Evolutionary study of the HVR1 E2 in chronic HCV infection

ALFONSO VICTORIA; FLICHMAN DIEGO MARTÍN; KOTT VERÓNICA LAURA; SOOKOIAN SILVIA; CAMPOS RODOLFO

París

Simposio; VIII International Symposium on Hepatitis C and Related Viruses; 2001

The European Association for the Study of the Liver

Aim: to study the population dynamics of HVR1-E2 in chronically HCV infected IFN alpha treated patients in order to analyze the evolutionary mechanisms of this genomic region.to study the population dynamics of HVR1-E2 in chronically HCV infected IFN alpha treated patients in order to analyze the evolutionary mechanisms of this genomic region. Methods: serum samples of three HCV chronically-infected patients were taken before (I), right after (II) and 14-22 months following a six-month IFN treatment (III). HVR1 region from samples were amplified by RT-PCR and sequenced before and after cloning and at least 10 clones were analyzed from each sample. The mean genetic distances (gd) within and between samples were calculated. Phylogenetic analyses were performed according to the neighbor-joining method. All bootstrap values considered were higher than 83.serum samples of three HCV chronically-infected patients were taken before (I), right after (II) and 14-22 months following a six-month IFN treatment (III). HVR1 region from samples were amplified by RT-PCR and sequenced before and after cloning and at least 10 clones were analyzed from each sample. The mean genetic distances (gd) within and between samples were calculated. Phylogenetic analyses were performed according to the neighbor-joining method. All bootstrap values considered were higher than 83. Results: patient A showed two subpopulations in sample I, (Ia, 5 clones and Ib, 7 clones). They were markedly different, with a gd (Ia-Ib) of 26.2%. Population II appeared to be phylogenetically related to Ia, but the high gd value (Ia-II) of 11.0% over 9 months, suggests that population II resulted from the selection of a minor subpopulation related to Ia rather than from the successive selection of point mutations. Population III was phylogenetically related to Ib, which was not detected in II, with a gd (Ib-III) of 5.0% along 31 months. This suggests a successive selection of point mutations from the Ib subpopulation.patient A showed two subpopulations in sample I, (Ia, 5 clones and Ib, 7 clones). They were markedly different, with a gd (Ia-Ib) of 26.2%. Population II appeared to be phylogenetically related to Ia, but the high gd value (Ia-II) of 11.0% over 9 months, suggests that population II resulted from the selection of a minor subpopulation related to Ia rather than from the successive selection of point mutations. Population III was phylogenetically related to Ib, which was not detected in II, with a gd (Ib-III) of 5.0% along 31 months. This suggests a successive selection of point mutations from the Ib subpopulation. Patient B, likewise, had two subpopulations in sample I (Ia, 10 clones and Ib, 3 clones). Population II was phylogenetically related to Ia, and population III was to Ib. There was a high degree of similarity between sequences of Ia and sequences of II (gd: 2.0%), and also between Ib and III (gd: 0.1%) thus indicating that populations II and III arise from the previous populations Ia and Ib, respectively. In patient C population I was homogeneous. Variants isolated in II, with a gd (I-II) of 19.5% over 10 months were likely to result from the selection of an undetected subpopulation in I. Virus population III was phylogenetically related to II variants, and presented a gd (II-III) of 6.7% along 22 months. This meager value suggests that population III results from continuous selection of point mutations from II. Conclusions: we propose herein that the evolution of HVR1 E2 region is more likely driven by shifts in viral populations due to the selection of early and markedly different subpopulations than by a continuous mechanism, related to the successive selection of point mutations.we propose herein that the evolution of HVR1 E2 region is more likely driven by shifts in viral populations due to the selection of early and markedly different subpopulations than by a continuous mechanism, related to the successive selection of point mutations.