TRIF-dependent innate immune activation is critical for survival to neonatal gram-negative sepsis

B Cells Induce Early-Onset Maternal Inflammation to Protect against LPS-Induced Fetal Rejection

The maternal balance between B regulatory (Breg) cells and inflammatory B cells is of central importance for protection against preterm birth (PTB). However, the impact of B cell signaling in early maternal and fetal immune responses on inflammatory insults remains underinvestigated. To understand which role B cells and B-cell-specific signaling play in the pathogenesis of PTB, the later was induced by an injection of LPS in B cell-sufficient WT mice, CD19-/-, BMyD88-/- and µMT murine dams at gestational day 16 (gd 16). WT dams developed a strong inflammatory response in their peritoneal cavity (PC), with an increased infiltration of granulocytes and enhanced IL-6, TNF-α, IL-17 and MCP-1 levels. However, they demonstrated a reduced NOS2 expression of PC macrophages 4 h after the LPS injection. Simultaneously, LPS-challenged WT dams upregulated pregnancy-protective factors like IL-10 and TARC. The concentrations of inflammatory mediators in the placental supernatants, amniotic fluids, fetal serums and gestational tissues were lower in LPS-challenged WT dams compared to CD19-/-, BMyD88-/- and µMT dams, thereby protecting WT fetuses from being born preterm. B cell deficiency, or the loss of B-cell-specific CD19 or MyD88 expression, resulted in an early shift from immune regulation towards inflammation at the fetomaternal interface and fetuses, resulting in PTB.

The Role of the Spleen and the Place of Splenectomy in Autoimmune Hemolytic Anemia-A Review of Current Knowledge

Autoimmune hemolytic anemia (AIHA) is a rare, very heterogeneous, and sometimes life-threatening acquired hematologic disease characterized by increased red blood cell (RBC) destruction by autoantibodies (autoAbs), either with or without complement involvement. Recent studies have shown that the involvement of T- and B-cell dysregulation and an imbalance of T-helper 2 (Th2) and Th17 phenotypes play major roles in the pathogenesis of AIHA. AIHA can be primary (idiopathic) but is more often secondary, triggered by infections or drug use or as a part of other diseases. As the location of origin of autoAbs and the location of autoAb-mediated RBC clearance, as well as the location of extramedullary hematopoiesis, the spleen is crucially involved in all the steps of AIHA pathobiology. Splenectomy, which was the established second-line therapeutic option in corticosteroid-resistant AIHA patients for decades, has become less common due to increasing knowledge of immunopathogenesis and the introduction of targeted therapy. This article provides a comprehensive overview of current knowledge regarding the place of the spleen in the immunological background of AIHA and the rapidly growing spectrum of novel therapeutic approaches. Furthermore, this review emphasizes the still-existing expediency of laparoscopic splenectomy with appropriate perioperative thromboprophylaxis and the prevention of infection as a safe and reliable therapeutic option in the context of the limited availability of rituximab and other novel therapies.

Epigenomic and transcriptomic analyses reveal differences between low-grade inflammation and severe exhaustion in LPS-challenged murine monocytes

Emerging studies suggest that monocytes can be trained by bacterial endotoxin to adopt distinct memory states ranging from low-grade inflammation to immune exhaustion. While low-grade inflammation may contribute to the pathogenesis of chronic diseases, exhausted monocytes with pathogenic and immune-suppressive characteristics may underlie the pathogenesis of polymicrobial sepsis including COVID-19. However, detailed processes by which the dynamic adaption of monocytes occur remain poorly understood. Here we exposed murine bone-marrow derived monocytes to chronic lipopolysaccharide (LPS) stimulation at low-dose or high-dose, as well as a PBS control. The cells were profiled for genome-wide H3K27ac modification and gene expression. The gene expression of TRAM-deficient and IRAK-M-deficient monocytes with LPS exposure was also analyzed. We discover that low-grade inflammation preferentially utilizes the TRAM-dependent pathway of TLR4 signaling, and induces the expression of interferon response genes. In contrast, high dose LPS uniquely upregulates exhaustion signatures with metabolic and proliferative pathways. The extensive differences in the epigenomic landscape between low-dose and high-dose conditions suggest the importance of epigenetic regulations in driving differential responses. Our data provide potential targets for future mechanistic or therapeutic studies.

BCG vaccination-induced emergency granulopoiesis provides rapid protection from neonatal sepsis

Death from sepsis in the neonatal period remains a serious threat for millions. Within 3 days of administration, bacille Calmette-Guérin (BCG) vaccination can reduce mortality from neonatal sepsis in human newborns, but the underlying mechanism for this rapid protection is unknown. We found that BCG was also protective in a mouse model of neonatal polymicrobial sepsis, where it induced granulocyte colony-stimulating factor (G-CSF) within hours of administration. This was necessary and sufficient to drive emergency granulopoiesis (EG), resulting in a marked increase in neutrophils. This increase in neutrophils was directly and quantitatively responsible for protection from sepsis. Rapid induction of EG after BCG administration also occurred in three independent cohorts of human neonates.

Aluminum Adjuvant Improves Survival Via NLRP3 Inflammasome and Myeloid Non-Granulocytic Cells in a Murine Model of Neonatal Sepsis

ABSTRACT

Neonatal sepsis leads to significant morbidity and mortality with the highest risk of death occurring in preterm (<37 weeks) and low birth weight (<2,500 g) infants. The neonatal immune system is developmentally immature with well-described defects in innate and adaptive immune responses. Immune adjuvants used to enhance the vaccine response have emerged as potential therapeutic options, stimulating non-specific immunity and preventing sepsis mortality. Aluminum salts ("alum") have been used as immune adjuvants for over a century, but their mechanism of action remains poorly understood. This study aims to identify potential mechanisms by which pretreatment with alum induces host protective immunity to polymicrobial sepsis in neonatal mice. Utilizing genetic and cell-depletion studies, we demonstrate here that the prophylactic administration of aluminum adjuvants in neonatal mice improves sepsis survival via activation of the nucleotide oligomerization domain-like receptor family, pyrin-domain-containing 3 inflammasome and dendritic cell activation. Furthermore, this beneficial effect is dependent on myeloid, non-granulocytic Gr1-positive cells, and MyD88-signaling pathway activation. These findings suggest a promising therapeutic role for aluminum-based vaccine adjuvants to prevent development of neonatal sepsis and improve mortality in this highly vulnerable population.

Cecal Slurry Injection in Neonatal and Adult Mice

Studying the pathophysiology of sepsis still requires animal models, and the mouse remains the most commonly used species. Here we discuss the "cecal slurry" (CS) model of polymicrobial, peritoneal sepsis and compare and contrast it to other commonly used methods. Among the different murine models of sepsis, cecal ligation and puncture (CLP), and not the CS, is often considered the "gold standard" to induce polymicrobial sepsis in laboratory animals. CLP is a well-described model involving a simple surgical procedure that closely mimics the clinical course of intra-abdominal sepsis. However, CLP may not be an option for experiments involving newborn pups, where the cecum is indistinguishable from small bowel, where differences in microbiome content may affect the experiment, or where surgical procedures/anesthesia exposure needs to be limited. An important alternative method is the CS model, involving the intraperitoneal injection of cecal contents from a donor animal into the peritoneal cavity of a recipient animal to induce polymicrobial sepsis. Furthermore, CS is an effective alternative model of intraperitoneal polymicrobial sepsis in adult mice and can now be considered the "gold standard" for experiments in neonatal mice.

The Role of Iron in the Susceptibility of Neonatal Mice to Escherichia coli K1 Sepsis

Sepsis from Escherichia coli expressing the K1 antigen is a leading cause of death in neonates. In a murine model, E. coli K1 grew rapidly in the peritoneal cavity of neonatal mice, causing fatal disease. In contrast, adult mice cleared the infection. Neonatal mice mounted a rapid and equivalent antimicrobial immune response compared to adult mice. Interestingly, peritoneal fluid from neonatal mice contained significantly more total iron than that of adult mice, which was sufficient to support enhanced E. coli growth. Transient iron overload in adult mice infected with E. coli resulted in 100% mortality. Maternal diet-induced mild iron deficiency decreased offspring peritoneal iron, decreased bacterial growth, and conferred protection against sepsis. Taken together, neonatal susceptibility to E. coli K1 sepsis is enhanced by a localized excess of peritoneal iron that allows for unchecked bacterial growth. Targeting this excess iron may provide a new therapeutic target in human patients.

C23, an oligopeptide derived from cold-inducible RNA-binding protein, suppresses inflammation and reduces lung injury in neonatal sepsis

INTRODUCTION

Neonatal sepsis remains a leading cause of infant mortality. Cold-inducible RNA binding protein (CIRP) is an inflammatory mediator that induces TNF-α production in macrophages. C23 is a CIRP-derived peptide that blocks CIRP from binding its receptor. We therefore hypothesized that treatment with C23 reduces systemic inflammation and protects the lungs in neonatal sepsis.

METHODS

Sepsis was induced in C56BL/6 mouse pups (5-7 days) by intraperitoneal injection of adult cecal slurry (0.525 mg/g body weight, LD₁₀₀). One hour later pups received retroorbital injection of C23 (8 mg/kg) or vehicle (normal saline). Ten hours after sepsis induction, blood and tissues were collected for analysis.

RESULTS

C23 treatment resulted in a 58% and 69% reduction in serum levels of proinflammatory cytokines IL-6 and IL-1β, respectively, and a 40% and 45% reduction of AST and LDH, as compared to vehicle-treated septic pups. In the lungs, C23 treatment reduced expression of cytokines IL-6 and IL-1β by 78% and 74%. In addition, the mRNA level of neutrophil chemoattractants KC and MIP-2 was reduced by 84% and 74%, respectively. These results corresponded to a reduction in histologic lung injury score. Vehicle-treated pups scored 0.49 ± 0.19, while C23 treatment reduced scores to 0.29 ± 0.12 (p < 0.05; Max = 1). Apoptosis in the lungs, measured by TUNEL assay, was also decreased by 53% with C23 treatment (p < 0.05).

CONCLUSIONS

Inhibition of CIRP with C23 treatment is protective in septic neonatal mice as demonstrated by reduced inflammatory markers systemically and in the lung. Therefore, C23 has promising therapeutic potential in treatment of neonatal sepsis.

LEVEL OF EVIDENCE

Level I.

Nested case-control study of multiple serological indexes and Brighton pediatric early warming score in predicting death of children with sepsis

BACKGROUND

Currently, it is difficult to predict the complications of children at the early stage of sepsis. Brighton pediatric early warning score (PEWS) is a disease risk assessment system that is simple and easy to operate, which has good sensitivity and specificity in disease recognition among children. Because detection indicators vary widely in children, a single indicator is difficult to assess the post-treatment status of children with sepsis.

AIM

To investigate the relationship between serological markers, Brighton PEWS, and death in children with sepsis after treatment.

METHODS

A total of 205 children diagnosed with sepsis at our hospital were enrolled. The baseline data, serum scores, and PEWS scores were recorded. In the nested case-control study, children who died during the study period were included in an observation group. According to the matching principle, the children who were not dead in the same cohort were included in a control group. The influencing factors of death in children with sepsis after treatment and the value of each evaluation index in predicting the prognosis of children were analyzed.

RESULTS

A total of 96 children were enrolled in the study, including 48 each in the observation group and the control group. Multivariate logistic regression analysis indicated that antibacterial treatments within 1 h (P = 0.017), shock (P = 0.044), multiple organ dysfunction syndrome (MODS) (P = 0.027), serum procalcitonin (PCT) (P = 0.047), serum albumin (ALB) (P = 0.024), and PEWS (P = 0.012) were independent risk factors for the death of children with sepsis. The area under the curve of the combination of ALB, PCT, and PEWS to predict the death in children with sepsis was the highest (0.908).

CONCLUSION

Antibacterial treatments within 1 h, shock, MODS, PCT, ALB, and PEWS are independent risk factors for the death of children with sepsis. The predictive accuracy of the combination of PCT, ALB, and PEWS for the prognosis of children with sepsis is the best.

Sepsis Upregulates CD14 Expression in a MyD88-Dependent and Trif-Independent Pathway

An overwhelming immune response, particularly from macrophages, plays a critical role in survival and organ damage in sepsis patients. Toll-like receptors (TLRs) are important receptors to recognize the conserved motifs expressed by invading bacteria. The TLRs except TLR3 signal via a MyD88-dependent pathway. TLR3 uses a TRIF-dependent pathway, while TLR4 uses both MyD88 and TRIF-dependent pathways. Previous studies indicated that CD14 was necessary for TLRs-dependent production of pro-inflammatory cytokines. Blocking CD14 protected against the deleterious systemic inflammatory response associated with sepsis. The aim of this study was to determine the signaling pathway of TLR activation-induced CD14 expression in models of polymicrobial sepsis and in peritoneal macrophages. We found that CD14 expression was upregulated in the lung, liver, and kidney of septic mice induced by cecal ligation puncture. In cultured peritoneal macrophages, specific agonists for all TLRs, except for TLR3, increased CD14 expression. Lipopolysaccharide-induced upregulation of CD14 was abolished in peritoneal macrophages from MyD88 KO mice but increased in TRIF inhibitor, resveratrol pretreated wild-type macrophages. Moreover, MyD88 KO, but not TRIF KO mice, showed a decreased CD14 expression in the tissue of septic mice, which was associated with a strongly attenuated inflammatory response and increased survival rate. These data suggest that a MyD88-dependent and TRIF-independent pathway of TLR is activated in upregulating CD14 expression under septic conditions. This study deciphers a critical cross-talk between TLRs and CD14.

Impact of toll-like receptor 4 stimulation on human neonatal neutrophil spontaneous migration, transcriptomics, and cytokine production

Neonates rely on their innate immune system, and neutrophils in particular, to recognize and combat life-threatening bacterial infections. Pretreatment with lipopolysaccharide (LPS), a toll-like receptor (TLR) 4 agonist, improves survival to polymicrobial sepsis in neonatal mice by enhancing neutrophil recruitment. To understand the response of human neonatal neutrophils to TLR4 stimulation, ex vivo spontaneous neutrophil migration, neutrophil transcriptomics, and cytokine production in the presence and absence of LPS were measured directly from whole blood of adults, term neonates, and preterm neonates. Spontaneous neutrophil migration was measured on novel microfluidic devices with time-lapse imaging for 10 h. Genome-wide neutrophil transcriptomics and plasma cytokine concentrations were also determined. Preterm neonates had significantly fewer spontaneously migrating neutrophils at baseline, and both term and preterm neonates had decreased neutrophil velocity, compared to adults. In the presence of LPS stimulation, the number of spontaneously migrating neutrophils was reduced in preterm neonates compared to term neonates and adults. Neutrophil velocity was not significantly different among groups with LPS stimulation. Preterm neonates upregulated expression of genes associated with the recruitment and response of neutrophils following LPS stimulation, but failed to upregulate the expression of genes associated with antimicrobial and antiviral responses. Plasma levels of IL-1β, IL-6, IL-8, MIP-1α, and TNF-α increased in response to LPS stimulation in all groups, but IL-10 was increased only in term and preterm neonates. In conclusion, age-specific changes in spontaneous neutrophil migration counts are not affected by LPS despite changes in gene expression and cytokine production.

KEY MESSAGES

Preterm neonates have reduced spontaneous neutrophil migration compared to term neonates and adults in the absence and presence of TLR4 stimulation. Preterm and term neonates have reduced neutrophil velocities compared to adults in the absence of TLR4 stimulation but no difference in the presence of TLR4 stimulation. Unique transcriptomic response to TLR4 stimulation is observed in neutrophils from preterm neonates, term neonates, and adults. TLR4 stimulation produces an age-specific cytokine response.

Outgrowing the Immaturity Myth: The Cost of Defending From Neonatal Infectious Disease

Newborns suffer high rates of mortality due to infectious disease-this has been generally regarded to be the result of an "immature" immune system with a diminished disease-fighting capacity. However, the immaturity dogma fails to explain (i) greater pro-inflammatory responses than adults in vivo and (ii) the ability of neonates to survive a significantly higher blood pathogen burden than of adults. To reconcile the apparent contradiction of clinical susceptibility to disease and the host immune response findings when contrasting newborn to adult, it will be essential to capture the entirety of available host-defense strategies at the newborn's disposal. Adults focus heavily on the disease resistance approach: pathogen reduction and elimination. Newborn hyperactive innate immunity, sensitivity to immunopathology, and the energetic requirements of growth and development (immune and energy costs), however, preclude them from having an adult-like resistance response. Instead, newborns also may avail themselves of disease tolerance (minimizing immunopathology without reducing pathogen load), as a disease tolerance approach provides a counterbalance to the dangers of a heightened innate immunity and has lower-associated immune costs. Further, disease tolerance allows for the establishment of a commensal bacterial community without mounting an unnecessarily dangerous immune resistance response. Since disease tolerance has its own associated costs (immune suppression leading to unchecked pathogen proliferation), it is the maintenance of homeostasis between disease tolerance and disease resistance that is critical to safe and effective defense against infections in early life. This paradigm is consistent with nearly all of the existing evidence.

Newborn susceptibility to infection vs. disease depends on complex in vivo interactions of host and pathogen

The burden of newborn infectious disease has long been recognized as the highest across the entire human life span. The precise underlying cause is unfortunately still far from clear. A substantial body of data derived mostly from in vitro experimentation indicates "lower" host immune responses in early vs. adult life and is briefly summarized within this review. However, emerging data derived mostly from in vivo experimentation reveal that the newborn host also exhibits an exuberant immune and inflammatory response following infection when compared to the adult. In this context, it is important to emphasize that "infection" does not equate "infectious disease," as for many infections it is the host response to the infection that causes disease. This simple insight readily arranges existing evidence into cause-effect relationships that explain much of the increase in clinical suffering from infection in early life. We here briefly summarize the evidence in support of this paradigm and highlight the important implications it has for efforts to ameliorate the suffering and dying from infection in early life.

STING and TRIF Contribute to Mouse Sepsis, Depending on Severity of the Disease Model

IFN regulatory factor (IRF)3 plays a detrimental role in the cecal ligation and puncture (CLP) mouse model of sepsis. However, it is unclear which pathway activates IRF3 in this context. In this report, we investigate two pathways that activate IRF3: the Stimulator of Interferon Genes (STING) pathway (that senses cytosolic DNA) and the TIR-domain-containing adapter-inducing interferon-β (TRIF) pathway (that senses dsRNA and LPS via Toll-like receptor 3 and 4). Initially, we examine the impact of these pathways using a severe CLP model (∼90% mortality). Both STING-KO and TRIF-KO mice are protected from severe sepsis, exhibiting reduced mortality, disease score, hypothermia, and inflammatory cytokines relative to WT counterparts. STING/TRIF-DKO mice exhibit a similar phenotype to each of the single KO strains, suggesting that these pathways have an interrelated function. Subsequently, we examine the impact of these pathways using a moderate CLP model incorporating clinical treatments (Lactated Ringer Solution and antibiotics, ∼36% mortality). In this case, STING-KO mice show a similar phenotype to WT counterparts, while TRIF-KO mice show improved disease score and hypothermia. During sepsis, innate immune receptors recognize bacterial ligands and host-derived danger signals, including cell-free DNA released into the circulation. We show that IRF3 is activated in cultured macrophages treated with bacteria derived from the mouse cecum, dependent on TRIF, and in macrophages treated with mouse genomic DNA/Lipofectamine 2000, dependent on STING. Together, our data demonstrate that both the STING and TRIF pathways can promote sepsis pathogenesis; however, their contribution depends on the severity of the disease model. We show that bacteria are abundant in the peritoneum following both severe and moderate CLP, while cell-free DNA is more highly elevated in the serum following severe CLP compared with sham and moderate CLP. Hence, the presence of bacteria and cell-free DNA may explain the variable phenotypes in our severe CLP model (dependent on TRIF and STING) versus our moderate CLP model (dependent on TRIF only).

S100-alarmin-induced innate immune programming protects newborn infants from sepsis

The high risk of neonatal death from sepsis is thought to result from impaired responses by innate immune cells; however, the clinical observation of hyperinflammatory courses of neonatal sepsis contradicts this concept. Using transcriptomic, epigenetic and immunological approaches, we demonstrated that high amounts of the perinatal alarmins S100A8 and S100A9 specifically altered MyD88-dependent proinflammatory gene programs. S100 programming prevented hyperinflammatory responses without impairing pathogen defense. TRIF-adaptor-dependent regulatory genes remained unaffected by perinatal S100 programming and responded strongly to lipopolysaccharide, but were barely expressed. Steady-state expression of TRIF-dependent genes increased only gradually during the first year of life in human neonates, shifting immune regulation toward the adult phenotype. Disruption of this critical sequence of transient alarmin programming and subsequent reprogramming of regulatory pathways increased the risk of hyperinflammation and sepsis. Collectively these data suggest that neonates are characterized by a selective, transient microbial unresponsiveness that prevents harmful hyperinflammation in the delicate neonate while allowing for sufficient immunological protection.

Myeloid cell-specific inositol polyphosphate-4-phosphatase type I knockout mice impair bacteria clearance in a murine peritonitis model

Phosphatidylinositol 3-kinase (PI3K)/Akt signaling has been implicated in the anti-inflammatory response in a mouse model of endotoxemia and sepsis. The present study focused on the role of inositol polyphosphate-4-phosphatase type I (Inpp4a), which dephosphorylates PtdIns(3,4)P2 to PtdIns(3)P, in bacterial infections. We prepared myeloid cell-specific Inpp4a-conditional knockout mice. Macrophages from these mice showed increased Akt phosphorylation and reduced production of inflammatory cytokines in response to LPS or Escherichia coli in vitro. The Inpp4a knockout mice survived for a shorter time than wild type mice after i.p. infection with E. coli, with less production of inflammatory cytokines. Additionally, E. coli clearance from blood and lung was significantly impaired in the knockout mice. A likely mechanism is that the Inpp4a-catalyzed dephosphorylation of PtdIns(3,4)P2 down-regulates Akt pathways, which, in turn, increases the production of inflammatory mediators. This mechanism at least fits the decreased E. coli clearance and short survival in the Inpp4a knockout mice.

TRIF-dependent TLR signaling, its functions in host defense and inflammation, and its potential as a therapeutic target

Toll/IL-1R domain-containing adaptor-inducing IFN-β (TRIF)-dependent signaling is required for TLR-mediated production of type-I IFN and several other proinflammatory mediators. Various pathogens target the signaling molecules and transcriptional regulators acting in the TRIF pathway, thus demonstrating the importance of this pathway in host defense. Indeed, the TRIF pathway contributes to control of both viral and bacterial pathogens through promotion of inflammatory mediators and activation of antimicrobial responses. TRIF signaling also has both protective and pathologic roles in several chronic inflammatory disease conditions, as well as an essential function in wound-repair processes. Here, we review our current understanding of the regulatory mechanisms that control TRIF-dependent TLR signaling, the role of the TRIF pathway in different infectious and noninfectious pathologic states, and the potential for manipulating TRIF-dependent TLR signaling for therapeutic benefit.

An Immunological Perspective on Neonatal Sepsis

Despite concerted international efforts, mortality from neonatal infections remains unacceptably high in some areas of the world, particularly for premature infants. Recent developments in flow cytometry and next-generation sequencing technologies have led to major discoveries over the past few years, providing a more integrated understanding of the developing human immune system in the context of its microbial environment. We review these recent findings, focusing on how in human newborns incomplete maturation of the immune system before a full term of gestation impacts on their vulnerability to infection. We also discuss some of the clinical implications of this research in guiding the design of more-accurate age-adapted diagnostic and preventive strategies for neonatal sepsis.

Recent developments in severe sepsis research: from bench to bedside and back

Severe sepsis remains a worldwide threat, not only in industrialized countries, due to their aging population, but also in developing countries where there still are numerous cases of neonatal and puerperal sepsis. Tools for early diagnosis, a prerequisite for rapid and appropriate antibiotic therapy, are still required. In this review, we highlight some recent developments in our understanding of the associated systemic inflammatory response that help deciphering pathophysiology (e.g., epigenetic, miRNA, regulatory loops, compartmentalization, apoptosis and synergy) and discuss some of the consequences of sepsis (e.g., immune status, neurological and muscular alterations). We also emphasize the challenge to better define animal models and discuss past failures in clinical investigations in order to define new efficient therapies.

Neonatal Vaccination: Challenges and Intervention Strategies

BACKGROUND

While vaccines have been tremendously successful in reducing the incidence of serious infectious diseases, newborns remain particularly vulnerable in the first few months of their life to life-threatening infections. A number of challenges exist to neonatal vaccination. However, recent advances in the understanding of neonatal immunology offer insights to overcome many of those challenges.

OBJECTIVE

This review will present an overview of the features of neonatal immunity which make vaccination difficult, survey the mechanisms of action of available vaccine adjuvants with respect to the unique features of neonatal immunity, and propose a possible mechanism contributing to the inability of neonates to generate protective immune responses to vaccines.

METHODS

We surveyed recent published findings on the challenges to neonatal vaccination and possible intervention strategies including the use of novel vaccine adjuvants to develop efficacious neonatal vaccines.

RESULTS

Challenges in the vaccination of neonates include interference from maternal antibody and excessive skewing towards Th2 immunity, which can be counteracted by the use of proper adjuvants.

CONCLUSION

Synergistic stimulation of multiple Toll-like receptors by incorporating well-defined agonist-adjuvant combinations to vaccines is a promising strategy to ensure a protective vaccine response in neonates.

Improved emergency myelopoiesis and survival in neonatal sepsis by caspase-1/11 ablation

Over one million newborns die annually from sepsis with the highest mortality in premature and low-birthweight infants. The inflammasome plays a central role in the regulation of innate immunity and inflammation, and is presumed to be involved in protective immunity, in large part through the caspase-1-dependent activation of interleukin-1β (IL-1β) and IL-18. Studies in endotoxic shock, however, suggest that endogenous caspase-1 activity and the inflammasome contribute to mortality primarily by promoting excessive systemic inflammatory responses. We examined whether caspase-1 and the inflammasome also regulate neonatal inflammation, host protective immunity and myelopoiesis during polymicrobial sepsis. Neonatal (5-7 days) C57BL/6 and caspase-1/11(-/-) mice underwent a low-lethality caecal slurry model of intra-abdominal sepsis (LD25-45 ). Ablation of caspase-1/11, but not apoptosis-associated speck-like protein containing a CARD domain or nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3), improved neonatal survival following septic challenge compared with wild-type mice (P < 0·001), with decreased concentrations of inflammatory cytokines in the serum and peritoneum. Surprisingly, caspase-1/11(-/-) neonates also exhibited increased bone marrow and splenic haematopoietic stem cell expansion (P < 0·001), and increased concentrations of granulocyte and macrophage colony-stimulating factors in the peritoneum (P < 0·001) after sepsis. Ablation of caspase-1/11 signalling was also associated with increased recruitment of peritoneal macrophages and neutrophils (P < 0·001), increased phagocytosis by neutrophils (P = 0·003), and decreased bacterial colonization (P = 0·02) in the peritoneum. These findings suggest that endogenous caspase-1/11 activity, independent of the NLRP3 inflammasome, not only promotes the magnitude of the inflammatory response, but also suppresses protective immunity in the neonate, so contributing to innate immune dysfunction and poor survival in neonatal sepsis.

TRAM-Derived Decoy Peptides inhibits the inflammatory response in mouse mammary epithelial cells and a mastitis model in mice

It has been proved that TRAM-Derived Decoy peptides have anti-inflammatory properties. In this study, we synthesized a TRAM-Derived decoy peptide (TM6), belongs to TRAM TIR domain, of which sequence is "N"-RQIKIWFQNRRMKWK, KENFLRDTWCNFQFY-"C" and evaluated the effects of TM6 on lipopolysaccharide-induced mastitis in mice. In vivo, LPS-induced mice mastitis model was established by injection of LPS through the duct of mammary gland. TM6 was injected 1h before or after LPS treatment. In vitro, primary mouse mammary epithelial cells were used to investigate the effects of TM6 on LPS-induced inflammatory responses. The results showed that TM6 inhibited LPS-induced mammary gland histopathologic changes, MPO activity, and TNF-α, IL-1β and IL-6 production in mice. In vitro, TM6 significantly inhibited LPS-induced TNF-α and IL-6 production, as well as NF-κB and MAPKs activation. In conclusion, this study demonstrated that TM6 had protective effects on LPS-mastitis and may be a promising therapeutic reagent for mastitis treatment.