Caractériser l'épuisement lymphocytaire T global ou donneur-spécifique après transplantation rénale : analyse phénotypique et fonctionnelle

L'utilisation d'une immunosuppression (IS) au long cours reste indispensable après transplantation, même si le phénotype des rejets se modifie avec le délai de greffe. Cependant, les complications liées à la sur- IS (néoplasies, infections...), ou sous- IS (rejet aigu ou chronique) réduisent toujours la survie des patients ou des greffons. Améliorer la compréhension des mécanismes lymphocytaires impliqués dans les modifications des réponses allo-spécifiques ou non spécifiques après greffe est importante pour individualiser la prescription des immunosuppresseurs et limiter leurs complications. Une altération des fonctions lymphocytaires T peut survenir au cours des mécanismes allo-immuns, ou sous traitement immunosuppresseur au long cours. L'épuisement lymphocytaire T (ELT) caractérise un état de dysfonction affectant les lymphocytes T mémoires, dans des situations de stimulation chronique avec persistance de l'exposition à un antigène. Cet état est caractérisé par une baisse des capacités prolifératives ou fonctionnelles de ces cellules, et la co-expression de récepteurs inhibiteurs (RIs). Bien que des modèles murins aient récemment souligné le rôle de l'ELT dans le rejet de greffe, cet état dysfonctionnel reste peu étudié. Dans une première étude, nous avons analysé l'expression de 3 RIs classiquement associés à l'ELT (2B4 (CD244), Programmed cell Death protein (PD)-1), et CD160, au cours du traitement par anti-PD1 (nivolumab) de 3 transplantés rénaux présentant une leucoencéphalopathie multifocale progressive. L'analyse des RIs dans les CD4+ et CD8+ a montré des taux élevés d'expression de 2B4, PD-1, et CD160 avant traitement, suggérant un ELT. Après traitement, seule l'expression de PD-1 diminuait, alors que les autres RIs n'étaient pas affectés par l'utilisation du traitement, suggérant la persistance de cet dysfonction lymphocytaire. Par la suite, nous avons cherché par une étude transversale à caractériser l'ELT dans une population de patients exposés à de forts niveaux d'IS, les patients greffés avec anticorps spécifiques du donneur préformés (greffes HLA incompatibles, HLAi). Ces patients recevaient tous une induction par sérum anti-lymphocytaire et rituximab, ainsi qu'un traitement de maintenance par tacrolimus, acide mycophenolique, et corticoides. Afin de comparer l'expression des RIs (PD-1, Tigit, 2B4) et les capacités de production cytokinique (IFNgamma, TNFalpha, IL2) de ces patients, nous avons utilisé un groupe de patients greffés en incompatibilité ABO (greffes ABOi) recevant un traitement d'induction et de maintenance similaire, mais exposé à un antigène dont la réponse est T-indépendante. Nous avons pu observer une augmentation de la co-expression des récepteurs inhibiteurs dans le groupe de patients HLAi en comparaison aux patients ABOi. Particulièrement, Tigit présentait un niveau d'expression dans les CD4 et CD8 du groupe HLAi plus élevé comparativement aux ABOi. De plus, alors que Tigit était négativement corrélé aux capacités fonctionnelles des LT du groupe ABOi, toute corrélation était perdue dans le groupe HLAi. Ces données suggèrent que l'ELT au cours de la reconstitution lymphocytaire serait plus important après greffe HLAi, ce qui est cohérent avec le niveau élevé de complications infectieuses et néoplasiques décrites après ce type de greffe. Dans une deuxième étude transversale portant sur des patients transplantés rénaux, libres de toute complication infectieuse, néoplasique, allo-immune, et sous traitement immunosuppresseur standard, nous avons montré une corrélation positive entre le délai de greffe et l'expression de Tigit dans les CD4 mémoires, alors que la proportion de cellules CD4+ TIGIT-CD226+ diminuait. L'analyse fonctionnelle de ces cellules nous a permis de montrer une dysfonction de l'axe Tigit/CD226 au cours du temps dans les CD4 mémoires. Dans les CD8 mémoires, nous avons pu montrer un profil dysfonctionnel de ces cellules, associé à une augmentation d'expression des cellules CD8+PD-1+Tigit+. La réponse allo-spécifique (approchée par réaction lymphocytaire mixte) était diminuée en comparaison à la réponse non-spécifique, et corrélée au pourcentage de cellules mémoires CD4+Tigit+CD226+Tim3-PD-1-2B4- avant stimulation. Enfin, nous avons étudié les différences immunologiques T et B au cours de formes modérées et graves du COVID-19 chez des patients transplantés d'organe solide, et montré des différences immunologiques majeures au sein des différents compartiments entre les deux groupes. Par ces différents travaux nous avons montré que l'ELT pourrait être impliqué dans la diminution progressive des rejets T-médiés après greffe. La caractérisation d'une signature d'ELT post greffe pour limiter les complications liées à l'IS parait utile pour améliorer les résultats post-transplantation.Kidney transplantation requires the long-term use of immunosuppressive therapy (IT) even if a modification of rejections phenotype with time was previously noted. However, patient and graft survival remain entailed by over-IT (e.g cancer and infections), or under-IT (e.g acute or chronic rejections) complications. A better comprehension of immune mechanisms involved in changes concerning global or allo-specific responses is a key point to improve the individualization of IT and decrease IT-related complications. Several dysfunctional states could occur during allo-immune response, or on long-term immunosuppressive therapy. T cell exhaustion (TCE) is a dysfunctional state affecting memory T cells during chronic stimulation due to the persistent exposure of a high load of foreign antigen. This state is characterized by a decrease proliferative capacity, reduced production of cytokines, and is associated with co-expression of inhibitory receptors (IRs) expression. Murine models of solid organ transplantation suggested a role for T cell exhaustion. However, until now this dysfunctional state is barely studied after transplantation. We first analyzed the expression of 3 IRs classically associated with T cell exhaustion (2B4 (CD244), Programmed cell Death protein (PD)-1), and CD160), in 3 kidney transplant recipients treated with anti-PD1 (nivolumab) therapy for progressive multifocal leukoencephalopathy. Before treatment, we observed a high-level expression of IRs in both CD4 and CD8+ T cells, suggesting T cell exhaustion. After treatment, PD-1 expression, but not of others IRs, decreased, suggesting the persistence of this dysfunctional state, strengthened by the absence of clinical improvement. We next investigated TCE in a cross-sectional study in a highly immunocompromised population, patients with preformed donor-specific antibodies (HLA incompatible, HLAi). All included patients received anti-lymphocyte globulins and anti-20 antibodies (rituximab), followed by a maintenance therapy (tacrolimus, mycophenolic acid, and steroids). We compared IRs expression ( PD-1, Tigit, 2B4) and cytokine production (IFNgamma, TNFalpha, IL2) of these patients to ABO incompatible recipients that received the same induction and maintenance therapy, but was exposed to a T-independent response antigen. We observed an increased co-expression of IRs in the HLAi group comparing with ABOi. Especially, Tigit expression was expressed in higher levels by CD4+ and CD8+ T cells in HLAi comparing with ABOi. Moreover, while Tigit was as expected negatively correlated with functional capacities in ABOi patients, we did not observe any correlation between Tigit expression and function in HLAi recipients. These data suggest that TCE during reconstitution of HLAi patients would be more important than in ABOi recipients, which is consistent with the higher rate of infectious and neoplastic complications previously reported in this group. Thereafter, we performed a second cross-sectional study a living-donor kidney transplant recipients, free from infectious, neoplastic, alloimmune complications, and receiving a standard immunosuppressive maintenance therapy (no induction, maintenance with tacrolimus, mycophenolic acid, steroids). We observed a positive correlation between time post transplantation and Tigit expression in memory CD4+ T cells, while the proportion of CD4+Tigit-CD226+ decreased. Functional analysis of these cells revealed a dysfunctional state of Tigit/ CD226 axis with time post transplantation in memory CD4. In memory CD8+ T cells, we observed a dysfunctional profile of these cells with time post transplantation, associated with an increased proportion of CD8+PD-1+Tigit+ cells. Donor-specific response, investigated by the mean of mixed lymphocyte reaction, was reduced comparing with third-parties responses, and was correlated to the percentage of CD4+Tigit+CD226+Tim3-PD-1-2B4- before stimulation. Finally, we studied T and B cells differences during moderate and severe forms of COVID-19 in solid organ transplant recipients. We observed accurate immunological differences between mild and severe forms (lower CD3+ and CD8+ T cells number, higher proportion of activated CD4+ T cells and lower proportion of regulatory T cells, NK cells, and transitional B cells in severe forms). This work suggests that TCE could be involved in the progressive decrease of T cell rejection post transplantation. Characterizing a post-transplant TCE signature to reduce immunosuppression-related complication appears to be usefull to improve post-transplant outcomes

An Association between BK Virus Replication in Bone Marrow and Cytopenia in Kidney-Transplant Recipients

The human polyomavirus BK (BKV) is associated with severe complications, such as ureteric stenosis and polyomavirus-associated nephropathy (PVAN), which often occur in kidney-transplant patients. However, it is unknown if BKV can replicate within bone marrow. The aim of this study was to search for BKV replication within the bone marrow of kidney-transplant patients presenting with a hematological disorder. Seventy-two kidney-transplant patients underwent bone-marrow aspiration for cytopenia. At least one virus was detected in the bone marrow of 25/72 patients (35%), that is, parvovirus B19 alone (n = 8), parvovirus plus Epstein-Barr virus (EBV) (n = 3), cytomegalovirus (n = 4), EBV (n = 2), BKV alone (n = 7), and BKV plus EBV (n = 1). Three of the eight patients who had BKV replication within the bone marrow had no detectable BKV replication in the blood. Neutropenia was observed in all patients with BKV replication in the bone marrow, and blockade of granulocyte maturation was observed. Hematological disorders disappeared in all patients after doses of immunosuppressants were reduced. In conclusion, an association between BKV replication in bone marrow and hematological disorders, especially neutropenia, was observed. Further studies are needed to confirm these findings

Impaired antigen-specific B-cell responses after Influenza vaccination in kidney transplant recipients receiving co-stimulation blockade with Belatacept

Inhibidores de la calcineurina; Vacunación antigripal; Trasplante de riñónCalcineurin inhibitors; Influenza vaccination; Kidney transplantationInhibidors de la calcineurina; Vacunació antigripal; Trasplantament de ronyóEmerging data suggest that costimulation blockade with belatacept effectively controls humoral alloimmune responses. However, whether this effect may be deleterious for protective anti-infectious immunity remains poorly understood. We performed a mechanistic exploratory study in 23 kidney transplant recipients receiving either the calcineurin-inhibitor tacrolimus (Tac, n=14) or belatacept (n=9) evaluating different cellular immune responses after influenza vaccination such as activated T follicular Helper (Tfh), plasmablasts and H1N1 hemagglutinin (HA)-specific memory B cells (HA+mBC) by flow-cytometry, and anti-influenza antibodies by hemagglutination inhibition test (HI), at baseline and days 10, 30 and 90 post-vaccination. The proportion of CD4+CD54RA-CXCR5+ Tfh was lower in belatacept than Tac patients at baseline (1.86%[1.25-3.03] vs 4.88%[2.40-8.27], p=0.01) and remained stable post-vaccination. At M3, HA+mBc were significantly higher in Tac-treated patients (0.56%[0.32-1.49] vs 0.27%[0.13-0.44], p=0.04) and correlated with activated Tfh numbers. When stratifying patients according to baseline HA+mBc frequencies, belatacept patients with low HA+mBC displayed significantly lower HA+mBc increases after vaccination than Tac patients (1.28[0.94-2.4] vs 2.54[1.73-5.70], p=0.04). Also, belatacept patients displayed significantly lower seroprotection rates against H1N1 at baseline than Tac-treated patients (44.4% vs 84.6%) as well as lower seroconversion rates at days 10, 30 and 90 after vaccination (50% vs 0%, 63.6% vs 0%, and 63.6% vs 0%, respectively). We show the efficacy of belatacept inhibiting T-dependent antigen-specific humoral immune responses, active immunization should be highly encouraged before starting belatacept therapy.This work was supported by the Instituto de Salud Carlos III (ISCIII) (grant numbers ICI14/00242 and PI16/01321, PI19/01710) and by the European Union’s Horizon 2020 Research and innovation program (grant agreement 754995). Also, this work was partly supported by the SLT002/16/00183 grant, from the Department of Health of the Generalitat de Catalunya by the call “Accioí instrumental de programes derecerca orientats en l’àmbit de la recerca i la innovacioí en salut.” The authors thank the Research Centers of Catalonia (CERCA) Programme/Generalitat de Catalunya for institutional support. OB was awarded with an intensification grant from the “Instituto de Salud Carlos III” [INT19/00051]

Case Report Beneficial Effect of Conversion to Belatacept in Kidney-Transplant Patients with a Low Glomerular-Filtration Rate

Belatacept has been found to be efficient at preserving good kidney function in maintenance kidney-transplant patients. Herein, we report on the use of belatacept as a rescue therapy for two kidney-transplant patients presenting with severe adverse events after treatment with calcineurin inhibitors (CNIs) and mammalian target-of-rapamycin (mTOR) inhibitors. Two kidney-transplant patients developed severely impaired kidney function after receiving CNIs. The use of everolimus was associated with severe angioedema. Belatacept was then successfully used to improve kidney function in both cases, even though estimated glomerularfiltration rate before conversion was <20 mL/min. These case reports show that belatacept can be used as a rescue therapy, even if kidney function is very low in kidney-transplant patients who cannot tolerate CNIs and/or mTOR inhibitors

Impaired antigen-specific B-cell responses after Influenza vaccination in kidney transplant recipients receiving co-stimulation blockade with Belatacept

Emerging data suggest that costimulation blockade with belatacept effectively controls humoral alloimmune responses. However, whether this effect may be deleterious for protective anti-infectious immunity remains poorly understood. We performed a mechanistic exploratory study in 23 kidney transplant recipients receiving either the calcineurin-inhibitor tacrolimus (Tac, n=14) or belatacept (n=9) evaluating different cellular immune responses after influenza vaccination such as activated T follicular Helper (Tfh), plasmablasts and H1N1 hemagglutinin (HA)-specific memory B cells (HA(+)mBC) by flow-cytometry, and anti-influenza antibodies by hemagglutination inhibition test (HI), at baseline and days 10, 30 and 90 post-vaccination. The proportion of CD4+CD54RA-CXCR5+ Tfh was lower in belatacept than Tac patients at baseline (1.86%[1.25-3.03] vs 4.88%[2.40-8.27], p=0.01) and remained stable post-vaccination. At M3, HA(+)mBc were significantly higher in Tac-treated patients (0.56%[0.32-1.49] vs 0.27%[0.13-0.44], p=0.04) and correlated with activated Tfh numbers. When stratifying patients according to baseline HA(+)mBc frequencies, belatacept patients with low HA(+)mBC displayed significantly lower HA(+)mBc increases after vaccination than Tac patients (1.28[0.94-2.4] vs 2.54[1.73-5.70], p=0.04). Also, belatacept patients displayed significantly lower seroprotection rates against H1N1 at baseline than Tac-treated patients (44.4% vs 84.6%) as well as lower seroconversion rates at days 10, 30 and 90 after vaccination (50% vs 0%, 63.6% vs 0%, and 63.6% vs 0%, respectively). We show the efficacy of belatacept inhibiting T-dependent antigen-specific humoral immune responses, active immunization should be highly encouraged before starting belatacept therapy

Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis

BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London

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

BLOOM: A 176B-Parameter Open-Access Multilingual Language Model

Large language models (LLMs) have been shown to be able to perform new tasks based on a few demonstrations or natural language instructions. While these capabilities have led to widespread adoption, most LLMs are developed by resource-rich organizations and are frequently kept from the public. As a step towards democratizing this powerful technology, we present BLOOM, a 176B-parameter open-access language model designed and built thanks to a collaboration of hundreds of researchers. BLOOM is a decoder-only Transformer language model that was trained on the ROOTS corpus, a dataset comprising hundreds of sources in 46 natural and 13 programming languages (59 in total). We find that BLOOM achieves competitive performance on a wide variety of benchmarks, with stronger results after undergoing multitask prompted finetuning. To facilitate future research and applications using LLMs, we publicly release our models and code under the Responsible AI License

Surgical site infection after gastrointestinal surgery in high-income, middle-income, and low-income countries: a prospective, international, multicentre cohort study

Background: Surgical site infection (SSI) is one of the most common infections associated with health care, but its importance as a global health priority is not fully understood. We quantified the burden of SSI after gastrointestinal surgery in countries in all parts of the world. Methods: This international, prospective, multicentre cohort study included consecutive patients undergoing elective or emergency gastrointestinal resection within 2-week time periods at any health-care facility in any country. Countries with participating centres were stratified into high-income, middle-income, and low-income groups according to the UN's Human Development Index (HDI). Data variables from the GlobalSurg 1 study and other studies that have been found to affect the likelihood of SSI were entered into risk adjustment models. The primary outcome measure was the 30-day SSI incidence (defined by US Centers for Disease Control and Prevention criteria for superficial and deep incisional SSI). Relationships with explanatory variables were examined using Bayesian multilevel logistic regression models. This trial is registered with ClinicalTrials.gov, number NCT02662231. Findings: Between Jan 4, 2016, and July 31, 2016, 13 265 records were submitted for analysis. 12 539 patients from 343 hospitals in 66 countries were included. 7339 (58·5%) patient were from high-HDI countries (193 hospitals in 30 countries), 3918 (31·2%) patients were from middle-HDI countries (82 hospitals in 18 countries), and 1282 (10·2%) patients were from low-HDI countries (68 hospitals in 18 countries). In total, 1538 (12·3%) patients had SSI within 30 days of surgery. The incidence of SSI varied between countries with high (691 [9·4%] of 7339 patients), middle (549 [14·0%] of 3918 patients), and low (298 [23·2%] of 1282) HDI (p < 0·001). The highest SSI incidence in each HDI group was after dirty surgery (102 [17·8%] of 574 patients in high-HDI countries; 74 [31·4%] of 236 patients in middle-HDI countries; 72 [39·8%] of 181 patients in low-HDI countries). Following risk factor adjustment, patients in low-HDI countries were at greatest risk of SSI (adjusted odds ratio 1·60, 95% credible interval 1·05–2·37; p=0·030). 132 (21·6%) of 610 patients with an SSI and a microbiology culture result had an infection that was resistant to the prophylactic antibiotic used. Resistant infections were detected in 49 (16·6%) of 295 patients in high-HDI countries, in 37 (19·8%) of 187 patients in middle-HDI countries, and in 46 (35·9%) of 128 patients in low-HDI countries (p < 0·001). Interpretation: Countries with a low HDI carry a disproportionately greater burden of SSI than countries with a middle or high HDI and might have higher rates of antibiotic resistance. In view of WHO recommendations on SSI prevention that highlight the absence of high-quality interventional research, urgent, pragmatic, randomised trials based in LMICs are needed to assess measures aiming to reduce this preventable complication