The generation of Th memory in neonates versus adults: prolonged primary Th2 effector function and impaired development of Th1 memory effector function in murine neonates

Site-specific development and progressive maturation of human tissue-resident memory T cells over infancy and childhood

Infancy and childhood are critical life stages for generating immune memory to protect against pathogens; however, the timing, location, and pathways for memory development in humans remain elusive. Here, we investigated T cells in mucosal sites, lymphoid tissues, and blood from 96 pediatric donors aged 0-10 years using phenotypic, functional, and transcriptomic profiling. Our results revealed that memory T cells preferentially localized in the intestines and lungs during infancy and accumulated more rapidly in mucosal sites compared with blood and lymphoid organs, consistent with site-specific antigen exposure. Early life mucosal memory T cells exhibit distinct functional capacities and stem-like transcriptional profiles. In later childhood, they progressively adopt proinflammatory functions and tissue-resident signatures, coincident with increased T cell receptor (TCR) clonal expansion in mucosal and lymphoid sites. Together, our findings identify staged development of memory T cells targeted to tissues during the formative years, informing how we might promote and monitor immunity in children.

Shaping Neonatal Immunization by Tuning the Delivery of Synergistic Adjuvants via Nanocarriers

Adjuvanted nanocarrier-based vaccines hold substantial potential for applications in novel early-life immunization strategies. Here, via mouse and human age-specific in vitro modeling, we identified the combination of a small-molecule STING agonist (2'3'-cyclic GMP-AMP, cGAMP) and a TLR7/8 agonist (CL075) to drive the synergistic activation of neonatal dendritic cells and precision CD4 T-helper (Th) cell expansion via the IL-12/IFNγ axis. We further demonstrate that the vaccination of neonatal mice with quadrivalent influenza recombinant hemagglutinin (rHA) and an admixture of two polymersome (PS) nanocarriers separately encapsulating cGAMP (cGAMP-PS) and CL075 (CL075-PS) drove robust Th1 bias, high frequency of T follicular helper (T_FH) cells, and germinal center (GC) B cells along with the IgG2c-skewed humoral response in vivo. Dual-loaded cGAMP/CL075-PSs did not outperform admixed cGAMP-PS and CL075-PS in vivo. These data validate an optimally designed adjuvantation system via age-selected small-molecule synergy and a multicomponent nanocarrier formulation as an effective approach to induce type 1 immune responses in early life.

Neonatal Immune Responses to Respiratory Viruses

Respiratory tract infections are a leading cause of morbidity and mortality in newborns, infants, and young children. These early life infections present a formidable immunologic challenge with a number of possibly conflicting goals: simultaneously eliminate the acute pathogen, preserve the primary gas-exchange function of the lung parenchyma in a developing lung, and limit long-term sequelae of both the infection and the inflammatory response. The latter has been most well studied in the context of childhood asthma, where multiple epidemiologic studies have linked early life viral infection with subsequent bronchospasm. This review will focus on the clinical relevance of respiratory syncytial virus (RSV), human metapneumovirus (HMPV), and rhinovirus (RV) and examine the protective and pathogenic host responses within the neonate.

Infant T cells are developmentally adapted for robust lung immune responses through enhanced T cell receptor signaling

Infants require coordinated immune responses to prevent succumbing to multiple infectious challenges during early life, particularly in the respiratory tract. The mechanisms by which infant T cells are functionally adapted for these responses are not well understood. Here, we demonstrated using an in vivo mouse cotransfer model that infant T cells generated greater numbers of lung-homing effector cells in response to influenza infection compared with adult T cells in the same host, due to augmented T cell receptor (TCR)–mediated signaling. Mouse infant T cells showed increased sensitivity to low antigen doses, originating at the interface between T cells and antigen-bearing accessory cells—through actin-mediated mobilization of signaling molecules to the immune synapse. This enhanced signaling was also observed in human infant versus adult T cells. Our findings provide a mechanism for how infants control pathogen load and dissemination, which is important for designing developmentally targeted strategies for promoting immune responses at this vulnerable life stage.

Buttermilk: an important source of lipid soluble forms of choline that influences the immune system development in Sprague-Dawley rat offspring

PURPOSE

To determine the effect of feeding buttermilk-derived choline metabolites on the immune system development in Sprague-Dawley rat pups.

METHODS

Sprague-Dawley dams were randomized to one of the three diets containing 1.7 g/kg choline: 1-Control (100% free choline (FC)), 2-Buttermilk (BM, 37% phosphatidylcholine (PC), 34% sphingomyelin (SM), 17% glycerophosphocholine (GPC), 7% FC, 5% phosphocholine), and 3-Placebo (PB, 50% PC, 25% FC, 25% GPC) until the end of the lactation period. At weaning, pups continued on the same diet as their mom. Cell phenotypes and cytokine production by mitogen-stimulated splenocytes isolated from 3- and 10-week-old pups were measured.

RESULTS

At 3 weeks, BM-pups had a higher proportion of cytotoxic T cells (CTL; CD3 + CD8 +) while both BM- and PB-pups had an increased proportion of cells expressing CD28 + , CD86 + and CD27 + (all p > 0.05). Following ConA stimulation, splenocytes from BM- and PB-pups produced more TNF-α and IFN-γ and after LPS stimulation produced more IL-10 and TNF-α (all p > 0.05). Starting at week 6 of age, BM-pups had a higher body weight. At 10 weeks, both the BM- and PB-pups had a higher proportion of CTL expressing CD27 + . After ConA stimulation, splenocytes from BM- and PB-pups produced more IL-2, IFN-γ and IL-6 and more IL-10 after LPS stimulation (all p > 0.05).

CONCLUSION

The proportion of lipid soluble forms of choline in the diet during lactation and weaning periods influence the immune system development in rat offspring.

Mucosal and systemic immune responses to Aujeszky's disease virus (ADV) in early vaccinated piglets

Newborn humans and animals are highly susceptible to viral infections. The Aujeszky´s disease virus (ADV) is a porcine herpes virus 1 which infects the respiratory tract and is lethal during the first weeks of life. Current intramuscular vaccines, applied at weaning, induce poor mucosal immunity and frequently fail to prevent and control the disease. Additionally, early vaccination has not been studied thoroughly. Therefore, we studied a systemic/mucosal route of immunization using an inactivated ADV vaccine in two-and fourteen-day-old groups of unweaned SPF miniature Vietnamese pigs, measuring the anti ADV antibody (ELISA) and cytokine (qPCR) responses in systemic and mucosal samples. The results showed that the serum ADV-specific IgG response was higher in the 14-day groups. However, the nasal IgA responses were similar in immunized groups, although the response in saliva was higher in the 2-day old group. Moreover, in vitro ADV stimulated peripheral blood mononuclear cells and lung cells from immunized pigs showed higher IFN-γ mRNA production in the 14-day old group than in younger animals and similar levels of IL-4 and IL-10 transcripts. Our data suggest that early mucosal immunization induce humoral and cellular systemic and mucosal immune responses against ADV in young pigs and younger animals may have compensatory mechanisms to overcome early immaturity and maternal-driven immune interference. Therefore, early protection in susceptible animals could be induced using this immunization protocol, opening the possibility for its application against other viral pathogens of pigs and for traslational studies in humans.

The Sources of Essential Fatty Acids for Allergic and Cancer Patients; a Connection with Insight into Mammalian Target of Rapamycin: A Narrative Review

Background:

Disturbance in essential fatty acids (EFA) metabolism plays a key role in autoimmune diseases, but EFA supplementation with sources of borage, evening primrose, hemp seed and fish oils was not effective in atopic and cancer diseases, as that seen in the case of multiple sclerosis. It seems that two complexes of the mammalian target of rapamycin (mTOR) signaling, mTORC1 and mTORC2, are congruent with the two bases of the Traditional Iranian Medicine (TIM) therapy, Cold and Hot nature, which are essential for the efficacy of functional oils for controlling immune responses in autoimmune diseases.

Methods:

We searched PubMed database, Web of Science (WOS), Google Scholar, Scopus and selected studies by predefined eligibility criteria. We then assessed their quality and extracted data.

Results:

The oils controlled by Cold or Hot nature may be helpful in maintaining homeostasis and preventing autoimmune diseases. In summary, studies of randomized controlled trials for allergy and cancer patients found no improvement in the signs or response to tests, despite a remarkable change in EFA fractions in the blood by supplementation with sources of borage, evening primrose, hemp seed and fish oils. In contrast, portulaca oleracea oil exhibited protective effects by anti-inflammatory properties via the PI3K/Akt/mTORC2 pathway with a deviation immune response to Th1 to treat atopic diseases and cancer.

Conclusions:

According to the concept of Traditional Iranian Medicine therapy, in contrast to Cold-nature oils, EFA supplementation with the sources of Hot-nature oilsis not suitable for the treatment of atopic and cancerous diseases.

Neonatal Immunity, Respiratory Virus Infections, and the Development of Asthma

Infants are exposed to a wide range of potential pathogens in the first months of life. Although maternal antibodies acquired transplacentally protect full-term neonates from many systemic pathogens, infections at mucosal surfaces still occur with great frequency, causing significant morbidity and mortality. At least part of this elevated risk is attributable to the neonatal immune system that tends to favor T regulatory and Th2 type responses when microbes are first encountered. Early-life infection with respiratory viruses is of particular interest because such exposures can disrupt normal lung development and increase the risk of chronic respiratory conditions, such as asthma. The immunologic mechanisms that underlie neonatal host-virus interactions that contribute to the subsequent development of asthma have not yet been fully defined. The goals of this review are (1) to outline the differences between the neonatal and adult immune systems and (2) to present murine and human data that support the hypothesis that early-life interactions between the immune system and respiratory viruses can create a lung environment conducive to the development of asthma.

HIV-Infected Children Have Elevated Levels of PD-1+ Memory CD4 T Cells With Low Proliferative Capacity and High Inflammatory Cytokine Effector Functions

Background

During human immunodeficiency virus (HIV) disease, chronic immune activation leads to T-cell exhaustion. PD-1 identifies "exhausted" CD8 T cells with impaired HIV-specific effector functions, but its role on CD4 T cells and in HIV-infected children is poorly understood.

Methods

In a Kenyan cohort of vertically HIV-infected children, we measured PD-1+ CD4 T-cell frequencies and phenotype by flow cytometry and their correlation with HIV disease progression and immune activation. Second, in vitro CD4 T-cell proliferative and cytokine responses to HIV-specific and -nonspecific stimuli were assessed with and without PD-1 blockade.

Results

HIV-infected children have increased frequencies of PD-1+ memory CD4 T cells that fail to normalize with antiretroviral treatment. These cells are comprised of central and effector memory subsets and correlate with HIV disease progression, measured by viral load, CD4 percentage, CD4:CD8 T-cell ratio, and immune activation. Last, PD-1+ CD4 T cells predict impaired proliferative potential yet preferentially secrete the Th1 and Th17 cytokines interferon-γ and interleukin 17A, and are unresponsive to in vitro PD-1 blockade.

Conclusions

This study highlights differences in PD-1+ CD4 T-cell memory phenotype and response to blockade between HIV-infected children and adults, with implications for potential immune checkpoint therapies.

Feeding a Mixture of Choline Forms to Lactating Dams Improves the Development of the Immune System in Sprague-Dawley Rat Offspring

Dietary choline is essential during lactation, but few studies have examined the implications of feeding a mixture of choline forms on immune function. This study investigates the impact of feeding lactating dams different mixtures of choline forms, similar to those in human diets, on the development and later immune function of suckled offspring. Sprague-Dawley lactating dams (n = 6/diet) were randomized to consume one of three diets, containing 1 g/kg choline: Control (100% free choline (FC)), Mixed Choline (MC: 50% phosphatidylcholine (PC), 25% FC, 25% glycerophosphocholine (GPC)), or High GPC (HGPC: 75% GPC, 12.5% PC, 12.5% FC). At weaning, female pups (n = 2/dam) were fed the Control diet until 10 weeks. At 3 weeks, MC and HGPC pups were heavier and their splenocytes had a higher proportion of helper T cells expressing CD25 and CD28 and produced less interferon gamma (IFN-γ) and tumor-necrosis factor-α (TNF-α) after Concanavalin A stimulation vs. Control pups (p < 0.05). At 10 weeks, MC and HGPC offspring had a lower proportion of macrophages and dendritic cells and produced less interleukin (IL)-1β but more IL-10 after lipopolysaccharide stimulation vs. Control pups (p < 0.05). In summary, feeding mixed choline diets during lactation improved T cell phenotype/function at the end of suckling and programmed a less inflammatory response later in life.

Natural killer T cell sensitization during neonatal respiratory syncytial virus infection induces eosinophilic lung disease in re-infected adult mice

Respiratory syncytial virus (RSV) is a major viral pathogen that causes severe lower respiratory tract infections in infants and the elderly worldwide. Infants with severe RSV bronchiolitis tend to experience more wheezing and asthma in later childhood. Because invariant natural killer T (iNKT) cells are associated with the asthma pathology, we investigated whether neonatal iNKT cells are involved in the aggravation of pulmonary diseases following RSV infection in mice. Intranasal exposure to the iNKT cell ligand α-galactosylceramide (α-GC) with RSV primary infection in neonatal mice elicited neither cytokine production (except for a slight increase of IL-5) nor pulmonary eosinophilia, despite the presence of both CD1d⁺ cells and NKT cells. Interestingly, in adult mice re-infected with RSV, neonatal iNKT cell sensitization by α-GC during RSV primary infection resulted in much higher levels of pulmonary Th2 cytokines and elevated eosinophilia with airway hyperresponsiveness, whereas this was not observed in cd1d knockout mice. In contrast, α-GC priming of adults during RSV re-infection did not induce more severe airway symptoms than RSV re-infection in the absence of α-GC. α-GC co-administration during RSV primary infection facilitated RSV clearance regardless of age, but viral clearance following re-infection was not iNKT cell-dependent. This study clearly demonstrates that RSV-induced immune responses can be altered by iNKT cells, suggesting that neonatal iNKT cell sensitization during RSV primary infection is associated with exacerbation of pulmonary diseases following RSV re-infection in adulthood.

Neonatal Group B Streptococcal Disease in Otherwise Healthy Infants: Failure of Specific Neonatal Immune Responses

Only a small proportion of newborn infants exposed to a pathogenic microorganism develop overt infection. Susceptibility to infection in preterm infants and infants with known comorbidities has a likely multifactorial origin and can be often attributed to the concurrence of iatrogenic factors, environmental determinants, underlying pathogenic processes, and probably genetic predisposition. Conversely, infection occurring in otherwise healthy full-term newborn infants is unexplained in most cases. Microbial virulence factors and the unique characteristics of the neonatal immune system only partially account for the interindividual variability in the neonatal immune responses to pathogens. We here suggest that neonatal infection occurring in otherwise healthy infants is caused by a failure of the specific protective immunity to the microorganism. To explain infection in term and preterm infants, we propose an extension of the previously proposed model of the genetic architecture of infectious diseases in humans. We then focus on group B streptococcus (GBS) disease, the best characterized neonatal infection, and outline the potential molecular mechanisms underlying the selective failure of the immune responses against GBS. In light of the recent discoveries of pathogen-specific primary immunodeficiencies and of the role of anticytokine autoantibodies in increasing susceptibility to specific infections, we hypothesize that GBS disease occurring in otherwise healthy infants could reflect an immunodeficiency caused either by rare genetic defects in the infant or by transmitted maternal neutralizing antibodies. These hypotheses are consistent with available epidemiological data, with clinical and epidemiological observations, and with the state of the art of neonatal physiology and disease. Studies should now be designed to comprehensively search for genetic or immunological factors involved in susceptibility to severe neonatal infections.

A Dietary Supply of Docosahexaenoic Acid Early in Life Is Essential for Immune Development and the Establishment of Oral Tolerance in Female Rat Offspring

BACKGROUND

The early postnatal period is critical for immunity, and feeding docosahexaenoic acid (DHA) has been demonstrated to affect immune development.

OBJECTIVE

The objective of this study was to determine the importance of feeding DHA during suckling and/or weaning on immune function and oral tolerance (OT).

METHODS

Sprague-Dawley rats were randomly assigned to 1 of 2 nutritionally adequate diets throughout lactation (21 d): a control (n = 12, 0% DHA) diet or a DHA (n = 8, 0.9% DHA) diet. At 11 d, suckled pups from each dam were randomly assigned to a mucosal OT challenge: placebo or ovalbumin. At week 5, all pups systemically received ovalbumin + adjuvant to induce systemic immunization. At 21 d, pups from each dam were randomly assigned to 1 of the 2 diets for 21 d in a factorial design after which immune function and OT were assessed.

RESULTS

Feeding dams DHA during lactation resulted in a 40-60% higher splenocyte production of interleukin (IL)-10 when stimulated with concanavalin A, lipopolysaccharide (LPS), or ovalbumin and a 100% higher production of interferon (IFN)-γ with LPS (P < 0.05) than feeding the control diet to the pups. In comparison with pups fed the control diet, feeding DHA at weaning resulted in a 25% lower type 1 T helper (IL-1β) and type 2 T helper (IL-6) response by splenocytes after LPS stimulation and a 33% lower plasma concentration of ovalbumin-specific immunoglobulin (Ig) G (P < 0.05). Pups that did not receive additional DHA during the study had a 70% higher plasma concentration of ovalbumin-specific IgE than did the pups that received DHA at suckling and/or weaning (P < 0.05).

CONCLUSIONS

Feeding additional DHA during suckling had a beneficial programming effect on the ability of immune cells to produce IFN-γ and IL-10, and feeding DHA during weaning resulted in a lower inflammatory response. Providing no dietary DHA in either of the critical periods of immune development prevented the establishment of OT in female rat offspring.

Age-Specific Adjuvant Synergy: Dual TLR7/8 and Mincle Activation of Human Newborn Dendritic Cells Enables Th1 Polarization

Due to functionally distinct cell-mediated immunity, newborns and infants are highly susceptible to infection with intracellular pathogens. Indeed, neonatal Ag-presenting dendritic cells (DCs) demonstrate impaired Th1 responses to many candidate adjuvants, including most TLR agonists (TLRAs). Combination adjuvantation systems may provide enhanced immune activation but have typically been developed without regard to the age of the target population. We posited that distinct combinations of TLRAs and C-type lectin receptor agonists may enhance Th1 responses of newborn DCs. TLRA/C-type lectin receptor agonist combinations were screened for enhancement of TNF production by human newborn and adult monocyte-derived DCs cultured in 10% autologous plasma or in newborn cord, infant, adult, and elderly whole blood. Monocyte-derived DC activation was characterized by targeted gene expression analysis, caspase-1 and NF-κB studies, cytokine multiplex and naive autologous CD4⁺ T cell activation. Dual activation of newborn DCs via the C-type lectin receptor, macrophage-inducible C-type lectin (trehalose-6,6-dibehenate), and TLR7/8 (R848) greatly enhanced caspase-1 and NF-κB activation, Th1 polarizing cytokine production and autologous Th1 polarization. Combined activation via TLR4 (glycopyranosyl lipid adjuvant aqueous formulation) and Dectin-1 (β-glucan peptide) acted synergistically in newborns and adults, but to a lesser extent. The degree of synergy varied dramatically with age, and was the greatest in newborns and infants with less synergy in adults and elders. Overall, combination adjuvant systems demonstrate markedly different immune activation with age, with combined DC activation via Macrophage-inducible C-type lectin and TLR7/8 representing a novel approach to enhance the efficacy of early-life vaccines.

Effectiveness of an immunocastration vaccine formulation to reduce the gonadal function in female and male mice by Th1/Th2 immune response

Immunocastration has emerged as an alternative to surgical castration in different animal species. This study examined the effectiveness of a new vaccine formulation for immunocastration using the biopolymer chitosan as adjuvant. First, female and male mice (n = 4), in three subsequent experiments were vaccinated at Days 1 and 30 of the study, to determine the immune response profile and gonadal alterations due to immunization. The results demonstrated that the vaccine was able to elicit strong antibody responses against native GnRH hormone (P < 0.01), with a T helper (Th) 1/Th2 immune response profile. Along with this, a suppression of gonadal activity with a decrease of luteal bodies (1.08 ± 0.22 and 4.08 ± 0.39) and antral follicles (1.17 ± 0.32 and 4.5 ± 0.38) in the ovaries of immunized females and control, respectively, and a reduction of seminiferous tubules size (142.3 ± 5.58 mm and 198.0 ± 6.11 mm) and germinal cellular layers (3.58 ± 0.26 and 5.08 ± 0.29) of immunized males and control animals, respectively, were observed (P < 0.01). Then, in a study of long-term immune response due to vaccination in female and male mice (n = 4) from two subsequent experiments, a suppression of gonadal function and an induction of a Th1/Th2 immune response was also observed, determined by both, immunoglobulin and cytokine profiles, which lasted until the end of the study (7 months; P < 0.01). The findings of this study have demonstrated that vaccination with a new immunocastration vaccine inducing a Th1/Th2 immune response against GnRH (P < 0.01) elicit a decrease of gonadal function in male and female mice (P < 0.01). Owing to long-term duration of the antibody levels generated, this vaccine formulation appears as a promising alternative for immunocastration of several animal species where long-lasting reproductive block is needed.

Neonatal respiratory syncytial virus infection has an effect on lung inflammation and the CD4(+) CD25(+) T cell subpopulation during ovalbumin sensitization in adult mice

In BALB/c adult mice, respiratory syncytial virus (RSV) infection enhances the degree of lung inflammation before and/or after ovalbumin (OVA) respiratory sensitization. However, it is unclear whether RSV infection in newborn mice has an effect on the immune response to OVA respiratory sensitization in adult mice. The aim of this study was to determine if RSV neonatal infection alters T CD4(+) population and lung inflammation during OVA respiratory sensitization in adult mice. BALB/c mice were infected with RSV on the fourth day of life and challenged by OVA 4 weeks later. We found that in adult mice, RSV neonatal infection prior to OVA sensitization reduces the CD4(+) CD25(+) and CD4(+) CD25(+) forkhead protein 3 (FoxP3)(+) cell populations in the lungs and bronchoalveolar lavage. Furthermore, it also attenuates the inflammatory infiltrate and cytokine/chemokine expression levels in the mouse airways. In conclusion, the magnitude of the immune response to a non-viral respiratory perturbation in adult mice is not enhanced by a neonatal RSV infection.

Evidence for the essentiality of arachidonic and docosahexaenoic acid in the postnatal maternal and infant diet for the development of the infant’s immune system early in life

Long-chain polyunsaturated fatty acids (LCPUFA), especially the balance between arachidonic (AA) and docosahexaenoic (DHA) acids are known to have important immunomodulatory roles during the postnatal period when the immune system is rapidly developing. AA and DHA are required in infant formula in many countries but are optional in North America. The rationale for adding these LCPUFA to full-term formula is based on their presence in breast milk and randomized controlled studies that suggest improved cognitive function in preterm infants, but results are more variable in full-term infants. Recently, the European Food Safety Authority has proposed, based on a lack of functional evidence, that AA is not required in infant formula for full-term infants during the first year of life but DHA should remain mandatory. The purpose of this review is to review the evidence from epidemiological and intervention studies regarding the essentiality of AA and DHA in the postnatal infant and maternal diet (breast-feeding) for the immune system development early in life. Although studies support the essentiality of DHA for the immune system development, more research is needed to rule out the essentiality of AA. Nevertheless, intervention studies have demonstrated improvement in many markers of immune function in infants fed formula supplemented with AA and DHA compared with unsupplemented formula, which appears to consistently result in beneficial health outcomes including reduction in the risk of developing allergic and atopic disease early in life.

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 Form of Choline in the Maternal Diet Affects Immune Development in Suckled Rat Offspring

BACKGROUND

Lipid-soluble phosphatidylcholine (PC) and aqueous free choline are absorbed and metabolized differently, but the metabolic effects of feeding these 2 forms of choline have not been thoroughly investigated.

OBJECTIVE

We sought to compare the effects of PC and free choline in the maternal diet on the development of the offspring's immune system.

METHODS

During lactation, Sprague-Dawley dams (n= 10) were randomly assigned to 1 of 2 diet groups containing the same concentration of total choline (1 g/kg diet) as free choline (choline bitartrate) or PC (egg lecithin). The splenocytes of pups aged 21 d were isolated and stimulated ex vivo with concanavalin A (ConA) or lipopolysaccharide (LPS), and the choline concentrations of stomach content, plasma, and the spleen were measured.

RESULTS

Pups from PC-fed dams had a lower proportion of cells involved in antigen presentation but produced 54% more interleukin (IL)-2, 163% more IL-6, and 107% more IFN-γ after ConA stimulation and 110% more IL-6 and 43% more tumor necrosis factor (TNF)-α after LPS stimulation (allP< 0.05). The PC concentrations were significantly higher in the plasma and spleen of pups from PC-fed dams (P< 0.05). Increasing the supply of PC in the form of lysophosphatidylcholine to splenocytes in vitro increased the rate of proliferation and IL-2 production and the surface expression of CD25, CD28, CD71, and CD152 on CD8+ T cells, suggesting 1 possible mechanism.

CONCLUSIONS

The results of this study demonstrate that providing choline to rats in the form of PC (compared to free choline), possibly by increasing the supply of PC to the suckling pups, promotes maturation and improves function of the offspring's immune system.

Along the Axis between Type 1 and Type 2 Immunity; Principles Conserved in Evolution from Fish to Mammals

A phenomenon already discovered more than 25 years ago is the possibility of naïve helper T cells to polarize into TH1 or TH2 populations. In a simplified model, these polarizations occur at opposite ends of an "immune 1-2 axis" (i1-i2 axis) of possible conditions. Additional polarizations of helper/regulatory T cells were discovered later, such as for example TH17 and Treg phenotypes; although these polarizations are not selected by the axis-end conditions, they are affected by i1-i2 axis factors, and may retain more potential for change than the relatively stable TH1 and TH2 phenotypes. I1-i2 axis conditions are also relevant for polarizations of other types of leukocytes, such as for example macrophages. Tissue milieus with "type 1 immunity" ("i1") are biased towards cell-mediated cytotoxicity, while the term "type 2 immunity" ("i2") is used for a variety of conditions which have in common that they inhibit type 1 immunity. The immune milieus of some tissues, like the gills in fish and the uterus in pregnant mammals, probably are skewed towards type 2 immunity. An i2-skewed milieu is also created by many tumors, which allows them to escape eradication by type 1 immunity. In this review we compare a number of i1-i2 axis factors between fish and mammals, and conclude that several principles of the i1-i2 axis system seem to be ancient and shared between all classes of jawed vertebrates. Furthermore, the present study is the first to identify a canonical TH2 cytokine locus in a bony fish, namely spotted gar, in the sense that it includes RAD50 and bona fide genes of both IL-4/13 and IL-3/ IL-5/GM-CSF families.

Pulmonary immunity during respiratory infections in early life and the development of severe asthma

Asthma affects 10% of the population in Westernized countries, being most common in children. It is a heterogeneous condition characterized by chronic allergic airway inflammation, mucus hypersecretion, and airway hyperresponsiveness (AHR) to normally innocuous antigens. Combination therapies with inhaled corticosteroids and bronchodilators effectively manage mild to moderate asthma, but there are no cures, and patients with severe asthma do not respond to these treatments. The inception of asthma is linked to respiratory viral (respiratory syncytial virus, rhinovirus) and bacterial (Chlamydia, Mycoplasma) infections. The examination of mouse models of early-life infections and allergic airway disease (AAD) provides valuable insights into the mechanisms of disease inception that may lead to the development of more effective therapeutics. For example, early-life, but not adult, Chlamydia respiratory infections in mice permanently modify immunity and lung physiology. This increases the severity of AAD by promoting IL-13 expression, mucus hypersecretion, and AHR. We have identified novel roles for tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and IL-13 in promoting infection-induced pathology in early life and subsequent chronic lung disease. Genetic deletion of TRAIL or IL-13 variously protected against neonatal infection-induced inflammation, mucus hypersecretion, altered lung structure, AHR, and impaired lung function. Therapeutic neutralization of these factors prevented infection-induced severe AAD. Other novel mechanisms and avenues for intervention are also being explored. Such studies indicate the immunological mechanisms that may underpin the association between early-life respiratory infections and the development of more severe asthma and may facilitate the development of tailored preventions and treatments.

Dose-dependent effects of morphine exposure on mRNA and microRNA (miR) expression in hippocampus of stressed neonatal mice

Morphine is used to sedate critically ill infants to treat painful or stressful conditions associated with intensive care. Whether neonatal morphine exposure affects microRNA (miR) expression and thereby alters mRNA regulation is unknown. We tested the hypothesis that repeated morphine treatment in stress-exposed neonatal mice alters hippocampal mRNA and miR expression. C57BL/6 male mice were treated from postnatal day (P) 5 to P9 with morphine sulfate at 2 or 5 mg/kg ip twice daily and then exposed to stress consisting of hypoxia (100% N₂ 1 min and 100% O₂ 5 min) followed by 2h maternal separation. Control mice were untreated and dam-reared. mRNA and miR expression profiling was performed on hippocampal tissues at P9. Overall, 2 and 5 mg/kg morphine treatment altered expression of a total of 150 transcripts (>1.5 fold change, P<0.05) from which 100 unique mRNAs were recognized (21 genes were up- and 79 genes were down-regulated), and 5 mg/kg morphine affected 63 mRNAs exclusively. The most upregulated mRNAs were fidgetin, arginine vasopressin, and resistin-like alpha, and the most down-regulated were defensin beta 11, aquaporin 1, calmodulin-like 4, chloride intracellular channel 6, and claudin 2. Gene Set Enrichment Analysis revealed that morphine treatment affected pathways related to cell cycle, membrane function, signaling, metabolism, cell death, transcriptional regulation, and immune response. Morphine decreased expression of miR-204-5p, miR-455-3p, miR-448-5p, and miR-574-3p. Nine morphine-responsive mRNAs that are involved in neurodevelopment, neurotransmission, and inflammation are predicted targets of the aforementioned differentially expressed miRs. These data establish that morphine produces dose-dependent changes in both hippocampal mRNA and miR expression in stressed neonatal mice. If permanent, morphine–mediated neuroepigenetic effects may affect long-term hippocampal function, and this provides a mechanism for the neonatal morphine-related impairment of adult learning.

Immunity to RSV in Early-Life

Respiratory Syncytial Virus (RSV) is the commonest cause of severe respiratory infection in infants, leading to over 3 million hospitalizations and around 66,000 deaths worldwide each year. RSV bronchiolitis predominantly strikes apparently healthy infants, with age as the principal risk factor for severe disease. The differences in the immune response to RSV in the very young are likely to be key to determining the clinical outcome of this common infection. Remarkable age-related differences in innate cytokine responses follow recognition of RSV by numerous pattern recognition receptors, and the importance of this early response is supported by polymorphisms in many early innate genes, which associate with bronchiolitis. In the absence of strong, Th1 polarizing signals, infants develop T cell responses that can be biased away from protective Th1 and cytotoxic T cell immunity toward dysregulated, Th2 and Th17 polarization. This may contribute not only to the initial inflammation in bronchiolitis, but also to the long-term increased risk of developing wheeze and asthma later in life. An early-life vaccine for RSV will need to overcome the difficulties of generating a protective response in infants, and the proven risks associated with generating an inappropriate response. Infantile T follicular helper and B cell responses are immature, but maternal antibodies can afford some protection. Thus, maternal vaccination is a promising alternative approach. However, even in adults adaptive immunity following natural infection is poorly protective, allowing re-infection even with the same strain of RSV. This gives us few clues as to how effective vaccination could be achieved. Challenges remain in understanding how respiratory immunity matures with age, and the external factors influencing its development. Determining why some infants develop bronchiolitis should lead to new therapies to lessen the clinical impact of RSV and aid the rational design of protective vaccines.

The difference in immune response and IL-12p35 methylation between newborns and adults

Background

The immune system of newborn is generally depressed by impaired production of Th1-cell associated cytokines, which results in increased susceptibility to intracellular pathogens and poor response to vaccinations. For avoiding abortion, the maternal and fetal immune systems tend to Th2-cell polarizing cytokines. Besides, IL-12p35 is a determining factor of the bioactivity of IL-12, which has an important role in the Th1 response. Recently methylated DNA is known to associate to inhibit transcription. Therefore, we explored the methylation status of CpG sites upstream of the coding sequence of the IL-12p35 gene to determine whether neonatal peripheral blood mononuclear cell (PBMC) synthesis lower level of IL-12 is related to methylated DNA.

Results

PBMCs from adults expressed higher levels of IL-12p40 (p = 0.303) and IL-12p70 (p = 0.045) and had a strong ability to produce IL-12p35 mRNA (p = 0.01). However, there was no difference in the methylation status of CpG sites in the promoter of IL-12p35 between adults and newborns.

Conclusions

We found that PBMC synthesis of bioactive IL-12p70 was significantly impaired in the neonatal period, potentially though a reduction in IL-12p35 production. The reeducation in IL-12p35 production might not be due to methylation of the promoter gene. But, the impairment of IL-12p35 expression during the neonatal period might be caused by other epigenetic regulation occurs in the chromatin level.

Immunity to HIV in Early Life

The developing immune system is adapted to the exposure to a plethora of pathogenic and non-pathogenic antigens encountered in utero and after birth, requiring a fine balance between protective immunity and immune tolerance. In early stages of life, this tolerogenic state of the innate and adaptive immune system and the lack of immunological memory render the host more susceptible to infectious pathogens like HIV. HIV pathogenesis is different in children, compared to adults, with more rapid disease progression and a substantial lack of control of viremia compared to adults. Plasma viral load remains high during infancy and only declines gradually over several years in line with immune maturation, even in rare cases where children maintain normal CD4 T-lymphocyte counts for several years without antiretroviral therapy (ART). These pediatric slow progressors also typically show low levels of immune activation despite persistently high viremia, resembling the phenotype of natural hosts of SIV infection. The lack of immunological memory places the fetus and the newborn at higher risk of infections; however, it may also provide an opportunity for unique interventions. Frequencies of central memory CD4+ T-lymphocytes, one of the main cellular reservoirs of HIV, are very low in the newborn child, so immediate ART could prevent the establishment of persistent viral reservoirs and result in "functional cure." However, as recently demonstrated in the case report of the "Mississippi child" who experienced viral rebound after more than 2 years off ART, additional immunomodulatory strategies might be required for sustained viral suppression after ART cessation. In this review, we discuss the interactions between HIV and the developing immune system in children and the potential implications for therapeutic and prophylactic interventions.

Human cord blood γδ T cells expressing public Vγ2 chains dominate the response to bisphosphonate plus interleukin-15

Compared with adults, the circulating Vγ2Vδ2 T-cell population in cord blood is present at low levels and does not show the strong bias for Vγ2-Jγ1.2 rearrangements. These features may be a result of limited exposure to stimulatory phosphoantigens, lack of T-cell-derived interleukin-2 (IL-2) or both. In cord blood mononuclear cell cultures, a single round of stimulation, using aminobisphosphonates to elevate phosphoantigen levels, resulted in expansion of adult-like Vγ2 chains and accumulation of memory cells with cytotoxic potential. Selection was similar using IL-2 or myeloid-derived IL-15. The Vγ2Vδ2 T cells present in neonates are capable of generating potent immune responses even when relying on IL-15.

Deficiencies in the CD4+ T-Helper Cell Arm of the Immune System of Neonates and Young Children

Newborns and young children rely on innate immunity to protect against infections until the adaptive immune system matures. Immunization helps facilitate protection, but multiple doses are needed to establish sufficient antibody levels and T-cell-facilitated immune memory. Deficient T-cell activation and function among neonates and young children are primarily present in the CD4⁺ compartment, whereas CD8⁺ T-cell function is at par with adults. CD4⁺ T cells in neonates and young children produce low levels of IFNγ, interleukin (IL)-2, IL-13, IL-5, and IL-17. This inherent deficiency in neonatal and young child CD4⁺ T-cell functionality has been linked to several mechanistic failures: (1) lower sensitivity to T-cell receptor stimulation, (2) increased apoptosis after proliferation, (3) unavailability of antigen for T-cell priming, and (4) inefficient stimulation by relatively immature antigen-presenting cells. In this review, we discuss evidence from infection and vaccination responses that shed light on the various checkpoints possibly involved in delayed maturation of CD4⁺ T-cell activation and function in newborns and young children.

Association of Expanded Disability Status Scale and Cytokines after Intervention with Co-supplemented Hemp Seed, Evening Primrose Oils and Hot-natured Diet in Multiple Sclerosis Patients(♦)

INTRODUCTION

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS). Because of limited efficacy and adverse side effects, identifying novel therapeutic and protective agents is important. The aim of this study is to examine the correlations between expanded disability status scale (EDSS) and cytokines after intervention with co-supplemented hemp seed and evening primrose oils and hot-natured diet in patients with relapsing-remitting multiple sclerosis (RRMS).

METHODS

We studied a group of 23 patients with clinically definite RRMS, with EDSS<6 who received co-supplemented hemp seed and evening primrose oils with advising hot-natured diet. Clinically EDSS and immunological factors (plasma cytokines of IL-4, IFN-γ and IL-17) were assessed at baseline and after 6 months.

RESULTS

Mean follow-up was 180±2.9 days (N=23, 7 Male and 16 Females aged 25.0±7.5 years with disease duration 6.26±3.9 years). After 6 months, significant improvements in extended disability status score were found in the patients in agreement with decrease cytokines of IFN-γ and IL-17 and increase cytokines of IL-4. Clinical and immunological parameters showed improvement in the patients after the intervention.

CONCLUSION

Our study shows that co-supplemented hemp seed and evening primrose oils with hot-natured diet can have beneficial effects in improving clinical symptoms in relapsing remitting MS patients and significant correlation was found between EDSS and immunological findings.

Functional deficits of pertussis-specific CD4+ T cells in infants compared to adults following DTaP vaccination

Understanding the immune responses that explain why infants require multiple doses of pertussis vaccine to achieve protection against infection is a high priority. The objective of this study was to compare the function and phenotypes of antigen-specific CD4(+) T cells in adults (n=12), compared to infants (n=20), following vaccination with acellular pertussis (DTaP) vaccine. Peripheral blood mononuclear cells (PBMCs) were stimulated with pertussis toxoid (PT), pertactin (PRN) and filamentous haemagglutinin (FHA). Multi-parameter flow cytometry was used to delineate CD4(+) T cell populations and phenotypes producing interferon (IFN)-γ, interleukin (IL)-2, tumour necrosis factor (TNF)-α and IL-4. Based on surface CD69 expression, infants demonstrated activation of vaccine antigen-specific CD4(+) T cells similar to adults. However, among infants, Boolean combinations of gates suggested that type 1 (Th-1) CD4(+) T cell responses were confined largely to TNF-α(+) IL-2(+) IFN-γ(-) or TNF-α(+) IL-2(-) IFN-γ(-) . A significantly lower percentage of polyfunctional T helper type 1 (Th1) responses (TNF-α(+) IFN-γ(+) IL-2(+) ) and type 2 (Th2) responses (IL-4) were present in the infants compared to adults. Moreover, a significantly higher percentage of infants' functional CD4(+) T cells were restricted to CD45RA(-) CCR7(+) CD27(+) phenotype, consistent with early-stage differentiated pertussis-specific memory CD4(+) T cells. We show for the first time that DTaP vaccination-induced CD4(+) T cells in infants are functionally and phenotypically dissimilar from those of adults.

In utero exposure to second-hand smoke aggravates adult responses to irritants: adult second-hand smoke

In utero exposure to second-hand smoke (SHS) is associated with exacerbated asthmatic responses in children. We tested the hypothesis that in utero SHS will aggravate the lung responses of young adult mice re-exposed to SHS. We exposed Balb/c mice in utero to SHS (S) or filtered air (AIR; A), and re-exposed the male offspring daily from 11-15 weeks of age to either SHS (AS and SS) or AIR (AA and SA). After the adult exposures, we analyzed samples of bronchoalveolar lavage fluid (BALF), examined the results of histopathology, and assessed pulmonary function and gene expression changes in lung samples. In SS mice, compared with the other three groups (AA, AS, and SA), we found decreases in breathing frequency and increases in airway hyperresponsiveness (AHR), as well as low but significantly elevated concentrations of BALF proinflammatory cytokines (IL-1b, IL-6, and keratinocyte-derived chemokine). Lung morphometric analyses revealed enlarged airspaces and arteries in SA and SS mice compared with their in utero AIR counterparts, as well as increased collagen deposition in AS and SS mice. Unique gene expression profiles were found for in utero, adult, and combined exposures, as well as for mice with elevated AHR responses. The profibrotic metalloprotease genes, Adamts9 and Mmp3, were up-regulated in the SS and AHR groups, suggesting a role for in utero SHS exposure on the adult development of chronic obstructive pulmonary disease. Our results indicate that in utero exposures to environmentally relevant concentrations of SHS alter lung structure more severely than do adult SHS exposures of longer duration. These in utero exposures also aggravate AHR and promote a profibrotic milieu in adult lungs.

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.

TLR2, but not TLR4, is required for effective host defence against Chlamydia respiratory tract infection in early life

Chlamydia pneumoniae commonly causes respiratory tract infections in children, and epidemiological investigations strongly link infection to the pathogenesis of asthma. The immune system in early life is immature and may not respond appropriately to pathogens. Toll-like receptor (TLR)2 and 4 are regarded as the primary pattern recognition receptors that sense bacteria, however their contribution to innate and adaptive immunity in early life remains poorly defined. We investigated the role of TLR2 and 4 in the induction of immune responses to Chlamydia muridarum respiratory infection, in neonatal wild-type (Wt) or TLR2-deficient (^−/−), 4^−/− or 2/4^−/− BALB/c mice. Wt mice had moderate disease and infection. TLR2^−/− mice had more severe disease and more intense and prolonged infection compared to other groups. TLR4^−/− mice were asymptomatic. TLR2/4^−/− mice had severe early disease and persistent infection, which resolved thereafter consistent with the absence of symptoms in TLR4^−/− mice. Wt mice mounted robust innate and adaptive responses with an influx of natural killer (NK) cells, neutrophils, myeloid (mDCs) and plasmacytoid (pDCs) dendritic cells, and activated CD4⁺ and CD8⁺ T-cells into the lungs. Wt mice also had effective production of interferon (IFN)γ in the lymph nodes and lung, and proliferation of lymph node T-cells. TLR2^−/− mice had more intense and persistent innate (particularly neutrophil) and adaptive cell responses and IL-17 expression in the lung, however IFNγ responses and T-cell proliferation were reduced. TLR2/4^−/− mice had reduced innate and adaptive responses. Most importantly, neutrophil phagocytosis was impaired in the absence of TLR2. Thus, TLR2 expression, particularly on neutrophils, is required for effective control of Chlamydia respiratory infection in early life. Loss of control of infection leads to enhanced but ineffective TLR4-mediated inflammatory responses that prolong disease symptoms. This indicates that TLR2 agonists may be beneficial in the treatment of early life Chlamydia infections and associated diseases.

Partial protection against enterovirus 71 (EV71) infection in a mouse model immunized with recombinant Newcastle disease virus capsids displaying the EV71 VP1 fragment

Enterovirus 71 (EV71) infection may cause severe neurological complications, particularly in young children. Despite the risks, there are still no commercially available EV71 vaccines. Hence, a candidate vaccine construct, containing recombinant Newcastle disease virus capsids that display an EV71 VP1 fragment (NPt-VP1(1-100) ) protein, was evaluated in a mouse model of EV71 infection. Previously, it was shown that this protein construct provoked a strong immune response in vaccinated adult rabbits. That study, however, did not address the issue of its effectiveness against EV71 infection in young animals. In the present study, EV71 viral challenge in vaccinated newborn mice resulted in more than 40% increase in survival rate. Significantly, half of the surviving mice fully recovered from their paralysis. Histological analysis of all of the surviving mice revealed a complete clearance of EV71 viral antigens from their brains and spinal cords. In hind limb muscles, the amounts of the antigens detected correlated with the degrees of tissue damage and paralysis. Findings from this study provide evidence that immunization with the NPt-VP1(1-100) immunogen in a newborn mouse model confers partial protection against EV71 infection, and also highlights the importance of NPt-VP1(1-100) as a possible candidate vaccine for protection against EV71 infections.

Immune Responses to rAAV6: The Influence of Canine Parvovirus Vaccination and Neonatal Administration of Viral Vector

Recombinant adeno-associated viral (rAAV) vectors promote long-term gene transfer in many animal species. Significant effort has focused on the evaluation of rAAV delivery and the immune response in both murine and canine models of neuromuscular disease. However, canines provided for research purposes are routinely vaccinated against canine parvovirus (CPV). rAAV and CPV possess significant homology and are both parvoviruses. Thus, any immune response generated to CPV vaccination has the potential to cross-react with rAAV vectors. In this study, we investigated the immune response to rAAV6 delivery in a cohort of CPV-vaccinated canines and evaluated multiple vaccination regimens in a mouse model of CPV-vaccination. We show that CPV-vaccination stimulates production of neutralizing antibodies with minimal cross-reactivity to rAAV6. In addition, no significant differences were observed in the magnitude of the rAAV6-directed immune response between CPV-vaccinated animals and controls. Moreover, CPV-vaccination did not inhibit rAAV6-mediated transduction. We also evaluated the immune response to early rAAV6-vaccination in neonatal mice. The influence of maternal hormones and cytokines leads to a relatively permissive state in the neonate. We hypothesized that immaturity of the immune system would permit induction of tolerance to rAAV6 when delivered during the neonatal period. Mice were vaccinated with rAAV6 at 1 or 5 days of age, and subsequently challenged with rAAV6 exposure during adulthood via two sequential IM injections, 1 month apart. All vaccinated animals generated a significant neutralizing antibody response to rAAV6-vaccination that was enhanced following IM injection in adulthood. Taken together, these data demonstrate that the immune response raised against rAAV6 is distinct from that which is elicited by the standard parvoviral vaccines and is sufficient to prevent stable tolerization in neonatal mice.

Immune adjuvants in early life: targeting the innate immune system to overcome impaired adaptive response

The neonatal phase is a transitory period characterized by an absence of memory cells, favoring a slow adaptive response prone to tolerance effects and the development of Th2-type responses. However, when appropriately stimulated, neonates may achieve an immune response comparable with adult counterparts. One strategy to stimulate the immunological response of neonates or children in early infancy has been to explore natural or synthetic ligands of cell receptors to stimulate innate immunity. The use of adjuvants for activating different cell receptors may be the key to enhancing neonatal adaptive immunity. This review highlights recent advances in the emerging field of molecular adjuvants of innate immune response and their implications for the development of immunotherapies, with particular focus on the neonatal period.

Regulation of Th2 responses and allergic inflammation through bystander activation of CD8+ T lymphocytes in early life

Th2-biased immune responses characterizing neonates may influence the later onset of allergic disease. The contribution of regulatory T cell populations in the prevention of Th2-driven pathologies in early life is poorly documented. We investigated the potential of CD8(+) T cells stimulated at birth with alloantigens to modulate the development of allergic airway inflammation. Newborn mice were immunized with semiallogeneic splenocytes or dendritic cells (DCs) and exposed at the adult stage to OVA aeroallergens. DC-immunized animals displayed a strong Th1 and Tc1/Tc2 alloantigen-specific response and were protected against the development of the allergic reaction with reduced airway hyperresponsiveness, mucus production, eosinophilia, allergen-specific IgE and IgG(1), and reduction of lung IL-4, IL-5, IL-10, and IL-13 mRNA levels. By contrast, splenocyte-immunized mice displayed a Th2 and a weak Tc2 alloantigen-specific response and were more sensitive to the development of the allergen-specific inflammation compared with mice unexposed at birth to alloantigens. DC-immunized animals displayed an important increase in the percentage of IFN-gamma-producing CD8(+)CD44(high), CD8(+)CD62L(high), and CD8(+)CD25(+) subsets. Adoptive transfers of CD8(+) T cells from semiallogeneic DC-immunized animals to adult beta(2)m-deficient animals prevented the development of allergic response, in particular IgE, IL-4, and IL-13 mRNA production in an IFN-gamma-dependent manner, whereas transfers of CD8(+) T cells from semiallogeneic splenocyte-immunized mice intensified the lung IL-4 and IL-10 mRNA level and the allergen-specific IgE. These findings demonstrated that neonatal induction of regulatory CD8(+) T cells was able to modulate key parameters of later allergic sensitization in a bystander manner, without recognition of MHC class I molecules.

Pathogens and immunologic memory in asthma: what have we learned?

Animal models and clinical studies of asthma have generated important insights into the first effector phase leading to the development of allergic airway disease and bronchial hyper-reactivity. In contrast, mechanisms related to asthma chronicity or persistence are less well understood. The CD4(+) T-helper 2 lymphocytes are known initiators of the inflammatory response associated with asthma. There is now increasing evidence that memory T-cells, sensitized against allergenic, occupational or viral antigens, are also involved in the persistence of asthma. Additionally, the role of pathogens in asthma has been linked to both the initial susceptibility to and flares of this disease. This review will discuss the potential links between infection and asthma, the role of the memory T-cells in asthma, and the potential mechanisms by which these factors interact to lead to the development and/or persistence of asthma.

Yersinia enterocolitica promotes robust mucosal inflammatory T-cell immunity in murine neonates

Mucosal immunity to gastrointestinal pathogens in early life has been studied only slightly. Recently, we developed an infection model in murine neonates using the gastroenteric pathogen Yersinia enterocolitica. Here, we report that oral infection of neonatal mice with low doses of virulent Y. enterocolitica leads to vigorous intestinal and systemic adaptive immunity. Y. enterocolitica infection promoted the development of anti-LcrV memory serum IgG1 and IgG2a responses of comparable affinity and magnitude to adult responses. Strikingly, neonatal mesenteric lymph node CD4(+) T cells produced Yersinia-specific gamma interferon (IFN-gamma) and interleukin-17A (IL-17A), exceeding adult levels. The robust T- and B-cell responses elicited in neonates exposed to Y. enterocolitica were associated with long-term protection against mucosal challenge with this pathogen. Using genetically deficient mice, we found that IFN-gamma and CD4(+) cells, but not B cells, are critical for protection of neonates during primary Y. enterocolitica infection. In contrast, adults infected with low bacterial doses did not require either cell population for protection. CD4-deficient neonatal mice adoptively transferred with CD4(+) cells from wild-type, IFN-gamma-deficient, or IL-17AF-deficient mice were equally protected from infection. These data demonstrate that inflammatory CD4(+) T cells are required for protection of neonatal mice and that this protection may not require CD4-derived IFN-gamma, IL-17A, or IL-17F. Overall, these studies support the idea that Y. enterocolitica promotes the development of highly inflammatory mucosal responses in neonates and that intestinal T-cell function may be a key immune component in protection from gastrointestinal pathogens in early life.

Immunogenicity of aggregates of recombinant human growth hormone in mouse models

Aggregation of recombinant therapeutic protein products is a concern due to their potential to induce immune responses. We examined the immunogenicity of protein aggregates in commercial formulations of recombinant human growth hormone produced by freeze-thawing or agitation, two stresses commonly encountered during manufacturing, shipping and handling of therapeutic protein products. In addition, we subjected each preparation to high-pressure treatment to reduce the size and concentration of aggregates present in the samples. Aggregates existing in a commercial formulation, as well as aggregates induced by freeze-thawing and agitation stresses enhanced immunogenicity in one or more mouse models. The use of high-pressure treatment to reduce size and concentrations of aggregates within recombinant human growth hormone formulations reduced their overall immunogenicity in agreement with the "immunon" hypothesis.

Children's immunology, what can we learn from animal studies (2): Modulation of systemic Th1/Th2 immune response in infant mice after prenatal exposure to low-level toluene and toll-like receptor (TLR) 2 ligand

It has been reported that the newborn immune system differs quantitatively and functionally from that of adults. Development of the immune system has important implications for childhood diseases. The immaturity of the immune system in the prenatal or suckling stage may contribute to susceptibility to environmental toxic chemical exposure. In the present study, to clarify the effect of low-level toluene exposure on immune functions during developmental stage, pregnant mice were exposed to 0, 5, and 50 ppm toluene from gestational day 14 to day 19 with or without stimulation by peptidoglycan (PGN) of a gram-positive bacterial cell wall component, a toll-like receptor (TLR) 2 ligand. We examined Th1/Th2 balance in the offspring's at 3 weeks old using ELISA and real-time RT-PCR methods. Exposure of mice to 50 ppm toluene enhanced total immunoglobulin (Ig) G2a (Th1-dependent) level in plasma. On the other hand, splenic expression of transcription factor T-bet (Th1-specific), GATA-3 (Th2-specific) and Foxp3 (gene marker for regulatory CD4+CD25+ T-cells) mRNAs was suppressed in these mice, but not in the combination of 5 or 50 ppm toluene with PGN. In addition, total IgG1 (Th2 dependent) level was suppressed in the combination of 5 or 50 ppm toluene with PGN. Our findings indicate that modulation of Th1- and Th2-responses may occur in low-level toluene exposure and/or combination with PGN stimulation in infant mice.

Antiinfective properties of human milk

The unfavorable effects of neonatal immunodeficiency are limited by some naturally occurring compensatory mechanisms, such as the introduction of protective and immunological components of human milk in the infant. Breast-feeding maintains the maternal-fetal immunological link after birth, may favor the transmission of immunocompetence from the mother to her infant, and is considered an important contributory factor to the neonatal immune defense system during a delicate and crucial period for immune development. Several studies have reported that breast-feeding, because of the antimicrobial activity against several viruses, bacteria, and protozoa, may reduce the incidence of infection in infants. The protection from infections may be ensured either passively by factors with antiinfective, hormonal, enzymatic, trophic, and bioactive activity present in breast milk, or through a modulator effect on the neonatal immune system exerted by cells, cytokines, and other immune agents in human milk.

Murine neonates develop vigorous in vivo cytotoxic and Th1/Th2 responses upon exposure to low doses of NIMA-like alloantigens

Early life exposure to noninherited maternal antigens (NIMAs) may occur via transplacental transfer and/or breast milk. There are indications that early life exposure to NIMAs may lead to lifelong tolerance. However, there is mounting evidence that exposure to NIMAs may also lead to immunologic priming. Understanding how these different responses arise could be critical in transplantation with donor cells expressing NIMAs. We recently reported that murine neonates that received a transplant of low doses of NIMA-like alloantigens develop vigorous memory cytotoxic responses, as assessed by in vitro assays. Here, we demonstrate that robust allospecific cytotoxicity is also manifest in vivo. Importantly, at low doses, NIMA-expressing cells induced the development of in vivo cytotoxicity during the neonatal period. NIMA-exposed neonates also developed vigorous primary and memory allospecific Th1/Th2 responses that exceeded the responses of adults. Overall, we conclude that exposure to low doses of NIMA-like alloantigens induces robust in vivo cytotoxic and Th1/Th2 responses in neonates. These findings suggest that early exposure to low levels of NIMA may lead to long-term immunologic priming of all arms of T-cell adaptive immunity, rather than tolerance.

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.

Effects of environmental tobacco smoke exposure on pulmonary immune response in infant monkeys

BACKGROUND

Exposure to environmental tobacco smoke (ETS) in early life has adverse effects on lung development and increases asthma incidence and susceptibility to infection. We have previously reported that perinatal and postnatal exposure to ETS in infant monkeys leads to an impaired T(H)1 immune response in peripheral blood.

OBJECTIVE

Determine whether ETS exposure during the perinatal period alters pulmonary immune maturation in the neonatal lung.

METHODS

Nonhuman primates were exposed to ETS from gestation day 50 to 13 months postnatal age (perinatal ETS) or from 6 to 13 months (postnatal ETS). Control animals were only exposed to filtered air. T(H)1 and T(H)2-related cytokines, chemokines, and their corresponding receptors as well as transcription factors were analyzed in lung tissues at 13 months.

RESULTS

Animals exposed to ETS beginning in utero exhibited more profound alterations in T(H)1 factors compared with animals exposed to ETS beginning at 6 months postnatal age. In perinatal ETS-exposed monkeys, mRNA for IFN-gamma, IL-2, IFN-gamma-inducible protein 10, monokine induced by IFN-gamma, IFN-gamma-inducible T-cell chemoattractant, CXC chemokine receptor 3, IL-12 bioactive p70 subunit, and T-bet were significantly downregulated, whereas in postnatal ETS-exposed monkeys, only IFN-gamma, CXC chemokine receptor 3, and IL-12p70 were significantly downregulated. ETS effects on T(H)2 factors were less apparent and more variable: mRNA for thymus and activation-regulated chemokine was increased, and IL-10 protein was reduced.

CONCLUSIONS

Environmental tobacco smoke exposure during early life enhances a local T(H)2 immunity by impairing normal pulmonary T(H)1 immune maturation. This effect was greater in animals beginning ETS exposure in utero.

Maternal transmission of resistance to development of allergic airway disease

Parental phenotype is known to influence the inheritance of atopic diseases, such as allergic asthma, with a maternal history being a more significant risk factor for progeny than paternal history. We hypothesized that recall Th1- or Th2-type immune responses during pregnancy would result in transfer of maternal factors that would differentially impact development of immune responsiveness in offspring. Following weaning, susceptibility and severity of allergic airway disease (a murine model of human asthma) was evaluated in progeny, disease being elicited by immunization with OVA-Al(OH)(3) and challenge with aerosolized OVA. We found that progeny of mothers with Th1-biased immunity to OVA subjected to recall aerosol challenge during pregnancy had reduced levels of Ag-specific IgE and airway eosinophilia compared with progeny of mothers with Th2-biased immunity to OVA or naive mothers. Interestingly, progeny of mothers with Th1-type immunity to a heterologous albumin, BSA, were not protected from developing OVA-induced allergic airway disease. These findings demonstrated that maternal transfer of protection from development of allergic airway disease to offspring in this model of maternal Th1-type immunity was Ag specific.

Effects of environmental tobacco smoke on the developing immune system of infant monkeys

BACKGROUND

Exposure to environmental tobacco smoke (ETS) is associated with an increased incidence of allergic and infectious diseases among children that is thought to be partly due to the immaturity of the immune system.

OBJECTIVE

We sought to investigate the effects of ETS exposure on immune development during the first year of life in the nonhuman primate.

METHODS

Fifteen neonatal rhesus monkeys studied to 13 months of postnatal age were randomized into 3 groups: (1) exposure to filtered air, (2) continuous ETS exposure beginning at gestation day 50 (perinatal ETS); and (3) exposure to ETS beginning at 6 months of age (6-month ETS). Complete blood counts, lymphocyte subsets, and mRNA levels of 12 cytokines in PBMCs were measured.

RESULTS

Fetal/infant exposure to ETS altered the normal maturation of mRNA levels of IFN-gamma, IL-2, and IL-10, as well as the ratio of CD4 to CD8 lymphocytes, compared with filtered-air control levels. Blood lymphocyte subset distribution also significantly differed based on the onset of exposure to ETS. Subacute exposure to ETS for 2 weeks in 6-month-old infants was found to increase levels of peripheral blood neutrophils and IL-6 mRNA.

CONCLUSIONS

Short-term exposure to ETS can induce an acute systemic inflammatory response in the neonatal nonhuman primate, and long-term exposure to ETS beginning in utero or at 6 months of postnatal age can significantly alter immune effectors.

CLINICAL IMPLICATIONS

Normal immune system development is compromised by in utero and postnatal exposure to ETS and might contribute to ETS-related childhood diseases.

Cytokine concentrations during the first days of life

OBJECTIVE

To evaluate the cytokine concentration patterns during the first 5 days of life by measuring serum concentrations of type-1 cytokines, like interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) and type-2 cytokines, like IL-4, as well as the receptors of IL-2 (sIL-2R) and IL-4 (sIL-4R) during the early neonatal period.

SUBJECTS AND METHODS

Forty-two healthy term neonates were included in the study. Cytokine concentrations were measured in umbilical cord, in the 1st and 5th day after birth and compared with those in serum of 30 healthy adults.

RESULTS

IL-2 concentrations presented a decrease trend from umbilical cord to 5th day, while sIL-2R showed a significant elevation from umbilical cord to 5th day after birth. IL-4 concentrations did not differ significantly among umbilical cord, the 1st and the 5th day, while the sIL-4R showed the highest values in the 1st day after birth. Both IL-4 and sIL-4R concentrations in neonatal samples were elevated compared to adults. IFN-gamma concentrations increased significantly from umbilical cord to 5th day of life.

CONCLUSION

Our findings indicate a dysregulation among IL-2, IL-4 and IFN-gamma concentrations during the 1st day after birth, favoring a more precocious expression of IL-2 and IL-4 against IFN-gamma that seems to be ameliorated in the end of the 1st week of life.