Characterization of lymphocyte subsets from mucosal tissues in neonatal swine

Immune status of piglets during the first week of life: Current knowledge, significance and assessment

The immune system of neonate piglets differs from adult pigs in structure and competence. Although piglets are born immunocompetent, they are genuinely immunologically defenceless. To survive in the environment, piglets need passive protection provided by sow’s colostrum and milk when constantly exposed to numerous pathogens. Early assessment of piglets’ immune status may enable rapid intervention in case of detection of any deficiencies or disorders. Moreover, awareness of the piglets’ immunocompetence and the level of maternally-derived antibodies (MDA) may allow the creation of a proper vaccine schedule. Hence, extending knowledge of prenatal ontogeny of the porcine immune system, the immune status of neonate piglets’ and the immunological components of porcine colostrum is crucial. Since animal welfare has become a more critical element of animal production, new, non-invasive sampling methodologies are highly desirable for the evaluation of piglets’ immune status.

Intraepithelial lymphocytes in the pig intestine: T cell and innate lymphoid cell contributions to intestinal barrier immunity

Intraepithelial lymphocytes (IELs) include T cells and innate lymphoid cells that are important mediators of intestinal immunity and barrier defense, yet most knowledge of IELs is derived from the study of humans and rodent models. Pigs are an important global food source and promising biomedical model, yet relatively little is known about IELs in the porcine intestine, especially during formative ages of intestinal development. Due to the biological significance of IELs, global importance of pig health, and potential of early life events to influence IELs, we collate current knowledge of porcine IEL functional and phenotypic maturation in the context of the developing intestinal tract and outline areas where further research is needed. Based on available findings, we formulate probable implications of IELs on intestinal and overall health outcomes and highlight key findings in relation to human IELs to emphasize potential applicability of pigs as a biomedical model for intestinal IEL research. Review of current literature suggests the study of porcine intestinal IELs as an exciting research frontier with dual application for betterment of animal and human health.

Immunosafety evaluation in Juvenile Göttingen Minipigs

Although an extrapolation from the clinical experience in adults can often be considered to support the pediatric use for most pharmaceutical compounds, differences in safety profiles between adult and pediatric patients can be observed. The developing immune system may be affected due to exaggerated pharmacological or non-expected effects of a new drug. Toxicology studies in juvenile animals could therefore be required to better evaluate the safety profile of any new pharmaceutical compound targeting the pediatric population. The Göttingen minipig is now considered a useful non-rodent species for non-clinical safety testing of human pharmaceuticals. However, knowledge on the developing immune system in juvenile minipigs is still limited. The objective of the work reported here was to evaluate across-age proportions of main immune cells circulating in blood or residing in lymphoid organs (thymus, spleen, lymph nodes) in Göttingen Minipigs. In parallel, the main immune cell populations from healthy and immunocompromised piglets were compared following treatment with cyclosporin A (CsA) at 10 mg/kg/day for 4 wk until weaning. The study also assessed functionality of immune responses using an in-vivo model after "Keyhole limpet hemocyanin" (KLH) immunization and an ex-vivo lymph proliferation assay after stimulation with Concanavalin A. The results demonstrated variations across age in circulating immune cell populations including CD21⁺ B-cells, αβ-T- and γδ-T-cells, NK cells, and monocytes. CsA-induced changes in immune functions were only partially recovered by 5 mo after the end of treatment, whereas the immune cell populations affected by the treatment returned to normal levels in animals of the same age. Taken together, the study here shows that in this model, the immune function endpoints were more sensitive than the immunophenotyping endpoints.

Swine unconventional T cells

Pigs are important domestic livestock and a comprehensive understanding of their immune system is critical to improve swine vaccine efficacy. Pig models represent an excellent animal model for immunological studies because of their anatomical and physiological similarities to humans. A significant portion of pig immunological studies focused on characterizing the conventional T cell (Tconv) immune responses. These cells recognize peptides presented by major histocompatibility complex (MHC) proteins. In contrast, unconventional T cells are non-MHC-restricted and profoundly regulate conventional T cells. Key subsets of unconventional T cells reviewed here include natural killer T (NKT) cells, γδ T cells, mucosal-associated invariant T (MAIT) cells, intraepithelial lymphocytes (IELs), and two potential unconventional T cell subsets expressing NKp46 or CD11b. Unlike Tconvs, most of these cells recognize lipids, small molecule metabolites, or modified peptides, and they generally show simplified patterns of T cell receptor (TCR) expression and rapid effector responses. Here, we review that unconventional T cells are an abundant and critical component of the porcine immune system, summarize the current understanding of these cells, and highlight some of the key differences among mouse, human, and porcine unconventional T cells.

Early supplementation with Lactobacillus plantarum in liquid diet modulates intestinal innate immunity through toll-like receptor 4-mediated mitogen-activated protein kinase signaling pathways in young piglets challenged with Escherichia coli K88

This study was conducted to investigate the effects of early supplementation during 4 to 18 d of age with Lactobacillus plantarum (LP) in liquid diets on intestinal innate immune response in young piglets infected with enterotoxigenic Escherichia coli (ETEC) K88. Seventy-two barrow piglets at 4 d old were assigned to basal or LP-supplemented liquid diet (5 × 1010 CFU·kg-1). On day 15, piglets from each group were orally challenged with either ETEC K88 (1 × 108 CFU·kg-1) or the same amount of phosphate-buffered saline. The intestinal mucosa, mesenteric lymph node (MLN), and spleen samples were collected on day 18. Here, we found that LP pretreatment significantly decreased the mRNA relative expression of inflammatory cytokines (interleukin [IL]-1β, IL-8, and tumor necrosis factor-α), porcine β-defensin 2 (pBD-2), and mucins (MUC1 and MUC4) in the jejunal mucosa in piglets challenged with ETEC K88 (P < 0.05). Moreover, LP significantly decreased the ileal mucosa mRNA relative expression of IL-8 and MUC4 in young piglets challenged with ETEC K88 (P < 0.05). Furthermore, the piglets of the LP + ETEC K88 group had lower protein levels of IL-8, secretory immunoglobulin A, pBD-2, and MUC4 in the jejunal mucosa than those challenged with ETEC K88 (P < 0.05). Besides, LP supplementation reduced the percentage of gamma/delta T cells receptor (γδTCR) and CD172a+ (SWC3+) cells in MLN and the percentage of γδTCR cells in the spleen of young piglets after the ETEC K88 challenge. Supplementation with LP in liquid diets prevented the upregulated protein abundance of toll-like receptor (TLR) 4, phosphorylation-p38, and phosphorylation-extracellular signal-regulated protein kinases in the jejunal mucosa induced by ETEC K88 (P < 0.05). In conclusion, LP supplementation in liquid diet possesses anti-inflammatory activity and modulates the intestinal innate immunity during the early life of young piglets challenged with ETEC K88, which might be attributed to the suppression of TLR4-mediated mitogen-activated protein kinase signaling pathways. Early supplementation with LP in liquid diets regulates the innate immune response, representing a promising immunoregulation strategy for maintaining intestinal health in weaned piglets.

Impact of birth weight and neonatal nutritional interventions with micronutrients and bovine colostrum on the development of piglet immune response during the peri-weaning period

Immune system development of piglets is influenced by birth weight and colostrum and milk intake. Moreover, the dam transfer to piglets of vitamins A and D and copper, which play important role in immunity, is limited during lactation. In this study, we evaluated the potential of maternal and neonatal supplementations with vitamins A and D and copper, with or without neonatal supplementation of bovine colostrum (BC), to modulate the immune system development of low birth weight (LBW) and high birth weight (HBW) piglets during the peri-weaning period. Litters from 23 control sows (CONT) were assigned to one of the following treatments: 1) control (C); 2) oral administration at 2 and 8 days (d) of age of retinol-acetate, 25-hydroxyvitamin D and CuSO₄ and exposure to UVB light for 15 min every second day from d 5 to d 21 (ADCu); 3) oral administration of dehydrated BC (4 g/d) from d 5 to d 10 (BC); 4) ADCu + BC. This experimental design was repeated with 24 sows fed extra daily supplements of 25-hydroxyvitamin D (4,000 IU), β-carotene (30,000 IU) and Cu-yeast (equivalent 45 mg of Cu) from 90 d of gestation until weaning at d 21 (SUPPL). Within each litter, 2 LBW and 2 HBW piglets were euthanized at d 16 and d 23 in order to characterize leukocyte subsets in mesenteric lymph nodes (MLN) and blood by flow cytometry, and to measure gene expression in the MLN and jejunal mucosa by qPCR. At d 16, results revealed that the percentages of γδ and cytotoxic T lymphocytes were significantly reduced in LBW compared to HBW piglets. The jejunal expression of interleukin (IL) 22 was also up-regulated, along with MLN expression of C-C Motif Chemokine Ligand 23, bone morphogenetic protein 2 and secreted phosphoprotein 1 (SPP1), whereas jejunal expression of tumor necrosis factor α was decreased in LBW piglets. At d 23, LBW piglets showed lower amounts of γδ T lymphocytes, higher percentages of CD3^- and CD3^-CD8α⁺CD16⁺ leukocytes (which include Natural killer cells) and lower jejunal expression of IL18. Furthermore, supplementation with BC increased the blood percentage of CD3^-CD16⁺ leukocytes and reduced jejunal IL5 and MLN IL15 expression whereas supplementation with ADCu + BC increased jejunal TNF superfamily 13B and MLN SPP1 expression. Our results suggest that immune system development after birth differed between LBW and HBW piglets and that early dietary supplementation with BC and ADCu has the potential to modulate development of immune functions.

Intraepithelial T Cells Diverge by Intestinal Location as Pigs Age

T cells resident within the intestinal epithelium play a central role in barrier integrity and provide a first line of immune defense. Intraepithelial T cells (IETs) are among the earliest immune cells to populate and protect intestinal tissues, thereby giving them an important role in shaping gut health early in life. In pigs, IETs are poorly defined, and their maturation in young pigs has not been well-studied. Given the importance of IETs in contributing to early life and long-term intestinal health through interactions with epithelial cells, the microbiota, and additional environmental factors, a deeper characterization of IETs in pigs is warranted. The objective of this study was to analyze age- and intestinal location-dependent changes in IETs across multiple sites of the small and large intestine in pigs between 4- and 8-weeks of age. IETs increased in abundance over time and belonged to both γδ and αβ T cell lineages. Similar compositions of IETs were identified across intestinal sites in 4-week-old pigs, but compositions diverged between intestinal sites as pigs aged. CD2⁺CD8α⁺ γδ T cells and CD4^-CD8α⁺ αβ T cells comprised >78% of total IETs at all intestinal locations and ages examined. Greater percentages of γδ IETs were present in large intestine compared to small intestine in older pigs. Small intestinal tissues had greater percentages of CD2⁺CD8α^- γδ IETs, while CD2⁺CD8α⁺ γδ IET percentages were greater in the large intestine. Percentages of CD4^-CD8α⁺ αβ IETs increased over time across all intestinal sites. Moreover, percentages of CD27⁺ cells decreased in ileum and large intestine over time, indicating increased IET activation as pigs aged. Percentages of CD27⁺ cells were also higher in small intestine compared to large intestine at later timepoints. Results herein emphasize 4- to 8-weeks of age as a critical window of IET maturation and suggest strong associations between intestinal location and age with IET heterogeneity in pigs.

The Effect of Dietary Mushroom Agaricus bisporus on Intestinal Microbiota Composition and Host Immunological Function

A study was designed to determine the potential prebiotic effect of dietary mushrooms on the host immune response, and intestinal microbiota composition and function. Thirty-one six-week-old pigs were fed a pig grower diet alone or supplemented with either three or six servings of freeze-dried white button (WB)-mushrooms for six weeks. Host immune response was evaluated in peripheral blood mononuclear cells (PBMC), and alveolar macrophages (AM) after stimulation with Salmonella typhymurium-Lipopolysaccharide (LPS). Isolated DNA from fecal and proximal colon contents were used for 16S rDNA taxonomic analysis and linear discriminant analysis effect size (LEfSe) to determine bacterial abundance and metabolic function. Pigs gained weight with no difference in body composition or intestinal permeability. Feeding mushrooms reduced LPS-induced IL-1β gene expression in AM (P < 0.05) with no change in LPS-stimulated PBMC or the intestinal mucosa transcriptome. LEfSe indicated increases in Lachnospiraceae, Ruminococcaceae within the order Clostridiales with a shift in bacterial carbohydrate metabolism and biosynthesis of secondary metabolites in the mushroom-fed pigs. These results suggested that feeding WB mushrooms significantly reduced the LPS-induced inflammatory response in AM and positively modulated the host microbiota metabolism by increasing the abundance of Clostridiales taxa that are associated with improved intestinal health.

The expression of NKG2D on porcine IEL and its possible relation to the adaptive intestinal immune system

The gastrointestinal tract contains a multitude of components which include intraepithelial lymphocytes (IEL). IELs have been reported to express a variety of surface receptors that enable cross talk among various cell populations. The purpose of the reported investigation was to determine which IEL populations express the natural killer cell receptor NKG2D which is an activating receptor that plays a role in cytolytic responses. In a feeding experiment with piglets, IELs were isolated from jejunal tissue at three different stages post weaning. The time dependent development of different cell populations was evaluated and an elevated number of lymphocytes (CD45+) shortly after weaning was observed compared to later time points. The number of T cells (CD3), including cytotoxic T cells (CD8β/CD16-), appeared to be particularly affected by the weaning period. Correlation analysis revealed an association between the NKG2D expression in jejunal tissue and the frequency of lymphocytes, esp. CD8β+ cytotoxic T cells. Gene expression analysis of NKG2D were performed on several isolated IEL populations and support the hypothesis that cytotoxic T cells (CD8β) in the porcine gut epithelium are capable of communicating with the surrounding enterocytes and inducing immune reactions via NKG2D. Unlike previous observations in porcine blood, the γδ T cells of the gut epithelium also showed expression of the stress factor binding NKG2D receptor. Subsequent analysis of the isolated IELs revealed that T cells appear to only express the receptor after isolation with an anti-CD3 mab, indicating that a previous stimulation of the TCR/CD3 complex may reinforce this signal transduction pathway.

Progress in the use of swine in developmental immunology of B and T lymphocytes

The adaptive immune system of higher vertebrates is believed to have evolved to counter the ability of pathogens to avoid expulsion because their high rate of germline mutations. Vertebrates developed this adaptive immune response through the evolution of lymphocytes capable of somatic generation of a diverse repertoire of their antigenic receptors without the need to increase the frequency of germline mutation. The focus of our research and this article is on the ontogenetic development of the lymphocytes, and the repertoires they generate in swine. Several features are discussed including (a) the "closed" porcine placenta means that de novo fetal development can be studied for 114 days without passive influence from the mother, (b) newborn piglets are precocial permitting them to be reared without their mothers in germ-free isolators, (c) swine are members of the γδ-high group of mammals and thus provides a greater opportunity to characterize the role of γδ T cells and (d) because swine have a simplified variable heavy and light chain genome they offer a convenient system to study antibody repertoire development.

Influence of medium-chain fatty acids and short-chain organic acids on jejunal morphology and intra-epithelial immune cells in weaned piglets

Medium-chain fatty acids (MCFA) and short-chain organic acids (SOA) are often used as feed additives in piglet diets. There are limited studies in pigs describing the impact of MCFA or SOA on gut morphology and the local immune system. The aim of this study was to investigate whether the supplementation of SOA (0.41% fumaric acid and 0.32% lactic acid), or the combination of SOA with MCFA (0.15% caprylic and capric acid) would have effects on gut morphology and intestinal immune cells in weaned piglets. A total number of 72 weaned piglets were randomly allocated into three experimental groups. Tissue samples of six animals per group were used to investigate the potential impact of the feed additives on villus length and crypt depth of the jejunum and to quantify intra-epithelial lymphocytes (IEL). CD3-positive IEL were determined via immunohistochemistry (IHC) and flow cytometry (FC), whereas CD2-, CD5-, CD8β-, CD16- and γδ TCR-positive IEL were only analysed by FC. The supplementation of MCFA and SOA did not significantly affect morphometric data. The FC data indicated that SOA significantly increased the quantity of CD2^- CD8^- γδ T cells in the jejunum epithelium. Both IHC and FC analyses of pig jejunum confirmed that the majority of IEL expressed the surface marker CD3 and could be classified as cytotoxic T lymphocytes. In conclusion, the data indicated that SOA increased the proportion of CD2^- CD8^- γδ T cells in the jejunal epithelium. Thus, SOA might enable a beneficial effect on the local immunity by increasing the constitutive number of potential effector cells to defeat infectious diseases.

Safety of Bifidobacterium animalis subsp. lactis (B. lactis) strain BB-12-supplemented yogurt in healthy adults on antibiotics: a phase I safety study

Probiotics are live microorganisms that, when administered in sufficient doses, provide health benefits on the host. The United States Food and Drug Administration (FDA) requires phase I safety studies for probiotics when the intended use of the product is as a drug. The purpose of the study was to determine the safety of Bifidobacterium animalis subsp lactis (B. lactis) strain BB-12 (BB-12)-supplemented yogurt when consumed by a generally healthy group of adults who were prescribed a 10-day course of antibiotics for a respiratory infection. Secondary aims were to assess the ability of BB-12 to affect the expression of whole blood immune markers associated with cell activation and inflammatory response. A phase I, double-blinded, randomized controlled study was conducted in compliance with FDA guidelines for an Investigational New Drug (IND). Forty participants were randomly assigned to consume 4 ounces of either BB-12 -supplemented yogurt or non-supplemented control yogurt daily for 10 d. The primary outcome was to assess safety and tolerability, assessed by the number of reported adverse events. A total of 165 non-serious adverse events were reported, with no differences between the control and BB-12 groups. When compared to the control group, B lactis fecal levels were modestly higher in the BB-12-supplemented group. In a small subset of patients, changes in whole blood expression of genes associated with regulation and activation of immune cells were detected in the BB-12-supplemented group. BB-12-supplemented yogurt is safe and well tolerated when consumed by healthy adults concurrently taking antibiotics. This study will form the basis for future randomized clinical trials investigating the potential immunomodulatory effects of BB-12-supplemented yogurt in a variety of disease states.

Phenotypic maturation of porcine NK- and T-cell subsets

Detailed information concerning the development of the immune system in young pigs is still rudimental. In the present study, we analyzed changes in phenotype and absolute numbers of natural killer cells, γδ T cells, T helper cells, regulatory T cells and cytolytic T cells in the blood of pigs from birth to six months of age. For each lymphocyte subpopulation, a combination of lineage and differentiation markers was investigated by six-color flow cytometry. Major findings were: (i) absolute numbers of γδ T cells strongly increased from birth until 19-25 weeks of age, indicating an important role for these cells during adolescence; (ii) phenotype of T helper cells changed over time from CD8α(-)SLA-DR(-)CD27(+) towards CD8α(+)SLA-DR(+)CD27(-) but CD45RC(-) T helper cells were found immediately after birth, therefore questioning the role of this marker for the identification of T-helper memory cells; (iii) for cytolytic T cells, putative phenotypes for early effector (CD3(+)CD8αβ(+)perforin(+)CD27(dim)) and late effector or memory cells (CD3(+)CD8αβ(+)perforin(+)CD27(-)) could be identified.

Effect of maternally supplied n-3 and n-6 oils on the fatty acid composition and mononuclear immune cell distribution of lymphatic tissue from the gastrointestinal tract of suckling piglets

Fatty acids are essential for immune cell function. Maternal dietary fatty acid supply influences body fat composition of their offspring. As a first step to study immunonutritional interactions at an early age of pigs, four sows were fed a diet containing sunflower oil or oil from seal blubber during pregnancy and lactation. Corresponding piglets were sacrificed at three consecutive time points in the suckling period and their mesenteric lymph nodes and spleen were analysed by gas chromatography for levels of fatty acid. At the same time mononuclear cells of these organs and of the intestinal lymphoid tissue from the jejunum were isolated and subpopulations characterised by flow cytometry. Levels of fatty acids from the lymphatic organs of the piglets were significantly influenced by the maternal diet. The concentration of the fatty acids 20:5n-3, 22:5n-3 and 22:6n-3 were higher in the spleen and mesenteric lymph node of piglets suckled to sows of the test diet. Additionally, suckling time affected the levels of some long chain polyunsaturated fatty acids. Dietary effects were seen on some subpopulations including CD4-CD8alpha+ lymphocytes of the mesenteric lymph nodes and CD4+CD8alpha+ lymphocytes of the lamina propria, which were higher in the group fed seal blubber oil. The levels of CD21+ B-cells were higher in the group fed sunflower oil. The results indicate that the maternal diet and suckling time affect the fatty acid status of the investigated lymphatic tissues of piglets, but may have minor effects on the investigated lymphocyte subpopulations.

Innate defense regulator peptide synergizes with CpG ODN for enhanced innate intestinal immune responses in neonate piglets

The in vivo immunoadjuvant effects of the combination of CpG oligodeoxynucleotide (CpG ODN) and innate defense-regulator peptides (IDRs) have been studied in mice. However, little is known about the efficacy of these molecules in stimulating the innate intestinal immune system in neonatal piglets. In this study, we observed that intranasal (IN) administration of CpG-IDR (peptide HH2 (VQLRIRVAVIRA)) complex significantly increased intestinal mRNA expression of Th1 cytokines, CC chemokines and CXC chemokines when compared to HH2 and CpG ODN alone. Also an obvious cellular infiltration was observed in the intestine of CpG-HH2-treated neonatal piglets, which was associated with increased protection against Enterotoxigenic Escherichia coli (ETEC). Moreover, we showed that pro-inflammatory cytokine TNF-α was inhibited when CpG ODN combined with HH2. This was the first report that deciphered the role played by CpG-HH2 complex in the intestine of neonatal piglets. This work clearly demonstrated that efficiency of the IN route inducing intestinal responses in neonatal piglets might be taken into consideration for further vaccine development against neonatal intestinal diseases.

Glutamine supplementation improves intestinal barrier function in a weaned piglet model of Escherichia coli infection

The weaning period is associated with an increased prevalence of gastrointestinal infection in many species. Glutamine (Gln) has been shown to improve intestinal barrier function and immune function in both in vivo and in vitro models. The objective of the present study was to determine the effect of dietary Gln supplementation on intestinal barrier function and intestinal cytokines in a model of Escherichia coli infection. We randomised 21-d-old piglets (n 20) to nutritionally complete isonitrogenous diets with or without Gln (4·4 %, w/w) for 2 weeks. Intestinal loops were isolated from anaesthetised pigs and inoculated with either saline or one of the two E. coli (K88AC or K88 wild-type)-containing solutions. Intestinal tissue was studied for permeability, cytokine expression, fluid secretion and tight-junction protein expression. Animals receiving Gln supplementation had decreased potential difference (PD) and short-circuit current (I(sc)) in E. coli-inoculated intestinal loops (PD 0·628 (SEM 0·151) mV; I(sc) 13·0 (SEM 3·07) μA/cm(2)) compared with control-fed animals (PD 1·36 (SEM 0·227) mV; I(sc) 22·4 (SEM 2·24) μA/cm(2)). Intestinal tissue from control, but not from Gln-supplemented, animals responded to E. coli with a significant increase in mucosal cytokine mRNA (IL-1β, IL-6, transforming growth factor-β and IL-10). Tight-junction protein expression (claudin-1 and occludin) was reduced with exposure to E. coli in control-fed animals and was not influenced in Gln-supplemented piglets. Gln supplementation may be useful in reducing the severity of weaning-related gastrointestinal infections, by reducing the mucosal cytokine response and altering intestinal barrier function.

The influence of age and maternal antibodies on the postvaccinal response against swine influenza viruses in pigs

The influence of age and maternal immunity on the development and duration of postvaccinal humoral response against swine influenza viruses (SIV) were investigated under experimental conditions. Piglets born to immune and non-immune sows were vaccinated twice with bivalent inactivated vaccine. Vaccination was done according to 5 different schedules: 1+4, 1+8, 4+8, 8+10 or 8+12 weeks of age. Antibodies to the haemagglutinin type 1 and 3 were determined using the haemagglutination inhibition (HI) test. Maternally derived antibodies (MDA) against H1N1 and H3N2 in the serum of unvaccinated piglets born to immune sows were above the positive level until about 13-14 and 9-10 weeks of life, respectively. No serological responses were seen in any of the groups after the first vaccination. After the second dose of vaccine production of antibodies was observed even before the complete disappearance of maternal antibodies. MDA, however, were associated with reduced antibody response. In MDA-negative piglets, an active humoral postvaccinal response was developed in all vaccinated pigs. The age at which the vaccine was given was associated with the differences in the magnitude of antibody response to SIV. In general those pigs that were vaccinated for the first time at the age of 1 week, developed lower maximum titres after the second vaccination, and become seronegative earlier than pigs that were vaccinated for the first time at 4 or 8 weeks of age.

Synthetic innate defence regulator peptide enhances in vivo immunostimulatory effects of CpG-ODN in newborn piglets

The in vivo immunoadjuvant effects of CpG oligodeoxynucleotides (CpG-ODN) have been studied extensively in mice and relatively fewer studies have been done in piglets. But so far, the innate immunostimulatory effects of CpG-ODN combination with innate defense-regulator peptides (IDRs) have not been demonstrated. The purpose of this study is to determine the potential effects of CpG-ODN with IDR in newborn piglets. The immunostimulatory abilities of four selected IDRs were compared, among them HH2 showed best immunostimulatory effects in newborn piglets. Hereafter, the abilities of CpG-ODN combined with HH2 to enhance innate immune responses were examined in newborn piglets. The complex of HH2 and CpG-ODN could induce much stronger Th1 cytokine and chemokine responses than HH2 or CpG-ODN alone. HH2-CpG-ODN immunized piglets showed higher B cell percentage in PBMCs than CpG-ODN alone. These in vivo data demonstrated for the first time that subcutaneously (SC) administration of CpG-ODN combined with HH2 is efficient to stimulate innate immune system in newborn piglets.

Changes in lymphocyte populations in suckling piglets during primary infections with Isospora suis

Isospora suis, a common intestinal parasite of piglets, causes neonatal porcine coccidiosis, which results in reduced and uneven weaning weights and economic losses in pig production. Nevertheless, there are no detailed studies available on the immune response to I. suis. The aim of this study was to carry out phenotypical characterization of lymphocytes during primary infections on day 3 after birth. Infected and noninfected piglets were investigated between days 7 and 16 after birth. Lymphocytes from the blood, spleen and mesenteric lymph nodes (flow cytometry) and of the jejunal mucosa (immunohistochemistry) were analysed. A decrease in T cells, especially with the phenotype of resting T-helper cells, T-cell receptor-gammadelta-T cells, and regulatory T cells in the blood, spleen and mesenteric lymph nodes was noticeable. An increase in cells with the phenotype of natural killer cells in the spleen of infected animals was found, and the subset of TcR-gammadelta-T cells was strongly increased in the gut mucosa. Our findings suggest an accelerated migration of those cells into the gut. This study provides a strong indication for the involvement of adaptive and innate immune response mechanisms in the primary immune response to I. suis, especially of TcR-gammadelta-T cells as a linkage between innate and adaptive immunity.

Membrane markers of the immune cells in swine: an update

Besides their breeding value, swine are increasingly used as biomedical models. As reported in three international swine clusters of differentiation (CD) workshops and in the animal homologue section of the last workshop for the determination of human leukocyte differentiation antigens (HLDA 8), characterisation of leukocyte surface antigens by monoclonal antibodies and other molecular studies have determined the cell lineages and blood leukocyte subsets implicated in the immune response, including cell adhesion molecules involved in cell trafficking. This review focusses on the current state of knowledge of porcine leukocyte differentiation and major histocompatibility complex (SLA) molecules. Examples of porcine particularities such as the double-positive T lymphocytes with the phenotype CD(4+)CD8(low) and CD(4-)CD8(low) alphabeta T cell subsets and the persistence of SLA class II after T-lymphocyte activation are illustrated, as well as the shared characteristics of the Artiodactyla group, such as the high proportion of gammadelta TcR (T cell receptor) T cells in blood and other lymphoid tissues. Furthermore, discrepancies between swine and humans, such as CD16 expression on dendritic cells and CD11b (wCD11R1) tissue distribution are outlined. The rapidly growing information should facilitate manipulation of the swine immune system towards improving disease control, and open new avenues for biomedical research using the pig as a model.

Cross-reactive anti-human monoclonal antibodies as a tool for B-cell identification in dogs and pigs

We have characterized a panel of commercially available anti-human monoclonal antibodies (mAbs) suitable for B-cell identification in pigs and dogs. The specificities of the mAbs were against CD20, CD21, CD22, and CD86. In addition to HM57, originally raised against human CD79alpha the broad cross-reactivity of which was documented more than 10 years ago, we recommend here a panel of several other mAbs as a useful tool for immunophenotyping and multicolor flow cytometry of canine and porcine B-lymphocytes. All six investigated antibodies did bind weakly to either canine or porcine lymphocytes (or both), but considerable weaker than for the human control cells. Four of them did bind to canine or porcine spleen section in immunohistochemistry. Monoclonal antibody against CD22 (clone RFB-4) was the only antibody in the tested panel the cross-reactivity of which was confirmed by Western blot. The advantages and limits of cross-reactive mAbs in studies on animal B-cells are discussed.

Diet regulates the development of gut-associated lymphoid tissue in neonatal piglets

BACKGROUND

Controversy exists concerning diet-induced changes to gut epithelia and immunocytes that occur during weaning. Furthermore, studies on dietary effects on the development of the neonatal immune system, especially gut-associated lymphoid tissue (GALT), are lacking.

OBJECTIVE

The purpose of this study was to investigate growth and development, intestinal morphology, and GALT immune maturation in sow-reared littermates in comparison with early-weaned piglets fed a casein-based liquid diet.

METHOD

Piglets were breast fed by the sow or were weaned at 48 h to a casein-based diet (formula) that provided the amount of nutrient requirements recommended by the National Research Council.

RESULTS

Gross physical appearance and visual inspection of the gastrointestinal tract and other organs at necropsy revealed normal organogenesis in both cohorts. On postnatal day 21, body weight, liver and kidney weight relative to body weight, small intestine length, and weight-to-length ratio were greater in formula-fed piglets as compared with sow-reared piglets (p<0.05). The CD21+ B lymphocyte component of GALT and spleen was reduced in the formula-fed piglets. This was associated with lower circulating IgG and IgM levels in the formula-fed as compared with the breast-fed neonatal piglets (p<0.001).

CONCLUSIONS

Feeding a casein-based formula to newborn piglets may compromise the development of GALT and systemic immune system. Further, the neonatal piglet model may be used to identify the effects of dietary factors on the development of the neonatal immune system.

Effect of Vitamin E Supplementation on Lymphocyte Distribution in Gut-Associated Lymphoid Tissues Obtained from Weaned Piglets

Fifteen piglets were used to determine the effect of vitamin E supplementation on the number of CD4-immunoreactive (CD4+) T-lymphocytes, CD8-immunoreactive (CD8+) T-lymphocytes and IgA-immunoreactive (IgA+) B-lymphocytes per follicle in the Peyer's patch of distal ileum and the mesenteric lymph nodes of weaned piglets. Piglets, following a 3-day adaptation period after weaning, were assigned to one of three experimental groups: control (no vitamin E supplementation), vitamin E supplementation of 100 mg/kg of diet and vitamin E supplementation of 300 mg/kg of diet. Supplementation of vitamin E lasted for a period of 36 days. The basal diet contained 80 mg alpha-tocopherol/kg of diet. All piglets were killed at day 39 after weaning and samples of the distal ileum and adjacent mesenteric lymph nodes were collected. The number of cells for each lymphocyte subset was counted in the Peyer's patch and the mesenteric lymph nodes follicles, in cryostat sections processed for immunohistochemistry. Results showed that vitamin E supplementation (300 mg/kg diet) of piglets caused an increase (P < 0.05) in the number of IgA+ B-lymphocytes in the Peyer's patch, but not in the mesenteric lymph nodes, compared with the corresponding values in control animals. Vitamin E supplementation had no effect (P > 0.05) on the number of CD4+ and CD8+ T-lymphocytes in the follicles of the Peyer's patch and the adjacent mesenteric lymph nodes. Thus, vitamin E had relatively minor effects on distribution of the major immunocompetent cells in the gut. The numbers of CD4+ and CD8+ T-lymphocytes as well as IgA+ B-lymphocytes per follicle were higher by 26-77% (P < 0.05) in the mesenteric lymph nodes than the corresponding values in the Peyer's patch.

Relationship Between Immune Cell Phenotypes and Pig Growth in a Commercial Farm

The objective of this study was to evaluate the relationship between the level and function of circulating immune cells with average daily gain, live and carcass measurements, feed intake, and feed conversion. Production performance was monitored throughout the pig's lifetime. Pigs were moved in weekly batches through the nursery and growing/finishing rooms at specific target weights. Animals were individually weighed at birth and at weaning, and then every two weeks while they were "on test" until they were "off test" and sent to the slaughterhouse. At six to seven weeks of age, the pigs were bled in the nursery. The percentage of immune cell subsets and lymphocyte proliferation was estimated using swine monoclonal antibodies and flow cytometric analysis. The predictive effect of the immune cell subset markers and lymphocyte proliferation on production traits was statistically analyzed. The results indicated that the proportion of several peripheral cell subsets, including CD16+, CD2+/CD16+, and CD8+ lymphocytes, appear to predict growth during the entire productive life of the pig. Larger percentages of lymphocytes expressing CD16+ CD2+/CD16+, and CD8+receptors in blood resulted in a reduction in average daily gain. In addition, high percentages of SLA-DQ+ cells were associated with better carcass weight and feed conversion. The CD16+, CD2+/CD16+, CD8+, and SLA-DQ+/- cell subsets appear to be important biomarkers involved with the inherent ability of the pig to efficiently grow and produce better carcass weight in representative commercial environments.

The influence of different management systems and age on intestinal morphology, immune cell numbers and mucin production from goblet cells in post-weaning pigs

At time of weaning, the immune system in piglets is not fully mature resulting in reduced growth and increased mortality. Early-weaned pigs transported to a segregated early weaning (SEW) facility have enhanced performance and gut development compared to conventional (CONV) pigs which may be due, in part, to decreased pathogen challenge. To gain further insight into SEW enhanced performance and gut development, gut samples from pigs weaned at 19+/-2 days were assessed during the post-weaning (PW) period. The numbers of cells expressing CD2, CD4, CD8, and CD172 (the 74-22-15 (SWC3) antibody is now known to be specific for CD172), MHC class II, and CD25 were quantified using immunohistochemistry. Additionally, samples of duodenum, jejunum, and ileum were evaluated for the production of neutral, acidic, and sulfuric mucins from goblet cells and morphological measurements were also made. No effects due to the management systems alone were observed for any of the parameters. However, there were interactive effects of age/time post-weaning and management system on the immune cells as well as on the mucin secreting goblet cells. There were no differences in gut morphology between SEW and CONV reared pigs.

Peripheral T lymphocyte changes in neonatal piglets: Relationship with growth hormone (GH), prolactin (PRL) and cortisol changes

Taking into account the role played by the neuroendocrine network in affecting the early development of the immune response, the present study aims to assess neonatal immunity in piglets by testing peripheral lymphocyte age-related changes in relationship to plasma levels of some relevant immunoregulatory hormones, such as growth hormone (GH), prolactin (PRL) and cortisol. For this purpose, we studied the peripheral lymphocyte age-related changes in relationship to plasma levels of GH, PRL and cortisol in conventional piglets from birth (day 0) to 41 days of age. A significant decrease was observed in the total number of lymphocytes at day 0, with a subsequent constant increment up to 41 days of age. Concomitantly, the number of T cell subsets (mainly CD8(+) cells and double positive CD4(+)CD8(+)) was low at birth, with strong increments between the 19th and 41st days of life. The CD4(+) T cell number subset was less diminished at birth than that of CD8(+), albeit with significant increments in the post-weaning period. Of interest, gammadelta T cells, which are more involved in innate immune efficiency, displayed the same trend as CD8(+) T cells from birth to the 41st day of life. From day 0 up to the 19th day, significant inverse correlations were found between T cell subsets and GH or PRL or cortisol, albeit with more significant inverse correlations with cortisol. The high levels of GH and PRL in the pre-weaning period may be due to the fact that they have to counteract the cortisol-mediated negative effect on lymphocyte production and development. These findings suggest that stress condition occurs at birth with decreases in the immune parameters, in the same way as in human newborns, with a subsequent gradual normalisation and immune development, as shown by decreased cortisol, GH and PRL normalisation and concomitant increments in T cell subsets.

Intestinal double-positive CD4+CD8+ T cells are highly activated memory cells with an increased capacity to produce cytokines

Peripheral blood and intestinal CD4+CD8+ double-positive (DP) T cells have been described in several species including humans, but their function and immunophenotypic characteristics are still not clearly understood. Here we demonstrate that DP T cells are abundant in the intestinal lamina propria of normal rhesus macaques (Macaca mulatta). Moreover, DP T cells have a memory phenotype and are capable of producing different and/or higher levels of cytokines and chemokines in response to mitogen stimulation compared to CD4+ single-positive T cells. Intestinal DP T cells are also highly activated and have higher expression of CCR5, which makes them preferred targets for simian immunodeficiency virus/HIV infection. Increased levels of CD69, CD25 and HLA-DR, and lower CD62L expression were found on intestinal DP T cells populations compared to CD4+ single-positive T cells. Collectively, these findings demonstrate that intestinal and peripheral blood DP T cells are effector cells and may be important in regulating immune responses, which distinguishes them from the immature DP cells found in the thymus. Finally, these intestinal DP T cells may be important target cells for HIV infection and replication due to their activation, memory phenotype and high expression of CCR5.

Glutamine supplementation influences immune development in the newly weaned piglet

A study was conducted to determine changes that occur in immune function during the early post-weaning period and the effect of supplementing glutamine (gln, 4% w/w) to the weaning diet of piglets. Dutch-Landrace piglets (n=10/group) were killed prior to weaning (21 d) or randomized to one of two nutritionally complete weaning diets with or without gln. With age there was an increased ability of peripheral blood mononuclear cells (PBMC) and mesenteric lymph nodes (MLN) cells to proliferate (rate of (3)H-thymidine uptake) to T cell mitogens (P<0.05). PBMC from older piglets produced less of a Th-1 type response after stimulation (P<0.05). Adding gln to the weaning diet significantly (P<0.05) modified immune cells in the MLN, in a potentially beneficial manner (with respect to mucosal infections) by preventing an increase in antigen naïve CD4+ cells, increasing the proliferative response to pokeweed mitogen and supporting a Th-1 type cytokine response after T cell (phytohemagglutinin) stimulation.

Levamisole mucosal adjuvant activity for a live attenuated Escherichia coli oral vaccine in weaned pigs

The present study tested the hypothesis that levamisole exerts its immunopotentiating activity in weaned pigs vaccinated against colibacillosis by priming the lymphocytes and macrophages in the mesenteric lymph node (MLN). Ten weaned piglets were used and allocated into two equal groups. The experimental group was intramuscularly primed with levamisole at an immunostimulatory dose of 2.5 mg/kg given daily, in three consecutive days, and controls received saline according to the same schedule. Both groups were orally vaccinated with the vaccinal Escherichia coli strain on day 0 and challenged with the virulent E. coli strain 7 days later. All pigs were killed on postchallenge day 6. Upon virulent challenge the health status of the two groups was evaluated by clinical observations, and expression of CD25, SWC7 and SWC9 activation antigens by MLN and spleen T and B cells and macrophages, respectively, was tested using flow cytometry. Priming by levamisole significantly contributed to the effectiveness of a live attenuated oral vaccine against porcine postweaning colibacillosis, as evidenced by a good health status of primed vaccinated vs. un-primed vaccinated pigs. The CD3+, CD25+ and SWC9+ MLN but not spleen T cells and macrophages increased in experimental vs. control pigs, implying that levamisole exerts its potentiating activity in the MLN by augmenting both recruitment and activation of cells that participate in cell-mediated immunity.