Viral hepatitis

Analysis of the Enzymatic Activity of an NS3 Helicase Genotype 3a Variant Sequence Obtained from a Relapse Patient

The hepatitis C virus (HCV) is a species of diverse genotypes that infect over 170 million people worldwide, causing chronic inflammation, cirrhosis and hepatocellular carcinoma. HCV genotype 3a is common in Brazil, and it is associated with a relatively poor response to current direct-acting antiviral therapies. The HCV NS3 protein cleaves part of the HCV polyprotein, and cellular antiviral proteins. It is therefore the target of several HCV drugs. In addition to its protease activity, NS3 is also an RNA helicase. Previously, HCV present in a relapse patient was found to harbor a mutation known to be lethal to HCV genotype 1b. The point mutation encodes the amino acid substitution W501R in the helicase RNA binding site. To examine how the W501R substitution affects NS3 helicase activity in a genotype 3a background, wild type and W501R genotype 3a NS3 alleles were sub-cloned, expressed in E. coli, and the recombinant proteins were purified and characterized. The impact of the W501R allele on genotype 2a and 3a subgenomic replicons was also analyzed. Assays monitoring helicase-catalyzed DNA and RNA unwinding revealed that the catalytic efficiency of wild type genotype 3a NS3 helicase was more than 600 times greater than the W501R protein. Other assays revealed that the W501R protein bound DNA less than 2 times weaker than wild type, and both proteins hydrolyzed ATP at similar rates. In Huh7.5 cells, both genotype 2a and 3a subgenomic HCV replicons harboring the W501R allele showed a severe defect in replication. Since the W501R allele is carried as a minor variant, its replication would therefore need to be attributed to the trans-complementation by other wild type quasispecies.

Epidemiology and prevention of hepatitis A in travelers

BACKGROUND

Hepatitis A is the second most common vaccine-preventable travel-associated infectious disease and hepatitis A virus (HAV) is the most common cause of viral hepatitis. The incidence of infection is closely related to sanitary conditions and the level of economic development.

METHODS

We evaluated HAV incidence, infection-related risk factors, and HAV vaccination rates in international travelers through retrospective analyses using major databases, such as CENTRAL, MEDLINE, EMBASE, and the current literature describing epidemiological data for HAV infection in recent years.

RESULTS AND CONCLUSIONS

We found that the incidence of HAV infection in developed countries is very low. As international travel increases, the incidence of hepatitis A among travelers remains high and likely leads to regional outbreaks. Travelers should visit the Centers for Disease Control and Prevention website or Infectious Disease Prevention Center of their countries to learn about the incidence of infectious diseases associated with their destination before going abroad to determine if they should be vaccinated.

Hepatitis C virus core protein subverts the antiviral activities of human Kupffer cells

BACKGROUND & AIMS

Kupffer cells (KC) are important innate immune cells of the liver, functioning as scavenging sinusoidal phagocytes and transducers of pattern recognition signals, including those of toll-like receptors (TLRs). The hepatitis C virus core protein (HCVc) engages TLR2 on peripheral blood monocytes and induces production of multiple inflammatory cytokines. We examined the effects of HCVc on human primary KC functions.

METHODS

KC were isolated from living donor allografts and stimulated with HCVc and/or ligands for TLRs. KC were examined for production of cytokines, expression of programmed death-ligand 1 (PD-L1), secretion of type 1 interferons (IFNs), and expression of the apoptosis-inducing protein tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL).

RESULTS

HCVc acts as a ligand for TLR2 on human KC, inducing them to secrete interleukin (IL)-1beta, TNF-alpha, and IL-10 and up-regulate cell surface PD-L1. HCVc blocked TLR3-mediated secretion of IFN-alpha, IFN-beta, and cell surface expression of the cytotoxic molecule TRAIL. Inhibition of phosphoinositide 3 kinase with LY294002 blocked the up-regulation of PD-L1 by TLR ligands and the TLR3-specific induction of TRAIL and type 1 IFNs.

CONCLUSIONS

KC are intravascular macrophages that are continuously exposed to, and tolerant of, bacterial TLR ligands, which are delivered via the portal circulation. By mimicking a bacterial TLR2 ligand and effectively blocking the TLR3-mediated, double-stranded RNA-induced antiviral response, HCVc might appear to exploit this unique aspect of immunity in the liver.

Entry of hepatitis C virus and human immunodeficiency virus is selectively inhibited by carbohydrate-binding agents but not by polyanions

We studied the antiviral activity of carbohydrate-binding agents (CBAs), including several plant lectins and the non-peptidic small-molecular-weight antibiotic pradimicin A (PRM-A). These agents efficiently prevented hepatitis C virus (HCV) and human immunodeficiency virus type 1 (HIV-1) infection of target cells by inhibiting the viral entry. CBAs were also shown to prevent HIV and HCV capture by DC-SIGN-expressing cells. Surprisingly, infection by other enveloped viruses such as herpes simplex viruses, respiratory syncytial virus and parainfluenza-3 virus was not inhibited by these agents pointing to a high degree of specificity. Mannan reversed the antiviral activity of CBAs, confirming their association with viral envelope-associated glycans. In contrast, polyanions such as dextran sulfate-5000 and sulfated polyvinylalcohol inhibited HIV entry but were devoid of any activity against HCV infection, indicating that they act through a different mechanism. CBAs could be considered as prime drug leads for the treatment of chronic viral infections such as HCV by preventing viral entry into target cells. They may represent an attractive new option for therapy of HCV/HIV coinfections. CBAs may also have the potential to prevent HCV/HIV transmission.

Cost-effectiveness of Chronic Hepatitis C Treatment with Thymosin Alpha-1

BACKGROUND

More than one million individuals in Mexico are infected with hepatitis C virus (HCV), and 80% are at risk for developing a chronic infection that could lead to hepatic cirrhosis and other complications that impact quality of life and institutional costs. The objective of the study was to determine the most cost-effective treatment against HCV among the following: peginterferon, peginterferon plus ribavirin, peginterferon plus ribavirin plus thymosin, and no treatment.

METHODS

We carried out cost-effectiveness analysis using the institutional perspective, including a 45-year time frame and a 3% discount rate for costs and effectiveness. We employed a Bayesian-focused decision tree and a Markov model. One- and two-way sensitivity analyses were performed, as well as threshold-oriented and probabilistic analyses, and we obtained acceptability curves and net health benefits.

RESULTS

Triple therapy (peginterferon plus ribavirin plus thymosin alpha-1) was dominant with lower cost and higher utility in relationship with peginterferon + ribavirin option, peginterferon alone and no-treatment option. In triple therapy the cost per unit of success was of 1,908 [USD/quality-adjusted life years (QALY)] compared with peginterferon plus ribavirin 2,277/QALY, peginterferon alone 2,929/QALY, and no treatment 4,204/QALY. Sensitivity analyses confirmed the robustness of the base case.

CONCLUSIONS

Peginterferon plus ribavirin plus thymosin alpha-1 option was dominant (lowest cost and highest effectiveness). Using no drug was the most expensive and least effective option.