New trends of HCV infection in China revealed by genetic analysis of viral sequences determined from first-time volunteer blood donors

Abstract

Recently, we studied hepatitis C virus (HCV) sera-prevalence among 559 890 first-time volunteer blood donors in China. From randomly selected 450 anti-HCV positive donors, we detected HCV RNA in 270 donors. In this study, we amplified HCV E1 and/or NS5B sequences from 236 of these donors followed by DNA sequencing and phylogenetic analysis. The results indicate new trends of HCV infection in China. The HCV genotype distribution differed according to the donors' region of origin. Among donors from Guangdong province, we detected subtypes 6a, 1b, 3a, 3b, 2a, and 1a at frequencies of 49.7%, 31.0%, 7.6%, 5.5%, 4.1%, and 2.1%, respectively. Among donors from outside Guangdong, we detected 1b, 2a, 6a, 3b, 3a, 6e, and 6n at frequencies 57.1%, 13.2%, 11.0%, 9.9%, 4.4%, 2.2%, and 2.2%, respectively. Although we found no significant differences among regions in age or gender, subtype 6a was more common (P < 0.001) in donors from Guangdong than those from elsewhere, whilst subtypes 1b (P < 0.02) and 2a (P < 0.001) were more frequent outside Guangdong. Disregarding origins, the male/female ratio was higher for subtype 6a-infected donors (P < 0.05) than for subtype 1b donors, whilst the mean age of subtype 2a donors was 8-10 years older (P < 0.05) than that for all other subtypes. Detailed phylogenetic analysis of our sequence data provides further insight into the transmission of HCV within China, and between China and other countries. The predominance of HCV 6a among blood donors in Guangdong is striking and mandates studies into risk factors for its acquisition.

Fig. 1

Subtype 1b phylogeny estimated from E1 region sequences (H77 positions: 869–1289). Subtype 1a sequence M62321 was used as an outgroup. Green circles label reference sequences from outside China, and red circles label sequences from this study. Sequences without a circle are Chinese isolates reported in other studies. Blue circles and dashed arrows represent the locations of clusters A and B, which are shown expanded in two boxes on the right. Three dashed circles indicate clusters C, D, and E and bootstrap support values are shown in italics. Scale bar represents 0.10 nucleotide substitutions per site.

Fig. 2

Subtype 1b phylogeny estimated from NS5B region sequences (H77 positions: 8276–8615). Subtype 1a sequence M62321 was used as an outgroup. All labels are the same as those described in the Fig. 1 legend. In addition, yellow circles represent unpublished sequences obtained by us from Chinese patients coinfected with HIV-1 [40], and dashed circles indicate clusters F and G.

Fig. 3

Subtype 6a phylogeny estimated from E1 region sequences (H77 positions: 869–1289). Subtype 6b sequence D84263 was used as an outgroup. All labels are the same as those described in the Fig. 1 legend. In addition, five dashed circles indicate clusters I, II, III, IV, and V. The box on the left contains a smaller phylogeny estimated from longer 510 nt sequences, which shows stronger bootstrap support for clusters I, II, and III.

Fig. 4

Subtype 6a phylogeny estimated from E1 region sequences (H77 positions: 8276–8615) Subtype 6b sequence D84263 was used as an outgroup. All labels are the same as those described in the Fig. 1 legend. In addition, three dashed circles indicate clusters I, II, and III. The box on the left contains a smaller phylogeny estimated from a longer alignment of concatenated E1 + NS5B sequences (870 nt), which shows very high bootstrap support for clusters I, II, and III.