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Volume 91,
Issue 8,
2010
Volume 91, Issue 8, 2010
- Animal
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- DNA viruses
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An analysis of clustering of betapapillomavirus antibodies
Betapapillomaviruses (βPVs) may contribute to the aetiology of cutaneous squamous cell carcinoma. However, no high-risk types have yet been identified, possibly because the high frequency of co-infection prevents a straightforward analysis of the independent effects of individual viruses. This study aimed to determine whether specific virus types were more likely to co-occur than others, thereby reducing the number of parameters needed in statistical models. Antibody data were analysed from controls who participated in case–control studies in The Netherlands, Italy and Australia and from participants in the German Nutrition Survey. Cluster analysis and two ordination techniques were used to identify patterns. Evidence of clustering was found only according to the number of viruses to which antibodies were detected. The lack of clustering of specific viral types identified suggests that if there are βPV types that are independently related to skin carcinogenesis, they are unlikely to be identified using standard epidemiological methods.
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Differences and changes in human papillomavirus type 16 variant status in human immunodeficiency virus-positive adults are not uncommon
Human papillomavirus type 16 (HPV-16) genotype variants have been the subject of several investigations, but study participants have rarely been sampled more than once. In this study, among a cohort of human immunodeficiency virus (HIV)-infected adults, HPV-16 variants were investigated in samples collected concurrently from the anus and cervix, as well as in serial samples collected from the same anatomical site at 12-month intervals. HPV-16 variants in stored extracts of cervical and anal samples were determined from subjects with multiple visits and at least one sample positive for HPV-16. Seven polymorphic nucleotide positions within the E6 region were analysed by pyrosequencing to determine genotype variants. Of 364 samples examined, 176 anal and 39 cervical swabs from 84 different subjects yielded unequivocal sequences of eight major HPV-16 variants. Eight samples contained probable novel HPV-16 variants and in one sample two variants were detected. In eight out of 29 (27.6 %) anal–cervical sample pairs positive for HPV-16, discordant variants were found. From 57 anal and nine cervical sample series of HPV-16-positive samples, a change in HPV-16 variant status over time was seen in nine (13.6 %) instances (seven anal and two cervical) from eight different participants. Changes in HPV-16 variants in HIV-infected adults were seen most frequently when different anatomical sites were sampled, but were also observed over time.
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Lack of association between the presence and persistence of betapapillomavirus DNA in eyebrow hairs and betapapillomavirus L1 antibodies in serum
Betapapillomavirus (βPV) DNA and seroresponses are highly prevalent in the general population and both are frequently used as infection markers in epidemiological studies to elucidate an association with cutaneous squamous cell carcinoma (SCC). Little is known about the natural history of βPV infection and the aspects of infection that drive antibody responses. To investigate the relationship between these markers, this study assessed whether the presence or persistence of βPV DNA in eyebrow hairs and L1 antibodies of the same βPV type co-occurred more frequently than would be expected by chance in both a cross-sectional assessment and a longitudinal study. βPV DNA in plucked eyebrow hairs and L1 antibodies in serum were measured in 416 participants of the Australian community-based Nambour Skin Cancer Study in 1996. Similar data were available for a subset of 148 participants in 2003. Observed co-occurrence of βPV DNA and antibodies was compared with expected values based on prevalence. A case-wise concordance index was used to calculate the overall concordance of βPV DNA and antibodies of the same type. No significant associations were found between the presence or persistence of βPV DNA and antibody responses. The age and sex of the host did not influence the association, and nor did SCC status or a history of sunburns. It was concluded that βPV antibody responses in adults are not primarily driven by βPV infection as measured in eyebrow hairs. Other factors, such as viral load, may play a more pivotal role in the induction of detectable seroresponses.
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Hepatitis B virus polymerase inhibits RIG-I- and Toll-like receptor 3-mediated beta interferon induction in human hepatocytes through interference with interferon regulatory factor 3 activation and dampening of the interaction between TBK1/IKKϵ and DDX3
More LessHepatitis B virus (HBV) infection remains one of the most serious health problems worldwide. Whilst studies have shown that HBV impairs interferon (IFN) production from dendritic cells in chronic hepatitis B patients, it remains unknown whether HBV inhibits IFN production in human hepatocytes. Using transient transfection assays in a primary human hepatocyte cell line (PH5CH8), this study demonstrated that HBV polymerase inhibits IFN-β promoter activity induced by Newcastle disease virus, Sendai virus or poly(I : C) in a dose-dependent manner, whilst ectopic expression of the HBV core and X proteins had no effect on IFN-β promoter activity. In addition, HBV polymerase blocked cellular IFN-β expression and consequent antiviral immunity revealed by an infection protection assay. Furthermore, overexpression of key molecules on the IFN-β induction axis, together with HBV polymerase, resulted in a block of IFN-β promoter activity triggered by RIG-I, IPS-1, TRIF, TBK1 and IKKϵ, but not by an IFN regulatory factor 3 dominant-positive mutant (IRF3-5D), suggesting that HBV polymerase prevents IFN-β expression at the TBK1/IKKϵ level. Further studies showed that HBV polymerase inhibited phosphorylation, dimerization and nuclear translocation of IRF3, in response to Sendai virus infection. Finally, it was shown that HBV polymerase-mediated dampening of the interaction between TBK1/IKKϵ and DDX3 may be involved in the inhibitory effect on IFN-β induction. Taken together, these findings reveal a novel role of HBV polymerase in HBV counteraction of IFN-β production in human hepatocytes.
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- Plant
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Genetic diversity and phylogeography of begomoviruses infecting legumes in Pakistan
More LessGrain legumes are an important source of dietary protein across southern Asia, but they suffer extensive losses due to several viruses that are members of the genus Begomovirus (family Geminiviridae), which are collectively known as legume yellow mosaic viruses (LYMVs). Despite their economic importance, little attention has been paid to LYMVs in Pakistan and only partial sequences of virus isolates originating from this country are available in the databases. Here, a survey of LYMVs occurring across Pakistan is described. Complete sequences of 44 components (23 DNA-A, 19 DNA-B and 2 betasatellites) were determined. The results show that only the mungbean yellow mosaic India virus (MYMIV) is of agricultural significance in Pakistan having been isolated from all cultivated grain legumes examined. Mungbean yellow mosaic virus, a significant crop pathogen in India, was only identified in a weed, which together with a novel species of LYMV we reported earlier, represents the first LYMV identified in non-cultivated plants. MYMIV was shown to occur as two types in Pakistan that show phylogeographical segregation. Additionally, two begomovirus species not considered pathogens of legumes and a betasatellite were isolated. This is of grave concern since it suggests that the presumed genetic isolation of the LYMVs in legumes may be being breached. LYMVs show little, if any, evidence of interspecific recombination with non-legume infecting begomoviruses. Thus, either recombination with non-legume viruses or interaction with betasatellites, which are host range and pathogenicity determining satellites of begomoviruses, could lead to the appearance of more aggressive virus variants/strains affecting legumes.
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Mutation of a chloroplast-targeting signal in Alternanthera mosaic virus TGB3 impairs cell-to-cell movement and eliminates long-distance virus movement
Cell-to-cell movement of potexviruses requires coordinated action of the coat protein and triple gene block (TGB) proteins. The structural properties of Alternanthera mosaic virus (AltMV) TGB3 were examined by methods differentiating between signal peptides and transmembrane domains, and its subcellular localization was studied by Agrobacterium-mediated transient expression and confocal microscopy. Unlike potato virus X (PVX) TGB3, AltMV TGB3 was not associated with the endoplasmic reticulum, and accumulated preferentially in mesophyll cells. Deletion and site-specific mutagenesis revealed an internal signal VL(17,18) of TGB3 essential for chloroplast localization, and either deletion of the TGB3 start codon or alteration of the chloroplast-localization signal limited cell-to-cell movement to the epidermis, yielding a virus that was unable to move into the mesophyll layer. Overexpression of AltMV TGB3 from either AltMV or PVX infectious clones resulted in veinal necrosis and vesiculation at the chloroplast membrane, a cytopathology not observed in wild-type infections. The distinctive mesophyll and chloroplast localization of AltMV TGB3 highlights the critical role played by mesophyll targeting in virus long-distance movement within plants.
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- Other Agents
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PrP-specific camel antibodies with the ability to immunodetect intracellular prion protein
More LessAlthough there is currently no effective treatment for prion diseases, significant advances have been made in suppressing its progress, using antibodies that block the conversion of PrPC into PrPSc. In order to be effective in treating individuals that have prion diseases, antibodies must be capable of arresting disease in its late stages. This requires the development of antibodies with higher affinity for PrPSc and systems for effective translocation of antibodies across the blood–brain barrier in order to achieve high concentrations of inhibitor at the site of protein replication. An additional advantage is the ability of these antibodies to access the cytosol of affected cells. To this end, we have generated PrP-specific antibodies (known as PrioV) by immunization of camels with murine scrapie material adsorbed to immunomagnetic beads. The PrioV antibodies display a range of specificities with some recognizing the PrP27–30 proteinase K-resistant fragment, others specific for PrPC and a number with dual binding specificity. Independent of their PrP conformation specificity, one of the PrioV antibodies (PrioV3) was shown to bind PrPC in the cytosol of neuroblastoma cells. In marked contrast, conventional anti-PrP antibodies produced in mouse against similar target antigen were unable to cross the neuronal plasma membrane and instead formed a ring around the cells. The PrioV anti-PrP antibodies could prove to be a valuable tool for the neutralization/clearance of PrPSc in intracellular compartments of affected neurons and could potentially have wider applicability for the treatment of so-called protein-misfolding diseases.
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Characterization of atypical scrapie cases from Great Britain in transgenic ovine PrP mice
Twenty-four atypical scrapie cases from sheep with different prion protein genotypes from Great Britain were transmitted to transgenic tg338 and/or TgshpXI mice expressing sheep PrP alleles, but failed to transmit to wild-type mice. Mean incubation periods were 200–300 days in tg338 mice and 300–500 days in TgshpXI mice. Survival times in C57BL/6 and VM/Dk mice were >700 days. Western blot analysis of mouse brain samples revealed similar multi-band, protease-resistant prion protein (PrPres) profiles, including an unglycosylated band at ∼8–11 kDa, which was shown by antibody mapping to correspond to the ∼93–148 aa portion of the PrP molecule. In transgenic mice, the incubation periods, Western blot PrPres profiles, brain lesion profiles and abnormal PrP (PrPSc) distribution patterns produced by the Great Britain atypical scrapie isolates were similar and compatible with the biological characteristics of other European atypical scrapie or Nor98 cases.
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Relevance of oral experimental challenge with classical scrapie in sheep
Oral inoculation is currently considered as the best approach to mimic natural TSE contamination in ruminants. In this study, we compared the timing of abnormal prion protein (PrPSc) dissemination and accumulation in the organism of susceptible sheep either orally inoculated or naturally infected with classical scrapie. Both animal groups shared a similar PrPSc dissemination scheme and accumulation dynamics in lymphoid tissues. However, orally challenged animals displayed an earlier neuro-invasion and a dramatically shorter incubation period than naturally exposed sheep. No differences were observed between the groups with regards to the neuro-invasion route. These results unambiguously indicate that oral inoculation can have an impact on both the earliness of neuro-invasion and the incubation period. They also support the statement that oral inoculation is a relevant model for investigating transmissible spongiform encephalopathy pathogenesis. Nevertheless, data obtained under such experimental conditions should be used with some caution.
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- Phage
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Phospholipids act as secondary receptor during the entry of the enveloped, double-stranded RNA bacteriophage φ6
More LessBacteriophage φ6 is the type member of the family Cystoviridae and infects Gram-negative Pseudomonas syringae cells. The virion consists of a protein-rich lipid envelope enclosing a nucleocapsid. The nucleocapsid covers the icosahedral polymerase complex that encloses the double-stranded RNA genome. Here, we demonstrate that nucleocapsid surface protein P8 is the single nucleocapsid component interacting with the cytoplasmic membrane. This interaction takes place between P8 and phospholipid. Based on this and previous studies, we propose a model where the periplasmic nucleocapsid interacts with the phospholipid head groups and, when the membrane voltage exceeds the threshold of 110 mV, this interaction drives the nucleocapsid through the cytoplasmic membrane, resulting in an intracellular vesicle containing the nucleocapsid.
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Volumes and issues
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Volume 106 (2025)
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Volume 2 (1968)
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Volume 1 (1967)
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