Human Placenta-Derived Mesenchymal Stromal-Like Cells Enhance Angiogenesis via T Cell-Dependent Reprogramming of Macrophage Differentiation.

Peripheral arterial disease (PAD) is a leading cause of limb loss and mortality worldwide with limited treatment options. Mesenchymal stromal cell (MSC) therapy has demonstrated positive effects on angiogenesis in preclinical models and promising therapeutic efficacy signals in early stage clinical studies; however, the mechanisms underlying MSC-mediated angiogenesis remain largely undefined. Here, we investigated the mechanism of action of human placenta-derived MSC-like cells (PDA-002) in inducing angiogenesis using mice hind limb ischemia model. We showed that PDA-002 improved blood flow and promoted collateral vessel formation in the injured limb. Histological analysis demonstrated that PDA-002 increased M2-like macrophages in ischemic tissue. Analysis of the changes in functional T cell phenotype in the draining lymph nodes revealed that PDA-002 treatment was associated with the induction of cytokine and gene expression signatures of Th2 response. Angiogenic effect of PDA-002 was markedly reduced in Balb/c nude mice compared with wild type. This reduction in efficacy was reversed by T cell reconstitution, suggesting T cells are essential for PDA-002-mediated angiogenesis. Furthermore, effect of PDA-002 on macrophage differentiation was also T cell-dependent as a PDA-002-mediated M2-like macrophage skewing was only observed in wild type and T cell reconstituted nude mice, but not in nude mice. Finally, we showed that PDA-002-treated animals had enhanced angiogenic recovery in response to the second injury when PDA-002 no longer persisted in vivo. These results suggest that PDA-002 enhances angiogenesis through an immunomodulatory mechanism involving T cell-dependent reprogramming of macrophage differentiation toward M2-like phenotype. Stem Cells 2017;35:1603-1613.

Clinical Scale Zinc Finger Nuclease-mediated Gene Editing of PD-1 in Tumor Infiltrating Lymphocytes for the Treatment of Metastatic Melanoma.

Programmed cell death-1 (PD-1) is expressed on activated T cells and represents an attractive target for gene-editing of tumor targeted T cells prior to adoptive cell transfer (ACT). We used zinc finger nucleases (ZFNs) directed against the gene encoding human PD-1 (PDCD-1) to gene-edit melanoma tumor infiltrating lymphocytes (TIL). We show that our clinical scale TIL production process yielded efficient modification of the PD-1 gene locus, with an average modification frequency of 74.8% (n = 3, range 69.9-84.1%) of the alleles in a bulk TIL population, which resulted in a 76% reduction in PD-1 surface-expression. Forty to 48% of PD-1 gene-edited cells had biallelic PD-1 modification. Importantly, the PD-1 gene-edited TIL product showed improved in vitro effector function and a significantly increased polyfunctional cytokine profile (TNFα, GM-CSF, and IFNγ) compared to unmodified TIL in two of the three donors tested. In addition, all donor cells displayed an effector memory phenotype and expanded approximately 500-2,000-fold in vitro. Thus, further study to determine the efficiency and safety of adoptive cell transfer using PD-1 gene-edited TIL for the treatment of metastatic melanoma is warranted.

Bovine mammary dendritic cells: a heterogeneous population, distinct from macrophages and similar in phenotype to afferent lymph veiled cells.

Dendritic cells (DC) are a heterogeneous population of professional antigen presenting cells and are potent stimulators of naïve T-cells. However, there is little previous research describing DC in bovine mammary tissue, primarily because of the difficulty distinguishing these cells from macrophages, which possess a similar phenotype. Using immunohistofluorescence and a combination of markers (MHC-II, CD205, CD11c), DC were localized in the bovine mammary gland and supramammary lymph node. In mammary tissue DC were found within the alveolar epithelium and within the intralobular connective tissue. In the lymph node DC were found on the periphery of B-cell areas, in the cortex, and among T-cells in the paracortex and medulla. DC in mammary parenchyma and supramammary lymph nodes were quantified and further characterized using flow cytometry. DC were CD11c(hi), CD14(lo) cells that expressed MHC-II and CD205. DC could be distinguished from macrophages based on their low CD14 expression. This research provides a better understanding of mammary gland immunology, while potentially aiding in the targeting of antigens to mucosal DC for vaccine development.

Targeting mucosal immunity in the battle to develop a mastitis vaccine.

The mucosal immune system encounters antigens that enhance and suppress immune function, and serves as a selective barrier against invading pathogens. The mammary gland not only encounters antigens but also produces a nutrient evolved to protect and enhance mucosal development in the neonate. Efforts to manipulate antibody concentrations in milk to prevent mastitis, an infection of the mammary gland, have been hampered both by complexity and variation in target pathogens and limited knowledge of cellular immunity in the gland. Successful vaccination strategies must overcome the natural processes that regulate types and concentrations of milk antibodies for neonatal development, and enhance cellular immunity. Furthermore, the need to overcome dampening of immunity caused by non-pathogenic encounters to successfully prevent establishment of infection is an additional obstacle in vaccine development at mucosal sites. A significant mastitis pathogen, Staphylococcus aureus, not only resides as a normal flora on a multitude of species, but also causes clinical disease with limited treatment options. Using the bovine model of S. aureus mastitis, researchers can decipher the role of antigen selection and presentation by mammary dendritic cells, enhance development of central and effector memory function, and subsequently target specific memory cells to the mammary gland for successful vaccine development. This brief review provides an overview of adaptive immunity, previous vaccine efforts, current immunological findings relevant to enhancing immune memory, and research technologies that show promise in directing future vaccine efforts to enhance mammary gland immunity and prevent mastitis.