[The influence of hepatitis B virus polymorphism on the progression of chronic liver disease]. / Wplyw polimorfizmu wirusa zapalenia watroby typu B na przebieg choroby u osób przewlekle zakazonych.

Hepatitis B virus (HBV) infection is one of the major human health problems worldwide. It is estimated that chronic HBV infection affects more than 350 million people globally. It is one of the leading causes of liver cirrhosis and hepatocellular carcinoma. High genetic variability is a characteristic feature of HBV as the viral polymerase lacks proofreading activity. The nucleotide substitution rate for HBV is 10-fold higher than for other DNA viruses. Genetic variations of HBV influence the clinical outcome of HBV infection. There are eight genotypes of hepatitis B virus (A-H) that have a distinct geographical distribution. There is clinical significance of HBV genotype in terms of disease activity, risk of progression to cirrhosis, the development of hepatocellular carcinoma and response to antiviral treatments. Moreover, polymorphism in HBV viral polymerase influences the development of HBV mutants resistant to nucleotide analogue treatment that is a consequence of treatment failure.

Determination of lamivudine-resistant variants of hepatitis B virus by denaturing gradient gel electrophoresis: a novel approach to monitoring drug resistance.

BACKGROUND: A DGGE-based assay for hepatitis B virus (HBV) drug-resistance monitoring was designed and checked for feasibility. It detects mutations within the YMDD motif related to lamivudine resistance. MATERIAL/METHODS: The YMDD motif of HBV polymerase was amplified by the set of primers designed in this study. DGGE analysis of the amplicons was performed on 9% polyacrylamide gels containing a 20-40% gradient of urea plus formamide and electrophoresis was performed. DNA sequencing was performed using a standard protocol. RESULTS: Based on the DGGE pattern of previously sequenced HBV variants, a reference ladder consisting of bands was constructed within and near the YMDD motif of HBV with excellent resolution. The genotypes of all the fragments included in the ladder were confirmed by sequencing after DGGE analysis. The flexibility of DGGE was demonstrated by the ability to add more bands to the migration ladder when new variants were discovered during the analysis of patient specimens. Clinical samples from HBV-infected patients were also used to demonstrate the performance of this approach. CONCLUSIONS: This preliminary feasibility study of HBV drug-resistance monitoring by means of DGGE shows the potential advantage of this approach for low-cost screening for viral drug resistance in clinical settings. The presented example can be extended to detect other mutations related to drug resistance in the HBV genome as well as other viruses.

[HBV gene variants and polymerse gene mutations in children with chronic hepatitis B in the course of the antiviral therapy]. / Genotypy HBV oraz mutacje genu polimerazy HBV u dzieci z przewleklym zapaleniem watroby typu B w przebiegu leczenia lamiwudyna.

UNLABELLED: THE AIM OF THE STUDY was to evaluate the occurrence of HBV genotypes and the emergence of polymerase gene mutations in children with chronic hepatitis B in the course of the lamivudine therapy. MATERIAL AND METHODS: eighteen children (aged from 6 to 15 years, mean age 11,8 years, 10 boys and 8 girls) with chronic hepatitis B were included in the study. All patients were treated with 100 mg lamivudine tablets given daily orally for 12-16 months. All amino acid substitutions within HBV polymerase were detected by PCR amplification and direct sequencing HBV genotypes and polymerase gene mutations were determined by comparing the sequences in the overlapping PollS genes with published sequences, available in GenBank. RESULTS: HBVgenotyping showed the presence of genotype A in 17 children and genotype H in one. No change of HBV genotype was noted in any of the studied patients as the sequencing of HBV DNA was repeated during the lamivudine therapy. The presence of lamivudine-resistance mutations involving the YMDD motif was detected in 5 patients. Four children had YVDD mutation, while in one child YIDD mutation was detected. YIDD mutation appeared to be the single one in the viral polymerase gene, while YVDD mutations in four patients were accompanied by other changes at amino acid sequence of the HBV polymerase: rtL180M, rtN124D and rtL164M. CONCLUSIONS: 1) Genotype A was predominant in the studied population of patients. 2) The risk of the emergence of drug-resistant HBV polymerase mutations is high and increases in the course of the lamivudine therapy. 3)Drug-resistant mutations in the YMDD motif are accompanied by other amino acid substitutions in the viral polymerase of unclear clinical significance.

Genetic variability of hepatitis B virus isolates in Poland.

There is very limited knowledge about the genetic variability of HBV strains circulating in the population of Polish chronically infected HBV patients. The aim of this study was to analyse the phylogenetic relatedness and polymorphism in some functional domains of HBV genome among chronically infected patients from northern Poland. Fifty-one serum samples were included to analysis of HBV genomes due to the viral load sufficient for DNA preparation and sequencing. The sequences of the rt polymerase/S and preC/BCP regions of those isolates were analysed, compared to genome sequences of different variants of HBV from GenBank database and genetic relatedness of Polish genotypes to known reference strains was estimated. A phylogenetic tree of 41 analysed genotype A isolates as well as 8 genotype D strains was constructed showing relationship to know reference strains. Two isolates, initially classified as genotype F turned to be related to genotype H, newly described genotype deriving from genotype F, a very rare genotype in Europe. HBV genotypes' distribution pattern in Poland and phylogenetic relatedness seems to be different from our Eastern neighbours. Due to the fact that Poland is still ethnically uniform country, it is interesting to explore molecular epidemiology of HBV infections in our population.

Distribution of HBV genotypes and mutants among hepatitis B infected patients from northern Poland.

Hepatitis B virus (HBV) infection is one of the major global epidemiological problems. The aim of our study was to determine the distribution of HBV genotypes in Poland since the data concerning the spread of HBV viruses in the central-eastern region of Europe is still very limited. HBV DNA was extracted from 58 serum samples. To quantify the level of HBV DNA the Roche Amplicor HBV Monitor Assay was used. To genotype and assign HBV subtypes DNA sequencing methods were performed. The HBV virus from 43 serum samples from hepatitis B infected patients was genotype A (74.1%), 12 cases had genotype D (20.7%), and 3 had the rare in Europe genotype F (5.2%). Prediction of HBV serological subtypes based on HBsAg sequencing showed almost 100% occurrence of subtype adw2 in the group of genotype A samples, three different subtypes in genotype D (ayw2, ayw3, and ayw4), and equal distribution of subtype adw4q- in all 3 cases of genotype F, also the most prevalent subtype in the Amerindians. Our results coincide with the general European HBV prevalence. However, HBV genotype F, which is not a common genotype in European countries, was detected and so was relatively high occurrence of genotype D, which may reflect historical and ethnical migration events in Poland in the past.