Neonatal immunity: how well has it grown up?

Neonatal CD4+ T cells have a characteristic transcriptome and epigenome and respond to TCR stimulation with proliferation and yet a limited immune response

The adaptive immune response is coordinated by CD4+ T cells, which determine the type and strength of the immune response and the effector cells involved. It has been reported that CD4+ T cells are less responsive in neonates, leading to low activation of the cellular response and poor antibody production by B cells. This low response is essential for the tolerant window that favors birth transition from the sterile environment in the womb to the outside world but leaves neonates vulnerable to infection, which is still an important health issue. Neonates have a high morbidity and mortality rate due to infections, and the molecular reasons are still understudied. We asked whether the neonatal naive CD4+ T cells have a genomic program that predisposes them to a low response. Therefore, we evaluated the transcriptome and epigenome of human neonatal and adult naive CD4+ T cells. Our results point to a gene expression profile forming a distinct regulatory network in neonatal cells, which favors proliferation and a low T-cell response. Such expression profile is supported by a characteristic epigenetic landscape of neonatal CD4+ T cells, which correlates with the characteristic transcriptome of the neonatal cells. These results were confirmed by experiments showing a low response to activation signals, higher proliferation, and lower expression of cytokines of neonatal CD4+ T cells as compared to adult cells. Understanding this network could lead to novel vaccine formulations and better deal with life-threatening diseases during this highly vulnerable period of our lives.

TLR4, MyD88, and TNF-α Expression in the Lungs of Akkaraman and Romanov Lambs in Response to LPS and LTA

Toll-like receptors are involved in the recognition of bacterial toxins, which cause infection in the respiratory system. This study aimed to evaluate microanatomical and histological alterations in the lungs of 24 healthy Akkaraman and Romanov lambs after the administration of lipoteichoic acid (LTA), lipopolysaccharide (LPS), and LTA + LPS and investigate the gene, protein, and immune expression levels of TLR4, MyD88, and TNF-α molecules, known to have immune functions. Microanatomical examinations showed thickened peribronchial and alveolar walls in the lungs of groups LTA, LPS, and LTA + LPS of both breeds due to immune cell infiltration. TLR4, MyD88, and TNF-α immunoexpressions were positive to varying degrees in the cytoplasm and nucleus of the bronchial and bronchiolar luminal epithelial cells, alveolar epithelial cells, and alveolar macrophages. TLR4 and TNF-α protein expressions were statistically different in the LPS-treated Romanov lambs, compared to the other groups. Among the Akkaraman lambs, TLR4 gene expression was significantly higher in group LPS, and among the Romanov lambs, TLR4, MyD88, and TNF-α gene expressions were significantly higher in group LTA + LPS. Therefore, TLR4, MyD88, and TNF-α molecules, involved in the immune response, were found to be expressed at different levels against LTA and LPS in the lungs of two different sheep breeds.

Glycoprotein N-linked glycans play a critical role in arenavirus pathogenicity

Several arenaviruses cause hemorrhagic fevers in humans with high case fatality rates. A vaccine named Candid#1 is available only against Junin virus (JUNV) in Argentina. Specific N-linked glycans on the arenavirus surface glycoprotein (GP) mask important epitopes and help the virus evade antibody responses. However the role of GPC glycans in arenavirus pathogenicity is largely unclear. In a lethal animal model of hemorrhagic fever-causing Machupo virus (MACV) infection, we found that a chimeric MACV with the ectodomain of GPC from Candid#1 vaccine was partially attenuated. Interestingly, mutations resulting in acquisition of N-linked glycans at GPC N83 and N166 frequently occurred in late stages of the infection. These glycosylation sites are conserved in the GPC of wild-type MACV, indicating that this is a phenotypic reversion for the chimeric MACV to gain those glycans crucial for infection in vivo. Further studies indicated that the GPC mutant viruses with additional glycans became more resistant to neutralizing antibodies and more virulent in animals. On the other hand, disruption of these glycosylation sites on wild-type MACV GPC rendered the virus substantially attenuated in vivo and also more susceptible to antibody neutralization, while loss of these glycans did not affect virus growth in cultured cells. We also found that MACV lacking specific GPC glycans elicited higher levels of neutralizing antibodies against wild-type MACV. Our findings revealed the critical role of specific glycans on GPC in arenavirus pathogenicity and have important implications for rational design of vaccines against this group of hemorrhagic fever-causing viruses.

Several arenaviruses cause severe hemorrhagic fevers in humans. The only vaccine against arenavirus infections is Candid#1, a live attenuated vaccine against Argentine hemorrhagic fever. So far, we have successfully attenuated additional one of the arenaviruses, Machupo virus, the causative agent of Bolivian hemorrhagic fever. Unraveling this attenuation mechanism might help the development of live-attenuated vaccines for other arenaviruses. In this study, we revealed that the specific glycans of the viral glycoproteins play an important role in pathogenicity in vivo. The glycans facilitate the virus to evade neutralizing antibodies. This study would contribute to the development of arenavirus vaccine candidates.

Bovine neonate is deficient in innate immunity at birth

With an objective to understand acquisition of innate immunity in bovine neonates, we analyzed perinatal expression of cytokine, adhesion molecule and complement component genes involved in innate and adaptive immune functions. Statistically robust transcriptomic analysis of 27 cytokines showed low IL1B, IL2 and IL7 but high IL23, TGFB1 and TGFB2 expression in bovine neonates post-birth. Unlike mice and humans, no T_H2 polarizing cytokine expression occurs in bovine neonates. Further, T_H17 and Treg differentiation in bovine neonates may differ from other species like mice and humans. Decreased IL7, IL23R, CXCR3 and increased TGFB1 and TGFB2 expression provides an immunosuppressive environment in the bovine neonate at birth. Transcriptomic analysis of 31 adhesion molecules showed rapid increase in ITGAL expression within a week post-birth in bovine neonates that permits acquisition of innate cytotoxic functions by granulocytes (antibody-mediated), cytotoxic T and NK cells. However, innate immune functions involving phagocytosis and platelet aggregation are deficient in bovine neonates at birth. Of twenty-seven, 18 complement component genes show no significant differential gene expression in neonates post-birth. But low expression of C1QA, C1QB, CQC, C1R and C2 compromises classical and lectin complement pathways mediated lytic function in bovine neonates. The complement-mediated cytotoxic functions, however, normalize between days 7 and 28 post-birth. To conclude, bovine neonate is immunosuppressed and deficient in innate immune competence at birth. Such differences with regard to global innate immune deficiency and lack of T_H2 polarization in bovine neonates have profound implications for designing vaccines to prevent neonatal infections. To conclude, species-specific unique characteristics of developing innate and adaptive immune system need to be taken into consideration while designing new immunization strategies to prevent neonatal mortality from infections.

Cord Blood-Based Approach to Assess Candidate Vaccine Adjuvants Designed for Neonates and Infants

Neonates and infants are particularly susceptible to infections, for which outcomes tend to be severe. Vaccination is a key strategy for preventing infectious diseases, but the protective immunity achieved through vaccination typically is weaker in infants than in healthy adults. One possible explanation for the poor acquisition of vaccine-induced immunity in infants is that their innate immune response, represented by toll-like receptors, is immature. The current system for developing pediatric vaccines relies on the confirmation of their safety and effectiveness in studies involving the use of mature animals or adult humans. However, creating vaccines for neonates and infants requires an understanding of their uniquely immature innate immunity. Here we review current knowledge regarding the innate immune system of neonates and infants and challenges in developing vaccine adjuvants for those children through analyses of cord blood.

Nutritional ecology and ecological immunology in degus: Does early nutrition affect the postnatal development of the immune function?

Environmental conditions experienced by developing animals have an impact on the development and maturity of the immune system. Specifically, the diet experienced during early development influences the maintenance and function of the immune system in young and adult animals. It is well known that exposure to low-protein diets during early development are related to an attenuation of immunocompetence in adulthood. While this functional linkage has been widely studied in altricial models' mammals, it has been little explored how the nutritional history modulates the immune function in precocial animals. We evaluated the effect of dietary protein consumed during early development on the immune function and the oxidative costs in the precocial Caviomorph rodent Octodon degus, or degu. We evaluated components of the acute phase response (APR) and oxidative parameters before and after immune challenge. We found that after the immune challenge, the juveniles on the low-protein dietary treatment exhibited an attenuation of body temperature but showed higher levels of lipid peroxidation than juvenile degus on the high-protein diet. We did not find a significant effect of the interaction between diet and immune challenge on body mass, levels of inflammatory proteins, nor in the total antioxidant capacity. Our results suggest that some components of the immune function and the oxidative status in the degu can be modulated by diet during development. However, the modulation would depend on the immune variables analyzed, and the characteristics of the immune system of precocial rodents.

Baboon envelope LVs efficiently transduced human adult, fetal, and progenitor T cells and corrected SCID-X1 T-cell deficiency

T cells represent a valuable tool for treating cancers and infectious and inherited diseases; however, they are mainly short-lived in vivo. T-cell therapies would strongly benefit from gene transfer into long-lived persisting naive T cells or T-cell progenitors. Here we demonstrate that baboon envelope glycoprotein pseudotyped lentiviral vectors (BaEV-LVs) far outperformed other LV pseudotypes for transduction of naive adult and fetal interleukin-7-stimulated T cells. Remarkably, BaEV-LVs efficiently transduced thymocytes and T-cell progenitors generated by culture of CD34⁺ cells on Delta-like ligand 4 (Dll4). Upon NOD/SCIDγC^-/- engraftment, high transduction levels (80%-90%) were maintained in all T-cell subpopulations. Moreover, T-cell lineage reconstitution was accelerated in NOD/SCIDγC^-/- recipients after T-cell progenitor injection compared with hematopoietic stem cell transplantation. Furthermore, γC-encoding BaEV-LVs very efficiently transduced Dll4-generated T-cell precursors from a patient with X-linked severe combined immunodeficiency (SCID-X1), which fully rescued T-cell development in vitro. These results indicate that BaEV-LVs are valuable tools for the genetic modification of naive T cells, which are important targets for gene therapy. Moreover, they allowed for the generation of gene-corrected T-cell progenitors that rescued SCID-X1 T-cell development in vitro. Ultimately, the coinjection of LV-corrected T-cell progenitors and hematopoietic stem cells might accelerate T-cell reconstitution in immunodeficient patients.

Development of Dog Immune System: From in Uterus to Elderly

Immune system recognize and fight back foreign microorganisms and inner modifications that lead to deficient cell and tissue functions. During a dog's life, the immune system needs to adapt to different physiological conditions, assuring surveillance and protection in a careful and controlled way. Pregnancy alters normal homeostasis, requiring a balance between immunity and tolerance. The embryos and fetus should be protected from infections, while the female dog must tolerate the growing of semi-allografts in her uterus. After birth, newborn puppies are at great risk of developing infectious diseases, because their immune system is in development and immune memory is absent. Passive transfer of immunity through colostrum is fundamental for puppy survival in the first weeks of life, but hampers the development of an active immune response to vaccination. At the end of life, dogs experience a decline in the structure and functional competence of the immune system, compromising the immune responses to novel antigenic challenges, such as infections and vaccines. Therefore, the current article reviews the general processes related to the development of the dog´s immune system, providing an overview of immune activity throughout the dog's life and its implications in canine health, and highlighting priority research goals.

Frank Beach Award Winner - The future of mental health research: Examining the interactions of the immune, endocrine and nervous systems between mother and infant and how they affect mental health

Pregnancy and the postpartum period are periods of significant change in the immune and endocrine systems. This period of life is also associated with an increased risk of mental health disorders in the mother, and an increased risk of developmental and neuropsychiatric disorders in her infant. The collective data described here supports the idea that peripartum mood disorders in mother and developmental disorders in her infant likely reflects multiple pathogeneses, stemming from various interactions between the immune, endocrine and nervous systems, thereby resulting in various symptom constellations. In this case, testing the mechanisms underlying specific symptoms of these disorders (e.g. deficits in specific types of learning or anhedonia) may provide a better understanding of the various physiological interactions and multiple etiologies that most likely underlie the risk of mental health disorders during this unique time in life. The goal here is to summarize the current understanding of how immune and endocrine factors contribute to maternal mental health, while simultaneously understanding the impact these unique interactions have on the developing brain of her infant.

Grafted Human iPSC-Derived Neural Progenitor Cells Express Integrins and Extend Long-Distance Axons Within the Developing Corticospinal Tract

After spinal cord injury (SCI), regeneration of adult motor axons such as axons in the corticospinal tract (CST) is severely limited. Alongside the inhibitory lesion environment, most neuronal subtypes in the mature central nervous system (CNS) are intrinsically unrepairable. With age, expression of growth-promoting proteins in neurons, such as integrins, declines. Integrin receptors allow communication between the extracellular matrix (ECM) and cell cytoskeleton and their expression in axons facilitates growth and guidance throughout the ECM. The α9β1 integrin heterodimer binds to tenascin-C (TN-C), an ECM glycoprotein expressed during development and after injury. In the mature CST however, expression of the α9 integrin subunit is downregulated, adding to the intrinsic inability of axons to regenerate. Our previous work has shown the α9 integrin subunit is not trafficked within axons of mature CST or rubrospinal tracts (RSTs). Thus, here we have utilized human induced pluripotent stem cell (iPSC)-derived neural progenitor cells (NPCs) to increase expression of α9 integrinwithin the developing rat CST. We demonstrate that human NPCs (hNPCs) express endogenous levels of both α9 and β1 integrin subunits as well as cortical neuron markers such as chicken ovalbumin upstream promoter transcription factor (COUP-TF) interacting protein 2 (Ctip2) and T-box brain 1 (Tbr1). In addition, lentivirus-mediated α9 integrin overexpression in hNPCs resulted in increased neurite outgrowth in the presence of TN-C in vitro. Following transplantation into the sensorimotor cortex of newborn rats, both wild type (WT) and α9-expressing hNPCs extend along the endogenous CST and retain expression of α9 throughout the length of the axonal compartment for up to 8 weeks following transplantation. These data highlight the growth potential of transplanted human iPSCs which may be a future target for regenerative therapies after nervous system injury.

A single vaccination with non-replicating MVA at birth induces both immediate and long-term protective immune responses

Newborns are considered difficult to protect against infections shortly after birth, due to their ineffective immune system that shows quantitative and qualitative differences compared to adults. However, here we show that a single vaccination of mice at birth with a replication-deficient live vaccine Modified Vaccinia Ankara [MVA] efficiently induces antigen-specific B- and T-cells that fully protect against a lethal Ectromelia virus challenge. Protection was induced within 2 weeks and using genetically modified mice we show that this protection was mainly T-cell dependent. Persisting immunological T-cell memory and neutralizing antibodies were obtained with the single vaccination. Thus, MVA administered as early as at birth induced immediate and long-term protection against an otherwise fatal disease and appears attractive as a new generation smallpox vaccine that is effective also in children. Moreover, it may have the potential to serve as platform for childhood vaccines as indicated by measles specific T- and B-cell responses induced in newborn mice vaccinated with recombinant MVA expressing measles antigens.

Incidence of Severe and Nonsevere Pertussis Among HIV-Exposed and -Unexposed Zambian Infants Through 14 Weeks of Age: Results From the Southern Africa Mother Infant Pertussis Study (SAMIPS), a Longitudinal Birth Cohort Study

Background. Maternal vaccination with tetanus, reduced-dose diphtheria, and acellular pertussis vaccine (Tdap) could be an effective way of mitigating the high residual burden of infant morbidity and mortality caused by Bordetella pertussis. To better inform such interventions, we conducted a burden-of-disease study to determine the incidence of severe and nonsevere pertussis among a population of Zambian infants.

Methods. Mother–infant pairs were enrolled at 1 week of life, and then seen at 2- to 3-week intervals through 14 weeks of age. At each visit, nasopharyngeal (NP) swabs were obtained from both, and symptoms were catalogued. Using polymerase chain reaction (PCR) to identify cases, and a severity scoring system to triage these into severe/nonsevere, we calculated disease incidence using person-time at risk as the denominator.

Results. From a population of 1981 infants, we identified 10 with clinical pertussis, for an overall incidence of 2.4 cases (95% confidence interval [CI], 1.2–4.2) per 1000 infant-months and a cumulative incidence of 5.2 cases (95% CI, 2.6–9.0) per 1000 infants. Nine of 10 cases occurred within a 3-month window (May–July 2015), with highest incidence between birth and 6 weeks of age (3.5 cases per 1000 infant-months), concentrated among infants prior to vaccination or among those who had only received 1 dose of Diphtheria Tetanus whole cell Pertussis (DTwP). Maternal human immunodeficiency virus (HIV) modestly increased the risk of infant pertussis (risk ratio, 1.8 [95% CI, .5–6.9]). Only 1 of 10 infant cases qualified as having severe pertussis. The rest presented with the mild and nonspecific symptoms of cough, coryza, and/or tachypnea. Notably, cough durations were long, exceeding 30 days in several cases, with PCRs repeatedly positive over time.

Conclusions. Pertussis is circulating freely among this population of Zambian infants but rarely presents with the classical symptoms of paroxysmal cough, whooping, apnea, and cyanosis. Maternal HIV appears to increase the risk, while lack of effective exposure to DTwP increased the risk.

Development and Function of the Mucosal Immune System in the Upper Respiratory Tract of Neonatal Calves

Respiratory infections remain the second most common cause of clinical disease and mortality in newborn calves, which has led to increased interest in using vaccines early in life to mitigate this risk. Intranasal vaccination of neonatal calves can be an effective strategy to circumvent vaccine interference by maternal antibody, but this raises questions regarding onset of immune competence in the upper respiratory tract (URT) following birth. Little is known, however, about the development and function of mucosa-associated lymphoid tissue (MALT) in the URT of newborn calves and what factors, including the commensal microbiome, contribute to this early development. We review the structure, development, and function of MALT in the bovine URT during the first six weeks of life and identify knowledge gaps regarding this early developmental time. This information is critical when designing vaccination programs for young calves, especially when targeting respiratory pathogens that may reside within the commensal microbiome.

Global gene expression analysis combined with a genomics approach for the identification of signal transduction networks involved in postnatal mouse myocardial proliferation and development

Mammalian cardiomyocytes may permanently lose their ability to proliferate after birth. Therefore, studying the proliferation and growth arrest of cardiomyocytes during the postnatal period may enhance the current understanding regarding this molecular mechanism. The present study identified the differentially expressed genes in hearts obtained from 24 h-old mice, which contain proliferative cardiomyocytes; 7-day-old mice, in which the cardiomyocytes are undergoing a proliferative burst; and 10-week-old mice, which contain growth-arrested cardiomyocytes, using global gene expression analysis. Furthermore, myocardial proliferation and growth arrest were analyzed from numerous perspectives, including Gene Ontology annotation, cluster analysis, pathway enrichment and network construction. The results of a Gene Ontology analysis indicated that, with increasing age, enriched gene function was not only associated with cell cycle, cell division and mitosis, but was also associated with metabolic processes and protein synthesis. In the pathway analysis, 'cell cycle', proliferation pathways, such as the 'PI3K-AKT signaling pathway', and 'metabolic pathways' were well represented. Notably, the cluster analysis revealed that bone morphogenetic protein (BMP)1, BMP10, cyclin E2, E2F transcription factor 1 and insulin like growth factor 1 exhibited increased expression in hearts obtained from 7-day-old mice. In addition, the signal transduction pathway associated with the cell cycle was identified. The present study primarily focused on genes with altered expression, including downregulated anaphase promoting complex subunit 1, cell division cycle (CDC20), cyclin dependent kinase 1, MYC proto-oncogene, bHLH transcription factor and CDC25C, and upregulated growth arrest and DNA damage inducible α in 10-week group, which may serve important roles in postnatal myocardial cell cycle arrest. In conclusion, these data may provide important information regarding myocardial proliferation and development.

Lifetime Modulation of the Pain System via Neuroimmune and Neuroendocrine Interactions

Chronic pain is a debilitating condition that still is challenging both clinicians and researchers. Despite intense research, it is still not clear why some individuals develop chronic pain while others do not or how to heal this disease. In this review, we argue for a multisystem approach to understand chronic pain. Pain is not only to be viewed simply as a result of aberrant neuronal activity but also as a result of adverse early-life experiences that impact an individual's endocrine, immune, and nervous systems and changes which in turn program the pain system. First, we give an overview of the ontogeny of the central nervous system, endocrine, and immune systems and their windows of vulnerability. Thereafter, we summarize human and animal findings from our laboratories and others that point to an important role of the endocrine and immune systems in modulating pain sensitivity. Taking "early-life history" into account, together with the past and current immunological and endocrine status of chronic pain patients, is a necessary step to understand chronic pain pathophysiology and assist clinicians in tailoring the best therapeutic approach.

Immunoglobulin-A Profile in Breast Milk from Mothers Delivering Full Term and Preterm Infants

Recent advances in the care of low-birth-weight and preterm neonates have stimulated research into the best dietetic program to improve their survival and short/long term outcome. Some components of human milk that cannot be included in artificial formulas may be critical for survival. Of these, immunoglobulins are important, and in particular secretory immunoglobulins A (sIgA). The concentration of secretory IgA was measured by immunoblotting (an immunoelectrophoretic technique having high specificity and reliability) in milk from mothers delivering at term (TM) or prematurely (PM). In both groups, IgA concentrations were high very early on but quickly decreased during the first week of lactation. The early IgA mean concentration was higher in PM than in TM but, because of high variability in PM milk, the difference rarely reached statistical significance. This variability during lactation reflects the important role of human milk in supplying immunological factors to cope with the gastrointestinal absorption of high molecular weight proteins in the first days of life. Immunological protection is particularly critical for a preterm baby, so it is important to promote feeding with its own mother's milk if possible, paying strict attention to the timing of milk collection.

Development of immune organs and functioning in humans and test animals: Implications for immune intervention studies

A healthy immune status is mostly determined during early life stages and many immune-related diseases may find their origin in utero and the first years of life. Therefore, immune health optimization may be most effective during early life. This review is an inventory of immune organ maturation events in relation to developmental timeframes in minipig, rat, mouse and human. It is concluded that time windows of immune organ development in rodents can be translated to human, but minipig reflects the human timeframes better; however the lack of prenatal maternal-fetal immune interaction in minipig may cause less responsiveness to prenatal intervention. It is too early to conclude which immune parameters are most appropriate, because there are not enough comparative immune parameters. Filling these gaps will increase the predictability of results observed in experimental animals, and guide future intervention studies by assessing relevant parameters in the right corresponding developmental time frames.

Transplant Tolerance Induction in Newborn Infants: Mechanisms, Advantages, and Potential Strategies

Although several tolerance induction protocols have been successfully implemented in adult renal transplantation, no tolerance induction approach has, as yet, been defined for solid organ transplantations in young infants. Pediatric transplant recipients have a pressing demand for the elaboration of tolerance induction regimens. Indeed, since they display a longer survival time, they are exposed to a higher level of risks linked to long-term immunosuppression (IS) and to chronic rejection. Interestingly, central tolerance induction may be of great interest in newborns, because of their immunological immaturity and the important role of the thymus at this early stage in life. The present review aims to clarify mechanisms and strategies of tolerance induction in these immunologically premature recipients. We first introduce the discovery and mechanisms of neonatal tolerance in murine experimental models and subsequently analyze tolerance induction in human newborn infants. Hematopoietic mixed chimerism in neonates is also discussed based on in utero hematopoietic stem cell (HSC) transplant studies. Then, we review the recent advances in tolerance induction approaches in adults, including the infusion of HSCs associated with less toxic conditioning regimens, regulatory T cells/facilitating cells/mesenchymal stem cells transplantation, costimulatory blockade, and thymus manipulation. Finally, IS withdrawal in pediatric solid organ transplant is discussed. In conclusion, the establishment of transplant tolerance induction in infants is promising and deserves further investigations. Future studies could focus on the selection of patients, on less toxic conditioning regimens, and on biomarkers for IS minimization or withdrawal.

The transfer and decay of maternal antibody against Shigella sonnei in a longitudinal cohort of Vietnamese infants

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Shigella sonnei is an emergent and highly drug resistant diarrheal pathogen.

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The half-life of maternal S. sonnei IgG in infants is 43 days.

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Maternal titer, antibody transfer ratio and gestational age influence birth titer.

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Incidence of seroconversion in infants in southern Vietnam is 4/100 infant years.

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Children should be vaccinated after 5 months of age if a candidate is licensed.

Background

Shigella sonnei is an emergent and major diarrheal pathogen for which there is currently no vaccine. We aimed to quantify duration of maternal antibody against S. sonnei and investigate transplacental IgG transfer in a birth cohort in southern Vietnam.

Methods and results

Over 500-paired maternal/infant plasma samples were evaluated for presence of anti-S. sonnei-O IgG and IgM. Longitudinal plasma samples allowed for the estimation of the median half-life of maternal anti-S. sonnei-O IgG, which was 43 days (95% confidence interval: 41–45 days). Additionally, half of infants lacked a detectable titer by 19 weeks of age. Lower cord titers were associated with greater increases in S. sonnei IgG over the first year of life, and the incidence of S. sonnei seroconversion was estimated to be 4/100 infant years. Maternal IgG titer, the ratio of antibody transfer, the season of birth and gestational age were significantly associated with cord titer.

Conclusions

Maternal anti-S. sonnei-O IgG is efficiently transferred across the placenta and anti-S. sonnei-O maternal IgG declines rapidly after birth and is undetectable after 5 months in the majority of children. Preterm neonates and children born to mothers with low IgG titers have lower cord titers and therefore may be at greater risk of seroconversion in infancy.

Integrative Analysis of the Developing Postnatal Mouse Heart Transcriptome

In mammals, cardiomyocytes rapidly proliferate in the fetus and continue to do so for a few more days after birth. These cardiomyocytes then enter into growth arrest but the detailed molecular mechanisms involved have not been fully elucidated. We have addressed this issue by comparing the transcriptomes of 2-day-old (containing dividing cardiomyocytes) with 13-day-old (containing growth arrested cardiomyocytes) postnatal mouse hearts. We performed comparative microarray analysis on the heart tissues and then conducted Functional annotation, Gene ontology, KEGG pathway and Gene Set enrichment analyses on the differentially expressed genes. The bioinformatics analysis revealed that gene ontology categories associated with the “cell cycle”, “DNA replication”, “chromosome segregation” and “microtubule cytoskeleton” were down-regulated. Inversely, “immune response”, “extracellular matrix”, “cell differentiation” and “cell membrane” were up-regulated. Ingenuity Pathways Analysis (IPA) has revealed that GATA4, MYH7 and IGF1R were the key drivers of the gene interaction networks. In addition, Regulator Effects network analysis suggested that TASP1, TOB1, C1orf61, AIF1, ROCK1, TFF2 and miR503-5p may be acting on the cardiomyocytes in 13-day-old mouse hearts to inhibit cardiomyocyte proliferation and G1/S phase transition. RT-qPCR was used to validate genes which were differentially expressed and genes that play a prominent role in the pathways and interaction networks that we identified. In sum, our integrative analysis has provided more insights into the transcriptional regulation of cardiomyocyte exit from the cell cycle during postnatal heart development. The results also pinpoint potential regulators that could be used to induce growth arrested cardiomyocytes to proliferate in the infarcted heart.

Assessing the energetic costs and trade-offs of a PHA-induced inflammation in the subterranean rodent Ctenomys talarum: immune response in growing tuco-tucos

A traditional approach used to assess whether immune defense is costly is to explore the existence of trade-offs between immunity and other functions; however, quantitative studies of the energetic costs associated with the activation of the immune system are scarce. We assessed the magnitude of a PHA-triggered immune response and the associated energetic costs in 60-day old Ctenomys talarum. We expected that the magnitude of the macroscopic inflammatory response to PHA is lower in young tuco-tucos compared with that of adults, given the allocation of substantial energy to growth, and that the magnitude of the inflammation is lower in male pups compared to females, due to the higher investment in growth of the larger sex. Concomitantly, we expected that the pups challenged with PHA show an increase in oxygen consumption compared to control animals and that a positive association exists between magnitude of the PHA-induced inflammation and oxygen consumption. Contrary to what was expected, young tuco-tucos mounted a higher inflammatory response compared with adults and there were no differences in the magnitude of this response between sexes. The inflammatory response induced by a PHA injection did not represent a significant energetic cost for young tuco-tucos. There were no differences in oxygen consumption between PHA-injected and control animals, and tuco-tucos that mounted a higher inflammatory response to PHA did not show higher oxygen consumption. Energy expenditure, however, is not the only physiological cost involved in trade-offs between immune response and various functions of the organism, and other currencies are discussed.

Macrophages are required for neonatal heart regeneration

Myocardial infarction (MI) leads to cardiomyocyte death, which triggers an immune response that clears debris and restores tissue integrity. In the adult heart, the immune system facilitates scar formation, which repairs the damaged myocardium but compromises cardiac function. In neonatal mice, the heart can regenerate fully without scarring following MI; however, this regenerative capacity is lost by P7. The signals that govern neonatal heart regeneration are unknown. By comparing the immune response to MI in mice at P1 and P14, we identified differences in the magnitude and kinetics of monocyte and macrophage responses to injury. Using a cell-depletion model, we determined that heart regeneration and neoangiogenesis following MI depends on neonatal macrophages. Neonates depleted of macrophages were unable to regenerate myocardia and formed fibrotic scars, resulting in reduced cardiac function and angiogenesis. Immunophenotyping and gene expression profiling of cardiac macrophages from regenerating and nonregenerating hearts indicated that regenerative macrophages have a unique polarization phenotype and secrete numerous soluble factors that may facilitate the formation of new myocardium. Our findings suggest that macrophages provide necessary signals to drive angiogenesis and regeneration of the neonatal mouse heart. Modulating inflammation may provide a key therapeutic strategy to support heart regeneration.

Brain development in rodents and humans: Identifying benchmarks of maturation and vulnerability to injury across species

Hypoxic-ischemic and traumatic brain injuries are leading causes of long-term mortality and disability in infants and children. Although several preclinical models using rodents of different ages have been developed, species differences in the timing of key brain maturation events can render comparisons of vulnerability and regenerative capacities difficult to interpret. Traditional models of developmental brain injury have utilized rodents at postnatal day 7-10 as being roughly equivalent to a term human infant, based historically on the measurement of post-mortem brain weights during the 1970s. Here we will examine fundamental brain development processes that occur in both rodents and humans, to delineate a comparable time course of postnatal brain development across species. We consider the timing of neurogenesis, synaptogenesis, gliogenesis, oligodendrocyte maturation and age-dependent behaviors that coincide with developmentally regulated molecular and biochemical changes. In general, while the time scale is considerably different, the sequence of key events in brain maturation is largely consistent between humans and rodents. Further, there are distinct parallels in regional vulnerability as well as functional consequences in response to brain injuries. With a focus on developmental hypoxic-ischemic encephalopathy and traumatic brain injury, this review offers guidelines for researchers when considering the most appropriate rodent age for the developmental stage or process of interest to approximate human brain development.

Frank A. Beach award: programming of neuroendocrine function by early-life experience: a critical role for the immune system

Many neuropsychiatric disorders are associated with a strong dysregulation of the immune system, and several have a striking etiology in development as well. Our recent evidence using a rodent model of neonatal Escherichia coli infection has revealed novel insight into the mechanisms underlying cognitive deficits in adulthood, and suggests that the early-life immune history of an individual may be critical to understanding the relative risk of developing later-life mental health disorders in humans. A single neonatal infection programs the function of immune cells within the brain, called microglia, for the life of the rodent such that an adult immune challenge results in exaggerated cytokine production within the brain and associated cognitive deficits. I describe the important role of the immune system, notably microglia, during brain development, and discuss some of the many ways in which immune activation during early brain development can affect the later-life outcomes of neural function, immune function, and cognition.

Humanized mice, a new model to study the influence of drug treatment on neonatal sepsis

Bacterial infection with group B Streptococcus (GBS) represents a prominent threat to neonates and fetuses in the Western world, causing severe organ damage and even death. To improve current therapeutic strategies and to investigate new approaches, an appropriate in vivo model to study the immune response of a human immune system is needed. Therefore, we introduced humanized mice as a new model for GBS-induced sepsis. Humanized mice feature deficiencies similar to those found in neonates, such as lower immunoglobulin levels and myeloid cell dysfunction. Due to the husbandry in specific-pathogen-free (SPF) facilities, the human immune cells in these mice also exhibit a naive phenotype which mimics the conditions in fetuses/neonates. Following infection, cytokine release and leukocyte trafficking from the bone marrow to the lymphoid organ (spleen) and into the peritoneum (site of infection) as well as bacterial spreading and clearance were traceable in the humanized mice. Furthermore, we investigated the effects of betamethasone and indomethacin treatment using this novel sepsis model. Although both drugs are commonly used in perinatal care, little is known about their effects on the neonatal immune system. Treatment of infected humanized mice not only induced the reduction of human leukocytes in the spleen but also increased the bacterial load in all analyzed organs, including the brain, which did not show infiltration of live GBS in untreated controls. These studies demonstrate the utility of the humanized mice as a new model to study an immature human immune response during bacterial infection and allow the investigation of side effects induced by various treatments.

Toll-like receptor levels and caffeine responsiveness in rat pups during perinatal period

Infants born prematurely are prone to bronchopulmonary dysplasia which is a devastating form of chronic lung disease that develops in very low birth weight infants. Toll-like receptors (TLRs) are pattern recognition receptors that initiate innate immune responses. We tested TLR2, 4, and 9 levels in the lungs of rat pups given caffeine at the first days of postnatal life. Twenty-four rat pups equally divided into three groups. The study group received caffeine immediately after birth for ten days. The levels of TLR9 were found significantly higher in study group than control groups. We conclude that the beneficial and anti-inflammatory effects of caffeine in the lungs of newborn rats may be due to increased TLR9 levels.

The suckling rat as a model for immunonutrition studies in early life

Diet plays a crucial role in maintaining optimal immune function. Research demonstrates the immunomodulatory properties and mechanisms of particular nutrients; however, these aspects are studied less in early life, when diet may exert an important role in the immune development of the neonate. Besides the limited data from epidemiological and human interventional trials in early life, animal models hold the key to increase the current knowledge about this interaction in this particular period. This paper reports the potential of the suckling rat as a model for immunonutrition studies in early life. In particular, it describes the main changes in the systemic and mucosal immune system development during rat suckling and allows some of these elements to be established as target biomarkers for studying the influence of particular nutrients. Different approaches to evaluate these immune effects, including the manipulation of the maternal diet during gestation and/or lactation or feeding the nutrient directly to the pups, are also described in detail. In summary, this paper provides investigators with useful tools for better designing experimental approaches focused on nutrition in early life for programming and immune development by using the suckling rat as a model.

Preexposure to CpG protects against the delayed effects of neonatal respiratory syncytial virus infection

Severe respiratory viral infection in early life is associated with recurrent wheeze and asthma in later childhood. Neonatal immune responses tend to be skewed toward T helper 2 (Th2) responses, which may contribute to the development of a pathogenic recall response to respiratory infection. Since neonatal Th2 skewing can be modified by stimulation with Toll-like receptor (TLR) ligands, we investigated the effect of exposure to CpG oligodeoxynucleotides (TLR9 ligands) prior to neonatal respiratory syncytial virus (RSV) infection in mice. CpG preexposure was protective against enhanced disease during secondary adult RSV challenge, with a reduction in viral load and an increase in Th1 responses. A similar Th1 switch and reduction in disease were observed if CpG was administered in the interval between neonatal infection and challenge. In neonates, CpG pretreatment led to a transient increase in expression of major histocompatibility complex class II (MHCII) and CD80 on CD11c-positive cells and gamma interferon (IFN-γ) production by NK cells after RSV infection, suggesting that the protective effects may be mediated by antigen-presenting cells (APC) and NK cells. We conclude that the adverse effects of early-life respiratory viral infection on later lung health might be mitigated by conditions that promote TLR activation in the infant lung.

Inhibition of IL-10 production by maternal antibodies against Group B Streptococcus GAPDH confers immunity to offspring by favoring neutrophil recruitment

Group B Streptococcus (GBS) is the leading cause of neonatal pneumonia, septicemia, and meningitis. We have previously shown that in adult mice GBS glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is an extracellular virulence factor that induces production of the immunosuppressive cytokine interleukin-10 (IL-10) by the host early upon bacterial infection. Here, we investigate whether immunity to neonatal GBS infection could be achieved through maternal vaccination against bacterial GAPDH. Female BALB/c mice were immunized with rGAPDH and the progeny was infected with a lethal inoculum of GBS strains. Neonatal mice born from mothers immunized with rGAPDH were protected against infection with GBS strains, including the ST-17 highly virulent clone. A similar protective effect was observed in newborns passively immunized with anti-rGAPDH IgG antibodies, or F(ab')₂ fragments, indicating that protection achieved with rGAPDH vaccination is independent of opsonophagocytic killing of bacteria. Protection against lethal GBS infection through rGAPDH maternal vaccination was due to neutralization of IL-10 production soon after infection. Consequently, IL-10 deficient (IL-10^−/−) mice pups were as resistant to GBS infection as pups born from vaccinated mothers. We observed that protection was correlated with increased neutrophil trafficking to infected organs. Thus, anti-rGAPDH or anti-IL-10R treatment of mice pups before GBS infection resulted in increased neutrophil numbers and lower bacterial load in infected organs, as compared to newborn mice treated with the respective control antibodies. We showed that mothers immunized with rGAPDH produce neutralizing antibodies that are sufficient to decrease IL-10 production and induce neutrophil recruitment into infected tissues in newborn mice. These results uncover a novel mechanism for GBS virulence in a neonatal host that could be neutralized by vaccination or immunotherapy. As GBS GAPDH is a structurally conserved enzyme that is metabolically essential for bacterial growth in media containing glucose as the sole carbon source (i.e., the blood), this protein constitutes a powerful candidate for the development of a human vaccine against this pathogen.

Streptococcus agalactiae (Group B streptococcus, GBS) is the leading infectious cause of morbidity and mortality among neonates. However, there is still no satisfactory explanation of why neonates are so susceptible to GBS infections. Intrapartum antibiotic prophylaxis (IAP) was implemented in many countries but led to the emergence of antibiotic-resistant GBS strains. Therefore, maternal vaccination represents an attractive alternative to IAP. Here, we show that the high susceptibility of newborn mice to GBS infections is associated with their propensity to produce elevated amounts of immunosuppressive cytokine IL-10. We also demonstrate that IL-10 impairs neutrophil recruitment into infected organs thus preventing bacterial clearance. We identified extracellular GAPDH as the GBS factor that induces the high IL-10 production detected early upon neonatal infection. We show that maternal vaccination with recombinant GAPDH confers robust protective immunity against lethal infection with a GBS hyper-virulent strain in mice offspring. This protection can also be obtained either by antibody neutralization of GBS GAPDH or by blocking IL-10 binding to its receptor. As GBS GAPDH is an essential protein for bacterial growth, it is present in all GBS strains and thus constitutes an appropriate target antigen for a global effective vaccine against this pathogen.

IgG placental transfer in healthy and pathological pregnancies

Placental transfer of maternal IgG antibodies to the fetus is an important mechanism that provides protection to the infant while his/her humoral response is inefficient. IgG is the only antibody class that significantly crosses the human placenta. This crossing is mediated by FcRn expressed on syncytiotrophoblast cells. There is evidence that IgG transfer depends on the following: (i) maternal levels of total IgG and specific antibodies, (ii) gestational age, (iii) placental integrity, (iv) IgG subclass, and (v) nature of antigen, being more intense for thymus-dependent ones. These features represent the basis for maternal immunization strategies aimed at protecting newborns against neonatal and infantile infectious diseases. In some situations, such as mothers with primary immunodeficiencies, exogenous IgG acquired by intravenous immunoglobulin therapy crosses the placenta in similar patterns to endogenous immunoglobulins and may also protect the offspring from infections in early life. Inversely, harmful autoantibodies may cross the placenta and cause transitory autoimmune disease in the neonate.

Immunohistochemical investigation of cells expressing CD21, membrane IgM, CD32 and a follicular dendritic cell marker in the lymphoid tissues of neonatal calves

Activation of B lymphocytes in the presence of passive maternal antibodies depends on expression of CD21, membrane IgM and CD32. On colligation with IgM, CD32 inhibits activation whereas CD21 enhances it. Recently, we assessed expression of CD21 and CD32 on IgM(+) cells from lymphoid tissues of newborn calves by flow cytometry, but this approach does not provide information about spatial distribution within lymphoid compartments. Therefore, histologic sections of lymphoid tissues from newborn and 7-month-old calves were examined using an immunoperoxidase technique. In all calves, CD21 and IgM stained cells were collocated in the cortex and paracortex of the retropharyngeal lymph node, in the marginal zone of the spleen and in lymphoid aggregates of palatine tonsils. Most CD32(+) cells were in the mantle zone of lymphoid follicles in 7-month-old calves, whereas only weak staining was observed in newborns. A few CD32(+) cells were also observed in the paracortex at both ages. Absence of CD32(+) cells in the center of follicles suggests that IgM(+)CD32(-) cells observed previously by flow cytometry were from germinal centers. Overall, there were few organized lymphoid aggregates within lymphoid tissues of newborn calves, and follicular dendritic cells were virtually undetectable. Their absence may be an important limitation for neonatal immunization.

Early-life programming of later-life brain and behavior: a critical role for the immune system

The immune system is well characterized for its critical role in host defense. Far beyond this limited role however, there is mounting evidence for the vital role the immune system plays within the brain, in both normal, “homeostatic” processes (e.g., sleep, metabolism, memory), as well as in pathology, when the dysregulation of immune molecules may occur. This recognition is especially critical in the area of brain development. Microglia and astrocytes, the primary immunocompetent cells of the CNS, are involved in every major aspect of brain development and function, including synaptogenesis, apoptosis, and angiogenesis. Cytokines such as tumor necrosis factor (TNF)α, interleukin [IL]-1β, and IL-6 are produced by glia within the CNS, and are implicated in synaptic formation and scaling, long-term potentiation, and neurogenesis. Importantly, cytokines are involved in both injury and repair, and the conditions underlying these distinct outcomes are under intense investigation and debate. Evidence from both animal and human studies implicates the immune system in a number of disorders with known or suspected developmental origins, including schizophrenia, anxiety/depression, and cognitive dysfunction. We review the evidence that infection during the perinatal period of life acts as a vulnerability factor for later-life alterations in cytokine production, and marked changes in cognitive and affective behaviors throughout the remainder of the lifespan. We also discuss the hypothesis that long-term changes in brain glial cell function underlie this vulnerability.

Intra-amniotic LPS modulation of TLR signaling in lung and blood monocytes of fetal sheep

Epidemiological studies suggest that intra-uterine exposure to inflammation may prime postnatal immune responses. In fetal sheep, intra-amniotic injection of lipopolysaccharide (LPS) induced chorioamnionitis, lung inflammation and maturation, matured lung monocytes to macrophages and initiated systemic tolerance of fetal monocytes to subsequent challenge with LPS. We hypothesized that LPS-mediated chorioamnionitis altered the response of lung and blood monocytes to Toll-like receptor (TLR) ligands such as PamCysK4 (TLR2), flagellin (TLR5), and human CpG-DNA (TLR9). Time-mated ewes were given intra-amniotic injections of LPS or saline. Blood and lung monocytes were assessed after 2 days, 7 days and 2 days and 7 days repetitive LPS injections before delivery at 124 days gestational age (term 150 days). Responsiveness of blood and lung monocytes to TLR-ligands in vitro was assessed by interleukin (IL)-6, tumor necrosis factor-alpha (TNF-alpha) and hydrogen peroxide. Monocytes from preterm controls had minimal responses. Lipopolysaccharide-mediated chorioamnionitis increased IL-6, TNF- alpha and hydrogen peroxide to all TLR agonists in blood and lung monocytes. Repetitive exposure to antenatal LPS reduced IL-6, TNF- alpha and hydrogen peroxide to TLR-ligands suggesting tolerance. Tolerance to TLR-ligands reduced IL-1 receptor associated kinase-4 expression. Thus, repeated fetal exposure to LPS induced tolerance to other TLR-ligands. These modulations of fetal innate immunity have implications for host defense and injury responses in preterm infants.

Phenotypic analysis of circulating dendritic cells during the second half of human gestation

Dendritic cells (DCs) have been characterized as having an immature phenotype in infants when compared with adults; but it is unclear whether the phenotype or function of these populations changes during human intrauterine development. Three-colour flow cytometry was used to phenotype fetal/neonatal circulating DCs during the second half (>20-wk gestation) of pregnancy, (n = 34) and adults (n = 9). DCs were identified from peripheral blood mononuclear cells (PBMCs) or cord blood mononuclear cells (CBMCs) as staining brightly for HLA-DR but negative for T cell, B cell, monocyte, and NK cell lineage markers. The surface molecule of interest was detected in a third colour. During gestation CD34, a marker of immaturity was significantly higher, and CD4, a differentiation marker, was significantly lower than adult levels. The percentage of CD11c+ cells did not differ significantly at any age, although a trend to reduced intensity of expression at earlier stages of gestation was observed. Significantly fewer DCs expressed the IgG receptors CD32 and CD64 at all gestations. The percentage of HLA-DR+/lin- cells expressing CD40 was lowest at 20-23 wks and was always significantly lower on DCs from cord blood vs. adult blood. Similarly, the percentage of CD86+ and CD54+ DCs was significantly lower than adults throughout gestation. Thus, immaturity of cord blood DCs is likely to arise as a consequence of decreased ability to take up antigen (at least via IgG-mediated mechanisms) and reduced provision of co-stimulation.

Activated human neonatal CD8+ T cells are subject to immunomodulation by direct TLR2 or TLR5 stimulation

In conditions of optimal priming, the neonate possesses competency to mount quantitatively adult-like responses. Vaccine formulations containing sufficiently potent adjuvants may overcome the neonate's natural tendency for immunosuppression and provoke a similarly robust immune response. TLR expression on T cells represents the possibility of directly enhancing T cell immunity. We examined the ex vivo responsiveness of highly purified human cord blood-derived CD8(+) T cells to direct TLR ligation by a repertoire of TLR agonists. In concert with TCR stimulation, only Pam(3)Cys (palmitoyl-3-Cys-Ser-(Lys)(4)) and flagellin monomers significantly enhanced proliferation, CD25(+) expression, IL-2, IFN-gamma, TNF-alpha, and intracellular granzyme B expression. TLR2 and TLR5 mRNA was detected in the CD8(+) T cells. Blocking studies confirmed that the increase in IFN-gamma production was by the direct triggering of surface TLR2 or TLR5. The simultaneous exposure of CD8(+) T cells to both TLR agonists had an additive effect on IFN-gamma production. These data suggest that a combination of the two TLR ligands would be a potent T cell adjuvant. This may represent a new approach to TLR agonist-based adjuvant design for future human neonatal vaccination strategies requiring a CD8(+) component.

Evidence of changes in the immunophenotype and metabolic characteristics (intracellular reactive oxygen radicals) of fetal, but not maternal, monocytes and granulocytes in the fetal inflammatory response syndrome

OBJECTIVE

The fetal inflammatory response syndrome (FIRS) is present in a fraction of fetuses exposed to intra-amniotic infection and is associated with the impending onset of labor and multisystem organ involvement. Neonates born with funisitis, the histologic counterpart of fetal systemic inflammation, are at increased risk for cerebral palsy and bronchopulmonary dysplasia. The aim of this study was to determine whether fetal and maternal granulocytes and monocytes have the phenotypic and metabolic characteristics of activation in cases with FIRS.

STUDY DESIGN

A case-control study was conducted with umbilical cord and maternal blood samples obtained from patients who delivered preterm with (n=30) and without funisitis (n=15). The phenotypic characteristics of granulocytes and monocytes were examined using flow cytometry and monoclonal antibodies including CD11b, CD14, CD15, CD16, CD18, CD49d, CD62L, CD64, CD66b, and HLA-DR. Intracellular reactive oxygen species (iROS) were measured at the basal state and after stimulation (oxidative burst). A P<0.01 was considered statistically significant.

RESULTS

(1) Funisitis was associated with a significant increase in the median mean channel brightness (MCB) of CD14, CD64, and CD66b on granulocytes and the MCB of CD64 on monocytes collected from umbilical cord blood. (2) The basal iROS production and oxidative burst were higher in the umbilical cord monocytes of neonates with funisitis than in those without funisitis. (3) There were no differences in the immunophenotype, basal iROS production, and oxidative burst in maternal granulocytes or monocytes between the study groups.

CONCLUSION

Fetal systemic inflammation is associated with phenotypic and metabolic changes consistent with activation in fetal immune cells but not in maternal blood.

Bottlenose dolphin (Tursiops truncatus) papillomaviruses: vaccine antigen candidates and screening test development

Papillomaviruses (PVs) have been shown as being the etiologic agents of various benign and malignant tumours in many vertebrate species. In dolphins and porpoises, a high prevalence of orogenital tumours has recently been documented with at least four distinct novel species-specific PV types detected in such lesions. Therefore, we generated the immunological reagents to establish a serological screening test to determine the prevalence of PV infection in Atlantic bottlenose dolphins [(Tursiops truncatus (Tt)]. Using the baculovirus expression system, virus-like particles (VLPs) derived from the L1 proteins of two TtPV types, TtPV1 and TtPV2, were generated. Polyclonal antibodies against TtPV VLPs were produced in rabbits and their specificity for the VLPs was confirmed. Electron microscopy and enzyme-linked immunosorbent assay (ELISA) studies revealed that the generated VLPs self-assembled into particles presenting conformational immunodominant epitopes. As such, these particles are potential antigen candidates for a TtPV vaccine. Subsequently, the VLPs served as antigens in initial ELISA tests using sera from six bottlenose dolphins to investigate PV antibody presence. Three of these sera were derived from dolphins with genital tumour history and showed positive PV ELISA reactivity, while the remaining sera from lesion-free dolphins were PV antibody-negative. The results suggest that the developed screening test may serve as a potential tool for determining PV prevalence and thus for observing transmission rates in dolphin populations as the significance of PV infection in cetaceans starts to unfold.

Infection of mice with respiratory syncytial virus during neonatal life primes for enhanced antibody and T cell responses on secondary challenge

Primary neonatal immune responses to infection or vaccines are weak when compared with those of adults. In addition, memory responses of neonatally primed animals may be absent, weak or T helper type 2 (Th2)-biased. Respiratory syncytial virus (RSV) is an important pathogen of human infants and infection during the neonatal period has been linked to the development of asthma in later life. Here we report that acute intranasal infection of neonatal mice with RSV induces significant RSV-specific antibody and CD8 T cell responses. These responses were boosted after RSV rechallenge during adulthood, demonstrating the establishment of memory after neonatal priming. Primary infection during neonatal life was associated, following rechallenge, with limited viral replication in the lung. Recall responses of both spleen and lymph node cells from neonatally primed and adult-primed mice were associated with interferon-gamma secretion, indicative of a Th1-type response. However, interleukin (IL)-4 and IL-5 secretion were enhanced only in spleen and lymph node cells from neonatally primed mice. Rechallenge of neonatally primed mice was also associated with increased concentrations of chemokines monocyte chemoattractant protein-1, macrophage inflammatory protein-1alpha and regulated upon activation normal T cell expressed and secreted in the lung. These may play a role in the enhanced inflammatory cell recruitment and immunopathology induced following RSV reinfection. Our results demonstrate therefore that immunity to RSV can be established during neonatal life and, importantly, that the quality of the subsequent response is dependent upon the age of first infection.

Toll-like receptors and agonist responses in the developing fetal sheep lung

Toll-like receptors (TLRs) are pattern recognition molecules that initiate innate immune responses. Intra-amniotic exposure of fetal sheep to pro-inflammatory stimuli causes pulmonary inflammation and induced lung maturation. We examined TLR ontogeny and fetal lung responsiveness to three different TLR agonists. We cloned ovine TLRs 2, 3, and 4 and found 83-88% homology between these ovine and human TLRs. Lung TLR2 and 4 mRNAs increased throughout late gestation to 50% of adult level in the term newborn lamb. Doses of 10 mg of PAMCysK4 (TLR2 agonist), poly I:C dsRNA (TLR3 agonist), or E. coli O55:B5 lipopoysaccharide (LPS) (TLR4 agonist) were given by intra-amniotic injection 2 d or 7 d before operative delivery of preterm lambs at 123 d (n = 4-7/group). The TLR4 agonist induced lung inflammation and maturation, whereas the TLR2 agonist gave less consistent responses. Intra-amniotic LPS increased TLR2 mRNA expression primarily in the inflammatory cells and TLR4 mRNA diffusely in multiple cell types. The TLR3 agonist had no effects, and TLR3 mRNA in the fetal lung did not change after LPS exposure. We conclude that TLR2 and TLR4 mRNAs increase through gestation and expression of TLR2 and TLR4 are induced by LPS in the fetal sheep lung.

Functional development of immune response in rabbits

The aim of our study was to extend knowledge concerning postnatal development of the immune system in rabbits from two aspects. Firstly, capability of lymphocytes from peripheral blood, spleen, mesenteric, and popliteal lymph nodes to respond to Concanavalin A stimulation was investigated. Secondly, changes in the ability to produce antibodies against tetanus toxoid by rabbits during maturation were studied. Proliferation of lymphocytes was reduced in mesenteric lymph nodes in newborns, in PB up to the age of two weeks, and in popliteal lymph nodes up to the age of four weeks when compared to adults. High spontaneous lymphocyte proliferation that lasted up to the age of two weeks was recorded in spleen. The study of antibody response showed that even one-day-old rabbits were able to form specific antibodies of isotype IgM and IgG. Nevertheless, significantly lower formation of both isotypes was noted in one-day and two-week-old rabbits, and commencement of IgG isotype formation was delayed in one-day, two-week, and four-week-old rabbits when compared to adults.

Modeling Immunocompetence Development and Immunoresponsiveness to Challenge in Chicks

The purpose of this study was 2-fold: 1) to develop a deterministic model that describes the development of immunocompetence and the kinetics of immunoresponsiveness to a pathogenic challenge in chicks and 2) to use this model to illustrate the importance of factors in experimental design, such as type of variable measured, measurement timing, and challenge age. Difficulties in evaluating immunological variables hinder attempts to improve animal health through selection on immunological variables. In young chicks, evaluating immunological variables is additionally complicated by immune system development and maternal immunity. The evaluation of immunocompetence and immunoresponsiveness and the definition of appropriate challenge and measurement strategies may be enabled through a mathematical model that captures the key components of the immune system and its development. Therefore, a model was developed that describes the development of immunocompetence as well as the kinetics of immunoresponsiveness to a pathogenic extracellular bacterial challenge in an individual chick from 0 to 56 d of age. The model consisted of 4 components describing immunocompetence (maternal and baseline immunity) and immunoresponsiveness (acute phase and antibody response). Individual component equations generally fit published data adequately. Four scenarios that represented combinations of challenge age and measurement timing were simulated. In each scenario, the immunoresponsiveness to a particular challenge was compared for 3 different levels of baseline immunity, representing 3 broiler genotypes. It was illustrated that experimental design (type of immunoresponsiveness measured, measurement timing, and challenge age) can have an important effect on the ranking of genotypes, groups, or individuals and on the reliability of extrapolations based on this ranking. It is concluded that this model is a potentially useful tool in the definition of appropriate challenge and measurement strategies when evaluating immunocompetence and immunoresponsiveness. Further, it may be used as a generator of hypotheses on global immunological relationships to be tested experimentally.

Endotoxin-induced maturation of monocytes in preterm fetal sheep lung

The fetal lung normally contains immature monocytes and very few mature macrophages. The chorioamnionitis frequently associated with preterm birth induces monocyte influx into the fetal lung. Previous studies demonstrated that monocytes in the developing lung can mediate lung injury responses that resemble BPD in humans. We hypothesized that chorioamnionitis would induce maturation of immature monocytes in the fetal lung. Groups of three to seven time-mated ewes received saline or 10 mg of endotoxin (Escherichia coli 055:B5) in saline by intra-amniotic injection for intervals from 1 to 14 days before operative delivery at 124 days of gestational age. Monocytic cells from lung tissue were recovered using Percoll gradients. Monocytic cells consistent with macrophages were identified morphologically and by myosin heavy chain class II expression. An increase in macrophages was preceded by induction of granulocyte-macrophage colony-stimulating factor in the lung and subsequent activation of the transcription factor PU.1. The production of IL-6 by monocytes/macrophages in response to endotoxin challenge in vitro increased 7 and 14 days after exposure to intra-amniotic endotoxin. Recombinant TNF-alpha induced IL-6 production by lung monocytic cells exposed to intra-amniotic endotoxin but not in control cells. Monocytic phagocytosis of apoptotic neutrophils also increased 7 and 14 days after exposure to intra-amniotic endotoxin. Intra-amniotic endotoxin induced lung monocytes to develop into functionally mature cells consistent with macrophages. These findings have implications for lung immune responses after exposure to chorioamnionitis.

Vitamin A supplementation and retinoic acid treatment in the regulation of antibody responses in vivo

Vitamin A (VA, retinol) is essential for normal immune system maturation, but the effect of VA(1) on antibody production, the hallmark of successful vaccination, is still not well understood. In countries where VA deficiency is a public health problem, many children worldwide are now receiving VA along with immunizations against poliovirus, measles, diphtheria, pertussis, and tetanus. The primary goal has been to provide enough VA to protect against the development of VA deficiency for a period of 4-6 months. However, it is also possible that VA might promote the vaccine antibody response. Several community studies, generally of small size, have been conducted in children supplemented with VA at the time of immunization, as promoted by the World Health Organization/UNICEF. However, only a few studies have reported differences in antibody titers or seroconversion rates due to VA. However, VA status was not directly assessed, and in some communities children were often breast fed, another strategy for preventing VA deficiency. Some of the vaccines used induced a high rate of seroconversion, even without VA. In children likely to have been VA deficient, oral polio vaccine seroconversion rate was increased by VA. In animal models, where VA status was controlled and VA deficiency confirmed, the antibody response to T-cell-dependent (TD) and polysaccharide antigens was significantly reduced, congruent with other defects in innate and adaptive immunity. Moreover, the active metabolite of VA, retinoic acid (RA) can potentiate antibody production to TD antigens in normal adult and neonatal animals. We speculate that numerous animal studies have correctly identified VA deficiency as a risk factor for low antibody production. A lack of effect of VA in human studies could be due to a low rate of VA deficiency in the populations studied or low sample numbers. The ability to detect differences in antibody response may also depend on the vaccine-adjuvant combination used. Future studies of VA supplementation and immunization should include assessment of VA status and a sufficiently large sample size. It would also be worthwhile to test the effect of neonatal VA supplementation on the response to immunization given after 6 months to 1 year of age, as VA supplementation, by preventing the onset of VA deficiency, may improve the response to immunizations given later on.

DNA vaccines for poultry: the jump from theory to practice

DNA vaccines could offer a solution to a number of problems faced by the poultry industry; they are relatively easy to manufacture, stable, potentially easy to administer, can overcome neonatal tolerance and the deleterious effects of maternal antibody, and do not cause disease pathology. Combined with this, in ovo vaccination offers the advantage of reduced labor costs, mass administration and the induction of an earlier immune response. Together, this list of advantages is impressive. However, this combined technology is still in its infancy and requires many improvements. The potential of CpG motifs, DNA vaccines and in ovo vaccination, however, can be observed by the increasing number of recent reports investigating their application in challenge experiments. CpG motifs have been demonstrated to be stimulatory both in vitro and in vivo. In addition, DNA vaccines have been successfully delivered via the in ovo route, albeit not yet through the amniotic fluid. Lastly, a recent report has demonstrated that a DNA vaccine against infectious bronchitis virus administered via in ovo vaccination, followed by live virus boost, can slightly improve on the protective effect induced by the live virus alone. Therefore, DNA vaccination via the in ovo route is promising and offers potential as a poultry vaccine, however, efficacy needs to be improved and the costs of production reduced before it is likely to be beneficial to the poultry industry in the long term.

Placental Plasmodium falciparum infection: causes and consequences of in utero sensitization to parasite antigens

Available evidence suggests that, in African populations, systemic blood-dwelling parasitoses of mothers are associated with enhanced susceptibility to infection of their offspring. Thus, children born to mothers with filariasis or schistosomiasis are infected earlier, and offspring of mothers with placental Plasmodium falciparum at delivery, commonly referred to as pregnancy-associated malaria or PAM, are themselves at higher risk of developing parasitaemia during infancy. Since foetal/neonatal antigen-presenting cells (APC) are either immature or provide insufficient costimulatory signals to T cells, thus favouring tolerance induction, it is commonly assumed that soluble parasite components [protein antigens], transferred transplacentally and inducing foetal immune tolerance, are largely, if not exclusively, responsible for these outcomes. Plasmodial asexual blood stage antigen-specific T cells are detectable in as many as two-thirds of all cord blood samples in malaria-endemic countries of sub-Saharan Africa, indicating that in utero sensitization may be a common phenomenon during pregnancy in these populations. Parasite antigen-specific T cell responses of neonates born to helminth-infected mothers display a highly skewed Th2-type cytokine pattern, with a prominent role for the regulatory cytokine interleukin (IL)-10. Similarly, the cord blood immune response of those born to mothers identified with on-going PAM is characterised by inducible parasite antigen-specific IL-10-producing regulatory T cells that can inhibit both APC HLA expression and Th1-type T cell responses. In contrast, plasmodial antigen-specific Th1-type responses, characterised by IFN-gamma production, predominate in cord blood of those born to mothers successfully treated for Pf malaria during gestation, suggesting that the duration and/or the nature of antigen exposure in utero governs the outcome with respect to neonatal immune responses. Aspects of APC function in the context of these differentially modulated responses, whether and how the latter translate into altered susceptibility to Pf infection during infancy, as well as the possible implications for vaccination in early life, are aspects that are discussed in this review.