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    ABSTRACT: Accumulating evidence suggests that natural killer (NK) cells may have an important role in HIV-1 disease pathogenesis; however, in vivo studies are lacking. Feline immunodeficiency virus (FIV) infection of cats provides a valuable model to study NK cell function in vivo. The immune response against Listeria monocytogenes (Lm) is well characterized, allowing its use as an innate immune probe. We have previously shown that locally delivered IL-15 can improve Lm clearance in FIV-infected animals, and this correlated with an increase in NK cell number. In the present study, chronically FIV-infected and SPF-control cats were challenged with Lm by unilateral subcutaneous injection next to the footpad and then treated with 5-bromo-2'-deoxyuridine (BrdU). The Lm draining and contralateral control lymph nodes were evaluated for NK, NKT, CD4+ and CD8+ T cell number, proliferation, apoptosis, and NK cell function. Listeria monocytogenes burden was also assessed in both control and Lm draining lymph nodes. NK, NKT, CD4+ T and CD8+ T cells in the Lm-challenged lymph node of FIV-infected cats did not increase in number. In addition, after Lm challenge, NK cells from FIV-infected cats did not increase their proliferation rate, apoptosis was elevated, and perforin expression was not upregulated when compared to SPF-control cats. The failure of the NK cell response against Lm challenge in the draining lymph node of FIV-infected cats correlates with the delayed control and clearance of this opportunistic bacterial pathogen.
    PLoS ONE 05/2012; 7(5):e37606. DOI:10.1371/journal.pone.0037606 · 3.53 Impact Factor
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    ABSTRACT: Feline immunodeficiency virus (FIV) is a lentivirus that causes AIDS in domestic cats, similar to HIV/AIDS in humans. FIV accessory protein Vif abrogates inhibition of infection by cat APOBEC3 restriction factors. FIV also encodes a multifunctional OrfA accessory protein, which has characteristics similar to HIV Tat, Vpu, Vpr, and Nef. To examine the role of vif and orfA accessory genes in FIV replication and pathogenicity, we generated chimeras between two FIV molecular clones with divergent disease potential: a highly pathogenic isolate that replicates rapidly in vitro and is associated with significant immunopathology in vivo, (FIV-C36, referred to as high virulence, or HV-FIV); and a less pathogenic strain (FIV-PPR, referred to as low virulence, or LV-FIV). Using PCR-driven overlap extension, we produced viruses in which vif, orfA or both genes from virulent HV-FIV replaced equivalent genes in LV-FIV. Generation of these chimeras is more straightforward in FIV than in primate lentiviruses, since FIV accessory gene open reading frames have very little overlap with other genes. All three chimeric viruses exhibited increased replication kinetics in vitro compared to LV-FIV. Chimeras containing HV-Vif or Vif/OrfA had replication rates equivalent to virulent HV-FIV parental virus. Furthermore, siRNA knockdown of feline APOBEC3 genes resulted in equalization of replication rates between LV-FIV and LV-FIV encoding HV-FIV Vif. These findings demonstrate that Vif-APOBEC interactions play a key role in controlling replication and pathogenicity of this immunodeficiency-inducing virus in its native host species, and that accessory genes act as mediators of lentiviral strain-specific virulence.
    Journal of Virology 05/2013; DOI:10.1128/JVI.00752-13 · 4.65 Impact Factor
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    ABSTRACT: C8, a short peptide characterized by three regularly spaced Trp residues, belongs to the membrane-proximal external functional domains of the feline immunodeficiency virus coat protein gp36. It elicits antiviral activity as a result of blocking cell entry and exhibits membranotropic and fusogenic activity. Membrane-proximal external functional domains of virus coat proteins are potential targets in the development of new anti HIV drugs that overcome the limitations of the current anti-retroviral therapy. In the present work, we studied the conformation of C8 and its interaction with micellar surfaces using circular dichroism, nuclear magnetic resonance and fluorescence spectroscopy. The experimental data were integrated by molecular dynamics simulations in a micelle-water system. Our data provide insight into the environmental conditions related to the presence of the fusogenic peptide C8 on zwitterionic or negatively charged membranes. The membrane charge modulates the conformational features of C8. A zwitterionic membrane surface induces C8 to assume canonical secondary structures, with hydrophobic interactions between the Trp residues and the phospholipid chains of the micelles. A negatively charged membrane surface favors disordered C8 conformations and unspecific superficial interactions, resulting in membrane destabilization.
    Biochimica et Biophysica Acta 12/2013; 1838(3). DOI:10.1016/j.bbamem.2013.12.010 · 4.66 Impact Factor