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J S Logan

Publications and source records attributed to J S Logan.

At least 37 records · Page 2Linked to original sources
PubMed1997

Swine lungs expressing human complement-regulatory proteins are protected against acute pulmonary dysfunction in a human plasma perfusion model.

UNLABELLED: Pulmonary transplantation is currently limited by the number of suitable cadaver donor lungs. For this reason, pulmonary xenotransplantation is currently being investigated. OBJECTIVE: Our goal was to assess the role of complement in pulmonary xenograft dysfunction. METHODS: The pulmonary function of swine expressing human decay accelerating factor and human CD59 (n = 6) was compared with that of the lungs from nontransgenic (control) swine (n = 6) during perfusion with human plasma. RESULTS: After 2 hours of perfusion, the pulmonary vascular resistance was 1624 +/- 408 dynes.sec.cm-5 in control lungs and 908 +/- 68 dynes.sec.cm-5 in transgenic lungs (p < 0.05). Control lungs had a venous oxygen tension of 271 +/- 23 mm Hg with a ratio of venous oxygen tension to inspired oxygen fraction of 452 +/- 38 at 2 hours of perfusion; transgenic lungs had a venous oxygen tension of 398 +/- 11 mm Hg and a ratio of venous oxygen tension to inspired oxygen fraction of 663 +/- 18 (p < 0.05). Control lungs showed a decrease of 79.8% +/- 3.7% in static pulmonary compliance by 2 hours, versus a 12.0% +/- 8.1% decrease by the transgenic lungs (p < 0.05). The control lungs also developed 561.7 +/- 196.2 ml of airway edema over 2 hours, in contrast to 6.5 +/- 1.7 ml in transgenic lungs (p < 0.05). CONCLUSION: Lungs from swine expressing human decay accelerating factor and human CD59 functioned better than nontransgenic swine lungs when perfused with human plasma. These results suggest that complement activation is involved in producing acute pulmonary xenograft dysfunction and demonstrate that lungs from swine expressing human decay accelerating factor and human CD59 are protected against pulmonary injury when perfused with human plasma.

Animals↗
PubMed1997

Humoral responses to pig-to-baboon cardiac transplantation: implications for the pathogenesis and treatment of acute vascular rejection and for accommodation.

Organs transplanted between phylogenetically-disparate species, such as from the pig into the primate, are subject to hyperacute and acute vascular rejection. Hyperacute rejection of a porcine organ by a primate is thought to be initiated by the binding of xenoreactive natural antibodies to Galalpha1-3Gal expressed on the endothelial lining of blood vessels in the xenograft. The factor(s) which initiates acute vascular rejection is uncertain; however, there is some evidence implicating xenoreactive antibodies. The nature of the humoral response which might contribute to acute vascular rejection of a porcine organ was investigated in baboons which received a porcine cardiac xenograft plus immunosuppression with methylprednisolone, azathioprine, and cyclosporine. Following rejection and surgical removal of the xenografts, the serum concentration of xenoreactive antibodies increased in untreated animals but in immunosuppressed animals was similar to the concentration in preimmune serum. The antibodies in the sensitized recipients were specific for Galalpha1-3Gal (70-95%) and other determinants (5-30%). However, cross-blocking studies showed that, following xenotransplantation, the immunosuppressed baboons had no detectable IgM or IgG directed against "new" endothelial antigens. These results indicate that antibodies made by immunosuppressed individuals in response to xenotransplantation are much like xenoreactive natural antibodies and suggest that acute vascular rejection might in some cases be addressed by therapeutic strategies aimed at those antibodies.

Animals↗
PubMed1997

The role of natural anti-Gal alpha 1-3Gal antibodies in hyperacute rejection of pig-to-baboon cardiac xenotransplants.

Xenoreactive natural antibodies in humans and higher primates are directed predominantly at Gal alpha 1-3Gal. These antibodies are thought to initiate hyperacute rejection of porcine organ xenografts. The contribution of anti-Gal alpha 1-3Gal antibodies to the xenoractive natural antibody repertoire and to the initiation of hyperacute rejection was tested in a pig-to-baboon cardiac xenograft model. Anti-Gal alpha 1-3Gal antibodies were depleted from baboons by extracorporeal absorption of anti-Gal alpha 1-3Gal antibodies from plasma using columns with a matrix bearing Gal alpha 1-3Galb1-4GlcNAc. Specific removal of anti-Gal alpha 1-3Gal antibodies was achieved prior to transplantation as demonstrated by immunoassay. Porcine hearts were then transplanted into these baboons and the outcome of the transplants was analysed. Immunofluorescence revealed little deposition of baboon antibodies in the grafts. The porcine hearts did not undergo hyperacute rejection even though complement activity was approximately 90% of baseline at the time of transplantation. These findings demonstrate that anti-Gal alpha 1-3Gal antibodies constitute a major fraction of xenoreactive natural antibodies in primate blood and that these antibodies contribute significantly to the pathogenesis of hyperacute xenograft rejection.

Acute Disease↗
PubMed1997

CD46 expression does not overcome the intracellular block of measles virus replication in transgenic rats.

The study of measles pathogenesis and the testing of improved vaccine candidates is hampered by the lack of a small animal model which is susceptible to infection by the intranasal route. With the identification of CD46 as a measles virus (MV) receptor, it was feasible to generate transgenic rats to overcome this problem. Although there was widespread expression of CD46 in the transgenic Sprague-Dawley rats, no measles-like disease could be induced after various routes of infection. The expressed transgenic protein was functionally intact since it mediated MV fusion and was downregulated by contact with MV hemagglutinin. In vitro studies revealed that CD46-expressing rat fibroblasts take up MV but do not allow viral replication, which explains the nonpermissiveness of the transgenic rats for in vivo infection.

Animals↗
PubMed1996

Reduction in the level of Gal(alpha1,3)Gal in transgenic mice and pigs by the expression of an alpha(1,2)fucosyltransferase.

Hyperacute rejection of a porcine organ by higher primates is initiated by the binding of xenoreactive natural antibodies of the recipient to blood vessels in the graft leading to complement activation. The majority of these antibodies recognize the carbohydrate structure Gal(alphal,3)Gal (gal epitope) present on cells of pigs. It is possible that the removal or lowering of the number of gal epitopes on the graft endothelium could prevent hyperacute rejection. The Gal(alpha1,3) Gal structure is formed by the enzyme Galbeta1,4GlcNAc3-alpha-D-galactosyltransferase [alpha(1,3)GT; EC 2.4.1.51], which transfers a galactose molecule to terminal N-acetyllactosamine (N-lac) present on various glycoproteins and glycolipids. The N-lac structure might be utilized as an acceptor by other glycosyltransferases such as Galbeta1,4GlcNAc 6-alpha-D-sialyltransferase [alpha(2,6)ST], Galbeta1,4GlcNAc 3-alpha-D-Sialyltransferase [alpha(2,3)ST], or Galbeta 2-alpha-L-fucosyltransferase [alpha(1,2)FT; EC 2.4.1.691, etc. In this report we describe the competition between alpha(1,2)FT and alpha(1,3)GT in cells in culture and the generation of transgenic mice and transgenic pigs that express alpha(1,2)Fr leading to synthesis of Fucalpha,2Galbeta- (H antigen) and a concomitant decrease in the level of Gal(alpha1,3)Gal. As predicted, this resulted in reduced binding of xenoreactive natural antibodies to endothelial cells of transgenic mice and protection from complement mediated lysis.

Animals↗
PubMed1996

Characterization of transgenic pigs expressing functionally active human CD59 on cardiac endothelium.

The critical shortage of human donor organs has generated interest in the potential for porcine to human xenotransplantation. The initial immunological barrier to xenotransplantation is hyperacute rejection, which is mediated by xenoreactive antibodies and complement, and results in rapid and irreversible tissue destruction. While endogenous complement regulatory proteins (CRPs) protect cells from injury caused by autologous complement, they are relatively species specific and most likely ineffectual in this setting. This has led to the hypothesis that expression of human CRPs in transgenic pigs may affect susceptibility to complement-mediated tissue injury in a porcine-to-human xenograft. Using specific lines of transgenic pigs that express low levels of human CD59, a CRP that acts at the terminal stage of the complement cascade, we present evidence that shows that the human CD59 protein inhibits membrane attack complex assembly and reduces tissue damage when the heart is transplanted to a baboon. Examination by immunohistochemistry of transgenic porcine hearts after transplantation revealed markedly reduced deposition of C5b and MAC, but a similar level of C3 deposition as compared with transplanted control hearts. This finding supports the concept that the species specific function of CRPs contributes to the humoral barrier to xenotransplantation and, given the low level of human CD59 protein expression in the porcine heart, argues that the human protein contributes a unique rather than an additive function in regulation of complement in a xenogeneic setting.

Animals↗
PubMed1996

Identification and characterization of a galactosyl peptide mimetic. Implications for use in removing xenoreactive anti-A Gal antibodies.

Gal alpha 1,3 Gal is thought to be the major antigenic epitope present on pig tissues to which XNAs bind. Removal of antibodies directed against that structure may be critical to the success of pig to human xeno-transplantation. As a first step toward the development of ligands capable of removing XNAs, we have used a phage-displayed peptide library to identify a six-amino-acid peptide that binds to the lectin GS-1-B4 (which binds the carbohydrate Gal alpha 1,3 Gal). This peptide blocks the binding of GS-1-B4 to pig aortic endothelial cells. The carbohydrate Gal alpha 1,3 Gal competes with the binding of GS-1-B4 to the peptide, suggesting that they may bind the same site. Using a RBC agglutination assay, we show that this peptide inhibits the agglutination of pig RBCs by heat-inactivated human serum at concentrations similar to that of Gal alpha 1,3 Gal.

Amino Acid Sequence↗
PubMed1995

Protection of xenogeneic cardiac endothelium from human complement by expression of CD59 or DAF in transgenic mice.

We investigated the ability of membrane-bound human complement regulatory proteins to control complement-driven humoral immune reactions on murine microvasculature. The human complement regulatory proteins CD59 and DAF were expressed using heterologous promoters in a variety of tissues in transgenic mice. Animals expressing these gene products are healthy and exhibit significant levels of endothelial cell expression of CD59 and DAF in cardiac muscle. Transgenic hearts perfused with human plasma exhibited profound reductions in the level of complement deposition compared with nontransgenic controls. We have also produced transgenic pigs that express these two human genes. Our results indicate that expression of complement regulatory proteins can control activation of complement and suggest that these proteins may have therapeutic applications in some inflammatory diseases and in the development of xenogeneic organs for human transplantation.

Animals↗
PubMed1995

In vivo transfer of GPI-linked complement restriction factors from erythrocytes to the endothelium.

Many proteins are associated with the outer layer of the cell membrane through a posttranslationally added glycosyl phosphatidylinositol (GPI) anchor. The functional significance of this type of protein linkage is unclear, although it results in increased lateral mobility, sorting to the apical surface of the cell, reinsertion into cell membranes, and possibly cell signaling. Here evidence is presented that GPI-linked proteins can undergo intermembrane transfer in vivo. GPI-linked proteins expressed on the surface of transgenic mouse red blood cells were transferred in a functional form to endothelial cells in vivo. This feature of GPI linkage may be potentially useful for the delivery of therapeutic proteins to vascular endothelium.

Animals↗
PubMed1995

Variation in the level of xenoantigen expression in porcine organs.

Hyperacute rejection of vascularized porcine to primate xenografts is initiated by the binding of xenoreactive natural antibodies to donor endothelium. We tested the hypothesis that the level of xenoantigen expression varies in the population of potential porcine donors and may determine the amount of binding of xenoreactive natural antibodies to a porcine organ perfused by xenogeneic blood. Two hundred ninety pigs were studied using an inhibition ELISA that quantitated the xenoantigen level on porcine platelets. Based on this assay, the levels of xenoantigen expression in the population adhered to a normal distribution. Kidneys from pigs found to express high antigen levels and kidneys from pigs found to express low antigen levels were perfused with baboon blood using an extracorporeal circuit. In multiple experiments, a significant difference was observed in the amount of xenoreactive natural antibody adsorbed by high antigen versus low antigen organs. Normalizing for the weight of the perfused organs and for levels of natural antibody in individual baboons, high antigen organs adsorbed 3.6 +/- 1.3 U of xenoreactive natural antibody/g and low antigen organs adsorbed -0.8 +/- 1.0 U of xenoreactive natural antibody/g (P < 0.002). Immunopathology of tissues from the perfused organs demonstrated more deposition of IgM and C4 in high than in low xenoantigen organs. The quantitative relationship between binding of xenoreactive natural antibodies to platelets and to whole organs suggests that platelets are a valid representation of endothelial cell antigen expression in vivo. Despite the probable importance of Gal alpha(1-3)Gal as an epitope recognized by xenoreactive natural antibodies, differences in the binding to platelets or to organs of the GS-I-B4 lectin that recognizes that sugar had no correlation with the differences in binding of IgM to these tissues. Variation in expression of xenoantigen may be exploited to selectively breed donors for xenotransplantation that are less susceptible to attack by xenoreactive natural antibodies.

Animals↗
PubMed1995

Transgenic expression of human complement regulatory proteins in mice results in diminished complement deposition during organ xenoperfusion.

Complement activation is an essential step in the hyperacute rejection of a vascularized xenograft. Endothelial cell-associated complement regulatory proteins limit complement activation in most settings, but are not able to limit the extensive complement activation that occurs in xenografts, at least in part due to their species specificity. To overcome this problem we and others have sought to express human complement regulatory proteins in the organs of potential donor animals. As an initial step toward evaluating this concept we tested organs from transgenic mice expressing human CD59 and/or decay-accelerating factor (DAF) in two in vitro perfusion systems for the ability to control activation of heterologous complement. In the first system, mouse hearts were perfused on a Langendorff circuit with 50% human plasma. Immunopathologic analysis of heart biopsies revealed deposition of human IgG, IgM, and C4 in both control and transgenic organs. The hearts from mice transgenic for human CD59 had substantially less and in some cases no membrane attack complex (MAC) and hearts from CD59/DAF transgenic mice had substantially less or no C5b and MAC. In the second system, mouse hearts were perfused with baboon blood through arterial lines inserted into baboons. Immunopathologic analysis of serial biopsies revealed the deposition of IgG, IgM, and C4 in control and transgenic hearts. Compared with controls, less MAC was deposited in many CD59-expressing hearts and less C5b and MAC in DAF-expressing hearts. These results demonstrate that human complement regulatory proteins expressed in a xenogeneic organ are able to contribute to the control of complement activation in that organ and support the concept that expression of these human molecules would help protect a xenogeneic organ transplanted into a human.

Animals↗
PubMed1995

Human CD59 expressed in transgenic mouse hearts inhibits the activation of complement.

Porcine-to-human xenotransplantation offers a potential solution to the critical shortage of human organs. The major immunological barrier to xenotransplantation between these species is a rapid rejection process mediated by preformed natural antibodies and complement. Xenogeneic organ grafts are especially susceptible to complement mediated injury because complement regulatory proteins, which ordinarily protect cells from inadvertent injury during the activation of complement, function poorly in regulating activation of heterologous complement. Removal of xenoreactive antibodies or systemic inhibition of complement activity has been shown to prolong graft survival. As an alternative to the systemic inhibition of complement activity, we have established a model system using transgenic animals to test whether the expression of human membrane bound complement regulatory proteins on mouse endothelial cells can inhibit the activation of human complement. CD59, which acts at the terminal stage of complement activation by inhibiting the formation of the membrane attack complex, was used as a paradigm for this model. A CD59 construct containing the putative CD59 gene promoter linked to the CD59 coding region was used to demonstrate expression of the human CD59 protein in various tissues of transgenic mice, including endothelial cells in the heart. In addition, we show that the transgenic CD59 protein is biologically active as determined by the ability to inhibit the formation of membrane attack complex in transgenic mouse hearts perfused ex vivo with human plasma. These results demonstrate that expression of membrane bound complement regulatory proteins can achieve complement inhibition in a xenogeneic organ and suggest that this approach may be useful for successful xenotransplantation between discordant species.

Animals↗
PubMed1995

Human complement regulatory proteins protect swine-to-primate cardiac xenografts from humoral injury.

The susceptibility of xenografts to hyperacute rejection is postulated to reflect in part failure of complement regulatory proteins (CRPs) to control activation of heterologous complement on graft endothelium. To test this concept, transgenic swine expressing the human CRP decay accelerating factor and CD59 were developed using a novel expression system involving transfer of the proteins from erythrocytes to endothelial cells. Hearts from transgenic swine transplanted into baboons had markedly less vascular injury and functioned for prolonged periods compared to hearts from nontransgenic swine. These results indicate that expression of human CRPs in xenogeneic organs may contribute to successful xenografting and suggest that intercellular protein transfer might be a useful approach for expression of heterologous proteins in endothelial cells.

Animals↗