Resurgence of time allocation.

The resurgence of time allocation with pigeons was studied in three experiments. In Phase 1 of each experiment, response-independent food occurred with different probabilities in the presence of two different keylights. Each peck on the key changed its color and the food probability in effect. In Phase 2, the food probabilities associated with each keylight were reversed and, in Phase 3, food was discontinued in the presence of either keylight. The food probabilities were .25 and .75, in Experiment 1, and 0.0 and 1.0 in Experiment 2. More time was allocated to the keylight correlated with more probable food in Phases 1 and 2, and in Phase 3 resurgence of time allocation occurred for two of three pigeons in Experiment 1, and for each of four pigeons in Experiment 2. Because time had to be allocated to either of the two alternatives in Experiments 1 and 2, however, it was difficult to characterize the time allocation patterns in Phase 3 as resurgence when changeover responding approached zero. In Experiment 3 this issue was addressed by providing a third alternative uncorrelated with food such that in each phase, after 30 s in the presence of either keylight correlated with food, the third alternative always was reinstated, requiring a response to access either of the two keylights correlated with food. In this experiment, the food probabilities were similar to those in Experiment 1. Resurgence of time allocation occurred for each of three pigeons under this procedure. The results of these experiments suggest that patterns of time allocation resurge similarly to discrete responses and to spatial and temporal patterns of responding.

Thymoglobulin induction decreases rejection in solitary pancreas transplantation.

BACKGROUND: Solitary pancreas transplants, both pancreas transplant alone (PTA) and pancreas after kidney (PAK), have higher rejection rates and lower graft survivals than simultaneous pancreas-kidney transplants (SPK). The aim of this study is to compare three different antibody induction regimens in solitary pancreas transplant recipients and to assess the role of surveillance pancreas biopsies in the management of these patients. METHODS: Solitary pancreas transplant recipients between 01/98 to 02/00 (n=29) received induction with either daclizumab (1 mg/kg on day 0, 7, 14), OKT 3 (5 mg/day x0-7), or thymoglobulin (1.5 mg/kg/day x0-10). Maintenance immunosuppression was similar for the three groups. All rejections were biopsy-proven either by surveillance/protocol or when clinically indicated. RESULTS: The 1-year graft survival was 89.3% overall and 91.7% in the thymoglobulin group. Thymoglobulin significantly decreased rejection in the first 6 months when compared with OKT3 or daclizumab (7.7 vs. 60 vs. 50%). Acute rejections were seen on surveillance biopsies in the absence of biochemical abnormalities in 40% of patients. CONCLUSIONS: Thymoglobulin induction regimen led to a low incidence of acute rejection and a high rate of graft survival in solitary pancreas transplants. In addition, surveillance biopsies were useful in the detection of early acute rejection in the absence of biochemical abnormalities.

Development of autoimmune hepatitis in the setting of long-standing primary biliary cirrhosis.

Primary biliary cirrhosis and autoimmune hepatitis, the most common autoimmune liver diseases in adults, are frequently easily differentiated by a combination of clinical, biochemical, and histological features along with the presence of highly sensitive and characteristic serum autoantibodies. Patients presenting with "overlapping" features of both conditions simultaneously are not uncommon. However, patients who switch over time from one disease to another have remained largely unrecognized. We report here two cases from the spectrum of autoimmune liver disease, patients who had well-defined primary biliary cirrhosis for a number of years and then developed the classic picture of superimposed autoimmune hepatitis. The importance of its recognition and the appropriate management modifications are discussed.

Autoimmune hepatitis with incidental histologic features of bile duct injury.

Bile duct changes are atypical of autoimmune hepatitis. Our aims were to assess the frequency and significance of these changes in classical disease. Liver biopsy specimens were reviewed under code from 84 patients who satisfied international scoring criteria for autoimmune hepatitis, and the findings were correlated with clinical features and outcome. Twenty patients (24%) had biliary changes, including 6 with destructive cholangitis, 4 with ductopenia, and 10 with nondestructive cholangitis. Patients with and without bile duct changes had similar laboratory findings. Diagnostic scores for autoimmune hepatitis were lower in patients with bile duct changes (16.6 +/- 0.6 vs. 19.1 +/- 0.2, P <.0001). The frequencies of scores sufficient for a definite (80% vs. 97%, P =.03) or probable diagnosis (20% vs. 3%, P =.03) were also less in this group. Patients with destructive cholangitis and/or ductopenia responded as well to therapy as patients with nondestructive cholangitis, and outcomes in each group were similar to those of patients without biliary changes. We concluded that biliary changes can occur in classic autoimmune hepatitis, and they are not associated with distinctive clinical features or treatment response. They may be coincidental findings associated with classic disease or weak expressions of a variant syndrome. In the absence of a cholestatic clinical syndrome, they do not compel a different management strategy.

Recurrent autoimmune hepatitis after orthotopic liver transplantation.

To determine the frequency, risk factors, and consequences of recurrent autoimmune hepatitis after liver transplantation, 41 patients with type 1 disease were monitored after surgery in accordance with a surveillance protocol. Tacrolimus or cyclosporine plus prednisone were administered to each patient, and liver biopsy examinations were performed at least annually according to protocol. Corticosteroid therapy was ultimately discontinued in only 2 patients. Recurrent disease was defined as the presence of lymphoplasmacytic infiltrates in liver tissue in the absence of other causes of allograft dysfunction. Autoimmune hepatitis recurred in 7 patients (17%), and the mean time to recurrence was 4.6 +/- 1 years. Recurrence was asymptomatic in 4 of 7 patients and detected only by surveillance liver biopsy assessment in 2 patients. Histological changes were mild, and there was no progression to cirrhosis during 4.9 +/- 0.9 years of observation. Five-year patient (86% v. 82%; P =.9) and graft (86% v. 67%; P =.5) survival rates were not statistically different between patients with and without recurrent disease. HLA-DR3 or HLA-DR4 occurred more commonly in patients with than without recurrence (100% v. 40%; P =.008) and healthy subjects (100% v. 49%; P =.01). Recurrent disease was unrelated to donor HLA status. In conclusion, recurrence after transplantation for type 1 autoimmune hepatitis is common. Its mild manifestations and favorable prognosis may reflect early detection by a surveillance protocol and/or continuous corticosteroid treatment. HLA-DR3- or HLA-DR4-positive recipients are at risk for recurrence regardless of donor HLA status.

Hepatic localization of endothelin-1 in patients with idiopathic portal hypertension and cirrhosis of the liver.

Endothelin-1 (ET-1) may mediate increased resistance to hepatic sinusoidal blood flow. We evaluated the hepatic distribution of ET-1 in patients with idiopathic portal hypertension (IPH), in which liver architecture may be normal, and in patients with cirrhosis, in which distortion of hepatic sinusoidal architecture is prominent. Immunohistochemistry and in situ hybridization were used to localize ET-1 in hepatic tissue of patients with IPH and cirrhosis. ET-1 was measured in plasma from a peripheral vein, the hepatic vein, and the portal vein of patients with cirrhosis of the liver and controls. On immunohistochemistry and in situ hybridization, ET-1 was localized to periportal hepatocytes and sinusoidal cells in patients with IPH and cirrhosis. Minimal positive staining for ET-1 was observed in control livers. Plasma ET-1 levels were significantly greater in patients with cirrhosis than in controls. In patients with cirrhosis, ET-1 was greater in the hepatic vein compared with the portal vein. However, the level of plasma ET-1 in patients with cirrhosis did not correlate with either the presence of ascites or portacaval pressure gradient. We conclude that in IPH, ET-1 is localized to sites in which it can modulate intrahepatic resistance. In late stages of cirrhosis, ET-1 may not modulate resistance. We speculate that vascular resistance in late stages of cirrhosis probably results from distortion of hepatic architecture.

Autoimmune cholangitis within the spectrum of autoimmune liver disease.

Autoimmune cholangitis is an idiopathic disorder with mixed hepatocellular and cholestatic findings. Our goal was to characterize the disease prospectively by application of uniform diagnostic criteria. Twenty patients were identified and compared with 242 patients with conventional forms of autoimmune liver disease. Patients with autoimmune cholangitis were distinguished from type 1 autoimmune hepatitis (AIH) by lower serum levels of aspartate transaminase (AST), gamma-globulin, and immunoglobulin G; higher serum levels of alkaline phosphatase; and lower frequencies of autoantibodies. They were distinguished from primary biliary cirrhosis (PBC) by higher serum levels of AST and bilirubin, lower serum concentrations of immunoglobulin M, and greater occurrence of autoantibodies. Their female predominance, lower serum alkaline phosphatase levels, higher frequency of autoantibodies, and absence of inflammatory bowel disease differentiated them from primary sclerosing cholangitis (PSC). Laboratory findings ranged widely and did not characterize individual patients. HLA risk factors were similar to those of type 1 AIH and PBC, and different from those of PSC. Treatment responses to corticosteroids or ursodeoxycholic acid were poor. Composite histological patterns resembled mainly PBC or PSC. We conclude that autoimmune cholangitis diagnosed by prospective analysis cannot be assimilated into a single, conventional, diagnostic category. It may represent variant forms of diverse conditions, a transition stage, or a separate entity with varying manifestations.

The importance of clinicopathological correlation in the diagnosis of inflammatory conditions of the colon: histological patterns with clinical implications.

Histological reaction patterns within the colon are not disease-specific but reflect mechanisms of injury and duration of disease. By correlating these patterns with known causes of colonic inflammation, we provide guidelines to enhance the diagnostic value of colonoscopic samples. Normal histological features are reviewed, and the sequence of inflammation and repair is used as the basis for appreciating pathological deviations. The common histological patterns of acute colitis with and without features of pseudomembranous or ischemic colitis and the morphological features of chronic colitis with and without crypt destruction are collated with clinical and endoscopic features to emphasize the importance of dialogue between the pathologist and gastroenterologist. Less common patterns, including eosinophilic colitis, graft-versus-host disease, chronic mucosal prolapse, portal hypertensive colopathy, and nonspecific or idiopathic ulcer, illustrate variations in the basic reaction patterns. Difficulties in differential diagnosis are underscored, and biopsy strategies are suggested.

Clinical and pathologic correlation of 84 mucinous cystic neoplasms of the pancreas: can one reliably differentiate benign from malignant (or premalignant) neoplasms?

OBJECTIVE: To determine whether the long-term behavior of cystic mucinous neoplasms of the pancreas could be predicted using a novel, precisely defined classification of benign mucinous cystadenomas, noninvasive proliferative cystic mucinous neoplasms, and invasive mucinous cystadenocarcinomas. The primary interest was to obtain long-term follow-up after complete resection to determine the recurrence rates based on this objective classification. BACKGROUND: Current understanding is that all cystic mucinous neoplasms of the pancreas are potentially malignant and that mucinous cystadenomas, when completely removed, are biologically benign. Cystadenocarcinomas are thought to be less aggressively malignant than ordinary ductal adenocarcinoma, but reported recurrence rates vary widely and are unpredictable. METHODS: All patients who underwent "curative" resection for cystic mucinous neoplasms at Mayo Clinic Rochester from 1940 to 1997 were identified. All available pathology slides, gross specimens, and clinical records were reviewed, eliminating patients with inadequate documentation. Neoplasms were reclassified as mucinous cystadenomas, noninvasive proliferative mucinous cystic neoplasms, or invasive cystadenocarcinomas based on specific histologic criteria. RESULTS: Of 84 patients (70 women, 14 men) with cystic mucinous neoplasms of the pancreas, 54 were classified as cystadenomas, 23 as noninvasive proliferative cystic mucinous neoplasms, and only 7 as cystadenocarcinomas. Recurrent disease developed in none of the 77 patients without invasion, but 5 of the 6 patients surviving resection for cystadenocarcinomas died of recurrent cystadenocarcinoma within 5 years. CONCLUSIONS: When the neoplasm is completely resected and subjected to adequate histopathologic examination based on these objective criteria, absence of tissue invasion predicts a curative operation and detailed follow-up may be unnecessary. In contrast, a histologic diagnosis of invasive cystadenocarcinoma portends a dismal prognosis, similar to that of typical ductal adenocarcinoma of the pancreas.

Strategies for assessing the implications of malformed frogs for environmental health.

The recent increase in the incidence of deformities among natural frog populations has raised concern about the state of the environment and the possible impact of unidentified causative agents on the health of wildlife and human populations. An open workshop on Strategies for Assessing the Implications of Malformed Frogs for Environmental Health was convened on 4-5 December 1997 at the National Institute of Environmental Health Sciences in Research Triangle Park, North Carolina. The purpose of the workshop was to share information among a multidisciplinary group with scientific interest and responsibility for human and environmental health at the federal and state level. Discussions highlighted possible causes and recent findings directly related to frog deformities and provided insight into problems and strategies applicable to continuing investigation in several areas. Possible causes of the deformities were evaluated in terms of diagnostics performed on field amphibians, biologic mechanisms that can lead to the types of malformations observed, and parallel laboratory and field studies. Hydrogeochemistry must be more integrated into environmental toxicology because of the pivotal role of the aquatic environment and the importance of fates and transport relative to any potential exposure. There is no indication of whether there may be a human health factor associated with the deformities. However, the possibility that causal agents may be waterborne indicates a need to identify the relevant factors and establish the relationship between environmental and human health in terms of hazard assessment.

Persistent, antigen-specific, therapeutic antitumor immunity by dendritic cells genetically modified with an adenoviral vector to express a model tumor antigen.

Dendritic cells (DC) are potent antigen-presenting cells that play a critical role in the initiation of cellular immune responses. Using a BALB/c syngeneic colon carcinoma cell line expressing a model tumor antigen beta-galactosidase (betagal), we previously reported (Song et al, J Exp Med 1997; 186: 1247-1256) that immunization of mice with a single injection of DCs genetically modified with an adenovirus vector expressing betagal confers potent protection against a lethal intravenous tumor challenge, as well as suppression of pre-established lung tumors, resulting in a significant survival advantage. In the present study, we have addressed the question: how long does the memory of tumor antigen- specific immunity persists after DC priming in vivo using this genetically modified DC-based cancer vaccination strategy? To accomplish this, two groups of mice were evaluated: (1) mice surviving >400 days following protection from an initial intravenous tumor challenge after immunization with DC genetically modified to express betagal; and (2) mice surviving >300 days that had previously demonstrated regression of pre-established lung tumors after treatment with DC immunization. By analyzing the antigen-specific cytotoxic T lymphocyte response and challenging these long-term survival mice with a second subcutaneous tumor administration, the data demonstrate that a single administration of DC genetically modified to express a model antigen induces long-lasting, antigen-specific antitumor immunity in both naive and tumor-bearing hosts, observations that have important implications in the development of genetically modified DC-based antitumor vaccination strategies. Gene Therapy (2000) 7, 2080-2086.

Perspectives on the role of the human gut microbiota and its modulation by pro- and prebiotics.

One of the most topical areas of human nutrition is the role of the gut in health and disease. Specifically, this involves interactions between the resident microbiota and dietary ingredients that support their activities. Currently, it is accepted that the gut microflora contains pathogenic, benign and beneficial components. Some microbially induced disease states such as acute gastroenteritis and pseudomembranous colitis have a defined aetiological agent(s). Speculation on the role of microbiota components in disorders such as irritable bowel syndrome, bowel cancer, neonatal necrotising enterocolitis and ulcerative colitis are less well defined, but many studies are convincing. It is evident that the gut microflora composition can be altered through diet. Because of their perceived health-promoting status, bifidobacteria and lactobacilli are the commonest targets. Probiotics involve the use of live micro-organisms in food; prebiotics are carbohydrates selectively metabolized by desirable moieties of the indigenous flora; synbiotics combine the two approaches. Dietary intervention of the human gut microbiota is feasible and has been proven as efficacious in volunteer trials. The health bonuses of such approaches offer the potential to manage many gut disorders prophylactically. However, it is imperative that the best methodologies available are applied to this area of nutritional sciences. This will undoubtedly involve a genomic application to the research and is already under way through molecular tracking of microbiota changes to diet in controlled human trials.

Ursodeoxycholic acid as adjunctive therapy for problematic type 1 autoimmune hepatitis: a randomized placebo-controlled treatment trial.

To evaluate the efficacy of ursodeoxycholic acid as adjunctive therapy in type 1 autoimmune hepatitis, 37 patients who had experienced treatment failure, repeated relapse, or incomplete response were randomized to ursodeoxycholic acid (13-15 mg/kg daily) or placebo for 6 months in addition to their usual corticosteroid schedule. Serum aspartate transaminase (70% vs. 31%, P =.04) and alkaline phosphatase (47% vs. 7%, P =.02) levels improved more commonly in the 21 patients randomized to ursodeoxycholic acid. Mean serum levels, however, were similar before and after the treatment period. The frequency of dose reduction or corticosteroid withdrawal was comparable in both groups (29% versus 31%, P >.9), and clinical improvement (48% vs. 44%, P >.9) or its absence (52% vs. 56%, P >.9) occurred as commonly in patients receiving ursodeoxycholic acid or placebo. The modified histological activity score (3.5 +/- 0.8 vs. 3. 5 +/- 0.9) and the modified fibrosis score (2.4 +/- 0.4 vs. 2.4 +/- 0.4) were similar before and after treatment with ursodeoxycholic acid and no different than after placebo therapy. We conclude that ursodeoxycholic acid can improve certain laboratory tests in problematic patients with type 1 autoimmune hepatitis when administered adjunctively for 6 months. Short-term therapy, however, does not facilitate reduction in the dose of corticosteroids or its withdrawal, affect clinical outcome, or reduce histological activity.

Host- and disease-specific factors affecting steatosis in chronic hepatitis C.

BACKGROUND/AIM: Steatosis is commonly present in chronic hepatitis C. Our aim was to evaluate host- and disease-specific factors associated with its occurrence. METHODS: Histologic findings in 60 patients were correlated with body mass index, human leukocyte antigens, and other conventional parameters. Comparisons were made with 41 patients who had nonalcoholic steatohepatitis and 18 patients who had chronic hepatitis B. RESULTS: Patients with chronic hepatitis C and steatosis had lower serum concentrations of gamma-globulin (p=0.01) and immunoglobulin G (p=0.05) than their counterparts without steatosis, and they had a lower frequency of antinuclear antibodies (19% versus 52%, p=0.01). They also had a higher mean body mass index (p=0.002) and a greater frequency of risk factors for steatosis (70% versus 34%, p=0.009). These risk factors, however, occurred more commonly in patients with nonalcoholic steatosis (p=0.007). Furthermore, fat deposition occurred more often in chronic hepatitis C than in chronic hepatitis B (52% versus 22%, p=0.03), despite comparable metabolic findings. The degree of steatosis in chronic hepatitis C was not associated with individual metabolic features. CONCLUSIONS: Steatosis in chronic hepatitis C is mainly a viral effect, and host-dependent metabolic factors may potentiate the manifestation. Fat deposition is associated with less immunoreactivity and it may connote a distinctive pathogenic mechanism.

Modulation of 7,12-dimethylbenz[a]anthracene disposition and hepatocarcinogenesis by dieldrin and chlordecone in rainbow trout.

The present study examined whether modified xenobiotic transport, resulting from chlordecone (CD) or dieldrin pretreatment, would alter polycyclic aromatic hydrocarbon (PAH) or organochlorine (OC) target organ doses and subsequent tumor organospecificity or incidence rates in rainbow trout. Additionally, the potential for exposure to dieldrin or CD, following PAH exposure, to enhance tumor incidence was assessed. Evaluation of CD pretreatment effects on [14C]CD disposition in trout was conducted following two i.p. (0-15 mg/kg) and two dietary (0-0.4 mg/kg/d) pretreatment regimes. To assess the influence of OC pretreatment on cancer induced by the PAH 7,12-dimethylbenz[a]anthracene (DMBA), juvenile trout were fed control, CD (0.1, 0.4 mg/kg/d), or dieldrin (0.1, 0.3 mg/kg/d) diets for 9 wk, received a waterborne [3H]DMBA exposure (1 mg/L, 20 h), and resumed control, CD, or dieldrin diets for 33 wk. [3H]DMBA disposition and hepatic [3H]DMBA binding were examined immediately and 24 h after exposure. Hepatic and stomach tumor incidences were determined 33 wk after DMBA exposure. CD pretreatment did not influence [14C]CD or [3H]DMBA hepatic concentrations, hepatic [3H]DMBA DNA binding, or hepatic/stomach tumor incidence. It did, however, elevate bile [14C]CD and [3H]DMBA concentrations. Postinitiation exposure to CD weakly enhanced DMBA-induced hepatic tumor incidence at the low but not the high CD dose. Dieldrin pretreatment did not influence stomach [3H]DMBA equivalents or stomach tumor incidence but did cause an elevation in biliary and hepatic concentrations of [3H]DMBA equivalents. [3H]DMBA binding to liver DNA was significantly increased and hepatic tumor incidence was elevated by dieldrin pretreatment. Dieldrin treatment following DMBA initiation did not enhance hepatic or stomach tumor incidence. Ecoepidemiology studies, to date, have reported correlations between the co-occurrence of PAHs and OCs and elevated tumor incidence in feral fish, but cause-and-effect relationships have been difficult to establish. The results of the present study confirm that OCs, such as dieldrin and CD, play a role in modifying PAH-induced carcinogenesis in fish.

GB virus-C infection in type 1 autoimmune hepatitis.

OBJECTIVE: To assess the frequency and significance of GB virus-C infection in type 1 autoimmune hepatitis. MATERIAL AND METHODS: Serum specimens from 94 patients with type 1 autoimmune hepatitis were tested for GB virus-C RNA by reverse transcription and polymerase chain reaction. Serum samples from 50 normal subjects were also assessed. RESULTS: Three of the 94 specimens from patients with autoimmune hepatitis were positive for GB virus-C RNA in comparison with none of the 50 control samples (3% versus 0%; P = 0.5). Two patients were seropositive after variceal hemorrhage and blood transfusion, including one patient who clearly acquired the infection in this fashion. One patient had no epidemiologic basis for his seropositivity. Viremia was prolonged in all infected patients (mean duration, 69 +/- 23 months; range, 36 to 113); however, no clinical features suggested a concurrent viral infection, and mortality was similar to that among the uninfected counterparts (33% versus 8%; P = 0.2). Liver transplantation was more common in the infected patients (67% versus 9%; P = 0.03), but the duration of disease was also longer in these patients (277 +/- 29 months versus 106 +/- 9 months; P = 0.0008). Clinical features and immediate responses to corticosteroid therapy were similar in both groups. CONCLUSION: GB virus-C RNA is found infrequently in type 1 autoimmune hepatitis, and GB virus-C is unlikely to be an important etiologic agent or prognostic determinant.

Bacterial and parasitic cholangitis.

Bacterial cholangitis is a clinically defined syndrome caused by the regurgitation of infected bile into the circulation. The pathogenic mechanism is unclear, and systemic sepsis may not occur. Prerequisite conditions are the presence of microorganisms in the bile and increased biliary pressure. Bacteria that commonly cause cholangitis are Escherichia coli, Klebsiella, Enterococcus, Enterobacter, Pseudomonas, and anaerobes. Although most infections are polymicrobial, this situation may not always prevail. Successful treatment depends on relieving biliary obstruction and administering antibiotics effective against bacteria in the circulation and the bile. The causes of biliary obstruction that predispose to bacterial cholangitis are myriad. Common conditions include biliary stones and benign strictures. In many parts of the world, biliary parasites are an important factor. Biliary parasites cause necrosis, inflammation, fibrosis, strictures, and cholangiectasis of the bile ducts by several mechanisms: (1) as a direct result of the irritating chemical composition of the parasite, parasitic secretions, or eggs; (2) physical obstruction of the bile ducts; (3) induction of formation of biliary stones; and (4) introduction of bacteria into the biliary system during migration from the duodenum. Therefore, bacterial cholangitis has an important and frequently dominant role in the pathogenesis and clinical course of biliary disease due to these parasitic infestations. Common biliary parasites include the nematode Ascaris lumbricoides, the trematodes Opisthorchis viverrini and felineus, Clonorchis sinensis, and Fasciola hepatica, and the cestodes Echinococcus granulosus and multilocularis. The epidemiologic, pathologic, and clinical manifestations of these parasitic infestations are reviewed.

Acute hepatitis E by a new isolate acquired in the United States.

OBJECTIVE: To report the first case of acute hepatitis E by a novel isolate acquired in the United States and confirmed by nucleotide sequencing. MATERIAL AND METHODS: We describe the clinical manifestations and the results of associated laboratory studies in a man who was found to have acute hepatitis E infection. RESULTS: A 62-year-old man was hospitalized because of fever, abdominal pain, and jaundice. After an initial evaluation did not provide a cause, his serum was found to be positive for IgG anti-hepatitis E virus (HEV) by three antibody assays. Serum was also positive for HEV RNA by reverse transcriptase polymerase chain reaction (PCR). Sequencing results from the PCR products demonstrated substantial differences at the nucleotide level between this strain and the known Mexican and Burmese strains. CONCLUSION: On the basis of this initial report, HEV should be considered an etiologic agent in patients with acute non-ABC hepatitis in the United States.

Dendritic cells genetically modified with an adenovirus vector encoding the cDNA for a model antigen induce protective and therapeutic antitumor immunity.

Dendritic cells (DCs) are potent antigen-presenting cells that play a critical role in the initiation of antitumor immune responses. In this study, we show that genetic modifications of a murine epidermis-derived DC line and primary bone marrow-derived DCs to express a model antigen beta-galactosidase (betagal) can be achieved through the use of a replication-deficient, recombinant adenovirus vector, and that the modified DCs are capable of eliciting antigen-specific, MHC-restricted CTL responses. Importantly, using a murine metastatic lung tumor model with syngeneic colon carcinoma cells expressing betagal, we show that immunization of mice with the genetically modified DC line or bone marrow DCs confers potent protection against a lethal tumor challenge, as well as suppression of preestablished tumors, resulting in a significant survival advantage. We conclude that genetic modification of DCs to express antigens that are also expressed in tumors can lead to antigen-specific, antitumor killer cells, with a concomitant resistance to tumor challenge and a decrease in the size of existing tumors.