Experimental Studies On New Hepatitis-associated Viruses(HGV And TTV)

Hepatitis 0 virus (HGV) and transfusion-transmitted virus (TTV) are newly identified hepatitis-associated viruses in 1995 and 1997 respectively. HGV is a positive strand RNA virus with a genome of about 9400nt in length, and classified as a member of Flaviviridae. In the past several years, the genomic structure and transmission routes of HGV have been studied clear, but some questions as follows remain to be resolved. 1. The pathogenicity of HGV: HGV has been thought of as a new hepatitis virus because of its detection in the patients of non-A-to-E hepatitis, subsequent researches showed doubt on the pathogenicity of HGV. 2. Tissue tropism of HGV: There are two opinions on the replication site of HGV, one is hepatropism, and the other is lymphotropism, most of the researches are apt to the latter. 3. Infection cell model of HGV: Although HGV could be replicated and expressed in PBMCs, interferon-resistant Daudi cells, PH5CH, MT-2C cells, stable cell model has not been established. TTV is a negative strand DNA virus. Its genomic structure of it shows notable variation and produced different isolates. In this study, we have done some experimental studies on HGV and TTV. Section I : Experimental studies of hepatitis G virus We had constructed the full length HOV eDNA clone pHGVqz, which was deposited in GenBank with the accession number AFO8 1782. In order to illustrate the pathogenicity and replication site of HGV, we prepared the full-length HGV RNA transcripts and studied the pathogenicity of it to macaques in this study. We also preliminarily established a cell model for HGV infection. 1. Infection of macaques with full-length HGV RNA transcripts Two healthy macaques BK1 5 and BY1 were intrahepatic inoculated with HGV RNA transcripts, positive sera from them were intravenously inoculated into the other two healthy macaques BS1 and BM1, and BBI was inoculated with positive sera from BM1. Sera were collected weeklylbi-weekly from infected macaques to detect the ALT level, HGV RNA and anti-HGV. All of the 5 macaques had slightly abnormal ALT level during the infectious periods except macaque BS 1, but individual differences were existed in the experimental macaques. HGV RNA became positive in Bl 5 and BY1 at 1St and 8th weeks respectively, and could exist for about 27 weeks. HGV RINA in the other three macaques also became positive. Anti-HGV was detectable in all of the infected macaques. Liver biopsies were taken regularly to detect the histological changes and expression of HGV in the hePatocytes. All of the macaques showed slightly inflaxnInatory changes inliver. The results of boohistochemiStry with MAb showed tha HGV E2 proteinmainly expressed in the cytoplasm of hepatocytes, and also could be exPressed in heartand spleen cells. HGV rnRNA was detected in the liver of BKl5, BYl and BM1. Theelectron microscopy of BKl5 indicated that HGV could produce tWo types of virus-likeparticles in the dissae of hepatcocyte. One tyPe of pbocle was arraned in crystal styleswith the diameter of about 25-30nm, and the other about 67 nm in diameter was usuallyrounded in the space of disse.HGV specific probe tagged with fluorescence was used to derect the dynamicchanges of HGV in serum of BKl5, and confirmed the qualitative results. Heart, liver,pancreas, spleen, kidney tissue of BKl5, liver tissues of BYl, BMl and BBlwere alldetected for HGV plus and minus strand by quantitative PCR methods. Plus and minusHGV RNA strands were found in the livers of experimental macaques excePt BSl,indicating tha HGV cou1d replicate in the lha tissue of macaques. HGV could raplicatein the heart and spleen as well in BKl5, Which suggests tha HGV isolates with bothhepatotropism and...