Examining epitope mutagenesis as a strategy to reduce and eliminate human antibody binding to class II swine leukocyte antigens.

Xenotransplantation of pig organs into people may help alleviate the critical shortage of donors which faces organ transplantation. Unfortunately, human antibodies vigorously attack pig tissues preventing the clinical application of xenotransplantation. The swine leukocyte antigens (SLA), homologs of human HLA molecules, can be xenoantigens. SLA molecules, encoded by genes in the pig major histocompatibility complex, contribute to protective immune responses in pig. Therefore, simply inactivating them through genome engineering could reduce the ability of the human immune system to surveil transplanted pig organs for infectious disease or the development of neoplasms. A potential solution to this problem is to identify and modify epitopes in SLA proteins to eliminate their contribution to humoral xenoantigenicity while retaining their biosynthetic competence and ability to contribute to protective immunity. We previously showed that class II SLA proteins were recognized as xenoantigens and mutating arginine at position 55 to proline, in an SLA-DQ beta chain, could reduce human antibody binding. Here, we extend these observations by creating several additional point mutants at position 55. Using a panel of monoclonal antibodies specific for class II SLA proteins, we show that these mutants remain biosynthetically competent. Examining antibody binding to these variants shows that point mutagenesis can reduce, eliminate, or increase antibody binding to class II SLA proteins. Individual mutations can have opposite effects on antibody binding when comparing samples from different people. We also performed a preliminary analysis of creating point mutants near to position 55 to demonstrate that manipulating additional residues also affects antibody reactivity.

Role of Stereotactic Body Radiation Therapy Before Orthotopic Liver Transplantation: Retrospective Evaluation of Pathologic Response and Outcomes.

PURPOSE: To analyze the results of stereotactic body radiation therapy (SBRT) in patients with early-stage, localized hepatocellular carcinoma who underwent definitive orthotopic liver transplantation (OLT). METHODS AND MATERIALS: The subjects of this retrospective report are 38 patients diagnosed with hepatocellular carcinoma who underwent SBRT per institutional phase 1 to 2 eligibility criteria, before definitive OLT. Pre-OLT radiographs were compared with pathologic gold standard. Analysis of treatment failures and deaths was undertaken. RESULTS: With median follow-up of 4.8 years from OLT, 9 of 38 patients (24%) recurred, whereas 10 of 38 patients (26%) died. Kaplan-Meier estimates of 3-year overall survival and disease-free survival are 77% and 74%, respectively. Sum longest dimension of tumors was significantly associated with disease-free survival (hazard ratio 1.93, P=.026). Pathologic response rate (complete plus partial response) was 68%. Radiographic scoring criteria performed poorly; modified Response Evaluation Criteria in Solid Tumors produced highest concordance (κ = 0.224). Explants revealed viable tumor in 74% of evaluable patients. Treatment failures had statistically larger sum longest dimension of tumors (4.0 cm vs 2.8 cm, P=.014) and non-statistically significant higher rates of lymphovascular space invasion (44% vs 17%), cT2 disease (44% vs 21%), ≥pT2 disease (67% vs 34%), multifocal tumors at time of SBRT (44% vs 21%), and less robust mean α-fetoprotein response (-25 IU/mL vs -162 IU/mL). CONCLUSIONS: Stereotactic body radiation therapy before to OLT is a well-tolerated treatment providing 68% pathologic response, though 74% of explants ultimately contained viable tumor. Radiographic response criteria poorly approximate pathology. Our data suggest further stratification of patients according to initial disease burden and treatment response.

Optimization of Perioperative Conditions to Prevent Ischemic Cholangiopathy in Donation After Circulatory Death Donor Liver Transplantation.

BACKGROUND: Donation after circulatory death (DCD) donor pool remains underutilized for liver transplantation (LT). We describe optimizing "modifiable risk factors," such as cold ischemia time (CIT) recipient warm ischemia time (WIT) and the use of thrombolytic flush at the time of procurement to minimize ischemic cholangiopathy (IC). METHODS: From July 2011 (era II), to improve outcomes after DCD LT, measures were taken to minimize CIT, operative time and recipient WIT along with the use of tissue plasminogen activator (tPA) flush during DCD procurements. Thirty consecutive DCD LTs were performed prospectively in era II. Outcomes were compared with 61 historic controls (era I). Reperfusion biopsies were evaluated for the presence of necrosis and biliary epithelial damage. RESULTS: Median CIT (4.9 [3.5-5.9] vs 6.4 [4.3-12]; P < 0.001), hepatectomy time (70 [42-120] vs 81 [58-207]; P = 0.02), and recipient WIT (16 [13-31] vs 24[15-40]; P < 0.001) were significantly shorter in era II. All patients in era II received tPA flushed liver grafts. None of the patients in era II developed IC (0% vs 18%; P = 0.013). There were fewer biliary complications in era II, and there was no increased risk of bleeding associated with the use of tPA. One-year graft survival was slightly better in era II (n = 24 patients with 1 year follow-up) (88% vs 80%; P = 0.14). CONCLUSIONS: Optimizing peritransplant conditions, such as shortening ischemic times with the use of thrombolytic donor flush, may prevent IC after DCD LT. With this approach, the DCD donor pool may be expanded.

Worse Long-term Patient Survival and Higher Cancer Rates in Liver Transplant Recipients With a History of Smoking.

BACKGROUND: This study is a retrospective review of liver transplant (LT) recipients to determine the impact of tobacco exposure on 10-year survival and de novo cancer (CA) incidence. METHODS: The records of 1275 consecutive LT patients were reviewed (2001 to 2011). Patients were categorized as current, previous, or never smokers (NS) at listing for LT. Additionally, smokers were stratified by pack-years of tobacco exposure. Events included patient death, cardiovascular events, and de novo cancers. Cox regression analysis was used to evaluate survival. A complete cause of death analysis is provided, as well as a detailed tumor registry. RESULTS: Current (n = 279) and previous smokers (n = 323) were more likely to have hepatocellular carcinoma (HCC) at transplant (25%, 29% vs 18% [NS], P < 0.001), and these 2 groups had higher HCC recurrence rates (21%, 14% vs 11% [NS], P = 0.18). De novo non-HCC CA was higher for current and previous smokers, compared to NS (18%, 16% vs 12% [NS], P = 0.05). Among those with de novo CA (n = 180), the 2 smoking groups were more likely to have non-skin CA (60%, 54% vs 27% [NS], P < 0.001). Patient survival at 10 years was worse for current smokers than the other study groups (55% vs 70%, P < 0.01). These results were largely mirrored with increased tobacco exposure. CONCLUSIONS: The LT outcomes are uniformly worse for patients with a history of smoking, and the risk of negative events increases with increasing tobacco use. Smokers have higher rates of HCC and recurrence, de novo cancer, and worse long-term survival. SUMMARY STATEMENT: This study summarizes the clinical outcomes for 1275 LT patients over 10 years, analyzing the impact of pre transplant recipient tobacco use. There are 47% of patients with a history of smoking. Because of demonstrated higher cancer rates and decreased survival, patients with a significant smoking history should be carefully scrutinized for liver transplantation.

Stem cells as a potential future treatment of pediatric intestinal disorders.

All surgical disciplines encounter planned and unplanned ischemic events that may ultimately lead to cellular dysfunction and death. Stem cell therapy has shown promise for the treatment of a variety of ischemic and inflammatory disorders where tissue damage has occurred. As stem cells have proven beneficial in many disease processes, important opportunities in the future treatment of gastrointestinal disorders may exist. Therefore, this article will serve to review the different types of stem cells that may be applicable to the treatment of gastrointestinal disorders, review the mechanisms suggesting that stem cells may work for these conditions, discuss current practices for harvesting and purifying stem cells, and provide a concise summary of a few of the pediatric intestinal disorders that could be treated with cellular therapy.

Induction immunosuppression with thymoglobulin and rituximab in intestinal and multivisceral transplantation.

BACKGROUND: Induction immunosuppression is now a common practice after intestinal and multivisceral transplantation. We report our experience in 27 adult recipients who received rituximab and rabbit antithymocyte globulin (rATG) in combination as induction agents. MATERIAL AND METHODS: Twenty-seven adult patients received 29 intestinal transplants between July 2004 and March 2007. All patients received induction immunosuppression therapy with rATG, rituximab, and steroids. Tacrolimums and a steroid taper were used for maintenance therapy. Patient and graft survival, episodes of rejection as well as posttransplant lymphoproliferative disease (PTLD) and graft-versus-host disease were analyzed. RESULTS: One-year patient and graft survival was 81% and 76%, respectively. Thirteen patients (48%) experienced 19 episodes of acute rejection (9 mild episodes, 2 moderate, and 8 severe). Patients with a multivisceral graft experienced less episodes of severe acute rejection (1 of 19, 5%) when compared with isolated intestinal transplants and modified multivisceral transplants (7 of 10, 70%). Two patients had episodes of skin graft-versus-host disease that responded to steroid boluses. PTLD was not seen in our series. Two patients developed cytomegalovirus enteritis. CONCLUSIONS: The combination of rATG and rituximab was an effective induction therapy in our preliminary data. The number and severity of rejection episodes increased when the liver was not included as part of the graft. An immunosuppression regimen including rATG, rituximab, and steroids may have a protective effect against PTLD and chronic rejection.