| 1. |
- Ekström, Johanna, et al.
(författare)
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Cutaneous human papillomavirus 88: Remarkable differences in viral load.
- 2008
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Ingår i: International Journal of Cancer. - : Wiley. - 0020-7136 .- 1097-0215. ; 122:2, s. 477-480
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Tidskriftsartikel (refereegranskat)abstract
- A human papillomavirus (HPV) was cloned from a patient with multiple squamous cell carcinomas (SCCs) and identified as HPV88, recently categorized into a new species within the genus Gamma. The HPV88 viral load in an SCC of the index patient exceeded 1 million copies/cell. By contrast, a survey of 447 skin lesions (79 actinic keratoses, 73 seborrhoeic keratoses, 169 basal cell carcinomas and 126 SCCs) and 362 healthy skin biopsies found detectable HPV88 DNA in only 7 specimens. All these had very low viral loads (<1 copy/10(3) cells) implying extreme biological variability in viral load.
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| 2. |
- Ekström, Jens-Ola
(författare)
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Ljungan Virus Replication in Cell Culture
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Ljungan virus (LV) is a recently identified picornavirus of the genus Parechovirus. LV has been isolated from voles trapped in Sweden and also in the United States. LV infected small rodents may suffer from diabetes type 1 and type 2 like symptoms, myocarditis and encephalitis. LV has been proposed as a human pathogen, with indications of causing diabetes type 1, myocarditis and intrauterine fetal deaths.In this thesis, cell culture adapted LV strains were utilised for development and adaptation of several basic methodological protocols to study the LV biology, e.g. real time PCR, highly specific antibodies and a reverse genetics system. These methods allowed detailed studies of this virus and how it interacts with the host cell. The genomic 5'-end was identified and modelling showed unique secondary structure folding of this region. The LV encodes an aphthovirus-like 2A protein with a DvExNPGP motif. This motif was found to mediate primary cleavage of the LV polyprotein in vitro and is proposed to constitute the carboxy terminus of the structural protein VP1 in LV. Rabbit polyclonal antibodies generated against recombinant structural proteins were used to verify that the LV virion is composed of the structural proteins VP0, VP1 and VP3. Cell culture studies showed that LV replicates to low titer with an absent or delayed cell lysis. LV is proposed to be able to spread by a, for picornaviruses, not previously demonstrated direct cell-to-cell transmission. All results taken together suggest a maintenance strategy of LV including low amounts of the LV genome and persistently infected hosts. Stability studies showed that the LV virion not only maintain activity in acidic and alkaline environments but also exhibit resistance to the commonly used disinfectant Virkon®.The results presented in this thesis show that LV has several unique properties, not previously observed for a picornavirus.
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| 3. |
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| 4. |
- Ekström, Jens-Ola, et al.
(författare)
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Replication of Ljungan virus in cell culture : the genomic 5'-end, infectious cDNA clones and host cell response to viral infections
- 2007
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Ingår i: Virus Research. - : Elsevier BV. - 0168-1702 .- 1872-7492. ; 130:1-2, s. 129-139
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Tidskriftsartikel (refereegranskat)abstract
- Ljungan virus (LV) is a picornavirus recently isolated from bank voles (Clethrionomys glareolus). The previously uncharacterised 5'-end sequence of the LV genome was determined. Infectious cDNA clones were constructed of the wild type LV prototype strain 87-012 and of the cytolytically replicating cell culture adapted variant 87-012G. Virus generated from cDNA clones showed identical growth characteristics as uncloned virus stocks. Cell culture adapted LV, 87-012G, showed a clear cytopathic effect (CPE) at 3-4 days post-infection (p.i.). Virus titers, determined by plaque titration, increased however only within the first 18h p.i. Replication of LV (+) strand RNA was determined by real-time PCR and corresponded in time with increasing titers. In contrast, the amounts of the replication intermediate, the (-) strand, continued to increase until the cells showed CPE. This indicates separate controlling mechanisms for replication of LV (+) and (-) genome strands. Replication was also monitored by immunofluorescence (IF) staining. IF staining of both prototype 87-012 and the CPE causing 87-012G showed groups of 5-25 infected cells at 48h p.i., suggesting a, for picornaviruses, not previously described direct cell-to-cell transmission.
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| 5. |
- Ekström, Johanna, et al.
(författare)
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Staphylococcus aureus and Squamous Cell Carcinoma of the Skin.
- 2009
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Ingår i: Cancer Epidemiology Biomarkers & Prevention. - 1538-7755. ; 18:2, s. 472-478
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Tidskriftsartikel (refereegranskat)abstract
- Squamous cell carcinoma (SCC) of the skin is a tumor with greatly increased incidence among immunosuppressed patients; therefore, an infectious cause of SCC has long been sought. We performed a hospital-based case-control study of Staphylococcus aureus and biopsies of SCC (n = 82), basal cell carcinoma (n = 142), actinic keratosis (n = 57), and seborrhoeic keratosis (n = 72) in comparison with biopsies from healthy skin of these 353 immunocompetent patients. In a S. aureus-specific PCR, targeting the nuc gene, presence of S. aureus DNA was strongly associated with SCC (29.3% positive specimens; adjusted odds ratio, 6.23; 95% confidence interval, 3.10-12.53) compared with healthy skin (5.7% positive specimens). There was also a tendency for association of S. aureus with actinic keratosis, but no association was found for basal cell carcinoma or seborrhoeic keratosis. Analysis using cotton swab samples taken on top of the lesions and from healthy skin gave similar results (adjusted odds ratio for SCC compared with healthy skin, 2.67; 95% confidence interval, 1.47-4.83). In conclusion, there is a strong association between SCC and presence of S. aureus. The study design used cannot determine whether the association implies that presence of S. aureus might influence carcinogenesis or whether it may imply that SCC has an increased susceptibility to S. aureus colonization. (Cancer Epidemiol Biomarkers Prev 2009;18(2):OF1-7).
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| 6. |
- Habayeb, Mazen S, et al.
(författare)
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Nora virus persistent infections are not affected by the RNAi machinery.
- 2009
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 4:5, s. e5731-
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Tidskriftsartikel (refereegranskat)abstract
- Drosophila melanogaster is widely used to decipher the innate immune system in response to various pathogens. The innate immune response towards persistent virus infections is among the least studied in this model system. We recently discovered a picorna-like virus, the Nora virus which gives rise to persistent and essentially symptom-free infections in Drosophila melanogaster. Here, we have used this virus to study the interaction with its host and with some of the known Drosophila antiviral immune pathways. First, we find a striking variability in the course of the infection, even between flies of the same inbred stock. Some flies are able to clear the Nora virus but not others. This phenomenon seems to be threshold-dependent; flies with a high-titer infection establish stable persistent infections, whereas flies with a lower level of infection are able to clear the virus. Surprisingly, we find that both the clearance of low-level Nora virus infections and the stability of persistent infections are unaffected by mutations in the RNAi pathways. Nora virus infections are also unaffected by mutations in the Toll and Jak-Stat pathways. In these respects, the Nora virus differs from other studied Drosophila RNA viruses.
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| 7. |
- Habayeb, Mazen, 1982-, et al.
(författare)
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The Drosophila Nora virus is an enteric virus, transmitted via feces
- 2009
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Ingår i: Journal of Invertebrate Pathology. - : Elsevier BV. - 0022-2011 .- 1096-0805. ; 101, s. 29-33
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Tidskriftsartikel (refereegranskat)abstract
- The biology of the Drosophila viruses has not been intensely investigated. Here we have investigated the biology of the Nora virus, a persistent Drosophila virus. We find that injected Nora virus is able to replicate in the flies, reaching a high titer that is maintained in the next generation. There is a remarkable variation in the viral loads of individual flies in persistently infected stocks; the titers can differ by three orders of magnitude. The Nora virus is mainly found in the intestine of infected flies, and the histology of these infected intestines show increased vacuolization. The virus is excreted in the feces and is horizontally transmitted. The Nora virus infection has a very mild effect on the longevity of the flies, and no significant effect on the number of eggs laid and the percent of eggs that develop to adults.
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| 8. |
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| 9. |
- Polacek, Charlotta, et al.
(författare)
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Cytolytic replication of coxsackievirus B2 in CAR-deficient rhabdomyosarcoma cells.
- 2005
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Ingår i: Virus Research. - : Elsevier BV. - 0168-1702 .- 1872-7492. ; 113:2, s. 107-15
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Tidskriftsartikel (refereegranskat)abstract
- The six coxsackievirus B serotypes (CVB1-6) use the coxsackie- and adenovirus receptor (CAR) for host cell entry. Four of these serotypes, CVB1, 3, 5 and 6, have also shown the capacity to replicate and cause cytolysis in rhabdomyosarcoma (RD) cells, a CAR-deficient cell line. This extended tropism has been associated with an acquired ability to bind decay accelerating factor (DAF). In this study, we have adapted the CVB2 prototype strain Ohio-1 (CVB2/O) to replicate in RD cells. Two types of infection were identified: (I) an enterovirus-typical, lytic infection, and (II) a non-lytic infection. Both CVB2/O-RD variants retained the prototype-ability to cause cytopathic effect in HeLa cells using CAR as receptor. Phenotypic and genotypic changes in the CVB2/O-RD-variants were determined and compared to the prototype cultured in HeLa cells. Inhibition studies using antibodies against CAR and DAF revealed a maintained ability of the CVB2/O-RD-variants to bind CAR, but no binding to DAF was observed. In addition, neither the prototype nor the CVB2/O-RD-variants were able to cause hemagglutination in human red blood cells, an enterovirus feature associated with affinity for DAF. Sequence analysis of the CVB2/O-RD-variants showed acquired mutations in the capsid region, suggesting extended receptor usage towards an alternative, yet unidentified, receptor for CVB2.
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| 10. |
- Tolf, Conny, et al.
(författare)
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Identification of Ljungan virus VP0 and VP1 amino acid residues associated with cytolytic replication in cultured cells
- 2009
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Ingår i: Archives of Virology. - : Springer Science and Business Media LLC. - 0304-8608 .- 1432-8798. ; 154:8, s. 1271-1284
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Tidskriftsartikel (refereegranskat)abstract
- Ljungan virus is a picornavirus isolated from Swedish and North American rodents. Replication of Ljungan virus in cultured cells normally induces a weak and delayed cytopathic effect compared to that of many other picornaviruses. However, efficiently replicating Ljungan virus variants may evolve during serial passages in cell culture. In this study, we evaluate the significance of three substitutions in capsid protein VP0 and VP1 of a cell-culture-adapted variant of the Swedish Ljungan virus 145SL strain. In contrast to the parental strain, this 145SLG variant grows to high titers in green monkey kidney cells and induces a distinct cytopathic effect. Reverse genetic analyses demonstrated that each one of the individual capsid substitutions contributes to lytic replication in cell culture, but also that expression of all three substitutions results in a 100- to 500-fold increase in viral titers compared to viruses encoding single capsid substitutions. In addition, as indicated by detection of activated caspase-3 and DNA fragmentation, there seems to be an association between increased replication efficiency of lytic Ljungan virus variants and induction of an apoptotic response in infected green monkey kidney cells.
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