Characterisation of porcine bone marrow progenitor cells identified by the anti-c-kit (CD117) monoclonal antibody 2B8/BM

Characterizing the immune response to myocardial infarction in pigs

Though myocardial infarction (MI) in pigs is a well-established translational large animal model, it has not yet been widely used for immunotherapy studies, and a comprehensive description of the immune response to MI in this species is lacking. We induced MI in Landrace pigs by balloon occlusion of the left anterior descending artery over 90 min. Within 14 days, the necrotic myocardium was progressively replaced by scar tissue with involvement of myofibroblasts. We characterized the immune response in the heart ex vivo by (immuno)histology, flow cytometry, and RNA sequencing of myocardial tissue on days 3, 7, and 14 after MI. Besides a clear predominance of myeloid cells among heart-infiltrating leukocytes, we detected activated T cells and an increasing proportion of CD4+ Foxp3+ regulatory T cells (Treg), especially in the infarct core-findings that closely mirror what has been observed in mice and humans after MI. Transcriptome data indicated inflammatory activity that was persistent but markedly changing in character over time and linked to extracellular matrix biology. Analysis of lymphocytes in heart-draining lymph nodes revealed significantly higher proliferation rates of T helper cell subsets, including Treg on day 7 after MI, compared to sham controls. Elevated frequencies of myeloid progenitors in the spleen suggest that it might be a site of emergency myelopoiesis after MI in pigs, as previously shown in mice. We thus provide a first description of the immune response to MI in pigs, and our results can aid future research using the species for preclinical immunotherapy studies.

Investigating porcine parvoviruses genogroup 2 infection using in situ polymerase chain reaction

Background

Porcine parvovirus 2 (PPV2) was detected in swine serum without showing any relationship with disease. The emergence of the virus seemed to be a unique event until other genetically highly similar parvoviruses were identified in China and, later in 2012, the presence of the virus was also described in Europe. PPV2 is widely distributed in pig populations where it is suspected to be involved in respiratory conditions, based on its frequent detection in lung samples. In order to investigate the potential pathogenic involvement of PPV2, 60 dead pigs were examined from two farms. They were necropsied and tested for PPV2 and PCV2 (Porcine circovirus type 2) by PCR; by Brown and Brenn (B&B) staining for bacteria; by immunohistochemistry (IHC) to detect CD3, Swine leukocyte antigen class II DQ (SLAIIDQ), lysozyme, porcine reproductive and respiratory syndrome virus (PRRSV), swine influenza (SIV), Mycoplasma hyopneumoniae (Mhyo); and by in situ hybridization (ISH) to detect ssDNA and dsDNA of PCV2. PPV2 positive samples were subjected to in situ polymerase chain reaction (IS-PCR) including double staining method to detect PPV2 and host cell markers. To calculate statistical difference we used GENMOD or LOGISTIC procedures in Statistical Analysis System (SAS®).

Results

We found that the PPV2 was localized mostly in lymphocytes in lungs, lymph nodes and liver. Neither CD3 antigen nor lysozyme was expressed by these infected cells. In contrast, low levels of SLAIIDQ were expressed by infected cells, suggesting that PPV2 may have a specific tropism for immature B lymphocytes and/or NK lymphocytes though possibly not T lymphocytes.

Conclusion

The overall conclusion of this study indicates that PPV2 may contribute to the pathogenesis of pneumonia.

Electronic supplementary material

The online version of this article (10.1186/s12917-018-1487-z) contains supplementary material, which is available to authorized users.

Bone marrow laminins influence hematopoietic stem and progenitor cell cycling and homing to the bone marrow

Hematopoietic stem and progenitor cell (HSPC) functions are regulated by a specialized microenvironment in the bone marrow - the hematopoietic stem cell niche - of which the extracellular matrix (ECM) is an integral component. We describe here the localization of ECM molecules, in particular the laminin α4, α3 and α5 containing isoforms in the bone marrow. Laminin 421 (composed of laminin α4, β2, γ1 chains) is identified as a major component of the bone marrow ECM, occurring abundantly surrounding venous sinuses and in a specialized reticular fiber network of the intersinusoidal spaces of murine bone marrow (BM) in close association with HSPC. Bone marrow from Lama4^-/- mice is significantly less efficient in reconstituting the hematopoietic system of irradiated wildtype (WT) recipients in competitive bone marrow transplantation assays and shows reduced colony formation in vitro. This is partially due to retention of Lin^-c-kit⁺Sca-1⁺CD48^- long-term and short-term hematopoietic stem cells (LT-HSC/ST-HSC) in the G0 phase of the cell cycle in Lama4^-/- bone marrow and hence a more quiescent phenotype. In addition, the extravasation of WT BM cells into Lama4^-/- bone marrow is impaired, influencing the recirculation of HSPC. Our data suggest that these effects are mediated by a compensatory expression of laminin α5 containing isoforms (laminin 521/522) in Lama4^-/- bone marrow. Collectively, these intrinsic and extrinsic effects lead to reduced HSPC numbers in Lama4^-/- bone marrow and reduced hematopoietic potential.

Differentiation ability of multipotent hematopoietic stem/progenitor cells detected by a porcine specific anti-CD117 monoclonal antibody

CD117 is a cytokine receptor expressed on the surface of hematopoietic stem cells with a likely role in cell survival, proliferation and differentiation. In order to study the differentiation activity of porcine CD117 hematopoietic cells in vitro and in vivo we prepared an anti-swine CD117 Mab (2A1) with high specificity for flow-cytometrical analysis. The 2A1 Mab did not recognize mouse or human mast cells suggesting that 2A1 is species-specific. Swine bone marrow (BM) CD117+ cells differentiated in vitro mainly into erythroid and monocyte lineages in the methylcellulose-based colony assay. When the swine BM CD117+ cells were transplanted in vivo into immunodeficient NOG (NOD/SCID/IL-2gc-null) mice, a significant amount of swine CD45+ leukocytes, including CD3 positive T cells, were developed in the mice. These results revealed that the swine BM CD117+ cells possess hematopoietic stem/progenitor activity and when monitored in immunodeficient mice or in vitro they can develop into lymphoid, erythroid, and myeloid cells efficiently with the new monoclonal antibody.

Molecular and functional characterization of porcine Siglec-3/CD33 and analysis of its expression in blood and tissues

A cDNA clone encoding a 380 a-a type 1 transmembrane protein with homology to human Siglec-3/CD33 was obtained from a swine small intestine library. An analysis of protein sequence identified two immunoglobulin-like domains, a transmembrane region, and a carboxi-terminal tail with two tyrosine-based signalling motifs. Binding assays of Siglec-3 transfected CHO cells to polyacrylamide glycoconjugates showed a preference for α2-6-linked sialic acids. Using mAbs raised against a fragment containing the two Ig-like domains, porcine Siglec-3 was found to be expressed on monocytes and granulocytes, and their bone marrow precursors. It was also detected in lymph node, splenic and alveolar macrophages. MAbs immunoprecipitated, from granulocyte lysates, a protein of 51-60 kDa under both non-reducing and reducing conditions. MAbs were also used to analyse functional activity of Siglec-3 on bone marrow and blood cells. Engagement of Siglec-3 by mAb had no apparent effect on cell proliferation or cytokine production.

Development and characterisation of monoclonal antibodies reactive with porcine CSF1R (CD115)

Macrophage colony-stimulating factor (CSF1) controls the proliferation and differentiation of cells of the mononuclear phagocyte system. CSF1, alongside a second ligand, interleukin-34 (IL-34), acts by binding to a cell surface receptor (CSF1R). We previously cloned and expressed pig CSF1 and IL-34. Here we produced a pig CSF1R-Ig+pFUSE Fc fusion protein and used it as an immunogen to produce three monoclonal antibodies (ROS8G11, ROS3A5 and ROS3B10) targeted against porcine CSF1R. Specific binding of each monoclonal antibody was confirmed by ELISA, Western blot, flow cytometry and immunocytochemistry. The antibodies did not block CSF1 signalling. The surface expression of CSF1R in pig peripheral blood was restricted to CD14-positive monocytes and was also detected on lung macrophages. These antibodies provided an opportunity to investigate the increase of available CSF1R during pig BMDM differentiation. The new monoclonal antibodies provide useful reagents to support the study of monocyte and macrophage biology in the pig.

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.

Molecular characterization and expression of porcine Siglec-5

In this study we describe the characterization of the porcine orthologue of Siglec-5. A cDNa clone was obtained from a porcine cDNa library derived from swine small intestine which encodes a 555 a-a type 1 transmembrane protein with sequence homology to human Siglec-5. This protein consists of four Ig-like domains, a transmembrane region, and a cytoplasmic tail with two tyrosine-based signalling motifs. When expressed as a recombinant protein fused to the Fc region of human IgG1, porcine Siglec-5 was able to bind porcine red blood cells in a sialic acid-dependent manner. Monoclonal antibodies (mAb) were developed against porcine Siglec-5 and used to analyse its expression in bone marrow and blood cells, and lymphoid tissues. Porcine Siglec-5 expression was mainly restricted to myelomonocytic cells and their precursors, being detected also, although at low levels, on plasmacytoid dendritic cells and B lymphocytes. In lymphoid tissues, ellipsoids of the spleen and subcapsular and medullar sinuses of lymph nodes were positive for Siglec-5. These mAbs were able to precipitate, from granulocyte lysates, a protein of approximately 85 kDa under non-reducing conditions, indicating that porcine Siglec-5 is expressed as a monomer in the plasma membrane.

Ileal Peyer's patches are not necessary for systemic B cell development and maintenance and do not contribute significantly to the overall B cell pool in swine

Based on studies of sheep, ileal Peyer's patches (IPP) have been regarded as a type of primary lymphoid tissue similar to the bursa of Fabricius in chicken. Because bursectomy results in B cell deficiency, we wondered whether resection of the IPP of piglets would have a similar effect. Comparison of IPP-resected, surgical shams and untreated germ-free piglets, all of which were later colonized with a defined commensal flora, demonstrated that resection of the IPP did not alter the level and phenotype of B and T cells in lymphoid tissues and the blood 10 wk after surgery. Additionally, colonization of IPP caused a shift from the fetal type of lymphocyte distribution to the adult type that is characterized by prevalence of B cells, with many of them representing IgA(+) switched B cells or displaying a more mature CD2(-)CD21(+) and CD2(-)CD21(-) phenotype. Moreover, colonization leads to appearance of effector CD4(+)CD8(+) αβ T helper and CD2(+)CD8(-) γδ T cells. Comparison of germ-free with colonized pigs and experiments utilizing surgical transposition of jejunal Peyer's patch into terminal ileum or construction of isolated ileal loops indicated that lymphocyte development in IPP is dependent on colonization. Although our studies confirmed higher mitotic and apoptotic rates in IPP, they failed to identify any cell populations that resemble developing B lineage cells in the bone marrow. These results indicate that porcine IPP are not required for systemic B cell generation or maintenance, but they are secondary lymphoid tissue that appears important in immune responses to colonizing bacteria.

Convenient and efficient enrichment of the CD133+ liver cells from rat fetal liver cells as a source of liver stem/progenitor cells

Although the stem cells are commonly isolated by FACS or MACS, they are very expensive and these is no specific marker for liver stem/progentior cells (LSPCs). This paper applied a convenient and efficient method to enrich LSPCs. The fetal liver cells (FLCs) were firstly enriched by Percoll discontinuous gradient centrifugation (PDGC) from the rat fetal liver. Then the FLCs in culture were purified to be homogeneous in size by differential trypsinization and differential adherence (DTDA). Flow cytometric analysis revealed more than half of the purified FLCs expressed alternative markers of LSPCs (CD117, c-Met, Sca-1, CD90, CD49f and CD133). In other words, the purified FLCs were heterogeneous. Therefore, they were sequentially layered into six fractions by Percoll continuous gradient centrifugation (PCGC). Both CD133 and CD49f expressed decreasingly from fraction 1 to 6. In fraction 1 and 2, about 85% FLCs expressed CD133, which were revealed to be LSPCs by high expressions of AFP and CK-19, low expressions of G-6-P and ALB. To conclude, the purity of CD133(+) LSPCs enriched by combination of PDGC, DTDA and PCGC is close to that obtained by MACS. This study will greatly contribute to two important biological aspects: liver stem cells isolation and liver cell therapy.

Porcine Flt3 ligand and its receptor: generation of dendritic cells and identification of a new marker for porcine dendritic cells

Based on the known importance of Flt3 ligand (Flt3L) for the development of mouse dendritic cells (DCs), the present study compared the phenotype and function of DC derived from porcine bone marrow haematopoietic cells using either granulocyte-macrophage colony-stimulating factor or Flt3L (GMCSF-DC and Flt3L-DC, respectively). To this end, porcine Flt3L was cloned resulting in the identification of three isoforms of Flt3L. Compared to GMCSF-DC which were uniformly CD14(+), Flt3L-DC had a more diverse phenotype comprised of CD172a(-)CD11a(-) progenitor cells, CD172a(+)CD14(-)CD163(-) DC and CD172a(+)CD14(+)CD163(+) DC. In addition, only the Flt3L-DC contained interferon-producing plasmacytoid DC, although their frequency was low. Only the CD14(-) Flt3L-DC responded to TLR2, -3, -4, -7 and -9 agonists by upregulating CD80/86. This population of DC was also more potent in T-cell stimulation assays when compared to the CD14(+) counterpart. Interestingly, Flt3 was not only highly expressed on DC precursors, but also found on Flt3L-DC but not on GMCSF-DC or monocyte-derived DC. Furthermore, also DC circulating in the blood but not monocytes or other leukocytes expressed this receptor. Taken together, our study demonstrates that Flt3L-DCs are more suitable to study the interaction of pathogens with DC. Moreover, we show that also in the pig Flt3 remains expressed in a restricted manner on DC originating from a bone marrow DC precursors, typically representing steady-state DC in lymphoid tissue and blood.

Porcine myelomonocytic markers and cell populations

This review focuses in what is currently known about swine myeloid markers, the expression and function of these receptors in the biology of porcine myelomonocytic cells, the regulation of their expression along the different developmental stages of these cells and their utility to investigate the heterogeneity of monocyte and macrophage populations. Although the number of monoclonal antibodies recognizing surface antigens expressed on either swine granulocytes or monocytes is low compared with those available for human or mouse, they have contributed significantly to study the members of myeloid lineages in this species, allowing to discriminate different maturation stages of these cells in bone marrow and to reveal the heterogeneity of blood monocytes and tissue macrophages. Porcine myeloid cells share many similarities with humans, highlighting the relevance of the pig as a biomedical model.

Molecular genetics of the swine major histocompatibility complex, the SLA complex

The swine major histocompatibility complex (MHC) or swine leukocyte antigen (SLA) complex is one of the most gene-dense regions in the swine genome. It consists of three major gene clusters, the SLA class I, class III and class II regions, that span approximately 1.1, 0.7 and 0.5Mb, respectively, making the swine MHC the smallest among mammalian MHC so far examined and the only one known to span the centromere. This review summarizes recent updates to the Immuno Polymorphism Database-MHC (IPD-MHC) website (http://www.ebi.ac.uk/ipd/mhc/sla/) which serves as the repository for maintaining a list of all SLA recognized genes and their allelic sequences. It reviews the expression of SLA proteins on cell subsets and their role in antigen presentation and regulating immune responses. It concludes by discussing the role of SLA genes in swine models of transplantation, xenotransplantation, cancer and allergy and in swine production traits and responses to infectious disease and vaccines.