Ebola virus is a Filoviridae that causes hemorrhagic fever in humans and induces high morbidity and mortality rates. Filoviruses are classified as "Category A bioterrorism agents", and currently there are no licensed therapeutics or vaccines to treat and prevent infection. The Filovirus glycoprotein (GP) is sufficient to protect individuals against infection, and several vaccines based on GP are under development including recombinant adenovirus, parainfluenza virus, Venezuelan equine encephalitis virus, vesicular stomatitis virus (VSV) and virus-like particles. Here we describe the development of a GP Fc fusion protein as a vaccine candidate. We expressed the extracellular domain of the Zaire Ebola virus (ZEBOV) GP fused to the Fc fragment of human IgG1 (ZEBOVGP-Fc) in mammalian cells and showed that GP undergoes the complex furin cleavage and processing observed in the native membrane-bound GP. Mice immunized with ZEBOVGP-Fc developed T-cell immunity against ZEBOV GP and neutralizing antibodies against replication-competent VSV-G deleted recombinant VSV containing ZEBOV GP. The ZEBOVGPFc vaccinated mice were protected against challenge with a lethal dose of ZEBOV. These results show that vaccination with the ZEBOVGP-Fc fusion protein alone without the need of a viral vector or assembly into virus-like particles is sufficient to induce protective immunity against ZEBOV in mice. Our data suggested that Filovirus GP Fc fusion proteins could be developed as a simple, safe, efficacious, and cost effective vaccine against Filovirus infection for human use.

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Athymic nude mice carry neither conventional T cells nor NKT cells of thymic origin. However, NK1.1−TCRint cells are present in the liver and other immune organs of athymic mice, because these lymphocyte subsets are truly of extrathymic origin. In this study, we examined whether extrathymic T cells had the capability to protect mice from malarial infection. Although B6-nu/nu mice were more sensitive to malaria than control B6 mice, these athymic mice were able to survive malaria when a reduced number of parasitized erythrocytes (5 × 103 per mouse) were injected. At the fulminant stage, lymphocytosis occurred in the liver and the major expanding lymphocytes were NK1.1−TCRint cells (IL-2Rβ+TCRαβ+). Unconventional CD8+ NKT cells (Vα14−) also appeared. Similar to the case of B6 mice, autoantibodies (IgM type) against denatured DNA appeared during malarial infection. Immune lymphocytes isolated from the liver of athymic mice which had recovered from malaria were capable of protecting irradiated euthymic and athymic mice from malaria when cell transfer experiments were conducted. In conjunction with the previous results in euthymic mice, the present results in athymic mice suggest that the major lymphocyte subsets associated with protection against malaria might be extrathymic T cells.

Natural killer T (NKT) cells and CD5+B cells were searched for in various immune organs of autoimmune prone (NZB×NZW)F1 (NZB/W F1) mice. The number of lymphocytes increased in the liver, spleen, and peritoneal cavity after the onset of disease (at the age of 30 weeks) while the number of thymocytes decreased at that time. Prominent changes of lymphocyte subsets were seen in the liver and peritoneal cavity, namely, expansion of IL‐2Rβ+TCRα βint cells in the liver and of CD5+B220+ cells in the peritoneal cavity. The majority of TCRα βint cells in the liver were NK1.1+, and CD5+B cells in the peritoneal cavity were CD1d+. Proteinuria became prominent in NZB/W F1 mice with the progression of disease. In parallel with this progression, the proportion of NKT cells decreased slightly in the liver, but their absolute number remained at a high level in this organ. These NKT cells were CD4+ and used an invariant chain of Vα14Jα281 for TCRα. Reflecting the elevation of CD5+B cells, autoantibodies against hepatocyte cytoplasmand denatured DNA were detected in sera. Although NKT cells are known to be immunoregulatory cells in some autoimmune mice, the present results raise the possibility that NKT cells as well as CD5+B cells might be associated with the onset of autoimmune diseases in NZB/W F1 mice. Indeed, NKT cells in F1 mice had a high potential to induce autoimmune‐like inflammationwhen α–galactosylceramide was administered or when active NKT cells were transferred into young F1 mice.

Serpins (serine protease inhibitors) are ubiquitous, complex, and highly active regulatory molecules that effectively control multiple coagulation, inflammatory, and neuroendocrine pathways (1-3). The amino acid sequence in the reactive center loop (RCL) 3 of serpins acts as bait for target serine proteases, initiating structural changes in the serpin-protease complex and culminating in suicide inhibition (1-3). This same RCL can insert into the neighboring ␤-sheet A in other serpins in serpinopathies, causing serpin aggregates induced by genetic mutations and causing disease as for anti-thrombin III (SERPIN C1, ATIII), ␣-1 antitrypsin (SERPIN A1, AAT), and neuroserpin (SERPIN I1, NSP). Whereas the amino acid residues in the RCL provide target P1-P1Ј sequences, referred to as a scissile bond, serpins also require the greater part of the protein structure to function with true serpin-protease inhibitory activity (4, 5). However, as for other proteins, peptides derived during protein metabolism may act to extend serpin activity beyond the initial suicide-inhibitory function, both increasing and decreasing responses (6 -9). In prior work, significant and prolonged antiinflammatory functions have been detected with myxomavirus-derived Serp-1 (10 -17) and mammalian serpin NSP purified protein injections in animal models of vascular disease (18,19). We have hypothesized that peptides produced by protease cleavage of the RCL sequence during natural proteolytic metabolism of Serp-1 or NSP may extend serpin activity, increasing anti-inflammatory activity after serpin-protease complex formation. Thus, these serpin RCL peptide metabolites have the theoretical potential to interfere with either protease activity by acting as a protease bait or inhibitors or to inhibit other serpins by inserting into the ␤-sheet.Many proteins have active metabolites providing additional and/or expanded functions. Peptides derived from calreticulin (20) and apolipoprotein E (Ep1B) (21) have proven anti-atherogenic activity, reducing inflammation and plaque growth in animal models. Serpins also have reported active terminal peptide metabolites. Among the serpins, angiotensinogen is a protein with serpin structure but lacking serpin inhibitory activity (6).