Structure and Molecular Virology

Hepatitis C virus (HCV) is present in the host with multiple variants generated by its error prone RNA-dependent RNA polymerase. Little is known about the initial viral diversification and the viral life cycle processes that influence diversity. We studied the diversification of HCV during acute infection in 17 plasma donors, with frequent sampling early in infection. To analyze these data, we developed a new stochastic model of the HCV life cycle. We found that the accumulation of mutations is surprisingly slow: at 30 days, the viral population on average is still 46% identical to its transmitted viral genome. Fitting the model to the sequence data, we estimate the median in vivo viral mutation rate is 2.5×10−5 mutations per nucleotide per genome replication (range 1.6–6.2×10−5), about 5-fold lower than previous estimates. To confirm these results we analyzed the frequency of stop codons (N = 10) among all possible non-sense mutation targets (M = 898,335), and found a mutation rate of 2.8–3.2×10−5, consistent with the estimate from the dynamical model. The slow accumulation of mutations is consistent with slow turnover of infected cells and replication complexes within infected cells. This slow turnover is also inferred from the viral load kinetics. Our estimated mutation rate, which is similar to that of other RNA viruses (e.g., HIV and influenza), is also compatible with the accumulation of substitutions seen in HCV at the population level. Our model identifies the relevant processes (long-lived cells and slow turnover of replication complexes) and parameters involved in determining the rate of HCV diversification.

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Pathogenesis of hepatitis C: HCV consensus 2007

Viso¹

2007

Braz J Infect Dis

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The chronic hepatitis C virus (HCV) infects approximately 130 million people worldwide [1]. It is estimated that approximately 15% of HCV-infected individuals eliminate the virus spontaneously, that 25% develop a mild form of the disease, and that 60% develop the chronic progressive form [2]. The elimination or persistence of HCV infection depends on the balance between the effectiveness, specificity and rapidity of the innate and adaptive immune responses, as well as on the HCV replication rate [3]. Persistence of HCV can also be caused by infection at privileged (extrahepatic) sites, viral inhibition of antigen presentation, selective immune suppression, negative regulation of HCV gene expression, viral mutations, immune exhaustion of T cells and the incomplete differentiation of memory T cells [4,5].Fibrosis is the principal complication of chronic hepatitis C, and it is estimated that 20% of patients develop cirrhosis over a period of 10, 20 or 30 years [2,6]. The progression of fibrosis increases morbidity and mortality in chronic hepatitis C [7], since it can lead to death due to complications caused by cirrhosis or hepatocarcinoma [2].Various studies have associated the progression of fibrosis in hepatitis C with diverse factors such as: the kinetics and pathogenicity of HCV; host-HCV interaction; intrinsic host factors such as demographic profile, body mass index and diabetes mellitus; host exposure to external factors; and the form of HCV acquisition. Life Cycle and Pathogenicity of HCVBelonging to the Flaviviridae family, HCV is a small enveloped virus [8]. Its genome consists of one RNA molecule that is composed of two terminal regions, 5'-and 3'-untranslated regions, and between these there is a single open reading frame that encodes a polyprotein with approximately 3000 amino acids. This polyprotein cleaves at the N-terminal side of three structural proteins, the nucleocapsid (core), envelope 1 (E1) and envelope 2 (E2), all of which are involved in the architectural organization of HCV. At the carboxylterminal side, the polyprotein cleaves to six nonstructural proteins, NS2, NS3, NS4 (NS4A and NS4B), NS5 (NS5A and NS5B) and NS6, which are responsible for the life cycle of the virus [9].After entering a susceptible host, HCV invades, infects and replicates within the blood stream, repeating the process in various tissues, as well as in peripheral B and T lymphocytes, as it proceeds to the liver by tropism, passing through various tissues such as those of the pancreas, thyroid, adrenal glands, spleen and bone marrow [10][11][12]. Since HCV can also directly infect the lymphatic tissue, its stimulation can lead to the development of B-cell lymphomas [13]. It is known that the liver is the principal site of HCV replication, and various studies have shown that this virus infects approximately 10% of hepatic cells [5]. Infection with HCV at extrahepatic sites can promote the appearance of HCV variants [14,15], thereby decreasing the chance that the immune system will recognize the virus.To enter the host ...

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Structure and Molecular Virology

Cited by 3 publications

References 334 publications

Busca de fatores genéticos associados à resposta ao tratamento do HCV genótipo 3.

Busca de fatores genéticos associados à resposta ao tratamento do HCV genótipo 3.

Quantifying the Diversification of Hepatitis C Virus (HCV) during Primary Infection: Estimates of the In Vivo Mutation Rate

Pathogenesis of hepatitis C: HCV consensus 2007

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