Prognostic models in end stage liver disease

Cirrhosis is a major cause of death worldwide, and is associated with significant health care costs. Even if milestones have been recently reached in understanding and managing end-stage liver disease (ESLD), the disease course remains somewhat difficult to prognosticate. These difficulties have already been acknowledged already in the past, when scores instead of single parameters have been proposed as valuable tools for short-term prognosis. These standard scores, like Child Turcotte Pugh (CTP) and model for end-stage liver disease (MELD) score, relying on biochemical and clinical parameters, are still widely used in clinical practice to predict short- and medium-term prognosis. The MELD score, which remains an accurate, easy-to-use, objective predictive score, has received significant modifications over time, in order to improve its performance especially in the liver transplant (LT) setting, where it is widely used as prioritization tool. Although many attempts to improve prognostic accuracy have failed because of lack of replicability or poor benefit with the comparator (often the MELD score or its variants), few scores have been recently proposed and validated especially for subgroups of patients with ESLD, as those with acute-on-chronic liver failure. Artificial intelligence will probably help hepatologists in the near future to fill the current gaps in predicting disease course and long-term prognosis of such patients.

Sex disparity and drug-induced liver injury

Drug-induced liver injury (DILI) is a potentially serious clinical condition that remains a major problem for patients, physicians and those involved in the development of new drugs. Population and hospital-based studies have reported incidences of DILI varying from 1.4 to 19.1/100.000. Overall, females have a 1.5- to 1.7-fold greater risk of developing adverse drug reactions and the female/male ratio increases after the age of 49 years, suggesting a clear susceptibility of DILI after menopause. Sex differences in pharmacokinetics and pharmacodynamic, sex-specific hormonal effects or interaction with signalling molecules that can influence drug efficacy and safety and differences in abnormal immune response following drug exposure are the main probable causes of the higher vulnerability observed among female patients. A novel phenotype of autoimmune-mediated DILI following the use of check-point inhibitors in oncology and haematology has been recently described. Finally, there have been increasing reports of DILI associated with use of herbal and dietary supplements that is more frequently reported in women.

Impact of the COVID-19 pandemic on Gastroenterology Divisions in Italy: A national survey

BACKGROUND

In Italy, the spread of the COVID-19 pandemic has stressed the entire healthcare system and required a huge re-organization of many Divisions, including those of Gastroenterology.

AIMS

to assess the impact of COVID-19 pandemic on Gastroenterology Divisions across Italy.

METHODS

All members of the Italian Society of Gastroenterology (SIGE) were invited to answer a web-based survey.

RESULTS

Data of 121 hospitals from all 20 Italian regions were analyzed. Overall, 10.7% Gastroenterology Divisions have been converted to Covid Units. Outpatients consultations, endoscopic and ultrasound procedures were limited to urgencies and oncology indications in 85.1%, 96.2% and 72.2% of Units, respectively, and 46.7% of them suspended the screening for colorectal cancer. Moreover, 72.2% of the staff received a training for use of personal protective equipment, although 45.5% did not have sufficient devices for adequate replacement. Overall, 132 healthcare workers in 41 Gastroenterology Divisions were found to be infected.

CONCLUSION

This is the first study to evaluate, at a country level, the impact of COVID-19 outbreak on Gastroenterology Divisions. Substantial changes of practice and reduction of procedures have been recorded in the entire country. The long-term impact of such modifications is difficult to estimate but potentially very risky for many digestive diseases.

Transjugular intrahepatic portosystemic shunt in non-cirrhotic portal hypertension related to cystic fibrosis in a lung transplant patient

Liver involvement is not uncommon in patients with cystic fibrosis (CF). Even if serious complications as non-cirrhotic portal hypertension, cirrhosis and liver failure rarely occur, they are associated with impaired survival and reduced quality of life. Herein, we have reported the first case of a patient with CF and non-cirrhotic portal hypertension who underwent transjugular intrahepatic portosystemic shunt placement for recurrent variceal bleeding after bilateral lung transplantation, and we have reviewed the available literature pertaining to this field.

The road map toward an hepatitis C virus-free transplant population

Antiviral therapy to eradicate hepatitis C virus (HCV) infection improves outcomes in patients undergoing liver transplantation (LT) for advanced chronic HCV with or without hepatocellular carcinoma. Traditionally, antiviral therapy focused on the use of interferon (IFN)-based regimens, with antiviral treatment initiated in the posttransplant period once recurrent HCV disease with fibrosis in the allograft was identified. The use of IFN-based therapy was limited in pretransplant patients with advanced liver disease. Earlier intervention, either before transplantation or early after LT, is now feasible with the advent of second-generation direct-acting antiviral agents (DAAs) with superior tolerability and efficacy to IFN-based therapy. These agents have the potential to reduce the number of patients developing HCV-related complications requiring LT and retransplantation, as well as reducing the demand for donor organs. We discuss the pros and cons of pretransplant, peritransplant, and posttransplant therapy with current DAAs, citing available data from clinical trials and real-world experience.

Liver Retransplantation for Hepatic Abscess Due to Hepatic Artery Thrombosis: A Case Report

INTRODUCTION

Hepatic artery thrombosis (HAT) is a well-recognized complication of liver transplantation (LT). HAT is an important risk factor for infectious, in particular hepatic abscess, which can cause graft loss and increasing morbidity and mortality.

CASE REPORT

We present a case report of complicated LT in a 52-year-old Caucasian man with primary sclerosing cholangitis. In 2007 the patient was included on the waiting list in Padua for LT. In 2012 the patient underwent percutaneous transhepatic biliary drainage for bile duct stricture, complicated with acute pancreatitis. A diagnostic laparoscopy was performed with choledochotomy and Kehr's T tube drainage. On February 14, 2012, the patient underwent LT with arterial reconstruction and choledochojejunostomy. The postoperative course was complicated with HAT, multiple liver abscesses, and sepsis associated with bacteremia due to Enterococcus faecium despite massive intravenous antibiotic therapy and percutaneous drainages. On November 28, 2012, the patient underwent retransplantation. Four years after transplantation the patient is still in good general condition.

CONCLUSION

Hepatic abscess formation secondary to HAT following LT is a major complication associated with important morbidity and mortality. In selected cases retransplantation should be considered as our case demonstrates.

Polyclonal and monoclonal B lymphocytes response in HCV-infected patients treated with direct-acting antiviral agents

Hepatitis C virus (HCV) chronic infection can be associated with extrahepatic manifestations such as mixed cryoglobulinaemia and lymphoproliferative disorders that are endowed with increased rates of morbidity and all-cause mortality. In this study, we used flow cytometry to evaluate the effect of interferon-free antiviral treatment on peripheral blood lymphocytes in HCV-infected patients with or without associated lymphoproliferative disorders. Flow cytometry analysis of peripheral blood lymphocytes was performed at baseline and at the end of treatment. In HCV-infected patients with lymphoproliferative disorders, we evaluated immunoglobulin (Ig) light chain κ/λ ratio variations as a measure of monoclonal B-cell response to antiviral therapy. Healthy volunteers were enrolled as controls. A total of 29 patients were included, nine with and 20 without lymphoproliferative disorders. Sustained virological response was achieved in 29 of 29 patients. We observed a significant reduction in the B-cell compartment (39% global reduction) in eight of nine HCV-infected patients with lymphoproliferative disorders after viral clearance. We recognized the same trend, even if less pronounced, in HCV-infected patients without lymphoproliferative disorders (9% global reduction). Among HCV-infected patients with lymphoproliferative disorders, three showed an improvement/normalization of the immunoglobulin light chain ratio, whereas in the remaining six patients monoclonal B cells persisted to be clonally restricted even 1 year after the end of treatment. Our data show that DAAs treatment can be effective in reducing the frequency of pathological B cells in the peripheral blood of HCV-infected patients affected by HCV-associated lymphoproliferative disorders; however, monoclonal populations can persist after viral eradication.

Long-term outcomes of direct acting antivirals in post-transplant advanced hepatitis C virus recurrence and fibrosing cholestatic hepatitis

Long-term functional outcomes of sofosbuvir-based antiviral treatment were evaluated in a cohort study involving 16 Italian centres within the international compassionate use programme for post-transplant hepatitis C virus (HCV) recurrence. Seventy-three patients with cirrhosis (n=52) or fibrosing cholestatic hepatitis (FCH, n=21) received 24-week sofosbuvir with ribavirin±pegylated interferon or interferon-free sofosbuvir-based regimen with daclatasvir/simeprevir+ribavirin. The patients were observed for a median time of 103 (82-112) weeks. Twelve of 73 (16.4%) died (10 non-FCH, 2 FCH) and two underwent re-LT. Sustained virological response was achieved in 46 of 66 (69.7%): 31 of 47 (66%) non-FCH and 15 of 19 (79%) FCH patients. All relapsers were successfully retreated. Comparing the data of baseline with last follow-up, MELD and Child-Turcotte-Pugh scores improved both in non-FCH (15.3±6.5 vs 10.5±3.8, P<.0001 and 8.4±2.1 vs 5.7±1.3, P<.0001, respectively) and FCH (17.3±5.9 vs 10.1±2.8, P=.001 and 8.2±1.6 vs 5.5±1, P=.001, respectively). Short-treatment mortality was higher in patients with baseline MELD≥25 than in those with MELD<25 (42.9% vs 4.8%, P=.011). Long-term mortality was 53.3% among patients with baseline MELD≥20 and 7.5% among those with MELD<20 (P<.0001). Among deceased patients 75% were Child-Turcotte-Pugh class C at baseline, while among survivors 83.9% were class A or B (P<.0001). Direct acting antivirals-based treatments for severe post-transplant hepatitis C recurrence, comprising fibrosing cholestatic hepatitis, significantly improve liver function, even without viral clearance and permit an excellent long-term survival. The setting of severe HCV recurrence may require the identification of "too-sick-to-treat patients" to avoid futile treatments.

BioInt: an integrative biological object-oriented application framework and interpreter

BioInt, a biological programming application framework and interpreter, is an attempt to equip the researchers with seamless integration, efficient extraction and effortless analysis of the data from various biological databases and algorithms. Based on the type of biological data, algorithms and related functionalities, a biology-specific framework was developed which has nine modules. The modules are a compilation of numerous reusable BioADTs. This software ecosystem containing more than 450 biological objects underneath the interpreter makes it flexible, integrative and comprehensive. Similar to Python, BioInt eliminates the compilation and linking steps cutting the time significantly. The researcher can write the scripts using available BioADTs (following C++ syntax) and execute them interactively or use as a command line application. It has features that enable automation, extension of the framework with new/external BioADTs/libraries and deployment of complex work flows.

Survival benefit of transplantation for recurrence of hepatocellular carcinoma after liver resection

BACKGROUND

Liver transplantation (LT) for hepatocellular carcinoma (HCC) can be used for tumor recurrence after liver resection (LR) both for initially transplant-eligible patients as conventional salvage therapy (ST) and for non-transplant-eligible patients (beyond Milan criteria) with a goal of downstaging (DW). The aim of this study was to compare the intention-to-treat (ITT) survival rates of patients who are listed for LT, according to these two strategies.

METHODS

We analyzed a prospective database of 399 consecutive patients who underwent hepatic resection for HCC from 2002 to 2011 to identify patients included in the waiting list for tumor recurrence. Intention-to-treat (ITT) survivals were compared with those of patients resected for HCC within and beyond Milan criteria in the same period and not included in the LT waiting list.

RESULTS

The study group consisted of 42 patients, 28 in the ST group (within Milan) and 14 in the DW group (beyond Milan). The 5-year ITT survival rate was similar between the 2 groups, being 64% for ST and 60% for DW (P=.84). Twenty-five patients (15 ST and 10 DW) underwent LT, 13 (10 ST and 3 DW) were still awaiting LT, 4 (3 ST and 1 DW) dropped out of the waiting list because of tumor progression, and 7 (5 ST [33%] and 2 DW [20%]) had tumor recurrence. The 5-year ITT survival of ST patients was similar to that of 252 in-Milan HCC patients resected only (P=.3), whereas 5-year ITT survival of DW patients was significantly higher (P<.01) than that of 105 beyond-Milan HCC patients resected only.

CONCLUSIONS

LR seems to be a safe and effective therapy both as alternative to transplantation and as downstaging strategy for intermediate-advanced HCC. The survival benefit of salvage LT, however, seems to be higher in the 2nd than in the 1st group.

Physical activity in solid organ transplant recipients: organizational aspects and preliminary results of the Italian project

Most of the difficulties when trying to realize the proposal to prescribe physical activity for transplantation patients come from patient attitudes and cultural beliefs that ignore the benefits of exercise, but there also are organizational aspects arising from the difficulties that these patients face in accessing supervised exercise facilities. To address these difficulties, the Italian study project "Transplant … and Now Sport" was developed based on a model of cooperation among transplantation specialists, sports physicians, and exercise specialists organized as a team combining their specific skills to effectively actuate the physical exercise programs. This preliminary report is based on 26 patients (16 male, 10 female; 47.8±10.0 years old; 21 kidney and 5 liver transplantations; time from transplantation 2.3±1.4 years) who performed prescribed and supervised exercises consisting of 3 sessions per week of aerobic and strengthening exercises for 1 year. Preliminary results show a significant decrease in body mass index (t=1.966; P<.05) and a significant increase in peak aerobic power (t=4.535; P<.01) and maximum workload (t=4.665; P<.01) on the incremental cycling test. Also maximum strength of knee extensors (t=2.933; P<.05) and elbow flexors (t=2.450; P<.05) and countermovement jump performance (t=2.303; P<.05) significantly increased. Creatinine and proteinuria tended to decrease, but the differences were not significant. In health-related quality of life assessed by the SF-36 questionnaire, the Bodily Pain, General Health, Vitality, Social Functioning, and Role Emotional scale scores showed a significant improvement (P<.05). Preliminary results of the study protocol "Transplant…and Now Sport" show the positive effects of the model based on cooperation among transplantation centers, sports medicine centers, and gyms in the administration of a supervised exercise prescription. These data should be considered a contribution to developing and promoting further detailed exercise protocols and to fostering improved posttransplantation health and survival, helping to ensure that physical activity becomes a safe routine medical treatment plan of patient management.

A Multistep, Consensus-Based Approach to Organ Allocation in Liver Transplantation: Toward a "Blended Principle Model"

Since Italian liver allocation policy was last revised (in 2012), relevant critical issues and conceptual advances have emerged, calling for significant improvements. We report the results of a national consensus conference process, promoted by the Italian College of Liver Transplant Surgeons (for the Italian Society for Organ Transplantation) and the Italian Association for the Study of the Liver, to review the best indicators for orienting organ allocation policies based on principles of urgency, utility, and transplant benefit in the light of current scientific evidence. MELD exceptions and hepatocellular carcinoma were analyzed to construct a transplantation priority algorithm, given the inequity of a purely MELD-based system for governing organ allocation. Working groups of transplant surgeons and hepatologists prepared a list of statements for each topic, scoring their quality of evidence and strength of recommendation using the Centers for Disease Control grading system. A jury of Italian transplant surgeons, hepatologists, intensivists, infectious disease specialists, epidemiologists, representatives of patients' associations and organ-sharing organizations, transplant coordinators, and ethicists voted on and validated the proposed statements. After carefully reviewing the statements, a critical proposal for revising Italy's current liver allocation policy was prepared jointly by transplant surgeons and hepatologists.

Risk of Kaposi sarcoma after solid-organ transplantation: multicenter study in 4,767 recipients in Italy, 1970-2006

Given the high prevalence of infection with human herpesvirus type 8, Italy is an area of utmost interest for studying Kaposi sarcoma (KS). We investigated the risk of KS in transplant recipients compared with the general population. A longitudinal study was performed from 1970 to 2006 in 4767 kidney, heart, liver, and lung transplant recipients from 7 Italian transplantation centers. The sample included 72.3% male patients with an overall patient median age of 48 years. Patient-years (PYs) at risk for KS were computed from 30 days posttransplantation to the date of KS, death, last follow-up, or study closure (December 31, 2007). Standardized incidence ratios (SIRs) and 95% confidence intervals were computed to quantify the risk of KS in transplant recipients compared with the general Italian population. Incidence rate ratios were computed to identify risk factors using adjusted Poisson regression. Based on 33,621 PYs, KS was diagnosed in 73 patients (62 men): 31 in kidney recipients, 27 in heart recipients, 8 in liver recipients, and 7 in lung recipients. The overall incidence was 217 cases per 10(5) PYs, with a significantly increased SIR of 125. SIR was particularly high in women (n = 34) and lung recipients (n = 428) but decreased significantly with time posttransplantation. The primary predictors of increased risk of KS were male sex, older age, and lung transplantation. A 5-fold reduction was observed after 18 months posttransplantation. After adjustment, patients born in southern Italy compared with northern Italy demonstrated a significant 2.2-fold increased risk. Our findings confirm that in the early posttransplantation period, Italian patients who have undergone solid-organ transplantation, particularly those from southern Italy and those who are lung recipients, are at greater risk of KS compared with the general population. These findings underscore the need for appropriate models for monitoring transplant recipients for KS, especially those at greater risk and, in particular, in the early postoperative period.

Alcohol abuse and de novo tumors in liver transplantation

INTRODUCTION

Organ transplant recipients show an increased incidence of cancer ranging from 4% to 16% owing to several causes: immunosuppression, viral infection, individual predisposition, and so on.

MATERIALS AND METHODS

We retrospectively reviewed the records of 43/683 (6.3%) recipients of 734 liver transplants performed from November 1991 to November 2008 who experienced a de novo neoplasm.

CONCLUSION

Alcohol abuse significantly increased the rate of all de novo neoplasms and particularly pharyngogastroesophageal cancers among population of liver transplant recipients. Minimization of immunosuppressive therapy is necessary to reduce the risk of a de novo neoplasm. Strict posttransplant follow-up is required to identify early gastroenteric tumors.

Progression of hepatocellular carcinoma before liver transplantation: dropout or liver transplantation?

BACKGROUND

Tumor progression before liver transplantation (OLT) is the main cause of dropout from the waiting list (WL) of patients with hepatocellular carcinoma (HCC). The aim of this study was to show a correlation between adopted dropout criteria and dropout/intention-to-treat survival rates of WL HCC patients.

METHODS

The study period was 2000 to 2007. The dropout criteria were macroscopic vascular invasion, metastases, or a poorly differentiated tumor. Adult patients with benign chronic liver disease enlisted for primary OLT in the same period represented the control group.

RESULTS

Dropout probability of study (n = 128) versus control group (n = 377) subjects was similar: namely, 12% at 1 year in both groups (P = NS). Intention-to-treat survival curve of the HCC group overlapped that of the benign group (5-year survival rates were 73% and 71%, respectively; P = NS). At the time of listing, 103 study group patients were within the Milan criteria (MC): among these patients, 29 (28%) showed tumor progression beyond MC before OLT. Simulating the dropout of these 29 patients at the time of diagnosis of tumor progression, we compared the dropout probability of the 103 patients within MC with that of the control group. As a result, the 1- and 2-year dropout rates became 37% and 53%, respectively, in the study group, which were significantly higher than those in the controls (P < .01).

CONCLUSION

HCC patients on the WL showed a significantly greater dropout rate than subjects with benign cirrhosis when too restrictive radiologic dropout criteria were used. The adoption of criteria more related to biological aggressiveness of a tumor decreased the dropout risk for HCC patients without impairing their intention-to-treat survival rates.

De novo tumors are a major cause of late mortality after orthotopic liver transplantation

The purpose of this study was to describe de novo post-orthotopic liver transplantation (OLT) malignancies for comparison with incidence rates in Italian cancer registries. Three hundred thirteen OLT patients engrafted from 1991 to 2006 and surviving 12 months without a previous diagnosis of cancer were evaluated for the development of de novo malignancies excluding nonmelanoma skin cancers. During a total follow-up time of 1753 PYs, 40 (12.8%) de novo malignancies were diagnosed in 40 recipients. The most common cancers were non-Hodgkin lymphoma (NHL; 20%), cancer of the head and neck (17%), Kaposi sarcoma (KS; 17%), and esophageal tumors (12%). The 1-, 3-, 5-, and 10-year estimated survival rates were 70%, 56%, 48%, and 39%. Patients with de novo cancers showed a lower 10-years survival rate (P = .0047) than patients without (39% vs 75%). The risk of cancer after OLT was 3-fold higher than that of the general population of the same age and gender (95% confidence interval [CI], 2.0-4.3). De novo tumor sites or types with significantly elevated standardized incidence ratios (SIRs) included KS (SIRs = 212), NHL (SIRs = 13.7), oesophagus (SIRs = 18.7), melanoma (SIRs = 10.1), and head and neck cancers (SIRs = 4.6). Tumors after OLT were associated with lower long-term survival, confirming that cancer is a major cause of late mortality.

Use of grafts from anti-HBc-positive donors in liver transplantation: a 5-year, single-center experience

INTRODUCTION

Liver transplantation (OLT) is the treatment of choice for advanced hepatic disease. The growing gap between waiting list patients and the number of donations has led to acceptance of less than optimal donors. The aim of this study was to evaluate the 5-year experience with anti hepatitis B core antigen (HBc)-positive liver donors.

PATIENTS AND METHODS

All recipients of anti-HBc-positive grafts from January 2005 to December 2010 were evaluated annually after OLT for liver disease etiology, Model for End-Stage Liver Disease (MELD) score, and the presence of hepatocellular carcinoma (HCC) liver biopsy histology and serology for hepatitis B virus (HBsAg, anti-HBs, HBV-DNA), hepatitis C virus, and hepatitis D virus as well as antiviral prophylaxis to prevent de novo HBV.

RESULTS

Among the 249 OLT performed from January 2005 to December 2010, (9.3%) cases used grafts from anti-HBc-positive donors. Etiologics of liver disease among the recipients were HBV (n = 13; 32.5%), HCV (n = 13; 32.5%) or other causes (n = 14; 35%). In 20 of the 40 patients (50%), HCC was found in the explanted organ. Of 40 recipients of anti-HBc-positive grafts 11 died, and 7 (17.5%) required retransplantation. Various regimens were employed as post-transplantation antiviral prophylaxis: (l) Immune globulin (25.8%); (2) Oral antiviral drugs (9.7%); and (3) combined prophylaxis (51.6%) or no treatment (12.9%). No difference was observed in patient or graft survival in relation to the etiology of liver disease, the MELD score, or the presence of HCC at the time of OLT, except graft survival was significantly reduced among recipient who underwent transplantation for non-HBV or non-HCV liver diseases compared with those engrafted due to viral hepatitis (P = .0062). No difference was observed in histologic features (grading and staging) compared with the antiviral prophylactic therapy; the 2 patients (5%) who developed de novo HBV had not received prophylaxis after OLT.

CONCLUSIONS

Matching anti-HBc-positive grafts to recipients without HBV infection before OLT, may be especially safe.

Use of grafts from anti-HBc-positive donors in liver transplantation: a 5-year, single-center experience

INTRODUCTION

Liver transplantation (OLT) is the treatment of choice for advanced hepatic disease. The growing gap between waiting list patients and the number of donations has led to acceptance of less than optimal donors. The aim of this study was to evaluate the 5-year experience with anti hepatitis B core antigen (HBc)-positive liver donors.

PATIENTS AND METHODS

All recipients of anti-HBc-positive grafts from January 2005 to December 2010 were evaluated annually after OLT for liver disease etiology, Model for End-Stage Liver Disease (MELD) score, and the presence of hepatocellular carcinoma (HCC) liver biopsy histology and serology for hepatitis B virus (HBsAg, anti-HBs, HBV-DNA), hepatitis C virus, and hepatitis D virus as well as antiviral prophylaxis to prevent de novo HBV.

RESULTS

Among the 249 OLT performed from January 2005 to December 2010, (9.3%) cases used grafts from anti-HBc-positive donors. Etiologics of liver disease among the recipients were HBV (n = 13; 32.5%), HCV (n = 13; 32.5%) or other causes (n = 14; 35%). In 20 of the 40 patients (50%), HCC was found in the explanted organ. Of 40 recipients of anti-HBc-positive grafts 11 died, and 7 (17.5%) required retransplantation. Various regimens were employed as post-transplantation antiviral prophylaxis: (l) Immune globulin (25.8%); (2) Oral antiviral drugs (9.7%); and (3) combined prophylaxis (51.6%) or no treatment (12.9%). No difference was observed in patient or graft survival in relation to the etiology of liver disease, the MELD score, or the presence of HCC at the time of OLT, except graft survival was significantly reduced among recipient who underwent transplantation for non-HBV or non-HCV liver diseases compared with those engrafted due to viral hepatitis (P = .0062). No difference was observed in histologic features (grading and staging) compared with the antiviral prophylactic therapy; the 2 patients (5%) who developed de novo HBV had not received prophylaxis after OLT.

CONCLUSIONS

Matching anti-HBc-positive grafts to recipients without HBV infection before OLT, may be especially safe.

Balancing donor and recipient risk factors in liver transplantation: the value of D-MELD with particular reference to HCV recipients

Donor-recipient match is a matter of debate in liver transplantation. D-MELD (donor age × recipient biochemical model for end-stage liver disease [MELD]) and other factors were analyzed on a national Italian database recording 5946 liver transplants. Primary endpoint was to determine factors predictive of 3-year patient survival. D-MELD cutoff predictive of 5-year patient survival <50% (5yrsPS<50%) was investigated. A prognosis calculator was implemented (http://www.D-MELD.com). Differences among D-MELD deciles allowed their regrouping into three D-MELD classes (A < 338, B 338-1628, C >1628). At 3 years, the odds ratio (OR) for death was 2.03 (95% confidence interval [CI], 1.44-2.85) in D-MELD class C versus B. The OR was 0.40 (95% CI, 0.24-0.66) in class A versus class B. Other predictors were hepatitis C virus (HCV; OR = 1.42; 95% CI, 1.11-1.81), hepatitis B virus (HBV; OR = 0.69; 95% CI, 0.51-0.93), retransplant (OR = 1.82; 95% CI, 1.16-2.87) and low-volume center (OR = 1.48; 95% CI, 1.11-1.99). Cox regressions up to 90 months confirmed results. The hazard ratio was 1.97 (95% CI, 1.59-2.43) for D-MELD class C versus class B and 0.42 (95% CI, 0.29-0.60) for D-MELD class A versus class B. Recipient age, HCV, HBV and retransplant were also significant. The 5yrsPS<50% cutoff was identified only in HCV patients (D-MELD ≥ 1750). The innovative approach offered by D-MELD and covariates is helpful in predicting outcome after liver transplantation, especially in HCV recipients.

Microwave thermal ablation for hepatocarcinoma: six liver transplantation cases

Surgical resection for malignant hepatic tumors, especially hepatocarcinoma (HCC), has been demonstrated to increase overall survival; however, the majority of patients are not suitable for resection. Radiofrequency ablation (RFA) is the most widely used modality for radical treatment of small HCC (<3 cm). It improves 5-year survival compared with standard chemotherapy and chemical ablation, allowing down-staging of unresectable hepatic masses. Microwave ablation (MWA) has been extensively applied in Asia and was recently introduced in the United States of America and Europe with excellent results, especially with regard to large unresectable HCC. Our single-center experience between May 2009 and October 2010 included application of MWA to 154 patients of median age ± standard deviation of 63.5 ± 8.5 years, 6 males, and 1 female, of mean Model for End-Stage Liver Disease (MELD) score (10.1 ± 3.8). The HCC included, hepatitis C virus (HCV)-related (n=70; 45.5%); alcool (ETOH)-related (n=42; 27%), hepatitis B virus (HBV)-related (n=16; 10.5%); and cryptogenic cases (n=26; 17%). The cases were performed for radical treatment down-staging for multifocal pathology or bridging liver transplantation to orthotopic (OLT) in selected patients with single nodules. A computed tomography (CT) scan was performed at 1 month after the surgical procedure to evalue responses to treatment. Among 6 selected patients who underwent OLT; 5 (83.3%) showed disease-free survival at one-year follow-up. The radical treatment achieved no intraoperative evidence of tumor spread or of pathological signs of active HCC among the explanted liver specimens. In conclusion, a MWA seemed to be a safe novel approach to treat HCC and could serve as a "bridge" to OLT and down-staging for patients with HCC.

Risk factors in liver retransplantation: a single-center experience

Liver retransplantation (Re-OLT) is one of the most debated issues in medicine over the past decade. Re-OLT, currently is accepted for patients with irreversible failure of a hepatic graft caused by primary nonfunction (PNF), hyperacute/chronic rejection, or hepatic artery thrombosis (HAT); whereas it is still controversial for patients with recurrent viral disease, in particular hepatitis C virus (HCV) cirrhosis. Patient and graft survival rates are lower than those observed after primary liver transplantation (OLT). The aim of the present study was to analyze the risk factors that adversely affect survival after Re-OLT in a single center. Medical data were collected for 23 patients who underwent Re-OLT from November 2002 to December 2008 including six men and seven women of mean age of 51.3 years. The most frequent indications for Re-OLT were: PNF (69.5%; 16/23), HCV recurrence (8.6%; 2/23), or HAT (8.6%; 2/23). Mean Model for End-Stage Liver Disease (MELD) at Re-OLT was 27.7 (range = 9-40). After a mean follow-up of 37.4 ± 30 (standard deviation) months, 43% (10/23) of patients had died, including 70% within the first 2 months after Re-OLT. Sepsis represented the commonest cause of death (40%). Re-OLT was performed for PNF among 90% of succumbing patients. As regards dead patients, 4/10 were HCV(+) whose causes of death were sepsis (n=2), alcoholic cirrhosis (n=2), and undetermined (n=1). Comparing patients who died after liver Re-OLT versus alive patients, we did not find any significant difference in terms of mean MELD (28.6 vs 27; P=NS), MELD > 25 (60% vs 61.5%, P=NS), donor age > 60 years (30% vs 15.3%, P=NS), HCV(+) (40% vs 62%, P = NS), or time interval from OLT to Re-OLT (12.2 vs 777.7 days, P=NS). Patient survivals after Re-OLT were 67% at 3 years and 50% at 5 years, which were lower than those of first transplantations, as reported by other European and International Centers. Forty percent of deaths after Re-OLT occurred among HCV(+) recipients, but for reasons unrelated to HCV infection.

Balancing donor and recipient risk factors in liver transplantation: the value of D-MELD with particular reference to HCV recipients

Donor-recipient match is a matter of debate in liver transplantation. D-MELD (donor age × recipient biochemical model for end-stage liver disease [MELD]) and other factors were analyzed on a national Italian database recording 5946 liver transplants. Primary endpoint was to determine factors predictive of 3-year patient survival. D-MELD cutoff predictive of 5-year patient survival <50% (5yrsPS<50%) was investigated. A prognosis calculator was implemented (http://www.D-MELD.com). Differences among D-MELD deciles allowed their regrouping into three D-MELD classes (A < 338, B 338-1628, C >1628). At 3 years, the odds ratio (OR) for death was 2.03 (95% confidence interval [CI], 1.44-2.85) in D-MELD class C versus B. The OR was 0.40 (95% CI, 0.24-0.66) in class A versus class B. Other predictors were hepatitis C virus (HCV; OR = 1.42; 95% CI, 1.11-1.81), hepatitis B virus (HBV; OR = 0.69; 95% CI, 0.51-0.93), retransplant (OR = 1.82; 95% CI, 1.16-2.87) and low-volume center (OR = 1.48; 95% CI, 1.11-1.99). Cox regressions up to 90 months confirmed results. The hazard ratio was 1.97 (95% CI, 1.59-2.43) for D-MELD class C versus class B and 0.42 (95% CI, 0.29-0.60) for D-MELD class A versus class B. Recipient age, HCV, HBV and retransplant were also significant. The 5yrsPS<50% cutoff was identified only in HCV patients (D-MELD ≥ 1750). The innovative approach offered by D-MELD and covariates is helpful in predicting outcome after liver transplantation, especially in HCV recipients.

Management of hepatitis C virus infection recurrence after liver transplantation: an overview

Hepatitis C virus (HCV) infection is the major indication for liver transplantation worldwide. Its recurrence is virtually universal. Once reinfection is established, progression to cirrhosis occurs in 25%-30% of recipients within 5 years. Several studies have attempted to identify the ideal antiviral treatment for liver transplant recipients. At present, the management of recurrent HCV infection in liver transplant recipients is based on widely accepted indications, which represent a reliable guide to identify the "ideal" candidate for therapy, when therapy should be started, and what is to be expected in terms of side effects and response to treatment.

Fibrosis progression and the pros and cons of antiviral therapy for hepatitis C virus recurrence after liver transplantation: a review

The progression of fibrosis due to hepatitis C virus (HCV) recurrence after liver transplantation (OLT) is faster than in the pretransplant setting, leading to histologically documented cirrhosis within 5 years in 25% to 30% of cases. Whether it is associated with biliary complications or previous alcohol abuse, recurrent HCV is the main cause of graft failure and death after OLT. The most important donor risk factor for HCV recurrence is advanced donor age. The disease's course is even more aggressive if it is associated with anti-HCV positivity or graft steatosis. The type of calcineurin inhibitor does not seem to influence HCV recurrence. Avoiding or slowly tapering steroids has been associated with less disease recurrence, while steroid pulses to treat acute rejection episodes have been associated with a worse progression of fibrosis. Antiviral therapy (AT) is not always recommended in OLT patients, but is of some benefit. Fibrosis has been shown to ameliorate in sustained virological responders to AT and to progress significantly more in nonresponders. Using long-term maintenance, AT has recently been shown to increase the probability of biochemical and histological responses, regardless of the timing of the HCV recurrence. In conclusion, the donor- recipient match should be assessed to limit HCV recurrences and their severity; AT is recommended to reduce or reverse the progression of fibrosis.

Pharmacokinetics and efficacy of intravenous or intramuscular hepatitis B immunoglobulins in prophylaxis of hepatitis B after liver transplantation

AIM

The use of hepatitis B immunoglobulin (HBIg) combined with nucleos(t)ide analogues (NUCs) has improved outcomes in post-hepatitis B (PHB) liver transplant (LT), reducing the 1-year recurrence rate below 10%. The aim of this study was to evaluate efficacy and pharmacokinetics of prophylaxis with NUC(s) and intravenous (iv-) or intramuscular (im-) HBIg in 33 PHBLTs, transplanted for more than 1 year.

METHODS

During the first six months of the study, 18 subjects received 5000 IU of iv-HBIg every four weeks and 15 patients 2160 IU/12 mL of im-HBIg every two weeks. In the following six months, 31 subjects were switched to two different concentrations of im-HBIg, 2160/12 mL (16 patients) or 2000 IU/6 mL every two weeks (15 patients).

RESULTS

All patients remained HBsAg-negative and 30/31 maintained anti-HBs >100 IU/L. Overall mean anti-HBs titer during treatment was 363 IU/mL. Mean HBIg half-life was 21.4, 27.3 and 26 days with intravenous, diluted or concentrated im-preparations, respectively.

CONCLUSION

These results confirm an analogue efficacy and tolerance of iv- and im-HBIg combined with antivirals in prophylaxis of hepatitis B after LT. Anti-HBs titers three times higher than aimed and four weeks mean half-life could suggest the reduction of doses and the elongation of the interval of administration of im-HBIg.

Estimation of the harm to the waiting list as a crucial factor in the selection of patients with hepatocellular carcinoma for liver transplantation

BACKGROUND

Long-term survival rates after orthotopic liver transplantation (OLT) for patients with hepatocellular carcinoma (HCC) of any size and number may now be predicted using the Metroticket calculator. The aim of this study was to evaluate the minimum post-OLT survival threshold that would justify the selection of a patient with HCC for OLT.

METHODS

We used a Markov model, recently developed at the University of Michigan, which assumes that a patient with HCC should undergo OLT if his or her transplant benefit is greater than the cumulative harm to the rest of the waiting list (WL). In the base case, we considered a patient with a low survival perspective without OLT (5-year survival rate, 10%). The data sources to construct and validate the model were as follows: the Organ Procurement and Transplantation Network report, and our prospective database.

RESULTS

Our center was generally characterized by lower WL mortalities, although there were lower transplant probabilities for both HCC and non-HCC patients than the average US center. The proportion of HCC patients on the WL was higher in Padua (25%) than in the United States (10%). The calculated harm to the WL was 434 quality-adjusted days of life in Padua, and 957 in the United States (P < .01). The OLT benefit outweighed the harm to the WL when the 5-year post-OLT survival rate was higher than 30% in Padua, and 61% in the United States.

CONCLUSIONS

In a decision model including the concepts of transplantation benefit and harm to the WL, the minimum 5-year post-OLT survival threshold justifying the selection of a patient with HCC for OLT in Padua was 30%.

The structure of Jann_2411 (DUF1470) from Jannaschia sp. at 1.45 Å resolution reveals a new fold (the ABATE domain) and suggests its possible role as a transcription regulator

The crystal structure of Jann_2411 from Jannaschia sp. strain CCS1, a member of the Pfam PF07336 family classified as a domain of unknown function (DUF1470), was solved to a resolution of 1.45 Å by multiple-wavelength anomalous dispersion (MAD). This protein is the first structural representative of the DUF1470 Pfam family. Structural analysis revealed a two-domain organization, with the N-terminal domain presenting a new fold called the ABATE domain that may bind an as yet unknown ligand. The C-terminal domain forms a treble-clef zinc finger that is likely to be involved in DNA binding. Analysis of the Jann_2411 protein and the broader ABATE-domain family suggests a role as stress-induced transcriptional regulators.

The structure of the first representative of Pfam family PF09836 reveals a two-domain organization and suggests involvement in transcriptional regulation

Proteins with the DUF2063 domain constitute a new Pfam family, PF09836. The crystal structure of a member of this family, NGO1945 from Neisseria gonorrhoeae, has been determined and reveals that the N-terminal DUF2063 domain is likely to be a DNA-binding domain. In conjunction with the rest of the protein, NGO1945 is likely to be involved in transcriptional regulation, which is consistent with genomic neighborhood analysis. Of the 216 currently known proteins that contain a DUF2063 domain, the most significant sequence homologs of NGO1945 (∼40-99% sequence identity) are from various Neisseria and Haemophilus species. As these are important human pathogens, NGO1945 represents an interesting candidate for further exploration via biochemical studies and possible therapeutic intervention.

Structures of the first representatives of Pfam family PF06684 (DUF1185) reveal a novel variant of the Bacillus chorismate mutase fold and suggest a role in amino-acid metabolism

The crystal structures of BB2672 and SPO0826 were determined to resolutions of 1.7 and 2.1 Å by single-wavelength anomalous dispersion and multiple-wavelength anomalous dispersion, respectively, using the semi-automated high-throughput pipeline of the Joint Center for Structural Genomics (JCSG) as part of the NIGMS Protein Structure Initiative (PSI). These proteins are the first structural representatives of the PF06684 (DUF1185) Pfam family. Structural analysis revealed that both structures adopt a variant of the Bacillus chorismate mutase fold (BCM). The biological unit of both proteins is a hexamer and analysis of homologs indicates that the oligomer interface residues are highly conserved. The conformation of the critical regions for oligomerization appears to be dependent on pH or salt concentration, suggesting that this protein might be subject to environmental regulation. Structural similarities to BCM and genome-context analysis suggest a function in amino-acid synthesis.

Risk factors for portal venous thrombosis after splenectomy in patients with cirrhosis and portal hypertension (Br J Surg 2010; 97: 910-916)

Background

Portal venous thrombosis (PVT) is a potentially fatal complication following splenectomy. Its mechanisms and risk factors are poorly understood, especially in patients with cirrhosis and portal hypertension. This study investigated risk factors for PVT following splenectomy in such patients.

Methods

All consecutive patients with cirrhosis who underwent splenectomy in Kyushu University Hospital between 1998 and 2004 were included in this retrospective study. They were divided into two groups based on the presence or absence of postoperative PVT. Preoperative and operative factors were compared, and the relationships between formation of PVT and its independent variables were analysed. In some cases, portal venous flow was measured before and after splenectomy using duplex Doppler ultrasonography.

Results

PVT developed after surgery in 17 (24 per cent) of 70 patients studied. Multivariable analysis showed that increased splenic vein diameter and low white cell count were significant independent risk factors for PVT. Portal venous flow after splenectomy was greatly reduced in the PVT group, but not in patients without PVT.

Conclusion

Large splenic vein diameter and low white cell count are independent risk factors for PVT after splenectomy in patients with cirrhosis and portal hypertension.

Post-transplant lymphoproliferative disorders in liver transplanted patients: a single-centre experience

Post-transplant lymphoproliferative disorder (PTLD) is a life-threatening complication after solid organ transplantation. Reduction of immunosuppression (RI) is accepted as a first step treatment with a long-term complete response rate observed in 23-50% of patients. Chemotherapy for diseases refractory to RI is based on small cohorts treated with different regimens. This paper reports on 10 consecutive cases of PTLD after liver transplantation. The median time from transplantation to PTLD diagnosis was 5 years. PTLD was frequently extranodal involving the transplanted liver. Seven monomorphic PTLD, 2 polymorphic and one Hodgkin disease were observed. Epstein Barr virus was present in tumour tissue only in one case. Initial therapy included RI in all patients. Chemotherapy was used in eight patients. No treatment-related mortality was observed and no patient developed graft rejection during chemotherapy. At a median follow-up period of 25 months, 6 of the 10 patients were alive and without evidence of disease.

Crystal structure of the first eubacterial Mre11 nuclease reveals novel features that may discriminate substrates during DNA repair

Mre11 nuclease plays a central role in the repair of cytotoxic and mutagenic DNA double-strand breaks. As X-ray structural information has been available only for the Pyrococcus furiosus enzyme (PfMre11), the conserved and variable features of this nuclease across the domains of life have not been experimentally defined. Our crystal structure and biochemical studies demonstrate that TM1635 from Thermotoga maritima, originally annotated as a putative nuclease, is an Mre11 endo/exonuclease (TmMre11) and the first such structure from eubacteria. TmMre11 and PfMre11 display similar overall structures, despite sequence identity in the twilight zone of only approximately 20%. However, they differ substantially in their DNA-specificity domains and in their dimeric organization. Residues in the nuclease domain are highly conserved, but those in the DNA-specificity domain are not. The structural differences likely affect how Mre11 from different organisms recognize and interact with single-stranded DNA, double-stranded DNA and DNA hairpin structures during DNA repair. The TmMre11 nuclease active site has no bound metal ions, but is conserved in sequence and structure with the exception of a histidine that is important in PfMre11 nuclease activity. Nevertheless, biochemical characterization confirms that TmMre11 possesses both endonuclease and exonuclease activities on single-stranded and double-stranded DNA substrates, respectively.

Liver transplantation for alcoholic liver disease in Europe: a study from the ELTR (European Liver Transplant Registry)

Alcohol-related liver disease (ALD) is one of the most common indications for liver transplantation (LT). Long-term outcome after LT for ALD versus other etiologies is still under debate. The aim of this study was to compare outcome after LT of patients with ALD, viral (VIR), and cryptogenic cirrhosis. Donor, graft and recipient ELTR variables were analysed in transplants for alcoholic and nonalcoholic cirrhosis (1988-2005) and were correlated with patient survival. Causes of death and/or graft failure were compared between groups. Nine thousand eight hundred eighty ALD, 10,943 VIR, 1478 ALD+VIR and 2410 cryptogenic (CRYP) liver transplants were evaluated. One, 3, 5 and 10 years graft survival rates after LT in ALD patients were 84%, 78%, 73%, 58%, significantly higher than in VIR and CRYP (p=0.04, p=0.05). By multivariate analysis, ALD+VIR (RR 1.14) and viral alone (RR 1.06) were significant risk factors for mortality. De novo tumors, cardiovascular and social causes were causes of death/graft failure in higher percentage in ALD groups versus other etiologies. LT for ALD cirrhosis has a favorable outcome, however, hepatitis C virus co-infection seems to eliminate this advantage. Screening for de novo tumors and prevention of cardiovascular complications are essential to provide better long-term results.

Liver transplantation for alcoholic liver disease in Europe: a study from the ELTR (European Liver Transplant Registry)

Alcohol-related liver disease (ALD) is one of the most common indications for liver transplantation (LT). Long-term outcome after LT for ALD versus other etiologies is still under debate. The aim of this study was to compare outcome after LT of patients with ALD, viral (VIR), and cryptogenic cirrhosis. Donor, graft and recipient ELTR variables were analysed in transplants for alcoholic and nonalcoholic cirrhosis (1988-2005) and were correlated with patient survival. Causes of death and/or graft failure were compared between groups. Nine thousand eight hundred eighty ALD, 10,943 VIR, 1478 ALD+VIR and 2410 cryptogenic (CRYP) liver transplants were evaluated. One, 3, 5 and 10 years graft survival rates after LT in ALD patients were 84%, 78%, 73%, 58%, significantly higher than in VIR and CRYP (p=0.04, p=0.05). By multivariate analysis, ALD+VIR (RR 1.14) and viral alone (RR 1.06) were significant risk factors for mortality. De novo tumors, cardiovascular and social causes were causes of death/graft failure in higher percentage in ALD groups versus other etiologies. LT for ALD cirrhosis has a favorable outcome, however, hepatitis C virus co-infection seems to eliminate this advantage. Screening for de novo tumors and prevention of cardiovascular complications are essential to provide better long-term results.

Liver transplantation for alcoholic liver disease in Europe: a study from the ELTR (European Liver Transplant Registry)

Alcohol-related liver disease (ALD) is one of the most common indications for liver transplantation (LT). Long-term outcome after LT for ALD versus other etiologies is still under debate. The aim of this study was to compare outcome after LT of patients with ALD, viral (VIR), and cryptogenic cirrhosis. Donor, graft and recipient ELTR variables were analysed in transplants for alcoholic and nonalcoholic cirrhosis (1988-2005) and were correlated with patient survival. Causes of death and/or graft failure were compared between groups. Nine thousand eight hundred eighty ALD, 10,943 VIR, 1478 ALD+VIR and 2410 cryptogenic (CRYP) liver transplants were evaluated. One, 3, 5 and 10 years graft survival rates after LT in ALD patients were 84%, 78%, 73%, 58%, significantly higher than in VIR and CRYP (p=0.04, p=0.05). By multivariate analysis, ALD+VIR (RR 1.14) and viral alone (RR 1.06) were significant risk factors for mortality. De novo tumors, cardiovascular and social causes were causes of death/graft failure in higher percentage in ALD groups versus other etiologies. LT for ALD cirrhosis has a favorable outcome, however, hepatitis C virus co-infection seems to eliminate this advantage. Screening for de novo tumors and prevention of cardiovascular complications are essential to provide better long-term results.

Liver transplantation for alcoholic liver disease in Europe: a study from the ELTR (European Liver Transplant Registry)

Alcohol-related liver disease (ALD) is one of the most common indications for liver transplantation (LT). Long-term outcome after LT for ALD versus other etiologies is still under debate. The aim of this study was to compare outcome after LT of patients with ALD, viral (VIR), and cryptogenic cirrhosis. Donor, graft and recipient ELTR variables were analysed in transplants for alcoholic and nonalcoholic cirrhosis (1988-2005) and were correlated with patient survival. Causes of death and/or graft failure were compared between groups. Nine thousand eight hundred eighty ALD, 10,943 VIR, 1478 ALD+VIR and 2410 cryptogenic (CRYP) liver transplants were evaluated. One, 3, 5 and 10 years graft survival rates after LT in ALD patients were 84%, 78%, 73%, 58%, significantly higher than in VIR and CRYP (p=0.04, p=0.05). By multivariate analysis, ALD+VIR (RR 1.14) and viral alone (RR 1.06) were significant risk factors for mortality. De novo tumors, cardiovascular and social causes were causes of death/graft failure in higher percentage in ALD groups versus other etiologies. LT for ALD cirrhosis has a favorable outcome, however, hepatitis C virus co-infection seems to eliminate this advantage. Screening for de novo tumors and prevention of cardiovascular complications are essential to provide better long-term results.

The impact of hepatitis C and biliary complications on patient and graft survival following liver transplantation

Recurrent hepatitis C (HCV) and biliary complications (BC) are major causes of post liver transplant morbidity and mortality. The impact of these complications may be additive or synergistic. We performed a retrospective cohort study to analyze the effects of HCV and BC on all patients transplanted at two institutions over 6 years. BC was defined by imaging findings in the setting of abnormal liver function tests that required intervention. The primary outcomes were graft and patient survival over a mean 3.4 years. 709 patients (619 deceased, 90 living donor) were included, 337 with HCV and 372 without. BC was diagnosed more frequently in patients with HCV, 26% versus 18% (p = 0.008). One-year and overall patient and graft survival were significantly lower in patients with HCV, but BC impacted only 1-year graft survival. The combination of BC and HCV had no additional impact on survival or fibrosis rates on 1-year protocol biopsies. Multivariate analysis revealed HCV (HR 2.1) and HCC (HR 1.9) to be independent predictors of mortality. Since BC are diagnosed more frequently in HCV patients and only affect early graft loss, it is likely that recurrent HCV rather than BC accounts for the majority of adverse graft outcomes.

Crystal structure of a novel Sm-like protein of putative cyanophage origin at 2.60 A resolution

ECX21941 represents a very large family (over 600 members) of novel, ocean metagenome-specific proteins identified by clustering of the dataset from the Global Ocean Sampling expedition. The crystal structure of ECX21941 reveals unexpected similarity to Sm/LSm proteins, which are important RNA-binding proteins, despite no detectable sequence similarity. The ECX21941 protein assembles as a homopentamer in solution and in the crystal structure when expressed in Escherichia coli and represents the first pentameric structure for this Sm/LSm family of proteins, although the actual oligomeric form in vivo is currently not known. The genomic neighborhood analysis of ECX21941 and its homologs combined with sequence similarity searches suggest a cyanophage origin for this protein. The specific functions of members of this family are unknown, but our structure analysis of ECX21941 indicates nucleic acid-binding capabilities and suggests a role in RNA and/or DNA processing.

Crystal structure of histidine phosphotransfer protein ShpA, an essential regulator of stalk biogenesis in Caulobacter crescentus

Cell-cycle-regulated stalk biogenesis in Caulobacter crescentus is controlled by a multistep phosphorelay system consisting of the hybrid histidine kinase ShkA, the histidine phosphotransfer (HPt) protein ShpA, and the response regulator TacA. ShpA shuttles phosphoryl groups between ShkA and TacA. When phosphorylated, TacA triggers a downstream transcription cascade for stalk synthesis in an RpoN-dependent manner. The crystal structure of ShpA was determined to 1.52 A resolution. ShpA belongs to a family of monomeric HPt proteins that feature a highly conserved four-helix bundle. The phosphorylatable histidine His56 is located on the surface of the helix bundle and is fully solvent exposed. One end of the four-helix bundle in ShpA is shorter compared with other characterized HPt proteins, whereas the face that potentially interacts with the response regulators is structurally conserved. Similarities of the interaction surface around the phosphorylation site suggest that ShpA is likely to share a common mechanism for molecular recognition and phosphotransfer with yeast phosphotransfer protein YPD1 despite their low overall sequence similarity.