Molecular Epidemiology of Hepatitis C Virus Genotype 4 Isolates in Egypt and Analysis of the Variability of Envelope Proteins E1 and E2 in Patients with Chronic Hepatitis

摘要

We analyzed hepatitis C virus (HCV) genotype 4 isolates circulating in the Alexandria District (Egypt) in terms of genetic divergence and the presence of different subtypes. Hypervariable region 1 (HVR1) and the NH2 region of the E2 protein were characterized, and the heterogeneity of subtype 4a isolates was evaluated by analyzing epitope frequencies, immunoproteasome prediction, and possible glycosylation patterns. The heterogeneity of the nucleotide sequences was greater than that found in previous studies, which reported only subtype 4a. Subtype 4a was most common (78% of cases), yet four new subtypes were found, with subtype 4m representing 11% of the cases and the other three subtypes representing another 11%. Substantial heterogeneity was also found when the intrasubtype 4a sequences were analyzed. Differences in the probability of glycosylation and in the positions of the different sites were also observed. The analysis of the predicted cytotoxic-T-lymphocyte epitopes showed differences in both the potential proteosome cleavage and the prediction score. The Egyptian isolates in our study also showed high variability in terms of the HVR1 neutralization epitope. Five of these isolates showed amino acid substitutions never previously observed (a total of six positions). Four of these residues (in four different isolates) were in positions involved in anchoring to the E2 glycoprotein core and in maintaining the HVR1 conformation. The results of this study indicate that HCV genotype 4 in Egypt is extremely variable, not only in terms of sequence, but also in terms of functional and immunological determinants. These data should be taken into account in planning the development of vaccine trials in Egypt.