Alterations in intracellular potassium concentration by HIV-1 and SIV Nef

<p>Abstract</p> <p>Background</p> <p>HIV-1 mediated perturbation of the plasma membrane can produce an alteration in the transmembrane gradients of cations and other small molecules leading to cell death. Several HIV-1 proteins have been shown to perturb membrane permeability and ion transport. <it>Xenopus laevis </it>oocytes have few functional endogenous ion channels, and have proven useful as a system to examine direct effects of exogenously added proteins on ion transport.</p> <p>Results</p> <p>HIV-1 Nef induces alterations in the intracellular potassium concentration in CD4+ T-lymphoblastoid cells, but not intracellular pH. Two electrode voltage-clamp recording was used to determine that Nef did not form ion channel-like pores in <it>Xenopus </it>oocytes.</p> <p>Conclusion</p> <p>These results suggest that HIV-1 Nef regulates intracellular ion concentrations indirectly, and may interact with membrane proteins such as ion channels to modify their electrical properties.</p

Down-regulation of cell surface CXCR4 by HIV-1

<p>Abstract</p> <p>Background</p> <p>CXC chemokine receptor 4 (CXCR4), a member of the G-protein-coupled chemokine receptor family, can serve as a co-receptor along with CD4 for entry into the cell of T-cell tropic X4 human immunodeficiency virus type 1 (HIV-1) strains. Productive infection of T-lymphoblastoid cells by X4 HIV-1 markedly reduces cell-surface expression of CD4, but whether or not the co-receptor CXCR4 is down-regulated has not been conclusively determined.</p> <p>Results</p> <p>Infection of human T-lymphoblastoid cell line RH9 with HIV-1 resulted in down-regulation of cell surface CXCR4 expression. Down-regulation of surface CXCR4 correlated temporally with the increase in HIV-1 protein expression. CXCR4 was concentrated in intracellular compartments in H9 cells after HIV-1 infection. Immunofluorescence microscopy studies showed that CXCR4 and HIV-1 glycoproteins were co-localized in HIV infected cells. Inducible expression of HIV-1 envelope glycoproteins also resulted in down-regulation of CXCR4 from the cell surface.</p> <p>Conclusion</p> <p>These results indicated that cell surface CXCR4 was reduced in HIV-1 infected cells, whereas expression of another membrane antigen, CD3, was unaffected. CXCR4 down-regulation may be due to intracellular sequestering of HIV glycoprotein/CXCR4 complexes.</p

Lassa Fever in Post-Conflict Sierra Leone

Background: Lassa fever (LF), an often-fatal hemorrhagic disease caused by Lassa virus (LASV), is a major public health threat in West Africa. When the violent civil conflict in Sierra Leone (1991 to 2002) ended, an international consortium assisted in restoration of the LF program at Kenema Government Hospital (KGH) in an area with the world's highest incidence of the disease. Methodology/Principal Findings Clinical and laboratory records of patients presenting to the KGH Lassa Ward in the post-conflict period were organized electronically. Recombinant antigen-based LF immunoassays were used to assess LASV antigenemia and LASV-specific antibodies in patients who met criteria for suspected LF. KGH has been reestablished as a center for LF treatment and research, with over 500 suspected cases now presenting yearly. Higher case fatality rates (CFRs) in LF patients were observed compared to studies conducted prior to the civil conflict. Different criteria for defining LF stages and differences in sensitivity of assays likely account for these differences. The highest incidence of LF in Sierra Leone was observed during the dry season. LF cases were observed in ten of Sierra Leone's thirteen districts, with numerous cases from outside the traditional endemic zone. Deaths in patients presenting with LASV antigenemia were skewed towards individuals less than 29 years of age. Women self-reporting as pregnant were significantly overrepresented among LASV antigenemic patients. The CFR of ribavirin-treated patients presenting early in acute infection was lower than in untreated subjects. Conclusions/Significance: Lassa fever remains a major public health threat in Sierra Leone. Outreach activities should expand because LF may be more widespread in Sierra Leone than previously recognized. Enhanced case finding to ensure rapid diagnosis and treatment is imperative to reduce mortality. Even with ribavirin treatment, there was a high rate of fatalities underscoring the need to develop more effective and/or supplemental treatments for LF

H9 cells were loaded with the fluorescent indicator PBFI-AM and incubated with 300 nM recombinant Nef protein or with control medium without Nef for 15 min at 37°C

Control cells (A and C) and cells incubated with Nef protein (B and D) were examined by light (A and B) and fluorescent (C and D) microscopy.<p><b>Copyright information:</b></p><p>Taken from "Alterations in intracellular potassium concentration by HIV-1 and SIV Nef"</p><p>http://www.virologyj.com/content/5/1/60</p><p>Virology Journal 2008;5():60-60.</p><p>Published online 19 May 2008</p><p>PMCID:PMC2396157.</p><p></p

Co-localization CXCR4 and HIV-1 glycoprotein in HIV-1 infected H9 cells

<p><b>Copyright information:</b></p><p>Taken from "Down-regulation of cell surface CXCR4 by HIV-1"</p><p>http://www.virologyj.com/content/5/1/6</p><p>Virology Journal 2008;5():6-6.</p><p>Published online 11 Jan 2008</p><p>PMCID:PMC2248172.</p><p></p> Four days after HIV-1 infection, cells were fixed and permeabilized with saponin. Cells were then labeled with a human monoclonal antibody that interact with SU and then rhodamine-conjugated goat anti-human antibodies (Panel C: red fluorescence) and with 12G5 mAb followed by fluorescein-conjugated goat anti-mouse antibodies (Panel D:green fluorescence). Panel A: phase contrast image. Panel B represents a superposition of green and red fluorescence, with costained regions appearing in yellow. Yellow regions in panel B indicate the colocalization of chemokine receptor CXCR4 and HIV-1 proteins

(A) 300 nM recombinant Nef, (B) control oocyte Panel C: current:voltage plots determined from data recorded in panel A and B

<p><b>Copyright information:</b></p><p>Taken from "Alterations in intracellular potassium concentration by HIV-1 and SIV Nef"</p><p>http://www.virologyj.com/content/5/1/60</p><p>Virology Journal 2008;5():60-60.</p><p>Published online 19 May 2008</p><p>PMCID:PMC2396157.</p><p></p

Flow cytometry analysis demonstrating reduced CXCR4 expression in HIV-1 infected RH9 cells

<p><b>Copyright information:</b></p><p>Taken from "Down-regulation of cell surface CXCR4 by HIV-1"</p><p>http://www.virologyj.com/content/5/1/6</p><p>Virology Journal 2008;5():6-6.</p><p>Published online 11 Jan 2008</p><p>PMCID:PMC2248172.</p><p></p> Panel A: RH9 T-lymphoblastoid cells infected with HIV-1. On days 1, 4, and 7 postinfection cells were fixed with 4% paraformaldehyde, stained with mouse MAb 12G5 anti-CXCR4 (10 μg/ml) or isotype-matched control antibody followed by fluorescein isothiocyanate (FITC)-conjugated goat anti-mouse immunoglobulin G, and analyzed by flow cytometry. Median fluorescence intensity was calculated as an indicator of the level of cell surface CXCR4 expression. Data are presented as single-color histograms with FITC fluorescence (CD3 expression) along the horizontal axis and relative cell number along the vertical axis. RH9 cells (control cells), heavy solid line: H9 cells infected with HIV, dotted line; H9 with an isotype-matched control antibody, thin solid line. Panel B: Analysis of surface CD3 expression in HIV-1 and mock infected RH9 cells by FACS analyzed on day 7 post-infection

Immunofluorescence microscopy analysis of CXCR4 expression in permeabilized HIV-1 and mock infected RH9 cells

<p><b>Copyright information:</b></p><p>Taken from "Down-regulation of cell surface CXCR4 by HIV-1"</p><p>http://www.virologyj.com/content/5/1/6</p><p>Virology Journal 2008;5():6-6.</p><p>Published online 11 Jan 2008</p><p>PMCID:PMC2248172.</p><p></p> Four days after HIV-1 infection, cells were fixed, permeabilized with saponin and labeled with a mouse monoclonal antibody to CXCR4 (12G5) and a secondary, FITC-conjugated anti-mouse antibodies for observation with a fluorescence microscopy. Panel A: Immunofluorescence staining control with isotype-matched monoclonal antibody. Panel C: CXCR4 immunofluorescence staining of H9 cells. Panels E and G, CXCR4 immunofluorescence staining of HIV-1 infected H9 cells. Panels B, D, F and H show phase contrast images of the same fields of cells shown in left panels

Monthly distribution of suspected LF cases presenting to the KGH Lassa Ward by serostatus, 2008–2012.

<p>Panel A: antigenemic Lassa fever cases (Ag+/IgM±). Panel B: Patients with serum anti-LASV IgM (Ag−/IgM+). Panel C: Patients with no Lassa virus seropositivity (Ag−/IgM−). The monthly frequency distributions differed between each of the serostatus group comparisons as assessed using a Poisson regression model (p<.001 for all serostatus comparisons; data not shown).</p