the pathogenesis of childhood epilepsy. IVIG exerts anti-epileptic effects through targeting upregulated cytokine pathways and antibodies thought to contribute to epilepsy. Applications in six additional pediatric diseases including pediatric asthma, atopic dermatitis, cystic fibrosis, pediatric autoimmune neuropsychiatric disorders associated with streptococcal infection (PANDAS), autism, and transplantation will also be briefly reviewed. From autoimmunity to immunodeficiency, a dynamic immunologic basis underlies major pediatric diseases and highlights the broad potential of IVIG therapy.

Matrix Metalloproteinase-8 Augments Bacterial Clearance in a Juvenile Sepsis Model

Genetic ablation or pharmacologic inhibition of matrix metalloproteinase-8 (MMP8) improves survival in an adult murine sepsis model. Because developmental age influences the host inflammatory response, we hypothesized that developmental age influences the role of MMP8 in sepsis. First, we compared sepsis survival between wild type (WT, C57BL/6) and MMP8 null juvenile-aged mice (12-14 days) after intraperitoneal injection of a standardized cecal slurry. Second, peritoneal lavages collected at 6 and 18 hours after cecal slurry injection were analyzed for bacterial burden, leukocyte subsets, and inflammatory cytokines. Third, juvenile WT mice were pretreated with an MMP8 inhibitor prior to cecal slurry injection; analysis of their bacterial burden was compared to vehicle-injected animals. Fourth, the phagocytic capacity of WT and MMP8 null peritoneal macrophages was compared. Finally, peritoneal neutrophil extracellular traps (NETs) were compared using immunofluorescent imaging and quantitative image analysis. We found that juvenile MMP8 null mice had greater mortality and higher bacterial burden than WT mice. Leukocyte counts and cytokine concentrations in the peritoneal fluid were increased in the MMP8 null mice, relative to the wild type mice. Peritoneal macrophages from MMP8 null mice had reduced phagocytic capacity compared to WT macrophages. There was no quantitative difference in NET formation, but fewer bacteria were adherent to NETs from MMP8 null animals. In conclusion, in contrast to septic adult mice, genetic ablation of MMP8 increased mortality following bacterial peritonitis in juvenile mice. The increase in mortality in MMP8 null juvenile mice was associated with reduced bacterial clearance and reduced NET efficiency. We conclude that developmental age influences the role of MMP8 in sepsis.

Role of innate immunity in neonatal infection

Newborns are at increased risk of infection due to genetic, epigenetic, and environmental factors. Herein we examine the roles of the neonatal innate immune system in host defense against bacterial and viral infections. Full-term newborns express a distinct innate immune system biased toward T(H)2-/T(H)17-polarizing and anti-inflammatory cytokine production with relative impairment in T(H)1-polarizing cytokine production that leaves them particularly vulnerable to infection with intracellular pathogens. In addition to these distinct features, preterm newborns also have fragile skin, impaired T(H)17-polarizing cytokine production, and deficient expression of complement and of antimicrobial proteins and peptides (APPs) that likely contribute to susceptibility to pyogenic bacteria. Ongoing research is identifying APPs, including bacterial/permeability-increasing protein and lactoferrin, as well as pattern recognition receptor agonists that may serve to enhance protective newborn and infant immune responses as stand-alone immune response modifiers or vaccine adjuvants.

Intravenous immunoglobulin (IVIg) for refractory and difficult-to-treat infections

Traditionally, intravenous immunoglobulin (IVIg) has been used as replacement therapy for patients with primary or secondary immunoglobulin deficiencies. Increasingly, IVIg is being used (in doses higher than for replacement therapy) in certain bacterial or viral infectious diseases. A variety of modes of action have been attributed to the beneficial effects of IVIg, including its interaction with T-cell function, antigen-presenting cell maturation/presentation, combined with a general "tune down" effect on inflammatory reactions. More often, IVIg is being evaluated in clinical trials for the treatment of refractory and difficult-to-treat chronic infections. The evidence, molecular mechanisms, and rationale for the use of adjunct IVIg therapy in infectious diseases are reviewed, and its potential use in the adjunct treatment of difficult-to-treat drug-resistant tuberculosis discussed.

Evolutionary-developmental perspectives on immune system interactions among the pregnant woman, placenta, and fetus, and responses to sexually transmitted infectious agents

A balance has evolved over deep time between the various immune systems of the "triad" that is linked together for a short period: the pregnant woman, the fetus, and the placenta. This balance is affected by, and helps to determine, the immune responses to maternal infectious agents that may be transmitted to the fetus/infant transplacentally, intrapartum, or via breast milk. This review identifies newer evolutionary concepts and processes related particularly to the human placenta, innate and adaptive immune systems involved in tolerance, and in responses to sexually transmitted infectious (STI) agents that may be pathogenic to the fetus/infant at different gestational periods and in the first year of life. An evolutionary-developmental (EVO-DEVO) perspective has been applied to the complexities within, and among, the different actors and their beneficial or deleterious outcomes. Such a phylogenetic and ontogenic approach has helped to stimulate several basic questions and suggested possible explanations and novel practical interventions.

The influence of developmental age on the early transcriptomic response of children with septic shock

Septic shock is a frequent and costly problem among patients in the pediatric intensive care unit (PICU) and is associated with high mortality and devastating survivor morbidity. Genome-wide expression patterns can provide molecular granularity of the host response and offer insight into why large variations in outcomes exist. We derived whole-blood genome-wide expression patterns within 24 h of PICU admission from children with septic shock. We compared the transcriptome between septic shock developmental-age groups defined as neonates (≤ 28 d, n = 17), infants (1 month to 1 year, n = 62), toddlers (2-5 years, n = 54) and school-age (≥ 6 years, n = 47) and age-matched controls. Direct intergroup comparisons demonstrated profound changes in neonates, relative to older children. Neonates with septic shock demonstrated reduced expression of genes representing key pathways of innate and adaptive immunity. In contrast to the largely upregulated transcriptome in all other groups, neonates exhibited a predominantly downregulated transcriptome when compared with controls. Neonates and school-age subjects had the most uniquely regulated genes relative to controls. Age-specific studies of the host response are necessary to identify developmentally relevant translational opportunities that may lead to improved sepsis outcomes.

Procession to pediatric bacteremia and sepsis: covert operations and failures in diplomacy

Despite advances in diagnosis and treatment, bacterial sepsis remains a major cause of pediatric morbidity and mortality, particularly among neonates, the critically ill, and the growing immunocompromised patient population. Sepsis is the end point of a complex and dynamic series of events in which both host and microbial factors drive high morbidity and potentially lethal physiologic alterations. In this article we provide a succinct overview of the events that lead to pediatric bloodstream infections (BSIs) and sepsis, with a focus on the molecular mechanisms used by bacteria to subvert host barriers and local immunity to gain access to and persist within the systemic circulation. In the events preceding and during BSI and sepsis, Gram-positive and Gram-negative pathogens use a battery of factors for translocation, inhibition of immunity, molecular mimicry, intracellular survival, and nutrient scavenging. Gaps in understanding the molecular pathogenesis of bacterial BSIs and sepsis are highlighted as opportunities to identify and develop new therapeutics.