The biology and pathogenesis of hepatitis viruses

Viral hepatitis is caused mainly by infection with one of the five hepatitis viruses, which use the liver as their primary site of replication. Each of these, known as hepatitis A through E viruses (HAV to HEV), belong to different virus families, have unique morphology, genomic organization and replication strategy. These viruses cause similar clinical manifestations during the acute phase of infection but vary in their ability to cause chronic infection. While HAV and HEV cause only acute disease with no chronic sequelae, HBV, HCV and HDV cause varying degrees of chronicity and liver injury, which can progress to cirrhosis and liver cancers. Though specific serological tests are available for the known hepatitis viruses, nearly 20% of all hepatitis cases show no markers. Antiviral therapy is also recommended for some hepatitis viruses and a preventive vaccine is available only for hepatitis B. More research and public awareness programmes are needed to control the disease. This review will provide an overview of the hepatitis viruses and the disease they cause.

Microglia play a major role in direct viral-induced demyelination

Microglia are the resident macrophage-like populations in the central nervous system (CNS). Microglia remain quiescent, unable to perform effector and antigen presentation (APC) functions until activated by injury or infection, and have been suggested to represent the first line of defence for the CNS. Previous studies demonstrated that microglia can be persistently infected by neurotropic mouse hepatitis virus (MHV) which causes meningoencephalitis, myelitis with subsequent axonal loss, and demyelination and serve as a virus-induced model of human neurological disease multiple sclerosis (MS). Current studies revealed that MHV infection is associated with the pronounced activation of microglia during acute inflammation, as evidenced by characteristic changes in cellular morphology and increased expression of microglia-specific proteins, Iba1 (ionized calcium-binding adaptor molecule 1), which is a macrophage/microglia-specific novel calcium-binding protein and involved in membrane ruffling and phagocytosis. During chronic inflammation (day 30 postinfection), microglia were still present within areas of demyelination. Experiments performed in ex vivo spinal cord slice culture and in vitro neonatal microglial culture confirmed direct microglial infection. Our results suggest that MHV can directly infect and activate microglia during acute inflammation, which in turn during chronic inflammation stage causes phagocytosis of myelin sheath leading to chronic inflammatory demyelination.

Sero-Prevalence of Rodent Pathogens in India

Health monitoring is an integral part of laboratory animal quality standards. However, current or past prevalence data as well as regulatory requirements dictate the frequency, type and the expanse of health monitoring. In an effort to understand the prevalence of rodent pathogens in India, a preliminary study was carried out by sero-epidemiology. Sera samples obtained from 26 public and private animal facilities were analyzed for the presence of antibodies against minute virus of mice (MVM), ectromelia virus (ECTV), lymphocytic choriomeningitis virus (LCMV), mouse hepatitis virus (MHV), Sendai virus (SeV), and Mycoplasma pulmonis in mice, and SeV, rat parvo virus (RPV), Kilham's rat virus (KRV) and sialodacryoadenitis virus (SDAV) in rats, by sandwich ELISA. It was observed that MHV was the most prevalent agent followed by Mycoplasma pulmonis and MVM in mice, and SDAV followed by RPV were prevalent in rats. On the other hand, none of the samples were positive for ECTV in mice, or SeV or KRV in rats. Multiple infections were common in both mice and rats. The incidence of MHV and Mycoplasma pulmonis was higher in facilities maintained by public organizations than in vivaria of private organizations, although the difference was not statistically different. On the other hand the prevalence of rodent pathogens was significantly higher in the northern part of India than in the South. These studies form the groundwork for detailed sero-prevalence studies which should further lay the foundations for country-specific guidelines for health monitoring of laboratory animals.

Targeted delivery of hepatitis C virus-specific short hairpin RNA in mouse liver using Sendai virosomes

Internal ribosome entry site (IRES)-mediated translation of input viral RNA is the initial required step for the replication of the positive-stranded genome of hepatitis C virus (HCV). We have shown previously the importance of the GCAC sequence near the initiator AUG within the stem and loop IV (SLIV) region in mediating ribosome assembly on HCV RNA. Here, we demonstrate selective inhibition of HCV-IRES-mediated translation using short hairpin (sh)RNA targeting the same site within the HCV IRES. sh-SLIV showed significant inhibition of viral RNA replication in a human hepatocellular carcinoma (Huh7) cell line harbouring a HCV monocistronic replicon. More importantly, co-transfection of infectious HCV-H77s RNA and sh-SLIV in Huh7.5 cells successfully demonstrated a significant decrease in viral RNA in HCV cell culture. Additionally, we report, for the first time, the targeted delivery of sh-SLIV RNA into mice liver using Sendai virosomes and demonstrate selective inhibition of HCV-IRES-mediated translation. Results provide the proof of concept that Sendai virosomes could be used for the efficient delivery of shRNAs into liver tissue to block HCV replication.

Monoclonal Antibodies against Hepatitis C Genotype 3a Virus Like Particle Inhibit Virus Entry in Cell Culture System

The envelope protein (E1-E2) of Hepatitis C virus (HCV) is a major component of the viral structure. The glycosylated envelope protein is considered to be important for initiation of infection by binding to cellular receptor(s) and also known as one of the major antigenic targets to host immune response. The present study was aimed at identifying mouse monoclonal antibodies which inhibit binding of virus like particles of HCV to target cells. The first step in this direction was to generate recombinant HCV-like particles (HCV-LPs) specific for genotypes 3a of HCV (prevalent in India) using the genes encoding core, E1 and E2 envelop proteins in a baculovirus expression system. The purified HCV-LPs were characterized by ELISA and electron microscopy and were used to generate monoclonal antibodies (mAbs) in mice. Two monoclonal antibodies (E8G9 and H1H10) specific for the E2 region of envelope protein of HCV genotype 3a, were found to reduce the virus binding to Huh7 cells. However, the mAbs generated against HCV genotype 1b (D2H3, G2C7, E1B11) were not so effective. More importantly, mAb E8G9 showed significant inhibition of the virus entry in HCV JFH1 cell culture system. Finally, the epitopic regions on E2 protein which bind to the mAbs have also been identified. Results suggest a new therapeutic strategy and provide the proof of concept that mAb against HCV-LP could be effective in preventing virus entry into liver cells to block HCV replication.

Specific Sequence of a Beta Turn in Human La Protein May Contribute to Species Specificity of Hepatitis C Virus

Human La protein is known to be an essential host factor for translation and replication of hepatitis C virus (HCV) RNA. Previously, we have demonstrated that residues responsible for interaction of human La protein with the HCV internal ribosomal entry site (IRES) around the initiator AUG within stem-loop IV form a beta-turn in the RNA recognition motif (RRM) structure. In this study, sequence alignment and mutagenesis suggest that the HCV RNA-interacting beta-turn is conserved only in humans and chimpanzees, the species primarily known to be infected by HCV. A 7-mer peptide corresponding to the HCV RNA-interacting region of human La inhibits HCV translation, whereas another peptide corresponding to the mouse La sequence was unable to do so. Furthermore, IRES-mediated translation was found to be significantly high in the presence of recombinant human La protein in vitro in rabbit reticulocyte lysate. We observed enhanced replication with HCV subgenomic and full-length replicons upon overexpression of either human La protein or a chimeric mouse La protein harboring a human La beta-turn sequence in mouse cells. Taken together, our results raise the possibility of creating an immunocompetent HCV mouse model using human-specific cell entry factors and a humanized form of La protein.

Protection of rabbits against lapinized rinderpest virus with purified envelope glycoproteins of peste-des-petits-ruminants and rinderpest viruses

Haemagglutinin (HA) and fusion (F) proteins of peste-des-petits-ruminants virus (PPRV) and rinderpest virus (RPV) were purified by immunoaffinity chromatography. The purified proteins were characterized by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS-PAGE). Rabbit hyperimmune sera were raised against the purified HA and F proteins and assayed by enzyme-linked immunosorbent assay (ELISA), haemagglutination-inhibition (HAI) and virus neutralization (VN) tests. The immunized animals were challenged with a virulent lapinized (rabbit-adapted) strain of RPV: Both HA and F proteins of PPRV protected rabbits against a lethal challenge with lapinized RPV. As expected, RPV HA and F proteins also conferred a similar protection against the homologous challenge. The postchallenge antibody responses were of a true anamnestic type.

Similarities in the Genomic Sequence and Coat Protein-Structure of Plant Viruses

The genomic sequences of several RNA plant viruses including cucumber mosaic virus, brome mosaic virus, alfalfa mosaic virus and tobacco mosaic virus have become available recently. The former two viruses are icosahedral while the latter two are bullet and rod shaped, respectively in particle morphology. The non-structural 3a proteins of cucumber mosaic virus and brome mosaic virus have an amino acid sequence homology of 35% and hence are evolutionarily related. In contrast, the coat proteins exhibit little homology, although the circular dichroism spectrum of these viruses are similar. The non-coding regions of the genome also exhibit variable but extensive homology. Comparison of the brome mosaic virus and alfalfa mosaic virus sequences reveals that they are probably related although with a much larger evolutionary distance. The polypeptide folds of the coat protein of three biologically distinct isometric plant viruses, tomato bushy stunt virus, southern bean mosaic virus and satellite tobacco necrosis virus have been shown to display a striking resemblance. All of them consist of a topologically similar 8-standard β-barrel. The implications of these studies to the understanding of the evolution of plant viruses will be discussed.

Biochemical effects of 3,5-diethoxycarbonyl-1, 4-dihydrocollidine in mouse liver

3,5-Diethoxycarbonyl-1,4-dihydrocollidine (DDC) is a porphyrinogenic agent and is a powerful inducer of δ-aminolaevulinate synthetase, the first and rate-limiting enzyme of the haem-biosynthetic pathway, in mouse liver. However, DDC strikingly inhibits mitochondrial as well as microsomal haem synthesis by depressing the activity of ferrochelatase in vivo. The drug on repeated administration to female mice has been found to elicit hypertrophic effects in the liver microsomes initially, but the effects observed at later stages denote either hyperplasia or increase in polyploidal cells. The microsomal protein concentration shows a striking decrease with repeated doses of the drug. The rate of microsomal protein synthesis in vivo as well as in vitro shows an increase with two injections of DDC but decreases considerably with repeated administration of the drug. The activities of NADPH-cytochrome creductase and ribonuclease are not affected in the liver microsomes of drug-treated animals when expressed per mg of microsomal protein. DDC has also been found to cause degradation of microsomal haem, which is primarily responsible for the decrease in cytochrome P-450 content. The drug also leads to a decrease in mitochondrial cytochrome c levels due to inhibition of haem synthesis and also due to degradation of mitochondrial haem at later stages. The biochemical effects of the drug are compared and discussed with those reported for allylisopropylacetamide and phenobarbital.

Thymidine inhibits the incorporation of 5-fluoro-2'-deoxyuridine to DNA of mouse mammary tumour

5-Fluoro-2'-deoxyuricine is incorporated into DNA of mouse breast tumour Image . The incorporation is inhibited by thymidine. Part of the fluorodeoxyuridine is cleaved to fluorouracil and is incorporated into RNA. This incorporation is enhanced by thymidine. The result suggests that the major mechanism of action of the fluorouracil is due to its incorporation into RNA. FUra, 5-Fluorouracil; FdUR, 5-Fluoro-2'-deoxyuridine; FdUMP, 5-Fluoro-2'-deoxyuridine-5'-monophosphate.

Toward the Discovery of Vaccine Adjuvants: Coupling In Silico Screening and In Vitro Analysis of Antagonist Binding to Human and Mouse CCR4 Receptors

Background: Adjuvants enhance or modify an immune response that is made to an antigen. An antagonist of the chemokine CCR4 receptor can display adjuvant-like properties by diminishing the ability of CD4+CD25+ regulatory T cells (Tregs) to down-regulate immune responses. Methodology: Here, we have used protein modelling to create a plausible chemokine receptor model with the aim of using virtual screening to identify potential small molecule chemokine antagonists. A combination of homology modelling and molecular docking was used to create a model of the CCR4 receptor in order to investigate potential lead compounds that display antagonistic properties. Three-dimensional structure-based virtual screening of the CCR4 receptor identified 116 small molecules that were calculated to have a high affinity for the receptor; these were tested experimentally for CCR4 antagonism. Fifteen of these small molecules were shown to inhibit specifically CCR4-mediated cellmigration, including that of CCR4(+) Tregs. Significance: Our CCR4 antagonists act as adjuvants augmenting human T cell proliferation in an in vitro immune response model and compound SP50 increases T cell and antibody responses in vivo when combined with vaccine antigens of Mycobacterium tuberculosis and Plasmodium yoelii in mice.

HDAC inhibitor valproic acid enhances tumor cell kill in adenovirus-HSVtk mediated suicide gene therapy in HNSCC xenograft mouse model

Safety, efficacy and enhanced transgene expression are the primary concerns while using any vector for gene therapy. One of the widely used vectors in clinical. trials is adenovirus which provides a safe way to deliver the therapeutic gene. However, adenovirus has poor transduction efficiency in vivo since most tumor cells express low coxsackie and adenovirus receptors. Similarly transgene expression remains low, possibly because of the chromatization of adenoviral genome upon infection in eukaryotic cells, an effect mediated by histone deacetylases (HDACs). Using a recombinant adenovirus (Ad-HSVtk) carrying the herpes simplex thymidine kinase (HSVtk) and GFP genes we demonstrate that HDAC inhibitor valproic acid can bring about an increase in CAR expression on host cells and thereby enhanced Ad-HSVtk infectivity. It also resulted in an increase in transgene (HSVtk and GFP) expression. This, in turn, resulted in increased cell kill of HNSCC cells, following ganciclovir treatment in vitro as well as in vivo in a xenograft nude mouse model.

Characterization of mouse neuronal Ca2+/calmodulin kinase II inhibitor alpha

We have overexpressed an 8.5-kDa mouse Ca2+/calmodulin kinase II inhibitor a protein (mCaMKIIN alpha) in Escherichia coli and demonstrate that the recombinant protein is a potent inhibitor of Ca2+/calmodulin kinase 11 (CaMKII) in vitro. However, antibodies raised against recombinant mCaMKIIN alpha. react with an similar to 37-kDa protein present in mouse brain. The pattern of expression of the similar to 37-kDa protein is similar to that of mCaMKIIN alpha mRNA as both are expressed in normal but not Japanese encephalitis virus (JEV)-infected mouse brain. Subcellular localization studies indicate that the similar to 37-kDa protein is present in the post-synaptic density (PSD) where mCaMKII alpha is known to perform key regulatory functions. We conclude that the similar to 37-kDa protein identified in this study is mCaMKIIN alpha. and its localization in the PSD indicates a novel role for this protein in the regulation of neuronal CaMKII alpha. (c) 2007 Elsevier B.V. All rights reserved.

Non-segmented negative sense RNA viruses as vectors for vaccine development

This article intends to cover two aspects of non-segmented negative sense RNA viruses. In the initial section, the strategy employed by these viruses to replicate their genomes is discussed. This would help in understanding the later section in which the use of these viruses as vaccine vectors has been discussed. For the description of the replication strategy which encompasses virus genome transcription and genome replication carried out by the same RNA dependent RNA polymerase complex, a member of the prototype rhabdovirus family - Chandipura virus has been chosen as an example to illustrate the complex nature of the two processes and their regulation. In the discussion on these viruses serving as vectors for carrying vaccine antigen genes, emphasis has been laid on describing the progress made in using the attenuated viruses as vectors and a description of the systems in which the efficiency of immune responses has been tested.

Replication of Japanese encephalitis virus in mouse brain induces alterations in lymphocyte response

The experimental model using intracerebral (i.c.) challenge was employed in many studies evaluating the protection against disease induced by Japanese encephalitis virus (JEV). We investigated alterations in peripheral lymphocyte response caused by i.c. infection of mice with JEV. Splenocytes from the i.c.-infected mice showed suppressed proliferative response to concanavalin A (con A) and anti-CD3 antibody stimulation. At the same time, the expression of CD25 (IL-2R) and production of IL-2 was inhibited. Addition of anti-CD28 antibody restored the decreased anti-CD3 antibody-mediated proliferation in the splenocytes. Moreover, the number of con A-stimulated cells secreting IL-4 was significantly reduced in splenocytes from i.c.-infected mice. These studies suggested that the i.c. infection with JEV might involve additional immune modulation effects due to massive virus replication in the brain.