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Biomedical subjects

K R McCurry

Publications and source records attributed to K R McCurry.

At least 19 recordsLinked to original sources
PubMed2001

A multicenter, randomized, controlled trial of Celsior for flush and hypothermic storage of cardiac allografts.

BACKGROUND: A multicenter, randomized, controlled, open-label trial was conducted to evaluate the safety and efficacy of Celsior when used for flush and hypothermic storage of donor hearts before transplantation. METHODS: Heart transplant recipients were randomized to one of two treatment groups in which donor hearts were flushed and stored in either Celsior or conventional preservation solution(s) (control). Study subjects were followed for 30 days after transplantation. RESULTS: A total of 131 heart transplant recipients were enrolled (Celsior, n = 64; control, n = 67). The treatment groups were evenly distributed in donor and recipient base line characteristics. Graft loss rate was lower in the Celsior group on day 7 (3% versus 9%) and on day 30 (6% versus 13%), but the difference was not statistically significant based on 95% confidence interval analysis. No significant difference was measured between the Celsior and control groups in 7-day patient survival (97% versus 94%) and the proportion of patients with one or more adverse events (Celsior, 88%; control 87%) or serious adverse events (Celsior, 38%; control, 46%). Significantly fewer patients in the Celsior group developed at least one cardiac-related serious adverse event (13% versus 25%). CONCLUSIONS: Celsior was demonstrated to be as safe and effective as conventional solutions for flush and cold storage of cardiac allografts before transplantation.

Adult↗
PubMed2001

Relapsing bacteremia in patients with ventricular assist device: an emergent complication of extended circulatory support.

BACKGROUND: Ventricular assist devices (VAD) are currently approved for use as a bridge for transplantation. Although reports have suggested acceptable rates of survival of patients with VAD, there is little information regarding the mechanism and etiology of bacteremia in these patients. METHODS: We prospectively followed patients who underwent VAD implantation and developed bacteremia during VAD support at the University of Pittsburgh Medical Center. Relapsing bacteremia was defined as at least two episodes of positive blood cultures with a genetically related organism on 2 different days. Species identification and susceptibility testing were performed on all isolates. Pulse field gel electrophoresis was performed on selected blood and VAD isolates. RESULTS: Between January 1998 and August 1999, 3 patients with VAD developed relapsing bacteremia, which was treated with full courses of antibiotic agents, 2 of whom also developed VAD endocarditis. All 3 patients had documented driveline or device pocket infections with these isolates. Consecutive blood and VAD isolates were found to be genetically related within each patient. CONCLUSIONS: These patients with bacteremia after VAD implantation had relapse due to the same strain, which may have originated from indolent driveline infection. Endovascular infection in this setting is difficult to eradicate with antibiotic agents and carries a high mortality. These patients should be considered to have priority for orthotopic heart transplantation.

Adult↗
PubMed2000

Effects of donor bone marrow infusion in clinical lung transplantation.

BACKGROUND: We have demonstrated that donor cell chimerism is associated with a lower incidence of obliterative bronchiolitis (OB) in lung recipients, and that donor chimerism is augmented by the infusion of donor bone marrow (BM). We herein report the intermediate results of a trial combining the infusion of donor BM and lung transplantation. METHODS: Clinical and in vitro data of 26 lung recipients receiving concurrent infusion of donor bone marrow (3.0 to 6.0 x 10(8) cells/kg) were compared with those of 13 patients receiving lung transplant alone. RESULTS: Patient survival and freedom from acute rejection were similar between groups. Of the patients whose graft survived greater than 4 months, 5% (1 of 22) of BM and 33% (4 of 12) of control patients, developed histologic evidence of OB (p = 0.04). A higher proportion (but not statistically significant) of BM recipients (7 of 10, 70%) exhibited donor-specific hyporeactivity by mixed lymphocyte reaction assays as compared with the controls (2 of 7, 28%). CONCLUSIONS: Infusion of donor BM at the time of lung transplantation is safe, and is associated with recipients' immune modulation and a lower rate of obliterative bronchiolitis.

Adult↗
PubMed2000

A clinical trial combining donor bone marrow infusion and heart transplantation: intermediate-term results.

BACKGROUND: Donor chimerism (the presence of donor cells of bone marrow origin) is present for years after transplantation in recipients of solid organs. In lung recipients, chimerism is associated with a lower incidence of chronic rejection. To augment donor chimerism with the aim to enhance graft acceptance and to reduce immunosuppression, we initiated a trial combining infusion of donor bone marrow with heart transplantation. Reported herein are the intermediate-term results of this ongoing trial. METHODS: Between September 1993 and August 1998, 28 patients received concurrent heart transplantation and infusion of donor bone marrow at 3.0 x 10(8) cells/kg (study group). Twenty-four contemporaneous heart recipients who did not receive bone marrow served as controls. All patients received an immunosuppressive regimen consisting of tacrolimus and steroids. RESULTS: Patient survival was similar between the study and control groups (86% and 87% at 3 years, respectively). However, the proportion of patients free from grade 3A rejection was higher in the study group (64% at 6 months) than in the control group (40%; P =.03). The prevalence of coronary artery disease was similar between the two groups (freedom from disease at 3 years was 78% in study patients and 69% in controls). Similar proportions of study (18%) and control (15%) patients exhibited in vitro evidence of donor-specific hyporesponsiveness. CONCLUSIONS: The infusion of donor bone marrow reduces the rate of acute rejection in heart recipients. Donor bone marrow may play an important role in strategies aiming to enhance the graft acceptance.

Acute Disease↗
PubMed2000

In the lung aerosol cyclosporine provides a regional concentration advantage over intramuscular cyclosporine.

BACKGROUND: Acute rejection remains an almost universal complication among lung transplant recipients. Refractory rejection as well as chronic systemic immunosuppression is associated with significant morbidity and mortality. Recent studies suggest that aerosol cyclosporine may address these issues by effectively preventing acute cellular rejection while maintaining low systemic drug concentrations. This study was designed to evaluate the concentrations of cyclosporine in blood and lung tissue after aerosol and intramuscular administration. METHODS: Lewis rats were divided into 4 experimental groups: Groups A (n = 33) and B (n = 30) received aerosol cyclosporine 3 and 5 mg/kg, respectively; Groups C (n = 33) and D (n = 30) received systemic cyclosporine 5 and 15 mg/kg, respectively. We used high-performance liquid chromatography to quantitate blood and lung tissue cyclosporine levels at timed intervals. We used the trapezoidal rule to approximate area under the concentration vs time curve (AUC). RESULTS: Aerosol delivery of cyclosporine resulted in higher and more rapid peak drug levels in lung tissue samples than did systemic delivery. At an equivalent 5 mg/kg dose, the cyclosporine AUC was 3 times higher with aerosol delivery than with intramuscular delivery in lung tissue (477,965 vs 157,706 ng x hour/g, respectively). The lung tissue: blood AUC ratio was highest in the aerosol groups (27.3:1 and 17.4:1) compared with the intramuscular groups (8.1:1 and 9.4:1). CONCLUSION: Local aerosol inhalation delivery of cyclosporine provides a regional advantage over systemic intramuscular therapy by providing higher peak concentrations and greater lung tissue exposure.

Administration, Inhalation↗
PubMed1999

Effect of ischemic time on survival in clinical lung transplantation.

BACKGROUND: While there is convincing evidence that prolonged ischemic times correlate with reduced long-term survival in heart transplantation, the effect of ischemic time on outcome in clinical lung transplantation remains controversial. To assess the effect of ischemic time on outcomes in lung transplantation, we reviewed our experience. METHODS: The study was performed by retrospective chart review. RESULTS: First-time lung transplantation was performed on 392 patients between 1988 and 1998. All grafts were flushed with cold crystalloid preservation solution and stored on ice. Ischemic time data were available for 352 of 392 (90%) patients. Ischemic times were grouped as follows: 0 to 4 hours (n = 91), 4 to 6 hours (n = 201), more than 6 hours (n = 60). Ischemic time did not correlate with survival: 3-year actuarial survival = 56% (0 to 4 hours), 58% (4 to 6 hours), 68% (> 6 hours), p = 0.58. There was no significant difference in the incidence of biopsy-proven diffuse alveolar damage in the first 30 days after transplantation (31%, 32%, 38%), episodes of acute rejection in the first 100 days after transplantation (1.9, 1.8, 1.7), duration of intubation (median 3, 4, 3 days), or incidence of obliterative bronchiolitis (23%, 28%, 26%) between the three groups (0 to 4 hours, 4 to 6 hours, > 6 hours, respectively). A diagnosis of diffuse alveolar damage was associated with a significantly worse outcome (1-year survival = 82% versus 54%, p < 0.0001). CONCLUSIONS: In contrast to heart transplantation, pulmonary allograft ischemic time up to 9 hours does not appear to have a significant impact on early graft function or survival. The presence of diffuse alveolar damage on biopsy early after transplantation does not correlate with prolonged ischemic time, but is associated with substantially reduced posttransplantation survival.

Adolescent↗
PubMed1998

Controlling perioperative morbidity and mortality after lung transplantation for pulmonary hypertension.

Lung transplantation for pulmonary hypertension now accounts for more than 18% of all transplantations performed with 1-year survival rates for primary pulmonary hypertension approximating 65%. Patients have NYHA class III or IV symptoms and typically have marked right ventricular dysfunction. Accelerated or acute decompensation can occur. A decline in status leads to a patient with severe right heart failure, hepatic dysfunction and severe malnutrition, conditions that increase perioperative morbidity and mortality. Immediate right ventricular dysfunction may be related to allograft injury with persistent elevation of pulmonary artery pressures or to intrinsic right ventricular disease; this can be supported with inotropic medications. Single-lung transplantation results in postoperative physiology that can require aggressive therapy to limit mortality. When allograft dysfunction occurs, significant hypoxemia results to a greater degree than that observed with single-lung transplantations for other diseases or following double-lung transplantation. As a result, careful donor selection for a single lung transplantation is crucial. The most common reason for prolonged ventilation is allograft reperfusion injury with ventilation-perfusion mismatching. Neuromuscular blockade can decrease oxygen utilization and improve chest wall compliance, whereas lateral positioning with the native lung down can be crucial to improving V/Q matching. Differential lung ventilation allows the application of larger quantities of positive end-expiratory pressure to the injured allograft. The use of exogenous nitrates has been advocated to reduce pulmonary vascular resistance. Nitric oxide has attractive potential benefits because it can be delivered directly to the lungs and functions to dilate the pulmonary vascular bed. All else having failed, we and others have successfully used extracorporeal membrane oxygenation to support cardiopulmonary function.

Humans↗
PubMed1997

Transgenic pigs expressing human CD59 and decay-accelerating factor produce an intrinsic barrier to complement-mediated damage.

We characterize a line of transgenic pigs that express the human complement-regulatory proteins human CD59 and human decay-accelerating factor. These genes, under the control of heterologous promoters, are expressed in a variety of organs, including the vasculature of the heart, kidney, and liver. We demonstrate that moderate levels of these gene products are sufficient to protect peripheral blood cells from human or baboon complement. Using pig to baboon heterotopic heart transplants, we show that expression of these proteins is sufficient to block the complement-mediated damage that is the hallmark of such xenografts, when nontransgenic organs are used. These results indicate that there is significant species specificity of intrinsic complement regulatory protein function. This specificity is evident in transgenic organs in which low levels of human CD59 and human decay-accelerating factor expression significantly effect the humoral immune response that causes xenograft rejection. This result suggests that transgenic organs with high levels of human complement-regulatory protein expression will be sufficient to alleviate the humoral immunological barriers that currently block the use of xenogeneic organs for human transplantation.

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

Lung and heart-lung transplantation at the University of Pittsburgh.

The application of lung transplantation as a treatment modality for patients with severe pulmonary disease has changed dramatically since its inception. At the University of Pittsburgh, the criteria for recipient selection continues to evolve and, in an effort to maximize scarce donor organs, the criteria for donor lung acceptance have been extended. Patient survival during the first 3 years after transplantation continues to improve but longer term survival is limited by infectious complications and chronic rejection. In early studies, the utilization of cyclosporine delivered directly to the lungs via aerosol has resulted in dramatic improvement in pulmonary function in recipients with immune mediated allograft injury and has allowed a reduction in systemic immunosuppression. We are hopeful that interventions such as this will result in prolongation of patient survival with less toxicity.

Actuarial Analysis↗
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↗
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

Cardiac xenografts between primate species provide evidence for the importance of the alpha-galactosyl determinant in hyperacute rejection.

Transplants performed between phylogenetically disparate species are subject to hyperacute rejection initiated by binding of xenoreactive natural Abs to endothelium in the donor organ. Binding of these Abs activates complement, leading to tissue injury and destruction of the graft. Human xenoreactive natural Abs recognize Gal alpha 1-3Gal beta 1-4GlcNAc (galactose alpha 1-3galactose beta 1-4-N-acetylglucosame); however, the relative importance of this Ag in graft rejection has not been proved. The present study was conducted to test the potential importance of alpha-galactosyl (alpha-Gal) determinants in the pathogenesis of hyperacute rejection. To this end, hearts (n = 3) from New World monkeys (Saimiri scureus, squirrel monkey), which can synthesize Gal alpha 1-3Gal, were transplanted heterotopically into Old World monkeys (Papio species, baboon), which do not synthesize Gal alpha 1-3Gal determinants and which have circulating anti-alpha Gal Abs. The xenografts were rejected in 51 to 56 min (mean +/- SD = 53.3 +/- 2.5), results similar to those observed in porcine grafts transplanted into baboons. Histologic analysis of the hearts revealed thrombosis and intraparenchymal hemorrhage and immune deposits consisting of IgM, Clq, C3, C4, C5b, and the membrane attack complex, but not properdin or factor B of the recipient deposited on graft endothelium. Sera obtained from baboons after perfusion of squirrel monkey kidneys revealed depletion of alpha-Gal-specific Abs and anti-pig endothelial cell Abs. These findings provide strong evidence that the Abs that accumulate in New World monkey organs during perfusion with baboon blood are the same Abs that would accumulate in a porcine organ transplanted into a primate and suggest that hyperacute rejection is not necessarily a reflection of phylogenetic distance but that the expression of terminal alpha-Gal residues provides an adequate target to initiate that process.

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↗