Treatment of chronic hepatitis C: a systematic review

Current status and prospect of treatments for recurrent hepatocellular carcinoma

Owing to its heterogeneous and highly aggressive nature, hepatocellular carcinoma (HCC) has a high recurrence rate, which is a non-negligible problem despite the increasing number of available treatment options. Recent clinical trials have attempted to reduce the recurrence and develop innovative treatment options for patients with recurrent HCC. In the event of liver remnant recurrence, the currently available treatment options include repeat hepatectomy, salvage liver transplantation, tumor ablation, transcatheter arterial chemoembolization, stereotactic body radiotherapy, systemic therapies, and combination therapy. In this review, we summarize the strategies to reduce the recurrence of high-risk tumors and aggressive therapies for recurrent HCC. Additionally, we discuss methods to prevent HCC recurrence and prognostic models constructed based on predictors of recurrence to develop an appropriate surveillance program.

Finding candidate drugs for hepatitis C based on chemical-chemical and chemical-protein interactions

Hepatitis C virus (HCV) is an infectious virus that can cause serious illnesses. Only a few drugs have been reported to effectively treat hepatitis C. To have greater diversity in drug choice and better treatment options, it is necessary to develop more drugs to treat the infection. However, it is time-consuming and expensive to discover candidate drugs using experimental methods, and computational methods may complement experimental approaches as a preliminary filtering process. This type of approach was proposed by using known chemical-chemical interactions to extract interactive compounds with three known drug compounds of HCV, and the probabilities of these drug compounds being able to treat hepatitis C were calculated using chemical-protein interactions between the interactive compounds and HCV target genes. Moreover, the randomization test and expectation-maximization (EM) algorithm were both employed to exclude false discoveries. Analysis of the selected compounds, including acyclovir and ganciclovir, indicated that some of these compounds had potential to treat the HCV. Hopefully, this proposed method could provide new insights into the discovery of candidate drugs for the treatment of HCV and other diseases.

Interferons and interferon regulatory factors in malaria

Malaria is one of the most serious infectious diseases in humans and responsible for approximately 500 million clinical cases and 500 thousand deaths annually. Acquired adaptive immune responses control parasite replication and infection-induced pathologies. Most infections are clinically silent which reflects on the ability of adaptive immune mechanisms to prevent the disease. However, a minority of these can become severe and life-threatening, manifesting a range of overlapping syndromes of complex origins which could be induced by uncontrolled immune responses. Major players of the innate and adaptive responses are interferons. Here, we review their roles and the signaling pathways involved in their production and protection against infection and induced immunopathologies.

Inhibitors for the hepatitis C virus RNA polymerase explored by SAR with advanced machine learning methods

Hepatitis C virus (HCV) is a global health challenge, affecting approximately 200 million people worldwide. In this study we developed SAR models with advanced machine learning classifiers Random Forest and k Nearest Neighbor Simulated Annealing for 679 small molecules with measured inhibition activity for NS5B genotype 1b. The activity was expressed as a binary value (active/inactive), where actives were considered molecules with IC50 ≤0.95 μM. We applied our SAR models to various drug-like databases and identified novel chemical scaffolds for NS5B inhibitors. Subsequent in vitro antiviral assays suggested a new activity for an existing prodrug, Candesartan cilexetil, which is currently used to treat hypertension and heart failure but has not been previously tested for anti-HCV activity. We also identified NS5B inhibitors with two novel non-nucleoside chemical motifs.

Immunotherapies in infectious diseases

The development of an infection involves interplay between the host's immune system and the virulence of the infecting microorganism. The traditional treatment of an infection involves antimicrobial chemotherapy to kill the organism. The use of immunotherapies in infections includes treatment options that modulate the immune response and can lead to control of infections. These therapies are expected to become more important therapeutic options with the increase in infections due to multidrug-resistant organisms and the increasing number of immunocompromised patients.

The importance of blood-borne viruses in elevated cancer risk among opioid-dependent people: a population-based cohort study

OBJECTIVE

To quantify cancer risk in opioid dependence and the association with infection by the oncogenic blood-borne viruses (BBVs) hepatitis C (HCV), hepatitis B (HBV) and HIV.

DESIGN

Cohort study.

SETTING

New South Wales, Australia.

PARTICIPANTS

All 45 412 adults aged 16 years or over registered for opioid substitution therapy (OST) between 1985 and 2007. Notifications of cancer, death and infection with HCV, HBV and HIV were ascertained by record linkage with registries.

MAIN OUTCOME MEASURES

The ratios of observed to expected number of cancers, standardised incidence ratios (SIRs), and the average annual per cent change (AAPC) in overall age and sex-standardised cancer incidence.

RESULTS

Overall cancer risk was modestly increased compared to the general population (SIR 1.15, 95% CI 1.07 to 1.23). Excess risk was observed for 11 cancers, particularly lung (4.02, 95% CI 3.32 to 4.82), non-Hodgkin's lymphoma (1.51, 95% CI 1.20 to 1.88) and liver (8.04, 95% CI 6.18 to 10.3). Reduced risk was observed for six cancers, including prostate (0.16, 95% CI 0.06 to 0.32) and breast (0.48, 95% CI 0.35 to 0.62). Individuals notified with HCV or HBV had a markedly increased risk of liver cancer; lung cancer risk was also increased in those with HCV. HIV was associated with an elevated risk of liver, anus and kidney cancer, non-Hodgkin lymphoma and Kaposi sarcoma. Cancer risk was not increased in individuals without a BBV notification, apart from pancreatic cancer (3.92, 95% CI 1.07 to 10.0). Cancer incidence increased significantly over time (AAPC 9.4%, 4.2% to 15%, p=0.001).

CONCLUSIONS

BBVs play a major role in the cancer risk profile of opioid-dependent individuals registered for OST. To address the dramatic increasing trend in cancer incidence, the OST setting could be utilised for cancer prevention strategies.

Modulation of CD4⁺ T cell responses following splenectomy in hepatitis C virus-related liver cirrhosis

Dysfunction of T cells is a common feature in chronic persistent viral infections, including hepatitis C virus (HCV), and although hepatic and peripheral T cells have been studied extensively in chronic HCV hepatitis, the role of splenic T cell responses in such patients is poorly defined. This is an important issue, as thrombocytopenia is a complication of HCV-related liver cirrhosis (LC), due to splenic platelet sequestration and bone marrow suppression; splenectomy has been proposed to treat such patients. Herein, we studied peripheral blood mononuclear cells (PBMC) and splenic lymphoid subpopulations from a total of 22 patients, including 15 with HCV-related LC with marked thrombocytopenia treated with splenectomy, and seven controls. CD4(+) T cells from peripheral blood and spleen were isolated and phenotype and function evaluated. Splenic CD4(+) T cells in patients with LC expressed molecules associated with inhibitory signalling, including increased frequency of negative markers such as cytotoxic T lymphocyte associated antigen-4 (CTLA-4) and programmed death 1 (PD-1) and decreased production of cytokines. Patients with LC manifest higher levels of splenic CD4(+) regulatory T cells and PD-L1- and PD-L2-expressing cells than controls. Blocking of PD-1/PD-1 ligand interaction reconstituted proliferative and cytokine responses of splenic mononuclear cells (SMC) from patients with LC. Splenectomy was followed by an increase in the ratio of interferon (IFN)-γ to interleukin (IL)-10 and a reduction of PD-1-expressing CD4(+) T cells in peripheral blood. Our data suggest that peripheral tolerance is promoted by the spleen in LC via the up-regulated expression of PD-1 ligands.

Excellent superiority and specificity of COBAS TaqMan HCV assay in an early viral kinetic change during pegylated interferon alpha-2b plus ribavirin treatment

BACKGROUND

An early virological response (EVR) after the start of interferon (IFN) treatment for chronic hepatitis C leads to a successful virological outcome. To analyze an association between sustained virological response (SVR) and EVR by comparing TaqMan with Amplicor assays in HCV genotype 1-infected patients treated with pegylated (PEG)-IFN alpha-2b plus ribavirin (RBV).

METHODS

We retrospectively analyzed a total of 80 HCV genotype 1 patients (39 SVR and 41 non-SVR patients), who received an enough dosage and a complete 48-week treatment of PEG-IFN alpha-2b plus RBV. Serum HCV RNA levels were measured by both TaqMan and Amplicor assays for each patients at Weeks 2, 4, 8 and 12 after the start of the antiviral treatment.

RESULTS

Of the 80 patients with undetectable HCV RNA by Amplicor, 17 (21.3%) patients were positive for HCV RNA by TaqMan at Weeks 12. The quantification results showed that no significant difference in the decline of HCV RNA level between TaqMan and Amplicor 10-fold method assays within the initial 12 weeks of the treatment was found. However, the qualitative analysis showed significant differences of the positive predictive rates for SVR were found between TaqMan (100% at weeks 4 and 100% at weeks 8) and Amplicor (80.0% and 69.6%, respectively).

CONCLUSIONS

The COBAS TaqMan HCV assay is very useful for monitoring HCV viremia during antiviral treatment to predict a SVR in HCV genotype 1 patients.

Cell-Penetrating Peptides for Antiviral Drug Development

Viral diseases affect hundreds of millions of people worldwide, and the few available drugs to treat these diseases often come with limitations. The key obstacle to the development of new antiviral agents is their delivery into infected cells in vivo. Cell-penetrating peptides (CPPs) are short peptides that can cross the cellular lipid bilayer with the remarkable capability to shuttle conjugated cargoes into cells. CPPs have been successfully utilized to enhance the cellular uptake and intracellular trafficking of antiviral molecules, and thereby increase the inhibitory activity of potential antiviral proteins and oligonucleotide analogues, both in cultured cells and in animal models. This review will address the notable findings of these studies, highlighting some promising results and discussing the challenges CPP technology has to overcome for further clinical applications.

Molecular and contextual markers of hepatitis C virus and drug abuse

The spread of hepatitis C virus (HCV) infection involves a complex interplay of social risks, and molecular factors of both virus and host. Injection drug abuse is the most powerful risk factor for HCV infection, followed by sexual transmission and additional non-injection drug abuse factors such as co-infection with other viruses and barriers to treatment. It is clearly important to understand the wider context in which the factors related to HCV infection occur. This understanding is required for a comprehensive approach leading to the successful prevention, diagnosis, and treatment of HCV. An additional consideration is that current treatments and advanced molecular methods are generally unavailable to socially disadvantaged patients. Thus, the recognition of behavioral/social, viral, and host factors as components of an integrated approach to HCV is important to help this vulnerable group. Equally important, this approach is key to the development of personalized patient treatment - a significant goal in global healthcare. In this review, we discuss recent findings concerning the impact of drug abuse, epidemiology, social behavior, virology, immunopathology, and genetics on HCV infection and the course of disease.

Determinants of antiviral treatment initiation in a hepatitis C-infected population benefiting from universal health care coverage

BACKGROUND AND AIMS

In view of increasing therapeutic efficacy, the delivery of hepatitis C virus (HCV) antiviral treatment is expected to increase. Yet practical experience reveals a low rate of treatment, particularly among intravenous drug users. The aim of the present study was to examine the prevalence of HCV treatment and identify factors associated with HCV treatment in a population of patients evaluated in an academic hepatology outpatient clinic between 2001 and 2002.

PATIENTS AND METHODS

The charts of HCV-infected patients who attended the outpatient clinic of the liver division between January 2001 and December 2002 were retrospectively reviewed. Regression analyses were conducted to compare patients according to HCV treatment initiation.

RESULTS

Of 378 eligible patients (past intravenous drug users 61%), 143 (38%) initiated antiviral treatment. Enrolment in a methadone maintenance program and a strong willingness to get treatment were independently associated with treatment initiation, while current intravenous drug use, alcoholic liver damage on biopsy, precarious housing arrangements and personality disorders were negatively associated with treatment initiation. Among patients who were offered treatment, 40% refused (they did not differ from the treated group for past or current substance abuse).

CONCLUSIONS

Only 38% of eligible patients initiated treatment; treatment refusal was very common. The results of the present study showed that a significant barrier to therapy involved patient perceptions.

Phenotypic characterization of resistant Val36 variants of hepatitis C virus NS3-4A serine protease

In patients chronically infected with hepatitis C virus (HCV) strains of genotype 1, rapid and dramatic antiviral activity has been observed with telaprevir (VX-950), a highly selective and potent inhibitor of the HCV NS3-4A serine protease. HCV variants with substitutions in the NS3 protease domain were observed in some patients during telaprevir dosing. In this study, purified protease domain proteins and reconstituted HCV subgenomic replicons were used for phenotypic characterization of many of these substitutions. V36A/M or T54A substitutions conferred less than eightfold resistance to telaprevir. Variants with double substitutions at Val36 plus Thr54 had approximately 20-fold resistance to telaprevir, and variants with double substitutions at Val36 plus Arg155 or Ala156 had >40-fold resistance to telaprevir. An X-ray structure of the HCV strain H protease domain containing the V36M substitution in a cocomplex with an NS4A cofactor peptide was solved at a 2.4-A resolution. Except for the side chain of Met36, the V36M variant structure is identical to that of the wild-type apoenzyme. The in vitro replication capacity of most variants was significantly lower than that of the wild-type replicon in cells, which is consistent with the impaired in vivo fitness estimated from telaprevir-dosed patients. Finally, the sensitivity of these replicon variants to alpha interferon or ribavirin remained unchanged compared to that of the wild-type.

Serum levels of IgG to the peptide of HCV1b core at positions 35-44 correlated with persistent infection, while levels of IgG to the peptide of NS5A at positions 2132-2140 correlated with better prognosis in HCV-infected patients

We previously reported that two IgG Abs to the hepatitis C virus (HCV), anti-core 35-44 (C35) and anti-NS5A 2132-2140 (NS5A2132), existed in the sera of the majority of patients with HCV infection. This study investigated if measuring the two Abs would facilitate the prediction of a patient's prognosis. The serum levels of anti-C35 were found to correlate with persistent infection, while those of anti-NS5A2132 correlated with a better prognosis in HCV-infected patients. These results suggest that sequential measurement of the two Abs together may provide new information for the prediction of prognosis.

Screening in liver disease

A disease is suitable for screening if it is common, if the target population can be identified and reached and if both a good screening test and an effective therapy are available. Of the most common liver diseases only viral hepatitis and genetic hemochromatosis partially satisfy these conditions. Hepatitis C is common, the screening test is good and the therapy eliminates the virus in half of the cases, but problems arise in the definition of the target population. In fact generalized population screening is not endorsed by international guidelines, although some recommend screening immigrants from high prevalence countries. Opportunistic screening (case finding) of individuals with classic risk factors, such as transfusion before 1992 and drug addiction, is the most frequently used strategy, but there is disagreement whether prison inmates, individuals with a history of promiscuous or traumatic sex and health care workers should be screened. In a real practice setting the performance of opportunistic screening by general practitioners is low but can be ameliorated by training programs. Screening targeted to segments of the population or mass campaigns are expensive and therefore interventions should be aimed to improve opportunistic screening and the detection skills of general practitioners. Regarding genetic hemochromatosis there is insufficient evidence for population screening, but individual physicians can decide to screen racial groups with a high prevalence of the disease, such as people in early middle age and of northern European origin. In the other cases opportunistic screening of high risk individuals should be performed, with a high level of suspicion in case of unexplained liver disease, diabetes, juvenile artropathy, sexual dysfunction and skin pigmentation.

Modulation of the anti-inflammatory interleukin 10 and of proapoptotic IL-18 in patients with chronic hepatitis C treated with interferon alpha and ribavirin

The aim of this work was to analyse apoptosis rate, measured by the serum levels of proapoptotic interleukin (IL)-18 and of soluble Fas (sFas), as well as of anti-inflammatory IL-10, in patients with chronic hepatitis C, at baseline and after treatment with interferon alpha and ribavirin. Twenty-seven patients with biopsy-proven chronic hepatitis C were studied, at baseline and after treatment with interferon alpha (21 cases) or pegylated interferon (6 cases) plus ribavirin. A group of 15 healthy sex- and age-matched individuals was selected as control. Serum concentrations of sFas, IL-10 and IL-18 were determined by ELISA in sandwich. The relationship of these molecules to necro-inflammatory and fibrotic activity was evaluated. Evolution of the serum concentrations of these molecules was analysed after treatment. Significantly increased serum concentrations of sFas were detected in patients with chronic hepatitis, compared with controls. Levels of this molecule were significantly correlated with necroinflammatory activity. Likewise, concentrations of IL-10 were significantly increased in the group of patients, compared with controls. Treatment with interferon and ribavirin induced a significant decrease of IL-18 concentration independently of the viral response. In contrast, levels of sFas decreased only in those patients with sustained response to therapy. Finally, baseline levels of IL-10 were significantly increased in patients without response to treatment, compared with those with sustained response, but the concentration did not change with the treatment. Increased serum levels of IL-10 are a negative prognostic marker of response to hepatitis C treatment. A significant decrease of apoptotic rate, as determined by sFas, can be expected in patients with a response to therapy.

Hepatitis C virus free-virion and immune-complex dynamics during interferon therapy with and without ribavirin in genotype-1b chronic hepatitis C patients

The Synergistic effect of interferon (IFN) and ribavirin for patients with chronic hepatitis C has been demonstrated, but ribavirin has no apparent direct antiviral effect against hepatitis C virus (HCV) when used as monotherapy. To elucidate the mechanism of ribavirin on enhanced HCV eradication when used in combination therapy, we investigated the serum HCV dynamics of free-virions (FV) and immune-complexes (IC) in genotype-1b infected patients treated with IFN-alpha2b alone (n = 11) or in combination with ribavirin (n = 15). Serum FV- and IC-HCV RNA were separated by immunoprecipitation using anti-human immunoglobulin and quantified serially using real-time detection polymerase chain reaction. At the first phase (day 0-2), the decline of FV- and IC-HCV RNA was similar between the two treatment groups. At the second phase (day 2-28), the decline of IC was significantly faster in patients treated with IFN plus ribavirin compared with IFN alone [exponential decay slope = 0.079 +/- 0.036 vs 0.048 +/- 0.027 log10/day, P = 0.0248; half-life = 81.1 +/- 21.4 vs 135.1 +/- 61.4 h, P = 0.0053], although the second phase FV-decline was not significantly different between the two treatment groups. The fast second phase decline of IC was associated with sustained virological response to therapy. These results suggest that ribavirin may modulate the humoral immune response against HCV and trigger a favourable response to IFN. In conclusion, analysis of early IC-HCV dynamics is useful for predicting the response to therapy and for understanding the mechanism of action of antiviral drugs in chronic hepatitis C patients.

Hepatitis C: a review for primary care physicians

Primary care physicians see many of the estimated 250 000 Canadians chronically infected with the hepatitis C virus (HCV). Of this number, about one-third are unaware they are infected, which constitutes a large hidden epidemic. They continue to spread HCV unknowingly and cannot benefit from advances in antiviral therapy that may clear them of the virus. Many HCV-infected people remain asymptomatic, which means it is important to assess for risk factors and test patients accordingly. The third-generation enzyme immunoassay for HCV antibodies is a sensitive and specific test, although the presence of the virus can be confirmed by polymerase chain reaction testing for HCV RNA in some circumstances. Pegylated interferon-alpha and ribavirin combination therapy clears the virus in about 45%-80% of patients, depending on viral genotype. Preventive strategies and counselling recommendations are also reviewed.

Residential substance user treatment programs as venues for HCV pharmacological treatment: client and staff perspectives

Hepatitis C virus (HCV) infection is highly prevalent among drug users. While there are antiviral medications available to combat the virus, the medication regimen is quite arduous, presenting special issues for drug users. We examined the challenges and benefits of using residential substance user treatment programs as venues for clients to undergo HCV medication regimens. Analyses of qualitative data collected from clients and staff in 2003 at four residential substance user treatment programs in the U.S. indicate that challenges primarily include issues involving the medications' side effects, and both financial and communication concerns. Benefits especially involve clients' feelings that they are being proactive in addressing health issues in an environment that provides much-needed support. Findings illuminate the complex issues involved for both clients and the programs, and some steps that programs can take to better support HCV-infected clients regarding HCV medication concerns.

Injection drug use and the hepatitis C virus: considerations for a targeted treatment approach--the case study of Canada

Infection with the hepatitis C virus (HCV) is a major public health burden in Canada and globally. The literature shows that injection drug use is currently the primary transmission route for HCV, and that a majority of injection drug users (IDUs) are currently infected with HCV in Canada. This article first reviews the burden of HCV within IDU populations and the transmission risks and the treatment implications specific to IDUs. Traditionally, IDUs have been excluded from HCV treatment unless abstaining from illicit drug use. However, recent research suggests that categorical exclusion is not medically necessary. A series of key questions about the feasibility of offering HCV treatment to IDUs in the specific Canadian context are considered, including concerns related to the motivation of treatment for IDUs, treatment delivery, treatment side effects, HCV reinfection, and the social environment. The article concludes that treatment of HCV-infected illicit drug users is both feasible and may be necessary to reduce transmission and adverse outcomes in this high-risk population.

Immune-based novel therapies for chronic hepatitis C virus infection

Hepatitis C virus (HCV) infection is a great public health problem, with an estimated 200 million chronically infected patients worldwide. No vaccines are currently available for HCV, and only a subset of HCV patients responds to interferon-alpha (IFN-alpha) and Ribavirin treatment. Substantial evidence has emerged recently to support the role of the host immune response in the outcome and pathogenesis of HCV infection. Our aims of this article are to present the immune-based novel therapeutic options for HCV infection and the evidence supporting their use in patients with chronic hepatitis C. There is a growing consensus that acute control of HCV infection is associated with a vigorous intrahepatic antiviral CD4+ and CD8+ T cell response. IFN-gamma was detectable in the livers of the chimpanzees that cleared or controlled the virus, raising the possibility that IFN-gamma might perform antiviral effector functions during HCV infection. Based on these observations, therapeutic induction of intrahepatic IFN-gamma by adoptive immunotherapy might be able to control chronic HCV infection. Immune-based novel therapies appear to hold great promise in treating chronic HCV infection.

Providing treatment for hepatitis C in an Australian district centre

Hepatitis C virus (HCV) poses a major public health problem world wide. The introduction of combined therapy (interferon and ribavirin) and the recent development of pegylated interferon have offered the opportunity to alter the natural history of HCV, potentially reducing morbidity and mortality. Until recently, treatment has been confined to larger Australian cities. This paper describes the establishment of a clinic for the treatment of HCV in a regional Australian city. The facilities of the sexual health clinic were utilised. Factors contributing to the success of the clinic include the specialist nurse, a multidisciplinary approach, and the service model of shared care with general practitioners. The patient population and the outcomes of managing HCV in a regional centre are described. The sustained viral response rate is comparable to the published data from specialist centres.

Autocrine/paracrine IL-15 that is required for type I IFN-mediated dendritic cell expression of MHC class I-related chain A and B is impaired in hepatitis C virus infection

We previously reported that monocyte-derived dendritic cells activate resting NK cells by expressing MHC class I-related chain A and B (MICA/B), ligands for NKG2D, in response to IFN-alpha, but the MICA/B expression was severely impaired in patients with chronic hepatitis C virus (HCV) infection. In the present study, we examined induction of MICA/B on DCs by various innate cytokines and found that DCs from either healthy donors or HCV-infected individuals, upon IL-15 stimulation, express MICA/B and can activate NK cells, which is solely dependent on MICA/B-NKG2D interaction. Of interest is the finding that IL-15- and type I IFN-mediated induction of MICA/B in healthy donors is completely inhibited when DCs are incubated in the presence of anti-IFN-alpha/betaR or anti-IL-15Ralpha, respectively, suggesting interdependent roles of these cytokines in MICA/B expression. Indeed, DCs produced IL-15 in response to type I IFN, whereas they directly produced IFN-beta, in response to IL-15, which was followed by the production of IFN-alpha. In HCV-infected individuals, type I IFN-mediated production of IL-15 was virtually absent, but IL-15-mediated production of type I IFN was not compromised, which is consistent with the distinct ability of these cytokines to induce MICA/B in these patients. The present study demonstrates that IL-15 and type I IFN lead to DC expression of MICA/B and subsequent DC activation of NK cells, which is critically dependent on each other's autocrine/paracrine effect, and suggests that impaired IL-15 production is one of the mechanisms of the aberrant response of DC to type I IFN in HCV-infected patients.

Development of recombinant vesicular stomatitis viruses that exploit defects in host defense to augment specific oncolytic activity

Vesicular stomatitis virus (VSV) is a negative-stranded RNA virus normally sensitive to the antiviral actions of alpha/beta interferon (IFN-alpha/beta). Recently, we reported that VSV replicates to high levels in many transformed cells due, in part, to susceptible cells harboring defects in the IFN system. These observations were exploited to demonstrate that VSV can be used as a viral oncolytic agent to eradicate malignant cells in vivo while leaving normal tissue relatively unaffected. To attempt to improve the specificity and efficacy of this system as a potential tool in gene therapy and against malignant disease, we have genetically engineered VSV that expresses the murine IFN-beta gene. The resultant virus (VSV-IFNbeta) was successfully propagated in cells not receptive to murine IFN-alpha/beta and expressed high levels of functional heterologous IFN-beta. In normal murine embryonic fibroblasts (MEFs), the growth of VSV-IFNbeta was greatly reduced and diminished cytopathic effect was observed due to the production of recombinant IFN-beta, which by functioning in a manner involving autocrine and paracrine mechanisms induced an antiviral effect, preventing virus growth. However, VSV-IFNbeta grew to high levels and induced the rapid apoptosis of transformed cells due to defective IFN pathways being prevalent and thus unable to initiate proficient IFN-mediated host defense. Importantly, VSV expressing the human IFN-beta gene (VSV-hIFNbeta) behaved comparably and, while nonlytic to normal human cells, readily killed their malignant counterparts. Similar to our in vitro observations, following intravenous and intranasal inoculation in mice, recombinant VSV (rVSV)-IFNbeta was also significantly attenuated compared to wild-type VSV or rVSV expressing green fluorescent protein. However, VSV-IFNbeta retained propitious oncolytic activity against metastatic lung disease in immunocompetent animals and was able to generate robust antitumor T-cell responses. Our data indicate that rVSV designed to exploit defects in mechanisms of host defense can provide the basis for new generations of effective, specific, and safer viral vectors for the treatment of malignant and other disease.

Managing occupational risks for hepatitis C transmission in the health care setting

Hepatitis C virus (HCV) infection is a significant contemporary health problem in the United States and elsewhere. Because it is primarily transmitted via blood, hepatitis C infection presents risks for both nosocomial transmission to patients and occupational spread to health care workers. Recent insights into the pathogenesis, immunopathogenesis, natural history, and treatment of infection caused by this unique flavivirus provide a rationale for the use of new strategies for managing occupational hepatitis C infections when they occur. This article reviews this developing information. Recently published data demonstrate success rates in the treatment of "acute hepatitis C syndrome" that approach 100\%, and although these studies are not directly applicable to all occupational infections, they may provide important clues to optimal management strategies. In addition, the article delineates approaches to the prevention of occupational exposures and also addresses the difficult issue of managing HCV-infected health care providers. The article summarizes currently available data about the nosocomial epidemiology of HCV infection and the magnitude of risk and discusses several alternatives for managing exposure and infection. No evidence supports the use of immediate postexposure prophylaxis with immunoglobulin, immunomodulators, or antiviral agents. Based on the very limited data available, the watchful waiting and preemptive therapy strategies described in detail in this article represent reasonable interim approaches to the complex problem of managing occupational HCV infections, at least until more definitive data are obtained.