Virus taxonomy--1999. The universal system of virus taxonomy, updated to include the new proposals ratified by the International Committee on Taxonomy of Viruses during 1998

Establishment of five new genera in the family Geminiviridae: Citlodavirus, Maldovirus, Mulcrilevirus, Opunvirus, and Topilevirus

Geminiviruses are plant-infecting, circular single-stranded DNA viruses that have a geminate virion morphology. These viruses infect both cultivated and non-cultivated monocotyledonous and dicotyledonous plants and have a wide geographical distribution. Nine genera had been established within the family Geminiviridae (Becurtovirus, Begomovirus, Capulavirus, Curtovirus, Eragrovirus, Grablovirus, Mastrevirus, Topocuvirus, and Turncurtovirus) as of 2020. In the last decade, metagenomics approaches have facilitated the discovery and identification of many novel viruses, among them numerous highly divergent geminiviruses. Here, we report the establishment of five new genera in the family Geminiviridae (Citlodavirus, Maldovirus, Mulcrilevirus, Opunvirus, and Topilevirus) to formally classify twelve new, divergent geminiviruses.

Antiviral therapeutics directed against RNA dependent RNA polymerases from positive-sense viruses

Viruses with positive-sense single stranded RNA (+ssRNA) genomes are responsible for different diseases and represent a global health problem. In addition to developing new vaccines that protect against severe illness on infection, it is imperative to identify new antiviral molecules to treat infected patients. The genome of these RNA viruses generally codes for an enzyme with RNA dependent RNA polymerase (RdRP) activity. This molecule is centrally involved in the duplication of the RNA genome. Inhibition of this enzyme by small molecules will prevent duplication of the RNA genome and thus reduce the viral titer. An overview of the different therapeutic strategies used to inhibit RdRPs from +ssRNA viruses is provided, along with an analysis of these enzymes to highlight new binding sites for inhibitors.

Bluetongue in India: a systematic review and meta-analysis with emphasis on diagnosis and seroprevalence

Bluetongue (BT) is an infectious viral disease which affects a wide range of ruminants and was first reported in India in 1964. In view of the absence of comprehensive information on the BT status in India, this study presents the seroprevalence on BT in farm animals of India based-on a systematic review and meta-analysis. A systematic review was conducted to identify the published articles (2001–2018) reporting the seroprevalence of BT in sheep, goats, cattle, buffalo, camels, and Mithun (Bos frontalis) from India. From 409 research articles, 71 fulfilled the inclusion criteria and meta-analysis for proportions was carried out targeting the eligible studies. From these, 144 strata level data were extracted with a sample size of 14048 sheep, 14696 goats, 5218 cattle, 2653 buffaloes, 2062 camels, and 222 Mithun. Overall, the analyses showed that the BT seroprevalence of 43% (95% CI: 38–49%) in goats, 39% (95% CI: 33–46%) in sheep, 38% (95% CI: 25–45%) in cattle, 34% (95% CI: 20–51%) in buffaloes, 16% (95% CI: 10–22%) in camels, and 66% (95% CI: 17–95%) in Mithun. Furthermore, the meta-regression analysis suggested that serological tests, geographical region, and sample size were the prime moderators. Meta-analytic study indicates the BT seropositivity in 25.35 million sheep (95% CI: 21.5–29.9), 58 million goats (95% CI: 51.3–66.2), 66.8 million cattle (95% CI: 47.7–86), 37.0 million buffaloes (95% CI: 21.7–55.4), 0.06 million camels (95% CI: 0.04–0.09), and 0.19 million Mithun (95% CI: 0.05–0.28). The findings highlight the variation of BT seropositivity in different geographical regions of India.

Sheep pestivirus in Morocco: sero-epidemiological and molecular study

The present study is the first to investigate Border disease caused by the sheep pestivirus (SPV) in sheep herds in Morocco. Sero-epidemiological investigations were carried out in six regions of the Kingdom, known as important in terms of sheep breeding. A total of 760 blood samples were collected including aborted ewes from 28 randomly selected farms. The samples were analysed, for the determination of anti-pestivirus antibodies, using indirect ELISA technique. Next, reverse transcriptase PCR (RT-PCR) was conducted on serologically negative samples to identify possible persistently infected (PI) animals, through detection of specific RNA fragment. The results revealed an overall SPV seroprevalence in studied areas of 28.9%. The difference in seroprevalence between the six investigated regions was not statistically significant (p>0.05) and varied slightly from 20.9% to 37.5%. Furthermore, 93% of investigated farms were affected with an average seroprevalence of 22.7% (with a variation of 1%–74%). RT-PCR results were all negative, indicating the absence of PI animals in the tested samples. Nevertheless, the present study revealed that SPV is endemic in Morocco.

Whole-Genome Sequencing and Genomic Analysis of a Virulent Bacteriophage Infecting Bacillus cereus

OBJECTIVE

Infants with a weak immune system are prone to infection with Bacillus cereus, which is commonly found in natural environments. With the aim of achieving better control of this pathogenic bacterium, in the present study we characterized a new bacteriophage, ΦBC01.

METHODS

Bacteriophage particles were analyzed by transmission electron microscopy. Factors influencing adsorption were identified in a double-layer plaque assay. Sodium dodecyl sulfate polyacrylamide gel electrophoresis was conducted to determine the size of major structural proteins. The complete genome of the phage was analyzed.

RESULTS

Bacteriophage particles (105.3 ± 3.1 nm icosahedral head and 208.8 ± 3.6 nm contractile tail) were identified as Myoviridae. ΦBC01 was found to have host specificity to B. cereus. Major structural proteins of ΦBC01 showed 2 well-pronounced bands of 99 and 56 kDa. The 158,385-bp genome sequence of ΦBC01 was determined: 56 of the 239 open reading frames were annotated, indicating involvement in bacteriophage DNA manipulation, cell lysis, packaging, virion structure, and other functions.

CONCLUSION

Because of characterization and genotyping of a new bacteriophage from soil samples containing earthworms, this study provides a baseline for the development of alternatives to antibiotics.

Seroprevalence of peste des petits ruminants and bluetongue in goat population of Meghalaya, India

Aim:

This study aimed to determine the seroprevalence of peste des petits ruminants (PPR) and bluetongue (BT) in goats’ population in the state of Meghalaya of Northeast India.

Materials and Methods:

The serosurveillance study was done from the random sampling (n=598) of blood collected from five districts (Ri-Bhoi, East Khasi Hills, West Khasi Hills, Jaintia Hills and West Garo Hills) of Meghalaya. The presence of antibodies against PPR and BT in the samples was detected by indirect enzyme-linked immunosorbent assay (ELISA) method for PPR and competitive ELISA for BT.

Results:

The results showed the overall seropositivity of PPR and BT at 7.19% and 60.20%, respectively. West Garo Hills recorded the highest seroprevalence of both PPR (9.81%) and BT (68%) and 3.6% of the samples tested positive for both PPR and BT.

Conclusion:

The random survey results indicating the presence of PPR and BT have specific implication in epidemiological perspectives since it highlights the prevalence under natural situations, where the subclinical, inapparent, or non-lethal or recovery of infection was suspected in unvaccinated animals. It also warrants further studies to suggest appropriate control measures to prevent the spread of infection.

Comparative Neuropathology of Major Indian Bluetongue Virus Serotypes in a Neonatal BALB/c Mouse Model

Bluetongue virus (BTV) is neurotropic in nature, especially in ruminant fetuses and in-utero infection results in abortion and congenital brain malformations. The aim of the present study was to compare the neuropathogenicity of major Indian BTV serotypes 1, 2, 10, 16 and 23 by gross and histopathological lesions and virus distribution in experimentally infected neonatal BALB/c mice. Each BTV serotype (20 μl of inoculum containing 1 × 10⁵ tissue culture infectious dose [TCID]₅₀/ml of virus) was inoculated intracerebrally into 3-day-old mice, while a control group was inoculated with mock-infected cell culture medium. Infection with BTV serotypes 1, 2 and 23 led to 65-70% mortality at 7-9 days post infection (dpi) and caused severe necrotizing encephalitis with neurodegenerative changes in neurons, swelling and proliferation of vascular endothelial cells in the cerebral cortex, cerebellum, midbrain and brainstem. In contrast, infection with BTV serotypes 10 and 16 led to 25-30% mortality at 9-11 dpi and caused mild neuropathological lesions. BTV antigen was detected by immunohistochemistry, direct fluorescence antibody technique and confocal microscopy in the cytoplasm of neuronal cells of the hippocampus, grey matter of the cerebral cortex and vascular endothelial cells in the midbrain and brainstem of BTV-1, -2, -10, -16 and -23 infected groups from 3 to 20 dpi. BTV nucleic acid was detected in the infected brain tissues from as early as 24 h up to 20 dpi by VP7 gene segment-based one-step reverse transcriptase polymerase chain reaction. This study of the relative neurovirulence of BTV serotypes is likely to help design suitable vaccination and control strategies for the disease.

First report and genetic characterization of feline kobuvirus in diarrhoeic cats in China

Feline kobuvirus (FeKoV) is a newly discovered organism, classified under the species Aichivirus A of the genus Kobuvirus. Since it was first reported in 2013, molecular evidence for FeKoV in the feline population has been restricted to two countries: Korea and Italy. In this study, we collected faecal samples from cats in southern China and detected the FeKoV RNA in these samples. A prevalence rate of 9.9% (8/81) was identified by RT‐PCR, and all positive samples were obtained from diarrhoeic animals. In addition, FeKoV was shown positive associated with diarrhoea in cats, with a correlation coefficient of 0.25. Next, we designed three primer pairs with degenerate bases, which targeted the conservative overlapping region of the entire published FeKoV genome, and sequenced the near‐complete genome of the first Chinese field FeKoV strain, WHJ‐1, using long‐fragment PCR. Finally, we analysed WHJ‐1's homology and phylogeny using the polyprotein gene. The results indicated that FeKoV has rapidly mutated since it was first discovered. This study will help to better understand FeKoV's epidemiology, evolutionary pattern and genetic diversity.

Molecular evolution and phylogeography of infectious hematopoietic necrosis virus with a focus on its presence in France over the last 30 years

Infectious hematopoietic necrosis virus (IHNV) is among the most important pathogens affecting the salmonid industry. Here, we investigated the molecular evolution and circulation of isolates from 11 countries or regions all over the world, with a special focus on the epidemiological situation in France. The phylogeography, time to the most recent common ancestor (TMRCA) and nucleotide substitution rate were studied using 118 full-length glycoprotein gene sequences isolated from 9 countries (5 genogroups) over a period of 47 years. The TMRCA dates back to 1943, with the L genogroup identified as the likely root (67 %), which is consistent with the first report of this pathogen in the USA. A Bayesian inference approach was applied to the partial glycoprotein gene sequences of 88 representative strains isolated in France over the period 1987-2015. The genetic diversity of these 88 sequences showed mean nucleotide and amino-acid identities of 97.1 and 97.8 %, respectively, and a d _N/d _S ratio (non-synonymous to synonymous mutations) of 0.25, indicating purifying selection. The French viral populations are divided into eight sub-clades and four individual isolates, with a clear spatial differentiation, suggesting the predominant role of local reservoirs in contamination. The atypical 'signatures' of some isolates underlined the usefulness of molecular phylogeny for epidemiological investigations that track the spread of IHNV.

Attachment and Postattachment Receptors Important for Hepatitis C Virus Infection and Cell-to-Cell Transmission

Hepatitis C virus (HCV) requires multiple receptors for its attachment to and entry into cells. Our previous studies found that human syndecan-1 (SDC-1), SDC-2, and T cell immunoglobulin and mucin domain-containing protein 1 (TIM-1) are HCV attachment receptors. Other cell surface molecules, such as CD81, Claudin-1 (CLDN1), Occludin (OCLN), SR-BI, and low-density lipoprotein receptor (LDLR), function mainly at postattachment steps and are considered postattachment receptors. The underlying molecular mechanisms of different receptors in HCV cell-free and cell-to-cell transmission remain elusive. In the present study, we used a clustered regularly interspaced short palindromic repeat (CRISPR)-Cas9 technology, gene-specific small interfering RNAs, and a newly developed luciferase-based reporter system to quantitatively determine the importance of individual receptors in HCV cell-free and cell-to-cell transmission. Knockouts of SDC-1 and SDC-2 resulted in remarkable reductions of HCV infection and cell attachment, whereas SDC-3 and SDC-4 knockouts did not affect HCV infection. Defective HCV attachment to SDC-1 and/or SDC-2 knockout cells was completely restored by SDC-1 and SDC-2 but not SDC-4 expression. Knockout of the attachment receptors SDC-1, SDC-2, and TIM-1 also modestly decreased HCV cell-to-cell transmission. In contrast, silencing and knockout of the postattachment receptors CD81, CLDN1, OCLN, SR-BI, and LDLR greatly impaired both HCV cell-free and cell-to-cell transmission. Additionally, apolipoprotein E was found to be important for HCV cell-to-cell spread, but very-low-density lipoprotein (VLDL)-containing mouse serum did not affect HCV cell-to-cell transmission, although it inhibited cell-free infection. These findings demonstrate that attachment receptors are essential for initial HCV binding and that postattachment receptors are important for both HCV cell-free and cell-to-cell transmission.IMPORTANCE The importance and underlying molecular mechanisms of cell surface receptors in HCV cell-free and cell-to-cell transmission are poorly understood. The role of some of the HCV attachment and postattachment receptors in HCV infection and cell-to-cell spread remains controversial. Using CRISPR-Cas9-mediated knockouts of specific cellular genes, we demonstrate that both SDC-1 and SDC-2, but not SDC-3 or SDC-4, are bona fide HCV attachment receptors. We also used a newly developed luciferase-based reporter system to quantitatively determine the importance of attachment and postattachment receptors in HCV cell-to-cell transmission. SDC-1, SDC-2, TIM-1, and SR-BI were found to modestly promote HCV cell-to-cell spread. CD81, CLDN1, OCLN, and LDLR play more important roles in HCV cell-to-cell transmission. Likewise, apolipoprotein E (apoE) is critically important for HCV cell-to-cell spread, unlike VLDL-containing mouse serum, which did not affect HCV cell-to-cell spread. These findings suggest that the mechanism(s) of HCV cell-to-cell spread differs from that of cell-free infection.

Porcine circovirus type 2 ORF4 protein binds heavy chain ferritin

Porcine circovirus type 2 (PCV2) is the primary infectious agent of PCV-associated disease (PCVAD) in swine. ORF4 protein is a newly identified viral protein of PCV2 and is involved in virus-induced apoptosis. However, the molecular mechanisms of ORF4 protein regulation of apoptosis remain unclear, especially given there is no information regarding any cellular partners of the ORF4 protein. Here, we have utilized the yeast two-hybrid assay and identified four host proteins (FHC, SNRPN, COX8A and Lamin C) interacting with the ORF4 protein. Specially, FHC was chosen for further characterization due to its important role in apoptosis. GST pull-down, subcellular co-location and co-immunoprecipitation assays confirmed that the PCV2 ORF4 protein indeed interacted with the heavy-chain ferritin, which is an interesting clue that will allow us to determine the role of the ORF4 protein in apoptosis.

Computationally Efficient Multiscale Reactive Molecular Dynamics to Describe Amino Acid Deprotonation in Proteins

An important challenge in the simulation of biomolecular systems is a quantitative description of the protonation and deprotonation process of amino acid residues. Despite the seeming simplicity of adding or removing a positively charged hydrogen nucleus, simulating the actual protonation/deprotonation process is inherently difficult. It requires both the explicit treatment of the excess proton, including its charge defect delocalization and Grotthuss shuttling through inhomogeneous moieties (water and amino residues), and extensive sampling of coupled condensed phase motions. In a recent paper (J. Chem. Theory Comput. 2014, 10, 2729-2737), a multiscale approach was developed to map high-level quantum mechanics/molecular mechanics (QM/MM) data into a multiscale reactive molecular dynamics (MS-RMD) model in order to describe amino acid deprotonation in bulk water. In this article, we extend the fitting approach (called FitRMD) to create MS-RMD models for ionizable amino acids within proteins. The resulting models are shown to faithfully reproduce the free energy profiles of the reference QM/MM Hamiltonian for PT inside an example protein, the ClC-ec1 H(+)/Cl(-) antiporter. Moreover, we show that the resulting MS-RMD models are computationally efficient enough to then characterize more complex 2-dimensional free energy surfaces due to slow degrees of freedom such as water hydration of internal protein cavities that can be inherently coupled to the excess proton charge translocation. The FitRMD method is thus shown to be an effective way to map ab initio level accuracy into a much more computationally efficient reactive MD method in order to explicitly simulate and quantitatively describe amino acid protonation/deprotonation in proteins.

Effect of Soil Moisture Management on the Development of Potato mop-top virus-Induced Tuber Necrosis

Potato mop-top virus (PMTV), transmitted by Spongospora subterranea f. sp. subterranea, the causal agent of powdery scab in potato, has become one of the most important tuber necrosis viruses in the United States. The virus has been confirmed in six major potato-producing states in the United States since its identification in 2003. Currently, no control methods are available for PMTV or its vector. A growth-chamber experiment was conducted to investigate the potential of using moisture regime adjustments to manage tuber necrosis caused by PMTV. Two commercial potato cultivars with varying levels of sensitivity to PMTV, 'Dakota Crisp' and 'Ivory Crisp', were grown in soil obtained from a PMTV-infested field. Over the course of the plant growth cycle, plants of each cultivar were subjected to moisture regimes of wet throughout (WT), wet early/dry late (WEDL), dry early/wet late (DEWL), and dry throughout (DT). Soil moisture levels of 90 and 60% field capacity were considered wet and dry, respectively, while early and late refer to first and last 50 days after planting, respectively. Results of visual assessment conducted 3 months after storage showed significant differences in root gall formation, powdery scab on tubers, and PMTV tuber necrosis among moisture regimes. Powdery scab incidence was significantly higher in the WT and DEWL regimes than WEDL and DT regimes. PMTV tuber necrosis incidence did not differ between the WT and DEWL or between DEWL and WEDL moisture regimes. However, PMTV tuber necrosis incidence was significantly higher in WT than under WEDL and DT regimes. The incidence of PMTV tuber necrosis was significantly lower in the DT regime than in the other three moisture regimes. Severity of PMTV tuber necrosis was significantly higher in the WT than the other regimes, which did not differ statistically among themselves. A significant interaction was found between cultivar and moisture regime on root gall formation, with the highest number of galls found on Ivory Crisp grown in the WT moisture regime. A significant correlation was found between powdery scab incidence on tubers and PMTV-induced tuber necrosis incidence. The results of this study provide useful basic information upon which further work can be built for formulating irrigation management schemes that have the potential of reducing the likelihood of powdery scab infection and PMTV-induced tuber necrosis development in potato.

Sequence-independent amplification coupled with DNA microarray analysis for detection and genotyping of noroviruses

Noroviruses (NoVs) have high levels of genetic sequence diversities, which lead to difficulties in designing robust universal primers to efficiently amplify specific viral genomes for molecular analysis. We here described the practicality of sequence-independent amplification combined with DNA microarray analysis for simultaneous detection and genotyping of human NoVs in fecal specimens. We showed that single primer isothermal linear amplification (Ribo-SPIA) of genogroup I (GI) and genogroup II (GII) NoVs could be run through the same amplification protocol without the need to design and use any virus-specific primers. Related virus could be subtyped by the unique pattern of hybridization with the amplified product to the microarray. By testing 22 clinical fecal specimens obtained from acute gastroenteritis cases as blinded samples, 2 were GI positive and 18 were GII positive as well as 2 negative for NoVs. A NoV GII positive specimen was also identified as having co-occurrence of hepatitis A virus. The study showed that there was 100 % concordance for positive NoV detection at genogroup level between the results of Ribo-SPIA/microarray and the phylogenetic analysis of viral sequences of the capsid gene. In addition, 85 % genotype agreement was observed for the new assay compared to the results of phylogenetic analysis.

Expression of E2 gene of bovine viral diarrhea virus in Pichia pastoris: a candidate antigen for indirect Dot ELISA

The E2 gene containing the EcoR I and Not I sites of bovine viral diarrhea virus (BVDV) was amplified from the plasmid pMD-18T-E2 of the HB-bd isolated, and inserted into Pichia pastoris (P. pastoris) expression vector pPIC9K, and transfected into Escherichia coli DH5α. The recombinant plasmid pPIC9K-E2 was digested by the SalI restriction enzyme and transformed into the P. pastoris strain GS115 by electroporation. High copy integrative transformants were obtained by G418 screening and induced for expression with methanol. The expressed products in the culture medium were identified by the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), the Western blotting and the antibody test for immunity. An indirect Dot-ELISA for the detection of antibody against BVDV was established by the recombinant E2 protein as the coating antigen. The reaction conditions of the indirect Dot-ELISA were optimized. The coating concentration of the E2 recombinant protein antigen, the dilution of serum sample, the optimal concentration of HRP labeled antibody, the optimal blocking reagent and blocking time were studied. 100 sera samples from cows in the field were tested for the antibody against BVDV by the Dot-ELISA and the IDEXX HerdChek BVDV antibody ELISA kit simultaneously to compare the specificity, sensitivity and accuracy. The results showed that the expressed products in the culture medium resulted in single band of 44kDa by SDS-PAGE and Western blotting. The results of the immunogenicity assay indicated that the protein E2 expressed in P. pastoris could induce the experimental animals of the rabbit to produce BVDV specific antibodies. The results of the indirect Dot-ELISA showed that the optimal coating concentration of the E2 recombinant protein was 2.0μg/mL, the bovine serum dilution was 1:100, the optimal concentration of HRP-labeled rabbit anti-bovine antibody IgG was 1:500, and the optimal blocking reagent was 3% glutin-TBS and blocking for 45min. The indirect Dot-ELISA showed 96.7%, 92.5% and 95% in the terms of specificity, sensitivity and accuracy compared to the IDEXX ELISA test kit. The indirect Dot-ELISA using the E2 recombinant protein can be used for the detection of antibody against the BVDV and could be considered in the surveillance programs.

Multiscale simulation reveals a multifaceted mechanism of proton permeation through the influenza A M2 proton channel

The influenza A virus M2 channel (AM2) is crucial in the viral life cycle. Despite many previous experimental and computational studies, the mechanism of the activating process in which proton permeation acidifies the virion to release the viral RNA and core proteins is not well understood. Herein the AM2 proton permeation process has been systematically characterized using multiscale computer simulations, including quantum, classical, and reactive molecular dynamics methods. We report, to our knowledge, the first complete free-energy profiles for proton transport through the entire AM2 transmembrane domain at various pH values, including explicit treatment of excess proton charge delocalization and shuttling through the His37 tetrad. The free-energy profiles reveal that the excess proton must overcome a large free-energy barrier to diffuse to the His37 tetrad, where it is stabilized in a deep minimum reflecting the delocalization of the excess charge among the histidines and the cost of shuttling the proton past them. At lower pH values the His37 tetrad has a larger total charge that increases the channel width, hydration, and solvent dynamics, in agreement with recent 2D-IR spectroscopic studies. The proton transport barrier becomes smaller, despite the increased charge repulsion, due to backbone expansion and the more dynamic pore water molecules. The calculated conductances are in quantitative agreement with recent experimental measurements. In addition, the free-energy profiles and conductances for proton transport in several mutants provide insights for explaining our findings and those of previous experimental mutagenesis studies.

Population Movement and Virus Spreading: HEV Spreading in a Pilgrimage City, Mashhad in Northeast Iran; an Example

BACKGROUND

Hepatitis E Virus (HEV) infection is a significant public health concern and responsible for large outbreaks of acute hepatitis in poor sanitary and living conditions.

OBJECTIVES

To investigate the impact of population movements on virus spreading, a large-scale population-based survey was performed in a pilgrimage- tourism area, the great Mashhad, capital city of Khorasan province.

PATIENTS AND METHODS

A cross-sectional study was carried out among 1582 randomly selected individuals from general population of Mashhad, north east of Iran, between May to September 2009. Serum samples were tested for total anti-HEV antibody using a specific enzyme linked immunoassay (ELISA) kit.

RESULTS

The prevalence of HEV infection was 14.2% (225/1582) with a maximum of 25.5 % (14/55) in densely populated areas. The highest prevalence was observed in visitant areas (≥ 20%) near the holly shrine with crowded hotels and inns. The differences between these areas and other districts were statistically significant (P < 0.001). The findings indicated that 13.2% (95/718) of males and 15.0% (130/864) of females were HEV positive; this difference is not significant. Seroprevalence increases with age rising , from 12.8% in subjects less than five years to 28.6% in individuals with more than 65 years old. Although, there were no meaningful differences between HEV seropositivity and socio-economic status, Illiterate individuals were significantly at higher risk for infection than educated persons (P < 0.001).

CONCLUSIONS

These findings demonstrated that, high prevalence of HEV is related to populated district, which can reach to the highest rate in hotels and inns close to visitants. Traditional sanitation and water supplying systems are the second important factor for the virus transmission. Therefore, it can be concluded that such areas need efficient surveillance systems to prevent the spreading of infectious diseases.

Syndecan-1 serves as the major receptor for attachment of hepatitis C virus to the surfaces of hepatocytes

Our recent studies demonstrated that apolipoprotein E mediates cell attachment of hepatitis C virus (HCV) through interactions with the cell surface heparan sulfate (HS). HS is known to covalently attach to core proteins to form heparan sulfate proteoglycans (HSPGs) on the cell surface. The HSPG core proteins include the membrane-spanning syndecans (SDCs), the lycosylphosphatidylinositol-linked glypicans (GPCs), the basement membrane proteoglycan perlecan (HSPG2), and agrin. In the present study, we have profiled each of the HSPG core proteins in HCV attachment. Substantial evidence derived from our studies demonstrates that SDC1 is the major receptor protein for HCV attachment. The knockdown of SDC1 expression by small interfering RNA (siRNA)-induced gene silence resulted in a significant reduction of HCV attachment to Huh-7.5 cells and stem cell-differentiated human hepatocytes. The silence of SDC2 expression also caused a modest decrease of HCV attachment. In contrast, the siRNA-mediated knockdown of other SDCs, GPCs, HSPG2, and agrin had no effect on HCV attachment. More importantly, ectopic expression of SDC1 was able to completely restore HCV attachment to Huh-7.5 cells in which the endogenous SDC1 expression was silenced by specific siRNAs. Interestingly, mouse SDC1 is also fully functional in mediating HCV attachment when expressed in the SDC1-deficient cells, consistent with recent reports that mouse hepatocytes are also susceptible to HCV infection when expressing other key HCV receptors. Collectively, our findings demonstrate that SDC1 serves as the major receptor protein for HCV attachment to cells, providing another potential target for discovery and development of antiviral drugs against HCV.

Gene therapy: light is finally in the tunnel

After two decades of ups and downs, gene therapy has recently achieved a milestone in treating patients with Leber's congenital amaurosis (LCA). LCA is a group of inherited blinding diseases with retinal degeneration and severe vision loss in early infancy. Mutations in several genes, including RPE65, cause the disease. Using adeno-associated virus as a vector, three independent teams of investigators have recently shown that RPE65 can be delivered to retinal pigment epithelial cells of LCA patients by subretinal injections resulting in clinical benefits without side effects. However, considering the whole field of gene therapy, there are still major obstacles to clinical applications for other diseases. These obstacles include innate and immune barriers to vector delivery, toxicity of vectors and the lack of sustained therapeutic gene expression. Therefore, new strategies are needed to overcome these hurdles for achieving safe and effective gene therapy. In this article, we shall review the major advancements over the past two decades and, using lung gene therapy as an example, discuss the current obstacles and possible solutions to provide a roadmap for future gene therapy research.

Homologous recombination in negative sense RNA viruses

Recombination is an important process that influences biological evolution at many different levels. More and more homologous recombination events have been reported among negative sense RNA viruses recently. While sporadic authentic examples indicate that homologous recombination does occur, recombination seems to be generally rare or even absent in most negative sense RNA viruses, and most of the homologous recombination events reported in the literature were likely generated artificially due to lab contamination or inappropriate bioinformatics methods. Homologous recombination in negative sense RNA viruses should be reported with caution in the future, and only after stringent quality control efforts. Moreover, co-infection experiments should be performed to confirm whether recombination can occur.

Detection of and phylogenetic studies with avian metapneumovirus recovered from feral pigeons and wild birds in Brazil

The aim of the present study was to determine whether avian metapneumovirus (aMPV)-related viruses were present in wild and synanthropic birds in Brazil. Therefore, we analysed samples from wild birds, feral pigeons and domestic chickens in order to perform a phylogenetic comparison. To detect the presence of aMPV, a nested reverse transcriptase-polymerase chain reaction was performed with the aim of amplifying a fragment of 270 bases for subtype A and 330 bases for subtype B, comprising the gene coding the G glycoprotein. Positive samples for aMPV subtypes A and B were found in seven (13.2%) different asymptomatic wild birds and pigeons (50%) that had been received at the Bosque dos Jequitibás Zoo Triage Center, Brazil. Also analysed were positive samples from 15 (12.9%) domestic chickens with swollen head syndrome from several regions of Brazil. The positive samples from wild birds, pigeons and domestic chickens clustered in two major phylogenetic groups: some with aMPV subtype A and others with subtype B. The similarity of the G fragment nucleotide sequence of aMPV isolated from chickens and synanthropic and wild avian species ranged from 100 to 97.5% (from 100 to 92.5% for the amino acids). Some positive aMPV samples, which were obtained from wild birds classified in the Orders Psittaciformes, Anseriformes and Craciformes, clustered with subtype A, and others from the Anas and Dendrocygma genera (Anseriformes Order) with subtype B. The understanding of the epizootiology of aMPV is very important, especially if this involves the participation of non-domestic bird species, which would add complexity to their control on farms and to implementation of vaccination programmes for aMPV.

Ultrastructure of Felis catus whole fetus (Fcwf-4) cell culture following infection with feline coronavirus

Feline coronavirus (FCoV) consists of two biotypes based on their growth in cell culture and their antigenicity. Infections with FCoV are highly prevalent in the cat population worldwide. In this study, Felis catus whole fetus (Fcwf-4)cell culture was infected with FCoV UPM11C/08. Virus multiplication in cell culture was monitored and examined under the transmission electron microscope. The virus particles revealed the characteristic morphology of feline FCoV represented by envelope viruses surrounded by peplomers. Virus attachment and entry into the cell occurred 15 h post-infection (pi), and the myriad of virus particles were observed both extracellularly and intracellularly after 48 h pi. Thereafter, intracellular virus particles were observed to be present in vacuoles or present freely in the cytoplasm.

The C-terminal alpha-helix domain of apolipoprotein E is required for interaction with nonstructural protein 5A and assembly of hepatitis C virus

We have recently demonstrated that human apolipoprotein E (apoE) is required for the infectivity and assembly of hepatitis C virus (HCV) (K. S. Chang, J. Jiang, Z. Cai, and G. Luo, J. Virol. 81:13783-13793, 2007; J. Jiang and G. Luo, J. Virol. 83:12680-12691, 2009). In the present study, we have determined the molecular basis underlying the importance of apoE in HCV assembly. Results derived from mammalian two-hybrid studies demonstrate a specific interaction between apoE and HCV nonstructural protein 5A (NS5A). The C-terminal third of apoE per se is sufficient for interaction with NS5A. Progressive deletion mutagenesis analysis identified that the C-terminal α-helix domain of apoE is important for NS5A binding. The N-terminal receptor-binding domain and the C-terminal 20 amino acids of apoE are dispensable for the apoE-NS5A interaction. The NS5A-binding domain of apoE was mapped to the middle of the C-terminal α-helix domain between amino acids 205 and 280. Likewise, deletion mutations disrupting the apoE-NS5A interaction resulted in blockade of HCV production. These findings demonstrate that the specific apoE-NS5A interaction is required for assembly of infectious HCV. Additionally, we have determined that using different major isoforms of apoE (E2, E3, and E4) made no significant difference in the apoE-NS5A interaction. Likewise, these three major isoforms of apoE are equally compatible with infectivity and assembly of infectious HCV, suggesting that apoE isoforms do not differentially modulate the infectivity and/or assembly of HCV in cell culture.

Effects of cyclosporin A induced T-lymphocyte depletion on the course of avian Metapneumovirus (aMPV) infection in turkeys

The avian Metapneumovirus (aMPV) causes an economically important acute respiratory disease in turkeys (turkey rhinotracheitis, TRT). While antibodies were shown to be insufficient for protection against aMPV-infection, the role of T-lymphocytes in the control of aMPV-infection is not clear. In this study we investigated the role of T-lymphocytes in aMPV-pathogenesis in a T-cell-suppression model in turkeys. T-cell-intact turkeys and turkeys partly depleted of functional CD4(+) and CD8(+) T-lymphocytes by Cyclosporin A (CsA) treatment were inoculated with the virulent aMPV subtype A strain BUT 8544. CsA-treatment resulted in a significant reduction of absolute numbers of circulating CD4(+) and CD8alpha(+) T-lymphocytes by up to 82 and 65%, respectively (P<0.05). Proportions of proliferating T-cells within mitogen-stimulated peripheral blood mononuclear cells were reduced by similar levels in CsA-treated birds compared to untreated controls (P<0.05). CsA-treated turkeys showed delayed recovery from aMPV-induced clinical signs and histopathological lesions and a prolonged detection of aMPV in choanal swabs. The results of this study show that T-lymphocytes play an important role in the control of primary aMPV-infection in turkeys.

Caspase-3/-8/-9, Bax and Bcl-2 expression in the cerebellum, lymph nodes and leukocytes of dogs naturally infected with canine distemper virus

Canine distemper is an immunosuppressive disease caused by the canine distemper virus (CDV). Pathogenesis mainly involves the central nervous system and immunosuppression. Dogs naturally infected with CDV develop apoptotic cells in lymphoid tissues and the cerebellum, but this apoptotic mechanism is not well characterized. To better understand this process, we evaluated the expression of Bax, Bcl-2, and caspase-3, -8 and -9, by evaluating mRNA levels in the peripheral blood, lymph nodes and cerebellum of CDV-infected (CDV+) and uninfected (CDV-) dogs by real-time polymerase chain reaction (PCR). Blood samples from 12 CDV+ and 8 CDV- dogs, diagnosed by reverse transcription-PCR, were subjected to hematological analysis and apoptotic gene expression was evaluated using real-time-PCR. Tissues from the cerebellum and lymph nodes of four CDV+ and three CDV-dogs were also subjected to real time-PCR. No significant differences were found between CDV+ and CDV- dogs in the hemotological results or in the expression of caspase-3, -8, -9, Bax, and Bcl-2 in the peripheral blood. However, expression of Bax, caspase-3, -8 and -9 was significantly higher in the cerebellum of CDV+ compared to CDV- dogs. Expression of caspase-3 and -8 was significantly higher in the lymph nodes of CDV+ compared to CDV- dogs. We concluded that infection with CDV induces apoptosis in the cerebellum and lymph nodes in different ways. Lymph node apoptosis apparently occurs via caspase-3 activation, through the caspase-8 pathway, and cerebellum apoptosis apparently occurs via caspase-3 activation, through the caspase-8 and mitochondrial pathways.

Characterization of the biosynthesis and cell surface expression of avian metapneumovirus attachment glycoprotein

Biosynthesis, glycosylation and cell surface expression of the AMPV/C G protein were examined in eukaryotic cell lines (LLC-MK2, CHO-K1, CHO-1d1D). Immature G gene products with a molecular mass of 42, 45 and 58-90 kilodaltons (kDa) were identified by SDS-PAGE and represented glycosylated intermediates. Tunicamycin treatment of transfected cells confirmed the presence of N-linked carbohydrate moieties on these intermediate species and identified a 38 kDa unglycosylated precursor. A fully processed, mature form of the protein migrated around 110 kDa. The presence of O-linked sugars on the mature G protein was confirmed by using the O-glycosylation deficient CHO-ldlD cell line supplemented with exogenous Gal and GalNAc. Binding of the lectin Arachis hypogaea (peanut agglutinin) confirmed the presence of O-linked sugars on the mature protein and its intracellular transport to the cell surface was demonstrated by indirect immunofluorescent staining.

Dimerization of hepatitis E virus capsid protein E2s domain is essential for virus-host interaction

Hepatitis E virus (HEV), a non-enveloped, positive-stranded RNA virus, is transmitted in a faecal-oral manner, and causes acute liver diseases in humans. The HEV capsid is made up of capsomeres consisting of homodimers of a single structural capsid protein forming the virus shell. These dimers are believed to protrude from the viral surface and to interact with host cells to initiate infection. To date, no structural information is available for any of the HEV proteins. Here, we report for the first time the crystal structure of the HEV capsid protein domain E2s, a protruding domain, together with functional studies to illustrate that this domain forms a tight homodimer and that this dimerization is essential for HEV–host interactions. In addition, we also show that the neutralizing antibody recognition site of HEV is located on the E2s domain. Our study will aid in the development of vaccines and, subsequently, specific inhibitors for HEV.

Infectious viral hepatitis is a major disease in both developing and developed countries. Hepatitis E virus (HEV) is one of the major causes of severe inflammation of the liver, which is characterized by jaundice, fever, liver enlargement, and abdominal pain in humans and non-human primates. The hepatitis E virus capsid is made up of individual subunits consisting of homodimers of a single structural protein forming the virus shell. These dimers are believed to protrude from the viral surface and to interact with host cells to initiate infection. To date, no structural information is available for any of the HEV proteins. This article reports the crystal structure of the HEV capsid protein domain E2s (protruding domain), along with functional studies, which illustrate the tight homodimeric state of E2s and that dimerization is essential for both HEV–host interactions and disease progression. We also show that the neutralizing antibody recognition site of HEV is located on the E2s domain. The present findings will aid the development of vaccines and novel inhibitors for HEV.

Molecular epidemiology of hepatitis E virus in Hong Kong

Hepatitis E virus (HEV) is one of the major causes of acute and self-limiting hepatitis in human. In Hong Kong, the number of notifications increased from 26 to 62 from year 2001 to 2007. This study describes the molecular epidemiology of HEV in Hong Kong in order to determine the movement and distribution of HEV. HEV in 171 serum samples from HEV IgM positive cases from year 2001 to 2007 were amplified using RT-PCR and subjected to nucleotide sequencing. Phylogenetic analysis showed 162 of 171 HEV detected cases (94.7%) belonged to genotype IV and 8 (4.7%) to genotype I. Interestingly, a cluster of 10 cases in year 2007 that had the same sequence of HEV was identified. Epidemiological data however did not detect any relationship between these cases. Since zoonotic transmission is a well known route of HEV infection, close monitoring of the circulating HEV strains in human and food source animals may help to provide additional information on the transmission of HEV and possible source of infection in Hong Kong.

Increase of pro-inflammatory cytokine expression in non-demyelinating early cerebral lesions in nervous canine distemper

Canine distemper virus (CDV) infection of the central nervous system results in lesions of the gray and white matter. While a biphasic disease process has been discussed for leukoencephalitis with a prominent loss of viral protein expression, polioencephalitis has been associated with virus persistence. Using semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR), expression of pro- and anti-inflammatory cytokines such as interleukin (IL)-1beta, IL-2, IL-6, IL-8, IL-10, IL-12, tumor necrosis factor-alpha (TNF)-alpha, interferon (IFN)-gamma, and transforming growth factor (TGF)-beta were studied in the cerebra of distemper dogs with white matter lesions in the cerebellum. Additionally, cytokine values were correlated with the degree of CDV infection, major histocompatibility complex class II (MHC II) expression, and infiltration of CD4-, CD8-, and CD3epsilon-positive lymphocytes. Cerebral CDV infection was not associated with detectable light microscopic lesions or infiltration of B and T lymphocytes. However, an increasing number of CDV-antigen-positive cells was associated with an upregulation of MHC II antigen. RT-PCR results revealed a significant upregulation of IL-6, IL-8, IL-12, and TNF-alpha in the cerebra of distemper dogs, whereas IL-10 and TGF-beta showed no significant increase. Elevated cytokine values were directly related to the presence of CDV antigen and MHC II upregulation. However, succeeding increases of the latter did not result in an additional proportional elevation of cytokine expression values. In summary, the present study demonstrates the expression of pro-inflammatory cytokines by resident neural cells following CDV infection. Furthermore, the lack of light microscopic changes indicates that additional factors besides cytokines are necessary for the development of a distemper-characteristic neuropathology.

Efficient production of type 2 porcine circovirus-like particles by a recombinant baculovirus

The capsid protein of PCV2 was expressed by using a recombinant baculovirus with insect Tn5 cells. A large amount of 28-kDa protein was released into the culture medium and self-assembled into PCV2-like particles (PCV2-LPs) with a buoyant density of 1.365 g/cm(3) and a diameter of 20 nm. PCV2-LPs were efficiently expressed, yielding 1 mg of purified particles per 10(7) Tn5 cells. The PCV2-LPs have antigenicity similar to that of authentic PCV2 particles, allowing us to develop a method for sensitively detecting PCV2-specific IgG antibodies. In addition, the PCV2-LPs appeared to be the most promising PCV2 vaccine candidate, by virtue of their potent immunogenicity.

Rapid detection and differentiation of wild-type and three attenuated lapinized vaccine strains of classical swine fever virus by reverse transcription polymerase chain reaction

A simple one-step reverse transcription polymerase chain reaction (RT-PCR) method was developed based on T-rich insertions in the viral genome for simultaneous detection and differentiation of wild type and vaccine strains of Classical swine fever virus (CSFV). The CSFV-specific primers were designed to contain the sequences of the T-rich insertion sites that exist uniquely in the 3' nontranslated regions (3' NTR) of the genome of lapinized CSFV vaccine strains. By using a one-step RT-PCR or a nested PCR followed by an agarose gel electrophoresis or a multicapillary electrophoresis, the wild-type and lapinized vaccine strains of CSFV in clinical samples could be detected and accurately distinguished. These assays can be applied to at least 3 attenuated lapinized vaccine strains, lapinized Philippines Coronel (LPC), hog cholera lapinized virus (HCLV), and Chinese strain (C strain). The detection limit of the wild-type virus was 6.3 TCID(50) (50% tissue culture infective dose)/ml for RT-PCR and 0.63 TCID(50)/ml for nested PCR. In previous studies, notable T-rich insertions of 12-13 nucleotides (nt) were found in the 3' NTR of the genome of lapinized vaccine strains of CSFV. However, this study discovered that 2 T-rich insertions, 42 and 36 nt in length, are present in the viral genome of lapinized vaccine strains LPC/PRK (primary rabbit kidney) and LPC/TS (Tam-Sui), respectively. These T-rich insertions of 12, 36, and 42 nt length increases the size of PCR fragments, which are favorable genetic markers for rapid detection of and differentiation between wild-type and different lapinized vaccine strains of CSFV.

Relationships of gag-pol diversity between Ty3/Gypsy and Retroviridae LTR retroelements and the three kings hypothesis

BACKGROUND

The origin of vertebrate retroviruses (Retroviridae) is yet to be thoroughly investigated, but due to their similarity and identical gag-pol (and env) genome structure, it is accepted that they evolve from Ty3/Gypsy LTR retroelements the retrotransposons and retroviruses of plants, fungi and animals. These 2 groups of LTR retroelements code for 3 proteins rarely studied due to the high variability - gag polyprotein, protease and GPY/F module. In relation to 3 previously proposed Retroviridae classes I, II and II, investigation of the above proteins conclusively uncovers important insights regarding the ancient history of Ty3/Gypsy and Retroviridae LTR retroelements.

RESULTS

We performed a comprehensive study of 120 non-redundant Ty3/Gypsy and Retroviridae LTR retroelements. Phylogenetic reconstruction inferred based on the concatenated analysis of the gag and pol polyproteins shows a robust phylogenetic signal regarding the clustering of OTUs. Evaluation of gag and pol polyproteins separately yields discordant information. While pol signal supports the traditional perspective (2 monophyletic groups), gag polyprotein describes an alternative scenario where each Retroviridae class can be distantly related with one or more Ty3/Gypsy lineages. We investigated more in depth this evidence through comparative analyses performed based on the gag polyprotein, the protease and the GPY/F module. Our results indicate that contrary to the traditional monophyletic view of the origin of vertebrate retroviruses, the Retroviridae class I is a molecular fossil, preserving features that were probably predominant among Ty3/Gypsy ancestors predating the split of plants, fungi and animals. In contrast, classes II and III maintain other phenotypes that emerged more recently during Ty3/Gypsy evolution.

CONCLUSION

The 3 Retroviridae classes I, II and III exhibit phenotypic differences that delineate a network never before reported between Ty3/Gypsy and Retroviridae LTR retroelements. This new scenario reveals how the diversity of vertebrate retroviruses is polyphyletically recurrent into the Ty3/Gypsy evolution, i.e. older than previously thought. The simplest hypothesis to explain this finding is that classes I, II and III trace back to at least 3 Ty3/Gypsy ancestors that emerged at different evolutionary times prior to protostomes-deuterostomes divergence. We have called this "the three kings hypothesis" concerning the origin of vertebrate retroviruses.

Taxonomy, molecular phylogeny and evolution of plant reverse transcribing viruses (family Caulimoviridae) inferred from full-length genome and reverse transcriptase sequences

This study constitutes the first evaluation and application of quantitative taxonomy to the family Caulimoviridae and the first in-depth phylogenetic study of the family Caulimoviridae that integrates the common origin between LTR retrotransposons and caulimoviruses. The phylogenetic trees and PASC analyses derived from the full genome and from the corresponding partial RT concurred, providing strong support for the current genus classification based mainly on genome organisation and use of partial RT sequence as a molecular marker. The PASC distributions obtained are multimodal, making it possible to distinguish between genus, species and strain. The taxonomy of badnaviruses infecting banana (Musa spp.) was clarified, and the consequence of endogenous badnaviruses on the genetic diversity and evolution of caulimoviruses is discussed. The use of LTR retrotransposons as outgroups reveals a structured bipolar topology separating the genus Badnavirus from the other genera. Badnaviruses appear to be the most recent genus, with the genus Tungrovirus in an intermediary position. This structuring intersects the one established by genomic and biological properties and allows us to make a correlation between phylogeny and biogeography. The variability shown between members of the family Caulimoviridae is in a similar range to that reported within other DNA and RNA plant virus families.

The Gypsy Database (GyDB) of mobile genetic elements

In this article, we introduce the Gypsy Database (GyDB) of mobile genetic elements, an in-progress database devoted to the non-redundant analysis and evolutionary-based classification of mobile genetic elements. In this first version, we contemplate eukaryotic Ty3/Gypsy and Retroviridae long terminal repeats (LTR) retroelements. Phylogenetic analyses based on the gag-pro-pol internal region commonly presented by these two groups strongly support a certain number of previously described Ty3/Gypsy lineages originally reported from reverse-transcriptase (RT) analyses. Vertebrate retroviruses (Retroviridae) are also constituted in several monophyletic groups consistent with genera proposed by the ICTV nomenclature, as well as with the current tendency to classify both endogenous and exogenous retroviruses by three major classes (I, II and III). Our inference indicates that all protein domains codified by the gag-pro-pol internal region of these two groups agree in a collective presentation of a particular evolutionary history, which may be used as a main criterion to differentiate their molecular diversity in a comprehensive collection of phylogenies and non-redundant molecular profiles useful in the identification of new Ty3/Gypsy and Retroviridae species. The GyDB project is available at http://gydb.uv.es.

Severe malformations in calves associated with bovine viral diarrhoea (BVD) virus infection in a dairy cattle herd

During late may 2004, Some dairy cows at Al-Kharj area of central Saudi Arabia, gave birth to severely malformed calves which died, few hours to few days following birth. Samples were collected from the affected calves and their dams of virological and serological investigations. Bovine viral diarrhoea virus was detected by capture enzyme linked immuno-sorbent assay (ELISA) in the brains of affected calves. Serum antibodies were detected in the dams. The present study indicated that in spite of vaccination against BVD in the country, still severe affections of the disease are encountered. Further insight epidemiological studies to elucidate the BVD situation in Saudi Arabia is urgently needed.

A genetically engineered prime-boost vaccination strategy for oculonasal delivery with poly(D,L-lactic-co-glycolic acid) microparticles against infection of turkeys with avian Metapneumovirus

In this study we demonstrated the use of an oculonasally delivered poly(D,L-lactic-co-glycolic acid) microparticle (PLGA-MP)-based and genetically engineered vaccination strategy in the avian system. An avian Metapneumovirus (aMPV) fusion (F) protein-encoding plasmid vaccine and the corresponding recombinant protein vaccine were produced and bound to or encapsulated by PLGA-MP, respectively. The PLGA-MP as the controlled release system was shown in vitro to not induce any cytopathic effects and to efficiently deliver the F protein-based aMPV-vaccines to avian cells for further processing. Vaccination of turkeys was carried out by priming with an MP-bound F protein-encoding plasmid vaccine and a booster-vaccination with an MP-encapsulated recombinant F protein. Besides the prime-boost F-specific vaccinated birds, negative control birds inoculated with a mock-MP prime-boost regimen as well as non-vaccinated birds and live vaccinated positive control birds were included in the study. The MP-based immunization of turkeys via the oculonasal route induced systemic humoral immune reactions as well as local and systemic cellular immune reactions, and had no adverse effects on the upper respiratory tract. The F protein-specific prime-boost strategy induced partial protection. After challenge the F protein-specific MP-vaccinated birds showed less clinical signs and histopathological lesions than control birds of mock MP-vaccinated and non-vaccinated groups did. The vaccination improved viral clearance and induced accumulation of local and systemic CD4+ T cells when compared to the mock MP-vaccination. It also induced systemic aMPV-neutralizing antibodies. The comparison of mock- and F protein-specific MP-vaccinated birds to non-vaccinated control birds suggests that aMPV-specific effects as well as adjuvant effects mediated by MP may have contributed to the overall protective effect.

Hepatitis E virus

Hepatitis E virus (HEV) is the aetiological agent of non-HAV enterically transmitted hepatitis. It is the major cause of sporadic as well as epidemic hepatitis, which is no longer confined to Asia and developing countries but has also become a concern of the developed nations. In the Indian subcontinent, it accounts for 30-60% of sporadic hepatitis. It is generally accepted that hepatitis E is mostly self-limited and never progresses to chronicity. It has a higher mortality in pregnant women where the disease condition is accentuated with the development of fulminant liver disease. Currently, no antiviral drug or vaccine is licensed for HEV, although a vaccine candidate is in clinical trials. HEV genome is 7.2kb in size with three open reading frames (ORFs) and 5' and 3' cis acting elements, which have important roles to play in HEV replication and transcription. ORF1 codes for methyl transferase, protease, helicase and replicase; ORF2 codes for the capsid protein and ORF3 for a protein of undefined function. HEV has recently been classified in the genus Hepevirus of the family Hepeviridae. There are four major recognised genotypes with a single known serotype. The absence of a reliable in vitro propagation system is an obstacle to deciphering HEV biology. The genome of HEV has been cloned, sequenced and the infectious nature of these replicons has been established. However, questions related to replication, transcription, virus-host interactions and pathogenesis remain to be answered. This comprehensive review summarises the progress made so far in HEV research, and addresses some of the unanswered questions.

Establishment of an immortal turkey turbinate cell line suitable for avian metapneumovirus propagation

Until recently, there has not been a homologous avian cellular substrate which could continuously produce high titer avian metapneumovirus (AMPV); development of such a cell line should provide an excellent model system for studying AMPV infection. We have established a non-tumorigenic immortal turkey turbinate cell line (TT-1) to propagate sufficiently high AMPV titers. Currently, immortal TT-1 cells are growing continuously at 1.2-1.4 population doublings per day and are at passage 160. Kinetic analysis suggests that AMPV can infect and replicate more rapidly in TT-1 compared to Vero cells, although both cell types undergo apoptosis upon infection. The non-tumorigenic, reverse transcriptase negative TT-1 cell line can serve as an excellent homologous cellular substrate for virus propagation.

Truncated E2 of bovine viral diarrhea virus (BVDV) expressed in Drosophila melanogaster cells: a candidate antigen for a BVDV ELISA

A simple and reliable indirect enzyme-linked immunosorbent assay for detection of antibodies directed against a major bovine viral diarrhea virus (BVDV) immunogen, the E2 glycoprotein (tE2-ELISA), has been developed using the recombinant C-terminal truncated E2 glycoprotein (tE2) expressed in a Drosophila melanogaster system. This strategy demonstrated that tE2 is secreted efficiently in the supernatant, no purification steps are necessary, it is easy to produce and carries out the post translational modifications necessary to preserve its native conformation. Preliminary analysis of 183 cattle serum samples using tE2-ELISA showed a 98% specificity and a 100% sensitivity compared with the standard homologous BVDV virus neutralization test. The results also showed that the tE2 is immunoreactive because the conformation and antigenicity of the original E2 are maintained to a large extent. To our knowledge this is the first study report of the recombinant tE2 of BVDV expressed in D. melanogaster system as an antigen for ELISA.