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author:("koehne, Ana")
1.  Immune Memory to Sudan Virus: Comparison between Two Separate Disease Outbreaks 
Viruses  2015;7(1):37-51.
Recovery from ebolavirus infection in humans is associated with the development of both cell-mediated and humoral immune responses. According to recent studies, individuals that did not survive infection with ebolaviruses appear to have lacked a robust adaptive immune response and the expression of several early innate response markers. However, a comprehensive protective immune profile has yet to be described. Here, we examine cellular memory immune responses among survivors of two separate Ebolavirus outbreaks (EVDs) due to Sudan virus (SUDV) infection in Uganda—Gulu 2000–2001 and Kibaale 2012. Freshly collected blood samples were stimulated with inactivated SUDV, as well as with recombinant SUDV or Ebola virus (EBOV) GP (GP1–649). In addition, ELISA and plaque reduction neutralization assays were performed to determine anti-SUDV IgG titers and neutralization capacity. Cytokine expression was measured in whole blood cultures in response to SUDV and SUDV GP stimulation in both survivor pools, demonstrating recall responses that indicate immune memory. Cytokine responses between groups were similar but had distinct differences. Neutralizing, SUDV-specific IgG activity against irradiated SUDV and SUDV recombinant proteins were detected in both survivor cohorts. Furthermore, humoral and cell-mediated crossreactivity to EBOV and EBOV recombinant GP1–649 was observed in both cohorts. In conclusion, immune responses in both groups of survivors demonstrate persistent recognition of relevant antigens, albeit larger cohorts are required in order to reach greater statistical significance. The differing cytokine responses between Gulu and Kibaale outbreak survivors suggests that each outbreak may not yield identical memory responses and promotes the merits of studying the immune responses among outbreaks of the same virus. Finally, our demonstration of cross-reactive immune recognition suggests that there is potential for developing cross-protective vaccines for ebolaviruses.
doi:10.3390/v7010037
PMCID: PMC4306827  PMID: 25569078
ebolavirus; human survivors; memory immunity; cross-reactivity
2.  Lassa virus entry requires a trigger-induced receptor switch 
Science (New York, N.Y.)  2014;344(6191):1506-1510.
Lassa virus spreads from rodents to humans and can lead to lethal hemorrhagic fever. Despite its broad tropism, chicken cells were reported to resist infection thirty years ago. We show that Lassa virus readily engaged its cell surface receptor α-dystroglycan in avian cells, but virus entry in susceptible species involved a pH-dependent switch to an intracellular receptor, the lysosome-resident protein LAMP1. Iterative haploid screens revealed that the sialyltransferase ST3GAL4 was required for the interaction of the virus glycoprotein with LAMP1. A single glycosylated residue in LAMP1, present in susceptible species but absent in birds, was essential for interaction with the Lassa virus envelope protein and subsequent infection. The resistance of Lamp1-deficient mice to Lassa virus highlights the relevance of this receptor switch in vivo.
doi:10.1126/science.1252480
PMCID: PMC4239993  PMID: 24970085
3.  Venezuelan Equine Encephalitis Virus Replicon Particle Vaccine Protects Nonhuman Primates from Intramuscular and Aerosol Challenge with Ebolavirus 
Journal of Virology  2013;87(9):4952-4964.
There are no vaccines or therapeutics currently approved for the prevention or treatment of ebolavirus infection. Previously, a replicon vaccine based on Venezuelan equine encephalitis virus (VEEV) demonstrated protective efficacy against Marburg virus in nonhuman primates. Here, we report the protective efficacy of Sudan virus (SUDV)- and Ebola virus (EBOV)-specific VEEV replicon particle (VRP) vaccines in nonhuman primates. VRP vaccines were developed to express the glycoprotein (GP) of either SUDV or EBOV. A single intramuscular vaccination of cynomolgus macaques with VRP expressing SUDV GP provided complete protection against intramuscular challenge with SUDV. Vaccination against SUDV and subsequent survival of SUDV challenge did not fully protect cynomolgus macaques against intramuscular EBOV back-challenge. However, a single simultaneous intramuscular vaccination with VRP expressing SUDV GP combined with VRP expressing EBOV GP did provide complete protection against intramuscular challenge with either SUDV or EBOV in cynomolgus macaques. Finally, intramuscular vaccination with VRP expressing SUDV GP completely protected cynomolgus macaques when challenged with aerosolized SUDV, although complete protection against aerosol challenge required two vaccinations with this vaccine.
doi:10.1128/JVI.03361-12
PMCID: PMC3624300  PMID: 23408633
4.  Standardization of the Filovirus Plaque Assay for Use in Preclinical Studies 
Viruses  2012;4(12):3511-3530.
The filovirus plaque assay serves as the assay of choice to measure infectious virus in a cell culture, blood, or homogenized tissue sample. It has been in use for more than 30 years and is the generally accepted assay used to titrate virus in samples from animals treated with a potential antiviral therapeutic or vaccine. As these animal studies are required for the development of vaccines and therapeutics under the FDA Animal Rule, it is essential to have a standardized assay to compare their efficacies against the various filoviruses. Here, we present an evaluation of the conditions under which the filovirus plaque assay performs best for the Ebola virus Kikwit variant and the Angola variant of Marburg virus. The indicator cell type and source, inoculum volumes, length of incubation and general features of filovirus biology as visualized in the assay are addressed in terms of the impact on the sample viral titer calculations. These optimization studies have resulted in a plaque assay protocol which can be used for preclinical studies, and as a standardized protocol for use across institutions, to aid in data comparison. This protocol will be validated for use in GLP studies supporting advanced development of filovirus therapeutics and vaccines.
doi:10.3390/v4123511
PMCID: PMC3528277  PMID: 23223188
plaque assay; filovirus; Ebola; ebolavirus; marburgvirus; Marburg virus; Vero
5.  Structure of an Antibody in Complex with Its Mucin Domain Linear Epitope That Is Protective against Ebola Virus 
Journal of Virology  2012;86(5):2809-2816.
Antibody 14G7 is protective against lethal Ebola virus challenge and recognizes a distinct linear epitope in the prominent mucin-like domain of the Ebola virus glycoprotein GP. The structure of 14G7 in complex with its linear peptide epitope has now been determined to 2.8 Å. The structure shows that this GP sequence forms a tandem β-hairpin structure that binds deeply into a cleft in the antibody-combining site. A key threonine at the apex of one turn is critical for antibody interaction and is conserved among all Ebola viruses. This work provides further insight into the mechanism of protection by antibodies that target the protruding, highly accessible mucin-like domain of Ebola virus and the structural framework for understanding and characterizing candidate immunotherapeutics.
doi:10.1128/JVI.05549-11
PMCID: PMC3302272  PMID: 22171276
6.  A Shared Structural Solution for Neutralizing Ebolaviruses 
Nature structural & molecular biology  2011;18(12):1424-1427.
Sudan virus (genus ebolavirus) is lethal, yet no monoclonal antibody is known to neutralize it. Here we describe antibody 16F6 that neutralizes Sudan virus and present its structure bound to the trimeric viral glycoprotein. Unexpectedly, the 16F6 epitope overlaps that of KZ52, the only other antibody against the GP1,2 core to be visualized. Further, both antibodies against this key GP1–GP2-bridging epitope neutralize at a post-internalization step, likely fusion.
doi:10.1038/nsmb.2150
PMCID: PMC3230659  PMID: 22101933
8.  Complex of a protective antibody with its Ebola virus GP peptide epitope: unusual features of a Vλx-light chain 
Journal of molecular biology  2007;375(1):202-216.
13F6-1-2 is a murine monoclonal antibody that recognizes the heavily glycosylated mucin-like domain of the Ebola virus virion-attached glycoprotein (GP) and protects animals against lethal viral challenge. Here we present the crystal structure, at 2.0 Å, of 13F6-1-2 in complex with its Ebola virus GP peptide epitope. The GP peptide binds in an extended conformation, anchored primarily by interactions to the heavy chain. Two GP residues, Gln P406 and Arg P409, make extensive side chain hydrogen bond and electrostatic interactions to the antibody and are likely critical for recognition and affinity. The 13F6-1-2 antibody utilizes a rare Vλx light chain. The three light chain complementarity determining regions (CDRs) do not adopt canonical conformations and represent new classes of structures distinct from Vκ and other Vλ light chains. In addition, although Vλx had been thought to confer specificity, all light chain contacts are mediated through germline-encoded residues. This structure of an antibody that protects against the Ebola virus now provides a framework for humanization and development of a post-exposure immunotherapeutic.
doi:10.1016/j.jmb.2007.10.017
PMCID: PMC2173910  PMID: 18005986
Ebola virus; Vλx light chain; glycoprotein; neutralizing antibody; new canonical structures of immunoglobulins; hypervariable loops; complementarity determining region; Fab-peptide complex
9.  Protective Cytotoxic T-Cell Responses Induced by Venezuelan Equine Encephalitis Virus Replicons Expressing Ebola Virus Proteins 
Journal of Virology  2005;79(22):14189-14196.
Infection with Ebola virus causes a severe disease accompanied by high mortality rates, and there are no licensed vaccines or therapies available for human use. Filovirus vaccine research efforts still need to determine the roles of humoral and cell-mediated immune responses in protection from Ebola virus infection. Previous studies indicated that exposure to Ebola virus proteins expressed from packaged Venezuelan equine encephalitis virus replicons elicited protective immunity in mice and that antibody-mediated protection could only be demonstrated after vaccination against the glycoprotein. In this study, the murine CD8+ T-cell responses to six Ebola virus proteins were examined. CD8+ T cells specific for Ebola virus glycoprotein, nucleoprotein, and viral proteins (VP24, VP30, VP35, and VP40) were identified by intracellular cytokine assays using splenocytes from vaccinated mice. The cells were expanded by restimulation with peptides and demonstrated cytolytic activity. Adoptive transfer of the CD8+ cytotoxic T cells protected filovirus naïve mice from challenge with Ebola virus. These data support a role for CD8+ cytotoxic T cells as part of a protective mechanism induced by vaccination against six Ebola virus proteins and provide additional evidence that cytotoxic T-cell responses can contribute to protection from filovirus infections.
doi:10.1128/JVI.79.22.14189-14196.2005
PMCID: PMC1280180  PMID: 16254354

Results 1-9 (9)