A novel approach to genetic engineering of T-cell subsets by hematopoietic stem cell infection with a bicistronic lentivirus.

Lentiviral modification of hematopoietic stem cells (HSCs) paved the way for in vivo experimentation and therapeutic approaches in patients with genetic disease. A disadvantage of this method is the use of a ubiquitous promoter leads not only to genetic modification of the leukocyte subset of interest e.g. T-cells, but also all other subsequent leukocyte progeny of the parent HSCs. To overcome this limitation we tested a bicistronic lentivirus, enabling subset specific modifications. Designed novel lentiviral constructs harbor a global promoter (mPGK) regulating mCherry for HSCs selection and a T-cell specific promoter upstream of eGFP. Two T-cell specific promoters were assessed: the distal Lck-(dLck) and the CD3δ-promoter. Transduced HSCs were FACS sorted by mCherry expression and transferred into sublethally irradiated C57/BL6 mice. Successful transplantation and T-cell specific expression of eGFP was monitored by peripheral blood assessment. Furthermore, recruitment response of lentiviral engineered leukocytes to the site of inflammation was tested in a peritonitis model without functional impairment. Our constructed lentivirus enables fast generation of subset specific leukocyte transgenesis as shown in T-cells in vivo and opens new opportunities to modify other HSCs derived subsets in the future.

Increased incidence of acute graft rejection on calcineurin inhibitor-free immunosuppression after heart transplantation.

BACKGROUND: Calcineurin inhibitor (CNI)-free immunosuppression is used increasingly after heart transplantation to avoid CNI toxicity, but in the absence of a randomized trial, concerns remain over an increased rejection risk. METHODS: We studied the incidence of graft rejection episodes among all cardiac graft recipients, beginning with the first introduction of CNI-free protocols. We compared events during CNI-free and CNI-containing immunosuppression among 231 transplant recipients of overall mean age 55.2 ± 11.8 years, from a mean 5.2 ± 5.4 years after transplantation through a mean follow-up of 3.1 ± 1.4 years. We considered as acute rejection episodes requiring treatment those of International Society for Heart and Lung Transplantation. RESULTS: During the total follow-up of 685 patient years (CNI-containing, 563; CNI-free, 122), we performed 1,374 biopsies which diagnosed 78 rejection episodes. More biopsies were performed in CNI-free patients: biopsies/patient-month of CNI-containing, 0.13 versus CNI-free, 0.22 (P < .05). The incidence of rejection episodes per patient-month was significantly higher on CNI-free compared with CNI therapy, among patients switched both early and later after heart transplantation, namely, within 1 year, 0.119 versus 0.035 (P = .02); beyond 1 year, 0.011 versus 0.004 (P = .007); beyond 2 years, 0.007 versus 0.003 (P = .04); and beyond 5 years: 0.00578 versus 0.00173 (P = .04). CONCLUSIONS: Rejection incidence during CNI-free immunosuppression protocols after heart transplantation was significantly increased in both early and later postoperative periods. Given the potentially long delay to rejection occurrence, patients should be monitored closely for several months after a switch to CNI-free immunosuppressive protocols.

Mitochondrial translocation of oxidized cofilin induces caspase-independent necrotic-like programmed cell death of T cells.

Oxidative stress leads to T-cell hyporesponsiveness or death. The actin-binding protein cofilin is oxidized during oxidative stress, which provokes a stiff actin cytoskeleton and T-cell hyporesponsiveness. Here, we show that long-term oxidative stress leads to translocation of cofilin into the mitochondria and necrotic-like programmed cell death (PCD) in human T cells. Notably, cofilin mutants that functionally mimic oxidation by a single mutation at oxidation-sensitive cysteins (Cys-39 or Cys-80) predominately localize within the mitochondria. The expression of these mutants alone ultimately leads to necrotic-like PCD in T cells. Accordingly, cofilin knockdown partially protects T cells from the fatal effects of long-term oxidative stress. Thus, we introduce the oxidation and mitochondrial localization of cofilin as the checkpoint for necrotic-like PCD upon oxidative stress as it occurs, for example, in tumor environments.

A novel flow-cytometry-based assay for quantification of affinity and avidity changes of integrins.

Cell adhesion plays an important role in cell-cell contact formation and cell migration. Thus, the assessment of cellular adhesiveness is one important feature when studying cell-mediated immune responses. The interaction of lymphocytes with other cell types such as antigen-presenting cells or vascular-endothelial cells occurs via adhesion molecules including L-selectin, VCAM-1 or ICAM-1. There are principally two mechanisms by which cell adhesion can be enhanced: namely changes in the affinity or avidity of receptor interactions. Conventional plate-based adhesion assays detect both forms. However, they do not permit discrimination between affinity- and avidity-mediated changes in the adhesiveness. Moreover, analysis of cell subpopulations requires cell separation prior to performance of the adhesion assay. Conventional flow-cytometry-based tests make it possible to determine changes in the affinity of integrins at the single cell level. However, they fail to quantify avidity-mediated adhesiveness. Here we describe a novel flow-cytometry-based assay, which allows the detection of both integrin-mediated affinity as well as avidity changes at the single cell level. This opens up the possibility of precisely characterizing the adhesive capacity of subpopulations in heterogeneous cell populations.