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The hepatitis B virus
Insights
Hepatitis B virus (HBV) causes significant global illness and death. New PCR methods reveal inaccuracies in older serological interpretations, highlighting the need for better diagnostics and treatments for chronic HBV infection.
Area of Science:
- Hepatology and Virology
- Immunology and Infectious Diseases
Background:
- Hepatitis B virus (HBV) is a leading cause of global morbidity and mortality due to its transmissibility and potential for chronic infection, leading to cirrhosis and hepatocellular carcinoma.
- Previous interpretations of serological data for HBV infection are being revised with the advent of Polymerase Chain Reaction (PCR) technology.
- Detectable HBV DNA is found in patients with anti-HBe and anti-HBs, and even in some hepatocellular carcinoma cases lacking serological markers, indicating complex viral persistence.
Purpose of the Study:
- To review the current understanding of HBV infection, including diagnostic challenges, host immune responses, and therapeutic strategies.
- To highlight the evolving interpretation of serological markers in light of PCR findings.
- To discuss the role of immune responses and potential interventions for managing HBV.
Main Methods:
- Review of existing literature on HBV serology, PCR detection of HBV DNA, and host immune responses (interferon system, cytotoxic T cells, humoral immunity).
- Analysis of clinical data regarding the effectiveness of immunization, immune stimulation, and antiviral chemotherapy.
- Consideration of emerging findings, such as pre-core region mutations in HBV isolates.
Main Results:
- PCR has revealed that some patients with apparent serological resolution of HBV still harbor detectable viral DNA.
- Host immune clearance of HBV-infected cells involves interferon and cellular immunity, with nucleocapsid proteins and pre-S sequences as key targets.
- Alpha-interferon therapy achieves HBe antigen clearance in 40-60% of adults with chronic HBV, leading to reduced hepatic inflammation.
Conclusions:
- Accurate interpretation of HBV infection requires advanced diagnostics like PCR, as serological markers alone can be misleading.
- Effective management of HBV involves a multi-pronged approach including immunization, immune stimulation, and antiviral therapies tailored to different patient populations.
- Further research into HBV uptake mechanisms, in vitro models, and the role of viral mutants is crucial for developing improved treatments and prevention strategies.
Abstract:
Of all the hepatotropic viruses, HBV is associated with the greatest worldwide morbidity and mortality. This is because of the ease of transmission and the potential for progression to a chronic infective carrier state, with the complications of cirrhosis and hepatocellular carcinoma. The use of PCR has shown that some of the earlier concepts concerning the interpretation of serological data were inaccurate. Many patients with anti-HBe and anti-HBs have viral DNA detectable by PCR, and some hepatocellular carcinoma patients have detectable HBV DNA in their livers in the absence of all serological markers of HBV disease. The clearance of HBV infected cells from the liver is dependent on the interplay between the interferon system and the cellular limb of the host immune response. The importance of the nucleocapsid proteins as targets for sensitized cytotoxic T cells has been established for chronic HBV infection. The importance of pre-S sequences as inducers and targets of the virus-neutralizing humoral immune response is becoming established, but their precise role must await the development of in vitro models of hepadnavirus infection and a greater understanding of the mechanisms of viral uptake. The epidemiology and clinical course of the disease can be modified by immunization, immune stimulation and antiviral chemotherapy. For the developing world, a programme of immunization at birth would be the most effective way of eliminating this disease, but at present the cost is prohibitive. For the developed world, immunization is realistic for the at-risk population, and anti-viral and immunostimulatory therapy available for those already infected. In adult acquired chronic HBV infection alpha-interferon produces HBe antigen clearance in 40-60% of cases and is followed by resolution of the hepatic inflammation. Results in neonatally acquired infection are less impressive and prednisolone priming followed by interferon may be needed. The presence of a mutation in the pre-core region of some virus isolates has recently been described. Hepatocytes infected with this virus cannot produce HBe antigen and the course of the liver disease is fairly rapid. Whether this mutant causes liver damage in the same way as the wild virus or is directly cytopathic remains unclear, and its relationship to fulminant hepatitis is under investigation.