Anti-SARS-CoV-2 glyco-humanized polyclonal antibody XAV-19: phase II/III randomized placebo-controlled trial shows acceleration to recovery for mild to moderate patients with COVID-19.

Introduction: XAV-19 is a glyco-humanized swine polyclonal antibody targeting SARS-CoV-2 with high neutralizing activity. The safety and clinical efficacy of XAV-19 were investigated in patients with mild to moderate COVID-19. Methods: This phase II/III, multicentric, randomized, double-blind, placebo-controlled clinical trial was conducted to evaluate the safety and clinical efficacy of XAV-19 in patients with a seven-point WHO score of 2 to 4 at randomization, i.e., inpatients with COVID-19 requiring or not requiring low-flow oxygen therapy, and outpatients not requiring oxygen (EUROXAV trial, NCT04928430). Adult patients presenting in specialized or emergency units with confirmed COVID-19 and giving their consent to participate in the study were randomized to receive 150 mg of XAV-19 or placebo. The primary endpoint was the proportion of patients with aggravation within 8 days after treatment, defined as a worsening of the seven-point WHO score of at least one point between day 8 and day 1 (inclusion). The neutralization activity of XAV-19 against variants circulating during the trial was tested in parallel. Results: From March 2021 to October 2022, 279 patients received either XAV-19 (N = 140) or placebo (N = 139). A slow enrollment and a low rate of events forced the termination of the premature trial. XAV-19 was well tolerated. Underpowered statistics did not allow the detection of any difference in the primary endpoint between the two groups or in stratified groups. Interestingly, analysis of the time to improvement (secondary endpoint) showed that XAV-19 significantly accelerated the recovery for patients with a WHO score of 2 or 3 (median at 7 days vs. 14 days, p = 0.0159), and even more for patients with a WHO score of 2 (4 days vs. 14 days, p = 0.0003). The neutralizing activity against Omicron and BA.2, BA.2.12.1, BA.4/5, and BQ.1.1 subvariants was shown. Discussion: In this randomized placebo- controlled trial with premature termination, reduction of aggravation by XAV-19 at day 8 in patients with COVID-19 was not detectable. However, a significant reduction of the time to improvement for patients not requiring oxygen was observed. XAV-19 maintained a neutralizing activity against SARS-CoV-2 variants. Altogether, these data support a possible therapeutic interest for patients with mild to moderate COVID-19 requiring anti-SARS-CoV-2 neutralizing antibodies. Clinical Trial Registration: https://clinicaltrials.gov/, identifier NCT04928430; https://www.clinicaltrialsregister.eu/about.html (EudraCT), identifier 2020-005979-12.

First-in-human Study With LIS1, a Next-generation Porcine Low Immunogenicity Antilymphocyte Immunoglobulin in Kidney Transplantation.

BACKGROUND: Polyclonal rabbit antithymocyte globulins (ATGs) are commonly used in organ transplantation as induction. Anti-N-glycolylneuraminic acid carbohydrate antibodies which develop in response to rabbit carbohydrate antigens might lead to unwanted systemic inflammation. LIS1, the first new generation of antilymphocyte globulins (ALGs) derived from double knockout swine, lacking carbohydrate xenoantigens was already tested in nonhuman primates and rodent models. METHODS: This open-label, single-site, dose escalation, first-in-human, phase 1 study evaluated the safety, T cell depletion, pharmacokinetics, and pharmacodynamics of LIS1. In an ascending dose cohort (n = 5), a primary kidney transplant recipient at low immunologic risk (panel reactive antibody [PRA] < 20%), received LIS1 for 5 d at either 0.6, 1, 3, 6, or 8 mg/kg. After each patient completed treatment, the data safety monitoring board approved respective dose escalation. In the therapeutic dose cohort (n = 5) in patients with PRA <50% without donor specific antibodies, 2 patients received 8 mg/kg and 3 patients 10 mg/kg. RESULTS: CD3+ T cell depletion <100/mm3 at day 2 was observed in all patients who received 6, 8, and 10 mg/kg of LIS1. The terminal half-life of LIS1 was 33.7 d with linearity in its disposition. Lymphocyte repopulation was fast and pretransplant lymphocyte subpopulation counts recovered within 2-4 wk. LIS1 was well tolerated, neither cytokine release syndrome nor severe thrombocytopenia or leukopenia were noticed. Antibodies to LIS1 were not detected. CONCLUSIONS: In this first-in-human trial, genome-edited swine-derived polyclonal LIS1 ALG was well tolerated, did not elicit antidrug antibodies, and caused time-limited T cell depletion in low- and medium-risk kidney transplant recipients.

Polyclonal antibodies selectively inhibit tumor growth and invasion and synergize with immune checkpoint inhibitors.

Heterologous polyclonal antibodies (pAb) were shown to possess oncolytic properties a century ago with reported clinical responses. More recent preclinical models confirmed pAb efficacy, though their ability to tackle complex target antigens reduces susceptibility to tumor escape. Owing to the recent availability of glyco-humanized pAb (GH-pAb) with acceptable clinical toxicology profile, we revisited use of pAb in oncology and highlighted their therapeutic potential against multiple cancer types. Murine antitumor pAb were generated after repeated immunization of rabbits with murine tumor cell lines from hepatocarcinoma, melanoma, and colorectal cancers. Antitumor pAb recognized and showed cytotoxicity against their targets without cross-reactivity with healthy tissues. In vivo, pAb are effective alone; moreover, these pAb synergize with immune checkpoint inhibitors like anti-PD-L1 in several cancer models. They elicited an antitumor host immune response and prevented metastases. The anticancer activity of pAb was also confirmed in xenografted NMRI nude mice using GH-pAb produced by repeated immunization of pigs with human tumor cell lines. In conclusion, the availability of bioengineered GH-pAb allows for revisiting of passive immunotherapy with oncolytic pAb to fight against solid tumor and cancer metastasis.

Corrigendum: XAV-19, a swine glyco-humanized polyclonal antibody against SARS-CoV-2 spike receptor-binding domain, targets multiple epitopes and broadly neutralizes variants.

[This corrects the article DOI: 10.3389/fimmu.2021.761250.].

Systems prediction of chronic lung allograft dysfunction: Results and perspectives from the Cohort of Lung Transplantation and Systems prediction of Chronic Lung Allograft Dysfunction cohorts.

Background: Chronic lung allograft dysfunction (CLAD) is the leading cause of poor long-term survival after lung transplantation (LT). Systems prediction of Chronic Lung Allograft Dysfunction (SysCLAD) aimed to predict CLAD. Methods: To predict CLAD, we investigated the clinicome of patients with LT; the exposome through assessment of airway microbiota in bronchoalveolar lavage cells and air pollution studies; the immunome with works on activation of dendritic cells, the role of T cells to promote the secretion of matrix metalloproteinase-9, and subpopulations of T and B cells; genome polymorphisms; blood transcriptome; plasma proteome studies and assessment of MSK1 expression. Results: Clinicome: the best multivariate logistic regression analysis model for early-onset CLAD in 422 LT eligible patients generated a ROC curve with an area under the curve of 0.77. Exposome: chronic exposure to air pollutants appears deleterious on lung function levels in LT recipients (LTRs), might be modified by macrolides, and increases mortality. Our findings established a link between the lung microbial ecosystem, human lung function, and clinical stability post-transplant. Immunome: a decreased expression of CLEC1A in human lung transplants is predictive of the development of chronic rejection and associated with a higher level of interleukin 17A; Immune cells support airway remodeling through the production of plasma MMP-9 levels, a potential predictive biomarker of CLAD. Blood CD9-expressing B cells appear to favor the maintenance of long-term stable graft function and are a potential new predictive biomarker of BOS-free survival. An early increase of blood CD4 + CD57 + ILT2+ T cells after LT may be associated with CLAD onset. Genome: Donor Club cell secretory protein G38A polymorphism is associated with a decreased risk of severe primary graft dysfunction after LT. Transcriptome: blood POU class 2 associating factor 1, T-cell leukemia/lymphoma domain, and B cell lymphocytes, were validated as predictive biomarkers of CLAD phenotypes more than 6 months before diagnosis. Proteome: blood A2MG is an independent predictor of CLAD, and MSK1 kinase overexpression is either a marker or a potential therapeutic target in CLAD. Conclusion: Systems prediction of Chronic Lung Allograft Dysfunction generated multiple fingerprints that enabled the development of predictors of CLAD. These results open the way to the integration of these fingerprints into a predictive handprint.

LIS1, a glyco-humanized swine polyclonal anti-lymphocyte globulin, as a novel induction treatment in solid organ transplantation.

Anti-thymocyte or anti-lymphocyte globulins (ATGs/ALGs) are immunosuppressive drugs used in induction therapies to prevent acute rejection in solid organ transplantation. Because animal-derived, ATGs/ALGs contain highly immunogenic carbohydrate xenoantigens eliciting antibodies that are associated with subclinical inflammatory events, possibly impacting long-term graft survival. Their strong and long-lasting lymphodepleting activity also increases the risk for infections. We investigated here the in vitro and in vivo activity of LIS1, a glyco-humanized ALG (GH-ALG) produced in pigs knocked out for the two major xeno-antigens αGal and Neu5Gc. It differs from other ATGs/ALGs by its mechanism of action excluding antibody-dependent cell-mediated cytotoxicity and being restricted to complement-mediated cytotoxicity, phagocyte-mediated cytotoxicity, apoptosis and antigen masking, resulting in profound inhibition of T-cell alloreactivity in mixed leucocyte reactions. Preclinical evaluation in non-human primates showed that GH-ALG dramatically reduced CD4+ (p=0.0005,***), CD8+ effector T cells (p=0.0002,***) or myeloid cells (p=0.0007,***) but not T-reg (p=0.65, ns) or B cells (p=0.65, ns). Compared with rabbit ATG, GH-ALG induced transient depletion (less than one week) of target T cells in the peripheral blood (<100 lymphocytes/L) but was equivalent in preventing allograft rejection in a skin allograft model. The novel therapeutic modality of GH-ALG might present advantages in induction treatment during organ transplantation by shortening the T-cell depletion period while maintaining adequate immunosuppression and reducing immunogenicity.

XAV-19, a Swine Glyco-Humanized Polyclonal Antibody Against SARS-CoV-2 Spike Receptor-Binding Domain, Targets Multiple Epitopes and Broadly Neutralizes Variants.

Amino acid substitutions and deletions in the Spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants can reduce the effectiveness of monoclonal antibodies (mAbs). In contrast, heterologous polyclonal antibodies raised against S protein, through the recognition of multiple target epitopes, have the potential to maintain neutralization capacities. XAV-19 is a swine glyco-humanized polyclonal neutralizing antibody raised against the receptor binding domain (RBD) of the Wuhan-Hu-1 Spike protein of SARS-CoV-2. XAV-19 target epitopes were found distributed all over the RBD and particularly cover the receptor binding motives (RBMs), in direct contact sites with the angiotensin converting enzyme-2 (ACE-2). Therefore, in Spike/ACE-2 interaction assays, XAV-19 showed potent neutralization capacities of the original Wuhan Spike and of the United Kingdom (Alpha/B.1.1.7) and South African (Beta/B.1.351) variants. These results were confirmed by cytopathogenic assays using Vero E6 and live virus variants including the Brazil (Gamma/P.1) and the Indian (Delta/B.1.617.2) variants. In a selective pressure study on Vero E6 cells conducted over 1 month, no mutation was associated with the addition of increasing doses of XAV-19. The potential to reduce viral load in lungs was confirmed in a human ACE-2 transduced mouse model. XAV-19 is currently evaluated in patients hospitalized for COVID-19-induced moderate pneumonia in phase 2a-2b (NCT04453384) where safety was already demonstrated and in an ongoing 2/3 trial (NCT04928430) to evaluate the efficacy and safety of XAV-19 in patients with moderate-to-severe COVID-19. Owing to its polyclonal nature and its glyco-humanization, XAV-19 may provide a novel safe and effective therapeutic tool to mitigate the severity of coronavirus disease 2019 (COVID-19) including the different variants of concern identified so far.

High neutralizing potency of swine glyco-humanized polyclonal antibodies against SARS-CoV-2.

Heterologous polyclonal antibodies might represent an alternative to the use of convalescent plasma or monoclonal antibodies (mAbs) in coronavirus disease (COVID-19) by targeting multiple antigen epitopes. However, heterologous antibodies trigger human natural xenogeneic antibody responses particularly directed against animal-type carbohydrates, mainly the N-glycolyl form of the neuraminic acid (Neu5Gc) and the α1,3-galactose, potentially leading to serum sickness or allergy. Here, we immunized cytidine monophosphate-N-acetylneuraminic acid hydroxylase and α1,3-galactosyl-transferase (GGTA1) double KO pigs with the Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike receptor binding domain to produce glyco-humanized polyclonal neutralizing antibodies lacking Neu5Gc and α1,3-galactose epitopes. Animals rapidly developed a hyperimmune response with anti-SARS-CoV-2 end-titers binding dilutions over one to a million and end-titers neutralizing dilutions of 1:10 000. The IgG fraction purified and formulated following clinical Good Manufacturing Practices, named XAV-19, neutralized spike/angiotensin converting enzyme-2 interaction at a concentration <1 µg/mL, and inhibited infection of human cells by SARS-CoV-2 in cytopathic assays. We also found that pig GH-pAb Fc domains fail to interact with human Fc receptors, thereby avoiding macrophage-dependent exacerbated inflammatory responses and a possible antibody-dependent enhancement. These data and the accumulating safety advantages of using GH-pAbs in humans warrant clinical assessment of XAV-19 against COVID-19.

Plasma Acute Phase Proteins as Predictors of Chronic Lung Allograft Dysfunction in Lung Transplant Recipients.

Cumulating reports suggest that acute phase proteins (APPs) have diagnostic and prognostic value in different clinical conditions. Among others, APPs are proposed to serve as markers that help to control the outcome of transplant recipients. Here, we questioned whether plasma concentrations of APPs mirror the development of chronic lung allograft dysfunction (CLAD). We performed blinded analysis of serial plasma samples retrospectively collected from 35 lung transplanted patients, of whom 25 developed CLAD and 10 remained stable during the follow-up period of 3 to 4.5 years. Albumin (ALB), alpha1-antitrypsin (AAT), high sensitivity C-reactive protein (CRPH), antithrombin-3 (AT3), ceruloplasmin (CER), and alpha2-macroglobulin (A2MG) were measured by the nephelometric method. We found that within the first six months post-transplantation, levels of A2MG, CER and AAT were higher in stable patients relative to those who later developed CLAD. Moreover, in stable patient's plasma CRPH levels decreased during the follow-up period whereas opposite, in those developing CLAD, the CRPH gradually increased. The ALB levels became significantly lower at the end of the follow-up period in CLAD relative to a stable group. A logistic regression model based on A2MG, CER and AT3 at cut-offs levels of ≥175.5 mg/dL, ≥37.8 mg/dL and ≥27.35 mg/dL enabled to discriminate between stable and CLAD patients with a sensitivity of 87.5%, 100% and 62.5%, and specificity of 65.9%, 72.7% and 79.5%, respectively. We identified A2MG (below 175.5 mg/dL) as an independent predictor of CLAD (hazard ratio 11.5, 95% CI (1.5-91.3), p<0.021). Our findings suggest that profiles of certain APPs may help to predict the development of lung dysfunction at the very early stages after transplantation.

Frequent Homozygous Deletions of Type I Interferon Genes in Pleural Mesothelioma Confer Sensitivity to Oncolytic Measles Virus.

INTRODUCTION: Oncolytic immunotherapy is based on the use of nonpathogenic replicative oncolytic viruses that infect and kill tumor cells exclusively. Recently, we found that the spontaneous oncolytic activity of the Schwarz strain of measles virus (MV) against human malignant pleural mesothelioma (MPM) depends on defects in the antiviral type I interferon (IFN-I) response in tumor cells. METHODS: In this study, we studied three independent human MPM bio-collections to identify the defects in the IFN-I responses in tumor cells. RESULTS: We show that the most frequent defect is the homozygous deletions (HDs) of all the 14 IFN-I genes (IFN-α and IFN-ß) that we found in more than half of MV-sensitive MPM cell lines. These HDs occur together with the HDs of the tumor suppressor gene CDKN2A also located in the 9p21.3 chromosome region. Therefore, the IFN-I-/- MPM cell lines develop a partial and weak IFN-I response when they are exposed to the virus compared with that of normal cells and MV-resistant MPM cell lines. This response consists of the expression of a restricted number of IFN-stimulated genes that do not depend on the presence of IFN-I. In addition, the IFN-I-/- MPM cell lines infected by MV also develop a pro-inflammatory response associated with stress of the endoplasmic reticulum. CONCLUSION: Our study emphasizes the link between HDs of IFN-I encoding genes and the CDKN2A gene in MPM and sensitivity to MV oncolytic immunotherapy.

High neutralizing potency of swine glyco-humanized polyclonal antibodies against SARS-CoV-2.

Perfusion of convalescent plasma (CP) has demonstrated a potential to improve the pneumonia induced by SARS-CoV-2, but procurement and standardization of CP are barriers to its wide usage. Many monoclonal antibodies (mAbs) have been developed but appear insufficient to neutralize SARS-CoV-2 unless two or three of them are being combined. Therefore, heterologous polyclonal antibodies of animal origin, that have been used for decades to fight against infectious agents might represent a highly efficient alternative to the use of CP or mAbs in COVID-19 by targeting multiple antigen epitopes. However, conventional heterologous polyclonal antibodies trigger human natural xenogeneic antibody responses particularly directed against animal-type carbohydrate epitopes, mainly the N-glycolyl form of the neuraminic acid (Neu5Gc) and the Gal α1,3-galactose (αGal), ultimately forming immune complexes and potentially leading to serum sickness or allergy. To circumvent these drawbacks, we engineered animals lacking the genes coding for the cytidine monophosphate-N-acetylneuraminic acid hydroxylase (CMAH) and α1,3-galactosyl-transferase (GGTA1) enzymes to produce glyco-humanized polyclonal antibodies (GH-pAb) lacking Neu5Gc and α-Gal epitopes. We found that pig IgG Fc domains fail to interact with human Fc receptors and thereby should confer the safety advantage to avoiding macrophage dependent exacerbated inflammatory responses, a drawback possibly associated with antibody responses against SARS-CoV-2 or to avoiding a possible antibody-dependent enhancement (ADE). Therefore, we immunized CMAH/GGTA1 double knockout (DKO) pigs with the SARS-CoV-2 spike receptor-binding domain (RBD) to elicit neutralizing antibodies. Animals rapidly developed a hyperimmune response with anti-SARS-CoV-2 end-titers binding dilutions over one to a million and end-titers neutralizing dilutions of 1:10,000. The IgG fraction purified and formulated following clinical Good Manufacturing Practices, named XAV-19, neutralized Spike/angiotensin converting enzyme-2 (ACE-2) interaction at a concentration < 1µg/mL and inhibited infection of human cells by SARS-CoV-2 in cytopathic assays. These data and the accumulating safety advantages of using glyco-humanized swine antibodies in humans warranted clinical assessment of XAV-19 to fight against COVID-19.

In Vivo Analysis of Human Immune Responses in Immunodeficient Rats.

BACKGROUND: Humanized immune system immunodeficient mice have been extremely useful for the in vivo analyses of immune responses in a variety of models, including organ transplantation and graft versus host disease (GVHD) but they have limitations. Rat models are interesting complementary alternatives presenting advantages over mice, such as their size and their active complement compartment. Immunodeficient rats have been generated but human immune responses have not yet been described. METHODS: We generated immunodeficient Rat Rag-/- Gamma chain-/- human signal regulatory protein alpha-positive (RRGS) rats combining Rag1 and Il2rg deficiency with the expression of human signal regulatory protein alpha, a negative regulator of macrophage phagocytosis allowing repression of rat macrophages by human CD47-positive cells. We then immune humanized RRGS animals with human peripheral blood mononuclear cells (hPBMCs) to set up a human acute GVHD model. Treatment of GVHD was done with a new porcine antihuman lymphocyte serum active through complement-dependent cytotoxicity. We also established a tumor xenograft rejection model in these hPBMCs immune system RRGS animals by subcutaneous implantation of a human tumor cell line. RESULTS: RRGS animals receiving hPBMCs showed robust and reproducible reconstitution, mainly by T and B cells. A dose-dependent acute GVHD process was observed with progressive weight loss, tissue damage, and death censoring. Antihuman lymphocyte serum (L1S1) antibody completely prevented acute GVHD. In the human tumor xenograft model, detectable tumors were rejected upon hPBMCs injection. CONCLUSIONS: hPBMC can be implanted in RRGS animals and elicit acute GVHD or rejection of human tumor cells and these are useful models to test new immunotherapies.

High circulating CD4+CD25hiFOXP3+ T-cell sub-population early after lung transplantation is associated with development of bronchiolitis obliterans syndrome.

BACKGROUND: Chronic bronchiolitis obliterans syndrome (BOS) remains a major limitation for long-term survival after lung transplantation. The immune mechanisms involved and predictive biomarkers have yet to be identified. The purpose of this study was to determine whether peripheral blood T-lymphocyte profile could predict BOS in lung transplant recipients. METHODS: An in-depth profiling of CD4+ and CD8+ T cells was prospectively performed on blood cells from stable (STA) and BOS patients with a longitudinal follow-up. Samples were analyzed at 1 and 6 months after transplantation, at the time of BOS diagnosis, and at an intermediate time-point at 6 to 12 months before BOS diagnosis. RESULTS: Although no significant difference was found for T-cell compartments at BOS diagnosis or several months beforehand, we identified an increase in the CD4+CD25hiFoxP3+ T-cell sub-population in BOS patients at 1 and 6 months after transplantation (3.39 ± 0.40% vs 1.67 ± 0.22% in STA, p < 0.001). A CD4+CD25hiFoxP3+ T-cell threshold of 2.4% discriminated BOS and stable patients at 1 month post-transplantation. This was validated on a second set of patients at 6 months post-transplantation. Patients with a proportion of CD4+CD25hiFoxP3+ T cells up to 2.4% in the 6 months after transplantation had a 2-fold higher risk of developing BOS. CONCLUSIONS: This study is the first to report an increased proportion of circulating CD4+CD25hiFoxP3+ T cells early post-transplantation in lung recipients who proceed to develop BOS within 3 years, which supports its use as a BOS predictive biomarker.

Airway microbiota signals anabolic and catabolic remodeling in the transplanted lung.

BACKGROUND: Homeostatic turnover of the extracellular matrix conditions the structure and function of the healthy lung. In lung transplantation, long-term management remains limited by chronic lung allograft dysfunction, an umbrella term used for a heterogeneous entity ultimately associated with pathological airway and/or parenchyma remodeling. OBJECTIVE: This study assessed whether the local cross-talk between the pulmonary microbiota and host cells is a key determinant in the control of lower airway remodeling posttransplantation. METHODS: Microbiota DNA and host total RNA were isolated from 189 bronchoalveolar lavages obtained from 116 patients post lung transplantation. Expression of a set of 11 genes encoding either matrix components or factors involved in matrix synthesis or degradation (anabolic and catabolic remodeling, respectively) was quantified by real-time quantitative PCR. Microbiota composition was characterized using 16S ribosomal RNA gene sequencing and culture. RESULTS: We identified 4 host gene expression profiles, among which catabolic remodeling, associated with high expression of metallopeptidase-7, -9, and -12, diverged from anabolic remodeling linked to maximal thrombospondin and platelet-derived growth factor D expression. While catabolic remodeling aligned with a microbiota dominated by proinflammatory bacteria (eg, Staphylococcus, Pseudomonas, and Corynebacterium), anabolic remodeling was linked to typical members of the healthy steady state (eg, Prevotella, Streptococcus, and Veillonella). Mechanistic assays provided direct evidence that these bacteria can impact host macrophage-fibroblast activation and matrix deposition. CONCLUSIONS: Host-microbes interplay potentially determines remodeling activities in the transplanted lung, highlighting new therapeutic opportunities to ultimately improve long-term lung transplant outcome.

Blood Gene Expression Predicts Bronchiolitis Obliterans Syndrome.

Bronchiolitis obliterans syndrome (BOS), the main manifestation of chronic lung allograft dysfunction, leads to poor long-term survival after lung transplantation. Identifying predictors of BOS is essential to prevent the progression of dysfunction before irreversible damage occurs. By using a large set of 107 samples from lung recipients, we performed microarray gene expression profiling of whole blood to identify early biomarkers of BOS, including samples from 49 patients with stable function for at least 3 years, 32 samples collected at least 6 months before BOS diagnosis (prediction group), and 26 samples at or after BOS diagnosis (diagnosis group). An independent set from 25 lung recipients was used for validation by quantitative PCR (13 stables, 11 in the prediction group, and 8 in the diagnosis group). We identified 50 transcripts differentially expressed between stable and BOS recipients. Three genes, namely POU class 2 associating factor 1 (POU2AF1), T-cell leukemia/lymphoma protein 1A (TCL1A), and B cell lymphocyte kinase, were validated as predictive biomarkers of BOS more than 6 months before diagnosis, with areas under the curve of 0.83, 0.77, and 0.78 respectively. These genes allow stratification based on BOS risk (log-rank test p < 0.01) and are not associated with time posttransplantation. This is the first published large-scale gene expression analysis of blood after lung transplantation. The three-gene blood signature could provide clinicians with new tools to improve follow-up and adapt treatment of patients likely to develop BOS.

Cell-surface C-type lectin-like receptor CLEC-1 dampens dendritic cell activation and downstream Th17 responses.

Dendritic cells (DCs) represent essential antigen-presenting cells that are critical for linking innate and adaptive immunity, and influencing T-cell responses. Among pattern recognition receptors, DCs express C-type lectin receptors triggered by both exogenous and endogenous ligands, therefore dictating pathogen response, and also shaping T-cell immunity. We previously described in rat, the expression of the orphan C-type lectin-like receptor-1 (CLEC-1) by DCs and demonstrated in vitro its inhibitory role in downstream T helper 17 (Th17) activation. In this study, we examined the expression and functionality of CLEC-1 in human DCs, and show a cell-surface expression on the CD16- subpopulation of blood DCs and on monocyte-derived DCs (moDCs). CLEC-1 expression on moDCs is downregulated by inflammatory stimuli and enhanced by transforming growth factor ß. Moreover, we demonstrate that CLEC-1 is a functional receptor on human moDCs and that although not modulating the spleen tyrosine kinase-dependent canonical nuclear factor-κB pathway, represses subsequent Th17 responses. Interestingly, a decreased expression of CLEC1A in human lung transplants is predictive of the development of chronic rejection and is associated with a higher level of interleukin 17A (IL17A). Importantly, using CLEC-1-deficient rats, we showed that disruption of CLEC-1 signaling led to an enhanced Il12p40 subunit expression in DCs, and to an exacerbation of downstream in vitro and in vivo CD4+ Th1 and Th17 responses. Collectively, our results establish a role for CLEC-1 as an inhibitory receptor in DCs able to dampen activation and downstream effector Th responses. As a cell-surface receptor, CLEC-1 may represent a useful therapeutic target for modulating T-cell immune responses in a clinical setting.

Chronic Lung Allograft Dysfunction: A Systematic Review of Mechanisms.

Chronic lung allograft dysfunction (CLAD) is the major limitation of long-term survival after lung transplantation. Chronic lung allograft dysfunction manifests as bronchiolitis obliterans syndrome or the recently described restrictive allograft syndrome. Although numerous risk factors have been identified so far, the physiopathological mechanisms of CLAD remain poorly understood. We investigate here the immune mechanisms involved in the development of CLAD after lung transplantation. We explore the innate or adaptive immune reactions induced by the allograft itself or by the environment and how they lead to allograft dysfunction. Because current literature suggests bronchiolitis obliterans syndrome and restrictive allograft syndrome as 2 distinct entities, we focus on the specific factors behind one or the other syndromes. Chronic lung allograft dysfunction is a multifactorial disease that remains irreversible and unpredictable so far. We thus finally discuss the potential of systems-biology approach to predict its occurrence and to better understand its underlying mechanisms.

Sensitivity of human pleural mesothelioma to oncolytic measles virus depends on defects of the type I interferon response.

Attenuated measles virus (MV) is currently being evaluated as an oncolytic virus in clinical trials and could represent a new therapeutic approach for malignant pleural mesothelioma (MPM). Herein, we screened the sensitivity to MV infection and replication of twenty-two human MPM cell lines and some healthy primary cells. We show that MV replicates in fifteen of the twenty-two MPM cell lines. Despite overexpression of CD46 by a majority of MPM cell lines compared to healthy cells, we found that the sensitivity to MV replication did not correlate with this overexpression. We then evaluated the antiviral type I interferon (IFN) responses of MPM cell lines and healthy cells. We found that healthy cells and the seven insensitive MPM cell lines developed a type I IFN response in presence of the virus, thereby inhibiting replication. In contrast, eleven of the fifteen sensitive MPM cell lines were unable to develop a complete type I IFN response in presence of MV. Finally, we show that addition of type I IFN onto MV sensitive tumor cell lines inhibits replication. These results demonstrate that defects in type I IFN response are frequent in MPM and that MV takes advantage of these defects to exert oncolytic activity.

Nuclear trafficking, histone cleavage and induction of apoptosis by the meningococcal App and MspA autotransporters.

Neisseria meningitidis, a major cause of bacterial meningitis and septicaemia, secretes multiple virulence factors, including the adhesion and penetration protein (App) and meningococcal serine protease A (MspA). Both are conserved, immunogenic, type Va autotransporters harbouring S6-family serine endopeptidase domains. Previous work suggested that both could mediate adherence to human cells, but their precise contribution to meningococcal pathogenesis was unclear. Here, we confirm that App and MspA are in vivo virulence factors since human CD46-expressing transgenic mice infected with meningococcal mutants lacking App, MspA or both had improved survival rates compared with mice infected with wild type. Confocal imaging showed that App and MspA were internalized by human cells and trafficked to the nucleus. Cross-linking and enzyme-linked immuno assay (ELISA) confirmed that mannose receptor (MR), transferrin receptor 1 (TfR1) and histones interact with MspA and App. Dendritic cell (DC) uptake could be blocked using mannan and transferrin, the specific physiological ligands for MR and TfR1, whereas in vitro clipping assays confirmed the ability of both proteins to proteolytically cleave the core histone H3. Finally, we show that App and MspA induce a dose-dependent increase in DC death via caspase-dependent apoptosis. Our data provide novel insights into the roles of App and MspA in meningococcal infection.

Deciphering the complex three-way interaction between the non-integrin laminin receptor, galectin-3 and Neisseria meningitidis.

The non-integrin laminin receptor (LAMR1/RPSA) and galectin-3 (Gal-3) are multi-functional host molecules with roles in diverse pathological processes, particularly of infectious or oncogenic origins. Using bimolecular fluorescence complementation and confocal imaging, we demonstrate that the two proteins homo- and heterodimerize, and that each isotype forms a distinct cell surface population. We present evidence that the 37 kDa form of LAMR1 (37LRP) is the precursor of the previously described 67 kDa laminin receptor (67LR), whereas the heterodimer represents an entity that is distinct from this molecule. Site-directed mutagenesis confirmed that the single cysteine (C(173)) of Gal-3 or lysine (K(166)) of LAMR1 are critical for heterodimerization. Recombinant Gal-3, expressed in normally Gal-3-deficient N2a cells, dimerized with endogenous LAMR1 and led to a significantly increased number of internalized bacteria (Neisseria meningitidis), confirming the role of Gal-3 in bacterial invasion. Contact-dependent cross-linking determined that, in common with LAMR1, Gal-3 binds the meningococcal secretin PilQ, in addition to the major pilin PilE. This study adds significant new mechanistic insights into the bacterial-host cell interaction by clarifying the nature, role and bacterial ligands of LAMR1 and Gal-3 isotypes during colonization.