Developmental biology of the innate immune response: implications for neonatal and infant vaccine development

Production of inflammatory cytokines in response to diphtheria-pertussis-tetanus (DPT), haemophilus influenzae type b (Hib), and 7-valent pneumococcal (PCV7) vaccines

Haemophilus influenzae type b (Hib) and 7-valent pneumococcal (PCV7) vaccines both became recommended in Japan in 2010. In this study, cytokine production was investigated in peripheral blood mononuclear cells (PBMCs) cultures stimulated with diphtheria and tetanus toxoids combined with acellular pertussis vaccine (DPT), Hib, and PCV7 separately or concurrent different combinations, all as final off-the-shelf vaccines without the individual vaccine components as controls. Higher IL-1β levels were produced when cultures were stimulated with PCV than with DPT or Hib, and the concurrent stimulation including PCV7 enhanced the production of IL-1β. Although Hib induced higher levels of IL-6, no significant difference was observed in IL-6 production with the concurrent stimulation. The concurrent stimulation with Hib/PCV7 and DPT/Hib/PCV7 produced higher levels of TNF-α and human G-CSF. Cytokine profiles were examined in serum samples obtained from 61 vaccine recipients with febrile reactions and 18 recipients without febrile illness within 24 h of vaccination. No significant difference was observed in cytokine levels of IL-1β, IL-4, IL-6, IL-10, IL-12, IFN-γ, MIP-1, TNF-α, and prostaglandin E2 (PGE2) in sera between the two groups. However, significantly higher levels of human G-CSF were observed in recipients with febrile illness than in those without febrile reactions. Further investigations of the significance of elevated serum G-CSF levels are required in vaccine recipients with febrile illness.

Pediatric sepsis: important considerations for diagnosing and managing severe infections in infants, children, and adolescents

Sepsis is the leading cause of death in children worldwide. Although the diagnosis and management of sepsis in infants and children is largely influenced by studies done in adults, there are important considerations relevant for pediatrics. This article highlights pediatric-specific issues related to the definition of sepsis and its epidemiology and management. We review how the capacity of the immune system to respond to infection develops over early life. We also bring attention to primary immune deficiencies that should be considered in children recurrently infected with specific types of organisms. The management of pediatric sepsis must be tailored to the child’s age and immune capacity, and to the site, severity, and source of the infection. It is important for clinicians to be aware of infection-related syndromes that primarily affect children. Although children in developed countries are more likely to survive severe infections than adults, many survivors have chronic health impairments.

Toll-like receptor induced pro-interleukin-1β and interleukin-6 in monocytes are lower in healthy infants compared to adults

Infants have long been known to have higher infectious diseases morbidity and mortality and suboptimal vaccination responses compared to older children and adults. A variety of differences in innate and adaptive immune responses have been described between these two groups. We compared Toll-like receptor (TLR)-induced production of pro-interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α between 2-month-old infants and adults. TLR 7/8-induced production of pro-IL-1β and IL-6 in monocytes was lower in 2-month-old infants compared to adults. There was no difference in TLR 7/8-induced production of TNF-α. Lower TLR-induced production of pro-IL-1β and IL-6 in innate immune cells during early infancy likely contributes to suboptimal vaccine responses and infectious diseases susceptibility.

Toll-like receptors in neonatal sepsis

Toll-like receptors are vital transmembrane receptors that initiate the innate immune response to many micro-organisms. The discovery of these receptors has improved our understanding of host-pathogen interactions, and these receptors play an important role in the pathogenesis of multiple neonatal conditions such as sepsis and brain injury. Toll-like receptors, especially TLRs 2 and 4, are associated with necrotizing enterocolitis, periventricular leukomalacia and sepsis.

CONCLUSION

Toll-like receptor modulation may potentially be used as immunomodulators in the management of neonatal sepsis.

The path to an RSV vaccine

Respiratory syncytial virus (RSV) is the greatest remaining unmet infant vaccine need in developed countries and an important unmet infant vaccine need worldwide. More than 40 years of effort have yet to result in a licensed RSV vaccine for humans. Key challenges to RSV vaccine development include a peak of severe disease at 2-3 months of age, problematic biochemical behavior of key vaccine antigens, a history of vaccine-mediated disease enhancement, and reliance on animal models that may not accurately reflect human disease processes. Potential paths to overcome these challenges include maternal immunization, structure-based engineering of vaccine antigens, the design of a novel platform for safe infant immunization, and the development of improved animal models for vaccine-enhanced disease.

CD4+ T-cell responses among adults and young children in response to Streptococcus pneumoniae and Haemophilus influenzae vaccine candidate protein antigens

We characterized cytokine profiles of CD4(+) T-helper (h) cells in adults and young children to ascertain if responses occur to next-generation candidate vaccine antigens PspA, PcpA, PhtD, PhtE, Ply, LytB of Streptococcus pneumonia (Spn) and protein D and OMP26 of non-typeable Haemophilus influenzae (NTHi). Adults had vaccine antigen-specific Th1 and Th2 cells responsive to all antigens evaluated whereas young children had significant numbers of vaccine antigen-specific CD4(+) T cells producing IL-2, (p=0.004). Vaccine antigen-specific CD4(+) T-cell populations in adults were largely of effector (TEM) and/or central memory (TCM) phenotypes as defined by CD45RA(-)CCR7(+) or CD45RA(-)CCR7(-) respectively; however among young children antigen-specific IL-2 producing CD4(+) T cells demonstrated CD45RA(+) expression (non-memory cells). We conclude that adults have circulating memory CD4(+) T cells (CD45RA(-)) that can be stimulated by all the tested Spn and NTHi protein vaccine candidate antigens, whereas young children have a more limited response.

The ultra-potent and selective TLR8 agonist VTX-294 activates human newborn and adult leukocytes

Background

Newborns display distinct immune responses that contribute to susceptibility to infection and reduced vaccine responses. Toll-like receptor (TLR) agonists may serve as vaccine adjuvants, when given individually or in combination, but responses of neonatal leukocytes to many TLR agonists are diminished. TLR8 agonists are more effective than other TLR agonists in activating human neonatal leukocytes in vitro, but little is known about whether different TLR8 agonists may distinctly activate neonatal leukocytes. We characterized the in vitro immuno-stimulatory activities of a novel benzazepine TLR8 agonist, VTX-294, in comparison to imidazoquinolines that activate TLR8 (R-848; (TLR7/8) CL075; (TLR8/7)), with respect to activation of human newborn and adult leukocytes. Effects of VTX-294 and R-848 in combination with monophosphoryl lipid A (MPLA; TLR4) were also assessed.

Methods

TLR agonist specificity was assessed using TLR-transfected HEK293 cells expressing a NF-κB reporter gene. TLR agonist-induced cytokine production was measured in human newborn cord and adult peripheral blood using ELISA and multiplex assays. Newborn and adult monocytes were differentiated into monocyte-derived dendritic cells (MoDCs) and TLR agonist-induced activation assessed by cytokine production (ELISA) and co-stimulatory molecule expression (flow cytometry).

Results

VTX-294 was ∼100x more active on TLR8- than TLR7-transfected HEK cells (EC₅₀, ∼50 nM vs. ∼5700 nM). VTX-294-induced TNF and IL-1β production were comparable in newborn cord and adult peripheral blood, while VTX-294 was ∼ 1 log more potent in inducing TNF and IL-1β production than MPLA, R848 or CL075. Combination of VTX-294 and MPLA induced greater blood TNF and IL-1β responses than combination of R-848 and MPLA. VTX-294 also potently induced expression of cytokines and co-stimulatory molecules HLA-DR and CD86 in human newborn MoDCs.

Conclusions

VTX-294 is a novel ultra-potent TLR8 agonist that activates newborn and adult leukocytes and is a candidate vaccine adjuvant in both early life and adulthood.

Pediatric influenza vaccination: understanding the T-cell response

Influenza A virus-specific T cells are highly cross-reactive and contribute to heterosubtypic immunity, which may afford protection against novel pandemic strains of influenza virus. However, the magnitude and nature of virus-specific T-cell responses induced by natural infections and/or vaccination in young children is poorly understood. Host factors, such as the development of the immune system during childhood and environmental factors such as exposure rates to influenza viruses and interference by vaccination contribute to shaping the magnitude and specificity of the T-cell response. Here, the authors review several of these factors, including the differences between T-cell responses of young children and adults, the age-dependent frequency of virus-specific T cells and the impact of annual childhood influenza vaccination. In addition, the authors summarize all currently available studies in which influenza vaccine-induced T-cell responses were evaluated. The authors discuss these findings in the light of developing vaccines and vaccination strategies aiming at the induction of protective immunity to seasonal and pandemic influenza viruses of antigenically distinct subtypes.

Necrotizing enterocolitis and cytomegalovirus infection in a premature infant

Necrotizing enterocolitis is the most common gastrointestinal emergency in neonates. The etiology is considered multifactorial. Risk factors include prematurity, enteral feeding, hypoxia, and bacterial colonization. The etiologic role of viruses is unclear. We present a case of necrotizing enterocolitis associated with cytomegalovirus and Proteobacteria in a 48-day-old, ex-premature infant and discuss the effects of potential viral-bacterial interactions on host susceptibility to this disease.

Immune response to vaccine adjuvants during the first year of life

Subunit vaccine formulations often include adjuvants that primarily stimulate innate immune cells. While young infants represent the major target population for vaccination, effective immunization in this age group remains a challenge. Many parameters of innate immune responses differ quantitatively and qualitatively from newborns to infants and adults, revealing a highly regulated developmental program. Herein, we discuss the potential implications of innate immune ontogeny for the activity of adjuvants contained in licensed infant vaccines, as well as future directions for rational design of adjuvanted vaccines for this age group.

Age-related changes in expression and function of Toll-like receptors in human skin

Toll-like receptors (TLRs) initiate innate immune responses and direct subsequent adaptive immunity. They play a major role in cutaneous host defense against micro-organisms and in the pathophysiology of several inflammatory skin diseases. To understand the role of TLRs in the acquisition of immunological competence, we conducted a comprehensive study to evaluate TLR expression and function in the developing human skin before and after birth and compared it with adults. We found that prenatal skin already expresses the same spectrum of TLRs as adult skin. Strikingly, many TLRs were significantly higher expressed in prenatal (TLRs 1-5) and infant and child (TLRs 1 and 3) skin than in adult skin. Surprisingly, neither dendritic cell precursors in prenatal skin nor epidermal Langerhans cells and dermal dendritic cells in adult skin expressed TLRs 3 and 6, whereas the staining pattern and intensity of both TLRs in fetal basal keratinocytes was almost comparable to those of adults. Stimulation of primary human keratinocytes from fetal, neonatal and adult donors with selected TLR agonists revealed that the synthetic TLR3 ligand poly (I:C) specifically, mimicking viral double-stranded RNA, induced a significantly enhanced secretion of CXCL8/IL8, CXCL10/IP-10 and TNFα in fetal and neonatal keratinocytes compared with adult keratinocytes. This study demonstrates quantitative age-specific modifications in TLR expression and innate skin immune reactivity in response to TLR activation. Thus, antiviral innate immunity already in prenatal skin may contribute to protect the developing human body from viral infections in utero in a scenario where the adaptive immune system is not yet fully functional.

The effect of age on whole blood interferon-gamma release assay response among children investigated for latent tuberculosis infection

OBJECTIVE

To evaluate the effect of age upon QuantiFERON-TB Gold-In-Tube (QFT-IT) assay outcome among children examined for latent tuberculosis infection (LTBI).

STUDY DESIGN

A cross-sectional study was conducted among 761 children (mean age ± SD: 7.84 ± 4.68 years) evaluated for LTBI. Participants were examined with both tuberculin skin test and QFT-IT (Cellestis, Australia) and categorized into 4 age groups. Multivariate logistic and linear regressions were used to evaluate the association between selected demographic and patient characteristics upon the qualitative and quantitative QFT-IT outcomes. Agreement between the tuberculin skin test and QFT-IT within groups was evaluated with the κ statistic.

RESULTS

QFT-IT indeterminate results occurred more frequently among young children (8.1%; P < .0001) and children (2.7%; P = .025) than adolescents (0.7%). Among QFT-IT positive patients, infants had higher mean (± SD) interferon-gamma (IFNγ) concentration than adolescents. QFT-IT positive (vs negative) outcome was associated with origin from a high tuberculosis endemicity setting (AOR = 4.54; 95% CI, 3.22-6.25) and lack of previous Bacille Calmette Guerin immunization (AOR = 2.70; 95% CI, 1.89-3.85), but not patient age (AOR = 0.96; 95% CI, 0.92-0.99). However, among QFT-IT positive patients, the IFNγ concentration was inversely associated with patient age (P = .009) and positively with mitogen response (P = .0002). Agreement between tests was not significantly different between younger and older children in the different risk groups.

CONCLUSIONS

Qualitative QFT-IT assay results are not affected by patient age. However, indeterminate results occur more frequently among younger children. Among patients with LTBI the quantitative QFT-IT result (ie, IFNγ) is inversely associated with patient age.

Ontogeny of Toll-like receptor mediated cytokine responses of South African infants throughout the first year of life

The first year of life represents a time of marked susceptibility to infections; this is particularly true for regions in sub-Saharan Africa. As innate immunity directs the adaptive immune response, the observed increased risk for infection as well as a suboptimal response to vaccination in early life may be due to less effective innate immune function. In this study, we followed a longitudinal cohort of infants born and raised in South Africa over the first year of life, employing the most comprehensive analysis of innate immune response to stimulation published to date. Our findings reveal rapid changes in innate immune development over the first year of life. This is the first report depicting dramatic differences in innate immune ontogeny between different populations in the world, with important implications for global vaccination strategies.

Nutrition, epigenetics, and metabolic syndrome

SIGNIFICANCE

Epidemiological and animal studies have demonstrated a close link between maternal nutrition and chronic metabolic disease in children and adults. Compelling experimental results also indicate that adverse effects of intrauterine growth restriction on offspring can be carried forward to subsequent generations through covalent modifications of DNA and core histones.

RECENT ADVANCES

DNA methylation is catalyzed by S-adenosylmethionine-dependent DNA methyltransferases. Methylation, demethylation, acetylation, and deacetylation of histone proteins are performed by histone methyltransferase, histone demethylase, histone acetyltransferase, and histone deacetyltransferase, respectively. Histone activities are also influenced by phosphorylation, ubiquitination, ADP-ribosylation, sumoylation, and glycosylation. Metabolism of amino acids (glycine, histidine, methionine, and serine) and vitamins (B6, B12, and folate) plays a key role in provision of methyl donors for DNA and protein methylation.

CRITICAL ISSUES

Disruption of epigenetic mechanisms can result in oxidative stress, obesity, insulin resistance, diabetes, and vascular dysfunction in animals and humans. Despite a recognized role for epigenetics in fetal programming of metabolic syndrome, research on therapies is still in its infancy. Possible interventions include: 1) inhibition of DNA methylation, histone deacetylation, and microRNA expression; 2) targeting epigenetically disturbed metabolic pathways; and 3) dietary supplementation with functional amino acids, vitamins, and phytochemicals.

FUTURE DIRECTIONS

Much work is needed with animal models to understand the basic mechanisms responsible for the roles of specific nutrients in fetal and neonatal programming. Such new knowledge is crucial to design effective therapeutic strategies for preventing and treating metabolic abnormalities in offspring born to mothers with a previous experience of malnutrition.

Age-dependent changes in innate immune phenotype and function in rhesus macaques (Macaca mulatta)

Aged individuals are more susceptible to infections due to a general decline in immune function broadly referred to as immune senescence. While age-related changes in the adaptive immune system are well documented, aging of the innate immune system remains less well understood, particularly in nonhuman primates. A more robust understanding of age-related changes in innate immune function would provide mechanistic insight into the increased susceptibility of the elderly to infection. Rhesus macaques have proved a critical translational model for aging research, and present a unique opportunity to dissect age-dependent modulation of the innate immune system. We examined age-related changes in: (i) innate immune cell frequencies; (ii) expression of pattern recognition receptors (PRRs) and innate signaling molecules; (iii) cytokine responses of monocytes and dendritic cells (DC) following stimulation with PRR agonists; and (iv) plasma cytokine levels in this model. We found marked changes in both the phenotype and function of innate immune cells. This included an age-associated increased frequency of myeloid DC (mDC). Moreover, we found toll-like receptor (TLR) agonists lipopolysaccharide (TLR4), fibroblast stimulating ligand-1 (TLR2/6), and ODN2006 (TLR7/9) induced reduced cytokine responses in aged mDC. Interestingly, with the exception of the monocyte-derived TNFα response to LPS, which increased with age, TNFα, IL-6, and IFNα responses declined with age. We also found that TLR4, TLR5, and innate negative regulator, sterile alpha and TIR motif containing protein (SARM), were all expressed at lower levels in young animals. By contrast, absent in melanoma 2 and retinoic acid-inducible gene I expression was lowest in aged animals. Together, these observations indicate that several parameters of innate immunity are significantly modulated by age and contribute to differential immune function in aged macaques.

Ontogeny of Toll-like and NOD-like receptor-mediated innate immune responses in Papua New Guinean infants

Studies addressing the ontogeny of the innate immune system in early life have reported mainly on Toll-like receptor (TLR) responses in infants living in high-income countries, with little or even no information on other pattern recognition receptors or on early life innate immune responses in children living under very different environmental conditions in less-developed parts of the world. In this study, we describe whole blood innate immune responses to both Toll-like and nucleotide-binding oligomerization domain (NOD)-like receptor agonists including the widely used vaccine adjuvant ‘alum’ in a group of Papua New Guinean infants aged 1–3 (n = 18), 4–6 (n = 18), 7–12 (n = 21) and 13–18 (n = 10) months old. Depending on the ligands and cytokines studied, different age-related patterns were found: alum-induced IL-1β and CXCL8 responses were found to significantly decline with increasing age; inflammatory (IL-6, IL-1β, IFN-γ) responses to TLR2 and TLR3 agonists increased; and IL-10 responses remained constant or increased during infancy, while TNF-α responses either declined or remained the same. We report for the first time that whole blood innate immune responses to the vaccine adjuvant alum decrease with age in infancy; a finding that may imply that the adjuvant effect of alum in pediatric vaccines could be age-related. Our findings further suggest that patterns of innate immune development may vary between geographically diverse populations, which in line with the ‘hygiene hypothesis’ particularly involves persistence of innate IL-10 responses in populations experiencing higher infectious pressure.

Imidazoquinoline Toll-like receptor 8 agonists activate human newborn monocytes and dendritic cells through adenosine-refractory and caspase-1-dependent pathways

BACKGROUND

Newborns have frequent infections and manifest impaired vaccine responses, motivating a search for neonatal vaccine adjuvants. Alum is a neonatal adjuvant but might confer a T(H)2 bias. Toll-like receptor (TLR) agonists are candidate adjuvants, but human neonatal cord blood monocytes demonstrate impaired T(H)1-polarizing responses to many TLR agonists caused by plasma adenosine acting through cyclic AMP. TLR8 agonists, including imidazoquinolines (IMQs), such as the small synthetic 3M-002, induce adult-level TNF from neonatal monocytes, but the scope and mechanisms of IMQ-induced activation of neonatal monocytes and monocyte-derived dendritic cells (MoDCs) have not been reported.

OBJECTIVE

We sought to characterize IMQ-induced activation of neonatal monocytes and MoDCs.

METHODS

Neonatal cord and adult peripheral blood monocytes and MoDCs were cultured in autologous plasma; levels of alum- and TLR agonist-induced cytokines and costimulatory molecules were measured. TLR8 and inflammasome function were assayed by using small interfering RNA and Western blotting/caspase-1 inhibitory peptide, respectively. The ontogeny of TLR8 agonist-induced cytokine responses was defined in rhesus macaque whole blood ex vivo.

RESULTS

IMQs were more potent and effective than alum at inducing TNF and IL-1β from monocytes. 3M-002 induced robust TLR pathway transcriptome activation and T(H)1-polarizing cytokine production in neonatal and adult monocytes and MoDCs, signaling through TLR8 in an adenosine/cyclic AMP-refractory manner. Newborn MoDCs displayed impaired LPS/ATP-induced caspase-1-mediated IL-1β production but robust 3M-002-induced caspase-1-mediated inflammasome activation independent of exogenous ATP. TLR8 IMQs induced robust TNF and IL-1β in whole blood of rhesus macaques at birth and infancy.

CONCLUSIONS

IMQ TLR8 agonists engage adenosine-refractory TLR8 and inflammasome pathways to induce robust monocyte and MoDC activation and represent promising neonatal adjuvants.

Alum-adjuvanted H5N1 whole virion inactivated vaccine (WIV) enhanced inflammatory cytokine productions

Alum-adjuvanted H5 whole virion inactivated vaccine (WIV) was licensed for adults in Japan but induced marked febrile reactions with significantly stronger antibody responses in children. In this study, the mechanisms behind the different responses were investigated. Lymphocytes were obtained from 25 healthy subjects who were not immunized with H5 vaccine, to examine the innate immune impact of the various vaccine formulations, analyzing the cytokine production profile stimulated with alum adjuvant alone, alum-adjuvanted H5 WIIV, plain H5 WIV, and H5 split vaccine. Alum adjuvant did not induce cytokine production, but H5 split induced IFN-γ and TNF-α. H5 WIV induced IL-6, IL-17, TNF-α, MCP-1, IFN-γ, and IFN-α. An extremely low level of IL-1β was produced in response to H5 WIV, and alum-adjuvanted H5 WIV enhanced IL-1β production, with similar levels of other cytokines stimulated with H5 WIV. Enhanced production of cytokines induced by alum-adjuvanted H5 WIV may be related to the higher incidence of febrile reactions with stronger immune responses in children but it should be further investigated why efficient immune responses with febrile illness were observed only in young children.

Acute bacterial meningitis in infants and children: epidemiology and management

Acute bacterial meningitis (ABM) continues to be associated with high mortality and morbidity, despite advances in antimicrobial therapy. The causative organism varies with age, immune function, immunization status, and geographic region, and empiric therapy for meningitis is based on these factors. Haemophilus influenzae type b (Hib), Streptococcus pneumoniae, and Neisseria meningitidis cause the majority of cases of ABM. Disease epidemiology is changing rapidly due to immunization practices and changing bacterial resistance patterns. Hib was the leading cause of meningitis in children prior to the introduction of an effective vaccination. In those countries where Hib vaccine is a part of the routine infant immunization schedule, Hib has now been virtually eradicated as a cause of childhood meningitis. Vaccines have also been introduced for pneumococcal and meningococcal diseases, which have significantly changed the disease profile. Where routine pneumococcal immunization has been introduced there has been a reported increase in invasive pneumococcal disease due to non-vaccine serotypes. In those parts of the world that have introduced conjugate meningococcal vaccines, there has been a significant change in the epidemiology of meningococcal meningitis. As a part of the United Nations Millennium Development Goal 4, the WHO has introduced a new vaccine policy to improve vaccine availability in resource poor countries. In addition, antibiotic resistance is an increasing problem, especially with pneumococcal infection. Effective treatment focuses on early recognition and use of effective antibiotics. This review will attempt to focus on the changing epidemiology of ABM in pediatric patients due to vaccination, the changing patterns of infecting bacterial serotypes due to vaccination, and on antibiotic resistance and its impact on current management strategies.

Development of newborn and infant vaccines

Vaccines for early-life immunization are a crucial biomedical intervention to reduce global morbidity and mortality, yet their developmental path has been largely ad hoc, empiric, and inconsistent. Immune responses of human newborns and infants are distinct and cannot be predicted from those of human adults or animal models. Therefore, understanding and modeling age-specific human immune responses will be vital to the rational design and development of safe and effective vaccines for newborns and infants.

Challenges for development of meningococcal vaccines in infants and children

Neisseria meningitidis causes significant disease in the form of severe sepsis syndrome or meningococcal meningitis. Owing to the susceptibility of the immune system in early life, the risk of disease after infection is significantly higher in infants. Thus far, vaccines targeted against meningococcal serogroups have struggled to provide lasting protection in young children. Even conjugate vaccines that are now routinely used in the immunization of infants require multiple dosing and the duration of protection has been shown to wane over time and require repeated booster doses. After briefly summarizing the current epidemiology according to age and serogroup, this article will consider the reasons for poor immunogenicity of vaccines in infants and will discuss the relative efficacy of the different vaccine types in this age group. It will then go on to consider strategies for optimizing the protection of infants against meningococcal disease.

Age-dependent maturation of Toll-like receptor-mediated cytokine responses in Gambian infants

The global burden of neonatal and infant mortality due to infection is staggering, particularly in resource-poor settings. Early childhood vaccination is one of the major interventions that can reduce this burden, but there are specific limitations to inducing effective immunity in early life, including impaired neonatal leukocyte production of Th1-polarizing cytokines to many stimuli. Characterizing the ontogeny of Toll-like receptor (TLR)-mediated innate immune responses in infants may shed light on susceptibility to infection in this vulnerable age group, and provide insights into TLR agonists as candidate adjuvants for improved neonatal vaccines. As little is known about the leukocyte responses of infants in resource-poor settings, we characterized production of Th1-, Th2-, and anti-inflammatory-cytokines in response to agonists of TLRs 1-9 in whole blood from 120 Gambian infants ranging from newborns (cord blood) to 12 months of age. Most of the TLR agonists induced TNFα, IL-1β, IL-6, and IL-10 in cord blood. The greatest TNFα responses were observed for TLR4, -5, and -8 agonists, the highest being the thiazoloquinoline CLO75 (TLR7/8) that also uniquely induced cord blood IFNγ production. For most agonists, TLR-mediated TNFα and IFNγ responses increased from birth to 1 month of age. TLR8 agonists also induced the greatest production of the Th1-polarizing cytokines TNFα and IFNγ throughout the first year of life, although the relative responses to the single TLR8 agonist and the combined TLR7/8 agonist changed with age. In contrast, IL-1β, IL-6, and IL-10 responses to most agonists were robust at birth and remained stable through 12 months of age. These observations provide fresh insights into the ontogeny of innate immunity in African children, and may inform development of age-specific adjuvanted vaccine formulations important for global health.

Early life environment and developmental immunotoxicity in inflammatory dysfunction and disease

Components of the innate immune system such as macrophages and dendritic cells are instrumental in determining the fate of immune responses and are, also, among the most sensitive targets of early life environmental alterations including developmental immunotoxicity (DIT). DIT can impede innate immune cell maturation, disrupt tissue microenvironment, alter immune responses to infectious challenges, and disrupt regulatory responses. Dysregulation of inflammation, such as that observed with DIT, has been linked with an increased risk of chronic inflammatory diseases in both children and adults. In this review, we discuss the relationship between early-life risk factors for innate immune modulation and promotion of dysregulated inflammation associated with chronic inflammatory disease. The health risks from DIT-associated inflammation may extend beyond primary immune dysfunction to include an elevated risk of several later-life, inflammatory-mediated diseases that target a wide range of physiological systems and organs. For this reason, determination of innate immune status should be an integral part of drug and chemical safety evaluation.

Ontogeny of Toll-like receptor mediated cytokine responses of human blood mononuclear cells

Newborns and young infants suffer increased infectious morbidity and mortality as compared to older children and adults. Morbidity and mortality due to infection are highest during the first weeks of life, decreasing over several years. Furthermore, most vaccines are not administered around birth, but over the first few years of life. A more complete understanding of the ontogeny of the immune system over the first years of life is thus urgently needed. Here, we applied the most comprehensive analysis focused on the innate immune response following TLR stimulation over the first 2 years of life in the largest such longitudinal cohort studied to-date (35 subjects). We found that innate TLR responses (i) known to support Th17 adaptive immune responses (IL-23, IL-6) peaked around birth and declined over the following 2 years only to increase again by adulthood; (ii) potentially supporting antiviral defense (IFN-α) reached adult level function by 1 year of age; (iii) known to support Th1 type immunity (IL-12p70, IFN-γ) slowly rose from a low at birth but remained far below adult responses even at 2 years of age; (iv) inducing IL-10 production steadily declined from a high around birth to adult levels by 1 or 2 years of age, and; (v) leading to production of TNF-α or IL-1β varied by stimuli. Our data contradict the notion of a linear progression from an ‘immature’ neonatal to a ‘mature’ adult pattern, but instead indicate the existence of qualitative and quantitative age-specific changes in innate immune reactivity in response to TLR stimulation.

Profound lack of interleukin (IL)-12/IL-23p40 in neonates born early in gestation is associated with an increased risk of sepsis

BACKGROUND

Infants born prematurely are highly vulnerable to infections and also exhibit a high susceptibility to organ damage due to inflammation.

METHODS

To investigate homeostatic immune control early in life, we used advanced multiparameter flow cytometry to compare responses to multiple Toll-like receptor (TLR) ligands in single cells and mononuclear cell populations in term neonates versus preterm neonates born before 29 weeks of gestation.

RESULTS

Preterm neonates had globally attenuated TLR-stimulated interleukin (IL)-6, interferon-α, and, to a lesser extent, tumor necrosis factor-α responses but demonstrated relative preservation of anti-inflammatory IL-10 responses in monocytes and dendritic cell subtypes. Remarkably, preterm neonates were also profoundly deficient in the common IL-12 and IL-23 cytokines' p40 subunit, which is critical for immunity against a wide variety of microbial pathogens in mice. Consistent with the increased susceptibility to infections resulting from the lack of IL-12/IL-23 in human newborns, significantly lower serum p40 concentrations were observed at birth in infants who developed early-onset sepsis.

CONCLUSION

To our knowledge, this study is the first detailed analysis of multiple TLR function in neonates born extremely premature. Although attenuation of proinflammatory pathways may protect against tissue-damaging immunity early in life, this previously unrecognized p40 immune deficiency appears to result in considerably increased susceptibility to infection in human preterm newborns.

Neonatal CD8+ T-cell differentiation is dependent on interleukin-12

Neonatal CD8(+) T-cell activation is significantly impaired compared with that in adults. Recent studies have demonstrated that interleukin (IL)-12 is necessary as a third signal, in addition to antigen and co-stimulation, to authorize the differentiation of naive CD8(+) T cells. We examined whether human neonatal CD8(+) T cells, which possess an exclusively naive T-cell phenotype, required a third signal to authorize a productive T-cell response. IL-12 enhanced activated naive CD8(+) T-cell survival, expansion, CD25 expression, and IL-2 production. Activated CD8(+) T cells produced interferon-γ and intracellular granzyme B and were cytotoxic only in the presence of IL-12. Sustained IL-12 signaling for 72 hours was required for optimal interferon-γ production. IL-12, in concert with T cell receptor (TCR) stimulation, sustained late-stage (48-72 hours) intracellular phosphorylation and particularly total protein levels of the proximal TCR components, Lck, and CD3ξ. The requirement for a third signal for productive human neonatal CD8(+) T-cell differentiation may have implications for neonatal vaccination strategies.

The challenge of assessing infant vaccine responses in resource-poor settings

Newborns and infants are highly susceptible to infectious diseases, resulting in high mortality and morbidity, particularly in resource-poor settings. Many vaccines require several booster doses, resulting in an extensive vaccine schedule, and yet there is still inadequate protection from some of these diseases. This is partly due to the immaturity of the neonate and infant immune system. Little is known about the specific modifications to immunological assessment protocols in early life but increasing knowledge of infant immunology has helped provide better recommendations for assessing these responses. Since most new vaccines will eventually be deployed in low-income settings such as Africa, the logistics and resources of assessing immunity in such settings also need to be understood. In this article, we will review immunity to vaccines in early life, discuss the many challenges associated with assessing immunogenicity and provide practical tips.

Inflammatory and autoimmune reactions in atherosclerosis and vaccine design informatics

Atherosclerosis is the leading pathological contributor to cardiovascular morbidity and mortality worldwide. As its complex pathogenesis has been gradually unwoven, the regime of treatments and therapies has increased with still much ground to cover. Active research in the past decade has attempted to develop antiatherosclerosis vaccines with some positive results. Nevertheless, it remains to develop a vaccine against atherosclerosis with high affinity, specificity, efficiency, and minimal undesirable pathology. In this review, we explore vaccine development against atherosclerosis by interpolating a number of novel findings in the fields of vascular biology, immunology, and bioinformatics. With recent technological breakthroughs, vaccine development affords precision in specifying the nature of the desired immune response—useful when addressing a disease as complex as atherosclerosis with a manifold of inflammatory and autoimmune components. Moreover, our exploration of available bioinformatic tools for epitope-based vaccine design provides a method to avoid expenditure of excess time or resources.