γδ T-lymphocyte cytotoxic activity against Mycobacterium bovis analyzed by flow cytometry

Porcine γδ T cells express cytotoxic cell-associated markers and display killing activity but are not selectively cytotoxic against PRRSV- or swIAV-infected macrophages

Background

Gamma-delta (γδ) T cells are a major immune cell subset in pigs. Approximately 50% of circulating T cells are γδ T cells in young pigs and up to 30% in adult sows. Despite this abundance, the functions of porcine γδ T cells are mostly unidentified. In humans and mice, activated γδ T cells exhibit broad innate cytotoxic activity against a wide variety of stressed, infected, and cancerous cells through death receptor/ligand-dependent and perforin/granzyme-dependent pathways. However, so far, it is unknown whether porcine γδ T cells have the ability to perform cytotoxic functions.

Methods

In this study, we conducted a comprehensive phenotypic characterization of porcine γδ T cells isolated from blood, lung, and nasal mucosa. To further analyze the cytolytic potential of γδ T cells, in vitro cytotoxicity assays were performed using purified γδ T cells as effector cells and virus-exposed or mock-treated primary porcine alveolar macrophages as target cells.

Results

Our results show that only CD2+ γδ T cells express cytotoxic markers (CD16, NKp46, perforin) with higher perforin and NKp46 expression in γδ T cells isolated from lung and nasal mucosa. Moreover, we found that γδ T cells can exhibit cytotoxic functions in a cell-cell contact and degranulation-dependent manner. However, porcine γδ T cells did not seem to specifically target Porcine Reproductive and Respiratory Syndrome Virus or swine Influenza A Virus-infected macrophages, which may be due to viral escape mechanisms.

Conclusion

Porcine γδ T cells express cytotoxic markers and can exhibit cytotoxic activity in vitro. The specific mechanisms by which porcine γδ T cells recognize target cells are not fully understood but may involve the detection of cellular stress signals.

Immunogenicity of Bacillus Calmette-Guérin in pigs: potential as a translational model of non-specific effects of BCG

Background

Clinical and immunological studies in humans show that the live attenuated Bacillus Calmette-Guérin (BCG) vaccine has beneficial non-specific effects, increasing resistance against diseases other than tuberculosis. The underlying mechanisms are currently being explored. The pig exhibits considerable physiological similarity to humans in anatomy and physiology, suggesting that similar responses to BCG could be expected. Studies of the non-specific effects of BCG in pigs are scarce. We investigated the feasibility of using pigs as a large animal model to investigate the non-specific immunological effects of BCG.

Methods

In a series of experiments, we randomized newborn or young piglets from conventional farms to receiving BCG or placebo and investigated the persistence of live BCG bacteria in various tissues, the immunogenicity of BCG in ex vivo blood and in vitro stimulation assays, and the acute phase protein and clinical responses to heterologous infectious challenge with influenza A virus or Actinobacillus pleuropneumoniae.

Results

The BCG vaccine was generally well tolerated. In contrast to humans, no skin reaction in the form of abscesses, ulcers, or scars was observed. Live BCG was recovered from draining lymph nodes in 2/13 animals 20 weeks after vaccination. Specific in vitro responses of IFN-γ to antigen-specific re-stimulation with mycobacterial antigen were increased but not TNF-responses to TLR2 or TLR4 agonists. A few genes were differentially expressed in blood after vaccination, including the antiviral genes RIG-I and CSF1, although the effect disappeared after correction for multiple testing. Clinical symptoms after heterologous bacterial or viral respiratory infections did not differ, nor did virus copies in nasopharyngeal samples after the challenge. However, the acute phase protein response was significantly reduced in BCG-vaccinated animals after influenza challenge but not after A. pleuropneumoniae challenge.

Discussion

BCG was safe in pigs, inducing specific immunological responses, but our model did not corroborate the innate immunological responsiveness to BCG seen in humans. The dose of BCG or the bacterial and viral challenges may have been sub-optimal. Even so, the acute phase protein response to influenza infection was significantly reduced in BCG-vaccinated animals.

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.

Effects of immunostimulators of microbial origin on T cells of pigs vaccinated with attenuated vaccine against Aujeszky's disease

Aujeszky's disease (AD) is a viral infectious disease caused by Suid herpesvirus 1 (SuHV-1). Vaccination and eradication of AD in domestic pigs is possible using marker vaccines with attenuated or inactivated SuHV-1, or subunit vaccines. However, vaccines with attenuated SuHV-1 have shown to be more potent in inducing strong cell-mediated immune response. The studies have shown that Parapoxvirus ovis, as well as Propionibacterium granulosum with lipopolysacharides (LPS) of Escherichia coli have pronounced immunomodulatory effects and that in combination with the vaccines can induce stronger humoral and cellular immune responses than use of vaccines alone. In our study distribution of peripheral blood T cell subpopulations was analysed after administration of vaccine alone (attenuated SuHV-1), immunostimulators (inactivated Parapoxvirus ovis or combination of an inactivated P. granulosum and detoxified LPS of E. coli) and combinations of vaccine with each immunostimulator to the 12-week old piglets. Throughout the study no significant changes were found in the proportions of γδ and most αβ T cell subpopulations analysed. However, on the seventh day of the study combination of an inactivated P. granulosum and LPS of E. coli with vaccine induced transient but significant increase of the proportions of CD4⁺CD8α⁺ and CD4^-CD8α⁺ αβ T cells, that have been strongly associated with early protection of SuHV-1 infected pigs. Our findings indicate that combination of inactivated P. granulosum and detoxified E. coli LPS could be used for enhancement of a cellular immune response induced by vaccines against AD.

Gamma Delta T Cell Function in Ruminants

Gamma delta (γδ) T cells constitute a major lymphocyte population in peripheral blood and epithelial surfaces. They play nonredundant roles in host defense against diverse pathogens. Although γδ T cells share functional features with other cells of the immune system, their distinct methods of antigen recognition, rapid response, and tissue tropism make them a unique effector population. This review considers the current state of our knowledge on γδ T cell biology in ruminants and the important roles played by this nonconventional T cell population in protection against several infectious diseases of veterinary and zoonotic importance.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (second edition)

These guidelines are a consensus work of a considerable number of members of the immunology and flow cytometry community. They provide the theory and key practical aspects of flow cytometry enabling immunologists to avoid the common errors that often undermine immunological data. Notably, there are comprehensive sections of all major immune cell types with helpful Tables detailing phenotypes in murine and human cells. The latest flow cytometry techniques and applications are also described, featuring examples of the data that can be generated and, importantly, how the data can be analysed. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid, all written and peer-reviewed by leading experts in the field, making this an essential research companion.

Shifts in porcine PBMC populations from adolescence to adulthood

In mammals, the immune system is undergoing significant changes during development, which has many impacts on the individual's capacity to cope with infectious diseases or other pathologic conditions, where the immune system is involved. Especially in livestock, it is important to know in detail about these changes, including shifts in the composition of systemic leukocyte populations, as this knowledge may help to focus on relevant cell populations when developing novel vaccines for use in juvenile versus adult animals. In this mini-review, a synoptic comparison of published PBMC populations, which were analysed in healthy weaned piglets as well as multiparous non-gestating sows, shows remarkable shifts within leukocyte populations. γδ T cells increase by factor 1.5, plasmacytoid dendritic cells and T helper cells more than double, and cytotoxic T cells as well as regulatory T cells increase more than four fold, whereas NK cells as well as B cells in adult sows comprise only 40% and monocytes 70% of the relative population sizes in weaned piglets. In summary, these insights into age-dependent shifts of porcine leukocyte populations indicate a principal increase of acquired immunity-associated leukocyte populations, whereas primarily innate immunity-associated cell types (NK cells, monocytes) are diminished.

Fermentation products as feed additives mitigate some ill-effects of heat stress in pigs

Heat stress (HS) may result in economic losses to pig producers across the USA and worldwide. Despite significant advancements in management practices, HS continues to be a challenge. In this study, an in-feed antibiotic (carbadox, CBX) and antibiotic alternatives ( [XPC], and [SGX] fermentation products) were evaluated in a standard pig starter diet as mitigations against the negative effects of HS in pigs. A total of 100 gilts were obtained at weaning (6.87 ± 0.82 kg BW, 19.36 ± 0.72 d of age) and randomly assigned to dietary treatments (2 rooms/treatment, 2 pens/room, 6 to 7 pigs/pen). After 4 wk of dietary acclimation, half of the pigs in each dietary group (1 room/dietary treatment) were exposed to repeated heat stress conditions (RHS; daily cycles of 19 h at 25°C and 5 h at 40°C, repeated for 9 d), and the remaining pigs were housed at constant thermal neutral temperature (25°C, [NHS]). Pigs subjected to RHS had elevated skin surface temperature ( < 0.05; average 41.7°C) and respiration rate ( < 0.05; 199 breaths per minute (bpm) during HS, and overall reduced ( < 0.05) BW, ADG, ADFI, and G:F regardless of dietary treatment. Independent of diet, RHS pigs had significantly shorter ( < 0.05) jejunum villi on d 3 and d 9 compared to NHS pigs. Heat stress resulted in decreased villus height to crypt depth ratio (V:C) in pigs fed with control diet with no added feed additive (NON) and CBX diets at d 3, whereas the pigs fed diets containing XPC or SGX showed no decrease. Transcriptional expression of genes involved in cellular stress (, , , ), tight junction integrity (, , ), and immune response (, , and ) were measured in the ileum mucosa. Pigs in all dietary treatments subjected to RHS had significantly higher ( < 0.05) transcript levels of and , and an upward trend ( < 0.07) of mRNA expression. RHS pigs had higher ( < 0.05) transcript levels of and in NON diet, in XPC and CBX diets, and in SGX diet compared to the respective diet-matched pigs in the NHS conditions. Neither RHS nor diet affected peripheral natural killer () cell numbers or NK cell lytic activity. In conclusion, pigs subjected to RHS had decreased performance, and supplementation with fermentation products in the feed (XPC and SGX) protected pigs from injury to the jejunum mucosa.

Mesenchymal stromal cells enhance the suppressive effects ofmyeloid-derived suppressor cells of multiple myeloma

Both mesenchymal stromal cells (MSCs) and myeloid-derived suppressor cells (MDSCs) have immunosuppressive properties, and their presence may confer a worse prognosis upon cancer patients. However, whether MSCs can enhance the immunosuppressive effects of MDSCs in MM remains unknown. We evaluated the influence of MSCs on MDSCs growth, apoptosis, and functions. Our results show that MSCs promote proliferation and inhibit apoptosis in MDSCs. Additionally, MSCs enhance the ability of MDSCs by inhibiting T-cell proliferation and IFN-γ production. Furthermore, both the mRNA and protein levels of Arg1 and NOS2 were upregulated in MDSCs. These results suggest that MSCs may exert immunomodulatory effects on MDSCs by upregulating Arg1 and NOS2.

Increased B and T Cell Responses in M. bovis Bacille Calmette-Guérin Vaccinated Pigs Co-Immunized with Plasmid DNA Encoding a Prototype Tuberculosis Antigen

The only tuberculosis vaccine currently available, bacille Calmette-Guérin (BCG) is a poor inducer of CD8(+) T cells, which are particularly important for the control of latent tuberculosis and protection against reactivation. As the induction of strong CD8(+) T cell responses is a hallmark of DNA vaccines, a combination of BCG with plasmid DNA encoding a prototype TB antigen (Ag85A) was tested. As an alternative animal model, pigs were primed with BCG mixed with empty vector or codon-optimized pAg85A by the intradermal route and boosted with plasmid delivered by intramuscular electroporation. Control pigs received unformulated BCG. The BCG-pAg85A combination stimulated robust and sustained Ag85A specific antibody, lymphoproliferative, IL-6, IL-10 and IFN-γ responses. IgG1/IgG2 antibody isotype ratio reflected the Th1 helper type biased response. T lymphocyte responses against purified protein derivative of tuberculin (PPD) were induced in all (BCG) vaccinated animals, but responses were much stronger in BCG-pAg85A vaccinated pigs. Finally, Ag85A-specific IFN-γ producing CD8(+) T cells were detected by intracellular cytokine staining and a synthetic peptide, spanning Ag85A131-150 and encompassing two regions with strong predicted SLA-1*0401/SLA-1*0801 binding affinity, was promiscuously recognized by 6/6 animals vaccinated with the BCG-pAg85A combination. Our study provides a proof of concept in a large mammalian species, for a new Th1 and CD8(+) targeting tuberculosis vaccine, based on BCG-plasmid DNA co-administration.

The porcine innate immune system: an update

Over the last few years, we have seen an increasing interest and demand for pigs in biomedical research. Domestic pigs (Sus scrofa domesticus) are closely related to humans in terms of their anatomy, genetics, and physiology, and often are the model of choice for the assessment of novel vaccines and therapeutics in a preclinical stage. However, the pig as a model has much more to offer, and can serve as a model for many biomedical applications including aging research, medical imaging, and pharmaceutical studies to name a few. In this review, we will provide an overview of the innate immune system in pigs, describe its anatomical and physiological key features, and discuss the key players involved. In particular, we compare the porcine innate immune system to that of humans, and emphasize on the importance of the pig as model for human disease.

Colostral antibody-mediated and cell-mediated immunity contributes to innate and antigen-specific immunity in piglets

Immunoglobulins and immune cells are critical components of colostral immunity; however, their transfer to and function in the neonate, especially maternal lymphocytes, is unclear. Cell-mediated and antibody-mediated immunity in sow blood and colostrum and piglet blood before (PS) and after (AS) suckling were assessed to investigate transfer and function of maternal immunity in the piglet. CD4, CD8, and γδ lymphocytes were found in sow blood and colostrum and piglet blood PS and AS; each had a unique T lymphocyte profile. Immunoglobulins were detected in sow blood, colostrum, and in piglet blood AS; the immunoglobulin profile of piglet serum AS mimicked that of sow serum. These results suggest selectivity in lymphocyte concentration into colostrum and subsequent lymphocyte transfer into the neonate, but that immunoglobulin transfer is unimpeded. Assessment of colostral natural killer activity and antigen-specific proliferation revealed that colostral cells are capable of influencing the innate and specific immune response of neonatal pigs.

Cell mediated innate responses of cattle and swine are diverse during foot-and-mouth disease virus (FMDV) infection: a unique landscape of innate immunity

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Harnessing the innate immunity can protect domestic animals from viruses.

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Innate immune cells have potential capacity to afford protection against infection.

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Understanding the innate and adaptive immunity will aid rational vaccine design.

Pathogens in general and pathogenic viruses in particular have evolved a myriad of mechanisms to escape the immune response of mammalian species. Viruses that cause acute disease tend to bear characteristics that make them very contagious, as survival does not derive from chronicity of infection, but spread of disease throughout the herd. Foot-and-mouth disease virus (FMDV) is one of the most contagious viruses known. Upon infection of susceptible species, cloven-hoofed animals, the virus proliferates rapidly and causes a vesicular disease within 2–4 days. Disease symptoms resolve by 10 days to 2 weeks and in most cases, virus can no longer be detected. Periods of fever and viremia are usually brief, 1–3 days. In vivo control of virus infection and clearance of the virus during and following acute infection is of particular interest. The interaction of this virus with cells mediating the early, innate immune response has been analyzed in a number of recent studies. In most reports, the virus has a distinct inhibitory effect on the response of cells early in infection. Here we review these new data and discuss the dynamics of the interaction of virus with different cell types mediating the immune response to infection.

PLGA nanoparticle entrapped killed porcine reproductive and respiratory syndrome virus vaccine helps in viral clearance in pigs

Porcine reproductive and respiratory syndrome (PRRS) is a chronic viral disease of pigs, has been posing a huge economic concern to pig industry worldwide. In this study, we developed biodegradable PLGA [poly(d,l-lactide-co-glycolide)] nanoparticle-entrapped killed PRRSV vaccine (Nano-KAg), and administered intranasally to pigs once and evaluated the immune correlates. In Nano-KAg vaccinated homologous virus challenged pigs, complete clearance of viremia was observed in 2 weeks, associated with a significant increase in virus neutralizing titers only in the lungs, compared to both unvaccinated and killed vaccine vaccinated pigs. The lung homogenate and sera of Nano-KAg vaccinated pigs had higher levels of IFN-γ and lower levels of TGF-β than control groups. Restimulation of mononuclear cells isolated from the lungs, blood, BAL, and TBLN of Nano-KAg vaccinated pigs’ secreted significantly increased levels of Th1 cytokines, IFN-γ and IL-12. In addition, higher frequencies of CD3⁺CD8⁺, CD4⁺CD8⁺, and γδ T cells, and reduced frequency of Foxp3⁺ T-regulatory cells were observed in Nano-KAg vaccinated pigs. Thus, intranasal delivery of Nano-KAg vaccine may be a suitable strategy to elicit anti-PRRSV immune response required to better clear viremia in pigs.

Comparative biology of γδ T cell function in humans, mice, and domestic animals

γδ T cells are a functionally heterogeneous population and contribute to many early immune responses. The majority of their activity is described in humans and mice, but the immune systems of all jawed vertebrates include the γδ T cell lineage. Although some aspects of γδ T cells vary between species, critical roles in early immune responses are often conserved. Common features of γδ T cells include innate receptor expression, antigen presentation, cytotoxicity, and cytokine production. Herein we compare studies describing these conserved γδ T cell functions and other, potentially unique, functions. γδ T cells are well documented for their potential immunotherapeutic properties; however, these proposed therapies are often focused on human diseases and the mouse models thereof. This review consolidates some of these studies with those in other animals to provide a consensus for the current understanding of γδ T cell function across species.

Morphine induces splenocyte trafficking into the CNS

Opioids significantly alter functional responses of lymphocytes following activation. The opiate Morphine, alters the Th1 to Th2 response and modulates functional responses such as cytolytic activity and T-cell proliferation. Although there has been extensive research involving morphine's effects on lymphocytes, little is known about the effects morphine has on lymphocyte trafficking. The objective of the study was to use in vivo bioluminescent imaging to determine morphine's effect on the trafficking pattern of splenocytes systemically and into the CNS either in a naïve state or following a neuroinflammatory stimulus. A neuroinflammatory response was induced by intracerebrally administering a DNA IFN-γ DNA plasmid into morphine-dependent or placebo wildtype mice. Mice with or without a neurostimulus received adoptively transferred firefly luciferase transgenic splenocytes and imaged. Morphine dependence significantly altered the inherent ability of splenocytes to traffic into the spleen, and lead to non-directed chaotic trafficking throughout the animal, including into the CNS. The morphine-mediated effects on trafficking were blocked by the antagonist naltrexone. Morphine dependence intensified splenocyte infiltration into the CNS following neuroinflammation induced by IFN-γ gene transfer. The study precented determined that morphine severely altered the ability of non-activated splenocytes to home to the spleen, inducing extrasplenic trafficking thoughout the animal. In addition to altering the ability of naive splenocyte to traffic to the spleen, this study demonstrated that morphine profoundly exacerbated lymphocyte infiltration into the CNS following a neurostimulus.

Oxygen is a master regulator of the immunogenicity of primary human glioma cells

With recent approval of the first dendritic cell (DC) vaccine for patient use, many other DC vaccine approaches are now being tested in clinical trials. Many of these DC vaccines employ tumor cell lysates (TL) generated from cells cultured in atmospheric oxygen (∼20% O₂) that greatly exceeds levels found in tumors in situ. In this study, we tested the hypothesis that TLs generated from tumor cells cultured under physiologic oxygen (∼5% O₂) would be more effective as a source for DC antigens. Gene expression patterns in primary glioma cultures established at 5% O₂ more closely paralleled patient tumors in situ and known immunogenic antigens were more highly expressed. DCs treated with TLs generated from primary tumor cells maintained in 5% O₂ took up and presented antigens to CD8 T cells more efficiently. Moreover, CD8 T cells primed in this manner exhibited superior tumoricidal activity against target cells cultured in either atmospheric 20% O₂ or physiologic 5% O₂. Together, these results establish a simple method to greatly improve the effectiveness of DC vaccines in stimulating the production of tumoricidal T cells, with broad implications for many of the DC-based cancer vaccines being developed for clinical application.

Effect of dietary supplementation of oregano essential oils to sows on colostrum and milk composition, growth pattern and immune status of suckling pigs

This study evaluated the effects of supplementing sow diets with oregano essential oils (OEO) during gestation and lactation on sow colostrum and milk composition and on the growth pattern and immune status of suckling pigs. A total of 70 second-parity sows were randomly assigned to 1 of 2 gestation dietary treatments within 24 h after service: control (CON) or CON + 250 mg/kg of OEO (OREG). In lactation, sows were again assigned to either the CON or OREG dietary treatment. Thus, the lactation treatments were CON-CON, CON-OREG, OREG-CON, and OREG-OREG. Colostrum and blood samples were collected from 6 sows per lactation dietary treatment. Thymus lymphocyte (T lymphocyte) subpopulations (γδ, cluster of differentiation 8, and 32 cluster of differentiation 4) were enumerated in blood and mammary secretions along with IGF-1, IgG, and IgA concentrations. Piglet growth rate were determined from 18, 17, 17, and 18 litters from the CON-CON, CON-OREG, OREG-CON, and OREG-OREG lactation dietary treatments, respectively. Growth rates were determined in 630 piglets, and piglets were individually identified and weighed on 1, 5, 9, 12, 16, and 19 d of age. Oregano essential oil supplementation during gestation or lactation had no effect (P > 0.05) on GE, CP, GE:CP, GE:fat, and IGF-1 in sow milk. Reductions of the fat percentage in milk on d 7 (P < 0.05) and d 14 (P = 0.07) were found in sows supplemented with OEO during lactation compared with those in the CON treatment. Milk from sows supplemented with OEO during lactation had the greatest number of T lymphocytes compared with those in the lactation CON treatment on d 14 of lactation (P < 0.01). The number of T lymphocytes in milk was greater for sows in the CON-OREG treatment compared with those other treatments on d 14 of lactation (P < 0.05). Energy intake was greater on d 1 to 5 in piglets from sows fed OEO during gestation than those from sows in the CON treatment (P < 0.05). A trend (P = 0.10) for greater milk intake was observed in piglets from sows supplemented with OEO during gestation compared with those from sows in the CON treatment. Similarly, a tendency for an increase in ADG on d 1 to 5 was found in piglets from sows supplemented with OEO during gestation compared with those from sows in the CON treatment (P = 0.10). Insulin-like growth factor-1 at birth and on d 7 and 14 of lactation did not differ among piglets from sows assigned to the different dietary treatments. Oregano essential oil supplementation of sow diets did not affect (P > 0.05) immunoglobulin concentrations in piglets after suckling. Supplementing sow diets with OEO during gestation or lactation did not affect (P > 0.05) the T lymphocytes, percentage of T-lymphocyte subpopulations, and natural killer cell activity of piglets during lactation. Supplementing sow diets with 250 mg/kg of OEO during gestation and lactation did not affect the growth potential of and immune responses in suckling piglets.

CD46 engagement on human CD4+ T cells produces T regulatory type 1-like regulation of antimycobacterial T cell responses

Understanding the regulation of human immune responses is critical for vaccine development and treating infectious diseases. We have previously shown that simultaneous engagement of the T cell receptor (TCR) and complement regulator CD46 on human CD4(+) T cells in the presence of interleukin-2 (IL-2) induces potent secretion of the immunomodulatory cytokine IL-10. These T cells mediate IL-10-dependent suppression of bystander CD4(+) T cells activated in vitro with anti-CD3 and anti-CD28 costimulation, reflecting a T regulatory type 1 (Tr1)-like phenotype. However, CD46-mediated negative regulation of pathogen-specific T cells has not been described. Therefore, we studied the ability of CD46-activated human CD4(+) T cells to suppress T cell responses to Mycobacterium bovis BCG, the live vaccine that provides infants protection against the major human pathogen Mycobacterium tuberculosis. Our results demonstrate that soluble factors secreted by CD46-activated human CD4(+) T cells suppress mycobacterium-specific CD4(+), CD8(+), and γ(9)δ(2) TCR(+) T cells. Dendritic cell functions were not downregulated in our experiments, indicating that CD46-triggered factors directly suppress pathogen-specific T cells. Interestingly, IL-10 appeared to play a less pronounced role in our system, especially in the suppression of γ(9)δ(2) TCR(+) T cells, suggesting the presence of additional undiscovered soluble immunoregulatory factors. Blocking endogenous CD46 signaling 3 days after mycobacterial infection enhanced BCG-specific T cell responses in a subset of volunteers. Taken together, these results indicate that CD46-dependent negative regulatory mechanisms can impair T cell responses vital for immune defense against mycobacteria. Therefore, modulating CD46-induced immune regulation could be integral to the development of improved tuberculosis therapeutics or vaccines.

Superior efficacy of tumor cell vaccines grown in physiologic oxygen

PURPOSE

Atmospheric oxygen (∼20% O(2)) has been the universal condition employed to culture tumor cells used as vaccine antigen. We tested the hypothesis that reducing oxygen tension would increase the efficacy of tumor cell lysate vaccines.

EXPERIMENTAL DESIGN

GL261 glioma cells and EMT6 breast carcinoma cells were grown in 5% or 20% O(2). Syngeneic tumor-bearing mice were vaccinated with these tumor cell lysates mixed with CpG oligodeoxynucleotides as an adjuvant. Tumor infiltrating T cells and apoptotic GL261 cells were quantified by immunohistochemistry. Tumor-reactive immunoglobulin was detected by Western blot. Ovalbumin and gp100-derived peptides were mixed with GL261 lysates as marker antigens to detect changes in presentation of exogenous antigen on MHC class I in vitro, and in vivo following adoptive transfer of gp100-specific CD8(+) T cells.

RESULTS

Mice bearing orthotopic glioma and breast carcinoma survived significantly longer when vaccinated with 5% O(2) lysates. Antigen-specific CTL activation was significantly enhanced following stimulation with lysates derived from GL261 cells grown in 5% O(2) versus 20% O(2) through a mechanism that involved enhanced cross-presentation of exogenous antigen on MHC I. Vaccination with 5% O(2) GL261 cell lysates caused a significant increase in CTL proliferation, tumoricidal function, and trafficking into brain tumor sites, whereas 20% O(2) lysate vaccines predominantly evoked an antibody response.

CONCLUSIONS

Tissue culture oxygen functions as an "immunologic switch" by dictating the cellular and humoral immune responses elicited by tumor cell lysates. These results have profound implications for cancer vaccines that utilize tumor cells as the source of antigen.

Porcine T lymphocytes and NK cells--an update

Natural killer (NK) cells represent an important cell population of the innate immune system with the ability to attack spontaneously pathogen-infected and malignant body cells as well as to produce immune-regulatory cytokines. T lymphocytes belong to the adaptive immune system and perform a wide array of functions in immune regulation, inflammation and protective immune responses. In this review we summarize the current knowledge about the phenotype and functional characteristics of these two cell populations in swine. Porcine NK cells can be distinguished from T cells by the complex phenotype perforin+ CD3(-)CD4(-)CD5(-)CD6(-)CD8alpha+CD8beta(-)CD11b+CD16+. Investigations so far show that these cells have the capacity to lyse virus-infected target cells and respond to various regulatory cytokines. Such cytokines can induce interferon-gamma (IFN-gamma) production in porcine NK cells, as well as the up-regulation of effector/activation molecules like perforin and CD25. Porcine T cells can be divided into a number of subpopulations, including a prominent fraction of T cells expressing T-cell receptors (TCR) with gammadelta-chains. Like TCR-alphabeta T cells, these TCR-gammadelta T cells can express CD8alpha and MHC class II, two molecules which in swine seem to be correlated with an activation status of T cells. Functional properties of these cells seem to include cytolytic activity as well as antigen presentation; however, both aspects require further investigation. Like in other species, TCR-alphabeta T cells in swine comprise MHC class-I restricted cytolytic T cells, T-helper cells and recently identified regulatory T cells. We summarize data on the phenotype and function of these cells including memory cell formation. Current knowledge suggests that MHC class-I restricted cytolytic T cells can be identified by the expression of CD8alphabeta heterodimers. T-helper cells express CD4 as well as other activation-related markers, including CD8alpha, MHC class II and CD45RC. Porcine regulatory T cells have a phenotype similar to that of mouse and humans: CD4+CD25+Foxp3+. First results indicate that these cells can suppress proliferation of other T cells and produce IL-10. Finally, the abundant expression of swine-specific activation markers CD8alpha and MHC class II on T cells and NK cells is discussed in more detail.

Inhibition of phosphoantigen-mediated gammadelta T-cell proliferation by CD4+ CD25+ FoxP3+ regulatory T cells

Tumour growth promotes the expansion of CD4(+) CD25(+) FoxP3(+) regulatory T cells (Tregs) which suppress various arms of immune responses and might therefore contribute to tumour immunosurveillance. In this study, we found an inverse correlation between circulating Treg frequencies and phosphoantigen-induced gammadelta T-cell proliferation in cancer patients, which prompted us to address the role of Tregs in controlling the gammadelta T-cell arm of innate immune responses. In vitro, human Treg-peripheral blood mononuclear cell (PBMC) co-cultures strongly inhibited phosphoantigen-induced proliferation of gammadelta T cells and depletion of Tregs restored the impaired phosphoantigen-induced gammadelta T-cell proliferation of cancer patients. Tregs did not suppress other effector functions of gammadelta T cells such as cytokine production or cytotoxicity. Our experiments indicate that Tregs do not mediate their suppressive activity via a cell-cell contact-dependent mechanism, but rather secrete a soluble non-proteinaceous factor, which is independent of known soluble factors interacting with amino acid depletion (e.g. arginase-diminished arginine and indolamine 2,3-dioxygenase-diminished tryptophan) or nitric oxide (NO) production. However, the proliferative activity of alphabeta T cells was not affected by this cell-cell contact-independent suppressive activity induced by Tregs. In conclusion, these findings indicate a potential new mechanism by which Tregs can specifically suppress gammadelta T cells and highlight the strategy of combining Treg inhibition with subsequent gammadelta T-cell activation to enhance gammadelta T cell-mediated immunotherapy.

Bovine WC1(-) gammadeltaT cells incubated with IL-15 express the natural cytotoxicity receptor CD335 (NKp46) and produce IFN-gamma in response to exogenous IL-12 and IL-18

The gammadeltaT cells of ruminants are believed to participate in innate immunity and have been described with regulatory, inflammatory and cytotoxic functions. Here we describe a subset of CD3(+) TcR1(+) WC1(-)gammadeltaT cells expressing CD335 (NKp46), classically associated with CD3(-) natural killer (NK) cells, as a consequence of incubation with IL-15. This population, undetectable at the time of collection, developed after 2 week of IL-15 culture from splenic leukocytes (SPL) reaching greater than 50% of the total gammadeltaT cells. However, they did not grow well from peripheral blood leukocytes (PBL). Splenic gammadeltaT cells positively selected by magnetic separation prior to incubation with IL-15 and analyzed by flow cytometry, consistently yielded CD3(+) cells expressing CD335. These cells arose from the CD335(-)gammadeltaT cell population suggesting that the new population represents up-regulation of CD335 by gammadeltaT cells. CD335 mRNA expression from sorted IL-15-incubated SPL CD335(+)gammadeltaT cells or NK cells exceeded that of CD335(-)gammadeltaT cells. Incubation with IL-12 and IL-18 increased the number of CD335(+)gammadeltaT cells in both the PBL and SPL fractions as compared to controls or IL-12 or IL-18 alone. In addition, CD335(+)gammadeltaT cells demonstrated a robust ability to produce IFN-gamma in response to exogenous IL-12 and IL-18. Taken as a whole, we describe a new phenotypically distinct bovine gammadeltaT cell sub-population capable of participating in type 1 immune responses.

In vitro and in vivo apoptosis detection using membrane permeant fluorescent-labeled inhibitors of caspases

Apoptosis detection methodology is an ever evolving science. The caspase family of cysteine proteases plays a central role in this environmentally conserved mechanism of regulated cell death. New methods that allow for the improved detection and monitoring of the apoptosis-associated proteases are key for further advancement of our understanding of apoptosis-mediated disease states such as cancer and Alzheimer's disease. From the use of membrane permeant fluorescent-labeled inhibitors of caspases (FLICA) probe technology, we have demonstrated their successful use as tools in the detection of apoptosis activity within the in vitro and in vivo research setting. In this chapter, we provide detailed methods for performing in vitro apoptosis detection assays in whole living cells, using flow cytometry, and 96-well fluorescence plate reader analysis methods. Furthermore, novel flow cytometry-based cytotoxicity assay methods, which incorporate the FLICA probe for early apoptosis detection, are described. Inclusion of this sensitive apoptosis detection probe component into the flow-based cytotoxicity assay format results in an extremely sensitive cytotoxicity detection mechanism. Lastly, in this chapter, we describe the use of the FLICA probe for the in vivo detection of tumor cell apoptosis in mice and rats. These early stage in vivo-type assays show great potential for whole animal apoptosis detection research.

Robust γδ+ T cell expansion in infants immunized at birth with BCG vaccine

Cell-mediated immune responses to BCG vaccine were evaluated in 7-month-old infants vaccinated with intradermal combined BCG and Hepatitis B or intradermal BCG and intramuscular Hepatitis B at birth. Peripheral blood mononuclear cell cultures from both groups showed CD4(+), CD8(+) and remarkable gammadelta(+) T cell BCG-specific proliferation, without significant differences. Also, IL-10, IL-12, IFN-gamma and TNF-alpha concentrations in culture supernatants, measured by ELISA, were similar. The results suggested that the combined BCG and Hepatitis B vaccine was as immunogenic as BCG separated from Hepatitis B vaccine.

Bortezomib enhances dendritic cell (DC)-mediated induction of immunity to human myeloma via exposure of cell surface heat shock protein 90 on dying tumor cells: therapeutic implications

Most anticancer chemotherapies are immunosuppressive and induce nonimmunogenic tumor cell death. Bortezomib, a specific inhibitor of 26S proteasome, has shown clinical activity in several human tumors, including myeloma. Here we show that the uptake of human myeloma cells by dendritic cells (DCs) after tumor cell death by bortezomib, but not gamma irradiation or steroids, leads to the induction of antitumor immunity, including against primary tumor cells, without the need for any additional adjuvants. The delivery of activating signal from bortezomib-killed tumor cells to DCs depends on cell-cell contact between DCs and dying tumor cells and is mediated by bortezomib-induced exposure of heat shock protein 90 (hsp90) on the surface of dying cells. The combination of bortezomib and geldanamycin (an hsp90 inhibitor) leads to greater apoptosis of tumor cells but abrogates their immunogenicity. These data identify drug-induced exposure of endogenous heat shock proteins on the surface of dying cells as a mechanism of immunogenic death of human tumors. Specific targeting of bortezomib to tumors may enhance their immunogenicity and the induction of antitumor immunity.

Morphine modulates gammadelta lymphocytes cytolytic activity following BCG vaccination

Chronic opioid administration modulates lymphocytes' functional capabilities increasing susceptibility to infectious diseases. Bacille-Calmette-Guérin (BCG) vaccination initiates a non-specific and specific cell-mediated immunity orchestrated by T lymphocytes including gammadelta T lymphocytes. gammadelta T lymphocytes increase in natural killer and antigen-directed cytolytic response following BCG vaccination. The objective of this study was to determine morphine effects on gammadelta T lymphocytes' cytolytic activity. Pigs were chronically administered morphine and subsequently vaccinated with Mycobacterium bovis BCG. By administering morphine prior to BCG vaccination, natural killer response was significantly suppressed (p=.034). Furthermore, innate cytolytic response against M. bovis-infected monocytes (p=.002) as well as antigen specific cytolytic functions (p=.04) were significantly altered due to morphine administration. It was concluded that administering morphine prior to BCG vaccination significantly altered gammadelta T lymphocyte cytolytic responses.

γδ Lymphocyte Response to Porcine Reproductive and Respiratory Syndrome Virus

Porcine reproductive and respiratory syndrome virus (PRRSV) continues to be one of the most important diseases facing swine industry today. Following PRRSV infection pigs develop both humoral and cell-mediated responses following PRRSV exposure; however, the relative importance in protection and clearance of the virus is not yet completely understood. Swine contain a large percentage of gammadelta T-lymphocytes in peripheral circulation capable of responding to various pathogens in both an innate and specific immune response. The objectives of this study were to determine whether gammadelta lymphocytes functionally respond to PRRSV upon initial exposure and re-exposure. Four month old PRRSV free gilts were intranasally inoculated with a field isolate MN-30100 then assessed at various time points post infection. On day 120, pigs were re-exposed with MN-30100 PRRSV strain and subsequently were bled on days 0, 7, and 14 post re-exposure. Lymphocyte subpopulations, antigen specific proliferation, and IFN-gamma production were evaluated throughout the study. Circulating gammadelta lymphocytes in PRRSV exposed animals expanded between days 14 to 70 (d14-d70, p = 0.016); following antigen stimulation, gammadelta lymphocyte proliferated by day 14 (d0-d14, p = 0.001) continuing through day 60. gammadelta lymphocytes produced IFN-gamma by day 14 pi continuing through day 50 (d0-d50, p = 0.004). Following re-exposure both gammadelta+ and CD4+ lymphocytes increased in IFN-gamma production. These results are not fully conclusive on the role of gammadelta lymphocytes against PRRSV; the data indicate that gammadelta lymphocytes specifically respond to PRRSV.