engleski

HEPATITIS B ESCAPE MUTANTS AMONG PATIENTS WITH DIFFERENT TYPES OF CHRONIC HEPATITIS B INFECTION

Hepatitis B virus (HBV) infection, inflammatory liver disease that affects more than 2 billion people in the world, remains as the viral infection with the highest risk of transmission by transfusion. Despite vaccination and highly preventive measures, the disease eradication is still very slow. This is the consequence of the extreme variability of HBV which leads to the generation of new viral variants with mutations which impair hepatitis B surface antigen (HBsAg) detection. The research presented here in this study was determination of S gene (codes for the HBsAg) mutations in patients chronically infected with hepatitis B virus with different stages of liver disease. HBV S gene mutations afford HBV variants a distinct survival advantage, permitting the mutant virus to escape from the immune system. They are often induced under immunosupression (vaccines or hepatitis B immune globulin therapy, HBIg). The effect of viral load, genotypes, subgenotypes, serotypes and serological profiles were evaluated considering duration of treatment and illness. Two groups of patients were selected ; one with decompensate cirrhosis or hepatocellular carcinoma, and the second one was the group of patients with chronic active hepatitis with and without therapy. Amplification of target HBV-DNA region were carried out by nested polymerase chain reaction (PCR) using selected primers, corresponded to the conserved regions among the different genotypes, allowing the distinction of HBV genotypes. The products of nested PCR were sequenced, using the second-round primers. The obtained sequences were then submitted to the Blast program in order to determine their similarity to other HBV strains deposited in GenBank. Phylogenetic analysis showed that most of the mutants were clustered in the genotype D (82.6%), mostly subgenotypes D3 and D2, and genotype A (15, 2%), subgenotype A2, which showed the expected distribution of genotypes. Remaining samples presented either F genotype or mixed D genotypes. Subtype/serotype distribution were mostly ayw3 (30%), ayw2 (41, 3%) and adw2 (15, 2%) which is in the correlation with the obtained genotypes. S gene mutations were observed in both groups ; frequency in group I was with the higher mutation rate in the major hydrophilic region (MHR) of region of the S gene (44, 2%) and group II 32, 7%. In the group I (HCC and cirrhosis), 45 mutations previously described have been found and two new mutations were identified, G71N and N206Y. In the group II (treated and untreated chronic patients), 18 previously described mutations have been found. Changes in the S gene showed of course impact on the severity of the disease, but numerous mutations in the S gene outside the MHR region warn us about the risk of the emergence of vaccine escape mutants. Also, genotyping of chronic HBV infections could help identify patients at risk of disease progression and to determine the right therapy.

hepatitis B virus; mutants; chronic hepatitis B infection

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