No detection of occult HBV-DNA in patients with various rheumatic diseases treated with anti-TNF agents: a two-year prospective study.

OBJECTIVES: The widespread use of tumour necrosis factor (TNF)-targeted therapies in patients with rheumatic, digestive and dermatologic diseases has been associated with reports of reactivation of HBV replication and ensuing hepatitis flares both in asymptomatic HBsAg carriers and in subjects with occult HBV infection. The aim of our work was to investigate in a two-year prospective study the potential for HBV reactivation in patients with inflammatory joint diseases undergoing anti-TNF treatment from a southern Mediterranean area. METHODS: Fifty-seven consecutive outpatients attending the Academic Unit of Rheumatology at the University of Palermo (12 with rheumatoid arthritis, 17 with psoriatic arthritis and 28 with ankylosing spondylitis) were enrolled in the study. HBV-DNA was tested by a standard quantitative assay in HBsAg-positive subjects and by an ad hoc highly sensitive PCR in HBsAg-negative patients performed at baseline and then every six months on the anti-TNF agent. RESULTS: Occult HBV-DNA was never detected in the 54 HBsAg negative subjects, regardless of their anti HBs/HBc status. All HBsAg positive patients, who were started on prophylactic lamivudine, remained HBV-DNA undetectable throughout the anti-TNF treatment. CONCLUSIONS: Even in an area of previously high HBV endemicity, where occult HBV infection is likely to have a high prevalence, treatment of rheumatological patients with anti-TNF drugs is safe in terms of its potential to reactivate HBV. Prophylaxis with lamivudine is sufficient to prevent reactivation in HBsAg carriers.

Phylogenetic analysis of isolates from new cases of HBV infection in Southern Italy.

The level of endemicity of hepatitis B virus (HBV) infections in Italy is low and genotype D infections predominant. New HBV strains may however be introduced as a result of movements of people from regions of high endemicity. The aim of the present study was to determine whether strains from new cases of acute hepatitis B detected in southern Italy were due to endemic or new HBV strains. We studied 34 isolates from patients with acute hepatitis B infection, and 35 from chronic hepatitis B patients. A phylogenetic analysis of preS/S region was done by comparing the sequences from the acute and chronic cases with references sequences. The study showed that 44% of strain from acute hepatitis B patients were of genotype A, 53% of genotype D, and 3% of genotype E. The molecular analysis of isolates from acute hepatitis B patients from Sicily showed a change in the local epidemiology of this infection, with an increase in HBV/A infections and a clustering effect for HBV D2, possibly correlated to immigration. The introduction of new genotypes , could have an effect on HBV-correlated diseases due to the different association between genotype, liver disease and response to antiviral therapy.

Vitamin D levels and IL28B polymorphisms are related to rapid virological response to standard of care in genotype 1 chronic hepatitis C.

BACKGROUND: Genotype 1 (G1) chronic hepatitis C (CHC) patients achieving a rapid virological response (RVR) on pegylated interferon (PEG-IFN) plus ribavirin have a high chance of sustained virological response (SVR), influenced by IL28B status, viral load, fibrosis and insulin resistance. We assessed whether 25-hydroxyvitamin D (25[OH]D) serum levels are linked to RVR and can be used together with IL28B to construct a pretreatment model to predict RVR. METHODS: A total of 117 consecutive patients with G1 CHC were evaluated by biopsy and anthropometric and metabolic measurements. 25(OH)D serum levels were measured by HPLC. IL28B rs12979860 and rs8099917 polymorphisms were also evaluated. All patients underwent antiviral therapy with PEG-IFN-α2a plus ribavirin. HCV RNA was assessed at baseline, week 4, week 12, at the end of therapy and after 6 months of follow-up. RESULTS: Mean ±SD 25(OH)D serum levels were 26.3 ±10.6 µg/l (range 8.0-58.0) and 31 (26.5%) patients had the rs12979860 CC polymorphism. RVR was achieved in 35 (29.9%) patients, and 32 (91.4%) of them had an SVR, compared to 26 of 82 (31.7%) without RVR. The rs12979860 CC polymorphism (OR 4.575, 95% CI 1.761, 11.889; P=0.002) and higher 25(OH)D levels (OR 1.055, 95% CI 1.010, 1.101; P=0.01) were independently associated with the achievement of RVR by multivariate analysis. The likelihood of RVR progressively increased from patients in the worst class (vitamin D<26.8 µg/l and TT/TC polymorphism; RVR 14.2%), to those with only one positive predictor (RVR 29.7% and 37.5%), and to those in the best class (vitamin D≥26.8 µg/l and rs12979860 CC polymorphism; RVR 73.3%). CONCLUSIONS: In patients with G1 CHC, 25(OH)D serum levels and IL28B status are independently associated with the likelihood to achieve RVR and SVR. When incorporated into a pretreatment predictive model they can assist in further discriminating patients with a high likelihood of achieving RVR and SVR.

Identification of human papillomavirus type 58 lineages and the distribution worldwide.

BACKGROUND: Human papillomavirus type 58 (HPV-58) accounts for a much higher proportion of cervical cancers in East Asia than other types. A classification system of HPV-58, which is essential for molecular epidemiological study, is lacking. METHODS AND RESULTS: This study analyzed the sequences of 401 isolates collected from 15 countries and cities. The 268 unique concatenated E6-E7-E2-E5-L1-LCR sequences that comprised 57% of the whole HPV-58 genome showed 4 distinct clusters. L1 and LCR produced tree topologies that best resembled the concatenated sequences and thus are the most appropriate surrogate regions for lineage classification. Moreover, short fragments from L1 (nucleotides 6014-6539) and LCR (nucleotides 7257-7429 and 7540-52) were found to contain sequence signatures informative for lineage identification. Lineage A was the most prevalent lineage across all regions. Lineage C was more frequent in Africa than elsewhere, whereas lineage D was more prevalent in Africa than in Asia. Among lineage A variants, sublineage A2 dominated in Africa, the Americas, and Europe, but not in Asia. Sublineage A1, which represents the prototype that originated from a patient with cancer, was rare worldwide except in Asia. CONCLUSIONS: HPV-58 can be classified into 4 lineages that show some degree of ethnogeographic predilection in distribution. The evolutionary, epidemiological, and pathological characteristics of these lineages warrant further study.

Hepatic steatosis and insulin resistance are associated with severe fibrosis in patients with chronic hepatitis caused by HBV or HCV infection.

BACKGROUND AND AIMS: Steatosis and insulin resistance (IR) are the major disease modifying in patients with chronic hepatitis C (CHC). Only few studies evaluated these features in patients with chronic hepatitis B (CHB). We aimed to assess the prevalence and the factors related to steatosis and IR in CHB patients, compared with CHC subjects, and to evaluate the potential association between these features and fibrosis severity. MATERIAL AND METHODS: One hundred and seventy consecutive patients with CHB (28 HBeAg positive, 142 HBeAg negative), were evaluated using liver biopsy and metabolic measurements and matched for sex, age and body mass index with 170 genotype 1 CHC patients. IR was defined if HOMA-IR>2.7. All biopsies were scored for grading and staging by Scheuer's score, and the steatosis was considered significant if ≥ 10%. RESULTS: The prevalence of significant steatosis was similar in both CHB and CHC patients (31 vs. 38%; P=0.14). IR rate was significantly higher in CHC than in CHB patients (42 vs. 26%; P=0.002). Severe fibrosis (F3-F4), at multivariate analysis, was independently associated with older age (OR 1.050, 95% CI 1.009-1.093), steatosis >10% (OR 4.375, 95% CI 1.749-10.943), and moderate-severe necroinflammatory activity (OR 8.187, 95% CI 2.103-31.875), regardless of HBeAg status, in CHB patients, and with older age (OR 1.080, 95% CI 1.028-1.136), IR (OR 2.640, 95% CI 1.110-6.281), steatosis >10% (OR 3.375, 95% CI 1.394-8.171), and moderate-severe necroinflammatory activity (OR 8.988, 95% CI 1.853-43.593) in CHC patients. CONCLUSIONS: CHB patients had high steatosis prevalence, similar to CHC controls, but lower IR rate. Both steatosis and IR in CHC, and only steatosis in CHB, are independently associated with fibrosis severity.

Variability of reverse transcriptase and overlapping S gene in hepatitis B virus isolates from untreated and lamivudine-resistant chronic hepatitis B patients.

BACKGROUND: The high degree of diversity of the hepatitis B virus (HBV) quasispecies in chronically infected individuals raises the possibility that HBV genetic variants favouring resistance to nucleoside/nucleotide analogues (NAs) might pre-exist to treatment. The aim of this study was to investigate the genetic variability of the entire HBV reverse transcriptase (RT) domain and of the overlapping S gene in a large series of untreated hepatitis B surface antigen carriers and in lamivudine (3TC)-resistant patients. METHODS: Sequencing analysis of the entire HBV RT domain of isolates from 100 untreated (treatment-naive group) and 59 3TC-resistant (3TC-resistant group) consecutive patients with chronic hepatitis B was performed. RESULTS: In the treatment-naive group, primary mutations known to cause resistance to NAs were not detected, but variably combined secondary/compensatory mutations were found in 46 (46%) patients. Moreover, four patients carried mutations that modified the S protein antigenicity. In the 3TC-resistant group, besides the primary 3TC-resistant mutations, various combinations of primary and secondary mutations conferring resistance to other NAs were detected in 41/59 (69.5%) patients. Importantly, the RT mutations induced by 3TC provoked stop codons in the overlapping S gene in two patients and modified the S protein antigenicity in another nine. CONCLUSIONS: This study shows that HBV mutants associated with resistance to NAs might already be present as the major infecting population in untreated patients, and that variants emerging under 3TC might also carry mutations favouring resistance to other NAs and/or potentially altering the S protein immunoreactivity.

Evaluating the risk of hepatitis B reactivation in patients with haematological malignancies: is the serum hepatitis B virus profile reliable?

BACKGROUND/AIM: Patients with an occult hepatitis B virus (HBV) infection undergoing deep immunosuppression are potentially at risk of HBV reactivation. In order to assess whether a polymerase chain reaction (PCR) assay for HBV DNA in serum could be used to predict the reactivation of an occult HBV infection, we performed a retrospective study in a cohort of Sicilian patients with oncohaematological diseases. METHODS: We studied by a highly sensitive ad hoc nested PCR for serum HBV DNA 75 HBsAg-negative oncohaematological patients requiring chemotherapy. RESULTS: Thirty-three patients (44%) were HBV seronegative (anti-HBc and anti-HBs negative) and 42 patients (56%) were HBV seropositive (anti-HBc and/or anti-HBs positive). Baseline serum HBV DNA was positive in nine out of 33 HBV-seronegative patients and in nine out of 42 HBV-seropositive patients (27.3 vs. 21.4%; P=NS). HBsAg seroconversion was observed in five out of 33 seronegative vs. six out of 42 seropositive patients (15 vs. 14%, P=0.9), and in five out of 18 HBV DNA-positive vs. six out of 57 HBV DNA-negative patients (27.7 vs. 10.6%P=0.11). Hepatitis C virus infection was found in 18 patients (24.3%), although with no correlation to HBV serological status, presence of serum HBV DNA or frequency of HBsAg seroconversion. CONCLUSIONS: In oncohaematological patients undergoing chemotherapy, highly sensitive serum HBV DNA testing at baseline has a 28% predictive ability to forecast HBsAg seroconversion in HBV DNA-positive patients, and a 90% ability to forecast persistent HBsAg negativity in HBV DNA-negative patients, a better performance than serological tests.

HCV genotypes in Sicily: is there any evidence of a shift?

The distribution of HCV strains in any area is characterized by a relative prevalence of one genotype, and a number of less prevalent types. In some Western countries a change from the prevalent HCV genotype 1 to genotypes 3 and 4 has been reported in the last decade. In order to assess possible variations of the distribution of HCV genotypes in Sicily, a southern region of Italy, a hospital-based cohort, collected prospectively, of 3,209 subjects with chronic HCV infection was surveyed, comparing the distribution of HCV genotypes during two consecutive periods, from 1997 to 2002 and from 2003 to 2007, according to age and gender. The results show that genotype 1b, which has been historically the most prevalent in Sicily, is still predominant, followed more distantly by genotypes 2 and 3a. However, a cohort effect for these genotypes was seen when comparing the two time periods. Genotype 1b decreased slowly over the last decade, due to the death of the people infected, leading to a proportional increase of the other genotypes. No evidence was found in support of a major increase in the prevalence of other genotypes, such as genotype 4, in relation to migration patterns.

Phylogenetic reconstruction of HCV genotype 1b dissemination in a small city centre: the Camporeale model.

Several seroepidemiological population-based surveys carried out in Italy have shown a high prevalence of hepatitis C virus (HCV) infection. Camporeale (CP), a small Sicilian town with a 10.4% prevalence of HCV mostly genotype 1b, probably represents a specific context, since intravenous drug addiction, and sexual promiscuity are almost absent. In order to reconstruct the pattern of introduction and diffusion of HCV in this ecological niche, the NS5 genomic region of 72 HCV genotype 1 isolates (39 from CP and 33 collected throughout Sicily) was amplified and sequenced. Sequences were aligned and analyzed by BioEdit, PAUP and BEAST, and their molecular evolution compared. Thirty-eight HCV genotype 1b isolates from CP were associated in a monophyletic "transmission cluster." By applying Monte Carlo Markov simulation, it was calculated that HCV was introduced between the end of the 1940s and the beginning of the 1950s. The phylogenetic distance between the CP cluster and other Sicilian isolates confirmed its uniqueness and the local diffusion from a common ancestor. The data obtained from classic phylogenetic analysis, combined with the application of the Bayesian analysis to the study of the coalescence of phylogenetic trees, have shown that, in CP, few HCV native strains have been transmitted in a limited length of time probably through iatrogenic routes, and then have not spread further.

Liver disease in chelated transfusion-dependent thalassemics: the role of iron overload and chronic hepatitis C.

Iron overload and hepatitis virus C infection cause liver fibrosis in thalassemics. In a monocentric retrospective analysis of liver disease in a cohort of 191 transfusion-dependent thalassemics, in 126 patients who had undergone liver biopsy (mean age 17.2 years; 58 hepatitis virus C-RNA positive and 68 hepatitis virus C-RNA negative) the liver iron concentration (median 2.4 mg/gr dry liver weight) was closely related to serum ferritin levels (R = 0.58; p<0.0001). Male gender (OR 4.12) and serum hepatitis virus C-RNA positivity (OR 11.04) were independent risk factors for advanced liver fibrosis. The majority of hepatitis virus C-RNA negative patients with low iron load did not develop liver fibrosis, while hepatitis virus C-RNA positive patients infected with genotype 1 or 4 and iron overload more frequently developed advanced fibrosis. Hepatitis virus C infection is the main risk factor for liver fibrosis in transfusion-dependent thalassemics. Adequate chelation therapy usually prevents the development of liver fibrosis in thalassemics free of hepatitis virus C-infection and reduces the risk of developing severe fibrosis in thalassemics with chronic hepatitis C.

Peg-interferon alone or combined with ribavirin in HCV cirrhosis with portal hypertension: a randomized controlled trial.

BACKGROUND/AIMS: Risks and benefits of antiviral therapy in HCV cirrhosis with portal hypertension are poorly known. METHODS: We performed a randomized controlled trial in 102 HCV patients with compensated cirrhosis and portal hypertension: 51 received 1 microg/kg/week of Pegylated-interferon alpha-2b and 51 Pegylated-interferon plus 800 mg/day of ribavirin up to 52 weeks. RESULTS: By intention-to-treat analysis, five patients on monotherapy and eleven on combination therapy achieved a sustained virological response (9.8% vs. 21.6%, p=0.06). The response was more frequent for genotypes 2 or 3 than genotype 1 (66.6% vs. 11.3%, p=0.001). Genotype 1, who had low viral load at start of therapy, were HCV-RNA negative at 4 weeks, and were adherent to the scheduled therapy had a higher probability of sustained virological response. Patients with sustained virological response had less disease events compared to nonresponders (6.2% vs. 38.3%, p=0.03 by log rank test) during follow-up. CONCLUSIONS: In HCV cirrhosis with portal hypertension Peg-interferon plus ribavirin is a feasible treatment. Although the rate of viral eradication is modest, tailoring by genotype and early viral response allows to keep patients on treatment who are more likely to have viral eradication. Patients with viral eradication have fewer disease complications during follow-up.

Different doses of consensus interferon plus ribavirin in patients with hepatitis C virus genotype 1 relapsed after interferon monotherapy: a randomized controlled trial.

AIM: To assess the efficacy of different schedules of consensus interferon (CIFN) plus ribavirin in retreating chronic hepatitis C patients who relapsed after recombinant interferon (rIFN) monotherapy. METHODS: Forty-five patients (34 males and 11 females) with chronic hepatitis due to hepatitis C virus (HCV) genotype 1 who relapsed after a previous course of rIFN monotherapy were randomized to receive 9 mug CIFN three times per week for 52 wk (group A, n = 22) or 18 mug CIFN three times per week for 52 wk (group B, n = 23) in combination with ribavirin 800 to 1200 mg daily for 52 wk (according to body weight). Virological response was evaluated at week 24 (EVR), at the end of treatment (ETR) and at 76 wk (SVR). RESULTS: By intention-to-treat analysis, subjects in group A had an EVR in 35% of cases, an ETR in 35% and a SVR in 27.3% of cases. Subjects in group B had an EVR in 32% of cases, an ETR in 35% and a SVR in 26.1% of cases. Treatment was stopped because of adverse effects (mostly intolerance) in 15 patients (6 in group A and 9 in group B). IFN dose reduction was needed in 2 patients (1 in group A and 1 in group B). Ribavirin dose was reduced in 2 patients in group A and 1 in group B respectively. Among the 15 subjects who received at least 80% of the intended schedule, the rate of SVR was 80% (6 in group A and 6 in group B). CONCLUSION: CIFN in combination with ribavirin when given to HCV genotype 1 relapsers after rIFN monotherapy obtains an unsatisfactory rate of sustained viral clearance independently of dosage of the drug. This may be due to its scarce tolerability.

HBV-DNA suppression and disease course in HBV cirrhosis patients on long-term lamivudine therapy.

In hepatitis B virus (HBV) cirrhosis patients on long-term lamivudine (LAM), the relationships between HBV suppression, development of viral resistance and disease outcome are unclear. We analysed the dynamic of serum HBV-DNA and its relationship with the clinical course of 59 patients (52 males, mean age 51.4 +/- 8.4 years, 12 HBeAg positive and 47 HBeAg negative, and 57 genotype D and two genotype A) with cirrhosis (45 in Child-Turcotte-Pugh class A) and high levels of serum HBV-DNA (median 14.7 x 10(7) genomes/ml) treated with LAM [median (range): 44 (15-78) months]. A total of 50 patient (84.7%) achieved a virological response (serum HBV-DNA negative by PCR) during the first 6 months of therapy, and nine (13.3%) achieved a reduction in viral load of > 3 log10. Mutations in the YMDD motif of HBV polymerase were documented in 26 patients [median (range) 18: (7-42) months]. At the time of the emergence of mutants, 22 patients had HBV-DNA < 10(5) genomes/ml and normal alanine aminotransferase (ALT) levels. The appearance of virological resistance was followed by an increase of HBV-DNA to > 10(5) genomes/ml and of ALT values in 19 out of 26 patients [median (range): 8 (3-19) months]. Event-free survival was significantly longer (P = 0.001) in patients who maintained virological suppression than in those who did not have a complete virological response or suffered a breakthrough. Patients with advanced cirrhosis were more likely to develop liver failure after the emergence of YMDD mutants. The risk of development of hepatocellular carcinoma in patients with compensated cirrhosis and YMDD mutations was maintained, regardless of HBV-DNA serum levels. Profound and maintained HBV-DNA suppression correlates with a better outcome. Early identification of LAM resistance mutations allows switching to other antivirals before liver decompensation or hepatocellular carcinoma development.

Hepatitis B virus reactivation and alemtuzumab therapy.

Reactivation of hepatitis B virus infection in subjects receiving cytotoxic treatment for heamatological malignancies occurs in 21-53% of chronic HBsAg carriers and in an unknown number of HBsAg negative subjects harbouring occult HBV infection. Immunotherapy with alemtuzumab, a humanized monoclonal antibody against CD52 epitopes on lymphocytes cells produces deep immunosuppression. We describe two subjects with chronic lymphocytic leukaemia and occult HBV infection who developed a virological and biochemical flare of hepatitis B following immunotherapy with alemtuzumab. One of them developed full blown hepatitis with seroreversion from anti-HBs to HBsAg after four weeks of alemtuzumab therapy. Lamivudine (100 mg die) achieved a complete clinical recovery and HBV-DNA clearance from blood within 8 weeks. The second patient (HBsAg and HBV-DNA seronegative, anti-HBs and anti-HBc positive before treatment) was kept under prophylaxis with lamivudine up to three months after alemtuzumab. Two months after withdrawal of lamivudine, clinical and laboratory features of acute hepatitis B developed. Lamivudine therapy was restarted and a prompt recovery was obtained with HBsAg and HBV-DNA clearance.

HVR-1 quasispecies modifications occur early and are correlated to initial but not sustained response in HCV-infected patients treated with pegylated- or standard-interferon and ribavirin.

BACKGROUND/AIMS: HVR-1 quasispecies composition and evolution were investigated in patients chronically infected with genotype 1b HCV, treated with PEG-IFN alpha 2b or STD-IFN alpha 2b plus RBV. METHODS: HVR-1 heterogeneity was assessed by calculating nucleotidic complexity, diversity, synonymous (S) and non-synonymous (NS) substitutions at baseline, after 4 weeks of therapy (T1) and at follow-up (T18). Evolution of viral quasispecies was analysed by constructing phylogenetic trees. RESULTS: No correlation of baseline viremia with heterogeneity was observed. Nucleotidic complexity was lower in patients showing early virological response, and tended to be inversely correlated to viral load decline at 4 weeks of treatment. In the majority of SR, profound changes of quasispecies composition occurred during 4 weeks of treatment, while in NR virtually no major changes of pre-therapy variants were observed. Relapse showed both patterns of quasispecies evolution. Virus quasispecies after follow-up was similar to that found at T1 in both Relapsers and NR patients. CONCLUSIONS: Baseline parameters of HVR-1 heterogeneity seem to be involved in the early response to treatment, and early response is associated with profound variations in the HVR-1 quasispecies. Viral quasispecies surviving early therapeutic pressure are most likely able to give rise to either virus rebound or persistence at T18.

IL-10 and TNF-alpha polymorphisms and the recovery from HCV infection.

Hepatitis C virus (HCV) infection becomes chronic in about 85% of infected individuals, whereas only 15% of infected people clear spontaneously the virus. It is conceivable that the host immunogenetic background influences the course of infection in term of recovery. Thus, in this study we have evaluated the effect of functionally relevant polymorphisms at tumor necrosis factor-alpha (TNF-alpha, i.e., 2 biallelic polymorphisms at nt -863 and nt-308 of the promoter) and interleukin-10 (IL-10) loci (i.e., 1 biallelic polymorphism at nt -1082 of the promoter), on the clearance of HCV infection. To this purpose, we compared 18 Sicilian patients who had spontaneously recovered from previous HCV infection with 42 Sicilian patients with current HCV infection and 135 Sicilian healthy patients. The results demonstrate a decreased frequency of the -863CC TNF-alpha promoter genotype (involved in high production of this pro-inflammatory cytokine) and an increased frequency of the -1082GG IL-10 promoter genotype (involved in high production of this anti-inflammatory cytokine) in patients recovered from HCV infection. The evaluation of combined TNF-alpha and IL-10 genotypes revealed a significant increase of the "anti-inflammatory genotype" (low-TNF/high-IL-10 producers) in resolved HCV infection group compared with patients with persistent HCV infection. On the whole, our findings suggest that a genetically determined control of the HCV-induced inflammatory response may play a role in the resolution of HCV infection.

ISDR pattern and evolution in patients with chronic hepatitis C treated with standard or PEG-IFN plus ribavirin.

The aim of the study was to characterize the interferon sensitivity determining region (ISDR) mutation pattern and its changes at 4 weeks of treatment in a population of patients infected with hepatitis C virus (HCV) genotype 1b receiving standard or PEG-IFN plus ribavirin (RBV), to find possible early correlates of therapy outcome. Forty-five patients with chronic hepatitis due to HCV 1b were treated by PEG-IFN-alpha2b (n=23) or IFN-alpha2b (n=22) plus RBV 1000-1200 mg/day. They were classified 24 weeks after stopping therapy as sustained responders (SR), relapsers (REL) or non-responders (NR). Sixteen patients were SR, 12 REL and 17 NR. ISDR mutations were evaluated by direct sequencing at baseline in all and after 4 weeks in patients with detectable viraemia (n=30). The frequency of the three ISDR types was 26.7% wild-type, 64.4% intermediate-type and 8.9% mutant-type, without significant difference in their frequency in SR, REL and NR, independent of IFN formulation. Average numbers of mutations in SR, REL and NR were 1.88 +/- 0.54, 1.33 +/- 0.33 and 0.94 +/- 0.25, respectively, P>0.05. The baseline number of ISDR mutations was not related to the extent of viral load decline in the first month of therapy. Sequence analysis of ISDR region performed 4 weeks after starting therapy revealed qualitative or quantitative changes of ISDR sequence in only seven patients, without correlation with response. Thus, in our patients the baseline pattern of ISDR was unrelated to treatment outcome. Selection towards a dominant IFN-resistant strain did not occur under standard or PEG-IFN plus RBV.