Lamivudine and Famciclovir resistant hepatitis B virus associated with fatal hepatic failure

Bozdayı

Antimicrob Agents Chemother

et al. 2005

The emergence of resistance to lamivudine has been one of the major stumbling blocks to successful treatment and control of hepatitis B virus (HBV) infections. The major mechanism of resistance has been attributed to the alteration in the YMDD motif of the HBV polymerase due to an amino acid change of rtM204 to V/I and an accompanying rtL180M conversion. A novel mutation pattern in a patient having clinical breakthrough under lamivudine therapy was discovered. The mutant had a rtL180C/M204I genotype and was detected after 2 years of therapy with lamivudine. To characterize this novel variant, site-directed mutagenesis was performed using a vector construct containing the HBV genome. Transient transfection studies in human hepatoma cells with HBV carrying the new mutant demonstrated that the rtL180C/M204I mutant was resistant to lamivudine up to 10 M. The resistance profile was comparable to that of the previously reported rtL180 M/M204I-containing virus. These observations were further confirmed by generation of stable cultures transfected with the mutant virus.Hepatitis B virus (HBV) is a pathogen that afflicts over 350 million people with liver disease worldwide (27). The persistence of the infection can have devastating consequences for the infected person, as the natural progression of the disease culminates with cirrhosis of the liver and hepatocellular carcinoma. Until recently, only two treatment options, alpha interferon and lamivudine, were available for the management of HBV. Recently, adefovir dipivoxil and entecavir were approved by the U.S. Food and Drug Administration for treatment of HBV (23,24).While the therapeutic utility of lamivudine is clearly documented in the literature (4,5,12,16,17), the emergence of resistance to lamivudine has been the major hurdle to viral clearance since long-term lamivudine monotherapy results in clinical resistance to the drug (18). The mutations responsible for the clinical nonresponse have been characterized (1,3,4,18) and can persist resulting in a major hurdle to viral clearance. While a number of mutations have been reported, the cardinal change that confers resistance has been the conversion of the methionine residue in the YMDD motif to valine or isoleucine (rtM204V/I) followed by the rtL180 M change (for review of mutations see references 19 and 23).There are some similarities in the resistance pattern to lamivudine between human immunodeficiency virus (HIV) and HBV (10). For example, a number of HIV cases show initial replacement of methionine with valine or isoleucine at residue 184 of the polymerase (6, 25), which corresponds to the rtM204V/I in HBV polymerase (26).Recently, mutations other than rtM204I/V have been reported for HBV (7,19,20,23). These changes, albeit observed at a lesser frequency, underscore the multiple strategies employed by the virus to circumvent inhibition of the viral replication machinery. The present studies are a continuation of our efforts to identify mechanisms underlying clinical resistance to lamivudine. A novel genotype wi...

Section: Discussionsupporting

confidence: 80%

mentioning

confidence: 99%

Emergence of a Novel Mutation in the FLLA Region of Hepatitis B Virus during Lamivudine Therapy

Bozdayı

Antimicrob Agents Chemother

et al. 2005

“…Furthermore, it was speculated that a sequential or a combination therapy with HBIG and lamivudine would produce the corresponding double mutations. Unfortunately, these predictions were confirmed by isolation of several double mutant strains [104,106,122,123,[146][147][148][149]. Taking these findings into account, it can be stated that for every given antiviral agent or therapy resistance can be expected, which calls for close monitoring of patients under such treatment.…”

Section: Double Mutantsmentioning

confidence: 99%

Hepatitis B: Where Are We Today?

Eckert¹,

Struff

2006

Transfus Med Hemother

Hepatitis B still is a major challenge of modern medicine. Here, we summarize the disease, the life cycle of the virus, the emergence of drug-resistant mutant strains and resulting consequences for new drug development. Hepatitis B has a worldwide prevalence of 0.1-20%. It occurs in an acute and a chronic phase. The acute phase is characterized by viral replication, onset of immune response leading to destruction of infected hepatocytes and, in most cases, viral clearance and lifelong immunity. Clinical symptoms are observed in this phase. The chronic phase is characterized by lifelong persistence of the virus, often without clinical symptoms but bearing the risk of hepatic cirrhosis or hepatocellular carcinoma. Both phases are distinguished by detection of viral antigens and hepatitis B antibodies in the blood. The hepatitis B virus (HBV) shows several features unique for hepadnaviridae: i) formation of covalently closed-circle DNA (cccDNA) as template for viral DNA replication and synthesis of viral RNAs and ii) a reverse transcription step in the synthesis of new viral DNAs. These features are the prime targets in antiviral drug development. Unfortunately, with the exception of interferon, resistant mutant strains of HBV were found after widespread use of every new drug so far. Therefore, combination therapies aimed at different targets are being discussed so that the selective pressure can no longer be compensated by HBV. This paper is the first part of a trilogy concerning HBV which will also discuss the situation regarding transplantation (second part) and blood transfusion (third part).

“…However, analysis of viral kinetics during lamivudine therapy revealed that a prolonged treatment is required since lamivudine does not completely inhibit viral replication and the rate of clearance for infected hepatocytes is slow [5] . HBV is not a cytopathogenic virus and hepatocytes are normally long-lived and their half-life is estimated to be 6-12 mo or longer, explaining the requirement for a long-term antiviral treatment course, which is associated with the selection of drug-resistant mutants [6] .…”

Section: Introductionmentioning

confidence: 99%

Combination of small interfering RNAs mediates greater suppression on hepatitis B virus cccDNA in HepG2.2.15 cells

Xin¹,

Li²,

Jin³

et al. 2008

WJG

AIM:To observe the inhibition of hepatitis B virus (HBV) replication and expression in HepG2.2.15 cells by combination of small interfering RNAs (siRNAs). METHODS: Recombinant plasmid psil-HBV was constructed and transfected into HepG2.2.15 cells. At 48 h, 72 h and 96 h after transfection, culture media were collected and cells were harvested for HBV replication assay. HBsAg and HBeAg in the cell culture medium were detected by enzyme-linked immunoadsorbent assay (ELISA). Intracellular viral DNA and covalently closed circular DNA (cccDNA) were quantified by real-time polymerase chain reaction (PCR). HBV viral mRNA was reverse transcribed and quantified by reverse-transcript PCR (RT-PCR). RESULTS: siRNAs showed marked anti-HBV effects. siRNAs could specifically inhibit the expression of HBsAg and the replication of HBV DNA in a dosedependent manner. Furthermore, combination of siRNAs, compared with individual use of each siRNA, exerted a stronger inhibition on antigen expression and viral replication. More importantly, combination of siRNAs significantly suppressed HBV cccDNA amplification. CONCLUSION: Combination of siRNAs mediates a stronger inhibition on viral replication and antigen