PubMed Health⌕ Search

Biomedical subjects

Fernando Alvarez

Publications and source records attributed to Fernando Alvarez.

At least 19 recordsLinked to original sources
PubMed2006

HLA class II influences humoral autoimmunity in patients with type 2 autoimmune hepatitis.

BACKGROUND/AIMS: Type 2 autoimmune hepatitis (AIH) is characterized by the presence of anti-liver kidney microsome (anti-LKM-1) and/or anti-liver cytosol type 1 (anti-LC1) autoantibodies. However, the correlation between these autoantibodies and the genetic background has not been studied. METHODS: Frequencies of HLA class II alleles were compared between the 60 Caucasian children with type 2 AIH and 313 control subjects. The anti-LKM1 antibody reactivity directed against antigenic sites of CYP2D6 was analysed by ELISA. RESULTS: HLA-DQB1 *0201 allele was found to be the primary genetic determinant of susceptibility to type 2 AIH by conferring the highest odd-ratio (OR = 6.4). HLA-DRB1 *03 allele was significantly increased (P < 0.0001) among patients with both anti-LKM1 and anti-LC1 autoantibodies as well as in those with only anti-LC1(+) compared to those with anti-LKM1(+) alone. In contrast, HLA-DRB1 *07 allele was significantly associated (P < 0.0001) with anti-LKM1(+) alone compared to groups with both anti-LKM and anti-LC1 or with LC1+ alone. Children with the DRB1 *07 allele develop anti-LKM1 autoantibodies having a more restricted specificity (2 epitopes) than to those having HLA-DRB1 *03 allele (5 epitopes). CONCLUSIONS: The HLA-DR locus is involved in autoantibody expression, while the DQ locus appears to be a critical determinant for the development of type 2 AIH.

Adolescent↗
PubMed2006

Study of a novel hypervariable region in hepatitis C virus (HCV) E2 envelope glycoprotein.

A large share of hepatitis C virus amino acid sequence variation is concentrated within two hypervariable regions located at the N-terminus of the E2 envelope glycoprotein (HVR1 and HVR2). Interhost and intrahost comparison of 391 E2 sequences derived from 17 subjects infected with HCV using amino acid entropy revealed clustering of amino acid variability at a third site (residues 431-466), which was termed HVR3. Genetic distance analysis supported the division of HVR3 into three subdomains (HVR3a, HVR3b, and HVR3c). Study of synonymous and nonsynonymous nucleic acid substitutions confirmed that HVR3a was subjected to strong intrahost-selective pressure. Physicochemical and antigenicity predictions, conservation of key residues, and molecular modeling were concordant with one another and further validated the proposed organization of HVR3. Taken together, these results are suggestive of a role for HVR3 in cell surface receptor binding and viral entry akin to that proposed for HVR1 and HVR2.

Base Sequence↗
PubMed2006

Normal glomerular filtration rate in long-term follow-up of children after orthotopic liver transplantation.

BACKGROUND: Cyclosporine A (CyA) and tacrolimus are the principal immunosuppressive agents used for OLT in children. However, progressive deterioration of renal function from calcineurin inhibitor toxicity after OLT has been widely reported. The aim of this study was to assess long-term renal function in children after OLT. METHODS: We reviewed all OLT patients surviving >1 year at Sainte Justine Hospital from 1987 to 2003. The GFR (ml/min/1.73 m) was measured yearly by the Tc-99m DTPA single injection technique RESULTS: In all, 101 OLT patients (27 tyrosinemia, 33 biliary atresia, 5 fulminant hepatic failure, 36 miscellaneous) were studied. Median age at OLT was 35 months (range 6-178 months) in tyrosinemia group and 58 months (range 1-226 months) in the "Others" (P = NS), median pediatric end-stage liver disease score was respectively 3 (range -9 to 21) and 15 (-9 to 35), (P=0.001), and median follow-up was 6 (range 1-14) and 6 (range 1-17) (P = NS) years, respectively. Median annual GFR values in tyrosinemia fluctuated between 61 and 104 ml/min/1.73 m, with an improving tendency, and 94-121 ml/min/1.73 m in the Others. GFR did not differ on CyA vs. tacrolimus treatment. The median duration of therapy with calcium-channel blocker in the tyrosinemia group was 5 (1-13) vs. 2 (1-13) years in the Others. CONCLUSIONS: Median GFR remained normal in most nontyrosinemia patients (Others). Tyrosinemia patients remained stable at a lower GFR. CyA administration in three daily doses and prolonged calcium-channel blocker therapy may have contributed to this stability. Impairment of kidney function was associated with congenital kidney disease, toxic kidney injury, and portal hypertension.

Adolescent↗
PubMed2006

Autoimmune hepatitis and primary sclerosing cholangitis.

Autoimmune liver disease in children presents predominantly as autoimmune hepatitis (AIH) and primary sclerosing cholangitis (PSC). These diagnoses must be considered in patients who have acute and chronic hepatitis, particularly when an extrahepatic autoimmune disorder is present. In AIH, the timely and sustained control of liver inflammation is critical to improve the short- and long-term outcomes. No effective treatment for PSC has been identified to date, but supportive care, careful attention to complications and associated nonhepatic diseases, and liver transplantation significantly improve the long-term outcome.

Adolescent↗
PubMed2006

Follow-up of children with autoimmune hepatitis treated with cyclosporine.

OBJECTIVES: To evaluate the effectiveness of cyclosporine in inducing and maintaining remission of the inflammatory process in autoimmune hepatitis, when used in combination with low doses of prednisone and azathioprine and to identify the prognostic factors associated with sustained remission. METHODS: Eighty-four patients with autoimmune hepatitis were consecutively recruited from 5 centers between January 1994 and March 2001. Cyclosporine was administered during the first 6 months. Thereafter, in patients with aminotransferase levels of lower than twice the normal values, prednisone and azathioprine were initiated. RESULTS: Normal aminotransferase levels were observed in 94.05% (79/84) of the patients, 72% of them within the first 6 months of treatment. Total serum bilirubin level of greater than 1.2 mg/dL and portal hypertension at diagnosis jointly predicted a significant delay in remission. Adverse effects related to cyclosporine remained mild and transient. Low doses of prednisone and standard doses of azathioprine were not implicated in relapse of the disease during the follow-up of any patient. CONCLUSIONS: This protocol allowed control of the liver inflammatory process and was well tolerated. The response to this immunosuppressive therapy can be predicted with accuracy. Factors delaying remission can be identified early at diagnosis and may contribute to the development of more effective treatment policies for this condition.

Adolescent↗
PubMed2006

Hepatocyte transplantation in the Long Evans Cinnamon rat model of Wilson's disease.

Wilson's disease (WD), caused by a mutation in the P-type copper transporting ATPase (Atp7b) gene, results in excessive accumulation of copper in the liver. Long Evans Cinnamon rats (LEC) bear a mutation in the atp7b gene and share clinical characteristics of human WD. To explore hepatocyte transplantation (HT) as therapy for metabolic liver diseases, 8-week-old LEC rats (n = 12) were transplanted by intrasplenic injection of hepatocytes from donor Long Evans (LE) rats. Immunosuppression was maintained with intraperitoneal tacrolimus. The success of HT was monitored at 24 weeks of life. Serum aminotransferases and bilirubin peaked at 14-21 weeks in both HT rats and nontransplanted controls, but at 24 weeks, survival was 97% in LEC-HT versus 63% in controls. All transplanted rats showed restored biliary copper excretion and reduced liver iron concentration associated with increased ceruloplasmin oxidase activity. Liver tissue expressed atp7b mRNA (11.9 +/- 13.6%) indicative of engraftment of normal cells in 7 of 12 HT rats, associated with a reduced liver copper concentration compared to untreated LEC rats. Periportal islets of normal appearing hepatocytes, recognized by atp7b antibody, were observed in transplanted livers while lobular host cells showed persistent pleomorphic changes and inflammatory infiltrates. In conclusion, transplantation of normal hepatocytes prevented fulminant hepatitis, reduces chronic inflammation, and improved 6-month survival in LEC rats. Engraftment of transplanted cells, which express atp7b mRNA, repopulated the recipient liver with normal functional capacity.

Adenosine Triphosphatases↗
PubMed2005

Type 2 autoimmune hepatitis murine model: the influence of genetic background in disease development.

Genetic predisposition is recognized as an important factor for the development of autoimmune hepatitis (AIH). To assess the potential contribution of MHC and non-MHC genes, type 2 AIH was reproduced in three mice strains, taking advantage of their different genetic makeup with regard to MHC and non-MHC genes. Mice (C57BL/6, 129/Sv and BALB/c) were DNA vaccinated with a pCMV-CTLA4-CYP2D6-FTCD plasmid coding for the extracellular region of CTLA-4 and for the antigenic region of the CYP2D6 and FTCD, and with pCMV-IL12. ALT and total IgG levels, liver histology, FACS analysis and liver T-cell cytotoxicity assays were monitored up to 8 months post-injection. C57BL/6 mice showed elevated serum ALT levels, autoantibodies, antigen-specific cytotoxic T-cells and lobular and periportal inflammatory infiltrate. The 129/Sv mice showed slightly elevated ALT levels, sparse liver lobular infiltrate and cytotoxic T-cells. The BALB/c mice showed no liver inflammation. All mice had elevated total serum IgG levels. This murine model of type 2 AIH shows that MHC and non-MHC genes contribute to the susceptibility to autoimmune hepatitis. The understanding of the genetic determinants implicated in AIH development will be a major advance in the study of its pathogenesis and could lead to a better diagnostic approach and preventive strategies.

Alanine Transaminase↗
PubMed2005

LKM1 autoantibodies in chronic hepatitis C infection: a case of molecular mimicry?

Anti-liver-kidney microsome type 1 (LKM1) autoantibodies directed against the cytochrome P450 2D6 (CYP2D6) are considered specific markers of type 2 autoimmune hepatitis, but are also found in 5% of sera from patients chronically infected by hepatitis C virus (HCV). Molecular mimicry between HCV proteins and CYP2D6 has been proposed to explain the emergence of these autoantibodies. Anti-LKM1 autoantibodies from hepatitis C-infected patients were affinity-purified against immobilized CYP2D6 protein and used to screen a phage display library. CYP2D6 conformational epitopes were identified using phage display analysis and the identification of statistically significant pairs (SSPs). Cross-reactivity between CYP2D6 and HCV protein candidates was tested by immunoprecipitation. Nineteen different clones were isolated, and their sequencing resulted in the mapping of a conformational epitope to the region of amino acids 254-288 of CYP2D6. Candidate HCV proteins for molecular mimicry included: core, E2, NS3 and NS5a. Affinity-purified autoantibodies from HCV+/LKM1+ patients immunoprecipitated either NS3, NS5a, or both, and these reactivities were specifically inhibited by immobilized CYP2D6. In conclusion, HCV+/LKM1+ sera recognize a specific conformational epitope on CYP2D6 between amino acids 254 to 288, the region that contains the major linear epitope in type 2 autoimmune hepatitis patients. Cross-reactivity due to molecular mimicry at the B-cell level was shown between the CYP2D6 and the HCV NS3 and NS5a proteins and could explain the presence of anti-LKM1 in patients chronically infected with HCV. Further investigation of the role played by this molecular mimicry in HCV-infected patients may lead to more specific strategies for diagnosis and treatment.

Amino Acid Sequence↗
PubMed2005

Neonatal cholestasis associated with fetal arrhythmia.

We evaluated the consequence of different types of fetal arrhythmia in the development of neonatal cholestasis. The charts of 38 children born at St. Justine Hospital between 1993 and 2001 with sustained and hemodynamically significant fetal arrhythmias were studied: 19 with supraventricular tachycardia, 14 with atrial flutter, and 5 with atrio-ventricular (AV) block. Six of these 38 children presented with cholestasis. The average duration of arrhythmia was 15.7 days in the noncholestatic group, compared with 40.3 days in the cholestatic group ( P <.05). The three infants with supraventricular tachycardia who developed cholestasis survived and resolved their cholestasis, whereas 2 of 3 infants with AV block died. No infant with atrial flutter developed cholestasis. We conclude that newborns who developed tachyarrhythmia during their fetal life can show transient neonatal cholestasis. In patients with AV block, severe and irreversible liver failure could be observed. In addition, extensive collapse of the stroma and the absence of hepatocytes (foie vide) also were observed in a patient with anti-Ro antibodies.

Arrhythmias, Cardiac↗
PubMed2005

Ascites after orthotopic liver transplantation in children.

Ascites is a poorly understood postoperative complication of orthotopic liver transplantation (OLT). It is associated with additional morbidity and can prolong hospitalization considerably. The incidence, the factors predictive of occurrence and the etiology of this complication are not known. The charts of 118 patients with 138 OLT were analyzed according to the following criteria: ascites lasting longer than the first 10 postoperative days, assessed by loss of ascitic fluid through drainage tubes, surgical wounds or paracentesis, with a peak volume of > or =10 mL/kg/day. Patients were divided into three groups: Group 1, no ascites; Group 2, ascites associated with postoperative complications, including chylus ascites; and Group 3, ascites not associated with postoperative complications. Postoperative ascites occurred in 43 of 138 OLT (31.2%). Patients with biliary atresia, preoperative portal hypertension, postoperative pleural effusion or at retransplantation had ascites significantly more often. In 32 of 138 (23.2%) OLT, ascites was associated with postoperative complications, including thrombosis, abdominal infections, intestinal perforation, biliary leak, pancreatitis, and chylus ascites. In 11 of 138 (7.9%) OLT, ascites was the only postoperative complication (group 3). Group three patients were significantly older, and had lower preoperative platelet counts and preoperative ascites more often than group 1 patients. The primary liver diseases were mainly cystic fibrosis of the pancreas, congenital hepatic fibrosis, and North American Indian childhood cirrhosis. The serum-ascites albumin gradient suggested a hepatic origin of ascites. Postoperative ascites is associated with the duration and degree of preoperative portal hypertension. We speculate that the mechanism involved includes a disproportion between venous blood volume and liver uptake capacity of the donor organ.

Ascites↗
PubMed2005

Reduced bile flow associated with parenteral nutrition is independent of oxidant load and parenteral multivitamins.

BACKGROUND: Reduction in bile flow is a characteristic of cholestasis related to parenteral nutrition. Light exposure of parenteral multivitamin preparations is the major source of peroxides contaminating parenteral nutrition solutions. They may contribute to local oxidative stress. Oxidants are reported to affect transport mechanisms across the hepatocyte membrane into bile. The authors hypothesize that an oxidant-antioxidant imbalance is involved in parenteral nutrition related cholestasis. The aim of this study was to investigate the roles of multivitamin preparations and peroxides on bile flow in newborn guinea pigs receiving parenteral nutrition. METHODS: Three-day-old guinea pigs were fed enterally or parenterally with solutions containing 8% dextrose/0.45% NaCl +/- multivitamin preparation +/- amino acids +/- lipids. The influence of the oxidant-antioxidant balance on bile flow was evaluated using 500 microM hydrogen peroxide and 1% and 3% multivitamin preparations +/- Na metabisulfite. Four days later, animals were anesthetized and bile flow was recorded over 2 hours. Glutathione determinations were performed on bile and liver samples. The percentage of oxidized glutathione, reflecting the redox status, was used as a marker of oxidative stress. Data were compared by analysis of variance with P < 0.05. RESULTS: Bile flow decreased first on initiating dextrose + NaCl infusion (a 25% decrease) and subsequently by adding amino acids (a further 30% decrease). Although antioxidant vitamins and peroxides modified the hepatic redox status, they did not influence bile flow. CONCLUSION: Although the composition of parenteral nutrition affects bile flow and the hepatic redox status, the oxidant-antioxidant imbalance in infused solutions is not the causal event in the installation of cholestasis.

Analysis of Variance↗
PubMed2004

Role of NK and NKT cells in the immunopathogenesis of HCV-induced hepatitis.

Natural killer (NK) cells constitute the first line of host defense against invading pathogens. They usually become activated in an early phase of a viral infection. Liver is particularly enriched in NK cells, which are activated by hepatotropic viruses such as hepatitis C virus (HCV). The activated NK cells play an essential role in recruiting virus-specific T cells and in inducing antiviral immunity in liver. They also eliminate virus-infected hepatocytes directly by cytolytic mechanisms and indirectly by secreting cytokines, which induce an antiviral state in host cells. Therefore, optimally activated NK cells are important in limiting viral replication in this organ. This notion is supported by the observations that interferon treatment is effective in HCV-infected persons in whom it increases NK cell activity. Not surprisingly, HCV has evolved multiple strategies to counter host's NK cell response. Compromised NK cell functions have been reported in chronic HCV-infected individuals. It is ironic that activated NK cells may also contribute toward liver injury. Further studies are needed to understand the role of these cells in host defense and in liver pathology in HCV infections. Recent advances in understanding NK cell biology have opened new avenues for boosting innate and adaptive antiviral immune responses in HCV-infected individuals.

Animals↗
PubMed2004

Characterization of the antigenicity of the formiminotransferase-cyclodeaminase in type 2 autoimmune hepatitis.

Human formiminotransferase-cyclodeaminase (hFTCD) is the autoantigen recognized by anti-liver cytosol type 1 (LC1) autoantibodies in type 2 autoimmune hepatitis (AIH) patients. In rats, this octameric protein is localized on the Golgi apparatus and binds brain microtubules (MTs) and vimentin. Subcellular localization of human formiminotransferase-cyclodeaminase and its implication in the pathogenesis of autoimmune hepatitis are unknown. Localization of the human formiminotransferase-cyclodeaminase in human hepatocytes was done using indirect immunofluorescence and subcellular fractionations followed by in vitro binding techniques. The formiminotransferase-cyclodeaminase antigen at two distinct locations in hepatocytes, free in the cytosol and associated with the Golgi membranes are recognized by anti-liver cytosol type 1 autoantibodies. The human formiminotransferase-cyclodeaminase binds reversibly to the Golgi membranes and this complex formation is increased by anti-liver cytosol type 1 autoantibodies. Finally, human formiminotransferase-cyclodeaminase does not interact with liver-specific cytoskeleton proteins. Anti-liver cytosol type 1 autoantibodies are directed against the mature high molecular form of human formiminotransferase-cyclodeaminase. Therefore, the subcellular location of the protein may influence the production of autoantibodies and their role in the pathogenesis of type 2 autoimmune hepatitis. This antigen-driven response does not appear to be facilitated or enhanced by a possible interaction between human formiminotransferase-cyclodeaminase and hepatocyte cytoskeleton proteins.

Ammonia-Lyases↗
PubMed2004

A murine model of type 2 autoimmune hepatitis: Xenoimmunization with human antigens.

Autoimmune hepatitis (AIH) is characterized by an immune-mediated injury of the hepatic parenchyma of unknown pathogenesis. Type 2 AIH is identified by the presence of anti-liver-kidney microsomes type 1 (anti-LKM1) and anti-liver cytosol type 1 (anti-LC1) autoantibodies. The current study shows that a murine model of AIH can be generated by DNA immunization against type 2 AIH self-antigens (P450 2D6 and formiminotransferase-cyclodeaminase). A pCMV plasmid containing the N-terminal region of mouse CTLA-4 and the antigenic region of human CYP2D6 (672-1,377 bp) and human formiminotransferase cyclodeaminase (FTCD; 1,232-1,668 bp) was used for DNA immunization of C57BL/6 female mice. Immunized mice showed elevated levels of alanine aminotransferase (ALT), with peaks at 4 and 7 months postinjection. Periportal, portal, and intralobular liver inflammatory infiltrates were observed at histology. Mainly CD4+ lymphocytes, but also CD8+ and B lymphocytes, were found in the liver. Cytotoxic-specific T cells were found in both the liver and spleen of these animals. Mice developed anti-LKM1 and anti-LC1 antibodies of immunoglobulin G2 (IgG2) subclass, against specific mouse autoantigens. The ALT levels correlated with both the presence of anti-LKM1/anti-LC1 antibodies and the presence of liver necroinflammation. In conclusion, in mice, DNA immunization against human autoantigens breaks tolerance and induces an autoimmune liver disease. Molecular mimicry between foreign and self-antigens explains the liver injury. This model of AIH resembles human type 2 AIH and will be helpful for the study of its pathogenesis.

Animals↗