Immunopathogenesis of viral hepatitis

Late onset post-transfusion hepatitis E developing during chemotherapy for acute promyelocytic leukemia

We herein report the case of a leukemia patient who developed hepatitis E seven months after undergoing a transfusion with contaminated blood products. The latency period in this case was significantly longer than that of typical hepatitis E. Recently, chronic infection with hepatitis E virus (HEV) genotype 3 has been reported in immunocompromised patients. There is a possibility that our patient was unable to eliminate the virus due to immunosuppression following chemotherapy and the administration of steroids. The prevalence of HEV in healthy Japanese individuals is relatively high and constitutes a critical source of infection via transfusion. Hepatitis E is an important post-transfusion infection, and immunocompromised patients may exhibit a long latency period before developing the disease.

T cell immunopathogenesis and immunotherapeutic strategies for chronic hepatitis B virus infection

Hepatitis B is caused by the host immune response and T cells play a major role in the immunopathogenesis. More importantly, T cells not only destroy hepatocytes infected by hepatitis B virus (HBV), but also control HBV replication or eradicate HBV in a noncytolytic manner. Therefore, analysis of T cell immune response during acute and chronic HBV infection is important to develop a strategy for successful viral control, which could lead to immunotherapy for terminating persistent HBV infection. There have been many attempts at immunotherapy for chronic HBV infection, and some have shown promising results. High viral load has been shown to suppress antiviral immune responses and immunoinhibitory signals have been recently elucidated, therefore, viral suppression by nucleos(t)ide analogs, stimulation of antiviral immune response, and suppression of the immunoinhibitory signals must be combined to achieve desirable antiviral effects.

Genetic diversity of near genome-wide hepatitis C virus sequences during chronic infection: evidence for protein structural conservation over time

Infection with hepatitis C virus (HCV) is one of the leading causes of chronic hepatitis, liver cirrhosis and end-stage liver disease worldwide. The genetics of HCV infection in humans and the disease course of chronic hepatitis C are both remarkably variable. Although the response to interferon treatment is largely dependent on HCV genotypes, whether or not a relationship exists between HCV genome variability and clinical course of hepatitis C disease still remains unknown. To more thoroughly understand HCV genome evolution over time in association with disease course, near genome-wide HCV genomes present in 9 chronically infected participants over 83 total study years were sequenced. Overall, within HCV genomes, the number of synonymous substitutions per synonymous site (d(S)) significantly exceeded the number of non-synonymous substitutions per site (d(N)). Although both d(S) and d(N) significantly increased with duration of chronic infection, there was a highly significant decrease in d(N)/d(S) ratio in HCV genomes over time. These results indicate that purifying selection acted to conserve viral protein structure despite persistence of high level of nucleotide mutagenesis inherent to HCV replication. Based on liver biopsy fibrosis scores, HCV genomes from participants with advanced fibrosis had significantly greater d(S) values and lower d(N)/d(S) ratios compared to participants with mild liver disease. Over time, viral genomes from participants with mild disease had significantly greater annual changes in d(N), along with higher d(N)/d(S) ratios, compared to participants with advanced fibrosis. Yearly amino acid variations in the HCV p7, NS2, NS3 and NS5B genes were all significantly lower in participants with severe versus mild disease, suggesting possible pathogenic importance of protein structural conservation for these viral gene products.

Managing occupational risks for hepatitis C transmission in the health care setting

Hepatitis C virus (HCV) infection is a significant contemporary health problem in the United States and elsewhere. Because it is primarily transmitted via blood, hepatitis C infection presents risks for both nosocomial transmission to patients and occupational spread to health care workers. Recent insights into the pathogenesis, immunopathogenesis, natural history, and treatment of infection caused by this unique flavivirus provide a rationale for the use of new strategies for managing occupational hepatitis C infections when they occur. This article reviews this developing information. Recently published data demonstrate success rates in the treatment of "acute hepatitis C syndrome" that approach 100\%, and although these studies are not directly applicable to all occupational infections, they may provide important clues to optimal management strategies. In addition, the article delineates approaches to the prevention of occupational exposures and also addresses the difficult issue of managing HCV-infected health care providers. The article summarizes currently available data about the nosocomial epidemiology of HCV infection and the magnitude of risk and discusses several alternatives for managing exposure and infection. No evidence supports the use of immediate postexposure prophylaxis with immunoglobulin, immunomodulators, or antiviral agents. Based on the very limited data available, the watchful waiting and preemptive therapy strategies described in detail in this article represent reasonable interim approaches to the complex problem of managing occupational HCV infections, at least until more definitive data are obtained.

Underexpression of mRNA in human hepatocellular carcinoma focusing on eight loci

Genetic alterations associated with human hepatocellular carcinoma (HCC) have been reported previously, but are not sufficient to specify differences of HCCs from precancerous diseases of the liver, such as hepatitis, hepatic fibrosis, and cirrhosis. In the present study, we performed differential gene display analysis (DGDA) to clarify the specific genetic alterations associated with gene expression changes in the course of development of HCC from chronic viral hepatitis. Four pairs of surgically resected HCCs and hepatitis tissues were investigated. We found 1,028 expression sequence tags (ESTs) that were decreased or increased in HCC tissues compared with hepatitis tissues in the same patient. Nucleotide sequencing showed that they included 55 EST clones in the GenBank database, which were considered candidates for specific messenger RNA (mRNA) expression alterations in HCCs. After excluding 9 ESTs that code mitochondrial DNA, we performed quantitative real-time reverse-transcription polymerase chain reaction (RT-PCR) for the 46 remaining EST clones. We found 8 mRNAs underexpressed in primary HCC tissues in 20 patients in higher percentages than found in previous studies, including 18 cases (90%) for aldolase B (ALDOB), 15 cases (75%) for carbamyl phosphate synthetase 1 (CPS1), albumin (ALB), plasminogen (PLG), and EST 51549, 13 cases (65%) for cytochrome P450 subfamily 2E1 (CYP2E1), 12 cases (60%) for human retinol-binding protein 4 (RBP4), and 11 cases (55%) for human organic anion transporter C (OATP-C) gene. In conclusion, underexpression of key gene products may be important in the development and/or progression of HCC.

Neighborhood politics: the immunoregulatory function of organ-resident liver endothelial cells

The liver is known for its ability to induce antigen (Ag)-specific immune tolerance. Among the different cell populations involved in the induction of hepatic tolerance, the liver sinusoidal endothelial cells (LSECs) are particularly important because they are highly efficient at presenting soluble Ags to CD4(+) and CD8(+) T cells. The crosspresentation of soluble Ags to CD8(+) T cells was believed previously to be restricted to professional Ag-presenting cells (APCs) such as dendritic cells (DCs). However, in contrast to DCs, crosspresentation by LSECs can induce Ag-specific immune tolerance. It is proposed that these organ-resident APCs act as sessile hepatic APCs that control the immune responses to soluble blood-borne Ags, in concert with APCs in lymphatic tissue.

Effects of immunosuppression and organ transplantation on the natural history and immunopathogenesis of hepatitis C virus infection

The hepatitis C virus (HCV) is recognized as the leading cause for parenterally transmitted hepatitis. It is characterized by a high propensity to chronicity. Several efforts have been directed towards understanding the natural history of chronic HCV infection and the immunopathogenic pathways involved in mediating liver injury in the non-immunosuppressed and immunosuppressed states. In the non-immunosuppressed setting, liver damage seems to be largely immune mediated. In contrast, in the non-immunosuppressed state, there are several other factors that may modify the natural course of the infection and play a role in mediating liver injury. In this review we will address the natural history, virological and immunological aspects of HCV infection. Also, the role played by immunosuppression and organ transplantation in modifying the course of the infection and the pathogenesis of liver injury will be discussed.

Competitive coexistence in antiviral immunity

Adaptive immunity to viruses in vertebrates is mediated by two distinct but complementary branches of the immune system: the cellular response, which eliminates infected cells, and the humoral response, which eliminates infectious virus. This leads to an interesting contest, since the two responses compete, albeit indirectly, for proliferative stimuli. How can a host mount a coordinated antiviral campaign? Here we show that competition may lead to a state of "competitive coexistence" in which, counterintuitively, each branch complements the other, with clinical benefit to the host. The principle is similar to free-market economics, in which firms compete, but the consumer benefits. Experimental evidence suggests this is a useful paradigm in antiviral immunity.

Fulminant hepatic failure resulting from lamivudine-resistant hepatitis B virus in a renal transplant recipient: durable response after orthotopic liver transplantation on adefovir dipivoxil and hepatitis B immune globulin

BACKGROUND

Mutations in the hepatitis B virus (HBV) genome may occur during therapy.

METHODS

We report an asymptomatic HBV carrier who underwent transplantation for end-stage renal disease. She developed an HBV flare 6 months after transplantation and was placed on lamivudine. After initial rapid improvement, she relapsed clinically and virologically. She decompensated with jaundice, peripheral edema, ascites, encephalopathy, coagulopathy, and hepatorenal syndrome. A liver biopsy specimen revealed submassive necrosis.

RESULTS

Emergency liver transplantation was performed: lamivudine was discontinued. Hepatitis B immunoglobulin and adefovir dipivoxil were initiated. Sixteen months after orthotopic liver transplantation, she is HBV DNA seronegative with normal liver enzymes. Sequencing of HBV polymerase gene from preliver transplantation sera did not detect the usual lamivudine resistance mutations in the YMDD motif but instead two other mutations (F514-->L, L528-->M). Lamivudine resistance was demonstrated in vitro.

CONCLUSIONS

Asymptomatic HBV carriers may reactivate following renal transplantation after immunosuppression. Resistance to lamivudine may result in severe hepatic damage in immunocompromised patients.