Significance of mutations in the region coding for NS3/4 protease in patients infected with HCV genotype 1b.

Background: Fast hepatitis C virus (HCV) replication is one of the reasons for frequent changes in viral genome.

Objectives: The objective of this study was to evaluate the frequency and type of mutation in NS3/4 protease in patients with HCV genotype 1b and to determine the effect of the mutation on viral load, fibrosis stage, alanine aminotransferase (ALT) activity, and alpha-fetoprotein (AFP) level.

Material And Methods: The study included 46 treatment-naïve patients, infected with HCV genotype 1b. Mutations were analyzed after isolating HCV RNA, and then evaluating the compliance of the amino acid sequence, using 3500 Genetic Analyzer (Applied Biosystems, Foster City, USA). RNA fragment from nucleotide 1-181 encoding NS3/4 protease was subjected to analysis.

Results: Mutations were demonstrated in 65% of subjects. Changes in the protease region affecting resistance to treatment (T54, Q80, V158, M175, D186) were detected in 10.8% of patients. Substitution mutation at T72 was found most frequently - in 49.9% of cases. In 13% of patients, mutation at G86 was demonstrated, including G86P in 5 patients and G86S in 1 patient. In the group of patients with T72 mutation, viral load was significantly higher (1.3 × 106 IU/mL vs 1.0 × 105 IU/mL; p = 0.01), AFP level was higher and fibrosis level was lower (1.26 vs 2.17; p = 0.008) compared to the patients without the mutation. Cryoglobulinemia was observed in 74% of patients with mutation at position T72.

Conclusions: Natural mutations of the region coding for NS3/4 protease are found frequently in patients infected with genotype 1b, but they may cause resistance to antiviral agents only in 11% of patients. Changes were most frequently found at position T72. Mutations at position T72 are correlated with the cryoglobulinemia occurrence. This is a substitution mutation, accompanied by a high viral load, high ALT activity and AFP level, which may point to a more unfavorable influence of such a modified virus, compared to wild-type virus, onto pathological processes in the liver.