[CAR-T therapy for autoimmune diseases]. / Thérapie cellulaire CAR-T dans le traitement des maladies auto-immunes.

Cellular therapy using genetically modified T lymphocytes expressing synthetic receptors, known as CAR (Chimeric Antigen Receptor), has revolutionized the treatment of certain hematologic malignancies. This success has led to exploring the same approach in the treatment of severe autoimmune diseases refractory to conventional therapies. Initial results in systemic lupus erythematosus have shown complete remissions that appear to persist over time. Consequently, there is a growing number of ongoing clinical trials. In this review, we discuss the rationale behind the use of CAR-T therapies, the targeted autoimmune diseases, and the associated risks.

La thérapie cellulaire à base de lymphocytes T génétiquement modifiés exprimant des récepteurs synthétiques ou CAR (récepteur antigénique chimérique) a révolutionné le traitement de certaines maladies hémato-oncologiques. Ce succès a conduit à l'exploration de la même approche dans le traitement de maladies auto-immunes sévères et réfractaires aux thérapies conventionnelles. Les premiers résultats obtenus dans le lupus érythémateux systémique ont montré des rémissions complètes semblant persister dans le temps. Nous assistons donc actuellement à une prolifération importante d'essais cliniques. Dans cet article, nous abordons le rationnel derrière l'utilisation des thérapies CAR-T, les maladies auto-immunes ciblées, mais aussi les risques associés.

[Cardiac sarcoidosis: a diagnostic and therapeutic challenge]. / Sarcoïdose cardiaque : un défi diagnostique et thérapeutique.

The diagnosis of cardiac sarcoidosis, particularly in its isolated cardiac form, represents a major challenge due to non-specific symptoms and the limited sensitivity and specificity of basic cardiac investigations. MRI and metabolic PET-CT are important elements in the diagnostic process. Corticosteroids remain the cornerstone for the treatment of the inflammatory phase, in association with biological agents and steroid-sparing therapies. The goal is to limit the progression of fibrosis, which is a source of malignant arrhythmias and heart failure. The indication for implantation of a cardiac defibrillator must be carefully evaluated to reduce the risk of sudden death. Multidisciplinary collaboration is essential for optimal care.

Le diagnostic de sarcoïdose cardiaque, en particulier dans sa forme cardiaque isolée, représente un défi majeur en raison de symptômes aspécifiques et d'une sensibilité et spécificité limitées des explorations cardiologiques de base. L'IRM et le PET-CT métabolique sont devenus des éléments essentiels dans le processus diagnostique. Les corticostéroïdes restent la pierre angulaire du traitement dans la phase inflammatoire, parallèlement aux agents biologiques et aux thérapies d'épargne cortisonique. L'objectif est d'éviter la progression vers la fibrose, source d'arythmies malignes et d'insuffisance cardiaque. L'indication à l'implantation d'un défibrillateur cardiaque doit être soigneusement évaluée afin de réduire le risque de mort subite. Une collaboration multidisciplinaire est essentielle afin d'assurer une prise en charge optimale.

[Idiopathic recurrent pericarditis: review of the literature and the Geneva experience]. / Péricardite récurrente idiopathique : revue de littérature et expérience genevoise.

The notion of idiopathic recurrent pericarditis (IRP) appeared in the scientific literature in the 1930s. In 1955, W. Dressler published a case series of IRP in which treatment of cortisone and salicylates (i.e. Aspirin) was effective. About 30 years later, De La Serna et al. in 1987 and Guindo et al. in 1990, reported a beneficial effect of colchicine. In recent years, several clinical studies have helped to i mprove the management of this disease. In this present literature review of IRP, we will focus on the definition, differential diagnoses, pathophysiological hypotheses and available treatments. We will also discuss the clinical experience at the division of clinical immunology at the University Hospitals of Geneva.

La notion de péricardite récurrente idiopathique (PRI) apparaît dans la littérature scientifique dans les années 1930. En 1955, Dressler publie une série de cas de PRI où les traitements de cortisone et les salicylates (c'est-à-dire l'aspirine) semblent être efficaces. Environ 30 ans plus tard, De La Serna et coll., en 1987, et Guindo et coll., en 1990, évoquent un effet bénéfique de la colchicine. Depuis le développement clinique moderne, plusieurs études ont permis de faire évoluer la prise en charge de cette entité. Dans cette revue de littérature de la PRI, nous nous intéressons à la définition, aux diagnostics différentiels, aux hypothèses physiopathologiques ainsi qu'aux traitements disponibles. Nous parlons également de l'expérience clinique de cette pathologie au sein de notre Service d'immunologie clinique aux HUG.

[Sjögren's syndrom: clinical, diagnostic and therapeutic innovations]. / Syndrome de Sjögren : nouveautés cliniques, diagnostiques et thérapeutiques.

Sjögren's syndrome (SS) is a systemic autoimmune disease affecting the lacrimal and salivary glands. In up to one third of patients, SS may be complicated by potentially severe extra-glandular visceral involvement, which can be life-threatening. Diagnosis is often difficult based on a combination of clinical and biological evidence. The development of new imaging techniques can now help the clinician in his diagnostic approach. Long considered incurable, new medical and surgical treatments are being studied and are potentially promising. Paramedical management and regular physical activity are also essential and contribute to the improvement of patients' fatigue. The objective of this article is to review the main clinical manifestations as well as the diagnostic and therapeutic novelties developed in recent years.

Le syndrome de Sjögren (SS) est une maladie autoimmune systémique touchant les glandes lacrymales et salivaires. Chez près d'un tiers des patients, il peut se compliquer d'atteintes extraglandulaires potentiellement sévères. Le diagnostic, reposant sur un faisceau d'arguments clinicobiologiques, est souvent difficile. Le développement des nouvelles techniques d'imagerie peut aujourd'hui aider le clinicien dans sa démarche diagnostique. Longtemps considéré comme incurable, de nouveaux traitements médicochirurgicaux sont en cours d'étude et potentiellement prometteurs. Une prise en charge paramédicale avec une activité physique régulière est également essentielle. L'objectif de cet article est de revoir les manifestations cliniques ainsi que les nouveautés diagnostiques et thérapeutiques développées ces dernières années.

[VEXAS syndrome : when do we have to consider it ?] / Syndrome VEXAS : quand y penser ?

VEXAS syndrome was recently discovered in patients who developed late in adulthood an inflammatory syndrome with fever, cytopenias, dysplastic bone marrow, cutaneous and pulmonary neutrophilic inflammation, arthritis, chondritis, or vasculitis. It is the result of an inactivating somatic mutation affecting methionine codon 41 of the UBA1 gene which encodes an ubiquitin activating enzyme (E1). Systemic corticosteroids generally reduce symptoms, while other immunosuppressive drugs only have limited long-term effects. Azacitidine is a promising treatment, but further studies are warranted. Here, we describe 2 new cases including one associated with pyoderma gangrenosum and cryoglobulinemia.

Le syndrome VEXAS (Vacuoles, E1 Enzyme, X-Linked, Auto- Inflammatory, Somatic Syndrome) a été récemment découvert chez des patients développant tardivement à l'âge adulte un syndrome inflammatoire associé à de la fièvre, des cytopénies, une moelle osseuse dysplasique, une inflammation neutrophilique cutanée et pulmonaire, des arthrites, des chondrites ou des vasculites. Il est le résultat d'une mutation somatique inactivatrice affectant le codon méthionine 41 du gène UBA1 qui encode une enzyme E1 activant l'ubiquitine. Les corticostéroïdes systémiques permettent généralement de diminuer les symptômes alors que les autres immunosuppresseurs ont un effet limité à long terme. L'azacitidine est l'un des traitements ayant démontré une efficacité, cependant de nouvelles études sont souhaitables. Nous décrivons ici 2 cas dont l'un est associé à un pyoderma gangrenosum et une cryoglobulinémie.

Prevalence of large vessel vasculitis in ANCA-associated vasculitis: a retrospective cohort study.

ANCA-associated vasculitis (AAV) in general involves small blood vessels and includes granulomatosis with polyangiitis (GPA), eosinophilic granulomatosis with polyangiitis (EGPA), and microscopic polyangiitis (MPA). Although reported in a few studies, the prevalence of large vessel vasculitis (LVV) in patients with AAV remains to be further explored. The goal of the present study was to assess the prevalence of LVV in a cohort of patients with AAV and to characterize this population. We conducted a ten-year retrospective study of a single-center cohort of AAV, including 101 patients with GPA (n = 58), EGPA (n = 28), MPA (n = 15), and compared the groups with or without associated LVV. LVV was diagnosed in five patients, two with aortitis and three with temporal arteritis, corresponding to a total prevalence of 5.0% [95% CI 1.6-11.2%]. This value was significantly higher than the estimated prevalence of LVV in the normal Swiss population (OR 234.9 95% CI 91.18-605.2, p < 0.001). All five patients had GPA, whereas no cases with EGPA or MPA were identified. Anti-PR3 antibodies were detected in four out of five patients, anti-MPO in one patient. Since LVV can occur in a significant proportion of patients with GPA, evaluation for LVV may be considered systematically in the diagnostic workup of AAV.

[Small fiber neuropathy in systemic autoimmune diseases]. / Neuropathie des petites fibres dans les maladies autoimmunes systémiques.

Small fiber neuropathy (SFN) causes damage to small-calibre nerve fibers (unmyelinated C fibers and myelinated A-delta fibers). The symptoms of SFN usually are sensitive including paresthesia, dysesthesia or burning pain, and protopathic deficits, sometimes associated with dysautonomia. The causes of SFN can be classified in six main groups: idiopathic, toxic, metabolic, immunological, infectious and hereditary. In this article, we present the diagnostic approach to SFN, the most common autoimmune aetiologies, as well as elements of their therapeutic management.

La neuropathie des petites fibres (NPF) implique une atteinte des fibres nerveuses de petit calibre : les fibres C non myélinisées et les fibres A-delta myélinisées. Elle se manifeste principalement par des troubles sensitifs : paresthésies, dysesthésies ou douleurs neuropathiques (brûlures) et déficits protopathiques, associés à des symptômes dysautonomiques. Les étiologies possibles des NPF sont variées : idiopathiques, toxiques, métaboliques, immunologiques, infectieuses et héréditaires. Nous présentons dans cet article la démarche diagnostique des NPF, les étiologies autoimmunes les plus fréquemment associées aux NPF, ainsi que des éléments de prise en charge thérapeutique.

Annexin V expression on CD4+ T cells with regulatory function.

Regulatory T (Treg) cells induce immunologic tolerance by suppressing effector functions of conventional lymphocytes in the periphery. On the other hand, immune silencing is mediated by recognition of phosphatidylserine (PS) on apoptotic cells by phagocytes. Here we describe expression of the PS-binding protein Annexin V (ANXA5) in CD4+  CD25hi Treg cells at the mRNA and protein levels. CD4+  ANXA5+ T cells constitute about 0·1%-0·6% of peripheral blood CD3+ T cells, exhibit co-expression of several Treg markers, such as Forkhead box P3, programmed cell death protein-1, cytotoxic T-lymphocyte antigen-4 and CD38. In vitro, ANXA5+ Treg cells showed enhanced adhesion to PS+ endothelial cells. Stimulated by anti-CD3 and PS+ syngeneic antigen-presenting cells CD4+  ANXA5+ T cells expanded in the absence of exogenous interleukin-2. CD4+  ANXA5+ T cells suppressed CD4+  ANXA5- T-cell proliferation and mammalian target of rapamycin phosphorylation, partially dependent on cell contact. CD4+  ANXA5+ T-cell-mediated suppression was allo-specific and accompanied by an increased production of anti-inflammatory mediators. In vivo, using a model of delayed type hypersensitivity, murine CD4+  ANXA5+ T cells inhibited T helper type 1 responses. In conclusion, we report for the first time expression of ANXA5 on a subset of Treg cells that might bridge classical regulatory Treg function with immune silencing.

Prolongation of rat-to-mouse islets xenograft survival by co-transplantation of autologous IL-10 differentiated murine tolerogenic dendritic cells.

BACKGROUND: Tolerogenic dendritic cells (DCs) represent a promising approach to promote transplantation tolerance. In this study, the potential of autologous bone marrow (BM)-derived murine DC to protect rat-to-mouse islets xenografts was analyzed. METHODS: Tolerogenic DCs were generated by differentiating BM cells in the presence of granulocyte-macrophage colony-stimulating factor and interleukin 10 (IL-10, IL-10 DC). The phenotype of IL-10 DC was characterized in vitro by expression of costimulatory/inhibitory molecules (flow cytometry) and cytokines (Luminex and ELISA), their function by phagocytosis and T-cell stimulation assays. To study transplant tolerance in vivo, rat islets were transplanted alone or in combination with autologous murine IL-10 DC under the kidney capsule of streptozotocin-induced diabetic C57BL/6 mice. Xenograft survival was evaluated by monitoring glycemia, cellular infiltration of xenografts by microscopy and flow cytometry 10 days post-transplantation. RESULTS: Compared with control DC, IL-10 DC exhibited lower levels of major histocompatibility complex class II, costimulatory molecules (CD40, CD86, CD205), lower production of pro-inflammatory cytokines (IL-12p70, TNF, IL-6), and higher production of IL-10. Phagocytosis of xenogeneic rat splenocytes was not impaired in IL-10 DC, whereas stimulation of T-cell proliferation was reduced in the presence of IL-10 DC. Xenograft survival of rat islets in diabetic mice co-transplanted with autologous murine IL-10 DC was significantly prolonged from 12 to 21 days, without additional immunosuppressive treatment. Overall, infiltration of xenografts by T cells and myeloid cells was not different in IL-10 DC recipient mice, but enriched for CD8+ T cells and myeloid cells with suppressor-associated phenotype. CONCLUSIONS: Autologous IL-10-differentiated DC with tolerogenic properties prolong rat-to-mouse islets xenograft survival, potentially by locally inducing immune regulatory cells, indicating their potential for regulatory immune cell therapy in xenotransplantation.

Efficacy of Omalizumab in Mastocytosis: Allusive Indication Obtained from a Prospective, Double-Blind, Multicenter Study (XOLMA Study).

BACKGROUND: Patients with mastocytosis often suffer from a variety of symptoms caused by mast cell mediators where treatments remain difficult, showing various success rates. Omalizumab, a monoclonal anti-IgE antibody, has been postulated to have a positive impact on mastocytosis-associated symptoms such as flush, vertigo, gastrointestinal problems, or anaphylaxis. OBJECTIVE: To investigate the efficacy and safety of omalizumab in systemic mastocytosis. METHODS: Patients with histologically proven mastocytosis were investigated in a multicenter prospective double-blind placebo-controlled trial to receive either omalizumab or placebo, dosed according to IgE and body weight. The primary endpoint was change in the AFIRMM activity score after 6 months of treatment. Different laboratory parameters were analyzed. RESULTS: Sixteen patients were analyzed: 7 to omalizumab and 9 to placebo (mean age 47.7 ± 13.8 vs. 45.4 ± 8.8 years; 66.6 vs. 85.7% were female; mean disease duration 10.0 ± 5.1 vs. 4.5 ± 2.9 years, respectively). After 6 months the median AFIRMM score decreased 50% from 52.0 to 26.0 in the omalizumab group versus 104.0-102.0 in the placebo group (p = 0.286); however, the difference was not significant (p = 0.941). Secondary endpoints, including the number of allergic reactions, changes in major complaints, wheal-and-flare reaction due to mechanical irritation (Darier's sign), and frequency of the use of mastocytosis-specific drugs improved in the omalizumab group, but not significantly. Adverse events like urticaria, bronchospasm, and anaphylactic shock showed no significant difference between the groups. No severe adverse events occurred. FcεRI (Fc-epsilon receptor) expression on basophils decreased after receiving omalizumab versus placebo. CONCLUSION: Omalizumab was safe and showed a tendency to improve mastocytosis-related symptoms, in particular diarrhea, dizziness, flush, and anaphylactic reactions, including the AFIRMM score and secondary endpoints; however, the difference was not significant. Due to the small study size and difference at baseline between the study groups, further studies are required to confirm our findings.

[Myocarditis in 2020]. / La myocardite en 2020.

Myocarditis is an inflammatory disease of the myocardium caused by various etiologies with a dominance of viral infections and potential post-infectious autoimmunity. The clinical presentation ranges from chest pain to severe complications including cardiogenic shock, ventricular arrhythmias, and progression to dilated cardiomyopathy. The diagnostic approach is challenging and includes several investigations, such as an ECG, an echocardiography, troponin testing and the exclusion of coronary artery disease. Although endomyocardial biopsy remains the gold standard, cardiovascular magnetic resonance is now the most valuable tool to accurately characterize myocardial tissue inflammation. The management is mainly symptomatic and consists in early detection and treatment of complications including heart failure and arrhythmias.

La myocardite est une inflammation du muscle cardiaque dont les étiologies sont variées, avec une prédominance d'atteinte infectieuse virale et d'une autoimmunité postinfectieuse. Le spectre clinique varie de la douleur thoracique aux complications comme le choc cardiogénique, les arythmies malignes et la cardiomyopathie dilatée. La démarche diagnostique est un défi pour le clinicien et comprend un ECG, un bilan biologique, une échocardiographie, ainsi que l'exclusion d'une maladie coronarienne. La biopsie myocardique reste le gold standard, mais l'imagerie par résonance magnétique est actuellement l'examen de référence pour caractériser avec précision le tissu myocardique inflammatoire. La prise en charge est essentiellement symptomatique et consiste à dépister et traiter précocement les complications comme l'insuffisance cardiaque et les arythmies.

[ENT and head and neck manifestations of the IgG4-related disease]. / Atteintes de la sphère ORL et cervicofaciale dans la maladie à IgG4.

IgG4-related disease is a rare multi-organic inflammatory disease that frequently involves the ENT and head and neck areas. In these cases, salivary gland and lacrimal gland involvement is very common and includes enlargement, infiltration, and formation of pseudotumours. Diagnosis of IgG4 related disease remains a challenge and relies on several clinical, serological, radiological and histopathological criteria to differentiate from other diseases with similar clinical presentation. Histology reveals IgG4 positive lymphoplasmocytic infiltrates, storiform fibrosis and obliterative phlebitis. Glucocorticoids are the first line of treatment and can be combined with other immunosuppressants. The prognosis is favorable if treatment is initiated early. Recurrences are common. Delay in diagnosis can have severe multi-organic consequences.

Rare et encore peu connue, la maladie à immunoglobuline G4 (IgG4) est multiorganique et se manifeste fréquemment dans la sphère oto-rhino-laryngologique et cervico-faciale. Dans ces cas, les glandes lacrymales et salivaires sont les plus fréquemment touchées, présentant des tuméfactions, infiltrations et pseudotumeurs. Le diagnostic reste un défi ; il repose sur des critères cliniques, sérologiques, radiologiques et histopathologies qui visent à la distinguer des nombreuses maladies de présentations cliniques similaires. À l'histologie, on retrouve un infiltrat lymphoplasmocytaire riche en plasmocytes IgG4+, une fibrose storiforme et des phlébites oblitérantes. Les glucocorticoïdes sont la première ligne de traitement et peuvent être associés à d'autres immunosuppresseurs. Le pronostic est favorable si le traitement est initié rapidement. Les récidives sont courantes. Un retard diagnostique peut avoir des conséquences multiorganiques sévères.

CLIPPERS and its mimics: evaluation of new criteria for the diagnosis of CLIPPERS.

OBJECTIVE: To evaluate the accuracy of the recently proposed diagnostic criteria for chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids (CLIPPERS). METHODS: We enrolled 42 patients with hindbrain punctate and/or linear enhancements (<3 mm in diameter) and tested the CLIPPERS criteria. RESULTS: After a median follow-up of 50 months (IQR 25-82), 13 out of 42 patients were CLIPPERS-mimics: systemic and central nervous system lymphomas (n=7), primary central nervous system angiitis (n=4) and autoimmune gliopathies (n=2). The sensitivity and specificity of the CLIPPERS criteria were 93% and 69%, respectively. Nodular enhancement ( ≥ 3 mm in diameter), considered as a red flag in CLIPPERS criteria, was present in 4 out of 13 CLIPPERS-mimics but also in 2 out of 29 patients with CLIPPERS, explaining the lack of sensitivity. Four out of 13 CLIPPERS-mimics who initially met the CLIPPERS criteria displayed red flags at the second attack with a median time of 5.5 months (min 3, max 18), explaining the lack of specificity. One of these four patients had antimyelin oligodendrocyte glycoprotein antibodies, and the three remaining patients relapsed despite a daily dose of prednisone/prednisolone ≥ 30 mg and a biopsy targeting atypical enhancing lesions revealed a lymphoma. CONCLUSIONS: Our study highlights that (1) nodular enhancement should be considered more as an unusual finding than a red flag excluding the diagnosis of CLIPPERS; (2) red flags may occur up to 18 months after disease onset; (3) as opposed to CLIPPERS-mimics, no relapse occurs when the daily dose of prednisone/prednisolone is ≥ 30 mg; and (4) brain biopsy should target an atypical enhancing lesion when non-invasive investigations remain inconclusive.

Immunological aspects of allogeneic pancreatic islet transplantation: a comparison between mouse and human.

Pancreatic islet allotransplantation is a treatment for patients with severe forms of type 1 diabetes. As long-term graft function and survival are not yet optimal, additional studies are warranted in order to continue improving transplant outcomes. The mechanisms of islet graft loss and tolerance induction are often studied in murine diabetes models. Despite numerous islet transplantation studies successfully performed over recent years, translation from experimental mouse models to human clinical application remains elusive. This review aims at critically discussing the strengths and limitations of current mouse models of diabetes and experimental islet transplantation. In particular, we will analyze the causes leading to diabetes and compare the immunological mechanisms responsible for rejection between mouse and human. A better understanding of the experimental mouse models should facilitate translation to human clinical application.

Thyroid Rosai-Dorfman disease with infiltration of IgG4-bearing plasma cells associated with multiple small pulmonary cysts.

BACKGROUND: Rosai-Dorfman disease (RDD) is a rare histiocytosis which involves principally lymph nodes. Thyroid involvement in RDD is a very rare situation, and lung involvement is even rarer. CASE PRESENTATION: We report the case of a 46-year-old woman presenting a painless mass in the right side of the neck and subacute dyspnoea. Computerised tomography (CT) scans of the neck and thorax showed a large thyroid mass causing tracheal stenosis and multiple cystic lesions in both lungs. Subtotal thyroidectomy with a tracheal segment resection and histological analysis confirmed the diagnosis of nodal and extranodal (thyroid, tracheal and probably lung) Rosai-Dorfman disease (RDD) with the presence of increased numbers of IgG4-bearing plasma cells. Clinical, functional and radiological follow up 4 years after surgery without medical treatment did not show any disease progression. CONCLUSIONS: This case report indicates a benign course of nodal RDD with thyroid and tracheal infiltration following surgical resection, association of typical histological signs of RDD (emperipolesis) with IgG4-related disease features, and that lung cysts might be a manifestation of RDD.

[IgG4 related disease†: the Geneva experience​]. / Maladie à IgG4†: l'expérience genevoise.

IgG4-related disease is a fibroinflammatory pathology which gathers several disorders with common histological, serological and clinical features. The disease usually manifests itself as a diffuse or localized enlargement of one or several organs that reveals upon histology a dense lymphoplasmatic infiltrate with IgG4 positive plasma cells, a storiform fibrosis and obliterative phlebitis. Serum IgG4 are often but not always increased. Diagnostic criterias were published in 2011. Lesions caused by the disease might become irreversible without treatment. Currently, glucocorticoids are the first line of treatment. However, other immunosuppressants such as rituximab are sometimes used.

La maladie à IgG4 est une pathologie fibro-inflammatoire regroupant un ensemble de troubles aux caractéristiques histologiques, sérologiques et cliniques communes. Elle se manifeste généralement par une hypertrophie localisée ou diffuse d'un ou plusieurs organes dont la biopsie montre un infiltrat lymphoplasmocytaire riche en plasmocytes IgG4+, une fibrose storiforme et une phlébite oblitérante. Les IgG4 sériques sont souvent mais pas toujours augmentées. Des critères diagnostiques ont été publiés en 2011. Ses atteintes peuvent être irréversibles en l'absence de traitement. Actuellement, les glucocorticoïdes constituent la thérapie de premier choix. Cependant, d'autres immunosuppresseurs tels que le rituximab sont parfois employés.

Release of pig leukocytes and reduced human NK cell recruitment during ex vivo perfusion of HLA-E/human CD46 double-transgenic pig limbs with human blood.

BACKGROUND: In pig-to-human xenotransplantation, interactions between human natural killer (NK) cells and porcine endothelial cells (pEC) are characterized by recruitment and cytotoxicity. Protection from xenogeneic NK cytotoxicity can be achieved in vitro by the expression of the non-classical human leukocyte antigen-E (HLA-E) on pEC. Thus, the aim of this study was to analyze NK cell responses to vascularized xenografts using an ex vivo perfusion system of pig limbs with human blood. METHODS: Six pig forelimbs per group, respectively, stemming from either wild-type (wt) or HLA-E/hCD46 double-transgenic (tg) animals, were perfused ex vivo with heparinized human blood for 12 hours. Blood samples were collected at defined time intervals, cell numbers counted, and peripheral blood mononuclear cells analyzed for phenotype by flow cytometry. Muscle biopsies were analyzed for NK cell infiltration. In vitro NK cytotoxicity assays were performed using pEC derived from wt and tg animals as target cells. RESULTS: Ex vivo, a strong reduction in circulating human CD45 leukocytes was observed after 60 minutes of xenoperfusion in both wt and tg limb groups. NK cell numbers dropped significantly. Within the first 10 minutes, the decrease in NK cells was more significant in the wt limb perfusions as compared to tg limbs. Immunohistology of biopsies taken after 12 hours showed less NK cell tissue infiltration in the tg limbs. In vitro, NK cytotoxicity against hCD46 single tg pEC and wt pEC was similar, while lysis of double tg HLA-E/hCD46 pEC was significantly reduced. Finally, circulating cells of pig origin were observed during the ex vivo xenoperfusions. These cells expressed phenotypes mainly of monocytes, B and T lymphocytes, NK cells, as well as some activated endothelial cells. CONCLUSIONS: Ex vivo perfusion of pig forelimbs using whole human blood represents a powerful tool to study humoral and early cell-mediated rejection mechanisms of vascularized pig-to-human xenotransplantation, although there are several limitations of the model. Here, we show that (i) transgenic expression of HLA-E/hCD46 in pig limbs provides partial protection from human NK cell-mediated xeno responses and (ii) the emergence of a pig cell population during xenoperfusions with implications for the immunogenicity of xenografts.

Multiple genetically modified GTKO/hCD46/HLA-E/hß2-mg porcine hearts are protected from complement activation and natural killer cell infiltration during ex vivo perfusion with human blood.

BACKGROUND: In pig-to-human xenotransplantation, early cellular rejection reactions are mediated by natural killer cells (NK cells). Human NK cells are inhibited by HLA-E via CD94/NKG2A receptors. To protect porcine grafts against human NK cell responses, transgenic GTKO pigs expressing hCD46 and HLA-E have been generated. The aim of this study was to test the effect of this genetic modification on xenogeneic, and in particular human NK cell response, using an ex vivo perfusion model of pig hearts with human blood. METHODS: Cardiopleged and explanted genetically modified (gm) pig hearts (GTKO/hCD46/HLA-E/hß2-microglobulin) and wild-type (wt) controls (n = 6 each) were reperfused and tested in an 8 hours ex vivo perfusion system using freshly drawn human blood. Cardiac function was evaluated during a 165-minute period in working heart mode. Myocardial damage, antibody deposition, complement activation, and coagulation parameters were evaluated histologically at the end of perfusion. The number of NK cells in the perfusate was determined by flow cytometry at baseline and at 8 hours; tissue infiltration by NK cells was quantified by immunofluorescence microscopy using NKp46 staining of frozen sections. RESULTS: Deposition of IgG (1.2 ± 1 × 107 vs 8.8 ± 2.9 × 106 ; P < .01), IgM (4.4 ± 3.7 × 106 vs 1.7 ± 1.2 × 106 ; P < .01), and the complement activation product C4b/c (3.5 ± 1.3 × 106 vs 2.3 × 106  ± 9.4 × 105 ; P > .01) was lower in gm than wt hearts. NK cell percentages of leukocytes in the perfusate decreased from 0.94 ± 0.77% to 0.21 ± 0.25% (P = .04) during xenoperfusion of wt hearts. In contrast, the ratio of NK cells did not decrease significantly in the gm hearts. In this group, NK cell myocardial infiltration after 480 minutes of perfusion was lower than in wt organs (2.5 ± 3.7 × 104 /mm3 vs 1.3 ± 1.4 × 105 /mm3 ; P = .0001). The function of gm hearts was better preserved compared to wt organs, as demonstrated by higher cardiac index during the first 2 hours of ex vivo perfusion. CONCLUSION: GTKO, hCD46, and HLA-E expression in porcine hearts reduced complement deposition, complement dependent injury, and myocardial NK cell infiltration during perfusion with human blood. This tested combination of genetic modifications may minimize damage from acute human-anti-pig rejection reactions and improve myocardial function after xenotransplantation.

Xenotransplantation: back to the future?

The field of xenotransplantation has fluctuated between great optimism and doubts over the last 50 years. The initial clinical attempts were extremely ambitious but faced technical and ethical issues that prompted the research community to go back to preclinical studies. Important players left the field due to perceived xenozoonotic risks and the lack of progress in pig-to-nonhuman-primate transplant models. Initial apparently unsurmountable issues appear now to be possible to overcome due to progress of genetic engineering, allowing the generation of multiple-xenoantigen knockout pigs that express human transgenes and the genomewide inactivation of porcine endogenous retroviruses. These important steps forward were made possible by new genome editing technologies, such as CRISPR/Cas9, allowing researchers to precisely remove or insert genes anywhere in the genome. An additional emerging perspective is the possibility of growing humanized organs in pigs using blastocyst complementation. This article summarizes the current advances in xenotransplantation research in nonhuman primates, and it describes the newly developed genome editing technology tools and interspecific organ generation.