Occult HBV in NANB fulminant hepatitis

Molecular mechanisms underlying occult hepatitis B virus infection

Chronic hepatitis B virus (HBV) infection is a complex clinical entity frequently associated with cirrhosis and hepatocellular carcinoma (HCC). The persistence of HBV genomes in the absence of detectable surface antigenemia is termed occult HBV infection. Mutations in the surface gene rendering HBsAg undetectable by commercial assays and inhibition of HBV by suppression of viral replication and viral proteins represent two fundamentally different mechanisms that lead to occult HBV infections. The molecular mechanisms underlying occult HBV infections, including recently identified mechanisms associated with the suppression of HBV replication and inhibition of HBV proteins, are reviewed in detail. The availability of highly sensitive molecular methods has led to increased detection of occult HBV infections in various clinical settings. The clinical relevance of occult HBV infection and the utility of appropriate diagnostic methods to detect occult HBV infection are discussed. The need for specific guidelines on the diagnosis and management of occult HBV infection is being increasingly recognized; the aspects of mechanistic studies that warrant further investigation are discussed in the final section.

Molecular mechanisms underlying occult hepatitis B virus infection

Chronic hepatitis B virus (HBV) infection is a complex clinical entity frequently associated with cirrhosis and hepatocellular carcinoma (HCC). The persistence of HBV genomes in the absence of detectable surface antigenemia is termed occult HBV infection. Mutations in the surface gene rendering HBsAg undetectable by commercial assays and inhibition of HBV by suppression of viral replication and viral proteins represent two fundamentally different mechanisms that lead to occult HBV infections. The molecular mechanisms underlying occult HBV infections, including recently identified mechanisms associated with the suppression of HBV replication and inhibition of HBV proteins, are reviewed in detail. The availability of highly sensitive molecular methods has led to increased detection of occult HBV infections in various clinical settings. The clinical relevance of occult HBV infection and the utility of appropriate diagnostic methods to detect occult HBV infection are discussed. The need for specific guidelines on the diagnosis and management of occult HBV infection is being increasingly recognized; the aspects of mechanistic studies that warrant further investigation are discussed in the final section.

Occult hepatitis B virus infection: a covert operation

Detection of occult hepatitis B requires assays of the highest sensitivity and specificity with a lower limit of detection of less than 10 IU/mL for hepatitis B virus (HBV) DNA and <0.1 ng/mL for hepatitis B surface antigen (HBsAg). This covert condition is relatively common in patients with chronic hepatitis C virus (HCV) that seems to exert some influence on the replicative capacity and latency of HBV. Detection of virus-specific nucleic acid does not always translate into infectivity, and the occurrence of primer-generated HBV DNA that is of partial genomic length in immunocompetent individuals who have significant levels of hepatitis B surface antibody (anti-HBs) may not be biologically relevant. Acute flares of alanine aminotransferase (ALT) that occur during the early phase of therapy for HCV or ALT levels that remain elevated at the end of therapy in biochemical nonresponders should prompt an assessment for occult hepatitis B. Similarly, the plasma from patients with chronic hepatitis C that is hepatitis B core antibody (anti-HBc) positive (+/-anti-HBs at levels of <100 mIU/mL) should be examined for HBV DNA with the most sensitive assay available. If a liver biopsy is available, immunostaining for hepatitis B surface antigen (HBsAg) and hepatitis B core antigen (HBcAg) should be contemplated and a portion of the sample tested for HBV DNA. This is another reason for optimal collection of a specimen (e.g. two passes with a 16-guage needle under ultrasound guidance). Transmission of HBV to immunosuppressed orthotopic liver transplant recipients by donors with occult hepatitis B (OHB) will continue to occupy the interests of the transplant hepatologist. As patients with OHB may have detectable HBV DNA in serum, peripheral blood mononuclear cells (PBMC) and/or liver that can be reactivated following immunosuppression or intensive cytotoxic chemotherapy, the patient needs to be either monitored or treated depending on the pretreatment serological results such as an isolated anti-HBc reaction or a detectable HBV DNA.

Viral hepatitis-related acute liver failure

OBJECTIVES

Viral hepatitis has previously been the major cause of acute liver failure (ALF) in the United States. We aimed to determine the incidence of viral hepatitis-related ALF and to compare the outcome and clinical and biochemical variables in patients with hepatitis A and B.

METHODS

A total of 354 patients with ALF from multiple centers were screened for possible acute viral etiology.

RESULTS

Forty-three patients (12.1% of all ALF cases) had acute viral hepatitis: hepatitis A (n = 16), hepatitis B (n = 26), and herpes simplex virus infection (n = 1). There was no difference between groups with regard to age, gender, body mass index, admission or peak coma grade, symptom duration, admission mean arterial pressure, temperature, or biochemical liver tests, creatinine, arterial pH, or rate of infections. Platelet count was significantly higher in hepatitis A patients than in hepatitis B patients. The transplantation-free (spontaneous) survival rate was significantly higher for hepatitis A patients (69%) than for hepatitis B patients (19%, p = 0.007), whereas the liver transplantation rate was higher in hepatitis B patients (62%) than in hepatitis A patients (19%, p = 0.017). Spontaneous survivors had significantly higher mean arterial pressure, higher platelet count, and lower AST/ALT ratio than patients who did not survive spontaneously.

CONCLUSIONS

Viral hepatitis now comprises only one-eighth of all ALF cases in the United States. The marked difference in spontaneous survival between hepatitis A and B cannot be explained by the severity of hepatic dysfunction on admission but may rather be an inherent feature of the infections or a bias toward transplanting patients with hepatitis B.

Etiopathogenesis of acute hepatic failure: Eastern versus Western countries

Etiopathogenesis of acute hepatic failure (AHF) in Eastern and Western countries is distinct. In the East hepatitis viruses cause AHF in more than 95% of such cases, while causes of AHF in the West are quite heterogenous. Hepatitis E virus is the major etiological agent of AHF in countries like India where the virus is hyperendemic. Occult HBV infection may also be causing AHF in a sizable proportion of cases in areas where chronic HBV infection frequency is high. Paracetamol causes AHF in about 70% cases in the UK and about 20% cases in USA, whereas in France and Denmark, non-steroidal anti-inflammatory drugs are more frequently associated with AHF. Hepatitis B virus causes AHF in about one-third of cases in the latter two countries.

Occult hepatitis B virus infection and its clinical implications

Occult hepatitis B virus (HBV) infection is characterized by presence of HBV infection with undetectable hepatitis B surface antigen (HBsAg). Serum HBV level is usually less than 104 copies/mL in these patients. Diagnosis of occult HBV infection requires sensitive HBV-DNA PCR assay. Several possibilities have been hypothesized as the mechanisms of occult HBV infection. These include: (i) mutations of HBV-DNA sequence; (ii) integration of HBV-DNA into host's chromosomes; (iii) infection of peripheral blood mononuclear cells by HBV; (iv) formation of HBV-containing immune complex; (v) altered host immune response; and (vi) interference of HBV by other viruses. The precise prevalence of occult HBV infection remains to be defined. The clinical implications of occult HBV infection involve different clinical aspects. First of all, occult HBV infection harbours potential risk of HBV transmission through blood transfusion, haemodialysis, and organ transplantation. Second, it may serve as the cause of cryptogenic liver disease, contribute to acute exacerbation of chronic hepatitis B, or even fulminant hepatitis. Third, it is associated with development of hepatocellular carcinoma. Fourth, it may affect disease progression and treatment response of chronic hepatitis C. Most of the previous studies utilized retrospective observation without control groups, and lacked direct association of occult HBV infection with specific pathological changes and disease progression. Highly sensitive, quantitative, and functional molecular analyses of HBV, combined with a well-designed prospective clinical assessment will provide the best approach for the future study of occult HBV infection.

GB virus C/hepatitis G virus and other putative hepatitis non A-E viruses

The identification of the major agents causing human hepatitis (Hepatitis A, B, C, D and E Viruses) was achieved during the last 30 years. These viruses are responsible for the vast majority of human viral hepatitis cases, but there are still some cases epidemiologically related to infectious agents without any evidence of infection with known virus, designated as hepatitis non A-E. Those cases are considered to be associated with at least three different viruses: 1--Hepatitis B Virus mutants expressing its surface antigen (HBsAg) with altered epitopes or in low quantities; 2--Another virus probably associated with enteral transmitted non A-E hepatitis, called Hepatitis F Virus. Still more studies are necessary to better characterize this agent; 3--Hepatitis G Virus or GB virus C, recently identified throughout the world (including Brazil) as a Flavivirus responsible for about 10% of parenteral transmitted hepatitis non A-E. Probably still other unknown viruses are responsible for human hepatitis cases without evidence of infection by any of these viruses, that could be called as non A-G hepatitis.

Liver transplantation for acute and chronic viral hepatitis

Hepatotrophic viruses are responsible for a substantial proportion of cases of both end-stage chronic liver disease and of acute liver failure which are treated by liver transplantation. We review here current practice in transplantation for viral-induced liver disease addressing, in particular, the selection of patients for transplantation and the increasingly recognized problem of recurrent disease in liver grafts.

Exclusion in liver by polymerase chain reaction of hepatitis B and C viruses in acute liver failure attributed to sporadic non-A, non-B hepatitis

Hepatitis B and C viruses have been implicated in a few cases of acute liver failure attributed to sporadic (community acquired) non-A, non-B hepatitis, but reports are conflicting. We determined whether hepatitis B virus and hepatitis C virus were detectable in prospectively stored hepatectomies from seven British patients grafted for acute liver failure attributed to sporadic non-A, non-B hepatitis. For hepatitis B virus, we used nested polymerase chain reaction with primers to the core and surface regions. For hepatitis C virus, we used one round of reverse transcription polymerase chain reaction with primers to the 5' untranslated region and Southern hybridization using an internal oligonucleotide probe as well as nested PCR for the E1 region. Positive controls were native livers from two patients with unequivocal fulminant hepatitis B and from four patients with cirrhosis attributed to hepatitis C virus. Our negative findings suggest that, in the UK, acute liver failure attributed to sporadic non-A, non-B hepatitis most likely is caused by agent/s other than hepatitis B and C viruses.

Hepatitis C and E in non-A non-B fulminant hepatic failure: a polymerase chain reaction and serological study

A significant proportion of patients with fulminant hepatic failure have clinical, biochemical and histological features suggestive of acute viral hepatitis, without serological evidence of either hepatitis A or B. The contribution of hepatitis C to such cases of non-A non-B fulminant hepatic failure is presently uncertain while hepatitis E is well recognized as a cause of fulminant hepatic failure in endemic areas. Nested polymerase chain reaction for detection of both hepatitis C and E virus as well as two serological assays for anti-hepatitis C virus and anti-hepatitis E virus western blotting (both IgG and IgM) were performed on acute sera of 42 consecutive cases of non A, non B-fulminant hepatic failure and on convalescent sera of 17 of 20 patients who underwent orthotopic liver transplantation. Fresh liver tissue, obtained at the time of transplantation, was also studied by polymerase chain reaction in eight cases. Evidence of an acute hepatitis E virus infection (hepatitis E virus RNA amplified from serum by polymerase chain reaction or serum IgM positive to western blot) was found in eight patients. One patient had anti-HCV at presentation but assays on later sera proved negative. Convalescent sera and sera obtained after orthotopic liver transplantation were all negative to both anti-HCV assay systems, but HCV RNA was not found in either serum or liver tissue in any case.(ABSTRACT TRUNCATED AT 250 WORDS)