Potential deleterious role of anti-Neu5Gc antibodies in xenotransplantation

International audienceHuman beings do not synthesize the glycolyl form of the sialic acid (Neu5Gc) and only express the acetylated form of the sugar, whereas a diet-based intake of Neu5Gc provokes a natural immunization and production of anti-Neu5Gc antibodies in human serum. However , Neu5Gc is expressed on mammal glycoproteins and glycolipids in most organs and cells. We review here the relevance of Neu5Gc and anti-Neu5Gc antibodies in the context of xenotransplantation and the use of animal-derived molecules and products, as well as the possible consequences of a long-term exposure to anti-Neu5Gc antibodies in recipients of xenografts. In addition, the importance of an accurate estimation of the anti-Neu5Gc response following xenotransplantation and the future contribution of knockout animals mimicking the human situation are also assessed

Increased IGM and IGG anti-NEU5GC antibodies in infectious mononucleosis (IMN): link with multiple sclerosis (MS)?

International audienceIntroduction: Multiple Sclerosis (MS) is a chronic inflammatory and demyelinating disease which displays an autoimmune component at its overt clinical stage. Among etiological hypotheses, the potential initiating role of EBV in the disease has been raised following works linking EBNA levels and the risk of MS occurrence [1] showing a linkage between the occurrence of IMN and MS. Our hypothesis is that a vigorous production of anti-Neu5Gc in IMN (as indirectly measured by Paul-Bunnell Davidson reaction) may induce brain blood barrier alterations when the EBV primo-infection is contemporary of an extraordinary high frequency of EBV committed T cells and of circulating EBV+ memory B cells[2]. Our aim was to measure anti-Neu5Gc IgG and IgM levels during the IMN and to investigate whether levels of anti-NeuGc could be also increased in MS. Material and Methods: Sera from 49 patients with overt IMN were collected from the University Hospital of Grenoble and Nantes. The gender ratio was 22F/ 27M. The age average was 24 years (range: 7- 65). Two cohorts of EBV negative individuals (n= 45) and healthy individuals (n= 120) were used as controls. A second cohort of 46 patients with proven MS was collected from the University Hospital of Nantes. The gender ratio was 30F/ 16M. The age average was 48 years (range: 22-73). This cohort contained 30 patients presenting a Remitting Relapsing (RR) form (65.2%) and 16 with a Secondary or Primary Progressive (SP-PP) one (34.7%). A cohort of healthy individuals (n= 37) matched for gender and age was used as controls. On these samples, we performed two Elisa [3][4] to quantify anti-Neu5Gc IgG and IgM antibodies. Results: We showed a highly significant increase in anti-Neu5Gc IgM in IMN patients in comparison to EBV negative controls (0.82±0.16 vs. 0.15±0.05 ng/ul; p<0.0001). Anti-Neu5Gc IgG were also, though less dramatically, increased (3.64±0.6 vs. 2.78±0.57ng/ul; p=0.04). The values obtained in IMN differed significantly to healthy individuals (0.82±0.16 vs. 0.2±0.03 ng/ul;p<0.0001 for IgM and 3.63±0.6 vs. 2.74±0.3 ng/ul; p= 0.01 for IgG). The levels of anti-α1-3Gal epitopes, an other type of «xeno» antibody against a sugar not synthesized by normal individuals were also increased during IMN (12.4±1.1 vs. 9.67±1.46 ng/ul for EBV negative controls and vs. 11.7±3.4 ng/ul for healthy individuals; p<0.0001 for both). We found neither increase in anti-Neu5gc antibodies in this small MS patient cohort (p=0.8 for IgM and p=0.84 for IgG), nor in RR or SP-PP subgroups. We found no correlation between the anti-Neu5Gc titers and age or gender of IMN or MS patients, or of healthy individuals. Conclusion: Despite the fact that EVB does not express Neu5Gc, anti-Neu5Gc antibodies are strongly increased in IMN patients, suggesting that uptake of Neu5Gc from dietary sources by EBV infected cells induces them to become more immunogenic during the acute disease. However our data did not evidence higher anti-Neu5Gc antibodies in established MS

In vivo analysis of human immune responses in immunodeficient rats.

International audienceBACKGROUND: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 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 RRGS rats (for Rat Rag-/- Gamma chain-/- hSIRPa-positive) combining Rag1 and Il2rg deficiency with the expression of human SIRPalpha, a negative regulator of macrophage phagocytosis allowing repression of rat macrophages by human CD47-positive cells. We then immune humanized RRGS animals with human PBMCs to set up a human acute GVHD model. Treatment of GVHD was done with a new porcine anti-human lymphocyte serum (LIS1) active through complement-dependent cytotoxicity. We also established a tumor xenograft rejection model in these human PBMCs immune system RRGS animals by subcutaneous implantation of a human tumor cell line.RESULTS:RRGS animals receiving human PBMCs 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. LIS1 antibody completely prevented acute GVHD. In the human tumor xenograft model, detectable tumors were rejected upon hPBMCs injection.CONCLUSIONS:Human PBMC 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

Anti-Gal and Anti-Neu5Gc Responses in Nonimmunosuppressed Patients After Treatment With Rabbit Antithymocyte Polyclonal IgGs

International audienceBackground. Polyclonal antihuman thymocyte rabbit IgGs (antithymocyte globulin [ATG]) are popular immunosuppressive drugs used to prevent or treat organ or bone-marrow allograft rejection, graft versus host disease, and autoimmune diseases. However, animal-derived glycoproteins are also strongly immunogenic and rabbit ATG induces serum sickness disease in almost all patients without additional immunosuppressive drugs, as seen in the Study of Thymoglobulin to arrest Type 1 Diabetes (START) trial of ATG therapy in new-onset type 1 diabetes.Methods. Using enzyme-linked immunosorbent assay, we analyzed serial sera from the START study to decipher the various anti-ATG specificities developed by the patients in this study: antitotal ATG, but also antigalactose-α1-3-galactose (Gal) and anti-Neu5Gc antibodies, 2 xenocarbohydrate epitopes present on rabbit IgG gly-cans and lacking in humans.Results. We show that diabetic patients have substantial levels of preexisting antibodies of the 3 specificities, before infusion, but of similar levels as healthy individuals. ATG treatment resulted in highly significant increases of both IgM (for anti-ATG and anti-Neu5Gc) and IgG (for anti-ATG,-Gal, and-Neu5Gc), peaking at 1 month and still detectable 1 year postinfusion. Conclusions. Treatment with rabbit polyclonal IgGs in the absence of additional immunosuppression results in a vigorous response against Gal and Neu5Gc epitopes, contributing to an inflammatory environment that may compromise the efficacy of ATG therapy. The results also suggest using IgGs lacking these major xenoantigens may improve safety and efficacy of ATG treatment

Quantitative and qualitative changes in anti‐Neu5Gc antibody response following rabbit anti‐thymocyte IgG induction in kidney allograft recipients

International audienceAntibodies of non-human mammals are glycosylated with carbohydrate antigens, such as galactose-α-1-3-galactose (α-Gal) and N-glycolylneuraminic acid (Neu5Gc). These non-human carbohydrate antigens are highly immunogenic in humans due to loss-of-function mutations of the key genes involved in their synthesis. Such immunogenic carbohydrates are expressed on therapeutic polyclonal rabbit anti-human T-cell IgGs (anti-thymocyte globulin; ATG), the most popular induction treatment in allograft recipients. To decipher the quantitative and qualitative response against these antigens in immunosuppressed patients, particularly against Neu5Gc, which may induce endothelial inflammation in both the graft and the host. We report a prospective study of the antibody response against α-Gal and Neu5Gc-containing glycans following rabbit ATG induction compared to controls. We show a drop in the overall levels of anti-Neu5Gc antibodies at 6 and 12 months post-graft compared to the pre-existing levels due to the major early immunosuppression. However, in contrast, in a cross-sectional study there was a highly significant increase in anti-Neu5Gc IgGs levels at 6 months post-graft in the ATG-treated compared to non-treated patients(P = 0.007), with a clear hierarchy favouring anti-Neu5Gc over anti-Gal response. A sialoglycan microarray analysis revealed that the increased anti-Neu5Gc IgG response was still highly diverse against multiple different Neu5Gc-containing glycans. Furthermore, some of the ATG-treated patients developed a shift in their anti-Neu5Gc IgG repertoire compared with the baseline, recognizing different patterns of Neu5Gc-glycans. In contrast to Gal, Neu5Gc epitopes remain antigenic in severely immunosuppressed patients, who also develop an anti-Neu5Gc repertoire shift. The clinical implications of these observations are discussed

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

International audienceAmino 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

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

International audienceAnti-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 (&lt;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

Increased late graft loss in kidney recipients with serum sickness disease following anti-thymocyte globulin induction: relation with an anti-NEU5GC response

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Increased late graft loss in kidney recipients with serum sickness disease following anti-thymocyte globulin induction: relation with an anti-NEU5GC response

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Anti-EBOV GP IgGs Lacking α1-3-Galactose and Neu5Gc Prolong Survival and Decrease Blood Viral Load in EBOV-Infected Guinea Pigs.

Polyclonal xenogenic IgGs, although having been used in the prevention and cure of severe infectious diseases, are highly immunogenic, which may restrict their usage in new applications such as Ebola hemorrhagic fever. IgG glycans display powerful xenogeneic antigens in humans, for example α1-3 Galactose and the glycolyl form of neuraminic acid Neu5Gc, and IgGs deprived of these key sugar epitopes may represent an advantage for passive immunotherapy. In this paper, we explored whether low immunogenicity IgGs had a protective effect on a guinea pig model of Ebola virus (EBOV) infection. For this purpose, a double knock-out pig lacking α1-3 Galactose and Neu5Gc was immunized against virus-like particles displaying surface EBOV glycoprotein GP. Following purification from serum, hyper-immune polyclonal IgGs were obtained, exhibiting an anti-EBOV GP titer of 1:100,000 and a virus neutralizing titer of 1:100. Guinea pigs were injected intramuscularly with purified IgGs on day 0 and day 3 post-EBOV infection. Compared to control animals treated with IgGs from non-immunized double KO pigs, the anti-EBOV IgGs-treated animals exhibited a significantly prolonged survival and a decreased virus load in blood on day 3. The data obtained indicated that IgGs lacking α1-3 Galactose and Neu5Gc, two highly immunogenic epitopes in humans, have a protective effect upon EBOV infection