Chronic hepatitis B virus (HBV) infection in children: 25 years' experience.

Whereas e-seroconversion represents the loss of hepatitis B e-antigen (HBeAg) followed by gain of antibody to HBeAg (anti-HBe), 'inactive chronic infection' extends this concept to include e-seroconversion with decreased serum viral load and biochemical remission. These events must be well-characterized before treatment outcomes can be evaluated. We examined the rates of e-seroconversion and achievement of inactive chronic infection among children with chronic HBV infection. Children who were HBsAg positive >6 months were identified retrospectively between 1983 and 2008 from the Hospital for Sick Children Liver Clinic. Inactive chronic infection was defined as loss of HBeAg, serum ALT ≤40 IU/mL, and HBV DNA <10(6 ) IU/mL. Both e-seroconversion and achievement of inactive chronic infection were characterized using survival analysis. The effect of transmission route, treatment, age at diagnosis, ethnicity, gender and baseline ALT on these rates was evaluated with univariate and multiple regression. Of 252 HBeAg-positive cases, 59.9% had HBV-infected mothers, 77% were Asian, and 33 received interferon-α. Untreated children were younger at last follow-up (mean 14.5 vs 17.6 years), had lower ALT (median 60 vs 116 IU/mL) and had shorter follow-up (6.6 vs 9.1 years, all P < 0.002) compared to treated children. Crude e-seroconversion rate was 41.7% over 0.5-19.1 years of follow-up, and this was not affected by transmission route (P = 0.93), gender (P = 0.62) nor treatment (P = 0.08). 49% achieved inactive chronic infection by age 19 years. Being non-Asian, age at diagnosis<3 years, and ALT ≥40 IU/mL were associated with a higher rate of e-seroconversion and achieving inactive chronic infection (P < 0.0001). Almost 50% of children achieved inactive chronic infection by early adulthood.

The changing face of hepatitis in boys with haemophilia associated with increased prevalence of obesity.

Hepatitis in children with haemophilia was historically most often associated with transfusion-transmitted infections. However, with the use of recombinant clotting factor concentrates, acquisition of such infections has now become rare. We studied the profile of hepatitis in North-American children with haemophilia in the modern era of safe blood products and excess childhood obesity. A total of 173 boys (<18 years) registered in the Pediatric Comprehensive Care Haemophilia Program were included in this retrospective study. Hospital records were reviewed for baseline data, serial height and weight measurements and serial alanine aminotransferase (ALT) levels. A body mass index (BMI) ranking was available for 170 boys, of whom 25 (14.7%, 95% CI 9.7-20.9%) were obese. The rate of obesity was higher in severe haemophilic boys. Compared with the general childhood population, the rate of obesity trended towards being higher in young haemophilic boys (2-5 years), but was similar in other age groups. A persistently high ALT (≥80 U L(-1) ) was documented in 5 boys and was associated with obesity. Three boys had clinical and imaging studies compatible with non-alcoholic fatty liver disease (NAFLD). Overweight and obesity are common among haemophilic boys, especially those who are younger and with severe disease. In this large group of haemophilic boys, chronic viral hepatitis was rare and NAFLD was a more common cause of liver disease. Overweight and obese haemophilic boys should be evaluated for NAFLD and interventional programmes should be designed to reduce the potential complications associated with obesity.

Dietary and physical activity patterns in children with fatty liver.

BACKGROUND/OBJECTIVES: To examine lifestyle patterns (diet, physical activity, energy expenditure) and metabolic variables (insulin resistance, oxidative stress, inflammation) in children with fatty liver detected by sonography. SUBJECTS/METHODS: Body composition (fat-free mass, body mass index-z), waist circumference (WC), dietary intake and energy expenditure were determined in 38 patients (ages 5-19 years) with fatty liver in whom specific causative liver disorders had been excluded. Laboratory investigations included liver biochemistries, C-reactive protein, tumor necrosis factor-alpha, glutathione peroxidase, vitamin E, and erythrocyte-glutathione. RESULTS: In all, 36 of 38 children were overweight/obese; 37 had WC indicative of abdominal obesity. They displayed fasting hyperinsulinemia (n=15), hypertriglyceridemia (n=14), and hypoadiponectinemia (5.5+/-1.9 s.d. microg/ml; n=23) and insulin resistance (homeostasis model of insulin resistance (HOMA-IR)>3; n=21). Alanine aminotransferase (ALT) was elevated in 28 (43-556 U/l; median=56). Some inflammatory markers were elevated, whereas antioxidants were decreased. Diet was characterized by high saturated-, low polyunsaturated-fat, high fructose and sucrose intakes. Fructose intake was independently associated with insulin resistance and decreased serum adiponectin, regardless of serum ALT (P<0.05). Low and subnormal intakes of omega-3 fatty acids (C20:5 (n-3) and C22:6 (n-3)) were associated with abnormal serum ALT (P=0.006) and elevated HOMA-IR (P=0.01). Findings were similar in children 11 years old. Physical activity was low in both age groups. CONCLUSIONS: Children with fatty liver detected sonographically have metabolic features of non-alcoholic fatty liver disease. Their diets are high in fructose and low in polyunsaturated fatty acid. Their activity patterns are sedentary. These lifestyle features may contribute to liver damage and can be a focus for therapeutic intervention.

Spontaneous clearance of childhood hepatitis C virus infection.

To describe the spontaneous clearance rate of childhood hepatitis C virus (HCV) infection, to determine whether route of transmission affects the clearance rate and to identify other predictors of clearance. Children with chronic hepatitis C were identified between 1990 and 2001. The rate of spontaneous clearance (defined as >or=2 positive anti-HCV antibody test but negative HCV RNA) was calculated using survival analysis. Univariate and multivariate predictor variables [route of transmission, age at infection, age at last follow-up, alanine aminotransferase (ALT) and gender] for clearance were evaluated. Of 157 patients, 28% of children cleared infection (34 transfusional and 10 nontransfusional cases). The 123 transfusional cases were older at time of infection and at follow-up, compared with the 34 nontransfusional cases. Younger age at follow-up (p < 0.0001) and normal ALT levels (p < 0.0001) favoured clearance. Among cases of neonatal infection, 25% demonstrated spontaneous clearance by 7.3 years. The rate of spontaneous clearance of childhood HCV infection was comparable between transfusional and nontransfusional cases. If clearance occurs, it tends to occur early in infection, at a younger age.

In vitro assessment of copper-induced toxicity in the human hepatoma line, Hep G2.

Copper, though essential, is highly toxic when present in excess, as in Wilson disease, a genetic disorder of hepatic copper metabolism. We hypothesized that mitochondria are a major target of copper-induced cytotoxicity in Wilson disease. We used the human hepatoma line Hep G2 to examine copper-mediated cytotoxicity and three different methods to assess organelle damage: MTT assay (mitochondria), neutral red (NR; lysosomes) and Trypan blue exclusion assay (TB; plasma membrane). For all assays, cells at approximately 60% confluence in microtitre plates were incubated with CuCl(2) (concentration range: 50-100-150-200 microM) for 24 or 48 h. Results were expressed as percent of untreated control. At 24 h, cytotoxicity as detected by NR assay was significantly higher at all concentrations of copper than for MTT or TB ( p<0.005 at all concentrations). Cytotoxicity as detected by MTT was higher than that detected by TB at all concentrations except at 200 microM (p<0.05 for 50 microM, p<0.005 for 100 microM, p = 0.001 for 150 microM). Results at 48 h were similar (NR versus others: p <0.001 MTT versus TB: NS except at 150 microM where p<0.01). We investigated reactive oxygen species (ROS) production in copper-associated hepatocytoxicity by incubating sub-confluent cells with 2('),7(')-dichlorodihydrofluorescein diacetate dye plus copper (concentration range: 0-200 microM) for 1-1.5 h. Copper, but not zinc, produced significant increases in ROS (p<0.001). In summary, Hep G2 lysosomes appeared more susceptible to Cu-mediated damage than mitochondria; the cell membrane was highly resistant to damage.

Wild-type nonneuronal cells extend survival of SOD1 mutant motor neurons in ALS mice.

The most common inherited [correct] form of amyotrophic lateral sclerosis (ALS), a neurodegenerative disease affecting adult motor neurons, is caused by dominant mutations in the ubiquitously expressed Cu-Zn superoxide dismutase (SOD1). In chimeric mice that are mixtures of normal and SOD1 mutant-expressing cells, toxicity to motor neurons is shown to require damage from mutant SOD1 acting within nonneuronal cells. Normal motor neurons in SOD1 mutant chimeras develop aspects of ALS pathology. Most important, nonneuronal cells that do not express mutant SOD1 delay degeneration and significantly extend survival of mutant-expressing motor neurons.

Histological improvement with lamivudine therapy for de novo hepatitis B occurring in an anti-HBs-positive child after bone marrow transplantation.

We describe a 14-year-old bone marrow transplant recipient who was anti-HBs-positive before the procedure and afterwards developed acute infection with hepatitis B virus (HBV). Liver biopsies taken while symptomatic showed portal fibrosis progressing to cirrhosis. The patient responded to lamivudine treatment with HBeAg seroconversion and significant regression of fibrosis. Although the source and timing of HBV exposure remain unclear, the potential for severe hepatitis B infection following bone marrow transplant warrants caution. This case demonstrates that a symptomatic HBV infection can occur in an immunocompromised patient who had originally been anti-HBs-positive.

Kinesin-mediated axonal transport of a membrane compartment containing beta-secretase and presenilin-1 requires APP.

Proteolytic processing of amyloid precursor protein (APP) generates amyloid-beta peptide and has been implicated in the pathogenesis of Alzheimer's disease. However, the normal function of APP, whether this function is related to the proteolytic processing of APP, and where this processing takes place in neurons in vivo remain unknown. We have previously shown that the axonal transport of APP in neurons is mediated by the direct binding of APP to the kinesin light chain subunit of kinesin-I, a microtubule motor protein. Here we identify an axonal membrane compartment that contains APP, beta-secretase and presenilin-1. The fast anterograde axonal transport of this compartment is mediated by APP and kinesin-I. Proteolytic processing of APP can occur in the compartment in vitro and in vivo in axons. This proteolysis generates amyloid-beta and a carboxy-terminal fragment of APP, and liberates kinesin-I from the membrane. These results suggest that APP functions as a kinesin-I membrane receptor, mediating the axonal transport of beta-secretase and presenilin-1, and that processing of APP to amyloid-beta by secretases can occur in an axonal membrane compartment transported by kinesin-I.

Detailed characterization of experimentally derived human hepatic CYP1A1 activity and expression using differential inhibition of ethoxyresorufin O-deethylation by fluvoxamine.

OBJECTIVE: To characterize the distribution of mathematically derived human hepatic CYP1A1 activity using differential inhibition of ethoxyresorufin O-deethylation (EROD) by fluvoxamine. METHODS: Quantitative CYP1A1- and CYP1A2-mediated EROD activities were determined in 42 human livers using differential inhibition of EROD by fluvoxamine. CYP1A2-specific activity was also measured by phenacetin O-deethylation and caffeine 3-demethylation. Distributions of CYP1A1-mediated EROD and CYP1-A2 probe activities were analyzed using cumulative distribution (probit) plots and the Kolgomorov-Smirnov test. Age effect on CYP1A1- and CYP1A2-mediated EROD activities was evaluated using descriptive statistics and analysis of variance. RESULTS: The derived CYP1A1 protein concentration of 0.58 +/- 1.04 pmol/mg was only 4% of the derived CYP1A2. Since CYP1A1 is intrinsically far more active than CYP1A2 in mediating EROD, contribution of CYP1A1 to EROD represented approximately 25-40% of CYP1A2 contribution. Three of the 42 livers exhibited no CYP1A1-mediated EROD. Approximately 8% of the individuals showed high CYP1A1 activity phenotype based on cumulative distribution curve analysis. Hepatic CYP1A1 activity was more variable than that of CYP1A2. The variance of CYP1A1-mediated EROD was significantly different from that of CYP1A2, using the Kolgomorov-Smirnov statistical test. Even though not statistically significant, an age-related pattern in CYP1A1-mediated activity was identified: activity was high in the pre-puberty group, then decreased in the young/mature adult group and, finally, a slight increase was observed in old age. CONCLUSIONS: Distribution pattern in CYP1A1-mediated EROD suggests that the low derived CYP1A1 expression is most likely induced rather than constitutive. CYP1A1 activity deviates from log-normal distribution; the variations in hepatic CYP1A1 activity may affect the conversion of procarcinogens to carcinogens. The age-related trend in CYP1A1-mediated EROD activity hints that CYP1A1 responsiveness to inducers may change with age as well as with exposure to environmental inducers. These findings prompt (1) future genotyping studies to determine whether increased CYP1A1 inducibility is a result of genetic factors and (2) studies to address whether CYP1A1 inducibility changes with age.

Liver failure with marked hyperferritinemia: 'ironing out' the diagnosis.

Hemophagocytic lymphohistiocytosis (HLH) may manifest as neonatal liver failure characterized by hepatosplenomegaly, profound coagulopathy, ascites and hyperbilirubinemia. Marked hyperferritinemia may be present in these patients, mimicking perinatal hemochromatosis. Tissue specimens are critical in distinguishing these two diseases and in directing management. Clinical recognition and diagnosis of HLH can be difficult but are crucial for appropriate therapy and genetic counselling. Liver transplantation is absolutely contraindicated for patients with HLH but may be the only life-saving treatment modality for patients with perinatal hemochromatosis.

Functional analysis of mouse kinesin motor Kif3C.

Members of the kinesin II family are thought to play essential roles in many types of intracellular transport. One distinguishing feature of kinesin II is that it generally contains two different motor subunits from the Kif3 family. Three Kif3 family members (Kif3A, Kif3B, and Kif3C) have been identified and characterized in mice. Intracellular localization and biochemical studies previously suggested that Kif3C is an anterograde motor involved in anterograde axonal transport. To understand the in vivo function of the Kif3C gene, we used homologous recombination in embryonic stem cells to construct two different knockout mouse strains for the Kif3C gene. Both homozygous Kif3C mutants are viable, reproduce normally, and apparently develop normally. These results suggest that Kif3C is dispensable for normal neural development and behavior in the mouse.

Impact of chronic hepatitis B and interferon-alpha therapy on growth of children.

Interferon-alpha (IFN) has been approved as treatment for children with chronic hepatitis B (CHB). The aims of this study were to assess the impact on children's growth of the disease itself and of IFN treatment. The growth of 142 children with CHB (70 IFN-treated, 72 untreated) was monitored for a minimum of one year. Regression analysis models were used to determine which of the variables most affected children's growth. After adjusting for racial differences, the population of 142 children with CHB had a mean baseline height for age percentile of 39 and a mean baseline weight for age percentile of 38, which were significantly different (P < 0.0001) from the 50th percentiles of their respective reference populations. The height for age Z score of untreated children was inversely correlated with serum hepatitis B virus DNA and aspartate aminotransferase levels, and the weight for age Z score was inversely correlated with serum hepatitis B virus DNA levels. While undergoing IFN therapy, children displayed a "U-shaped" growth pattern, such that height for age and weight for age Z scores at 3 or 6 months were lower than scores at baseline or 12 months. In this study the average child with CHB showed compromised growth even in the absence of IFN therapy. During IFN therapy, children's growth was temporarily disrupted.

Functional analysis of mouse C-terminal kinesin motor KifC2.

Proteins of the kinesin superfamily define a class of microtubule-dependent motors that play crucial roles in cell division and intracellular transport. In the mouse, several kinesin motors have been characterized and are suggested to play roles in axonal and/or dendritic transport. One such kinesin is KifC2. Sequence and secondary structure analysis revealed that KifC2 is a member of the C-terminal motor family. Northern and Western blot analyses indicated that KifC2 is specifically expressed in both the central and peripheral nervous systems. The cellular locations of the KifC2 proteins were found to be mainly in neural cell bodies and dendrites but also in axons. To understand the in vivo function of the KifC2 gene, we used homologous recombination in embryonic stem cells to construct knockout mouse strains for the KifC2 gene. Homozygous KifC2 mutants were viable and reproduced normally, and their development was apparently normal. These results suggest that KifC2 is dispensable for normal neural development and behavior in the mouse.

Molecular cloning and functional analysis of mouse C-terminal kinesin motor KifC3.

Proteins of the kinesin superfamily define a class of microtubule-dependent motors that play crucial roles in cell division and intracellular transport. To study the molecular mechanism of intracellular transport involving microtubule-dependent motors, a cDNA encoding a new kinesin-like protein called KifC3 was cloned from a mouse brain cDNA library. Sequence and secondary structure analysis revealed that KifC3 is a member of the C-terminal motor family. In contrast to other mouse C-terminal motors, KifC3 is apparently ubiquitous and may have a general role in intracellular transport. To understand the in vivo function of the KifC3 gene, we used homologous recombination in embryonic stem cells to construct knockout mouse strains for the KifC3 gene. Homozygous mutants of the KifC3 gene are viable, reproduce normally, and apparently develop normally. These results suggest that KifC3 is dispensable for normal development and reproduction in the mouse.

Hepatitis B in childhood: An update for the paediatrician.

Hepatitis B virus (HBV) infection may lead to acute or chronic hepatitis, cirrhosis and hepatocellular carcinoma. The incidence rate of paediatric hepatitis B is 0.2/100,000 to 1.8/100,000 in Canada. Hepatitis B virus infection is acquired largely through mother-to-infant (vertical) or community-based (horizontal) transmission in early childhood, whereas older children are susceptible to HBV infection through exposure to contaminated blood during intravenous drug use or through sexual transmission. Immigrants from endemic areas and some Native Canadian populations are also at a higher risk for HBV infection. Infection with HBV may manifest in three forms: acute self-limited hepatitis, chronic hepatitis or massive hepatic necrosis causing acute liver failure. The identification of HBV infection and the characterization of the disease relies on serological and virological tests. The course of chronic hepatitis B may be classified into three phases: an immunotolerant phase, an active phase and an inactive phase. Current treatment options include interferon-alpha and lamivudine for individuals with elevated serum alanine aminotransferase levels and markers of persistent viral replication. Children with chronic hepatitis B require regular monitoring and age-appropriate lifestyle counselling. Paediatricians are well-positioned to promote vaccination and encourage testing of those who are at risk for hepatitis B. With effective universal vaccination against hepatitis B, this infection could be essentially eliminated in Canada.