Analysis of low-density viral-genome containing particles of hepatitis B and C viruses

• Main Authors: Jhih-yuan Shieh, 謝志遠
• Other Authors: Kung-Chia Young
• Format: Others
• Language: en_US
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/67527847612264232068

碩士 === 國立成功大學 === 醫學檢驗生物技術學系 === 95 === Hepatitis B and C viruses (HBV) and (HCV), two major etiological agents of liver diseases, chronically infect millions of individuals in global population. Spherical HBV virion of 42 nm in diameter, known as Dane particle, has been well recognized, whereas rarely identified such HCV virion in plasma from infected patients. Circulating HCV particles exhibit a heterogeneous density. The low-density HCV fractions which may be due to association with β-lipoproteins have the highest infectivity among the other fractions with high densities. The purified low-density HCV RNA-containing particles were rich in triglycerides, containing at least apolipoprotein B, HCV-RNA, and HCV-core protein, which were named as lipo-viral particles (LVPs). However, the functional characteristics of LVPs remained unclear. In this study, salt gradient combined with ultracentrifugation was exploited to isolate the low-density fraction of plasma samples from blood bank donors who came under occult HBV or HCV infections. The results showed that the low-density fraction of HCV+ plasma contained a substantial amount of viral genome (48.3 ± 27.7% of total plasma HCV-RNA), but the corresponding fraction of HBV+ plasma had only a tiny amount (1.4 ± 0.8% of total plasma HBV-DNA). In a nuclease sensitivity assay, pretreatment of isolated HCV LVP with detergent triton X-100 could yield RNase-mediated degradation of HCV-RNA (decreased by 4.4 log10/ml, p=0.003). However, the HCV-RNA remained resistant to RNase digestion upon pretreatment with proteinase K. The results suggested that the lipid but not protein components of LVPs might be responsible to protect HCV-RNA. Furthermore, the size distribution of low-density particles was skew to the right in samples with HCV as compared to those with HBV or with neither HCV nor HBV. Additionally, nanogold conjugated HCV-specific oligonucleotide probes were used to detect HCV-RNA in the middle of LVP, suggesting that HCV genome might be incorporated into host lipoproteins. In conclusion, surrounding HCV-RNA by low-density lipoprotein particles might protect HCV genome in circulation. The results shed some light on HCV biology and hold potentials in the development of new anti-HCV strategy.