Propriétés des anticorps anti-HLA en transplantation d'organes

IgG HLA antibodies are a cause of graft loss in organ transplantation. The single antigen flow beadsassays (SAFB) are the most precise and sensitive assays to identify donor specific HLA antibodies(DSA) in recipient’s sera. Their semi-quantitative readout, the mean fluorescence intensity (MFI), is notperfectly associated with graft outcomes, which could be due to several factors.Firstly, we showed that class I SAFB frequently detects denatured class I HLA antibodies which areunable to bind cell surface and then are clinically irrelevant, while they actually impact the access to atransplant. Their identification was performed through SAFB acid-treatment and a modified SAFBassay, the iBeads®. They had a high reliability and a good concordance, but the acid-treatment assaycan be put at fault in a few cases whereas iBeads® appeared slightly less sensitive than classicalSAFB. Secondly, we deciphered the complement interference phenomenon: high MFI level IgG HLAantibodies activate the complement cascade at bead surface, leading to the deposition of C4 and C3degradation products which are able to reduce IgG HLA antibodies detection. We also demonstratedthat IgM HLA antibodies interfere with IgG detection through competition for the epitope, allosterichindrance and complement activation. Thirdly, we demonstrated that the detection of DSA with SAFB in lung biopsy eluates, proving that theDSA interact with the graft, was a risk factor for graft loss. We further developed a capture system insurface plasmon resonance allowing the concentration and affinity of HLA antibodies to bedetermined, which could allow the way that the DSA interact with the graft to be studied.Les anticorps anti-HLA d’isotype IgG sont une cause de perte de greffon en transplantation d’organes.Les tests « single antigen » (SAFB) sont les outils les plus précis et sensibles pour l’identification desanticorps anti-HLA dirigés contre le donneur (DSA) dans le sérum des receveurs. Leur résultat semiquantitatif,la MFI, n’est pas parfaitement associé à l’issue clinique, ce qui pourrait être dû à plusieursraisons. Premièrement, nous avons montré que les SAFB de classe I détectent fréquemment des anticorpsanti-HLA dénaturé de classe I, incapables de se lier à la surface cellulaire et donc n’ayant pas designification clinique, alors qu’ils ont un impact négatif sur l’accès à la transplantation. Leuridentification a été réalisée par un traitement acide des billes et par un SAFB modifié, les iBeads®.Ces deux tests montraient de bonnes fiabilité et concordance, mais le traitement acide pouvait parfoisêtre mis en défaut alors que les iBeads® auraient une sensibilité légèrement inférieure aux SAFBclassiques. Deuxièmement, nous avons déchiffré l’interférence liée au complément : les IgG anti-HLA de forte MFIsont capables d’activer le complément à la surface des billes, conduisant à une accumulation desproduits de dégradation du C4 et du C3, capables de réduire la détection des IgG anti-HLA. Nousavons également démontré que les IgM anti-HLA étaient capables d’interférer avec la détection desIgG à travers une compétition pour l’épitope, un encombrement stérique et une activation ducomplément. Troisièmement, nous avons montré que la détection des DSA avec les SAFB dans les éluats debiopsies de poumons transplantés, preuve formelle que ces DSA interagissent avec le greffon,constituait un facteur de risque de perte du greffon. Nous avons également développé un système decapture en résonance plasmonique de surface permettant de déterminer la concentration et l’affinitédes anticorps anti-HLA, ce qui pourrait permettre d’étudier la façon dont les DSA interagissent avec legreffon

Urban food forestry (UFF), its role in Canadian urban forestry management plans, and integration into Thunder Bay, Ontario

Urban food forests are perennial polycultures of fruit or nut-producing tree species that mimic a natural ecosystem. The concept of urban food forestry within small grassroots campaigns and initiatives is not a new one, but has until recently gained some recognition in Canadian urban forest management plans. Even so, its role in urban forest management plans remains poorly understood. An analysis of 10 contextual search terms and themes related to urban food forestry within 25 Canadian urban forest management plans was conducted to better understand its role. It was determined that the mention of urban food forestry was distributed unevenly and disproportionately with no discernible pattern. Discussions surrounding existing urban food forestry initiatives within Canada were then mentioned to adopt a framework to help address food insecurity in Thunder Bay

Exploring community-based suicide prevention in the context of rural Australia : a qualitative study

Suicide rates in rural communities are higher than in urban areas, and communities play a crucial role in suicide prevention. This study explores community-based suicide prevention using a qualitative research design. Semi-structured interviews and focus groups asked participants to explore community-based suicide prevention in the context of rural Australia. Participants recruited ((n = 37; ages 29–72, Mean = 46, SD = 9.56); female 62.2%; lived experience 48.6%) were self-identified experts, working in rural community-based suicide prevention (community services, program providers, research, and policy development) around Australia. Data were thematically analysed, identifying three themes relating to community-based suicide prevention: (i) Community led initiatives; (ii) Meeting community needs; and (iii) Programs to improve health and suicidality. Implementing community-based suicide prevention needs community-level engagement and partnerships, including with community leaders; gatekeepers; community members; people with lived experience; services; and professionals, to “get stuff done”. Available resources and social capital are utilised, with co-created interventions reflecting diverse lifestyles, beliefs, norms, and cultures. The definition of “community”, community needs, issues, and solutions need to be identified by communities themselves. Primarily non-clinical programs address determinants of health and suicidality and increase community awareness of suicide and its prevention, and the capacity to recognise and support people at risk. This study shows how community-based suicide prevention presents as a social innovation approach, seeing suicide as a social phenomenon, with community-based programs as the potential driver of social change, equipping communities with the “know how” to implement, monitor, and adjust community-based programs to fit community needs

C5b9 Deposition in Glomerular Capillaries Is Associated With Poor Kidney Allograft Survival in Antibody-Mediated Rejection

C4d deposition in peritubular capillaries (PTC) reflects complement activation in antibody-mediated rejection (ABMR) of kidney allograft. However, its association with allograft survival is controversial. We hypothesized that capillary deposition of C5b9—indicative of complement-mediated injury—is a severity marker of ABMR. This pilot study aimed to determine the frequency, location and prognostic impact of these deposits in ABMR. We retrospectively selected patients diagnosed with ABMR in two French transplantation centers from January 2005 to December 2014 and performed C4d and C5b9 staining by immunohistochemistry. Fifty-four patients were included. Median follow-up was 52.5 (34.25–73.5) months. Thirteen patients (24%) had C5b9 deposits along glomerular capillaries (GC). Among these, seven (54%) had a global and diffuse staining pattern. Twelve of the C5b9+ patients also had deposition of C4d in GC and PTC. C4d deposits along GC and PTC were not associated with death-censored allograft survival (p = 0.42 and 0.69, respectively). However, death-censored allograft survival was significantly lower in patients with global and diffuse deposition of C5b9 in GC than those with a segmental pattern or no deposition (median survival after ABMR diagnosis, 6 months, 40.5 months and 44 months, respectively; p = 0.015). Double contour of glomerular basement membrane was diagnosed earlier after transplantation in C5b9+ ABMR than in C5b9– ABMR (median time after transplantation, 28 vs. 85 months; p = 0.058). In conclusion, we identified a new pattern of C5b9+ ABMR, associated with early onset of glomerular basement membrane duplication and poor allograft survival. Complement inhibitors might be a therapeutic option for this subgroup of patients

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Analysis of anti-human CD22 human mAbs affinity and specificity on human PBMCs. a) Affinity determination of anti-human CD22 mAbs using SPR by flowing various concentration of CD22 antibody over CD22 chip-bound. b) Flow cytometry analysis of CD22 mAbs on human PBMC. Human PBMC were labeled with anti human CD19 (APC) and purified CD22 mAbs (clone γ1λ1, γ3λ3-5, γ23κ5-2 or γ27λ26) coupled with Alexa Fluor 568 fluorochrome or with a commercial mouse mAb anti-human CD22 (Ms anti-human CD22). (PPT 666 kb

Biomedicines

Antibody-mediated rejection (ABMR) is the leading cause of allograft failure in kidney transplantation. Its histological hallmark is represented by lesions of glomerulitis i.e., inflammatory cells within glomeruli. Current therapies for ABMR fail to prevent chronic allograft damage i.e., transplant glomerulopathy, leading to allograft loss. We used laser microdissection of glomeruli from formalin-fixed allograft biopsies combined with mass spectrometry-based proteomics to describe the proteome modification of 11 active and 10 chronic active ABMR cases compared to 8 stable graft controls. Of 1335 detected proteins, 77 were deregulated in glomerulitis compared to stable grafts, particularly involved in cellular stress mediated by interferons type I and II, leukocyte activation and microcirculation remodeling. Three proteins extracted from this protein profile, TYMP, WARS1 and GBP1, showed a consistent overexpression by immunohistochemistry in glomerular endothelial cells that may represent relevant markers of endothelial stress during active ABMR. In transplant glomerulopathy, 137 proteins were deregulated, which favor a complement-mediated mechanism, wound healing processes through coagulation activation and ultimately a remodeling of the glomerular extracellular matrix, as observed by light microscopy. This study brings novel information on glomerular proteomics of ABMR in kidney transplantation, and highlights potential targets of diagnostic and therapeutic interest

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Properties of HLA antibodies in organ transplantation

Les anticorps anti-HLA d’isotype IgG sont une cause de perte de greffon en transplantation d’organes.Les tests « single antigen » (SAFB) sont les outils les plus précis et sensibles pour l’identification desanticorps anti-HLA dirigés contre le donneur (DSA) dans le sérum des receveurs. Leur résultat semiquantitatif,la MFI, n’est pas parfaitement associé à l’issue clinique, ce qui pourrait être dû à plusieursraisons. Premièrement, nous avons montré que les SAFB de classe I détectent fréquemment des anticorpsanti-HLA dénaturé de classe I, incapables de se lier à la surface cellulaire et donc n’ayant pas designification clinique, alors qu’ils ont un impact négatif sur l’accès à la transplantation. Leuridentification a été réalisée par un traitement acide des billes et par un SAFB modifié, les iBeads®.Ces deux tests montraient de bonnes fiabilité et concordance, mais le traitement acide pouvait parfoisêtre mis en défaut alors que les iBeads® auraient une sensibilité légèrement inférieure aux SAFBclassiques. Deuxièmement, nous avons déchiffré l’interférence liée au complément : les IgG anti-HLA de forte MFIsont capables d’activer le complément à la surface des billes, conduisant à une accumulation desproduits de dégradation du C4 et du C3, capables de réduire la détection des IgG anti-HLA. Nousavons également démontré que les IgM anti-HLA étaient capables d’interférer avec la détection desIgG à travers une compétition pour l’épitope, un encombrement stérique et une activation ducomplément. Troisièmement, nous avons montré que la détection des DSA avec les SAFB dans les éluats debiopsies de poumons transplantés, preuve formelle que ces DSA interagissent avec le greffon,constituait un facteur de risque de perte du greffon. Nous avons également développé un système decapture en résonance plasmonique de surface permettant de déterminer la concentration et l’affinitédes anticorps anti-HLA, ce qui pourrait permettre d’étudier la façon dont les DSA interagissent avec legreffon.IgG HLA antibodies are a cause of graft loss in organ transplantation. The single antigen flow beadsassays (SAFB) are the most precise and sensitive assays to identify donor specific HLA antibodies(DSA) in recipient’s sera. Their semi-quantitative readout, the mean fluorescence intensity (MFI), is notperfectly associated with graft outcomes, which could be due to several factors.Firstly, we showed that class I SAFB frequently detects denatured class I HLA antibodies which areunable to bind cell surface and then are clinically irrelevant, while they actually impact the access to atransplant. Their identification was performed through SAFB acid-treatment and a modified SAFBassay, the iBeads®. They had a high reliability and a good concordance, but the acid-treatment assaycan be put at fault in a few cases whereas iBeads® appeared slightly less sensitive than classicalSAFB. Secondly, we deciphered the complement interference phenomenon: high MFI level IgG HLAantibodies activate the complement cascade at bead surface, leading to the deposition of C4 and C3degradation products which are able to reduce IgG HLA antibodies detection. We also demonstratedthat IgM HLA antibodies interfere with IgG detection through competition for the epitope, allosterichindrance and complement activation. Thirdly, we demonstrated that the detection of DSA with SAFB in lung biopsy eluates, proving that theDSA interact with the graft, was a risk factor for graft loss. We further developed a capture system insurface plasmon resonance allowing the concentration and affinity of HLA antibodies to bedetermined, which could allow the way that the DSA interact with the graft to be studied

Clinical relevance of donor-specific antibodies directed at HLA-C: A long road to acceptance

In solid organ transplantation (SOT), the clinical relevance of donor-specific antibodies (DSA) directed at anti-HLA-A, -B, -DR and -DQ antigens is largely recognized while it is still a matter of debate for DSA directed at HLA-C. In this review, we summarize the peculiarities of HLA-C among class I HLA antigens as well as their immunogenicity, which underlie the clinical relevance of HLA-C locus and anti-HLA-C DSA in SOT. Many factors, both intrinsic and extrinsic to the HLA-C gene and HLA-C protein, explain its lower expression in comparison with HLA-A and -B. This lower expression can explain the apparent lower immunogenicity of HLA-C leading to a lower prevalence and strength of anti-HLA-C antibodies. Nevertheless, HLA-C antigens are truly immunogenic and preformed anti-HLA-C DSA are clinically relevant. Indeed, anti-HLA-C DSA are able to bind donor cells and to activate the complement pathway both ex vivo and in vivo. In line with this, numerous clinical studies now show that preformed DSA directed at native HLA-C molecules induce poorer graft outcomes. We then plead for the inclusion of HLA-C in all transplant allocation systems and we propose a strategy to cope with anti-HLA-C DSA in SOT. Beyond SOT, anti-HLA-C antibodies generate a growing interest in the allo-HCT, transfusion and obstetrics fields, while new concepts such as the role of the « missing-self » in solid organ rejection places HLA-C as an inescapable actor in transplant tolerance