Unbalanced Neonatal CD4(+) T-Cell Immunity

In vivo immunoprotective comparison between recombinant protein and DNA vaccine of Eimeria tenella surface antigen 4

Eimeria tenella, belonging to protozoon, is the causative agent of cecal coccidiosis in chicken and causes enormous impacts for poultry industry. The surface antigens of apicomplexan parasites function as attachment and invasion in host-parasite interaction. Meanwhile, host immune response is triggered as a result of parasitic invasion. Immunogenicity and potency as a vaccinal candidate antigen of E. tenella surface antigen 4 (EtSAG4) have been unknown. Therefore, a gene segment of E. tenella EtSAG4 was amplified and transplanted to pET28a prokaryotic vector for recombinant protein expression. Similarly, pEGFP-N1 eukaryotic vectors with EtSAG4 gene segment (pEGFP-N1-EtSAG4) amplified in 293 T cells as DNA vaccines. Reverse transcription-polymerase chain reaction (RT-PCR) assay and western blot analysis were used to demonstrate successful expressions of EtSAG4 in Escherichia coli or 293 T cells. Subsequently, animal experiments (72 cobb broilers) were performed to evaluate immunoprotective between recombinant protein and DNA vaccine of E. tenella EtSAG4 using different immunizing doses (50 or 100 μg), respectively. Serum from chickens infected with E. tenella identified recombinant EtSAG4 (rEtSAG4) protein. Chickens vaccinated with either rEtSAG4 protein or pEGFP-N1-EtSAG4 plasmids both shown a significant increase in concentration of IFN-γ (p < 0.05) compared with control groups indicating production of cell-mediated immunity. Besides, pEGFP-N1-EtSAG4 plasmids motivated more intense immune responses for immunoglobulin Y (IgY) and interleukin 17 (IL-17) (p < 0.05) contrast to control groups. However, there was no increase in concentration of interleukin 10 (IL-10) and interleukin 4 (IL-4) for both rEtSAG4 protein and pEGFP-N1-EtSAG4 plasmids. Chickens vaccinated with rEtSAG4 protein or pEGFP-N1-EtSAG4 plasmids both show higher weight, lower oocyst output and mean lesion scores compared with infection control groups. The highest anticoccidial index (ACI) value of immunized groups was 168.24 from EGFP-N1-EtSAG4 plasmids (100 μg) group. Generally, EGFP-N1-EtSAG4 plasmids as DNA vaccines provided a more effective immunoprotective for chickens against E. tenalla than that of rEtSAG4 protein as subunit vaccines. EtSAG4 is a promising candidate antigen gene for development of coccidiosis vaccine.

Clinical and Immunological Metrics During Pediatric Rhesus Macaque Development

Background: Clinical measurements commonly used to evaluate overall health of laboratory animals including complete blood count, serum chemistry, weight, and immunophenotyping, differ with respect to age, development, and environment. This report provides comprehensive clinical and immunological reference ranges for pediatric rhesus macaques over the first year of life. Methods: We collected and analyzed blood samples from 151 healthy rhesus macaques, aged 0-55 weeks, and compared mother-reared infants to two categories of nursery-reared infants; those on an active research protocol and those under derivation for the expanded specific-pathogen-free breeding colony. Hematology was performed on EDTA-anticoagulated blood using a Sysmex XT2000i, and serum clinical chemistry was performed using the Beckman AU480 chemistry analyzer. Immunophenotyping of whole blood was performed with immunofluorescence staining and subsequent flow cytometric analysis on a BD LSRFortessa. Plasma cytokine analysis was performed using a Millipore multiplex Luminex assay. Results: For hematological and chemistry measurements, pediatric reference ranges deviate largely from adults. Comparison of mother-reared and nursery-reared animals revealed that large differences depend on rearing conditions and diet. Significant differences found between two nursery-reared cohorts (research and colony animals) indicate large influences of experimental factors and anesthetic events on these parameters. Immune cells and cytokine responses presented with distinct patterns for infants depending on age, birth location, and rearing conditions. Conclusions: Our results illustrate how the immune system changed over time and that there was variability among pediatric age groups. Reference ranges of results reported here will support interpretations for how infection and treatment may skew common immune correlates used for assessment of pathology or protection in research studies as well as help veterinarians in the clinical care of infant non-human primates. We highlighted the importance of using age-specific reference comparisons for pediatric studies and reiterated the utility of rhesus macaques as a model for human studies. Given the rapid transformation that occurs in multiple tissue compartments after birth and cumulative exposures to antigens as individuals grow, a better understanding of immunological development and how this relates to timing of infection or vaccination will support optimal experimental designs for developing vaccines and treatment interventions.

Whole-Cell Pertussis Vaccination and Decreased Risk of IgE-Mediated Food Allergy: A Nested Case-Control Study

BACKGROUND

Rates of food allergy have increased markedly in Australia and other high- income countries in recent years. On the basis of ecological observations, and the known immunologic characteristics of whole-cell pertussis (wP) compared with acellular pertussis (aP) vaccines, we hypothesized that wP vaccination in infancy protects against the development of food allergy.

OBJECTIVE

To determine whether infants who receive wP in infancy were less likely to develop IgE-mediated food allergy than those who received aP.

METHODS

Retrospective cohort-nested case-control study of Australian children born in the period 1997 to 1999, the period of transition from using wP-containing to aP-containing vaccines. Children diagnosed with IgE-mediated food allergy were individually matched to 10 controls by date of birth, socioeconomic decile, and jurisdiction of birth. The odds ratio of vaccination with wP versus aP among cases and matched controls was calculated using conditional logistic regression.

RESULTS

The odds ratio of receiving the first dose as wP (rather than aP) among cases of food allergy compared with controls was 0.77 (95% CI, 0.62-0.95). The results of secondary analyses (any dose as wP vs aP-only, and wP-only vs aP-only) were broadly similar.

CONCLUSIONS

Australian infants who received wP vaccines were less likely to be diagnosed with food allergy in childhood than contemporaneous children who received aP vaccines. If a protective effect is confirmed in a randomized controlled trial, wP or mixed wP and aP vaccination schedules could form part of an effective strategy for combating the rise in food allergies.

Extremely Preterm Infants Have Significant Alterations in Their Conventional T Cell Compartment during the First Weeks of Life

Extremely preterm neonates are particularly susceptible to infections, likely because of severely impaired immune function. However, little is known on the composition of the T cell compartment in early life in this vulnerable population. We conducted a comprehensive phenotypic flow cytometry-based longitudinal analysis of the peripheral conventional T cell compartment of human extremely low gestational age neonates (ELGAN) with extremely low birth weight (ELBW; <1000 g) participating in a randomized placebo-controlled study of probiotic supplementation. PBMCs from ELGAN/ELBW neonates were collected at day 14, day 28, and postmenstrual week 36. Comparisons were made with full-term 14-d-old neonates. Total CD4⁺ and CD8⁺ T cell frequencies were markedly lower in the preterm neonates. The reduction was more pronounced among the CD8⁺ population, resulting in an increased CD4/CD8 ratio. The preterm infants were also more Th2 skewed than the full-term infants. Although the frequency of regulatory T cells seemed normal in the ELGAN/ELBW preterm neonates, their expression of the homing receptors α4β7, CCR4, and CCR9 was altered. Notably, ELGAN/ELBW infants developing necrotizing enterocolitis before day 14 had higher expression of CCR9 in CD4⁺T cells at day 14. Chorioamnionitis clearly associated with reduced T regulatory cell frequencies and functional characteristics within the preterm group. Finally, probiotic supplementation with Lactobacillus reuteri did not impose any phenotypic changes of the conventional T cell compartment. In conclusion, notable immaturities of the T cell compartment in ELGAN/ELBW neonates may at least partially explain their increased susceptibility to severe immune-mediated morbidities.

Evolution of pathologic T-cell subsets in patients with atopic dermatitis from infancy to adulthood

BACKGROUND

The circulating immune phenotype was defined in adults and young children with early atopic dermatitis (AD), but chronologic changes in the blood of infants and children with AD through adolescence have not been explored.

OBJECTIVE

We sought to compare immune activation and cytokine polarization in the blood of 0- to 5-year-old (n = 39), 6- to 11-year-old (n = 26), 12- to 17-year-old (n = 21) and 18-year-old or older (n = 43) patients with AD versus age-matched control subjects.

METHODS

Flow cytometry was used to measure IFN-γ, IL-9, IL-13, IL-17, and IL-22 cytokine levels in CD4⁺/CD8⁺ T cells, with inducible costimulator molecule and HLA-DR defining midterm and long-term T-cell activation, respectively, within skin-homing/cutaneous lymphocyte antigen (CLA)⁺ versus systemic/CLA^- T cells. Unsupervised clustering differentiated patients based on their blood biomarker frequencies.

RESULTS

Although CLA⁺ T_H1 frequencies were significantly lower in infants with AD versus all older patients (P < .01), frequencies of CLA⁺ T_H2 T cells were similarly expanded across all AD age groups compared with control subjects (P < .05). After infancy, CLA^- T_H2 frequencies were increased in patients with AD in all age groups, suggesting systemic immune activation with disease chronicity. IL-22 frequencies serially increased from normal levels in infants to highly significant levels in adolescents and adults compared with levels in respective control subjects (P < .01). Unsupervised clustering aligned the AD profiles along an age-related spectrum from infancy to adulthood (eg, inducible costimulator molecule and IL-22).

CONCLUSIONS

The adult AD phenotype is achieved only in adulthood. Unique cytokine signatures characterizing individual pediatric endotypes might require age-specific therapies. Future longitudinal studies, comparing the profile of patients with cleared versus persistent pediatric AD, might define age-specific changes that predict AD clearance.

Impact of pregravid obesity on maternal and fetal immunity: Fertile grounds for reprogramming

Maternal pregravid obesity results in several adverse health outcomes during pregnancy, including increased risk of gestational diabetes, preeclampsia, placental abruption, and complications at delivery. Additionally, pregravid obesity and in utero exposure to high fat diet have been shown to have detrimental effects on fetal programming, predisposing the offspring to adverse cardiometabolic, endocrine, and neurodevelopmental outcomes. More recently, a deeper appreciation for the modulation of offspring immunity and infectious disease-related outcomes by maternal pregravid obesity has emerged. This review will describe currently available animal models for studying the impact of maternal pregravid obesity on fetal immunity and review the data from clinical and animal model studies. We also examine the burden of pregravid obesity on the maternal-fetal interface and the link between placental and systemic inflammation. Finally, we discuss future studies needed to identify key mechanistic underpinnings that link maternal inflammatory changes and fetal cellular reprogramming events.

Dissecting the defects in the neonatal CD8+ T-cell response

The neonatal period presents a complex scenario where the threshold of reactivity toward colonizing microbiota, maternal antigens, autoantigens, and pathogens must be carefully moderated and balanced. CD8⁺ T cells are critical for the response against intracellular bacteria and viruses, but this immune compartment maintains altered function relative to adult counterparts because of the unique challenges which infants face. Here, we review our current understanding of the factors which may promote the attenuation and altered function of the neonatal CD8⁺ T-cell response and potential avenues for future study. Specifically, we have focused on the neonatal CD8⁺ T-cell ontogeny, memory formation, TCR structure and repertoire, TCR inhibitory receptors, and the clinical implications of altered neonatal CD8⁺ T-cell function. Special emphasis has been placed on examining the response of preterm neonates relative to term neonates and adults.

Imprinting and Editing of the Human CD4 T Cell Response to Influenza Virus

Immunity to influenza is unique among pathogens, in that immune memory is established both via intermittent lung localized infections with highly variable influenza virus strains and by intramuscular vaccinations with inactivated protein-based vaccines. Studies in the past decades have suggested that the B cell responses to influenza infection and vaccination are highly biased by an individual's early history of influenza infection. This reactivity likely reflects both the competitive advantage that memory B cells have in an immune response and the relatively limited diversity of epitopes in influenza hemagglutinin that are recognized by B cells. In contrast, CD4 T cells recognize a wide array of epitopes, with specificities that are heavily influenced by the diversity of influenza antigens available, and a multiplicity of functions that are determined by both priming events and subsequent confrontations with antigens. Here, we consider the events that prime and remodel the influenza-specific CD4 T cell response in humans that have highly diverse immune histories and how the CD4 repertoire may be edited in terms of functional potential and viral epitope specificity. We discuss the consequences that imprinting and remodeling may have on the potential of different human hosts to rapidly respond with protective cellular immunity to infection. Finally, these issues are discussed in the context of future avenues of investigation and vaccine strategies.

CD4 T cells are required for maintenance of CD8 TRM cells and virus control in the brain of MCMV-infected newborn mice

Cytomegalovirus (CMV) infection is a significant public health problem. Congenital CMV infection is a leading infectious cause of long-term neurodevelopmental sequelae, including mental retardation and sensorineural hearing loss. Immune protection against mouse cytomegalovirus (MCMV) is primarily mediated by NK cells and CD8⁺ T cells, while CD4⁺ T cells are not needed for control of MCMV in majority of organs in immunocompetent adult mice. Here, we set out to determine the role of CD4⁺ T cells upon MCMV infection of newborn mice. We provide evidence that CD4⁺ T cells are essential for clearance of MCMV infection in brain of neonatal mice and for prevention of recurrence of latent MCMV. In addition, we provide evidence that CD4⁺ T cells are required for induction and maintenance of tissue-resident memory CD8⁺ T cells in the brain of mice perinatally infected with MCMV.

HIV-Exposed Uninfected Infants Have Increased Regulatory T Cells That Correlate With Decreased T Cell Function

Background: HIV-exposed uninfected infants (HEU) are at higher risk of severe infections, hospitalizations and death compared with HIV-unexposed uninfected infants (HUU), but the immune deficit underlying it is not known. To address this gap, we investigated T cell functionality and its relationship to phenotypic profiles of T cells and antigen presenting cells (APC) in HEU and HUU.

Methods: Blood mononuclear cells from 55 HEU and 16 HUU were stimulated with Staphylococcal Enterotoxin B (SEB) or mock for 72 h, and tested by flow cytometry for proliferation and expression of Th1, Th2, and regulatory (Treg) markers. In parallel, cells were phenotypically assessed for differentiation profiles of Treg, conventional T cell (Tconv) and APC in unstimulated cells.

Results: HEU had lower CD4+ functional responses to SEB/mock and similar CD8+ responses compared with HUU. In the phenotypic T cell panel, HEU showed higher proportions of CD4+ and CD8+ Treg expressing IL10, FOXP3, and CD25; higher effector Tconv and Treg; and lower naïve and CD4+TGFβ+ Treg compared with HUU. In the phenotypic APC panel, HEU showed higher proportions of CD1c+ cDC2, CD123+ pDC, CD16+ inflammatory monocytes and cDC and higher expression of CD103 on CD1c-CD123-CD16-cDC1 compared with HUU. Regression analyses adjusted for HIV exposure and multiple comparisons showed that higher CD8+IL10+ and CD8+FOXP3+ Treg in unstimulated cells were associated with lower CD8+ T cell functional responses to SEB/mock. Functionality was not affected by Tconv differentiation, but higher APC activation in aggregate was associated with higher CD8+IL10+ Treg responses to SEB.

Conclusions: T cell functionality was decreased in HEU compared with HUU. High CD8+ Treg proportions were the most important predictors of decreased T cell functionality in HEU and HUU.

Interleukin 15 blockade protects the brain from cerebral ischemia-reperfusion injury

Acute ischemic stroke is followed by a complex interplay between the brain and the immune system in which ischemia-reperfusion leads to a detrimental inflammatory response that causes brain injury. In the brain, IL-15 is expressed by astrocytes, neurons and microglia. Previous study showed that ischemia-reperfusion induces expression of IL-15 by astrocytes. Transgenic over-expression of IL-15 in astrocytes aggravates ischemia-reperfusion brain damage by increasing the levels and promoting the effector functions of CD8⁺ T and NK cells. Treatment of neonatal rats with IL-15 neutralizing antibody before hypoxia-ischemia induction reduces the infarct volume. However, as stroke-induced inflammatory responses differ between neonate and adult brain, the effects of IL-15 blockade on the injury and immune response arising from stroke in adult animals has remained unclear. In this study, we examined the effect of post-ischemia/reperfusion IL-15 blockade on the pathophysiology of cerebral ischemia-reperfusion in adult mice. Using a cerebral ischemia-reperfusion model, we compared infarct size and the infiltrating immune cells in the brain of wild type (WT) mice and Il15^-/- mice lacking NK and memory CD8⁺ T cells. We also evaluated the effects of IL-15 neutralizing antibody treatment on brain infarct volume, motor function, and the status of brain-infiltrating immune cells in WT mice. Il15^-/- mice show a smaller infarct volume and lower numbers of activated brain-infiltrating NK, CD8⁺ T, and CD4⁺ T cells compared to WT mice after cerebral ischemia-reperfusion. Post-ischemia/reperfusion IL-15 blockade reduces infarct size and improves motor and locomotor activity. Furthermore, IL-15 blockade reduces the effector function of NK, CD8⁺ T, and CD4⁺ T cells in the ischemia-reperfusion brain of WT mice. Ablation of IL-15 responses after cerebral ischemia-reperfusion ameliorates brain injury in adult mice. Therefore, targeting IL-15 is a potential effective therapy for ischemic stroke.

The role of the microbiome in childhood asthma

It is now well established that the healthy bronchial tree contains a microbiome distinct from that of the upper respiratory tract and that the lung microbiome may be dysregulated in individuals with a chronic respiratory disease, such as asthma. In addition, after birth, gut microbes interact with the host tissue, especially with the lymphatic tissue, thereby guaranteeing efficient immune activation. This review focuses on the available literature on the relationships between the gut microbiome, immune function and asthma in childhood, as well as the therapeutic strategies aimed at acting on the modulation of the microbiome.

Development of Asthma in Inner-City Children: Possible Roles of MAIT Cells and Variation in the Home Environment

Humans have populations of innate-like T lymphocytes with an invariant TCR α-chain that recognize nonpeptide Ags, including invariant NKT (iNKT) cells and mucosal-associated invariant T (MAIT) cells. iNKT cell involvement in human asthma is controversial, whereas there has been little analysis of MAIT cells. Using peripheral blood cells from 110 participants from the Urban Environment and Childhood Asthma (URECA) birth cohort study, these cells were analyzed for number and function. We determined whether iNKT cell or MAIT cell frequency at 1 y is correlated with the cytokine polarization of mainstream CD4+ T cells and/or the development of asthma by age 7 y. Dust samples from 300 houses were tested for iNKT cell antigenic activity. Our results show that a higher MAIT cell frequency at 1 y of age was associated with a decreased risk of asthma by age 7 y. The frequency of MAIT cells was associated with increased production of IFN-γ by activated CD4+ T cells from the URECA cohort. iNKT cell antigenic activity in bedroom dust samples was associated with higher endotoxin concentration and also with reduced risk of asthma. In conclusion, MAIT cell frequency at 1 y may reflect the tendency of the immune system toward Th1 responses and is associated with protection from asthma. Additionally, iNKT cell antigenic activity may be a marker of houses with increased microbial exposures and therefore also with protection from asthma.

Supplementing dams with both arachidonic and docosahexaenoic acid has beneficial effects on growth and immune development

Omega-3 long-chain polyunsaturated fatty acids (LCPUFAS) modulate immune cells in vitro and in vivo. This study investigated the effects of enriching the maternal diet with the n-6 and n-3 LCPUFAs, arachidonic (20:4n-6, 0.6%wt ARA) and docosahexaenoic acid (22:6n-3, 0.32%wt DHA), or 1:1 and 2:1 ratios (ARA: DHA) on total lipids in milk, total lipids, and immunophenotypes in plasma, lymph nodes, and spleen from isolated immune cells from 28d old pups. From day 15 of gestation to day 3 pp, Sprague-Dawley dams were fed a commercial chow. On day 3 pp litters were culled and pups (4 males and 2 females) randomly cross-fostered to dams who were randomized to one of the 5 experimental diets resulting in 20 male and 10 female pups/diet group. Dams fed ARA or ARA: DHA had 28-36% more 20:4n-6 in milk and feeding DHA or ARA: DHA doubled 22:6n-3 in milk lipids (P<0.05). Feeding 1:1 or 2:1 ARA: DHA resulted in greater pup weight at weaning (P<0.05). Compared to the control pups, ARA + DHA fed pups had a lower proportion of splenic CD45RA+ lymphocytes. In summary, postpartum supplementation with a combination of ARA + DHA, compared to ARA or DHA alone, resulted in a higher content of ARA and DHA in dam's milk and tissues and had positive effects on growth, accompanied by evidence of progression toward a mature immune phenotype, and suggests a need for ARA when DHA is supplemented in the early diet. Additional investigations are needed of ARA immunomodulation to better understand and estimate nutritional requirements for LCPUFAs during early development.

Vaccine responses in newborns

Immunisation of the newborn represents a key global strategy in overcoming morbidity and mortality due to infection in early life. Potential limitations, however, include poor immunogenicity, safety concerns and the development of tolerogenicity or hypo-responsiveness to either the same antigen and/or concomitant antigens administered at birth or in the subsequent months. Furthermore, the neonatal immunological milieu is polarised towards Th2-type immunity with dampening of Th1-type responses and impaired humoral immunity, resulting in qualitatively and quantitatively poorer antibody responses compared to older infants. Innate immunity also shows functional deficiency in antigen-presenting cells: the expression and signalling of Toll-like receptors undergo maturational changes associated with distinct functional responses. Nevertheless, the effectiveness of BCG, hepatitis B and oral polio vaccines, the only immunisations currently in use in the neonatal period, is proof of concept that vaccines can be successfully administered to the newborn via different routes of delivery to induce a range of protective mechanisms for three different diseases. In this review paper, we discuss the rationale for and challenges to neonatal immunisation, summarising progress made in the field, including lessons learnt from newborn vaccines in the pipeline. Furthermore, we explore important maternal, infant and environmental co-factors that may impede the success of current and future neonatal immunisation strategies. A variety of approaches have been proposed to overcome the inherent regulatory constraints of the newborn innate and adaptive immune system, including alternative routes of delivery, novel vaccine configurations, improved innate receptor agonists and optimised antigen-adjuvant combinations. Crucially, a dual strategy may be employed whereby immunisation at birth is used to prime the immune system in order to improve immunogenicity to subsequent homologous or heterologous boosters in later infancy. Similarly, potent non-specific immunomodulatory effects may be elicited when challenged with unrelated antigens, with the potential to reduce the overall risk of infection and allergic disease in early life.

Protecting the Newborn and Young Infant from Infectious Diseases: Lessons from Immune Ontogeny

Infections in the first year of life are common and often severe. The newborn host demonstrates both quantitative and qualitative differences to the adult in nearly all aspects of immunity, which at least partially explain the increased susceptibility to infection. Here we discuss how differences in susceptibility to infection result not out of a state of immaturity, but rather reflect adaptation to the particular demands placed on the immune system in early life. We review the mechanisms underlying host defense in the very young, and discuss how specific developmental demands increase the risk of particular infectious diseases. In this context, we discuss how this plasticity, i.e. the capacity to adapt to demands encountered in early life, also provides the potential to leverage protection of the young against infection and disease through a number of interventions.

Eosinophilia in infants with food protein-induced enterocolitis syndrome in Japan

BACKGROUND

Many Japanese infants with food protein-induced enterocolitis syndrome (FPIES) show eosinophilia, which has been thought to be a characteristic of food protein-induced proctocolitis (FPIP).

METHODS

To elucidate the characteristics of eosinophilia in Japanese FPIES patients, 113 infants with non-IgE-mediated gastrointestinal food allergy due to cow's milk were enrolled and classified into FPIES (n = 94) and FPIP (n = 19).

RESULTS

The percentage of peripheral blood eosinophils (Eo) was increased in most FPIES patients (median, 7.5%), which was comparable with that in FPIP patients (9.0%). Among FPIES patients, Eo was the highest in patients who had vomiting, bloody stool, and diarrhea simultaneously (12.9%) and lowest in patients with diarrhea alone (3.2%). Eo showed a significant positive correlation with the incidence of vomiting (Cramer's V = 0.31, p < 0.005) and bloody stool (Cramer's V = 0.34, p < 0.0005). A significant difference was found in Eo between early- (≤10 days, n = 56) and late-onset (>10 days, n = 38) FPIES (median, 9.8% vs. 5.4%; p < 0.005). IL-5 production by peripheral blood T cells stimulated with cow's milk protein in early-onset FPIES was significantly higher than that in late-onset FPIES (67.7 pg/mL vs. 12.5 pg/mL, p < 0.01), and showed a significant positive correlation with Eo (rs = 0.60, p < 0.01).

CONCLUSIONS

This study demonstrated two types of eosinophilia in Japanese FPIES infants: conspicuous and mild eosinophilia in early- and late-onset FPIES patients, respectively. Conspicuous eosinophilia in early-onset FPIES is suggested to be caused by abnormally high IL-5 production.

Gastrointestinal Microbiome Dysbiosis in Infant Mice Alters Peripheral CD8+ T Cell Receptor Signaling

We recently reported that maternal antibiotic treatment (MAT) of mice in the last days of pregnancy and during lactation dramatically alters the density and composition of the gastrointestinal microbiota of their infants. MAT infants also exhibited enhanced susceptibility to a systemic viral infection and altered adaptive immune cell activation phenotype and function. CD8⁺ effector T cells from MAT infants consistently demonstrate an inability to sustain interferon gamma (IFN-γ) production in vivo following vaccinia virus infection and in vitro upon T cell receptor (TCR) stimulation. We hypothesize that T cells developing in infant mice with gastrointestinal microbiota dysbiosis and insufficient toll-like receptor (TLR) exposure alters immune responsiveness associated with intrinsic T cell defects in the TCR signaling pathway and compromised T cell effector function. To evaluate this, splenic T cells from day of life 15 MAT infant mice were stimulated in vitro with anti-CD3 and anti-CD28 antibodies prior to examining the expression of ZAP-70, phosphorylated ZAP-70, phospho-Erk-1/2, c-Rel, total protein tyrosine phosphorylation, and IFN-γ production. We determine that MAT infant CD8⁺ T cells fail to sustain total protein tyrosine phosphorylation and Erk1/2 activation. Lipopolysaccharide treatment in vitro and in vivo, partially restored IFN-γ production in MAT effector CD8⁺ T cells and reduced mortality typically observed in MAT mice following systemic viral infection. Our results demonstrate a surprising dependence on the gastrointestinal microbiome and TLR ligand stimulation toward shaping optimal CD8⁺ T cell function during infancy.

Preferential expression of IGHV and IGHD encoding antibodies with exceptionally long CDR3H and a rapid global shift in transcriptome characterizes development of bovine neonatal immunity

With an objective to understand natural development of bovine neonatal immunity, we analyzed 18 RNA-seq libraries from peripheral blood lymphocytes of three neonatal calves pre- (day 0) and post-colostrum (7, 14 and 28) uptake as compared to their dams. A significant global shift in neonatal transcriptome occurs within first week post-birth, in contrast to dams, with an upregulation of 717 genes. Global pathway analysis of the transcriptome revealed 110 differentially expressed immune-related genes, such as, complement, MHCII, chemokine receptors, defensins and cytokines, at birth. The signaling molecules (LAX1, BLK) and transcription factors (GATA3, FOXP3) are expressed at high levels. High expression of GATA3 transcription factor at birth seems to skew the neonatal immune response towards TH2 type. The high levels of T-cell signaling molecules, CD3G and CD3D, at birth are important in neonatal T cell development. Unlike adults, IGKC expression is high in the neonates where IGKV12 is preferentially expressed at birth. But IGLC is predominant in both neonates and adult where IGLV3.4 is preferentially expressed in B cells at birth. Both IGHM and IGHD are expressed at birth and IGHM achieves adult levels by day 7. This is followed by IGHA and IGHG expression 14-28 days post-birth. Importantly, preferential expression of IGHV1S1(BF4E9) and longest IGHD2(D_H2) genes that encode immunoglobulin with exceptionally long CDR3H at birth indicates their critical role, as B cell antigen receptor, in the B cell development via idiotype-anti-idiotype interactions. The transcriptome signatures described here permit assessment bovine neonatal immunocompetence. Bovine neonates acquire innate and IgM-mediated humoral immunocompetence within first week post-birth.

Protection against Streptococcus pneumoniae Invasive Pathogenesis by a Protein-Based Vaccine Is Achieved by Suppression of Nasopharyngeal Bacterial Density during Influenza A Virus Coinfection

An increase in Streptococcus pneumoniae nasopharynx (NP) colonization density during a viral coinfection initiates pathogenesis. To mimic natural S. pneumoniae pathogenesis, we commensally colonized the NPs of adult C57BL/6 mice with S. pneumoniae serotype (ST) 6A or 8 and then coinfected them with mouse-adapted H1N1 influenza A virus (PR/8/34). S. pneumoniae established effective commensal colonization, and influenza virus coinfection caused S. pneumoniae NP density to increase, resulting in bacteremia and mortality. We then studied histidine triad protein D (PhtD), an S. pneumoniae adhesin vaccine candidate, for its ability to prevent invasive S. pneumoniae disease in adult and infant mice. In adult mice, the efficacy of PhtD vaccination was compared with that of PCV13. Vaccination with PCV13 led to a greater reduction of S. pneumoniae NP density (>2.5 log units) than PhtD vaccination (∼1-log-unit reduction). However, no significant difference was observed with regard to the prevention of S. pneumoniae bacteremia, and there was no difference in mortality. Depletion of CD4⁺ T cells in PhtD-vaccinated adult mice, but not PCV13-vaccinated mice, caused a loss of vaccine-induced protection. In infant mice, passive transfer of antisera or CD4⁺ T cells from PhtD-vaccinated adult mice led to a nonsignificant reduction in NP colonization density, whereas passive transfer of antisera and CD4⁺ T cells was needed to cause a significant reduction in NP colonization density. For the first time, these data show an outcome with regard to prevention of invasive S. pneumoniae pathogenesis with a protein vaccine similar to that which occurs with a glycoconjugate vaccine despite a less robust reduction in NP bacterial density.

Timing of in utero malaria exposure influences fetal CD4 T cell regulatory versus effector differentiation

Background

In malaria-endemic areas, the first exposure to malaria antigens often occurs in utero when the fetal immune system is poised towards the development of tolerance. Children exposed to placental malaria have an increased risk of clinical malaria in the first few years of life compared to unexposed children. Recent work has suggested the potential of pregnancy-associated malaria to induce immune tolerance in children living in malaria-endemic areas. A study was completed to evaluate the effect of malaria exposure during pregnancy on fetal immune tolerance and effector responses.

Methods

Using cord blood samples from a cohort of mother-infant pairs followed from early in pregnancy until delivery, flow cytometry analysis was completed to assess the relationship between pregnancy-associated malaria and fetal cord blood CD4 and dendritic cell phenotypes.

Results

Cord blood FoxP3⁺ T_reg counts were higher in infants born to mothers with Plasmodium parasitaemia early in pregnancy (12–20 weeks of gestation; p = 0.048), but there was no association between T_reg counts and the presence of parasites in the placenta at the time of delivery (by loop-mediated isothermal amplification (LAMP); p = 0.810). In contrast, higher frequencies of activated CD4 T cells (CD25⁺FoxP3⁻CD127⁺) were observed in the cord blood of neonates with active placental Plasmodium infection at the time of delivery (p = 0.035). This population exhibited evidence of effector memory differentiation, suggesting priming of effector T cells in utero. Lastly, myeloid dendritic cells were higher in the cord blood of infants with histopathologic evidence of placental malaria (p < 0.0001).

Conclusion

Together, these data indicate that in utero exposure to malaria drives expansion of both regulatory and effector T cells in the fetus, and that the timing of this exposure has a pivotal role in determining the polarization of the fetal immune response.

The expression and function of human CD300 receptors on blood circulating mononuclear cells are distinct in neonates and adults

Neonates are more susceptible to infections than adults. This susceptibility is thought to reflect neonates' qualitative and quantitative defects in the adaptive and innate immune responses. Differential expression of cell surface receptors may result in altered thresholds of neonatal immune cell activation. We determined whether the expression and function of the lipid-binding CD300 family of receptors are different on neonatal immune cells compared to adult immune cells. A multiparametric flow cytometry analysis was performed to determine the expression of CD300 receptors on adult peripheral blood mononuclear cells and neonatal cord blood mononuclear cells. The expression of the CD300a inhibitory receptor was significantly reduced on cells from the newborn adaptive immune system, and neonatal antigen presenting cells exhibited a different CD300 receptors expression pattern. We also found differential LPS-mediated regulation of CD300 receptors expression on adult monocytes compared to cord blood monocytes, and that CD300c and CD300e-mediated activation was quantitatively different in neonatal monocytes. This is the first complete study examining the expression of CD300 receptors on human neonatal immune cells compared with adult immune cells. Significant differences in the expression and function of CD300 receptors may help to explain the peculiarities and distinctness of the neonatal immune responses.

A Model to Explain How the Bacille Calmette Guérin (BCG) Vaccine Drives Interleukin-12 Production in Neonates

The Bacille Calmette Guérin (BCG) vaccine is the only routine vaccination at birth that effectively induces neonatal T-helper 1 (Th1)-polarized immune responses. The primary cytokine that drives CD4+ T-cell Th1 differentiation is interleukin (IL)-12 p70, a heterodimeric cytokine composed of the IL-12 p35 and IL-12 p40 subunits. We therefore examined the mechanisms involved in BCG vaccine stimulation of IL-12 p35 and p40 production from human umbilical cord (neonatal) cells. We found that BCG bacilli did not upregulate IL-12 p35 mRNA production, but upregulated IL-12 p40 mRNA production in a Toll-like receptor (TLR)2-dependent manner, in human neonatal monocyte-derived dendritic cells (mdDCs). The combination of TLR2 signaling, Type I interferon (IFN), and Type II IFN induced maximal levels of IL-12 p35 and p40 mRNA production in human neonatal mdDCs. The cell-free supernatants of reconstituted BCG vaccine vials contained extracellular mycobacterial (BCG) DNA which could induce IFN-α (Type I IFN) production in human neonatal plasmacytoid dendritic cells (pDCs). BCG bacilli also stimulated human neonatal CD16lo natural killer (NK) cells to produce IFN-γ (Type II IFN) in a TLR2-dependent manner. We have therefore proposed a model where BCG vaccine could stimulate the combination of neonatal conventional DCs (cDCs), pDCs, and CD16lo NK cells to produce optimal neonatal IL-12 p35 and p40 (IL-12 p70) production and subsequent CD4+ T-cell Th1 polarization. An adjuvant that emulates the mechanism by which the BCG vaccine stimulates neonatal IL-12 p35 and p40 production could improve vaccine strategies at birth for protection against intracellular pathogens and toxins.

Next generation protein based Streptococcus pneumoniae vaccines

All currently available Streptococcus pneumoniae (Spn) vaccines have limitations due to their capsular serotype composition. Both the 23-valent Spn polysaccharide vaccine (PPV) and 7, 10, or 13-valent Spn conjugate vaccines (PCV-7, 10, -13) are serotype-based vaccines and therefore they elicit only serotype-specific immunity. Emergence of replacement Spn strains expressing other serotypes has consistently occurred following introduction of capsular serotype based Spn vaccines. Furthermore, capsular polysaccharide vaccines are less effective in protection against non-bacteremic pneumonia and acute otitis media (AOM) than against invasive pneumococcal disease (IPD). These shortcomings of capsular polysaccharide-based Spn vaccines have created high interest in development of non-serotype specific protein-based vaccines that could be effective in preventing both IPD and non-IPD infections. This review discusses the progress to date on development of Spn protein vaccine candidates that are highly conserved by all Spn strains, are highly conserved, exhibit maximal antigenicity and minimal reactogenicity to replace or complement the current capsule-based vaccines. Key to development of a protein based Spn vaccine is an understanding of Spn pathogenesis. Based on pathogenesis, a protein-based Spn vaccine should include one or more ingredients that reduce NP colonization below a pathogenic inoculum. Elimination of all Spn colonization may not be achievable or even advisable. The level of expression of a target protein antigen during pathogenesis is another key to the success of protein based vaccines.. As with virtually all currently licensed vaccines, production of a serum antibody response in response to protein based vaccines is anticipated to provide protection from Spn infections. A significant advantage that protein vaccine formulations can offer over capsule based vaccination is their potential benefits associated with natural priming and boosting to all strains of Spn. One of the most universal and comprehensive approaches of identifying novel vaccine candidates is the investigation of human sera from different disease stages of natural infections. Antigens that are robustly reactive in preliminary human serum screening constitute a pathogen-specific antigenome. This strategy has identified a number of Spn protein vaccine candidates that are moving forward in human clinical trials.

Engineering the Microbiome: a Novel Approach to Immunotherapy for Allergic and Immune Diseases

The incidence of immune disorders is growing parallel with practices associated with westernization, such as dietary changes, increased use of antibiotics, or elevated rates of Cesarean section. These practices can significantly impact the gut microbiota, the collection of bacteria residing in the human gastrointestinal tract, and subsequently disrupt the delicate balance existing between commensal flora and host immune responses. Restoring this balance by modifying the microbiota has thus emerged as a promising therapeutic approach. Here, we discuss the interaction between gut commensals and immunity, along with the potential of different interventions on the microbiota as treatment for inflammatory and allergic diseases.

Developmental Activation of the AHR Increases Effector CD4+ T Cells and Exacerbates Symptoms in Autoimmune Disease-Prone Gnaq+/- Mice

Perinatal environmental exposures are potentially important contributors to the increase in autoimmune diseases. Yet, the mechanisms by which these exposures increase self-reactive immune responses later in life are poorly understood. Autoimmune diseases require CD4(+) T cells for initiation, progression, and/or clinical symptoms; thus, developmental exposures that cause durable changes in CD4(+) T cells may play a role. Early life activation of the aryl hydrocarbon receptor (AHR) causes persistent changes in the response of CD4(+) T cells to infection later in life but whether CD4(+) T cells are affected by developmental exposure in the context of an autoimmune disease is unknown. Gnaq(+/-) mice develop symptoms of autoimmune disease similar to those measured clinically, and therefore can be used to evaluate gene-environment interactions during development on disease progression. Herein, we examined the effect of AHR activation in utero and via lactation, or solely via lactation, on disease onset and severity in adult Gnaq(+/-) offspring. Developmental activation of the AHR-accelerated disease in Gnaq(+/-) mice, and this correlates with increases in effector CD4(+) T-cell populations. Increased symptom onset and cellular changes due to early life AHR activation were more evident in female Gnaq(+/-) mice compared with males. These observations suggest that developmental AHR activation by pollutants, and other exogenous ligands, may increase the likelihood that genetically predisposed individuals will develop clinical symptoms of autoimmune disease later in life.

Reduced frequencies of polyfunctional CMV-specific T cell responses in infants with congenital CMV infection

PURPOSE

CMV infection remains a priority for vaccine development. Vaccination of infants could modify congenital infection and provide lifetime immunity. Properties of CMV-specific T cells associated with control of viral replication in early life have not been fully defined.

METHODS

CMV-specific CD4 and CD8 T cell responses were investigated in infants with congenital CMV infection and compared to adults with primary or chronic infection. PBMC were stimulated with UL83 (pp65) or UL122 (IE-2) peptide pools then stained with antibodies to markers of T cell subset (CD4 or CD8), phenotype (CD45RA, CCR7), or function (MIP1β, CD107, IFNγ, IL2) for flow cytometry analysis.

RESULTS

Detection of CMV pp65-specific CD4 T cells was less common in infants than adults. Responder cells were primarily effector memory (EM, CD45RA-CCR7-) in adults, but mixed memory subsets in infants. Detection of CMV pp65-specific CD8 T cells did not differ between the groups, but infants had lower frequencies of total responding cells and of MIP1β- or CD107-expressing cells. Responder cells were EM or effector memory RA (CD45RA + CCR7-) in all groups. Polyfunctional T cells were less commonly detected in infants than adults. Responses to IE-2 were detected in adults but not infants. All infants had detectable circulating CMV DNA at initial study (versus 60 % of adults with primary infection) despite longer duration of CMV infection.

CONCLUSIONS

Reduced frequencies and altered functional profile of CMV-specific CD4 and CD8 T cell responses were detected in infants compared to adults, and were associated with persistent CMV DNA in peripheral blood.

A Review of the CD4+ T Cell Contribution to Lung Infection, Inflammation and Repair with a Focus on Wheeze and Asthma in the Pediatric Population

Childhood asthma and wheezing are very common, especially in those born preterm. Genetic and environmental factors are associated with developing asthma and wheezing. Respiratory syncytial virus and rhinovirus infections have been implicated in playing a causal role in the development of childhood asthma and wheezing, perhaps by altering the development of the immune system. Several subtypes of asthma and wheezing have been described which involve different mechanisms of pathophysiology. Much of the recent work in the field of asthma research has focused on describing unique aspects of these disease subtypes, which could lead to new drug targets. Alterations in CD4+ T cells have been described with alterations in the T helper 1, 2, 17 and regulatory cell balance could provide valuable targets for the development of new treatment strategies for the various subtypes of disease. This review article focuses on factors involved in childhood asthma and wheeze and potential drug targets.