Monitoring of hematopoietic chimerism by real-time quantitative PCR of micro insertions/deletions in samples with low DNA quantities.

BACKGROUND: Sensitive and accurate methods to detect hematopoietic chimerism after hematopoietic stem cell transplantation (HSCT) are essential to evaluate engraftment and to monitor response to therapeutic procedures such as donor lymphocyte infusion. Continuous long-term follow up, however, requires large amounts of pre-HSCT samples limiting the application of many widely used techniques for sensitive chimerism monitoring. METHODS: DNAs from 42 normal healthy donors and 16 HSCT donor/recipient pairs were employed to validate the use of allele-specific insertion/deletion (indel) quantitative real-time polymerase chain reaction (qPCR) to quantify chimerism in samples with low amounts of DNA. Consequently, indel-qPCR analyses of samples from 16 HSCT patients were compared to short-tandem repeat (STR) specific PCR analyses. RESULTS: Typing with reduced amounts of input DNA (15 vs. 60 ng) allowed for the reliable distinction of positive (mean threshold cycle (ct) 28.05) and negative (ct >36) signals. The high informativity of primer/probe sets, with 12 out of 19 markers exceeding 20% informativity, was confirmed in our cohort (n = 74). Importantly, a fourfold reduction of input DNA compared to published protocols did not alter PCR efficiencies and allowed for a more sensitive detection of chimerism in 7 of 16 HSCT patients compared to results obtained by STR-PCR. CONCLUSIONS: Our data suggest that indel-qPCR is a more sensitive technique for the detection of hematopoietic chimerism compared to STR-PCR and works efficiently for samples with low amounts of DNA.

Delayed therapy with clopidogrel and everolimus prevents progression of transplant arteriosclerosis and impairs humoral alloimmunity in murine aortic allografts.

OBJECTIVES: It was previously shown that the combination of clopidogrel and everolimus reduced the development of transplant arteriosclerosis. The aim of this study was to investigate whether delayed onset of treatment, similar to the clinical situation after heart transplantation, inhibits progression of transplant arteriosclerosis. METHODS: Fully allogeneic C57BL/6 (H2-b) donor aortas were transplanted into CBA.J (H2-k) recipients treated with clopidogrel and everolimus alone or in combination starting on Days 1, 7 or 14. Grafts were analysed by histology and alloantibodies were detected by fluorescence activated cell sorting after transplantation. RESULTS: Delayed platelet inhibition with clopidogrel reduced the development of transplant arteriosclerosis [neointima formation (Day 14): 50±4 vs 84±9% (control)]. The combination of clopidogrel and everolimus almost abolished formation of transplant arteriosclerosis when therapy was started on Day 1 [neointima formation (Day 1): 14±5 vs 84±9% (control)] and also showed a remarkable reduction in both delayed treatment groups [neointima formation (Day 7): 24±7 vs 84±9% (control); neointima formation (Day 14): 28±11 vs 84±9% (control)]. Platelet inhibition alone and in combination with everolimus resulted in reduced alloantibody production. CONCLUSIONS: These results demonstrate that delayed treatment with clopidogrel and everolimus-representative of a clinical setting-prevents the progression of transplant arteriosclerosis and impairs humoral immunity in this experimental model.

Attenuation of transplant arteriosclerosis by oral feeding of major histocompatibility complex encoding chitosan-DNA nanoparticles.

One promising approach for the induction of transplant tolerance is the pre-treatment of transplant recipients with donor MHC-alloantigen. Our study focuses on the oral delivery of MHC-antigen encoding genes via chitosan-DNA nanoparticles to modulate the alloimmune response in order to reduce the development of transplant arteriosclerosis, the hallmark feature of chronic rejection after heart transplantation. Therefore, we performed fully allogeneic mouse abdominal aortic transplants using C57BL/6 (H2(b)) mice as donors and CBA.J (H2(k)) mice as recipients. Aortic grafts were analyzed by histology and morphometry on day 30 after transplantation, levels of circulating alloantibodies were detected by FACS analysis. Pre-treatment of recipient mice with chitosan-DNA nanoparticles encoding for K(b), one of the MHC-I molecules of the donor, resulted in a significant reduction of intimal proliferation compared to untreated controls. When Ovalbumin was fed instead of K(b) encoding nanoparticles (K(b)-NP) or Balb/c (H2(d)) grafts were used instead of C57BL/6 (H2(b)) grafts as antigen controls, both groups showed no reduction of intimal thickness indicating an antigen-specific mechanism. In addition, analysis of peripheral blood of the transplanted mice showed significant suppression of alloantibody formation in the K(b)-NP fed group compared to all other allogeneic transplanted groups suggesting modulation of the humoral immune response. These results demonstrate the potential of chitosan-DNA nanoparticles to induce K(b)-specific tolerance and to reduce the development of transplant arteriosclerosis.

Oral gene application using chitosan-DNA nanoparticles induces transferable tolerance.

Oral tolerance is a promising approach to induce unresponsiveness to various antigens. The development of tolerogenic vaccines could be exploited in modulating the immune response in autoimmune disease and allograft rejection. In this study, we investigated a nonviral gene transfer strategy for inducing oral tolerance via antigen-encoding chitosan-DNA nanoparticles (NP). Oral application of ovalbumin (OVA)-encoding chitosan-DNA NP (OVA-NP) suppressed the OVA-specific delayed-type hypersensitivity (DTH) response and anti-OVA antibody formation, as well as spleen cell proliferation following OVA stimulation. Cytokine expression patterns following OVA stimulation in vitro showed a shift from a Th1 toward a Th2/Th3 response. The OVA-NP-induced tolerance was transferable from donor to naïve recipient mice via adoptive spleen cell transfer and was mediated by CD4(+)CD25(+) T cells. These findings indicate that nonviral oral gene transfer can induce regulatory T cells for antigen-specific immune modulation.