Molecular characterisation of HCV genotype 4 isolates circulating in Italy

The characteristics of genotype 4 subtype variability of HCV isolates circu lating in Italy were studied. The viral isolates were identified from 736 H CV-RNA positive sera originated from seroepidemiological studies undertaken in 4 different regions of North, South Italy and Sardinia. 24 out of 28 ge notype 4 isolates (86%) were classified by phylogenetic analysis of E1 geno me region (915-1128) as belonging to subtype 4d (Neighbour Joining Method). Three isolates classified as subtype 4a were detected in haemophilic patie nts, possibly related to infections from blood products. One isolate classi fied as a new subtype derived from an Eritrean patient subjected to haemodi alysis. Very high genome homogeneity (mean 4.3%) was shown by genetic compa risons (DNA dist programs Phylip Package) for all the 4d isolates relative to the studies performed in Veneto, Calabria and Sardinia and originated fr om subjects from the general population and outpatients (19 subtype 4d isol ates out of 24). In the 3 studies different prevalence rates of HCV genotyp e 4 (3.1%, 1.3%, 14% respectively) were found. In contrast a considerable d egree of heterogeneity, both intragroup and with the other groups (mean 8.2 % and 8.7%, respectively) was observed among subtype 4d isolates identified in the patients of a haemodialysis centre in Apulia region. In conclusion the subtype 4d of genotype 4 was highly prevalent and endemic in Italy. An elevated level of viral heterogeneity was observed in one study carried out in a region of Southern Italy. This can be related to a longer period of p ast endemicity of this genotype and to a high level of exposure to reinfect ions in particular categories of patients such as haemodialysis patients. J . Med. Virol. 62:84-90, 2000. (C) 2000 Wiley-Liss, Inc.