Dynamics Of Hepatitis Research Articles

Changes in risk behavior and dynamics of hepatitis C virus infections among young drug users in Amsterdam, the Netherlands

To elucidate the character and magnitude of the hepatitis C virus (HCV) epidemic among drug users in Amsterdam, 197 young drug users from the period 2000 to 2004 were compared with 215 counterparts from 1985 to 1989. Although injection risk behavior and HCV seroprevalence decreased sharply over time, HCV seroprevalence remains high (44%) among young drug users who have ever injected. Phylogenetic analysis shows that current HCV infections originate from diversification of strains already circulating in the past, but also from the recent introduction of new subtypes. HCV subtypes 1a and 3a remain the most prevalent among drug users in Amsterdam, but other subtypes such as 4d and 2b have entered the population. In conclusion, both the unpopularity of injecting drug use and the success of prevention campaigns are likely to be responsible for the decline in the seroprevalence of HCV and increased median time to seroconversion. Treatment of those infected chronically, in combination with the continuation of prevention programs, might decrease future HCV transmission.

Hepatitis C virus quasi-species dynamics predict progression of fibrosis after liver transplantation.

The dynamics of hepatitis C virus (HCV) quasi species in the E2 region may correlate with the course of infection after orthotopic liver transplantation (OLT). Thirty-four patients who underwent transplantation for HCV-related cirrhosis were studied. Serum and liver samples were available before OLT and at 1 week, 4 months, and 1 year after OLT. Patients were divided into group 1 (Knodell/Ishak fibrosis stage [FS] at 1 year, <2) and group 2 (FS at 1 year, > or =2). Complexity was estimated by the number of bands in a single-strand conformational polymorphism assay, whereas diversity was measured by Shannon entropy (SE) and median mobility shift (MMS) values derived from the heteroduplex mobility assay. Diversity dynamics were measured at transmission (before OLT vs. 1 week after OLT) and after OLT (1 week after OLT vs. 1 year after OLT). Complexity was higher in group 1 patients than in group 2 patients before OLT (P<.02) and at 1 week after OLT (P<.04). Diversity decreased in group 1 at transmission, as measured by either SE (P<.01) or MMS (P<.04). However, diversity increased in this group after OLT, as measured by SE (P<.03) or MMS (P<.02). FS at 1 year after OLT correlated with transmission changes, as measured by SE (r=0.642, P<.0001) and MMS (r=0.443, P<.04), and with post-OLT changes (for SE: r=-0.583, P<.01; for MMS: r=-0.536, P<.01). HCV complexity and diversity in the E2 region correlated with the severity of recurrence of HCV infection after OLT. Increased diversity of quasi species at transmission correlated with a higher FS at 1 year. However, increased diversity of quasi species in the post-OLT period correlated with a lower FS at 1 year. The dynamics of HCV quasi species in patients who undergo transplantation are predictive of outcome.

Dynamics of hepatitis C virus quasispecies turnover during interferon-alpha treatment.

Interferon-alpha (IFN) has been shown to accelerate the evolution of hepatitis C virus (HCV) variants (quasispecies) in nonresponder patients. Different sensitivities of HCV variants to IFN are discussed as a possible mechanism. In the present study, quasispecies were investigated in detail by a newly established and validated direct solid-phase sequencing of the hypervariable region 1 (HVR1), during the initial 3 months of IFN therapy. According to single strand conformation polymorphism (SSCP) analysis, 14 of 26 (54%) virologic nonresponders with quasispecies evolution were identified. Six representative patients with SSCP changes were selected for frequent HVR1 sequencing. Pre-existing variants were identified by cloning and sequencing of the pretreatment serum HCV sample. In one patient the major type was substituted by a minor variant within 3 days of treatment while in the majority of patients the pretreatment major type did not decline before days 26-57 of treatment. Total serum HCV RNA levels remained constant in all patients. In conclusion, although quasispecies evolution during IFN therapy is common, it occurs after a wide range of time intervals after initiation of therapy. Thus, nonresponse to IFN cannot exclusively be explained by changes in the quasispecies.

Dynamics of hepatitis C virus quasispecies turnover during interferon alfa treatment

Dynamics of hepatitis C virus quasispecies turnover during interferon alfa treatment

Timing of reinfection and mechanisms of hepatocellular damage in transplanted hepatitis C virus-reinfected liver.

Pathogenic mechanisms and dynamics of hepatitis C virus (HCV) reinfection in orthotopic liver transplantation (OLT) are poorly defined. This study focuses on these aspects by studying 55 frozen biopsy specimens from transplant recipients with various histological diagnoses obtained from 4 days to 4 years post-OLT and 10 patients with HCV-related chronic hepatitis. The percentage of HCV-infected hepatocytes, number and distribution of CD8 and natural killer cells, and rates of hepatocellular apoptosis and proliferation were quantified by immunohistochemistry. HCV antigens were detected in 37% of biopsy specimens obtained within 20 days and 90% of biopsy specimens obtained from 21 days to 6 months after OLT. The number of HCV-infected hepatocytes was never less than 40% in acute hepatitis specimens and never greater than 30% in the other cases. Hepatocellular apoptosis was high in biopsy specimens of acute hepatitis and moderate in those from transplant recipients with normal histological characteristics, but still greater than in specimens of chronic active hepatitis. Proliferation correlated significantly with apoptosis. Lymphocyte infiltration was high and similar among cases of acute hepatitis, chronic hepatitis, and rejection. These data: (1) show that the detection of liver HCV antigens is sensitive enough to be used in clinical practice as a diagnostic tool to detect infection of the transplanted liver and might be useful, combined with conventional histological evaluation to detect hepatitic damage, for therapeutic decision making; (2) suggest direct cytotoxicity of HCV, as well as immunologic mechanisms possibly prevalent in chronic hepatitis and rejection, at least in the phase of acute massive liver infection; and (3) show that hepatocellular apoptosis and regeneration might be active enough to lead to replacement of the entire transplanted liver in 2 weeks.

The dynamics of hepatitis C virus binding to platelets and 2 mononuclear cell lines

Hepatitis C virus (HCV) binds to platelets in chronically infected patients where free HCV constitutes only about 5% of total circulating virus. Free HCV preferentially binds to human mononuclear cell lines but free and complexed virus binds equally to platelets. The extent of free HCV binding to human Molt-4 T cells (which express CD81) and to human promonocytic U937 cells or to platelets (which do not express CD81) was similar. The binding of free HCV to the cell lines was saturated at a virus dose of 1 IU HCV RNA per cell but binding to platelets was not saturable. Human anti-HCV IgG, but not anti-CD81, markedly inhibited HCV binding to target cells in a dose-dependent manner. Human antibodies to HCV hypervariable region 1 of E2 glycoprotein partially inhibited viral binding to target cells. Recombinant E2 also inhibited viral binding to target cells in a dose-dependent manner, with the efficacy of this decreasing in the rank order of Molt-4 cells more than U937 cells more than platelets. In contrast to HCV, recombinant E2 bound to Molt-4 cells to an extent markedly greater than that apparent with U937 cells or platelets. These results suggest that the binding of HCV to blood cells is mediated by multiple cell surface receptors and that recombinant E2 binding may not be representative of the interaction of the intact virus with target cells.

The dynamics of hepatitis C virus binding to platelets and 2 mononuclear cell lines

AbstractHepatitis C virus (HCV) binds to platelets in chronically infected patients where free HCV constitutes only about 5% of total circulating virus. Free HCV preferentially binds to human mononuclear cell lines but free and complexed virus binds equally to platelets. The extent of free HCV binding to human Molt-4 T cells (which express CD81) and to human promonocytic U937 cells or to platelets (which do not express CD81) was similar. The binding of free HCV to the cell lines was saturated at a virus dose of 1 IU HCV RNA per cell but binding to platelets was not saturable. Human anti-HCV IgG, but not anti-CD81, markedly inhibited HCV binding to target cells in a dose-dependent manner. Human antibodies to HCV hypervariable region 1 of E2 glycoprotein partially inhibited viral binding to target cells. Recombinant E2 also inhibited viral binding to target cells in a dose-dependent manner, with the efficacy of this decreasing in the rank order of Molt-4 cells more than U937 cells more than platelets. In contrast to HCV, recombinant E2 bound to Molt-4 cells to an extent markedly greater than that apparent with U937 cells or platelets. These results suggest that the binding of HCV to blood cells is mediated by multiple cell surface receptors and that recombinant E2 binding may not be representative of the interaction of the intact virus with target cells.

Mutations in the E2-PePHD and NS5A region of hepatitis C virus type 1 and the dynamics of hepatitis C viremia decline during interferon alfa treatment

Both a double-stranded RNA-dependent protein kinase (PKR)-phosphorylation homology domain (PePHD) within the E2 protein and a PKR-binding domain within the nonstructural 5A (NS5A) protein of hepatitis C virus (HCV) genotype 1 isolates inhibit the function of the interferon alfa (IFN-α)-induced antiviral effector protein PKR in vitro. We investigated whether the mutational pattern of the E2 region (codons 618-681, including PePHD) of 81 HCV genotype 1-infected patients (HCV-1b [n = 54], HCV-1a [n = 27]) influences the response to IFN-α. Initial viral decline (ΔHCV RNA) was determined at week 1 hereby covering the effector reactions of IFN-α-mediated first phase and the immune-mediated second phase. ΔHCV RNA less than 50% (group 1); ΔHCV RNA greater than 50% but less than 90% (group 2); and ΔHCV RNA ≥90% (group 3) were differentiated. The PePHD region was highly conserved; the few mutations (5 patients) did not correlate with ΔHCV RNA or sustained virologic response to IFN-α. Within the flanking regions before and after PePHD (codons 618-681) 72 of 81 patients (89%) had 2.6 ± 0.17 mutations (median, 3; range, 1-8) that did not correlate with treatment response. Sequence analysis of the NS5A protein (codons 2,209-2,274, including interferon sensitivity determining region [ISDR]) in 39 of 81 patients showed a higher mean number of mutations in the ISDR (codons 2,209-2,248) in groups 2 (1.28 ± 0.43 [n = 18]) and 3 (1.89 ± 0.54 [n = 9]) than in group 1 (0.67 ± 0.19 [n = 12]; P = .049 group 1 vs. 3) and a mutant type ISDR ( e.g., ≥4 mutations) was significantly more frequent in sustained virologic responders than in nonresponders or relapsers (2 of 4 [50%] vs. 2 of 35 [6%]; P = .045). Thus, NS5A appears to be functionally relevant in IFN-α-induced effector reactions. (Hepatology2000;32:1386-1395.)

Dynamics of hepatitis C virus quasispecies turnover during interferon-a treatment

Dynamics of hepatitis C virus quasispecies turnover during interferon-a treatment

Hepatitis C Kinetics: Mathematical Modeling of Viral Response to Therapy

Mathematical models have been used to study the dynamics of HIV. Using these same principles, the dynamics of hepatitis C virus (HCV) are reviewed during interferon (IFN) therapy. After initiating IFN treatment, there is an IFN dose-dependent exponential decline in viral RNA levels within the first 48 hours. This rapid 1.0 to 2.0 log decline was best explained by an effect of IFN in inhibiting viral production with a varying degree of effectiveness. By applying mathematical principles, viral serum half-life was estimated to be 3.0 hours and viral production rat was calculated to be 1.0 x 10(12) virions per day. After this rapid first-phase decline there was a slower second phase decline in viral levels that was highly variable between subjects. This phase was dependent on the rate of elimination of HCV-infected liver cells. The rapidity of the second phase proved to be the best predictor of early viral clearance. The use of these models to understand the life cycle of viruses and their response to therapy is reviewed.

Dynamics of hepatitis C viremia after plasma exchange

Background/Aims: The dynamics of hepatitis C viremia after perturbation by plasma exchange was addressed in two infected patients with symptomatic cryoglobulinemia. This approach may offer an alternative to studying patients treated with antivirals in order to understand the dynamics of hepatitis C virion exchange among different compartments in vivo. Methods: Plasma exchange sessions were conducted every 24 h for 3 consecutive days; hepatitis C virus RNA copy numbers were evaluated in sequential plasma samples collected before (−24, −12, −8, and 0 h) and at short intervals (at 1, 3, 6, and 12 h) after each session. Results: After each plasma exchange session viremia dropped by 45.3–93.3% in patient 1, and by 60.5–72.7% in patient 2, paralleling (or, in some cases, exceeding) the amount of fluid exchanged. No mobilization of cell-free hepatitis C virus from extra-vascular sites was documented during the 2-h plasma exchange. The dynamics of hepatitis C viremia after each procedure was also evaluated. Pre-plasma exchange levels were restored within 3–6 h in both patients, and the mean doubling times of residual viremia were 4.6 h and 4.5 h for patients 1 and 2, respectively. Conclusions: The results, in agreement with recent evidence indicating that the turnover of hepatitis C virions is a highly dynamic process, extend previous evaluations by documenting that large amounts of newly-produced virions are introduced into the vascular compartment within a few hours of the drop in hepatitis C viremia caused by plasma exchange.

Clinical implications of hepatitis C viral kinetics

Antiviral treatment of patients with chronic hepatitis C can perturb the steady-state of virus production and clearance. From serial measurements of changes in viremia, kinetic information on the dynamics of hepatitis C virus (HCV) replication can be obtained. After a delay of about 9 h due to interferon-α pharmacokinetics, the decline of viremia in patients treated with interferon-α is characterized by a concave shape. In the first phase (day 1) a rapid dose-dependent decline in viral load is observed. The second phase viral decline (≥day 2) shows a much slower decline with no or less pronounced differences between the applied interferon-α schedules. While a first phase decline can be observed in almost all patients treated with interferon-α, non-responders typically reveal no further decline of viremia during the second phase. Kinetic analysis showed that combination therapy with interferon-α plus ribavirin has no direct synergistic antiviral effect in the initial 4 weeks of treatment of HCV-infected patients with 6 MU IFNα three times per week. Calculations revealed a minimum virus production and clearance per day in patients with chronic hepatitis C of approximately 10 10–10 12 virions per day and an in vivo half-life of the virus in the order of a few hours. The high turnover rates of HCV explain the rapid generation of viral diversity and the opportunity for viral escape from the host immune surveillance and antiviral therapy. The implications derived from HCV kinetics comprise the consideration of more aggressive initial dosing regimens (especially daily doses), the possibility to optimize therapy individually not only according to pretreatment parameters but also according to the initial decline of viral load and the perception that eradication of the virus will rely on the half-life of infected cells.

Molecular characterization and dynamics of hepatitis C virus replication in human fetal hepatocytes infected in vitro.

The molecular features of hepatitis C virus (HCV) replication in human fetal hepatocytes (HFHs) were addressed in this study. Using a competitive reverse-transcription polymerase chain reaction (RT-PCR) assay for the quantitation of HCV-RNA molecules, the highest level of viral replication was detected 30 days' postinfection. At this time point, viral particles of 41 to 45 nm in diameter accumulated in the cell cytoplasm. Their density in cell extracts and culture medium was distributed between heavy (1.180-1.360 g/cm3) and light fractions (1.105-1.050 g/cm3) of a sucrose gradient, while, in the serum inoculum, they had a positive fraction at 1.180 g/cm3. In infected HFHs, minus-strand HCV RNA was observed in fractions displaying a sedimentation coefficient of 28 S to 18 S, while plus-strand HCV RNA showed a peak restricted to the 21 S fraction; the HCV RNA of serum inoculum had a sedimentation coefficient of 38 to 40 S, which revealed the presence of HCV RNA of unique positive polarity. The 21 S RNA fraction of cell extracts was resistant to 20 minutes of RNase I digestion, while the same incubation time totally inactivated a comparable amount of HCV RNA purified from the serum inoculum, revealing the presence of completely and/or partially double-stranded HCV-RNA molecules in the infected cells. Detection in HFHs of replicative forms and replicative intermediates suggests that the dynamic profile of HCV replication in these cells is similar to that described in other flaviviruses. (Hepatology 1997 Nov;26(5):1328-37)

Molecular characterization and dynamics of hepatitis C virus replication in human fetal hepatocytes infected in vitro.

The molecular features of hepatitis C virus (HCV) replication in human fetal hepatocytes (HFHs) were addressed in this study. Using a competitive reverse-transcription polymerase chain reaction (RT-PCR) assay for the quantitation of HCV-RNA molecules, the highest level of viral replication was detected 30 days' postinfection. At this time point, viral particles of 41 to 45 nm in diameter accumulated in the cell cytoplasm. Their density in cell extracts and culture medium was distributed between heavy (1.180-1.360 g/cm3) and light fractions (1.105-1.050 g/cm3) of a sucrose gradient, while, in the serum inoculum, they had a positive fraction at 1.180 g/cm3. In infected HFHs, minus-strand HCV RNA was observed in fractions displaying a sedimentation coefficient of 28 S to 18 S, while plus-strand HCV RNA showed a peak restricted to the 21 S fraction; the HCV RNA of serum inoculum had a sedimentation coefficient of 38 to 40 S, which revealed the presence of HCV RNA of unique positive polarity. The 21 S RNA fraction of cell extracts was resistant to 20 minutes of RNase I digestion, while the same incubation time totally inactivated a comparable amount of HCV RNA purified from the serum inoculum, revealing the presence of completely and/or partially double-stranded HCV-RNA molecules in the infected cells. Detection in HFHs of replicative forms and replicative intermediates suggests that the dynamic profile of HCV replication in these cells is similar to that described in other flaviviruses.

Dynamics of hepatitis B virus infection in vivo

Background/Aims: Information on the kinetics of the pretreatment steady-state of HBV can be obtained from serial measurements of serum hepatitis B virus (HBV) DNA concentrations following lamivudine ((−)enantiomer of 3′-thiacytidine)-induced perturbation of the balance between virus production and clearance. Methods: In a placebo-controlled, dose-ranging trial, lamivudine (5 to 600 mg per day) was administered for 4 weeks to 17 patients with chronic replicative hepatitis B. Serum HBV DNA levels were quantified by standard liquid hybridization techniques. The time-dependent concentrations of serum HBV DNA following lamivudine administration were subjected to iterative least-squares regression in order to obtain kinetic data on HBV life-time and viremia. Results: In patients with stable HBe-antigen positive chronic hepatitis B responding to lamivudine, HBV DNA declined exponentially with a half-life of approximately 2–3 days. The minimum virus production and clearance per day in patients with chronic hepatitis B was calculated to be 6.09×10 11 virions/day (range 0.26 to 21.06×10 11 virions/day). Compared to the HBeAg levels before treatment, relative amounts of HBeAg were 1.00±0.16 and 0.96±0.20 at days 22 and 28 of treatment, respectively. Four weeks after termination of lamivudine treatment, the relative amount of HBeAg was 1.04±0.19. Conclusions: The half-life of HBV in chronically infected patients is longer and in vivo turnover rates are higher compared to recently published data on the human immunodeficiency virus type 1 and the hepatitis C virus. The constant expression of HBeAg observed in the present study during a 28-day lamivudine treatment period does not allow calculation of a definite decay rate for virus-producing cells. Our data, however, imply that the minimum half-life of infected cells may exceed 100 days.

Viral dynamics of hepatitis C early after orthotopic liver transplantation: Evidence for rapid turnover of serum virions

Viral dynamics of hepatitis C early after orthotopic liver transplantation: Evidence for rapid turnover of serum virions

The dynamics of hepatitis B virus infection.

We consider a cellular model of infection by the hepatitis B virus and describe how it may be used to account for two important features of the disease, namely (i) the wide variety of manifestations of infection and the age dependence thereof, and (ii) the typically long delay before the development of virus-induced liver cancer (primary hepatocellular carcinoma). The model is based on the assumption that the liver is comprised of both immature and mature hepatocytes, with these two subpopulations of cells responding contrastingly upon infection by the virus.

Viral dynamics in hepatitis B virus infection.

Treatment of chronic hepatitis B virus (HBV) infections with the reverse transcriptase inhibitor lamivudine leads to a rapid decline in plasma viremia and provides estimates for crucial kinetic constants of HBV replication. We find that in persistently infected patients, HBV particles are cleared from the plasma with a half-life of approximately 1.0 day, which implies a 50% daily turnover of the free virus population. Total viral release into the periphery is approximately 10(11) virus particles per day. Although we have no direct measurement of the infected cell mass, we can estimate the turnover rate of these cells in two ways: (i) by comparing the rate of viral production before and after therapy or (ii) from the decline of hepatitis B antigen during treatment. These two independent methods give equivalent results: we find a wide distribution of half-lives for virus-producing cells, ranging from 10 to 100 days in different patients, which may reflect differences in rates of lysis of infected cells by immune responses. Our analysis provides a quantitative understanding of HBV replication dynamics in vivo and has implications for the optimal timing of drug treatment and immunotherapy in chronic HBV infection. This study also represents a comparison for recent findings on the dynamics of human immunodeficiency virus (HIV) infection. The total daily production of plasma virus is, on average, higher in chronic HBV carriers than in HIV-infected patients, but the half-life of virus-producing cells is much shorter in HIV. Most strikingly, there is no indication of drug resistance in HBV-infected patients treated for up to 24 weeks.

Effect of interferon alfa on the dynamics of hepatitis C virus turnover in vivo

In about 30% to 40% of patients with chronic hepatitis C, treatment with recombinant interferon alfa (r-IFN alpha) causes a decrease of serum aminotransferases and hepatitis C virus (HCV) RNA. The antiviral mechanism of interferon alfa (IFN alpha) in vivo is unknown. From serial measurements of serum HCV-RNA concentrations following IFN alpha induced perturbation of the balance between virus production and clearance, we obtained kinetic information on the pretreatment steady-state of HCV. In patients with chronic hepatitis C responding to IFN alpha, HCV-RNA declined exponentially with a half life of approximately 2 days. Modeling of the data predicts that in patients with chronic hepatitis C responding to IFN alpha this cytokine predominantly acts as an inhibitor of de novo infection of susceptible cells. HCV is released from infected cells with a mean half life of 2.7 +/- 1.3 days, whereas the clearance rate from serum is faster (mean half life, 0.7 +/- 0.4 days). The minimum virus production and clearance per day in patients with chronic hepatitis C was calculated to be 6.7 x 1010 virions/d (range, 0.2 to 43.8 x 1010 virions/d). These values showed no correlation with the HCV genotype, aminotransferase levels, or the histological activity as assessed before the administration of r-IFN alpha. Simultaneous kinetic analysis of serum aminotransferases as surrogate markers of hepatocyte integrity revealed half lifes for the release of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) from hepatocytes of 4.7 +/- 3.8 and 3.0 +/- 3.5 days, respectively. The half life data for HCV in chronically infected patients are remarkably similar to recently published data on human immunodeficiency virus type 1 (HIV-1) suggesting that both RNA viruses replicate continuously and highly productive in vivo. The turnover rates explain the rapid generation of viral diversity and the opportunity for viral escape phenomena from the host immune surveillance. (Hepatology 1996 Feb;23(2):366-71)

Effect of interferon alfa on the dynamics of hepatitis C virus turnover in vivo

In about 30% to 40% of patients with chronic hepatitis C, treatment with recombinant interferon alfa (r-IFN alpha) causes a decrease of serum aminotransferases and hepatitis C virus (HCV) RNA. The antiviral mechanism of interferon alfa (IFN alpha) in vivo is unknown. From serial measurements of serum HCV-RNA concentrations following IFN alpha induced perturbation of the balance between virus production and clearance, we obtained kinetic information on the pretreatment steady-state of HCV. In patients with chronic hepatitis C responding to IFN alpha, HCV-RNA declined exponentially with a half life of approximately 2 days. Modeling of the data predicts that in patients with chronic hepatitis C responding to IFN alpha this cytokine predominantly acts as an inhibitor of de novo infection of susceptible cells. HCV is released from infected cells with a mean half life of 2.7 +/- 1.3 days, whereas the clearance rate from serum is faster (mean half life, 0.7 +/- 0.4 days). The minimum virus production and clearance per day in patients with chronic hepatitis C was calculated to be 6.7 x 10(10) virions/d (range, 0.2 to 43.8 x 10(10) virions/d). These values showed no correlation with the HCV genotype, aminotransferase levels, or the histological activity as assessed before the administration of r-IFN alpha. Simultaneous kinetic analysis of serum aminotransferases as surrogate markers of hepatocyte integrity revealed half lifes for the release of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) from hepatocytes of 4.7 +/- 3.8 and 3.0 +/- 3.5 days, respectively. The half life data for HCV in chronically infected patients are remarkably similar to recently published data on human immunodeficiency virus type 1 (HIV-1) suggesting that both RNA viruses replicate continuously and highly productive in vivo. The turnover rates explain the rapid generation of viral diversity and the opportunity for viral escape phenomena from the host immune surveillance.