Chronic infection with hepatitis B virus (HBV) is a major cause of chronic liver disease, cirrhosis and hepatocellular carcinoma (HCC) worldwide. Globally there are an estimated 400 million persons infected with HBV. In the United States, there are 1.25 million affected individuals and the epidemiology of the infection is changing due to immigration of persons from endemic regions. The natural history of chronic hepatitis B (CHB) also appears to be changing with an increasing prevalence of HBeAg negative chronic hepatitis B. Knowledge of the rate of progression between individuals with HBeAg positive and negative CHB is unknown. An equally important and related issue is the clinical assessment of disease severity in patients with CHB. Unfortunately, there are no good laboratory markers of disease severity. Liver biopsy is the accepted gold standard for assessing disease severity and cirrhosis but is costly, invasive, and associated with complications, which often limits patient acceptability as well as being subject to sampling error ranging from 15% to 25%. Non-invasive methods to assess disease severity are highly desirable for physicians caring for patients with CHB. Despite the recent licensing of several new agents for treatment of CHB, therapy remains problematic due to the high rate of anti-viral drug resistance with nucleos(t)ide analogues and relatively poor response to interferon. Identifying the optimal regimen, defining when to treat, for how long and when to stop therapy are major unresolved issues. In addition, defining the best parameters to monitor patients both on and off therapy are not clear. Given the number of chronically infected persons and the requirement for long-term therapy in many of these patients, newer agents with different therapeutic targets are needed, as well as cheaper, more effective regimens. Hypotheses/problems addressed: 1) Define the host, viral and environmental factors that determine the natural history and outcome of HBV infection. To study this problem, we are creating a large database of untreated and treated patients with CHB (n800), which will be analyzed to identify factors that affect the natural history of chronic hepatitis B e antigen positive (HBeAg) positive and negative infections, including factors that predict the course in HBeAg negative CHB and the outcome of patients with normal ALT. The database is being used to develop a non-invasive model to predict fibrosis progression in patients with CHB. We also plan to evaluate the role of transient ultrasound elastography (Fibroscan) to assess fibrosis stage in persons with CHB. These results will be compared to liver biopsy, MRI elastography and plasma will be stored for future proteomic analysis. The goal is to develop a series of blood and imaging tests that will obviate the need for liver biopsy in most patients with CHB. The long-term durability of antibody following vaccination against hepatitis B virus in adults from a non-endemic population is unknown. We have initiated a study to assess the long-term durability of HBV vaccination in healthy persons vaccinated as adults. Persons who recovered from hepatitis B will serve as controls. To date we have enrolled 164 patients and we expect this important study to be completed in the next 3 months. The Liver Diseases Branch will participate in a large multicenter study, the Hepatitis B Research Network, to define the natural history of HBeAg positive and negative chronic hepatitis B. This study will enroll 2500 patients at 13 North American sites. Primary questions that will be spearheaded by our group will be to identify the predictors of spontaneous HBeAg loss in immunetolerant patients and to evaluate the role of hepatic steatosis with fibrosis progression in patients with chronic hepatitis B. 2) Develop and evaluate novel, safer and more effective therapies for chronic viral hepatitis. Current therapy of CHB remains less than optimal. Relapse is common if treatment is discontinued after one year in the absence of HBsAg loss. Consequently, nucleos(t)ides must often be administered long-term or indefinitely. However, long-term use is associated with the development of antiviral resistance with resulting loss of clinical benefit. Therefore an important challenge in HBV management is how to use these agents most effectively to achieve a long-term response while avoiding the issue of antiviral resistance. One strategy to prevent the development of antiviral resistance was to administer combination therapy using agents with different resistant profiles. We have conducted a randomized trial of lamivudine and adefovir versus adefovir monotherapy in patients with HBeAg positive and negative CHB with and without resistance to lamivudine to assess the benefits and safety of combination therapy for management of patients with untreated and resistant CHB. Forty-one patients were enrolled into this trial. The primary endpoint was a combined biochemical, virological and histological response that was maintained to 196 weeks. The major findings of this study were that a significantly greater proportion of patients receiving combination therapy achieved a combined maintained response and cleared HBeAg compared to those receiving monotherapy. Resistance was only observed in patients receiving adefovir monotherapy. These results suggest that combination therapy with lamivudine and adefovir may be more appropriate for long-term use. However, whether combination therapy will be necessary with more potent agents with better resistance profiles will need to be evaluated in future trials. These promising results have led us to evaluate the combination of tenofovir and emtricitabine compared to tenofovir for patients with CHB. Tenofovir is a nucleotide analogue that is more effective than adefovir at suppressing HBV DNA and has an excellent resistance profile. This study will examine the long-term efficacy and safety of tenofovir and emtricitabine versus tenofovir alone in patients with HBeAg positive and negative CHB with the goals of maintaining long-term viral suppression ands preventing the emergence of viral resistance. To date 22 patients have been enrolled and started on therapy. Long-term results are pending. An important question regarding therapy is whether treatment can ever be stopped in patients receiving long-term nucleos(t)ide analogues. To address this question we have initiated a prospective trial to withdraw patients from medication and observe for benefits (HBsAg loss) or adverse events (ALT flares, HBeAg seroreversion and fulminant hepatitis). To date 8 patients have been withdrawn from therapy. 3) Elucidate the viral pathogenesis of HBV infection and mechanisms of anti-viral resistance The course of CHB following the development of anti-viral resistance is highly variable with some patients showing continued viral suppression, some with an accelerated course and others who lie in-between. We hypothesized that following initial viral breakthrough, compensatory mutations that affect viral replication may account for the different clinical presentations observed. We also asked the question whether the outcome of resistance was different in HBeAg positive and negative CHB due to the presence of naturally occurring mutations- the pre-core and the double core promoter mutations, in HBeAg negative patients. Preliminary results suggest a mild (<2-fold) increase in viral replication of the adefovir resistant virus in the presence of the pre-core mutation. We are currently investigating the potential mechanism of this effect, since the pre-core mutation is not in the polymerase gene. An effect of the pre-core gene on the overlapping X-gene is being explored. These results might have clinical implications on how to manage adefovir resistance in HBeAg (+) and (-) patients.
Showing the most recent 10 out of 16 publications
