The effect of recombinant swine interleukin-4 on swine immune cells and on pro-inflammatory cytokine productions in pigs

Differentiation and Regulation of Bovine Th2 Cells In Vitro

Bovine Th2 cells have usually been characterized by IL4 mRNA expression, but it is unclear whether their IL4 protein expression corresponds to transcription. We found that grass-fed healthy beef cattle, which had been regularly exposed to parasites on the grass, had a low frequency of IL4+ Th2 cells during flow cytometry, similar to animals grown in feedlots. To assess the distribution of IL4+ CD4+ T cells across tissues, samples from the blood, spleen, abomasal (draining), and inguinal lymph nodes were examined, which revealed limited IL4 protein detection in the CD4+ T cells across the examined tissues. To determine if bovine CD4+ T cells may develop into Th2 cells, naïve cells were stimulated with anti-bovine CD3 under a Th2 differentiation kit in vitro. The cells produced primarily IFNγ proteins, with only a small fraction (<10%) co-expressing IL4 proteins. Quantitative PCR confirmed elevated IFNγ transcription but no significant change in IL4 transcription. Surprisingly, GATA3, the master regulator of IL4, was highest in naïve CD4+ T cells but was considerably reduced following differentiation. To determine if the differentiated cells were true Th2 cells, an unbiased proteomic assay was carried out. The assay identified 4212 proteins, 422 of which were differently expressed compared to those in naïve cells. Based on these differential proteins, Th2-related upstream components were predicted, including CD3, CD28, IL4, and IL33, demonstrating typical Th2 differentiation. To boost IL4 expression, T cell receptor (TCR) stimulation strength was reduced by lowering anti-CD3 concentrations. Consequently, weak TCR stimulation essentially abolished Th2 expansion and survival. In addition, extra recombinant bovine IL4 (rbIL4) was added during Th2 differentiation, but, despite enhanced expansion, the IL4 level remained unaltered. These findings suggest that, while bovine CD4+ T cells can respond to Th2 differentiation stimuli, the bovine IL4 pathway is not regulated in the same way as in mice and humans. Furthermore, Ostertagia ostertagi (OO) extract, a gastrointestinal nematode in cattle, inhibited signaling via CD3, CD28, IL4, and TLRs/MYD88, indicating that external pathogens can influence bovine Th2 differentiation. In conclusion, though bovine CD4+ T cells can respond to IL4-driven differentiation, IL4 expression is not a defining feature of differentiated bovine Th2 cells.

Comparison of heterologous prime-boost immunization strategies with DNA and recombinant vaccinia virus co-expressing GP3 and GP5 of European type porcine reproductive and respiratory syndrome virus in pigs

Vaccination is principally used to control and treat porcine reproductive and respiratory syndrome virus (PRRSV) infection. This study investigated immunogenicity and protective efficacy of heterologous prime-boost regimens in pigs, including recombinant DNA and vaccinia virus vectors coexpressing PRRSV European genotype (EU) isolate GP3 and GP5: group A, pVAX1-EU-GP3-GP5 prime and rddVTT-EU-GP3-GP5 boost; group B, rddVTT-EU-GP3-GP5 prime and pVAX1-EU-GP3-GP5 boost; group C, empty vector pVAX1; group D, E3L gene-deleted vaccinia virus E3L- VTT. Vaccine efficacy was tested in an EU-type PRRSV (Lelystad virus strain) challenge pig model based on evaluating PRRSV-specific antibody responses, neutralizing antibodies, cytokines, T lymphocyte proliferation, CD4+ and CD8+ T lymphocytes, clinical symptoms, viremia and tissue virus loads. Plasmid DNA was delivered as chitosan-DNA nanoparticles, and Quil A (Quillaja) was used to increase vaccine efficiency. All piglets were boosted 21 days post the initial inoculation (dpi) and then challenged 14 days later. At 14, 21, 28 and 35 dpi, groups A and B developed significantly higher PRRSV-specific antibody responses compared with control groups C and D. Two weeks after the boost, significant differences in neutralizing antibody and IFN-γ levels were observed between groups A, C, D and B. At 49 dpi, groups A and B had markedly increased peripheral blood CD3+CD4+ T cell levels. Following virus challenge, group A showed viremia, but organ virus loads were lower than those in other groups. Thus, a heterologous prime-boost vaccine regimen (rddVTT-EU-GP3-GP5 prime, pVAX1-EU-GP3-GP5 boost) can improve humoral- and cell-mediated immune responses to provide resistance to EU-type PRRSV infection in vivo.

Phenotypic and functional modulations of porcine macrophages by interferons and interleukin-4

Considering that macrophage functions are strongly impacted by the local tissue environment and the type of immune response, the aim of this study was to carefully set the methodological baseline for phenotype and functions of polarized porcine monocyte-derived macrophages. To this end, macrophages were generated in autologous serum alone or with colony-stimulating factor (CSF)-1 or CSF-2, and subsequently polarized with interferon (IFN)γ, interleukin-4 or IFNβ. IFNγ promoted expression of MHC class I, MHC class II, CD11a, and CD40 as well as LPS-induced IL-6 and IL-12. A hallmark of interleukin-4 was Arginase 1 and CD203a upregulation, without abrogating pro-inflammatory cytokine production. IFNβ induced CD169, MHC class I, CD40, CD80/86, but suppressed IL-6, IL-12 and tumor-necrosis-factor secretion. CSF-2 alone altered macrophage differentiation and promoted an IFNγ-like polarization. Altogether, the results provide a comprehensive overview of porcine macrophage polarization, and demonstrate commonalities with other species as well as peculiarities of the pig.

Effects of interferon-α on the inflammatory response of swine peripheral blood mononuclear cells

Interferon-α (IFN-α) at low concentrations had been previously shown to control the expression of inflammatory cytokine genes in swine pulmonary alveolar macrophages. In the first part of this study, cultured swine peripheral blood mononuclear cells (PBMCs) were supplemented with IFN-α at low/moderate concentrations, and then stimulated with lipopolysaccharide (LPS). The expression of IFN-α, IFN-γ, IL-1β, TNF-α, and IL-6 genes was determined by real-time PCR. IFN-α at low/moderate concentrations did not significantly reduce the expression of any cytokine gene under study, with clear trends though to a concentration-dependent reduction of IL-1β gene expression and to a concentration-dependent increase of IFN-γ gene expression. In vivo, orally administered IFN-α was shown instead to modulate the inflammatory response to early weaning in uncultured PBMCs of specific pathogen-free piglets. As opposed to the in vitro model, the oral IFN-α treatment reduced after weaning the expression of the IFN-γ gene (P < 0.08) and increased that of the IL-1β gene (P < 0.05). There was also a trend to a reduced expression of both IL-6 and TNF-α. The above modulation of cytokine genes expression and the greater daily mean weight gain of treated piglets highlight important regulatory properties of oral IFN-α in the response to the weaning stress.

Effect of dietary addition of seaweed and licorice on the immune performance of pigs

In pig production, dietary additive antibiotics are usually used for growth stimulation and disease prevention, although there is public concern about the increased incidence of resistant antibiotics and food safety. It is possible that such antibiotics might be replaced by naturally derived products such as seaweed and licorice. In this study, we evaluated the effect of dietary addition of seaweed and licorice on enhancing the immune function in swine. The animals of each group (eight animals per group) were sensitized at day 42 and 49, and the immunoglobulin production and the expression of cytokines were detected by the ELISA and real-time PCR. As the results, saliva IgA production of the seaweed-treated group increased around five times compared to that of control (day 56). Delayed hypersensitivity reaction and IgG production of the seaweed-treated group increased around 1.8-2.0 times. In addition, enhanced saliva IgA production was detected at day 50 (around two times) and day 51 (around five times) by the licorice treatment, and lower expression level of tumor necrosis factor-α messenger RNA at day 51 (around 1/25) was observed in the licorice treatment. We conclude that the replacement of antibiotics by naturally derived dietary additives might be feasible for immune system enhancement.

Species specialization in cytokine biology: is interleukin-4 central to the T(H)1-T(H)2 paradigm in swine?

The TH1-TH2 paradigm provides an elegant model of directed response to infectious pathogens. Developed in the mouse, the model has provided a framework for systematic and mechanistic studies of immune regulation, protective immunity, and vaccine development in swine. Interleukin-4 (IL-4) plays a central role in the paradigm as a regulatory molecule directing development of the TH2 phenotype, as a developmental cytokine essential for antibody production, and as a soluble diagnostic marker of the TH2 cell type. In contrast, while characterizing the biological properties of porcine IL-4, we discovered that it was not a stimulatory factor for porcine B cells. Rather, it blocked antibody and IL-6 secretion and suppressed antigen-stimulated proliferation of B cells. Inhibition was not reversed by treatment with IL-2 and IL-6 treatment. IL-4 did not stimulate T lymphocyte proliferation, but induced cell growth in lymphoblasts in a dose-dependent fashion. These results suggest that IL-4 plays a different role in pigs than in mice and humans, in which it stimulates B cells and is essential for antibody production. Furthermore, the functions of IL-4 in swine cannot be inferred from results in model systems such as the mouse. General models of disease resistance show substantial variation between pigs and mice at the cellular and molecular level. Advances in somatic cell technologies and animal engineering to enable gene knockouts in pigs, in combination with a continuously expanding immunological toolkit, promise an exciting future for pig immunology, detailed mechanistic elucidation of the TH1-TH2 paradigm, and an improved understanding of the role of IL-4 in porcine immunity to infectious disease.

Cytokine expression in colostrum-deprived pigs immunized and challenged with Haemophilus parasuis

The expression of several cytokines in spleen, pharyngeal lymph nodes, lung and brain after different immunization procedures and a challenge with 5 x 10(9) CFU of Haemophilus parasuis was compared. Five groups of colostrum-deprived pigs were used: vaccinated with (I) a bacterin, (II) an outer-membrane-protein-vaccine, (III) a recombinant transferring-binding protein B, (IV) exposed to a total dose of 10(5) CFU, and (V) not previously immunized. All pigs in groups III and V died, while all animals in group I, most of group IV and half of group II survived until the end of the experiment. IL-1alpha was found in significantly higher levels (p<0.05) in spleen, lymph nodes and brain of dead pigs, which could be explained by the major severity of lesions in these animals. However, IL-4, IL-10, TNF-alpha and IFN-gamma were expressed in significantly higher levels by survivors (for all the four cytokines in lymph nodes; for IL-4, IL-10 and TNF-alpha in spleen; for IL-4, TNF-alpha and IFN-gamma in lung, and only for TNF-alpha in brain), thus suggesting a role of these four cytokines in the adaptive response, which might contribute to protection against H. parasuis infection.

Adjuvants for porcine reproductive and respiratory syndrome virus vaccines

This review deals with present and past efforts in utilization of vaccine adjuvants for porcine reproductive and respiratory syndrome virus (PRRSV) vaccines. PRRSV vaccines elicit delayed and weak cell-mediated immune (CMI) and antibody responses after vaccination. Several kinds of vaccine adjuvants have been utilized to accelerate and magnify immune responses to PRRSV vaccines. These adjuvants include cytokines, chemical reagents, and bacterial products. Of 11 vaccine adjuvants tested, five (i.e. interleukin-2 (IL-2), IL-12, interferon alpha (IFNalpha), polyinosinic and polycytidylic acid, and cytidine-phosphate-guanosine oligodeoxynucleotides (CpG ODN)) significantly enhance CMI response to PRRSV vaccines. The response is characterized by proliferation, cytotoxicity, and IFNgamma secretion of peripheral blood mononuclear cells or T cells in response to recall PRRSV antigens in vitro. Two (i.e. CpG ODN and cholera toxin) significantly enhance PRRSV-specific antibody response after vaccination. Two (i.e. IL-2 and CpG ODN) significantly enhance protective efficacy of PRRSV vaccines in challenge models. Improvement of immune responses to PRRSV vaccines should focus in future studies on assessing more vaccine adjuvants for their efficiency in enhancing both CMI and antibody responses and on identifying PRRSV components and strategies that down-modulate pig immune responses in order to devise vaccine adjuvants that can regulate such strategies of the virus.

Transfer of maternal cytokines to suckling piglets: in vivo and in vitro models with implications for immunomodulation of neonatal immunity

Maternal cytokines may play instructive roles in development of the neonatal immune system. However, cytokines in colostrum and milk and their transfer from mothers to neonates have not been well documented, except for TGF-beta. Swine provide a unique model to study lactogenic cytokines because the sow's impermeable placenta prohibits transplacental passage. We investigated IL-6 and TNF-alpha (pro-inflammatory), IFN-gamma and IL-12 (Th1), IL-10 and IL-4 (Th2) and TGF-beta1 (Th3) concentrations in sow serum and colostrum/milk and serum of their suckling and weaned piglets and in age-matched colostrum-deprived gnotobiotic piglets. All cytokines were detected in colostrum/milk and correlated with concentrations in sow serum except for mammary-derived TNF-alpha and TGF-beta1. Detection of IL-12 and TGF-beta1 in pre-suckling and colostrum-deprived gnotobiotic piglet serum suggests constitutive production: other cytokines were undetectable confirming absence of transplacental transfer. Peak median cytokine concentrations in suckling piglet serum occurred at post-partum days 1-2 (IL-4>IL-6>IFN-gamma>IL-10). The effects in vitro of physiologically relevant concentrations of the two predominant lactogenic cytokines (TGF-beta1 and IL-4) on porcine naive B cell responses to lipopolysaccharide (LPS) and rotavirus (RV) were investigated. High (10 ng/ml) TGF-beta1 suppressed immunoglobulin secreting cell responses to LPS and rotavirus; low concentrations (0.1 ng/ml) promoted isotype switching to IgA antibody. Interleukin-4 induced inverse dose-dependent (0.1 ng>10 ng/ml) isotype switching to IgA and enhanced IgM secreting cell responses to LPS and rotavirus. In summary, we documented the transfer and persistence of maternal cytokines from colostrum/milk to neonates and their potential role in Th-2 biased IgA responses and reduced immunologic responsiveness of neonates.

In vitro down regulation of proinflammatory cytokines induced by LPS tolerance in pig CD14+ cells

LPS tolerance is characterized by a reduced sensitivity to subsequent challenge of LPS. In human and mouse models LPS tolerance is closely associated with marked unbalanced production of leukocyte-derived inflammatory mediators which, when overexpressed, led to septic syndrome and shock. Here we characterized the in vitro induction of LPS tolerance in porcine CD14+ spleen cells in order to give insights into LPS tolerance in pigs. Following LPS stimulation, TNF-alpha and, to a minor extent, IL-8 production showed a significant reduction in CD14+ spleen monocytes that were pretreated with LPS in comparison to naïve cells, while IL-1beta production was slightly influenced by LPS stimulation and it was not affected by subsequent LPS challenge. Our findings showed that porcine CD14+ cells undergo a process, which resembles LPS tolerance, providing evidence that swine represent a valuable and useful model to perform experiments to study LPS tolerance and its biological significance.