Requirement of Cognate CD4+ T-Cell Recognition for the Regulation of Allospecific CTL by Human CD4+CD127−CD25+FOXP3+ Cells Generated in MLR

Although immunoregulation of alloreactive human CTLs has been described, the direct influence of CD4+ Tregs on CD8+ cytotoxicity and the interactive mechanisms have not been well clarified. Therefore, human CD4+CD127−CD25+FOXP3+ Tregs were generated in MLR, immunoselected and their allospecific regulatory functions and associated mechanisms were then tested using modified 51Chromium release assays (Micro-CML), MLRs and CFSE-based multi-fluorochrome flow cytometry proliferation assays. It was observed that increased numbers of CD4+CD127−CD25+FOXP3+ cells were generated after a 7 day MLR. After immunoselection for CD4+CD127−CD25+ cells, they were designated as MLR-Tregs. When added as third component modulators, MLR-Tregs inhibited the alloreactive proliferation of autologous PBMC in a concentration dependent manner. The inhibition was quasi-antigen specific, in that the inhibition was non-specific at higher MLR-Treg modulator doses, but non-specificity disappeared with lower numbers at which specific inhibition was still significant. When tested in micro-CML assays CTL inhibition occurred with PBMC and purified CD8+ responders. However, antigen specificity of CTL inhibition was observed only with unpurified PBMC responders and not with purified CD8+ responders or even with CD8+ responders plus Non-T “APC”. However, allospecificity of CTL regulation was restored when autologous purified CD4+ T cells were added to the CD8+ responders. Proliferation of CD8+ cells was suppressed by MLR-Tregs in the presence or absence of IL-2. Inhibition by MLR-Tregs was mediated through down-regulation of intracellular perforin, granzyme B and membrane-bound CD25 molecules on the responding CD8+ cells. Therefore, it was concluded that human CD4+CD127−CD25+FOXP3+ MLR-Tregs down-regulate alloreactive cytotoxic responses. Regulatory allospecificity, however, requires the presence of cognate responding CD4+ T cells. CD8+ CTL regulatory mechanisms include impaired proliferation, reduced expression of cytolytic molecules and CD25+ activation epitopes

Outcomes of immunosuppression minimization and withdrawal early after liver transplantation

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149209/1/ajt15205.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149209/2/ajt15205_am.pd

Mass spectrometry-based proteomics for advancing solid organ transplantation research

Scarcity of high-quality organs, suboptimal organ quality assessment, unsatisfactory pre-implantation procedures, and poor long-term organ and patient survival are the main challenges currently faced by the solid organ transplant (SOT) field. New biomarkers for assessing graft quality pre-implantation, detecting, and predicting graft injury, rejection, dysfunction, and survival are critical to provide clinicians with invaluable prediction tools and guidance for personalized patients' treatment. Additionally, new therapeutic targets are also needed to reduce injury and rejection and improve transplant outcomes. Proteins, which underlie phenotypes, are ideal candidate biomarkers of health and disease statuses and therapeutic targets. A protein can exist in different molecular forms, called proteoforms. As the function of a protein depends on its exact composition, proteoforms can offer a more accurate basis for connection to complex phenotypes than protein from which they derive. Mass spectrometry-based proteomics has been largely used in SOT research for identification of candidate biomarkers and therapeutic intervention targets by so-called “bottom-up” proteomics (BUP). However, such BUP approaches analyze small peptides in lieu of intact proteins and provide incomplete information on the exact molecular composition of the proteins of interest. In contrast, “Top-down” proteomics (TDP), which analyze intact proteins retaining proteoform-level information, have been only recently adopted in transplantation studies and already led to the identification of promising proteoforms as biomarkers for organ rejection and dysfunction. We anticipate that the use of top-down strategies in combination with new technological advancements in single-cell and spatial proteomics could drive future breakthroughs in biomarker and therapeutic target discovery in SOT

An interferon-free antiviral regimen for HCV after liver transplantation.

Background Hepatitis C virus (HCV) infection is the leading indication for liver transplantation worldwide, and interferon-containing regimens are associated with low response rates owing to treatment-limiting toxic effects in immunosuppressed liver-transplant recipients. We evaluated the interferon-free regimen of the NS5A inhibitor ombitasvir coformulated with the ritonavir-boosted protease inhibitor ABT-450 (ABT-450/r), the nonnucleoside NS5B polymerase inhibitor dasabuvir, and ribavirin in liver-transplant recipients with recurrent HCV genotype 1 infection. Methods We enrolled 34 liver-transplant recipients with no fibrosis or mild fibrosis, who received ombitasvir-ABT-450/r (at a once-daily dose of 25 mg of ombitasvir, 150 mg of ABT-450, and 100 mg of ritonavir), dasabuvir (250 mg twice daily), and ribavirin for 24 weeks. Selection of the initial ribavirin dose and subsequent dose modifications for anemia were at the investigator's discretion. The primary efficacy end point was a sustained virologic response 12 weeks after the end of treatment. Results Of the 34 study participants, 33 had a sustained virologic response at post-treatment weeks 12 and 24, for a rate of 97% (95% confidence interval, 85 to 100). The most common adverse events were fatigue, headache, and cough. Five patients (15%) required erythropoietin; no patient required blood transfusion. One patient discontinued the study drugs owing to adverse events after week 18 but had a sustained virologic response. Blood levels of calcineurin inhibitors were monitored, and dosages were modified to maintain therapeutic levels; no episode of graft rejection was observed during the study. Conclusions Treatment with the multitargeted regimen of ombitasvir-ABT-450/r and dasabuvir with ribavirin was associated with a low rate of serious adverse events and a high rate of sustained virologic response among liver-transplant recipients with recurrent HCV genotype 1 infection, a historically difficult-to-treat populatio

Banff 2022 liver group meeting report: monitoring long term allograft health.

The Banff Working Group on Liver Allograft Pathology met in September 2022. Participantsincluded hepatologists, surgeons, pathologists, immunologists and histocompatibility specialists.Presentations and discussions focused on the evaluation of long-term allograft health, including noninvasive and tissue monitoring, immunosuppression optimisation and long-term structural changes.Potential revision of the rejection classification scheme to better accommodate and communicate lateT cell-mediated rejection patterns and related structural changes, such as nodular regenerativehyperplasia, were discussed. Improved stratification of long-term maintenance immunosuppression tomatch the heterogeneity of patient settings will be central to improving long-term patient survival.Such personalised therapeutics are in turn contingent on better understanding and monitoring ofallograft status within a rational decision-making approach, likely to be facilitated in implementationwith emerging decision support tools. Proposed revisions to rejection classification emerging fromthe meeting include incorporation of interface hepatitis and fibrosis staging. These will be opened toonline testing, modified accordingly and subject to consensus discussion leading up to the next Banffconference

Transplanting livers from HCV‐infected donors into HCV‐negative recipients: Promise but mind the pitfalls

This editorial points out the important findings of the work by Kwong et al (page 1380) while highlighting the ethical concerns of their approach and potential pitfalls if performed on a broader scale