Molecular characterization of intrahepatic and extrahepatic hepatitis B virus (HBV) reservoirs in patients on suppressive antiviral therapy
Liver Unit, Division of Gastroenterology, Department of Medicine, Faculty of Medicine, University of Calgary, AB, Canada. Journal of Viral Hepatitis
(Impact Factor: 3.91).
06/2011; 18(6):415-23. DOI: 10.1111/j.1365-2893.2010.01321.x
The hepatitis B virus (HBV) replicates via an error-prone reverse transcriptase generating potential drug-resistant quasispecies. The degree of HBV variability in liver vs peripheral blood mononuclear cells (PBMC) in patients on long-term suppressive antivirals is unclear. We characterized HBV replication, drug resistance and molecular diversity in patients with plasma HBV DNA undetectable by clinical assays. Explant liver (n=9), PBMC (n=6) and plasma (n=7) from nine such patients undergoing liver transplantation were evaluated for HBV genomes by sensitive PCR/nucleic acid hybridization assay. Cases with HBV DNA in liver and PBMC were tested for covalently closed circular DNA (HBV cccDNA). HBV polymerase (P) amplicons were cloned, sequenced and both P and overlapping surface (S) gene sequences were analysed. HBV DNA was detected in 43% (3/7) of plasma, 100% (9/9) of liver and 83% (5/6) of PBMC samples. HBV cccDNA was detected in all liver and one PBMC sample. Four patients had a clinical diagnosis of resistance. HBV P gene sequencing revealed 100% wild type (wt) in plasma (2/2), 83% wt in PBMC (5/6) but livers of 3/9 (33%) contained wt and 6/9 (66%) carried resistance to lamivudine and/or adefovir. The translated S gene revealed no changes affecting HBV antigenicity. Sequences from livers with antiviral resistant mutants revealed greater interpatient quasispecies diversity. Despite apparent HBV suppression, the liver continues to support HBV replication and extrahepatic HBV can be detected. PBMC may be a sanctuary for wt virus during antiviral therapy, while the liver harbours more drug-resistant viruses. Drug resistance correlates with intrahepatic viral diversity.
Available from: PubMed Central
- "Despite apparent HBV suppression in plasma, the liver continued to support viral replication and harbor resistant viruses. On sequence and phylogenetic analysis of HBV P gene in the liver, the authors further demonstrated that drug resistance correlated with increased HBV quasispecies diversity
. In the study of Liu et al., the authors analyzed the quasispecies complexity of HBV in plasma of patients with entecavir treatment, in which all patients were divided into responders and partial responders. "
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Five nucleos(t)ide analogs are used to treat chronic hepatitis B. Ideal nucleos(t)ide analog therapy in chronic hepatitis B patients with kidney transplantation must ensure virological suppression and minimize renal injury. However, resistance to nucleos(t)ide analogs frequently results in virological breakthrough, hepatitis flare, and complicated deterioration of the transplanted kidney. Inappropriate rescue therapy for drug resistance may subsequently cause hepatitis B virus multidrug resistance. Currently, tenofovir is used to treat chronic hepatitis B patients with kidney transplantation. In the field, we first reported combination therapy with tenofovir plus entecavir in a kidney transplant chronic hepatitis B patient with nucleos(t)ide analog multidrug resistance.
A 50-year-old Chinese man with chronic hepatitis B and kidney transplantation received nucleos(t)ide analog therapy with sequential monotherapy and combination therapy. Virological parameters, hepatic enzymology and renal function were monitored. Drug-resistance mutations were detected by sequence analysis. Our patient received sequential nucleos(t)ide analog monotherapy and inappropriate combination therapy during 132 months, which caused multidrug resistance and renal functional injury. Entecavir plus adefovir was administered in month 106, resulting in decreased hepatitis B virus load, normal hepatic function, and stabilized creatinine clearance. As a result of rebounded viral load and significantly declining creatinine clearance, tenofovir plus entecavir was administered in month 133. After eight weeks, undetectable hepatitis B virus DNA, normal hepatic function and improved creatinine clearance were present. Compared with combination therapy with adefovir plus entecavir, tenofovir plus entecavir showed a potent antiviral effect for multidrug resistance and minimized renal injury.
In chronic hepatitis B patients with kidney transplantation, sequential monotherapy with antiviral agents with low barriers to resistance should be avoided, and initial therapy with entecavir is a better option. Combination therapy with tenofovir plus entecavir in this setting with multidrug resistance is safe and effective.
Available from: Tomasz I Michalak
- "Recent statistics indicate that up to one-third of the global population has evidence of exposure to HBV (WHO, 2008). This may indicate that over 90% of those exposed carry HBV asymptomatically, at levels which are not readily detectable by the current clinical laboratory tests, but which can be often 1994; Bläckberg & Kigg-Ljunggren, 2001; reviewed in Michalak 2000; Michalak et al., 2007; Pontisso et al., 2008; Coffin et al., 2011a, 2011b). On the other hand, the ability of WHV, which is a close relative of HBV, to infect and propagate in cells of the immune system has been well documented (Korba et al., 1988; Michalak et al., 1999; Michalak et al., 2004, 2007; reviewed in Michalak 2000, 2004; Mulrooney-Cousins & Michalak, 2007). "
Available from: Tomasz I Michalak
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ABSTRACT: The characterization of hepatitis B virus (HBV) quasispecies in different compartments in liver transplant (LT) recipients may be helpful in optimizing prophylaxis regimens. The aims of this study were to evaluate liver, peripheral blood mononuclear cells (PBMC), and plasma samples for HBV and to compare the quasispecies in hepatic and extrahepatic sites in LT recipients on long-term prophylaxis. For 12 patients followed for up to 15 years post-LT, liver, plasma, and PBMC samples [all HBV DNA-negative according to conventional polymerase chain reaction (PCR) assays] were evaluated for HBV DNA by a sensitive nested PCR method [covalently closed circular DNA (cccDNA) for liver and PBMC samples] and by the sequencing and phylogenetic analysis of polymerase quasispecies. For the 10 patients on prophylaxis with no clinical recurrence (median time post-LT = 15.5 months, range = 12-96 months), liver samples were HBV DNA-reactive in 9 of 10 cases, plasma samples were HBV DNA-reactive in 3 of 10 cases, and PBMC samples were HBV DNA-reactive in 2 of 7 cases (including 1 case with HBV cccDNA in PBMCs). The sequence analysis showed that all HBV clones had a wild-type (WT) sequence in the liver and PBMCs. In 2 patients with early HBV recurrence post-LT who were treated with nucleosides only, HBV DNA was detected in serum, PBMC, and liver samples, and HBV cccDNA was found in liver samples. An HBV lamivudine-resistant variant with an M204I mutation was identified in liver (70% and 18% of the clones) and plasma samples (100% of the clones), but a WT sequence was found in 70% and 100% of the PBMC clones. In conclusion, despite prophylaxis and the absence of HBV DNA in serum according to conventional assays, HBV is detectable in the serum, liver, and PBMCs of almost all patients, and this supports the use of continued anti-HBV therapy in this group. Antiviral drug-resistant variants are more frequent in the liver versus PBMCs, but both compartments are potential sources of reinfection.
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