Molecular heterogeneity and new subtypes of HCV genotype 4

The subtype distribution of HCV genotype 4 was studied in two different Afr ican countries, Egypt and Tanzania. The HCV isolates were obtained from epi demiological studies involving, respectively, 135 hepatopatic patients and 1043 pregnant women and outpatients. Sequence comparison and phylogenetic a nalysis of the NS5b genome region (nt 8327-8499) were performed. Fourteen o ut of 18 isolates from Egypt, but only 3 out of 6 isolates from Tanzania cl ustered in the same branch of subtype 4a. Three new proposed subtypes have been identified. The first includes 1 isolate from Egypt (EGY15); the secon d, 2 isolates from Egypt (EGY193 and EGY44)and 2 isolates from Tanzania (D7 76, D61); and the third, 1 isolate from Egypt (EGY47) and 1 isolate from Ta nzania (D70). These isolates cluster in branches different from any other, corresponding to a known subtype of genotype 4. In conclusion, remarkable g enetic heterogeneity has been found among genotype 4 isolates simultaneousl y circulating in a restricted area. This was particularly observed in the s tudy performed in Tanzania. Potential concern about the sensitivity of diag nostic assays and possible implications in the development of future vaccin es have been stressed.