A single-nucleotide polymorphism in the human ENTPD1 gene encoding CD39 is associated with worsened graft-versus-host disease in a humanized mouse model

Purinergic signalling in graft-versus-host disease

Allogeneic hematopoietic stem cell transplantation is used to treat blood cancers, but often results in lethal graft-versus-host disease (GVHD). GVHD is an inflammatory disorder mediated by donor leukocytes that damage host tissues. Purinergic signalling plays important roles in GVHD development in mice but studies of these pathways in human GVHD remain limited. P2X7 receptor activation by ATP on host antigen presenting cells contributes to the induction of GVHD, while activation of this receptor on regulatory T cells, myeloid-derived suppressor cells and possibly type 3 innate lymphoid cells results in their loss to promote GVHD progression. In contrast, A_2A receptor activation by adenosine on donor T cells serves to restrict GVHD development. These and other purinergic signalling molecules remain potential biomarkers and therapeutic targets in GVHD.

IL-4 prevents adenosine-mediated immunoregulation by inhibiting CD39 expression

The ectonucleotidase CD39 functions as a checkpoint in purinergic signaling on effector T cells. By depleting eATP and initiating the generation of adenosine, it impairs memory cell development and contributes to T cell exhaustion, thereby causing defective tumor immunity and deficient T cell responses in older adults who have increased CD39 expression. Tuning enzymatic activity of CD39 and targeting the transcriptional regulation of ENTPD1 can be used to modulate purinergic signaling. Here, we describe that STAT6 phosphorylation downstream of IL-4 signaling represses CD39 expression on activated T cells by inducing a transcription factor network including GATA3, GFI1, and YY1. GATA3 suppresses ENTPD1 transcription through prevention of RUNX3 recruitment to the ENTPD1 promoter. Conversely, pharmacological STAT6 inhibition decreases T cell effector functions via increased CD39 expression, resulting in the defective signaling of P2X receptors by ATP and stimulation of A2A receptors by adenosine. Our studies suggest that inhibiting the STAT6 pathway to increase CD39 expression has the potential to treat autoimmune disease while stimulation of the pathway could improve T cell immunity.

Humanized Mouse Model to Study the P2X7 Receptor in Graft-Versus-Host Disease

Humanized mouse models of graft-versus-host disease (GVHD), where human immune cells are injected into immune deficient mice, are well established and provide opportunities to investigate pathways involved in GVHD development. This chapter provides an overview of human immune cell isolation, injection of these cells into immune deficient mice, monitoring of mice for signs of GVHD, and assessment of human cell engraftment using flow cytometry. Further, this chapter focuses on the P2X7 signaling pathway involved in GVHD, and describes a strategy to block the P2X7 receptor and examine the effect of this on GVHD development.

The oral histopathological and immunological characteristics of a xenogeneic mouse chronic graft-versus-host disease model

BACKGROUND

Oral lesions are important clinical manifestations of chronic graft-verse-host disease (cGVHD). However, the oral characteristics of cGVHD mouse model are not yet clear. This study aims to demonstrate oral histopathological and immunological characteristics of a xenogeneic cGVHD mouse model.

MATERIALS AND METHODS

2.5 × 10⁶ , 5.0 × 10⁶ , 7.5 × 10⁶ , and 10.0 × 10⁶  human peripheral blood mononuclear cells (hPBMCs) were intravenously transplanted into NCG mice to induce cGVHD. After transplantation, clinical observations were recorded. Tissue samples from salivary glands and oral mucosa were stained with H&E, Masson Trichrome, and immunofluorescence, and the histopathology of oral tissues was scored according to our modified criteria.

RESULTS

NCG mice showed signs of cGVHD onset after transplantation. The oral histopathological lesion incidences in each group were 37.50%, 50.00%, 62.50%, and 75.00%, respectively. Oral histopathological lesion incidence and histopathological scores were positively correlated with the amount of infused hPBMCs. Epithelial atrophy, epithelial cells vacuolar degeneration, and basal cells liquefaction denaturation were observed in oral mucosa, and acinar destruction and collagen deposition were observed in the salivary glands. Human CD45⁺ , CD4⁺ , CD8⁺ , IL-17⁺ , and FoxP3⁺ cells infiltrated into oral tissues. In the 5.0 × 10⁶  hPBMCs group, oral histopathological changes mainly began between days 30 and 45 post-transplantation, and became more severe after day 45. The oral histopathological scores also gradually increased.

CONCLUSION

Inflammation in oral mucosa epithelium and salivary glands, and CD4⁺ and CD8⁺ T cells dominating infiltration are the main oral features in the xenogeneic cGVHD mouse model. The severity of oral histopathological lesions shows a dose and time correlation. These may be helpful to oral cGVHD research.

Limited TCR repertoire and ENTPD1 dysregulation mark late-stage COVID-19

T cell exhaustion and dysfunction are hallmarks of severe COVID-19. To gain insights into the pathways underlying these alterations, we performed a comprehensive transcriptome analysis of peripheral-blood-mononuclear-cells (PBMCs), spleen, lung, kidney, liver, and heart obtained at autopsy from COVID-19 patients and matched controls, using the nCounter CAR-T-Characterization panel. We found substantial gene alterations in COVID-19-impacted organs, especially the lung where altered TCR repertoires are noted. Reduced TCR repertoires are also observed in PBMCs of severe COVID-19 patients. ENTPD1/CD39, an ectoenzyme defining exhausted T-cells, is upregulated in the lung, liver, spleen, and PBMCs of severe COVID-19 patients where expression positively correlates with markers of vasculopathy. Heightened ENTPD1/CD39 is paralleled by elevations in STAT-3 and HIF-1α transcription factors; and by markedly reduced CD39-antisense-RNA, a long-noncoding-RNA negatively regulating ENTPD1/CD39 at the post-transcriptional level. Limited TCR repertoire and aberrant regulation of ENTPD1/CD39 could have permissive roles in COVID-19 progression and indicate potential therapeutic targets to reverse disease.

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Transcriptome profiling of COVID-19 autoptic tissue and PBMC was carried out

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There is limited TCR repertoire in lung, kidney and PBMC of severe COVID-19 cases

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There are increased CD39 levels in PBMC of severe COVID-19 patients

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High HIF-1a and STAT-3 and low CD39-antisense might be linked with CD39 increase

Purinergic Signalling in Allogeneic Haematopoietic Stem Cell Transplantation and Graft-versus-Host Disease

Allogeneic haematopoietic stem cell transplantation (allo-HSCT) is a curative therapy for blood cancers and other haematological disorders. However, allo-HSCT leads to graft-versus-host disease (GVHD), a severe and often lethal immunological response, in the majority of transplant recipients. Current therapies for GVHD are limited and often reduce the effectiveness of allo-HSCT. Therefore, pro- and anti-inflammatory factors contributing to disease need to be explored in order to identify new treatment targets. Purinergic signalling plays important roles in haematopoiesis, inflammation and immunity, and recent evidence suggests that it can also affect haematopoietic stem cell transplantation and GVHD development. This review provides a detailed assessment of the emerging roles of purinergic receptors, most notably P2X7, P2Y2 and A2A receptors, and ectoenzymes, CD39 and CD73, in GVHD.

CD39 Regulation and Functions in T Cells

CD39 is an enzyme which is responsible, together with CD73, for a cascade converting adenosine triphosphate into adenosine diphosphate and cyclic adenosine monophosphate, ultimately leading to the release of an immunosuppressive form of adenosine in the tumor microenvironment. Here, we first review the environmental and genetic factors shaping CD39 expression. Second, we report CD39 functions in the T cell compartment, highlighting its role in regulatory T cells, conventional CD4⁺ T cells and CD8⁺ T cells. Finally, we compile a list of studies, from preclinical models to clinical trials, which have made essential contributions to the discovery of novel combinatorial approaches in the treatment of cancer.

Post-transplant cyclophosphamide limits reactive donor T cells and delays the development of graft-versus-host disease in a humanized mouse model

Graft-versus-host disease (GVHD) is a major complication of allogeneic haematopoietic stem cell transplantation (allo-HSCT) that develops when donor T cells in the graft become reactive against the host. Post-transplant cyclophosphamide (PTCy) is increasingly used in mismatched allo-HSCT, but how PTCy impacts donor T cells and reduces GVHD is unclear. This study aimed to determine the effect of PTCy on reactive human donor T cells and GVHD development in a preclinical humanized mouse model. Immunodeficient NOD-scid-IL2Rγ^null mice were injected intraperitoneally (i.p.) with 20 × 10⁶ human peripheral blood mononuclear cells stained with carboxyfluorescein succinimidyl ester (CFSE) (day 0). Mice were subsequently injected (i.p.) with PTCy (33 mg kg^-1 ) (PTCy-mice) or saline (saline-mice) (days 3 and 4). Mice were assessed for T-cell depletion on day 6 and monitored for GVHD for up to 10 weeks. Flow cytometric analysis of livers at day 6 revealed lower proportions of reactive (CFSE^low ) human (h) CD3⁺ T cells in PTCy-mice compared with saline-mice. Over 10 weeks, PTCy-mice showed reduced weight loss and clinical GVHD, with prolonged survival and reduced histological liver GVHD compared with saline-mice. PTCy-mice also demonstrated increased splenic hCD4⁺ :hCD8⁺ T-cell ratios and reduced splenic Tregs (hCD4⁺  hCD25⁺  hCD127^lo ) compared with saline-mice. This study demonstrates that PTCy reduces GVHD in a preclinical humanized mouse model. This corresponded to depletion of reactive human donor T cells, but fewer human Tregs.

Comparison of peripheral blood mononuclear cell isolation techniques and the impact of cryopreservation on human lymphocytes expressing CD39 and CD73

CD39 and CD73 are ecto-nucleotidases present on human peripheral blood mononuclear cells (PBMCs) and are emerging biomarkers on these cells in various disorders including cancer. Many factors influence PBMC quality, so it is essential to validate sample processing methods prior to incorporation in clinical studies. This study examined the impact of both PBMC cryopreservation and PBMC isolation using SepMate density gradient centrifugation on CD39 and CD73 expressing subsets. First, PBMCs were isolated from the peripheral blood of 11 healthy donors by routine Ficoll-Paque density gradient centrifugation, cryopreserved and compared with freshly isolated PBMCs by flow cytometry. The proportions of T and B cells expressing combinations of CD39 and CD73 were relatively stable over 6-month cryopreservation, although some T cell combinations revealed small but significant changes. Second, peripheral blood was collected from six healthy donors to compare PBMCs isolated by SepMate or Ficoll-Paque density gradient centrifugation. Compared with Ficoll-Paque, the more rapid SepMate method yielded 9.1% less PBMCs but did not alter cell viability or proportions of T and B cells expressing combinations of CD39 and CD73. The present study reveals that cryopreservation is suitable for studying T and B cells expressing combinations of CD39 and CD73. However, caution should be exercised when observing small differences in these cryopreserved subsets between different cohorts. Further, SepMate and Ficoll-Paque methods of PBMC isolation show similar results for T and B cell subset analysis; however, SepMate is a faster and easier approach.