Peripheral Artery Disease Causes More Harm to Patients than COVID-19.

Background: To optimize our strategic planning, we aimed to investigate the impact of the COVID-19 pandemic on the treatment of patients with peripheral artery disease (PAD) at our tertiary care hospital. Methods: We performed a retrospective single-center cohort study. In total, 1210 patients were included: 611 patients admitted between March and December 2020, compared to retrospective data from 599 patients from the same period in 2019. Results: Emergency admissions involving patients with advanced stage PAD increased significantly during the pandemic period of 2020, compared to the same period in 2019 (p < 0.0098). This increase was accompanied by increased limb amputations performed during the first lockdown, post-lockdown and the second lockdown in 2020, compared to respective time periods in 2019 (p < 0.0003, p < 0.0004, p = 1). No SARS-CoV-2 infection was observed among patients with PAD during the observation period. Conclusions: Strict lockdown protocols adversely affected the care of PAD patients, with persisting aftereffects, including increased emergency admission with unsuccessful revascularization attempts leading to limb amputation, even after the peak of the pandemic had passed. We believe that providing continuous care to PAD patients, even in times of global pandemics, will prevent the unfavorable outcomes observed during the COVID-19 pandemic in 2020.

Ex vivo fluorescence confocal microscopy: chances and changes in the analysis of breast tissue.

BACKGROUND: Rapid histologic diagnosis of frozen sections is essential for a variety of surgical procedures. Frozen sections however, require specialized lab equipment, are prone to freezing artifacts and are not applicable to all types of tissue. Adipose tissue is especially difficult to process in frozen sections. Although these limitations are well known, no alternative method for microscopic tissue analysis that might replace frozen sections could be established. Our objective was to evaluate whether tissue imaging based on ex vivo fluorescent confocal microscopy (FCM) is applicable for rapid microscopic assessment of breast tumors specimens with abundant adipose tissue. METHODS: We evaluated 17 tissue samples from mastectomy specimens, rich in adipose tissue, submitted to the department of pathology at the Medical University of Vienna. We conducted our study on the FCM VivaScope® 2500M-G4 (Mavig GmbH, Munich, Germany; Caliber I.D.; Rochester NY, USA). RESULTS: When comparing FCM to frozen sections, we found a very similar overall processing time for FCM images and frozen sections respectively. Image quality was mostly superior to frozen sections (especially for adipose tissue and nuclear detail) but inferior to H&E stained FFPE sections. Limitations of the technology were uneven coloring, invisibility of ink applied for marking tissue margins and distortion artifacts if too much pressure is applied to the tissue. CONCLUSION: FCM has the potential to expand the application and usefulness of rapid tissue analysis as speed is comparable and quality exceeds that of frozen sections especially in tissues rich in adipose cells such as breast specimen.

Left Renal Vein Division for Juxtarenal Aortic Exposure: Influence on Renal Function and Role of the Communicating Lumbar Vein.

BACKGROUND: In this study, we evaluate the outcome of renal function in patients undergoing juxtarenal abdominal aortic aneurysm repair with or without division of the left renal vein with special focus on the role of the communicating lumbar vein. METHODS: A retrospective analysis of prospectively collected data of 110 patients undergoing elective juxtarenal abdominal aortic aneurysm repair between 2000 and 2018 was performed. The demographic characteristics and comorbidities were reviewed in detail and the renal function was analysed pre- and post-operatively. The cohort of patients was split into group A (left renal vein divided) and B (left renal vein mobilised). Group A was further sub-analysed regarding the presence of a communicating lumbar vein on preoperative imaging data (group A+ = vein present, group A- = no communicating lumbar vein present). RESULTS: The patients were matched well regarding their demographic characteristics and comorbidities. In the analysis of renal function, no statistically significant difference could be detected between group A and B. In the sub-analysis of group A, the group with a communicating lumber vein (group A+) turned out to have a significantly better renal function in the long term (sCrea 0.87 vs. 1.51; p = 0.016). CONCLUSION: Ligation of the left renal vein is a safe procedure in surgery of juxtarenal aortic aneurysms regarding the outcome of the renal function. A communicating lumbar vein between the left renal vein and the left ascending lumbar vein seems to play a key role to provide venous drainage after division of the left renal vein.

Growth prediction model for abdominal aortic aneurysms.

BACKGROUND: The most relevant determinant in scheduling monitoring intervals for abdominal aortic aneurysms (AAAs) is maximum diameter. The aim of the study was to develop a statistical model that takes into account specific characteristics of AAA growth distributions such as between-patient variability as well as within-patient variability across time, and allows probabilistic statements to be made regarding expected AAA growth. METHODS: CT angiography (CTA) data from patients monitored at 6-month intervals with maximum AAA diameters at baseline between 30 and 66 mm were used to develop the model. By extending the model of geometric Brownian motion with a log-normal random effect, a stochastic growth model was developed. An additional set of ultrasound-based growth data was used for external validation. RESULTS: The study data included 363 CTAs from 87 patients, and the external validation set comprised 390 patients. Internal and external cross-validation showed that the stochastic growth model allowed accurate description of the distribution of aneurysm growth. Median relative growth within 1 year was 4.1 (5-95 per cent quantile 0.5-13.3) per cent. Model calculations further resulted in relative 1-year growth of 7.0 (1.0-16.4) per cent for patients with previously observed rapid 1-year growth of 10 per cent, and 2.6 (0.3-8.3) per cent for those with previously observed slow growth of 1 per cent. The probability of exceeding a threshold of 55 mm was calculated to be 1.78 per cent at most when adhering to the current RESCAN guidelines for rescreening intervals. An online calculator based on the fitted model was made available. CONCLUSION: The stochastic growth model was found to provide a reliable tool for predicting AAA growth.

The prognostic impact of vascular calcification on abdominal aortic aneurysm progression.

OBJECTIVE: The maximal aortic diameter is currently the only clinically applied predictor of abdominal aortic aneurysm (AAA) progression. It is known that the risk of rupture is associated with aneurysm size; hence, accurate monitoring of AAA expansion is crucial. Aneurysmal vessel wall calcification and its implication on AAA expansion are insufficiently explored. We evaluated the vascular calcification using longitudinal computed tomography angiographies (CTA) of patients with an AAA and its association with AAA growth. METHODS: We conducted a retrospective study of 102 patients with an AAA with a total of 389 abdominal CTAs at 6-month intervals, treated and followed at the Division of Vascular Surgery, Department of General Surgery, Medical University of Vienna. Digitally stored CTAs were reviewed for vascular calcification (volume and score) of the infrarenal aorta and common iliac arteries as well as for morphometric AAA analysis. In the prognostic setting, slow versus fast AAA progression was defined as a less than 2 mm or a 2-mm or greater increase in AAA diameter over 6 months. In addition, to analyze the association of vascular calcification and the AAA growth rate with longitudinal monitoring data, a specifically tailored log-linear mixed model was used. RESULTS: An inverse relation of increased abdominal vessel wall calcification and short-term AAA progression was detected. Compared with fast progressing AAA, the median calcification volume of the infrarenal aorta (1225.3 mm³ vs 519.8 mm³; P = .003), the median total calcification volume (2014.1 mm³ vs 1434.9 mm³; P = .008), and the median abdominal total customized Agatston calcium (cAC) score (1663.5 vs 718.4; P = .003) were significantly increased in slow progressing AAA. Importantly, a log-linear mixed model efficiently predicted AAA expansion based on current diameter and abdominal total cAC score (P = .042). CONCLUSIONS: We assessed the prognostic value of CTA-measured vascular calcification for AAA progression. Increased vascular calcification stabilizes the aortic aneurysmal wall and likely protects against progressive AAA expansion, resulting in a significant decrease of aneurysm growth over time. As a consequence, this may have implications for rupture risk, mortality, morbidity, and cost.

Long-term outcome in pediatric surgical bypass grafting after traumatic injury and tumor resection: retrospective cohort analysis.

Vascular bypass surgery in children differs significantly from adults. It is a rarely performed procedure in the setting of trauma and tumor surgery. Besides technical challenges to reconstruct the small and spastic vessels, another concern in bypass grafting is the adequate limb length growth over time. The primary aim of this study was to assess long-term outcome after pediatric bypass grafting, in a single academic center, focusing on potential effects on limb development. In this retrospective cohort analyses we included all pediatric patients undergoing vascular bypass grafting at our department between 2002 and 2017. All patients ≤ 18 years suffered a traumatic injury or underwent a tumor resection of the lower or upper limb. The youngest female patient was 0.4 years, the youngest male patient was 3.5 years. During the observation period, 33 pediatric patients underwent vascular repair, whereby 15 patients underwent bypass grafting. Median overall follow-up was 4.7 years (IQR ± 9). 8 patients (53%) had a traumatic injury (traumatic surgery group) and 7 patients had a planned orthopedic tumor resection (orthopedic surgery group). In 13/15 (87%) a great saphenous vein (GSV) graft and in 2/15 (13%) a Gore-Tex graft was used for bypassing. Both Gore-Tex grafts showed complete occlusion 12 and 16 years after implantation. No patient died in the early postoperative phase (< 30 days), however 3/7 (43%) in the orthopedic group died during follow-up. Revision surgery had to be performed in 1/15 (7%) patients. A functional use of the extremity was reported in all patients. Normal limb length growth according to the contralateral site, and therefore bypass growth, could be documented in 14/15 patients. Children are surgically challenging. In our study, surgery by a specialized vascular surgery team using GSV grafts led to adequate limb length and bypass growth, and we observed no functional restrictions.

Analysis of host Toll-like receptor 3 and RIG-I-like receptor gene expression in patients with abdominal aortic aneurysm.

OBJECTIVE: Abdominal aortic aneurysm (AAA) is a vascular disease relatively common in the elderly population. Although some events that contribute to the development and progression of AAA are known, there are limited data examining the association of Toll-like receptor 3 (TLR3) and RIG-I-like receptor expression with the pathogenesis of AAAs. In this study, we investigated the gene and protein expression of TLR3 and RIG-I-like receptors (RIG-I and MDA5) in aortic wall and blood of AAA patients and examined the relationship between their expression and immune response. METHODS: Total RNA was extracted from aortic wall tissues and blood samples collected from 20 patients with AAA and blood samples of 17 healthy volunteers without aortic aneurysm. To evaluate the DDX58 (RIG-I), IFIH1 (MDA5), and TLR3 gene expression level, quantitative real-time polymerase chain reaction was used. Extracellular cytokine and pattern recognition receptor levels were quantified by enzyme-linked immunosorbent assays. RESULTS: TLR3, RIG-I, and MDA5 were constitutively expressed in both aortic tissues and blood samples from AAA patients and healthy volunteers. In patients with AAA, higher TLR3 expression in aortic tissues than in blood was found (P = .004). The DDX58 messenger RNA expression was higher in blood of patients with AAA compared with healthy subjects (P = .021). A significantly higher level of plasma interleukin 4 was noticed in patients with AAA than in healthy individuals (P = .008). CONCLUSIONS: This study suggests that RIG-I and TLR3 seem to be important factors in the pathogenesis of AAA.

Dabigatran: patient management in specific clinical settings.

Dabigatran, a direct thrombin inhibitor, is licensed for the prevention of venous thromboembolism after knee and hip replacement, the prevention of stroke and systemic embolism in patients with non-valvular atrial fibrillation and for the treatment of acute venous thromboembolism. As dabigatran has a favourable benefit-risk profile, it is being increasingly used. Dabigatran differs from vitamin K antagonists as regards its pharmacological characteristics and its impact on certain laboratory tests, and also in the lack of a direct antagonist that can reverse dabigatran-induced anticoagulation. In emergency settings such as acute bleeding, emergency surgery, acute coronary syndrome, thrombolysis for ischaemic stroke or overdosing, specific strategies are required. A working group of experts from various disciplines has developed strategies for the management of dabigatran-treated patients in emergency settings.

Echinococcus canadensis G7 (pig strain): an underestimated cause of cystic echinococcosis in Austria.

Anamnesis data of 104 patients with Cystic Echinococcosis were correlated retrospectively with the detected species/strain of Echinococcus. Ninety-two percent (N = 23) of autochthonous Austrian and 33% (N = 9) of patients with former Yugoslavian (YU) origin were infected with E. canadensis G7, the pig strain. All patients originating from Turkey harbored E. granulosus G1, the sheep strain. All E. canadensis G7-infected patients showed small liver cysts (ø 5.9 cm), only one of them an additional lung cyst. The median age at the time of operation of the Austrian patients was 55 years, of the Turkish patients 30 years, and of the former YU patients 23 years in the E. canadensis and 42 years in the E. granulosus-infected patients, respectively. The unexpected high number of E. canadensis G7-infected patients and the immigrants' young age show the importance of E. canadensis as a cause of human Cystic Echinococcosis in Central Europe and accordingly this new species has to be included into future echinococcosis control programs.

Development of a new PCR protocol for the detection of species and genotypes (strains) of Echinococcus in formalin-fixed, paraffin-embedded tissues.

The aim of our study was to establish a new PCR protocol for the detection and discrimination of Echinococcus granulosus complex on one hand and Echinococcus multilocularis in formalin-fixed, paraffin-embedded tissues (FFPTs) on the other. The target sequences for all PCRs are located on a 471bp segment of the mitochondrial ND1 gene, the fragment sizes of the amplification products are 295bp (for the sheep strain of E. granulosus), 204bp (for the pig strain of E. granulosus) and 252bp (for E. multilocularis), respectively. In total, 80 FFPTs from patients with histologically confirmed echinococcosis (76 with E. granulosus and four with E. multilocularis) operated on in Austrian hospitals between 1978 and 2005 were examined. In 68 (85%) samples, we were able to detect specific DNA fragments with our newly established PCR protocols. Thirty-eight (47.5%) of 80 clinical samples were identified as the G1 strain, 26 (32.5%) as the G5, 6 or 7 strains and four (5%) as E. multilocularis. The specificity of all three PCRs was 100%; for the discrimination between G6 and G7 strains, sequencing of an additional 234bp PCR fragment was necessary and showed that three out of 26 G5, 6 or 7 PCR-positive patients were infected with E. granulosus genotype G6 (the camel strain).

Immunological unresponsiveness in chimeric miniature swine following MHC-mismatched spleen transplantation.

BACKGROUND: In rodents, spleen allotransplantation (SpTx) induces tolerance. We investigated the induction of chimerism and donor-specific unresponsiveness following pig SpTx. METHODS: Thirteen pigs underwent splenectomy (day 0); all received a blood transfusion. In 11/13 pigs, SpTx was performed across a MHC class I (n=1) or full (n=10) barrier; two control pigs received no SpTx. All pigs were monitored for chimerism, and anti-donor immune responses, including suppressor assays. Four pigs (two asplenic controls and two with SpTx) underwent delayed donor-matched kidney transplantation without immunosuppression. RESULTS: Six of the 11 spleen grafts were lost from rejection (n=5) or splenic vein thrombosis (n=1), and five remained viable. All 11 SpTx recipients developed multilineage chimerism, but chimerism was rapidly lost if the graft failed. Two control pigs showed <6% blood chimerism for 4 and 11 days only. Pigs with functioning spleen grafts had multilineage chimerism in blood, thymus and bone marrow for at least 2-6 months, without graft-versus-host disease. These pigs developed in vitro donor-specific hyporesponsiveness and suppression. In 2 pigs tolerant to the spleen graft, donor MHC-matched kidney grafts survived for >4 and >7 months in the absence of exogenous immunosuppression; in two asplenic pigs, kidney grafts were rejected on days 4 and 15. CONCLUSIONS: Successful SpTx can result in hematopoietic cell engraftment and in vitro donor-specific unresponsiveness, enabling prolonged survival of subsequent donor-matched kidney grafts without immunosuppression.

Does additional doxorubicin chemotherapy improve outcome in patients with hepatocellular carcinoma treated by liver transplantation?

The aim of this prospective randomized study was to determine whether additional doxorubicin chemotherapy improves outcome in patients with hepatocellular carcinoma (HCCA) treated by liver transplantation. Stratification parameters were tumor stage (UICC I-IVa), gender, age 50 years, alpha-fetoprotein 20 ng/mL, cirrhosis and HbsAg status. For pre-operative chemotherapy doxorubicin (15 mg/m2) was given biweekly, intra-operative chemotherapy was a single dose administered before surgical manipulation. Post-operative chemotherapy from day 10 was as given preoperatively for a total dosage of 300 mg/m2. Outcome parameters were overall survival (OS) and disease-free survival. Of the 75 consecutive patients who received liver transplantation for treatment of HCCA, 62 patients were enrolled. Thirty-four patients were randomized in the chemotherapy group; 28 patients were in the control group and transplanted only. OS rates at 5 years were 38% in the chemotherapy group and 40% in the control group, disease-free survival rates at 5 years 43% and 53%, respectively. Tumor stage and vascular invasion were identified as independent risk factors for recurrence of disease. Doxorubicin chemotherapy did not improve organ survival and disease-free survival in patients undergoing liver transplantation for HCCA.

Histopathology of spleen allograft rejection in miniature swine.

Spleen transplantation (SpTx) has established donor-specific tolerance in rodents, but not in large animals or humans. We report the histopathology of rejection in an established model of SpTx in major histocompatibility complex (MHC)-defined miniature swine. Of the 17 SpTx, rejection was observed in two grafts transplanted into untreated, MHC-matched, minor antigen-disparate recipients (group 1, n=4), but not in the two that received a 12-day course of cyclosporin A (CyA). Rejection also occurred in five grafts transplanted into fully MHC-disparate recipients (group 2, n=12), one of which was untreated and four of which received some form of immunosuppressive therapy. One recipient of an MHC class-I-mismatched spleen treated with 12 days of CyA did not show rejection. Following biopsy and/or necropsy, fixed allograft tissue sections were treated with multiple stains, immunohistochemical markers and TUNEL assay. Common features of rejection occurred in grafts from both groups, but with varying time courses. Necrosis developed as early as day 8 in group 2 and day 27 in group 1, ranging from focal fibrinoid necrosis of arteriolar walls and sinusoids to diffuse liquefactive necrosis, usually associated with haemorrhage. Other features of rejection included white pulp expansion by atypical cells and decreased staining of basement membranes and reticular fibres. A doubling of the baseline TUNEL index preceded histologically identifiable rejection. This study establishes histologic guidelines for diagnosing and, perhaps, in future studies, predicting acute rejection of splenic allografts transplanted across known histocompatibility barriers in a large-animal model.

Early weaning of piglets fails to exclude porcine lymphotropic herpesvirus.

BACKGROUND: Xenotransplantation using pigs as source species carries a risk for the activation of latent herpesviruses from the porcine donor and potential transmission to the recipient. In pig-to-baboon xenotransplantation, activation of porcine cytomegalovirus (PCMV) has been associated with xenograft injury and an increased incidence of consumptive coagulopathy and graft loss. Activation of porcine lymphotropic herpesvirus (PLHV)-1 was not observed in pig-to-baboon solid organ xenotransplantation, but was associated with a syndrome of post-transplantation lymphoproliferative disorder (PTLD) after allogeneic stem cell transplantation in pigs. MATERIAL AND METHODS: Early weaning of piglets was used to try to reduce the viral burden of xenograft donors. This consisted of separating the piglets of a litter from the sow within the first 2 weeks after birth and raising them in isolation from the remaining herd. RESULTS: We have previously demonstrated that PCMV could be excluded from source animals by early weaning of piglets. However, early weaning failed to exclude PLHV-1 from source pigs. CONCLUSIONS: This disparity between PCMV and PLHV-1 reflects differing pathogenesis of infection of these herpesviruses. New approaches will be needed to exclude PLHV-1 from pig colonies.

Reduction of consumptive coagulopathy using porcine cytomegalovirus-free cardiac porcine grafts in pig-to-primate xenotransplantation.

BACKGROUND: Xenotransplantation using pigs as the source species for organs carries a potential risk for transmission and activation of porcine herpesviruses. Activation of porcine cytomegalovirus (PCMV) in pig-to-baboon xenotransplantation is associated with xenograft injury and possibly an increased incidence of consumptive coagulopathy (CC). METHODS: To further investigate the role of PCMV activation in the occurrence of CC, a strategy to exclude PCMV from the donor was developed. To exclude PCMV, piglets were early-weaned and raised separated from other swine. These piglets were used as donors in an experimental protocol of pig-to-baboon heart xenotransplantation. RESULTS: Early weaning of piglets was successful in excluding PCMV. Use of PCMV-free cardiac porcine xenografts in baboons resulted in prolonged graft survival and prevented consumptive coagulopathy in all recipients. CONCLUSIONS: The use of PCMV-free cardiac grafts is beneficial in reducing the direct effects of PCMV activation in the graft (tissue damage) and the indirect effects of PCMV activation in the recipient (consumptive coagulopathy).

Thrombotic microangiopathy and graft arteriopathy in pig hearts following transplantation into baboons.

BACKGROUND: Acute humoral xenograft rejection (AHXR) is an immunologic barrier in pig-to-baboon organ transplantation (Tx). We report microvascular thrombosis and myocardial necrosis in a series of cardiac xenografts. METHODS: Ten baboons underwent heterotopic heart Tx from pigs transgenic for human decay-accelerating factor. Recipients were treated with soluble Gal glycoconjugates and multiple immunosuppressive agents. Grafts were removed when palpable contractions stopped. Stained tissue sections from harvested grafts were analyzed by light and fluorescence microscopy. RESULTS: Xenograft survival ranged from 4 to 139 (mean 37, median 27) days. Some histology was typical for AHXR (n = 4; median survival 22 days). Hemorrhage and edema were only focal in the longer-surviving grafts (n = 4, median survival 54 days). All grafts had multiple platelet-rich fibrin thrombi occluding myocardial vessels. Ischemic damage was manifested by contraction band necrosis in four grafts, myocytolysis in eight, coagulative necrosis in nine, and patchy myocyte dropout in all grafts. A notable paucity of interstitial mononuclear cells was observed in all grafts. Marked intimal thickening resembling that of allograft vasculopathy was observed in one graft. Immunofluorescence showed immunoglobulin (Ig)G and/or IgM deposition in five grafts. Multivessel C4d deposition appeared in seven grafts. Significant C3 deposition was absent. CONCLUSIONS: Cardiac xenograft survival in the pig-to-baboon model can be significantly prolonged by vigorous immunosuppressive treatment of recipient animals. Additional efforts to block humoral activation of graft endothelial cells and/or to overcome species-specific molecular coagulation pathway incompatibilities may prevent the development of microvascular thrombosis and myocardial infarction. Cardiac xenograft vasculopathy (chronic rejection) can occur with prolonged graft survival.

Acute vascular rejection of xenografts: roles of natural and elicited xenoreactive antibodies in activation of vascular endothelial cells and induction of procoagulant activity.

BACKGROUND: Hyperacute rejection of vascularized discordant xenografts can now be effectively managed. However, acute vascular rejection (AVR) then ensues, resulting in graft destruction, coagulopathy, or both within weeks. The aim of this study was to determine associations between humoral responses to the xenograft and the induction of AVR, coagulopathy, or both. METHODS: In vitro, heat-inactivated, naive or sensitized baboon sera containing xenoreactive natural or elicited antibodies were used to activate porcine aortic endothelial cells (PAEC) in vitro. Tissue factor expression on PAEC was determined as an index of heightened procoagulant activity. In vivo, porcine renal xenografts were transplanted into immunosuppressed baboons, and at the time of rejection or the development of a consumptive coagulopathy, biopsy specimens were obtained for studies of xenoreactive antibody binding and tissue factor expression. RESULTS: In vitro, incubation of PAEC with naive baboon sera containing natural anti-Galalpha1,3Gal (Gal) antibodies resulted in minimal tissue factor induction; the addition of complement boosted procoagulant responses. Elicited xenoreactive antibodies, and to non-Gal epitopes alone, induced high amounts of procoagulant activity on PAEC; the addition of complement resulted in overt cytotoxicity. In vivo, AVR was associated with xenoreactive antibody deposition in the graft. When vascular endothelial binding of xenoreactive antibody was combined with the expression of tissue factor, consumptive coagulopathy developed irrespective of histopathologic features of AVR. CONCLUSIONS: Our in vitro results indicate that elicited antibodies, potentially to non-Gal epitopes, induce endothelial cell activation and tissue factor expression; in vivo, a consumptive coagulopathy occurred when there was xenoreactive antibody deposition and increase of tissue factor.

Activation of porcine cytomegalovirus, but not porcine lymphotropic herpesvirus, in pig-to-baboon xenotransplantation.

Tissue-invasive disease due to porcine cytomegalovirus (PCMV) has been demonstrated after pig-to-baboon solid-organ xenotransplantation. Porcine lymphotropic herpesvirus (PLHV)-1 is associated with B cell proliferation and posttransplant lymphoproliferative disorder after allogeneic bone marrow transplantation in swine but has not been observed in pig-to-primate xenotransplantation. Activation of PCMV and PLHV-1 was investigated in 22 pig-to-baboon xenotransplants by use of quantitative polymerase chain reaction. PCMV was found in all xenografts; increased viral replication occurred in 68% of xenografts during immunosuppression. PLHV-1 was found in 12 xenografts (55%); no increases in viral replication occurred during immunosuppression. Control immunosuppressed swine coinfected with PCMV and PLHV-1 had activation of PCMV but not PLHV-1. PCMV, but not PLHV-1, is activated in solid-organ xenotransplantation.

Suppression of natural and elicited antibodies in pig-to-baboon heart transplantation using a human anti-human CD154 mAb-based regimen.

Natural and elicited antipig antibodies (Abs) lead to acute humoral xenograft rejection (AHXR). Ten baboons underwent heterotopic heart transplantation (Tx) from human decay-accelerating factor (hDAF) pigs. Depletion of anti-Galalpha1, 3Gal (Gal) Abs was achieved by the infusion of a Gal glycoconjugate from day-1. Immunosuppression included induction of antithymocyte globulin, thymic irradiation, and cobra venom factor, and maintenance with a human antihuman CD154 mAb, mycophenolate mofetil, and methylprednisolone; heparin and prophylactic ganciclovir were also administered. Pig heart survival ranged from 4 to 139 (mean 37, median 27) days, with three functioning for >50 days. Graft failure (n = 8) was from classical AHXR [4], thrombotic microangiopathy [3], or intragraft thrombosis [1], with death (n = 2) from pneumonia [1], or possible drug toxicity (with features of thrombotic microangiopathy) [1]. Anti-Gal Abs (in microg/mL) were depleted by Gal glycoconjugate before graft implantation from means of 41.3 to 6.3 (IgM) and 12.4-4.6 (IgG), respectively, and at graft excision were 6.3 and 1.7 microg/mL, respectively. No elicited Abs developed, and no cellular infiltration was seen. The treatment regimen was effective in maintaining low anti-Gal Ab levels and in delaying or preventing AHXR. The combination of costimulatory blockade and heparin with Tx of a Gal-negative pig organ may prolong graft survival further.