V Andrésdottir

University of Iceland, Reikiavik, Capital Region, Iceland

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Publications (4)10.75 Total impact

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    ABSTRACT: RNA transcripts of the B7 family molecule (CD80) are diminished in blood leukocytes from animals clinically affected with Visna/Maedi virus (VMV) infection. This work investigates whether the use of B7 genes enhances immune responses and protection in immunization-challenge approaches. Sheep were primed by particle-mediated epidermal bombardment with VMV gag and env gene recombinant plasmids together with plasmids encoding both CD80 and CD86 or CD80 alone, boosted with gag and env gene recombinant modified vaccinia Ankara virus and challenged intratracheally with VMV. Immunization in the presence of one or both of the B7 genes resulted in CD4+ T cell activation and antibody production (before and after challenge, respectively), but only immunization with CD80 and CD86 genes together, and not CD80 alone, resulted in a reduced number of infected animals and increased early transient cytotoxic T lymphocytes (CTL) responses. Post-mortem analysis showed an immune activation of lymphoid tissue in challenge-target organs in those animals that had received B7 genes compared to unvaccinated animals. Thus, the inclusion of B7 genes helped to enhance early cellular responses and protection (diminished proportion of infected animals) against VMV infection.
    Vaccine 07/2009; 27(34):4591-600. · 3.77 Impact Factor
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    ABSTRACT: To determine whether systemic immunization with plasmid DNA and virus vector against visna/maedi virus (VMV) would induce protective immune responses, sheep were immunized with VMV gag and/or env sequences using particle-mediated epidermal bombardment and injection of recombinant modified vaccinia Ankara. The results showed that immunization induced both humoral and cell-mediated responses prior to and after virus challenge. The vaccination protocol did not prevent infection, but immunization with the gag gene or a combination of gag and env genes resulted in significantly reduced provirus loads in blood and mediastinal lymph node, respectively. Provirus loads in lung and draining lymph node were unaffected, but p25 expression was undetectable in lungs of animals immunized with a combination of gag and env genes. Analysis of target tissues for lesions at post-mortem showed that immunization with the env gene caused a significant increase in lesion score, while the gag gene or a combination of gag and env genes had no effect. Inclusion of the ovine interferon-gamma gene in the initial priming mixture had minimal effect on immune responses, provirus load, or lesion development, although it resulted in a decreased p25 expression in the lung. The results thus show that systemic immunization with gag or a combination of gag and env genes reduces provirus load in blood and lymphoid tissue, respectively whereas env immunization has no effect on provirus load but increased lesion development.
    Vaccine 12/2008; 27(2):260-9. · 3.49 Impact Factor
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    ABSTRACT: Sheep were immunized against Visna/Maedi virus (VMV) gag and/or env genes via the nasopharynx-associated lymphoid tissue (NALT) and lung using polyethylenimine (PEI)-DNA complexes and modified vaccinia Ankara, and challenged with live virus via the lung. env immunization enhanced humoral responses prior to but not after VMV challenge. Systemic T cell proliferative and cytotoxic responses were generally low, with the responses following single gag gene immunization being significantly depressed after challenge. A transient reduction in provirus load in the blood early after challenge was observed following env immunization, whilst the gag gene either alone or in combination with env resulted in significantly elevated provirus loads in lung. However, despite this, a significant reduction in lesion score was observed in animals immunized with the single gag gene at post-mortem. Inclusion of IFN-gamma in the immunization mixture in general had no significant effects. The results thus showed that protective effects against VMV-induced lesions can be induced following respiratory immunization with the single gag gene, though this was accompanied by an increased pulmonary provirus load.
    Vaccine 08/2008; 26(35):4494-505. · 3.49 Impact Factor
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    ABSTRACT: The behavior of two genetically different molecular clones of visna virus KV1772-kv72/67 and LV1-1KS1 was comparedin vivoandin vitro.On intracerebral inoculation, clone KV1772-kv72/67 induced a similar response in five sheep as has already been reported with neurovirulent derivates of visna virus. Virus was frequently isolated from blood, cerebrospinal fluid (CSF), and lymphoid organs and induced characteristic central nervous system (CNS) lesions. A strong humoral immune response was detected by ELISA, immunoblotting, and neutralization. Six sheep infected with clone LV1-1KS1 showed a completely different picture. No virus could be isolated from blood or CSF during 6 months of infection. At sacrifice all organs were virus-negative except the CNS of one sheep. None of the six sheep developed significant neutralizing antibodies and only low titer antibodies were detected by ELISA and immunoblotting. Minimal CNS lesions were present in one sheep. The molecular clones were also tested in sheep choroid plexus cells (SCP) and macrophages. In macrophages LV1-1KS1 replicated to a significantly lower titer but induced much more cell fusion than KV1772-kv72/67. The clones replicated equally well in SCP cells. Thus, these molecular clones of visna virus, which differ only by 1% in nucleotide sequence, showed a profound difference in replication and pathogenicity bothin vitroandin vivo.These results can be used to map viral genetic determinants important for host–lentivirus interactions.
    Virology. 01/1997; 229(2):370-380.