Analysis of GB virus C markers in families over three generations.
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GB virus C (GBV-C) markers were analyzed in two to three generations in three families with documented vertical transmission of GBV-C. None of the maternal grandparents had GBV-C markers, whereas the male spouses had GBV-C envelope 2 antibodies. Evidence was found for intrafamilial transmission but not for GBV-C transmission over three generations. (+info)
The RNA-dependent RNA polymerases of different members of the family Flaviviridae exhibit similar properties in vitro.
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The virus-encoded RNA-dependent RNA polymerase (RdRp), which is required for replication of the positive-strand RNA genome, is a key enzyme of members of the virus family Flaviviridae. By using heterologously expressed proteins, we demonstrate that the 77 kDa NS5B protein of two pestiviruses, bovine viral diarrhoea virus and classical swine fever virus, and the 100 kDa NS5 protein of the West Nile flavivirus possess RdRp activity in vitro. As originally shown for the RdRp of hepatitis C virus, RNA synthesis catalysed by the pestivirus and flavivirus enzymes is strictly primer-dependent in vitro. Accordingly, initiation of RNA polymerization on homopolymeric RNAs and heteropolymeric templates, the latter with a blocked 3'-hydroxyl group, was found to be dependent on the presence of complementary oligonucleotide primer molecules. On unblocked heteropolymeric templates, including authentic viral RNAs, the RdRps were shown to initiate RNA synthesis via intramolecular priming at the 3'-hydroxyl group of the template and 'copy-back' transcription, thus yielding RNase-resistant hairpin molecules. Taken together, the RdRps of different members of the Flaviviridae were demonstrated to exhibit a common reactivity profile in vitro, typical of nucleic acid-polymerizing enzymes. (+info)
Mutational analysis of the GB virus B internal ribosome entry site.
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GB virus B (GBV-B) is a recently discovered hepatotropic flavivirus that is distantly related to hepatitis C virus (HCV). We show here that translation of its polyprotein is initiated by internal entry of ribosomes on GBV-B RNA. We analyzed the translational activity of dicistronic RNA transcripts containing wild-type or mutated 5' nontranslated GBV-B RNA (5'NTR) segments, placed between the coding sequences of two reporter proteins, in vitro in rabbit reticulocyte lysate and in vivo in transfected BT7-H cells. We related these results to a previously proposed model of the secondary structure of the GBV-B 5'NTR (M. Honda, et al. RNA 2:955-968, 1996). We identified an internal ribosome entry site (IRES) bounded at its 5' end by structural domain II, a location analogous to the 5' limit of the IRES in both the HCV and pestivirus 5'NTRs. Mutational analysis confirmed the structure proposed for domain II of GBV-B RNA, and demonstrated that optimal IRES-mediated translation is dependent on each of the putative RNA hairpins in this domain, including two stem-loops not present in the HCV or pestivirus structures. IRES activity was also absolutely dependent on (i) phylogenetically conserved, adenosine-containing bulge loops in domain III and (ii) the primary nucleotide sequence of stem-loop IIIe. IRES-directed translation was inhibited by a series of point mutations predicted to stabilize stem-loop IV, which contains the initiator AUG codon in its loop segment. A reporter gene was translated most efficiently when fused directly to the initiator AUG codon, with no intervening downstream GBV-B sequence. This finding indicates that the 3' limit of the GBV-B IRES is at the initiator AUG and that it does not require downstream polyprotein-coding sequence as suggested for the HCV IRES. These results show that the GBV-B IRES, while sharing a common general structure, differs both structurally and functionally from other flavivirus IRES elements. (+info)
Perspectives for the treatment of infections with Flaviviridae.
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The family Flaviviridae contains three genera: Hepacivirus, Flavivirus, and Pestivirus. Worldwide, more than 170 million people are chronically infected with Hepatitis C virus and are at risk of developing cirrhosis and/or liver cancer. In addition, infections with arthropod-borne flaviviruses (such as dengue fever, Japanese encephalitis, tick-borne encephalitis, St. Louis encephalitis, Murray Valley encephalitis, West Nile, and yellow fever viruses) are emerging throughout the world. The pestiviruses have a serious impact on livestock. Unfortunately, no specific antiviral therapy is available for the treatment or the prevention of infections with members of the Flaviviridae. Ongoing research has identified possible targets for inhibition, including binding of the virus to the cell, uptake of the virus into the cell, the internal ribosome entry site of hepaciviruses and pestiviruses, the capping mechanism of flaviviruses, the viral proteases, the viral RNA-dependent RNA polymerase, and the viral helicase. In light of recent developments, the prevalence of infections caused by these viruses, the disease spectrum, and the impact of infections, different strategies that could be pursued to specifically inhibit viral targets and animal models that are available to study the pathogenesis and antiviral strategies are reviewed. (+info)
The entire nucleotide sequence of two hepatitis G virus isolates belonging to a novel genotype: isolation in Myanmar and Vietnam.
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A novel genotype of hepatitis G virus (HGV) was recently identified in sera of subjects from countries in South-East Asia. These isolates were recovered from serum of Myanmarese (designated HGV-MY14) and Vietnamese (designated HGV-VT48) subjects, respectively. To characterize the viral genome in more detail, the full-length nucleotide sequence of the two different HGV isolates belonging to the novel genotype was cloned. Both HGV isolates were composed of 9228 nt and had a single open reading frame spanning 8529 nt and encoding 2843 aa residues. The isolates differed from previously reported HGV/GBV-C isolates types 1 to 3 by 13-15% (nucleotide sequence) and 4-6% (amino acid sequence). The putative core region of both isolates was not clearly identifiable as it consisted of only 16 aa residues. Based on phylogenetic analysis of full-length genome sequences and 5'-UTR sequences, HGV-MY14 and HGV-VT48 isolates can be classified as a novel genotype, designated type 4. (+info)
Prevalence of GB virus C/Hepatitis G virus infection among various populations in Surabaya, Indonesia, and identification of novel groups of sequence variants.
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A molecular epidemiological study was performed to investigate the prevalence of GB virus C/hepatitis G virus (GBV-C/HGV) infection among various populations in Surabaya, Indonesia. The prevalence of GBV-C/HGV RNA, determined by reverse transcription-PCR for a portion of the NS3 region of the viral genome, was 2.7% (4 of 150) among randomly collected blood donor sera, which were all negative for both hepatitis B virus surface antigen and antibodies against hepatitis C virus (HCV). On the other hand, the prevalence among anti-HCV-positive blood donors was 17.8% (13 of 73), with the ratio being significantly higher than that observed with the anti-HCV-negative blood donors (P < 0.001). A high prevalence of GBV-C/HGV infection was also observed among patients with chronic liver disease, such as chronic hepatitis (5.7%), liver cirrhosis (11. 5%), and hepatocellular carcinoma (7.0%), and patients on maintenance hemodialysis (29.0%). No correlation was observed between GBV-C/HGV viremia and serum alanine aminotransferase levels in the populations tested, suggesting the possibility that GBV-C/HGV does not cause apparent liver injury. Phylogenetic analysis of sequences of a portion of the 5' untranslated region and the E1 region of the viral genome identified, in addition to a previously reported then novel group of GBV-C/HGV variants (group 4), another novel group of variants (group 5). This result suggests that GBV-C/HGV can be classified into at least five genetic groups. GBV-C/HGV isolates of group 4 and group 5 were each shown to comprise approximately 40% of the total Indonesian isolates. (+info)
Detection of TT virus DNA and GB virus type C/Hepatitis G virus RNA in serum and breast milk: determination of mother-to-child transmission.
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To investigate the vertical transmission of the newly described TT virus (TTV), serum and breast milk samples from 46 women as well as sera from their 47 newborns were examined for the presence of TTV DNA by PCR. TTV DNA was detected in 47.8% (n = 22) of the women. All but one child born to these women were also viremic for TTV from the first sample onward. TTV DNA was found in 73.9% (n = 17) of the breast milk samples derived from TTV viremic mothers. The one TTV-negative child born to a viremic mother remained negative during follow-up, although it was breast-fed. Our data show that TTV is highly effectively transmitted from mothers to their children during pregnancy. Although the majority of breast milk samples from viremic mothers are positive by TTV PCR, there is no need to discourage women from breast-feeding, because most children are TTV viremic even before breast-feeding begins. (+info)
Age related prevalence of hepatitis G virus in South Africans.
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AIM: To investigate the age related prevalence of hepatitis G virus (HGV) infection and its mode of transmission in relation to hepatitis B (HBV) and C (HCV) co-infection in South African blacks. METHODS: Reverse transcriptase polymerase chain reaction was performed to detect active infection, using primers for the 5'-NCR, NS5a, and NS3 regions. Antibodies to HGV envelope-2 protein (anti-E2), which measures past infection, were also sought. RESULTS: The overall prevalence of active infection was 116/580 (20%). A higher prevalence was noted in HBsAg carriers (28/106; 26.4%) and HCV positive subjects (25/82; 30.5%). In contrast to developed countries, active and past infection was seen in 12.9% and 12.1% of the general population, respectively (subjects negative for HBsAg and anti-HCV markers and with normal alanine aminotransferase values), with a total prevalence of 21.1% (52/248). Viraemia and anti-E2 were almost mutually exclusive. The distribution of viraemia by age was: < or = 15 years, 20/223 (9.0%); 16-35 years, 42/147 (28.6%); > or = 36 years, 37/151 (24.5%), with a significant difference (p = 0.001) in age related prevalence. A similar trend was observed for the prevalence of past infection in the general population. CONCLUSIONS: HGV infection begins in childhood and increases with age in South Africa, but transmission is largely independent of HBV and HCV. No association was found between HGV viraemia and hepatitis, or with co-infection with either HBV or HCV. (+info)