Oral delivery of xeno-antigen combined with non-depleting anti-CD4 monoclonal antibody induces significantly prolonged survival of concordant skin xenograft

Abstract: Oral administration can induce unresponsiveness to protein antigens. Therefore, we examined whether oral administration of xeno-antigen could induce the prolonged survival of xenogeneic skin grafts. CBA mice were given 1 × 10⁷ SD rat splenocytes orally, 7 days before transplantation of a SD rat skin in the presence or absence of a non-depleting anti-CD4 monoclonal antibody (mAb) (YTS177, 200 µg/dose, −8 and −7 days relative to transplantation). All skin grafts survived with a median survival time (MST) of 62 days when xeno-antigens were administered orally in combination with anti-CD4 mAb. Mice treated with anti-CD4 mAb alone or oral administration of xeno-antigen alone induced modest prolonged survival of rat skin grafts (MST = 18 and 19 days, respectively) while naive mice rejected rat skin acutely (MST = 12 days). Oral administration alone or combined with anti-CD4 mAb reduced the level of xeno-antibody production compared with that in untreated mice after transplantation. Xenogeneic mixed leukocyte response was reduced when splenocytes from mice pre-treated with oral administration of xenogeneic cells were used as the responder compared with that in untreated mice. Oral delivery of xeno-antigen plus non-depleting anti-CD4 mAb can induce prolongation of concordant xenogeneic skin grafts.     

Removal of bowel aerobic gram-negative bacteria is more effective than immunosuppression with cyclophosphamide and steroids to decrease natural alpha-galactosyl IgG antibodies

Abstract: Natural α-Galactosyl (Gal) antibodies play an important role in the rejection of pig xenografts by humans and Old World monkeys. In this study we investigate the efficacy of two different strategies to reduce the serum level of natural anti-Gal antibodies. On the one hand, removal of aerobic gram-negative bacteria from the intestinal flora, because anti-Gal antibodies appear to be produced as a result of the continuous sensitization by these microorganisms. On the other hand, we studied the effect on these antibodies of an immunosuppressive regimen of cyclophosphamide and steroids. Ten baboons were treated for three months with norfloxacin (Nor Group; n = 6) or cyclophosphamide and steroids (CyP Group; n = 4). A further four baboons did not receive any treatment (Control Group). Aerobic gram-negative bacteria became negative in stools of the Nor Group after two weeks of treatment, and remained undetectable until week 7. Thereafter, a gradual increase on the fecal concentration of aerobic gram-negative bacteria was observed despite the norfloxacin treatment. The mean anti-Gal IgG in the Nor Group gradually declined from week 4 to 9 to a mean of 62.7 ± 18% of the baseline level, and during this period were significantly lower than in the CyP ( P  < 0.02) and the Control ( P  < 0.05) groups. No differences were observed between the three groups during the 16 weeks of follow-up in serum levels of anti-Gal IgM, hemolytic anti-pig antibodies, total IgG, IgM and IgA. In conclusion, removal of normal aerobic gram-negative bacteria from the intestinal flora is more effective than immunosuppression with CyP and steroids in reducing the level of natural anti-Gal antibodies, although there is no discernible effect on IgM antibodies.     

Morphometric analysis of miniature swine hearts as potential human xenografts

Abstract: Miniature swine are considered to be potential donors for clinical cardiac transplantation. However, it is unclear how an appropriately sized porcine donor will be selected for a particular human recipient. To address this issue, we performed a morphometric study of the swine heart using transthoracic echocardiography (n = 26) to determine the diameters of the aortic annulus and root, pulmonary artery annulus, and mitral valve annulus. We also obtained direct ex vivo measurements of swine heart weight and linear dimensions (n = 71). Relationships between a swine's height, weight, length, chest circumference and these internal and external cardiac dimensions are described. The strongest correlations were found between a pig's body length and its aortic annulus and root diameters (r-values = 0.97). These relationships are accurately described by univariate linear regression models. By cross-relating our morphometric measurements of aortic annulus diameter in the miniature swine with normative human data, we were able to develop a nomogram, relating swine length and human height, which predicts which miniature swine would donate the best size-matched heart for a particular human recipient.     

Effects of specific anti-B and/or anti-plasma cell immunotherapy on antibody production in baboons: depletion of CD20- and CD22-positive B cells does not result in significantly decreased production of anti-alphaGal antibody

Anti-Galalpha1-3Gal antibodies (antialphaGal Ab) are a major barrier to clinical xenotransplantation as they are believed to initiate both hyperacute and acute humoral rejection. Extracorporeal immunoadsorption (EIA) with alphaGal oligosaccharide columns temporarily depletes antialphaGal Ab, but their return is ultimately associated with graft destruction. We therefore assessed the ability of two immunotoxins (IT) and two monoclonal antibodies (mAb) to deplete B and/or plasma cells both in vitro and in vivo in baboons, and to observe the rate of return of antialphaGal Ab following EIA. The effects of the mouse anti-human IT anti-CD22-ricin A (proportional to CD22-IT, directed against a B cell determinant) and anti-CD38-ricin A (proportional to CD38-IT, B and plasma cell determinant) and the mouse anti-human anti-CD38 mAb (proportional to CD38 mAb) and mouse/human chimeric anti-human anti-CD20 mAb (proportional to CD20 mAb, Rituximab, B cell determinant) on B and plasma cell depletion and antialphaGal Ab production were assessed both in vitro and in vivo in baboons (n = 9) that had previously undergone splenectomy. For comparison, two baboons received nonmyeloablative whole body irradiation (WBI) (300 cGy), and one received myeloablative WBI (900 cGy). Depletion of B cells was monitored by flow cytometry of blood, bone marrow (BM) and lymph nodes (LN), staining with anti-CD20 and/or anti-CD22 mAbs, and by histology of LN. EIA was carried out after the therapy and antialphaGal Ab levels were measured daily. In vitro proportional to CD22-IT inhibited protein synthesis in the human Daudi B cell line more effectively than proportional to CD38-IT. Upon differentiation of B cells into plasma cells, however, less inhibition of protein synthesis after proportional to CD22-IT treatment was observed. Depleting CD20-positive cells in vitro from a baboon spleen cell population already depleted of granulocytes, monocytes, and T cells led to a relative enrichment of CD20-negative cells, that is plasma cells, and consequently resulted in a significant increase in antialphaGal Ab production by the remaining cells, whereas depleting CD38-positive cells resulted in a significant decrease in antialphaGal Ab production. In vivo, WBI (300 or 900 cGy) resulted in 100% B cell depletion in blood and BM, > 80% depletion in LN, with substantial recovery of B cells after 21 days and only transient reduction in antialphaGal Ab after EIA. Proportional to CD22-IT depleted B cells by > 97% in blood and BM, and by 60% in LN, but a rebound of B cells was observed after 14 and 62 days in LN and blood, respectively. At 7 days, serum antialphaGal IgG and IgM Ab levels were reduced by a maximum of 40-45% followed by a rebound to levels up to 12-fold that of baseline antialphaGal Ab by day 83 in one baboon. The results obtained with proportional to CD38-IT were inconclusive. This may have been, in part, due to inadequate conjugation of the toxin. Cell coating was 100% with proportional to CD38 mAb, but no changes in antialphaGal Ab production were observed. Proportional to CD20 mAb resulted in 100% depletion of B cells in blood and BM, and 80% in LN, with recovery of B cells starting at day 42. Adding 150cGy WBI at this time led to 100% depletion of B cells in the BM and LN. Although B cell depletion in blood and BM persisted for > 3 months, the reduction of serum antialphaGal IgG or IgM Ab levels was not sustained beyond 2 days. Proportional to CD20 mAb + WBI totally and efficiently depleted CD20- and CD22-positive B cells in blood, BM, and LN for > 3 months in vivo, but there was no sustained clinically significant reduction in serum antialphaGal Ab. The majority of antibody secretors are CD38-positive cells, but targeting these cells in vitro or in vivo with proportional to CD38-IT was not very effective. These observations suggest that CD20-and CD22-positive B cells are not the major source of antialphaGal Ab production. Future efforts will be directed towards suppression of plasma cell function.     

大鼠胰岛与生长因子共微囊提高囊内胰岛存活率

目的 探讨微胶囊胰岛皮下移植治疗化学性糖尿病小鼠和生长因子(growth factor,GF)与大鼠胰岛共微囊对提高囊内胰岛存活率的作用.方法 选取C57BL/6雄性小鼠皮下预血管化糖尿病模型25只,行微胶囊大鼠胰岛皮下移植.随机分为5组,每组5只.①A组:GF与大鼠胰岛共微囊移植组;②B组:微胶囊大鼠胰岛移植组;③C组:GF微囊移植组;④D组:大鼠胰岛移植组;⑤E组:空囊移植组.观察受体小鼠的血糖和体重变化,移植后8周比较微胶囊内胰岛存活数.结果 移植后1周至移植后3周A组与B组间血糖均有非常显著差异(P＜0.01),移植后4周至移植后8周A组与B组间血糖无显著差异(P＞0.05),移植后1周至移植后4周B组与C组间血糖均有非常显著差异(P＜0.01).C组血糖异常升高,移植4周后小鼠陆续死亡.D组和E组移植无效.A组和B组间各实验点小鼠体重均无显著差异(P＞0.05),A组小鼠体重成模时下降,移植2周后开始上升.A组和B组胰岛存活数有非常显著差异(F=36.84,P＜0.01).结论 GF与大鼠胰岛共微胶囊移植,GF可促进胰岛的细胞增殖和再生,显著提高囊内胰岛的存活率.     

Role of microcirculation in transplantation

Microcirculatory derangements in organ transplantation, characterized by capillary perfusion failure and inflammation-associated leukocyte recruitment, are major determinants for the manifestation of graft dysfunction and destruction. Although preservation/cold storage, posttransplant reperfusion, and rejection have to be considered as individual factors that contribute to injury, recent studies have indicated that ischemia-reperfusion-associated events may trigger immune-response-mediated late rejection. There is major evidence that the microcirculatory derangements induced by cold preservation and reperfusion involve oxygen radicals, complement, phospholipase A2, leukotrienes, thromboxane, platelet-activating factor, and endothelin-1 as well as the activation and function of leukocytic and endothelial selectins, beta 2-integrins, and ICAM-1. This view is based on the fact that blockade or neutralization of these inflammatory mediators and adhesion molecules results in significant amelioration of microvascular graft dysfunction. In parallel, rejection-mediated microcirculatory derangements may not only be ameliorated by immunosuppressive agents, such as cyclosporin, deoxyspergualin, or RS61443, but may, in addition, effectively be inhibited by counteracting oxygen radicals, complement, platelet-activating factor, and adhesion molecules. The introduction of novel techniques for the study of the microcirculation in men, such as thermodiffusion and orthogonal polarization spectral imaging, may in the future assist in improving both early diagnosis of microcirculatory derangements and monitoring of appropriateness of therapy in clinical transplantation surgery.     

Xenotransplantation literature update: February–March, 2010

Schneider MKJ, Seebach JD. Xenotransplantation literature update: February–March, 2010.
Xenotransplantation 2010; 17: 256–260. © 2010 John Wiley & Sons A/S.     

Use of primary human fetal chondroblast culture for xenotransplantation into rat articular cartilage defect

The possibility of xenotransplantation of human fetal chondroblasts was studied. Filling of the rat articular cartilage defect with a tissue-engineering construction based on primary culture of human fetal chondroblasts and chitosan gel caused no immune rejection over 60 days and provided the formation of organotypical regenerate due to proliferation and differentiation of donor fetal chondroblasts and their integration in the recipient cartilage tissue. Translated from Kletochnye Tehnologii v Biologii i Medicine, No. 3, pp. 136–140, August, 2008     

Short Communication: Pig islet xenotransplantation acceptance in a Latin‐American diabetic population

Abalovich A, Wechsler C, Lara S, Bervottini M. Pig islet xenotransplantation acceptance in a Latin‐American diabetic population. Xenotransplantation 2010; 17: 263–266. © 2010 John Wiley & Sons A/S. Abstract: Progress in porcine islet xenotransplantation has been accompanied by studies on acceptance of this new procedure by patients, health professionals or the general public. Such studies have not been done in the Latin‐American population. We conducted a questionnaire in 108 diabetes patients (insulin‐dependent, n = 53; insulin‐independent, n = 55) in a public hospital in Argentina. The questions addressed the general perception of the xenotransplant procedure and specific items related to the outcome (achieving insulin independence, improvement in metabolic control, delay in emergence of diabetic complications, need for repeat procedures, potential of transfer of infectious viruses, association with psychological problems, and anticipated success in relation to achieving a cure). Eighty‐six (79%) of the patients accepted islet xenotransplantation; this incidence was not different for insulin‐dependent or insulin‐independent patients, patients with or without complications, or patients with good or poor metabolic control. Also, over 75% of patients accepted the procedure if this is only associated with a reduction in insulin requirement, if the procedure just delays but not prevents the onset of complications, or if the procedure needs to be performed every 6 months. Fifty‐seven percent of patients indicated acceptance even if the potential transmission of a virus infection cannot be completely ruled out: this outcome was not affected by the outbreak of the H1N1 flu epidemic during the conduct of this study. Forty percent of patients indicated that living with porcine cells in their body could give psychological problems. We conclude that this population of Latin‐American diabetic patients shows a high acceptance rate of a porcine islet xenotransplantation product.     

In vitro investigation of pig cells for resistance to human antibody‐mediated rejection

Although human complement‐dependent cytotoxicity (CDC) of α1,3‐galactosyltransferase gene‐knockout (GTKO) pig cells is significantly weaker than that of wild‐type (WT) cells, successful xenotransplantation will require pigs with multiple genetic modifications. Sera from healthy humans were tested by (i) flow cytometry for binding of IgM/IgG, and (ii) CDC assay against peripheral blood mononuclear cells and porcine aortic endothelial cells from five types of pig – WT, GTKO, GTKO transgenic for H‐transferase (GTKO/HT), WT transgenic for human complement regulatory protein CD46 (CD46) and GTKO/CD46. There was significantly higher mean IgM/IgG binding to WT and CD46 cells than to GTKO, GTKO/HT, and GTKO/CD46, but no difference between GTKO, GTKO/HT, and GTKO/CD46 cells. There was significantly higher mean CDC to WT than to GTKO, GTKO/HT, CD46, and GTKO/CD46 cells, but no difference between GTKO and GTKO/HT. Lysis of GTKO/CD46 cells was significantly lower than that of GTKO or CD46 cells. CD46 expression provided partial protection against serum from a baboon sensitized to a GTKO pig heart. GTKO/CD46 cells were significantly resistant to lysis by human serum and sensitized baboon serum. In conclusion, the greatest protection from CDC was obtained by the combination of an absence of Gal expression and the presence of CD46 expression, but the expression of HT appeared to offer no advantage over GTKO. Organs from GTKO/CD46 pigs are likely to be significantly less susceptible to CDC.