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Plasma bilirubin (a), creatinine (b) and LDH (c) levels and platelet counts (d), non-suggestive of thrombotic microangiopathy. There were no signs of liver or kidney damage. The increase in LDH in animal #17020 at the end of the experiment was caused by humoral rejection. LDH, lactate dehydrogenase.
Source publication
The blockade of the CD40/CD40L immune checkpoint is considered essential for cardiac xenotransplantation. However, it is still unclear which single antibody directed against CD40 or CD40L (CD154), or which combination of antibodies, is better at preventing organ rejection. For example, the high doses of antibody administered in previous experiments...
Citations
... Although this approach initially proves effective, CD8 + T cells proliferate rapidly following T cell depletion therapies, with the majority comprising effector-memory T cells [128]. This was recently confirmed in a pig-to-baboon genetically modified porcine kidney and heart transplantation models [10,[129][130][131]. ...
Xenotransplantation represents a potential solution to the shortage of organs for transplantation. The recent advancements in porcine genetic modification have addressed hyperacute and acute vascular rejection; however, challenges persist with regard to delayed xenograft rejection. Porcine endothelial cells (pECs) represent a crucial target in the context of xenograft rejection, which is mediated by cytotoxic lymphocytes. It is crucial to comprehend the manner in which human natural killer (NK) cells and cytotoxic CD8 ⁺ T lymphocytes (CTL) recognize and target pECs in order to develop efficacious prophylactic strategies against rejection. The objective of the present review is to synthesize the existing knowledge regarding the mechanisms and techniques employed to modulate xenogeneic responses mediated by human NK cells and CTL. We will elucidate recent methodological advancements, debate potential novel strategies, and emphasize the imperative necessity for further research and innovative approaches to enhance graft survival.
... Various PASylated biologics have been produced in diverse commercially established expression platforms such as E. coli [123], P. fluorescens [59], Gram-positive bacteria like C. glutamicum [121], yeast [122] as well as mammalian cell culture (CHO and HEK cells) [124]. PASylation is safe and well tolerated in animals as tested in many different species from rodents to cynomolgus monkeys [125], rhesus macaques [126] and baboons [127]. Applications of PASylation technology published so far range from the PK optimization of tumor imaging agents [128][129][130] to the half-life extension of wellknown biologics, including cytokines [131][132][133], enzymes [124,134], antibody fragments [58,135,136], alternative binding proteins [137][138][139], peptides [140,141] and various peptide/protein hormones [123,142,143], to the shielding of nanoparticles [144,145] and liposomes [146]. ...
Introduction:
Engineering of the drug half-life in vivo has become an integral part of modern biopharmaceutical development due to the fact that many proteins/peptides with therapeutic potential are quickly cleared by kidney filtration after injection and, thus, circulate only a few hours in humans (or just minutes in mice).
Areas covered:
Looking at the growing list of clinically approved biologics that have been modified for prolonged activity, and also the plethora of such drugs under preclinical and clinical development, it is evident that not one solution fits all needs, owing to the vastly different structural features and functional properties of the pharmacologically active entities. This article provides an overview of established half-life extension strategies, as well as of emerging novel concepts for extending the in vivo stability of biologicals, and their pros and cons.
Expert opinion:
Beyond the classical and still dominating technologies for improving drug pharmacokinetics and bioavailability, Fc fusion and PEGylation, various innovative approaches that offer advantages in different respects have entered the clinical stage. While the Fc fusion partner may be gradually superseded by engineered albumin-binding domains, chemical PEGylation may be replaced by biodegradable recombinant amino-acid polymers like PASylation, thus also offering a purely biotechnological manufacturing route.
Introduction
Inflammatory responses and coagulation disorders are a relevant challenge for successful cardiac xenotransplantation on its way to the clinic. To cope with this, an effective and clinically practicable anti‐inflammatory and anti‐coagulatory regimen is needed. The inflammatory and coagulatory response can be reduced by genetic engineering of the organ‐source pigs. Furthermore, there are several therapeutic strategies to prevent or reduce inflammatory responses and coagulation disorders following xenotransplantation. However, it is still unclear, which combination of drugs should be used in the clinical setting.
To elucidate this, we present data from pig‐to‐baboon orthotopic cardiac xenotransplantation experiments using a combination of several anti‐inflammatory drugs.
Methods
Genetically modified piglets (GGTA1‐KO, hCD46/hTBM transgenic) were used for orthotopic cardiac xenotransplantation into captive‐bred baboons ( n = 14). All animals received an anti‐inflammatory drug therapy including a C1 esterase inhibitor, an IL‐6 receptor antagonist, a TNF‐α inhibitor, and an IL‐1 receptor antagonist. As an additive medication, acetylsalicylic acid and unfractionated heparin were administered. The immunosuppressive regimen was based on CD40/CD40L co‐stimulation blockade. During the experiments, leukocyte counts, levels of C‐reactive protein (CRP) as well as systemic cytokine and chemokine levels and coagulation parameters were assessed at multiple timepoints. Four animals were excluded from further data analyses due to porcine cytomegalovirus/porcine roseolovirus (PCMV/PRV) infections ( n = 2) or technical failures ( n = 2).
Results
Leukocyte counts showed a relevant perioperative decrease, CRP levels an increase. In the postoperative period, leukocyte counts remained consistently within normal ranges, CRP levels showed three further peaks after about 35, 50, and 80 postoperative days. Analyses of cytokines and chemokines revealed different patterns. Some cytokines, like IL‐8, increased about 2‐fold in the perioperative period, but then decreased to levels comparable to the preoperative values or even lower. Other cytokines, such as IL‐12/IL‐23, decreased in the perioperative period and stayed at these levels. Besides perioperative decreases, there were no relevant alterations observed in coagulation parameters. In summary, all parameters showed an unremarkable course with regard to inflammatory responses and coagulation disorders following cardiac xenotransplantation and thus showed the effectiveness of our approach.
Conclusion
Our preclinical experience with the anti‐inflammatory drug therapy proved that controlling of inflammation and coagulation disorders in xenotransplantation is possible and well‐practicable under the condition that transmission of pathogens, especially of PCMV/PRV to the recipient is prevented because PCMV/PRV also induces inflammation and coagulation disorders. Our anti‐inflammatory regimen should also be applicable and effective in the clinical setting of cardiac xenotransplantation.
