Allo-HLA Cross-Reactivities of Cytomegalovirus-, Influenza-, and Varicella Zoster Virus-Specific Memory T Cells Are Shared by Different Healthy Individuals.

Virus-specific T cells can recognize allogeneic HLA (allo-HLA) through TCR cross-reactivity. The allospecificity often differs by individual (private cross-reactivity) but also can be shared by multiple individuals (public cross-reactivity); however, only a few examples of the latter have been described. Because these could facilitate alloreactivity prediction in transplantation, we aimed to identify novel public cross-reactivities of human virus-specific CD8+ T cells directed against allo-HLA by assessing their reactivity in mixed-lymphocyte reactions. Further characterization was done by studying TCR usage with primer-based DNA sequencing, cytokine production with ELISAs, and cytotoxicity with 51 chromium-release assays. We identified three novel public allo-HLA cross-reactivities of human virus-specific CD8+ T cells. CMV B35/IPS CD8+ T cells cross-reacted with HLA-B51 and/or HLA-B58/B57 (23% of tetramer-positive individuals), FLU A2/GIL (influenza IMP[58-66] HLA-A*02:01/GILGFVFTL) CD8+ T cells with HLA-B38 (90% of tetramer-positive individuals), and VZV A2/ALW (varicella zoster virus IE62[593-601] HLA-A*02:01/ALWALPHAA) CD8+ T cells with HLA-B55 (two unrelated individuals). Cross-reactivity was tested against different cell types including endothelial and epithelial cells. All cross-reactive T cells expressed a memory phenotype, emphasizing the importance for transplantation. We conclude that public allo-HLA cross-reactivity of virus-specific memory T cells is not uncommon and may create novel opportunities for alloreactivity prediction and risk estimation in transplantation.

Virus-Specific CD8(+) T Cells Cross-Reactive to Donor-Alloantigen Are Transiently Present in the Circulation of Kidney Transplant Recipients Infected With CMV and/or EBV.

T cells play a dual role in transplantation: They mediate transplant rejection and are crucial for virus control. Memory T cells generated in response to pathogens can cross-react to alloantigen, a phenomenon called heterologous immunity. Virus-specific CD8(+) T cells cross-reacting to donor-alloantigen might affect alloimmune responses and hamper tolerance induction following transplantation. Here, we longitudinally studied these cross-reactive cells in peripheral blood of 25 kidney transplant recipients with a cytomegalovirus and/or Epstein-Barr virus infection. Cross-reactive T cells were identified by flow cytometry as virus-specific T cells that proliferate in response to donor cells in a mixed-lymphocyte reaction. In 13 of 25 patients, we found cross-reactivity to donor cells for at least 1 viral epitope before (n = 7) and/or after transplantation (n = 8). Cross-reactive T cells were transiently present in the circulation, and their precursor frequency did not increase following transplantation or viral infection. Cross-reactive T cells expressed interferon-γ and CD107a in response to both alloantigen and viral peptide and resembled virus-specific T cells in phenotype and function. Their presence was not associated with impaired renal function, proteinuria, or rejection. In conclusion, virus-specific T cells that cross-react to donor-alloantigen are transiently detectable in the circulation of kidney transplant recipients.

Treatment with everolimus is associated with a procoagulant state.

INTRODUCTION: Renal transplant recipients are at increased risk of venous thromboembolic events, which is in part caused by their treatment with maintenance immunosuppressive drugs. Because we observed an increased incidence of venous thromboembolic events in renal transplant recipients treated with the mTOR inhibitor (mTORi) everolimus, we aimed to identify prothrombotic mechanisms of this immunosuppressive drug. MATERIALS AND METHODS: In a single center study, nested in a multi-center randomized controlled trial, we measured parameters of coagulation, anti-coagulation and fibrinolysis in renal transplant recipients, receiving the mTORi everolimus (n=16, mTOR group) and compared them to a similar patient group, receiving a calcineurin inhibitor and/or mycophenolate sodium (n=20, non-mTOR group). All patients were at least 6 months following transplantation with a stable transplant function. RESULTS: The use of an mTORi was associated with significantly higher levels of von Willebrand factor, prothrombin fragment 1+2, thrombin-activatable fibrinolysis inhibitor and plasminogen activator inhibitor-1 as compared to a non-mTORi based immunosuppressive regimen. CONCLUSIONS: Treatment with an mTORi leads to increased endothelial activation, thrombin formation and impaired fibrinolysis in renal transplant recipients. This suggests an increased risk of thrombotic events in renal transplant recipients treated with mTOR inhibitors. A prospective study to establish the precise risk of thrombotic events in these patients is urgently needed.

BK virus infection in transplant recipients: clinical manifestations, treatment options and the immune response.

Polyomavirus BK (BKV) is ubiquitously present amongst the general population establishing a latent, seemingly asymptomatic infection in immunocompetent individuals. In transplant recipients, however, BKV reactivation is common and can lead to distinctive pathological entities in different patient groups: in renal transplant (RT) recipients, it is associated with nephropathy (BKVN) and ureteral stenosis, and in haematopoietic stem cell transplant (HSCT) recipients with haemorrhagic cystitis (HC). Furthermore, BKV employs several potentially oncogenic mechanisms to promote its replication in cells and has been inconsistently linked to the development of malignancies. BKVN is currently a major cause of allograft failure in RT recipients. HC causes prolonged hospital stay and increased mortality in HSCT recipients. Despite its discovery more than 40 years ago, few advances have been made with regard to therapeutic strategies. Current therapies aim to restore the impaired immune response, e.g. by lowering immunosuppressive agents in RT recipients. However, this is a double-edged sword since it also increases the chance of rejection. Therefore, more specific and effective treatment strategies are urgently needed. Here, we will review the current knowledge on the structure and lifecycle of BKV, characteristics of the BKV-specific immune response, its clinical manifestations and the strengths and limitations of available treatments Polyomavirus BK (BKV) is ubiquitously present amongst the general population establishing a latent, seemingly asymptomatic infection in immunocompetent individuals. In transplant recipients, however, BKV reactivation is common and can lead to distinctive pathological entities in different patient groups: in renal transplant (RT) recipients, it is associated with nephropathy (BKVN) and ureteral stenosis, and in haematopoietic stem cell transplant (HSCT) recipients with haemorrhagic cystitis (HC). Furthermore, BKV employs several potentially oncogenic mechanisms to promote its replication in cells and has been inconsistently linked to the development of malignancies. BKVN is currently a major cause of allograft failure in RT recipients. HC causes prolonged hospital stay and increased mortality in HSCT recipients. Despite its discovery more than 40 years ago, few advances have been made with regard to therapeutic strategies. Current therapies aim to restore the impaired immune response, e.g. by lowering immunosuppressive agents in RT recipients. However, this is a double-edged sword since it also increases the chance of rejection. Therefore, more specific and effective treatment strategies are urgently needed. Here, we will review the current knowledge on the structure and lifecycle of BKV, characteristics of the BKV-specific immune response, its clinical manifestations and the strengths and limitations of available treatments methods.

The proof of analytical chemical education lies in proficiency testing: a proficiency testing programme in polytechnic academia and vocational colleges in The Netherlands.

Participation in proficiency testing schemes (PT-schemes) is an important way to prove and to improve the skills of analytical chemical students. It gives valuable information on the professional capabilities of the students and is thus an important step in the training of laboratory engineers and technicians. In the programme described three types of samples are offered to the students: chemical, environmental and clinical samples. A guiding protocol presents instructions to the participating student groups. Standard operating procedures are available, but the students are also free to select their own method. The results are methodologically and statistically judged by professional PT-organisers and are presented in the customary way: the dataset, the mean (consensus) value of all participants and the Z-scores. The final presentation of the results takes place in an annual symposium where awards are presented to the best performing student groups, and a lecture programme is presented with subjects in the area of quality assurance and quality control. A selection of results from the KILO/PT/1998-1999 and the KILO/PT/1999-2000 programme is presented.