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.