Wait-listed (n ϭ 226) or post-liver transplantation (n ϭ 241) chronic hepatitis B (CHB) patients with lamivudine-resistant hepatitis B virus (HBV) were treated with adefovir dipivoxil for a median of 39 and 99 weeks, respectively. Among wait-listed patients, serum HBV DNA levels became undetectable (Ͻ1,000 copies/mL) in 59% and 65% at weeks 48 and 96, respectively. After 48 weeks, alanine aminotransferase (ALT), albumin, bilirubin, and prothrombin time normalized in 77%, 76%, 60%, and 84% of wait-listed patients, respectively. Among posttransplantation patients, serum HBV DNA levels became undetectable in 40% and 65% at weeks 48 and 96, respectively. After 48 weeks, ALT, albumin, bilirubin, and prothrombin time normalized in 51%, 81%, 76%, and 56% of posttransplantation patients, respectively. Among wait-listed patients who underwent on-study liver transplantation, protection from graft reinfection over a median of 35 weeks was similar among patients who did (n ϭ 34) or did not (n ϭ 23) receive hepatitis B immunoglobulin (HBIg). Hepatitis B surface antigen was detected on the first measurement only in 6% and 9% of patients who did or did not receive HBIg, respectively. Serum HBV DNA was detected on consecutive visits in 6% and 0% of patients who did or did not receive HBIg, respectively. Treatment-related adverse events led to discontinuation of adefovir dipivoxil in 4% of patients. Cumulative probabilities of resistance were 0%, 2%, and 2% at weeks 48, 96, and 144, respectively. In conclusion, adefovir dipivoxil is effective and safe in wait-listed or posttransplantation CHB patients with lamivudine-resistant HBV and prevents graft reinfection with or without HBIg. Liver Transpl 13:349-360, 2007.

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BackgroundBecause of the extreme genetic variability of hepatitis C virus (HCV), we analyzed whether specific HCV-genotypes are differently prone to develop resistance to linear and macrocyclic protease-inhibitors (PIs).MethodsThe study includes 1568 NS3-protease sequences, isolated from PI-naive patients infected with HCV-genotypes 1a (N = 621), 1b (N = 474), 2 (N = 72), 3 (N = 268), 4 (N = 54) 5 (N = 6), and 6 (N = 73). Genetic-barrier was calculated as the sum of nucleotide-transitions (score = 1) and/or nucleotide-transversions (score = 2.5) required for drug-resistance-mutations emergence. Forty-three mutations associated with PIs-resistance were analyzed (36A/M/L/G-41R-43S/V-54A/S/V-55A-Q80K/R/L/H/G-109K-138T-155K/Q/T/I/M/S/G/L-156T/V/G/S-158I-168A/H/T/V/E/I/G/N/Y-170A/T-175L). Structural analyses on NS3-protease and on putative RNA-models have been also performed.ResultsOverall, NS3-protease was moderately conserved, with 85/181 (47.0%) amino-acids showing <1% variability. The catalytic-triad (H57-D81-S139) and 6/13 resistance-associated positions (Q41-F43-R109-R155-A156-V158) were fully conserved (variability <1%). Structural-analysis highlighted that most of the NS3-residues involved in drug-stabilization were highly conserved, while 7 PI-resistance residues, together with selected residues located in proximity of the PI-binding pocket, were highly variable among HCV-genotypes. Four resistance-mutations (80K/G-36L-175L) were found as natural polymorphisms in selected genotypes (80K present in 41.6% HCV-1a, 100% of HCV-5 and 20.6% HCV-6; 80G present in 94.4% HCV-2; 36L present in 100% HCV-3-5 and >94% HCV-2-4; 175L present in 100% HCV-1a-3-5 and >97% HCV-2-4). Furthermore, HCV-3 specifically showed non-conservative polymorphisms (R123T-D168Q) at two drug-interacting positions. Regardless of HCV-genotype, 13 PIs resistance-mutations were associated with low genetic-barrier, requiring only 1 nucleotide-substitution (41R-43S/V-54A-55A-80R-156V/T: score = 1; 54S-138T-156S/G-168E/H: score = 2.5). By contrast, by using HCV-1b as reference genotype, nucleotide-heterogeneity led to a lower genetic-barrier for the development of some drug-resistance-mutations in HCV-1a (36M-155G/I/K/M/S/T-170T), HCV-2 (36M-80K-155G/I/K/S/T-170T), HCV-3 (155G/I/K/M/S/T-170T), HCV-4-6 (155I/S/L), and HCV-5 (80G-155G/I/K/M/S/T).ConclusionsThe high degree of HCV genetic variability makes HCV-genotypes, and even subtypes, differently prone to the development of PIs resistance-mutations. Overall, this can account for different responsiveness of HCV-genotypes to PIs, with important clinical implications in tailoring individualized and appropriate regimens.

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Long-term immunoprophylaxis with anti-HBs immunoglobulins (HBIgH BV reinfection after liver transplantation for HBVrelated cirrhosis is frequent in the absence of immunoprophylaxis and is associated with poor prognosis, resulting from the development of cirrhosis, fibrosing hepatitis, or fulminant hepatitis. 1-2 The introduction of the long-term use of anti-HBs immune globulins (HBIg) has allowed the reduction of graft reinfection to acceptable levels, resulting in survival rates comparable with, or even better than, those of other indications. [3][4][5] This passive immunoprophylaxis strategy is therefore currently considered the standard treatment to prevent HBV reinfection after liver transplantation for HBV-related cirrhosis. 6 Yet, using this approach, posttransplant HBV recurrence still occurs in 10% to 30% of cases, possibly depending on a variety of factors, such as the amount of HBIg infused, the route and frequency of administration, and the minimum trough levels of anti-HBs maintained during various periods after transplant. 6 According to current recommendations, HBIg should be administered indefinitely after transplant. This is associated with a number of problems, including the limited availability of HBIg, the possible emergence of HBV envelope protein mutations, 7,8 and/or other adverse events, 9,10 and, most importantly, the extremely high costs. 6 Whatever is the prophylactic regimen used (which varies remarkably from one Center to another) and the cost differences of HBIg preparations between U.S. and most Western European countries, the expenses of post-transplant HBIg administration range between $25,000 and $120,000 per year, thus exceeding in a few years those of an uncomplicated transplant.New prophylactic strategies to prevent posttransplant HBV recurrence are therefore needed. New approaches under evaluation include the combination of lower doses of HBIg with antivirals, such as lamivudine, 11,12 and HBV vaccination, as proposed in the recent provocative study of Sanchez-Fueyo et al. 13 from Spain.