Swine as an allotransplantation model

Humanising and dehumanising pigs in genomic and transplantation research

Biologists who work on the pig (Sus scrofa) take advantage of its similarity to humans by constructing the inferential and material means to traffic data, information and knowledge across the species barrier. Their research has been funded due to its perceived value for agriculture and medicine. Improving selective breeding practices, for instance, has been a driver of genomics research. The pig is also an animal model for biomedical research and practice, and is proposed as a source of organs for cross-species transplantation: xenotransplantation. Genomics research has informed transplantation biology, which has itself motivated developments in genomics. Both have generated models of correspondences between the genomes of pigs and humans. Concerning genomics, I detail how researchers traverse species boundaries to develop representations of the pig genome, alongside ensuring that such representations are sufficiently porcine. In transplantation biology, the representations of the genomes of humans and pigs are used to detect and investigate immunologically-pertinent differences between the two species. These key differences can then be removed, to 'humanise' donor pigs so that they can become a safe and effective source of organs. In both of these endeavours, there is a tension between practices that 'humanise' the pig (or representations thereof) through using resources from human genomics, and the need to 'dehumanise' the pig to maintain distinctions for legal, ethical and scientific reasons. This paper assesses the ways in which this tension has been managed, observing the differences between its realisations across comparative pig genomics and transplantation biology, and considering the consequences of this.

Fascinating Dendritic Cells—Sentinel Cells of the Immune System a Review

Dendritic cells (DC) are specialized antigen presenting cells which have the unique ability to activate naive T-lymphocytes. Their role in the immune system is much more sophisticated than it seems, as they do not kill the pathogens directly, but provide a long-lasting antigen specific immune response thanks to that sufficiently bridging the innate and the adaptive immunity. In recent years, there has been a growing interest in studies of their role in immune regulation, autoimmune reactions, as well as in immune responses against pathogens and tumours. Processing and presentation capabilities of a highly specific and unique tumour antigen makes them an interesting tool for stimulating effective anti-tumour immunity. In vitro generations of DC represent a preferred model for more detailed studies of DC biology in other fields. The aim of this review was to discuss the main role of dendritic cells in the body as well as their current use as experimental models for further scientific studies.

The MHC-characterized Miniature Swine: Lessons Learned From a 40-Year Experience in Transplantation

Over the last 40 y, a specialized herd of miniature swine has been intentionally bred to develop lines of animals homozygous for the swine major histocompatibility complex (MHC), which have facilitated transplantation studies across reproducible MHC and minor antigen mismatch barriers. These MHC-characterized miniature swine (Mc-MS) have been used for the study of novel surgical techniques, various approaches to tolerance induction of solid organ and vascularized composite allografts, as well as studies of the immunobiology of allografts and xenografts. Mc-MS possess characteristics that are highly advantageous to these studies, and their continued use will likely continue to play an important role in bridging "bench-to-cage-to bedside" therapies in the field of transplantation. In this review, we highlight the seminal contributions of the Mc-MS model to the field and analyze their role in the broader context of large animal models in transplantation research.

Experimental Design for Composite Face Transplantation

Face allotransplantation represents a novel frontier in complex human facial defect reconstruction. To develop more refined surgical techniques and yield fine results, it is first imperative to make a suitable animal model. The development of a composite facial allograft model in swine is more appealing: the facial anatomy, including facial nerve and vascular anatomy, is similar to that of humans. Two operative teams performed simultaneously, one assigned to harvest the donor and the other to prepare the recipient in efforts to shorten operative time. The flap was harvested with the common carotid artery and external jugular vein, and it was transferred to the recipient. After insetting the maxilla, mandible, muscles, and skins, the anastomosis of the external jugular vein, external carotid artery, and facial nerve were performed. The total mean time of transplantation was 7 hours, and most allografts survived without vascular problems. The authors documented that this model is well qualified to be used as a standard transplantation training model and future research work, in every aspect.

Genome-wide association study for T lymphocyte subpopulations in swine

Background

Lymphocytes act as a major component of the adaptive immune system, taking very crucial responsibility for immunity. Differences in proportions of T-cell subpopulations in peripheral blood among individuals under same conditions provide evidence of genetic control on these traits, but little is known about the genetic mechanism of them, especially in swine. Identification of the genetic control on these variants may help the genetic improvement of immune capacity through selection.

Results

To identify genomic regions responsible for these immune traits in swine, a genome-wide association study was conducted. A total of 675 pigs of three breeds were involved in the study. At 21 days of age, all individuals were vaccinated with modified live classical swine fever vaccine. Blood samples were collected when the piglets were 20 and 35 days of age, respectively. Seven traits, including the proportions of CD4+, CD8+, CD4+CD8+, CD4+CD8−, CD4−CD8+, CD4−CD8− and the ratio of CD4+ to CD8+ T cells were measured at the two ages. All the samples were genotyped for 62,163 single nucleotide polymorphisms (SNP) using the Illumina porcineSNP60k BeadChip. 40833 SNPs were selected after quality control for association tests between SNPs and each immune trait considered based on a single-locus regression model. To tackle the issue of multiple testing in GWAS, 10,000 permutations were performed to determine the chromosome-wise and genome-wise significance levels of association tests. In total, 61 SNPs with chromosome-wise significance level and 3 SNPs with genome-wise significance level were identified. 27 significant SNPs were located within the immune-related QTL regions reported in previous studies. Furthermore, several significant SNPs fell into the regions harboring known immunity-related genes, 14 of them fell into the regions which harbor some known T cell-related genes.

Conclusions

Our study demonstrated that genome-wide association studies would be a feasible way for revealing the potential genetics variants affecting T-cell subpopulations. Results herein lay a preliminary foundation for further identifying the causal mutations underlying swine immune capacity in follow-up studies.

Mapping quantitative trait loci for T lymphocyte subpopulations in peripheral blood in swine

Background

Increased disease resistance through improved general immune capacity would be beneficial for the welfare and productivity of farm animals. T lymphocyte subpopulations in peripheral blood play an important role in immune capacity and disease resistance in animals. However, very little research to date has focused on quantitative trait loci (QTL) for T lymphocyte subpopulations in peripheral blood in swine.

Results

In the study, experimental animals consist of 446 piglets from three different breed populations. To identify QTL for T lymphocyte subpopulations in peripheral blood in swine, the proportions of CD4+, CD8+, CD4+CD8+, CD4+CD8-, CD4-CD8+, and CD4-CD8- T cells and the ratio of CD4+:CD8+ T cells were measured for all individuals before and after challenge with modified live CSF (classical swine fever) vaccine. Based on the combined data of individuals from three breed populations, genome-wide scanning of QTL for these traits was performed based on a variance component model, and the genome wide significance level for declaring QTL was determined via permutation tests as well as FDR (false discovery rate) correction. A total of 27 QTL (two for CD4+CD8+, one for CD4+CD8-, three for CD4-CD8+, two for CD4-CD8-, nine for CD4+, two for CD8+, and eight for CD4+:CD8+ ratio) were identified with significance level of FDR < 0.10, of which 11 were significant at the level of FDR < 0.05, including the five significant at FDR < 0.01.

Conclusions

Within these QTL regions, a number of known genes having potential relationships with the studied traits may serve as candidate genes for these traits. Our findings herein are helpful for identification of the causal genes underlying these immune-related trait and selection for immune capacity of individuals in swine breeding in the future.

The temporal pattern of postnatal neurogenesis found in the neocortex of the Göttingen minipig brain

The Göttingen minipig (G-mini) is increasingly used as a non-primate model for human neurological diseases. We applied design-based stereology on five groups of G-minis aged 1 day, 14 days, 30 days, 100 days, and 2 years or older to estimate the pattern of postnatal neuron number development in the neocortex. Two time periods for the postnatal increase of neocortical neuron number were observed from the time of birth to day 14 (P=0.013) and from day 30 to day 100 (P<0.001). No significant change in neuron number was found from day 14 to 30 (P=0.58) and day 100 onward (P=0.39). The average estimated total number of neurons in the neocortex was 236, 274, 264, 338, and 353 million, respectively. Since neurogenesis and neuronal migration in the human neocortex are generally accepted to be complete before term, the application of G-mini as human disease models may be inappropriate before day 100. However, G-mini may serve as a valuable model for the studies of ongoing neurogenesis in the living brain.

Immunological study of allogeneic mesenchymal stem cells during bone formation

Autologous mesenchymal stem cells (MSCs) are limited in their clinical application because tissue-engineered bone cannot be pre-fabricated. Allogeneic MSCs are readily available but carry the risk of transplant rejection. It is not yet clear whether allogeneic MSCs can induce a rejection response during bone formation. In this study, two strains of genetically unmatched mini-pigs were used as experimental animals to study the immunological changes in MSCs in vitro and in vivo when generating bone. Mini-pig MSCs showed low immunogenicity during osteogenesis both in vitro and in vivo, indicating that allogeneic MSCs had little or no immunogenicity in osteosis. In conclusion, allogeneic MSCs are an important source of seed cells for the tissue engineering of bone. This favours the clinical application of pre-constructed tissue-engineered bone.

Month-of-birth effect on further body size in a pig model

Previous studies unanimously confirmed the existence of a dependence of human body size on the month of birth. The cause of the phenomenon has not been identified yet, although some possible causes were proposed e.g. seasonal changes of climatic and nutritional conditions. This study explored the issue in an animal model of 20,513 pigs. We found that body weights of 6-month-old pigs were the highest for subjects born in February, but for 2-month-old pigs the peak fell in May. Any statistical correlation between the month of birth and later body weight may be induced by (1) a long-term effect of the month of birth on further growth potential (LTE), or by (2) a short-term effect of seasonal factors differentiating the growth rate (STE), so we developed a mathematical method to separate the effects. The analysis proved that (1) the observed correlations resulted only from the STE, with May-June being the months of the highest growth tempo, and that (2) there was no significant LTE. The short-term effect was responsible for differences between patterns of weight for 2- and 6-month-old animals by the month of birth: since a pig monthly gain of weight increases with age, it is favorable for it to be born in February to attain the greatest weight at the age of 6 months, whereas 2-month-old piglets are heaviest when born a month or two before the May/June optimum for growth. The lack of a long-term effect of the month of birth on pigs' weight supports the hypothesis of the cultural character of factor(s) responsible for the relationship between the month of birth and later body size in humans.

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.

Long-term survival of an allografted submandibular gland in a miniature swine model given immunosuppressant drugs

We used a model of allografts of submandibular glands in miniature swine to test the requirements of immunosuppressants for the survival of such grafts. Animals in the first group (n=6) were given no immunosuppressant, and the submandibular glands were rejected within 7 days. Those in the low-dose group (n=4) were treated with a low dose of cyclosporine, methylprednisolone, and azathioprine. The allografts were rejected on days 15, 17, 19, and 20. The animals in the high-dose group (n=6) were treated with a high dose of cyclosporin, methylprednisolone, and azathioprine. Three allografts were rejected, on days 35, 48, and 60. One animal died from anaesthetic problems on day 30 after transplantation, and there were no signs of rejection in the allograft. The other two allografts survived for 100 days with secretory function and no signs of rejection. After we discontinued the immunosuppression on day 100, the two remaining allografts were rejected on days 121 and 128. Blood tests and biopsy specimens of the heart, lung, liver, and kidneys were normal in all animals that were given immunosuppressants. To our knowledge, this study is the first to describe long-term survival of allografted submandibular glands with secretory function in miniature swine.

Crossing the bridge: large animal models in translational transplantation research

Many methods for reducing the immunosuppressive requirements of allotransplantation have been proposed based on a growing understanding of physiological and allospecific immunity. As these regimens are developed for clinical application, they require validation in models that are reasonably predictive of their performance in humans. This article provides an overview of the large animal models commonly used to test immunomodulatory organ transplant protocols. The rationale for the use of large animals and the effects of common immunosuppressants in the dog, pig, and non-human primate are reviewed. Promising methods for the induction of allospecific tolerance are surveyed with references to early human trials where appropriate.

Impairment of the Peripheral Lymphoid Compartment in Iron-deficient Piglets

The aim of this study was to investigate the effect of neonatal iron deficiency on immune functions in young piglets. While control piglets were not given any iron preparation until the age of 21 days, another group of piglets was given 200 mg of Fe(3+)-dextran i.m. on day 3. Red blood cell parameters in the former, iron-deficient group were characteristic of hypochromic anaemia. In addition, the total leucocyte count (P < 0.01), relative and absolute neutrophil count (P < 0.01) and absolute lymphocyte count (P < 0.05) in peripheral blood were found significantly lower in iron-deficient piglets than in their iron-supplemented counterparts. Lymphocyte activity as measured by in vitro lymphocyte transformation test was impaired in iron-deficient piglets. A statistically significant decrease in circulating B-lymphocyte numbers was found in non-supplemented animals. Iron deficiency apparently negatively influenced the immunocompetence in piglets.

Porcine dendritic cells generated in vitro: morphological, phenotypic and functional properties

Despite the central role that dendritic cells (DC) play in immune regulation and antigen presentation, little is known about porcine DC. In this study, two sources of DC were employed. Bone marrow haematopoietic cell-derived DC (BM-DC) were generated using granulocyte-macrophage colony-stimulating factor (GM-CSF) in the presence or absence of tumour necrosis factor-alpha (TNF-alpha). Monocyte-derived DC (Momicron-DC) were generated with GM-CSF and interleukin-4 (IL-4). In both systems, non-adherent cells developed with dendritic morphology, expressing high levels of major histocompatibility complex (MHC) class II. The presence of TNF-alpha increased the BM-DC yield, and enhanced T-cell stimulatory capacity. Both BM-DC and Momicron-DC expressed the pan-myeloid marker SWC3, as well as CD1 and CD80/86, but were also CD14+ and CD16+. The CD16 molecule was functional, acting as a low-affinity Fc receptor. In contrast, the CD14 on DC appeared to differ functionally from monocyte CD14: attempts to block CD14, in terms of lipopolysaccharide (LPS)-induced procoagulant activity (PCA), failed. The use of TNF-alpha or LPS for DC maturation induced up-regulation of MHC class II and/or CD80/86, but also CD14. Allogeneic mixed leucocyte reactions and staphylococcal enterotoxin B antigen presentation assays demonstrated that these DC possessed potent T-cell stimulatory capacity. No T helper cell polarization was noted. Both the BM-DC and the Momicron-DC induced a strong interferon-gamma and IL-4 response. Taken together, porcine DC generated in vitro possess certain characteristics relating them to DC from other species including humans, but the continued presence of CD14 and CD16 on mature and immature porcine DC was a notable difference.

Intermediate stages in monocyte-macrophage differentiation modulate phenotype and susceptibility to virus infection

The kinetics of monocyte-macrophage differentiation was analysed using two Swine Workshop Cluster (SWC) CD molecules: SWC1 and SWC9. Myeloid cells were selected by labelling for the common myeloid antigen, SWC3. Confirmation of macrophage identification used acid phosphatase and phagocytosis activities. During differentiation, SWC1 was gradually lost. SWC9 was absent on monocytes but up-regulated early. Consequently, monocytes were SWC1+ SWC9- and macrophages were SWC1- SWC9+. An additional, intermediate, cell population was identified as SWC1+ SWC9+. Size and granularity characteristics mirrored the monocyte, macrophage and intermediate-cell phenotypes. Overall, SWC9 up-regulation was central in macrophage differentiation and dependent on plasma factors. The concomitant loss of SWC1 was independent of these factors, but always associated with mature macrophages. Upon up-regulation of SWC9, the SWC1+ SWC9+ intermediate monocytic cells became susceptible to African swine fever virus infection. These results demonstrate the heterogeneity of monocytic cell differentiation and the importance of these characteristics for interaction with monocytotropic viruses.

Mapping Quantitative Trait Loci for Immune Capacity in the Pig

Immune capacity traits show considerable genetic variation in outbred populations. To identify quantitative trait loci (QTLs) for immune capacity in the pig, various measures of immune function (total and differential leukocyte counts, neutrophil phagocytosis, mitogen-induced proliferation, IL-2 production, and virus induced IFN-α production in whole blood cultures, and Ab responses to two Escherichia coli antigens) were determined in 200 F2 animals from a wild pig–Swedish Yorkshire intercross. The pedigree has been typed for 236 genetic markers covering all autosomes, the X chromosome and the X/Y pseudoautosomal region. Through interval mapping using a least-squares method, four QTLs with significant effects were identified; one for total leukocyte counts, one for mitogen-induced proliferation, one for prevaccination levels of Abs to E. coli Ag K88, and one for Ab response to the O149 Ag. In addition, several putative QTLs were indicated. The results from the present study conclusively show that it is possible to identify QTLs for immune capacity traits in outbred pig populations by genome analysis.

Differential adhesion molecule expression on porcine mononuclear cell populations

Adhesion molecule expression was analysed on porcine blood and lymphoid organ CD4+ CD8 naive T helper (Th) lymphocytes, CD4+CD8+ memory Th lymphocytes (particular to the pig), CD4-CD8high cytotoxic T (Tc) lymphocytes, CD4 CD8low NK cells (CD3- in the pig), CD4-CD8- T-cell receptor-gammadelta-positive (TCRgammadelta+) lymphocytes, B lymphocytes and monocytes. While CD44 expression was relatively homogeneous amongst mononuclear cells, differences were noted for the integrins. Blood naive Th lymphocytes were CD49d(low)CD11a(low), as were splenic naive Th cells; blood memory Th lymphocytes were CD49d(high)CD11a(low), splenic memory Th cells were CD49d(high)CD11a(high) with a CD49d(high)CD11a(low) subpopulation; blood Tc lymphocytes were mainly CD49d(low)CD11a(low), and splenic cells were CD49d(high) CD11a(high). Lymph node lymphocytes were more homogeneous in their integrin expression. These were relatively CD49d(low)CD11a(low), except the memory Th lymphocytes which had higher integrin expression. B lymphocytes related to the majority of integrin(low) T cells, while monocytes and NK cells were CD49d(high) CD11a(high); gammadelta T lymphocytes showed variable CD49d expression but a CD11a(high) phenotype. CD49d(high) CD11a(high) co-expression was found, and this phenotype was typical of, but not exclusive to, CD25+ (activated) lymphocytes. These results demonstrated that porcine memory Th lymphocytes and NK cells, as well as activated cells, would have increased integrin-dependent activities compared with naive Th lymphocytes, and integrin-dependent reactions would probably vary between blood and lymphoid organ cells.

Monoclonal antibodies specific for porcine monocytes/macrophages: macrophage heterogeneity in the pig evidenced by the expression of surface antigens

Macrophages are widely distributed in most tissues of the body, where they play important roles in host defense and repair of tissue damage. In this report we describe the production and characterization of a panel of six monoclonal antibodies (mAb) against porcine macrophages and their use for phenotyping tissue macrophages. All mAbs were produced by immunizing mice with porcine alveolar macrophages. Three of them (2A10/11, 3B11/11 and 3F7/11) react mainly with macrophages and, at a lower extent, blood monocytes, whereas the others (1E12/11, 2C12/10 and 4E9/11) also recognize granulocytes. Antigens recognized by these antibodies could be characterized by Western blot and/or immunoprecipitation, with the exception of that one recognized by 2C12/10. By their behavior in SDS-PAGE under reducing and nonreducing conditions, all seem to be single polypeptides, whose apparent molecular weight under reducing conditions are: 1E12/11 and 3B11/11 larger than 204 kDa; 2A10/11, 150 kDa; 4E9/11, 125-170 kDa; and 3F7/11, 135 kDa. Immunohistochemical analyses of both lymphoid and non-lymphoid organs using these mAbs reveal important antigenic heterogeneity among tissue macrophages. These mAbs are, therefore, useful tools for the study of porcine macrophage maturation and differentiation and for determining their heterogeneity both in normal and pathological conditions.