Protective Role of Cytotoxic T Lymphocytes in Filovirus Hemorrhagic Fever

Infection with many emerging viruses, such as the hemorrhagic fever disease caused by the filoviruses, Marburg (MARV), and Ebola virus (EBOV), leaves the host with a short timeframe in which to mouse a protective immune response. In lethal cases, uncontrolled viral replication and virus-induced immune dysregulation are too severe to overcome, and mortality is generally associated with a lack of notable immune responses. Vaccination studies in animals have demonstrated an association of IgG and neutralizing antibody responses against the protective glycoprotein antigen with survival from lethal challenge. More recently, studies in animal models of filovirus hemorrhagic fever have established that induction of a strong filovirus-specific cytotoxic T lymphocyte (CTL) response can facilitate complete viral clearance. In this review, we describe assays used to discover CTL responses after vaccination or live filovirus infection in both animal models and human clinical trials. Unfortunately, little data regarding CTL responses have been collected from infected human survivors, primarily due to the low frequency of disease and the inability to perform these studies in the field. Advancements in assays and technologies may allow these studies to occur during future outbreaks

Discovery of common marburgvirus protective epitopes in a BALB/c mouse model

<p>Abstract</p> <p>Background</p> <p>Marburg virus (MARV) causes acute hemorrhagic fever that is often lethal, and no licensed vaccines are available for preventing this deadly viral infection. The immune mechanisms for protection against MARV are poorly understood, but previous studies suggest that both antibodies and T cells are required. In our study, we infected BALB/c mice with plaque-purified, nonlethal MARV and used overlapping peptides to map H2^<it>d</it>-restricted CD8+ T-cell epitopes.</p> <p>Methods</p> <p>Splenocytes from mice infected with nonlethal MARV were harvested and stimulated with multiple overlapping 15-mer peptide pools, and reactive CD8+ T cells were evaluated for antigen specificity by measuring upregulation of CD44 and interferon-γ expression. After confirming positive reactivity to specific 15-mer peptides, we used extrapolated 9-mer epitopes to evaluate the induction of cytotoxic T-cell responses and protection from lethal MARV challenge in BALB/c mice.</p> <p>Results</p> <p>We discovered a CD8+ T-cell epitope within both the MARV glycoprotein (GP) and nucleoprotein (NP) that triggered cytotoxic T-cell responses. These responses were also protective when epitope-specific splenocytes were transferred into naïve animals.</p> <p>Conclusion</p> <p>Epitope mapping of MARV GP, NP, and VP40 provides the first evidence that specific MARV-epitope induction of cellular immune responses is sufficient to combat infection. Establishment of CD8+ T-cell epitopes that are reactive to MARV proteins provides an important research tool for dissecting the significance of cellular immune responses in BALB/c mice infected with MARV.</p

Development of a model for marburgvirus based on severe-combined immunodeficiency mice

The filoviruses, Ebola (EBOV) and Marburg (MARV), cause a lethal hemorrhagic fever. Human isolates of MARV are not lethal to immmunocompetent adult mice and, to date, there are no reports of a mouse-adapted MARV model. Previously, a uniformly lethal EBOV-Zaire mouse-adapted virus was developed by performing 9 sequential passages in progressively older mice (suckling to adult). Evaluation of this model identified many similarities between infection in mice and nonhuman primates, including viral tropism for antigen-presenting cells, high viral titers in the spleen and liver, and an equivalent mean time to death. Existence of the EBOV mouse model has increased our understanding of host responses to filovirus infections and likely has accelerated the development of countermeasures, as it is one of the only hemorrhagic fever viruses that has multiple candidate vaccines and therapeutics. Here, we demonstrate that serially passaging liver homogenates from MARV-infected severe combined immunodeficient (scid) mice was highly successful in reducing the time to death in scid mice from 50–70 days to 7–10 days after MARV-Ci67, -Musoke, or -Ravn challenge. We performed serial sampling studies to characterize the pathology of these scid mouse-adapted MARV strains. These scid mouse-adapted MARV models appear to have many similar properties as the MARV models previously developed in guinea pigs and nonhuman primates. Also, as shown here, the scid-adapted MARV mouse models can be used to evaluate the efficacy of candidate antiviral therapeutic molecules, such as phosphorodiamidate morpholino oligomers or antibodies

Role of Natural Killer Cells in Innate Protection against Lethal Ebola Virus Infection

Ebola virus is a highly lethal human pathogen and is rapidly driving many wild primate populations toward extinction. Several lines of evidence suggest that innate, nonspecific host factors are potentially critical for survival after Ebola virus infection. Here, we show that nonreplicating Ebola virus-like particles (VLPs), containing the glycoprotein (GP) and matrix protein virus protein (VP)40, administered 1–3 d before Ebola virus infection rapidly induced protective immunity. VLP injection enhanced the numbers of natural killer (NK) cells in lymphoid tissues. In contrast to live Ebola virus, VLP treatment of NK cells enhanced cytokine secretion and cytolytic activity against NK-sensitive targets. Unlike wild-type mice, treatment of NK-deficient or -depleted mice with VLPs had no protective effect against Ebola virus infection and NK cells treated with VLPs protected against Ebola virus infection when adoptively transferred to naive mice. The mechanism of NK cell–mediated protection clearly depended on perforin, but not interferon-γ secretion. Particles containing only VP40 were sufficient to induce NK cell responses and provide protection from infection in the absence of the viral GP. These findings revealed a decisive role for NK cells during lethal Ebola virus infection. This work should open new doors for better understanding of Ebola virus pathogenesis and direct the development of immunotherapeutics, which target the innate immune system, for treatment of Ebola virus infection

Managing Potential Laboratory Exposure to Ebola Virus by Using a Patient Biocontainment Care Unit1

One-sentence summary for table of contents: Recommendations are needed for management of potential laboratory exposure to a Biosafety Level 4 pathogen

Induced IL-10 Splice Altering Approach to Antiviral Drug Discovery

Ebola virus causes an acute hemorrhagic fever lethal in primates and rodents. The contribution of host immune factors to pathogenesis has yet to be determined and may reveal efficacious targets for potential treatment. In this study, we show that the interleukin (IL)-10 signaling pathway modulates Ebola pathogenesis. IL-10 [superscript - / -] mice and wild-type mice receiving antisense targeting IL-10 signaling via disrupting expression through aberrant splice altering were resistant to ebola virus infection. IL-10 [superscript - / -] mice exhibited reduced viral titers, pathology, and levels of IL-2, IL-6, keratinocyte-derived chemokine (KC), and macrophage inflammatory protein-1 α and increased interferon (IFN)-γ relative to infected wild-type mice. Furthermore, antibody depletion studies in IL-10 [superscript - / -] mice suggest a requirement for natural killer cells and IFN-γ for protection. Together, these data demonstrate that resistance to ebola infection is regulated by IL-10 and can be targeted in a prophylactic manner to protect against lethal hemorrhagic virus challenge

Constitutivism

A brief explanation and overview of constitutivism

The twilight of the Liberal Social Contract? On the Reception of Rawlsian Political Liberalism

This chapter discusses the Rawlsian project of public reason, or public justification-based 'political' liberalism, and its reception. After a brief philosophical rather than philological reconstruction of the project, the chapter revolves around a distinction between idealist and realist responses to it. Focusing on political liberalism’s critical reception illuminates an overarching question: was Rawls’s revival of a contractualist approach to liberal legitimacy a fruitful move for liberalism and/or the social contract tradition? The last section contains a largely negative answer to that question. Nonetheless the chapter's conclusion shows that the research programme of political liberalism provided and continues to provide illuminating insights into the limitations of liberal contractualism, especially under conditions of persistent and radical diversity. The programme is, however, less receptive to challenges to do with the relative decline of the power of modern states

Novel Structurally Designed Vaccine for S. aureus α-Hemolysin: Protection against Bacteremia and Pneumonia

Staphylococcus aureus (S. aureus) is a human pathogen associated with skin and soft tissue infections (SSTI) and life threatening sepsis and pneumonia. Efforts to develop effective vaccines against S. aureus have been largely unsuccessful, in part due to the variety of virulence factors produced by this organism. S. aureus alpha-hemolysin (Hla) is a pore-forming toxin expressed by most S. aureus strains and reported to play a key role in the pathogenesis of SSTI and pneumonia. Here we report a novel recombinant subunit vaccine candidate for Hla, rationally designed based on the heptameric crystal structure. This vaccine candidate, denoted AT-62aa, was tested in pneumonia and bacteremia infection models using S. aureus strain Newman and the pandemic strain USA300 (LAC). Significant protection from lethal bacteremia/sepsis and pneumonia was observed upon vaccination with AT-62aa along with a Glucopyranosyl Lipid Adjuvant-Stable Emulsion (GLA-SE) that is currently in clinical trials. Passive transfer of rabbit immunoglobulin against AT-62aa (AT62-IgG) protected mice against intraperitoneal and intranasal challenge with USA300 and produced significant reduction in bacterial burden in blood, spleen, kidney, and lungs. Our Hla-based vaccine is the first to be reported to reduce bacterial dissemination and to provide protection in a sepsis model of S. aureus infection. AT62-IgG and sera from vaccinated mice effectively neutralized the toxin in vitro and AT62-IgG inhibited the formation of Hla heptamers, suggesting antibody-mediated neutralization as the primary mechanism of action. This remarkable efficacy makes this Hla-based vaccine a prime candidate for inclusion in future multivalent S. aureus vaccine. Furthermore, identification of protective epitopes within AT-62aa could lead to novel immunotherapy for S. aureus infection