The filovirus Ebola causes hemorrhagic fever with 70 -80% human mortality. High case-fatality rates, as well as known aerosol infectivity, make Ebola virus a potential global health threat and possible biological warfare agent. Development of an effective vaccine for use in natural outbreaks, response to biological attack, and protection of laboratory workers is a higher national priority than ever before. Coexpression of the Ebola virus glycoprotein (GP) and matrix protein (

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.

Ebola virus (EBOV)-like particles (eVLP), composed of the EBOV glycoprotein and matrix viral protein (VP)40 with a lipid membrane, are a highly efficacious method of immunization against EBOV infection. The exact requirements for immunity against EBOV infection are poorly defined at this time. The goal of this work was to determine the requirements for EBOV immunity following eVLP vaccination. Vaccination of BALB/c or C57BL/6 mice with eVLPs in conjunction with QS-21 adjuvant resulted in mixed IgG subclass responses, a Th1-like memory cytokine response, and protection from lethal EBOV challenge. Further, this vaccination schedule led to the generation of both CD4+ and CD8+ IFN-γ+ T cells recognizing specific peptides within glycoprotein and VP40. The transfer of both serum and splenocytes, but not serum or splenocytes alone, from eVLP-vaccinated mice conferred protection against lethal EBOV infection in these studies. B cells were required for eVLP-mediated immunity to EBOV because B cell-deficient mice vaccinated with eVLPs were not protected from lethal EBOV challenge. We also found that CD8+, but not CD4+, T cells are absolutely required for eVLP-mediated protection against EBOV infection. Further, eVLP-induced protective mechanisms were perforin-independent, but IFN-γ-dependent. Taken together, both EBOV-specific humoral and cytotoxic CD8+ T cell responses are critical to mediate protection against filoviruses following eVLP vaccination.

B cell-dependent immunity to rotavirus, an important intestinal pathogen, plays a significant role in viral clearance and protects against reinfection. Human in vitro and murine in vivo models of rotavirus infection were used to delineate the role of primary plasmacytoid DCs (pDCs) in initiating B cell responses. Human pDCs were necessary and sufficient for B cell activation induced by rotavirus. Type I IFN recognition by B cells was essential for rotavirus-mediated B cell activation in vitro and murine pDCs and IFN-α/β-mediated B cell activation after in vivo intestinal rotavirus infection. Furthermore, rotavirus-specific serum and mucosal antibody responses were defective in mice lacking functional pDCs at the time of infection. These data demonstrate that optimal B cell activation and virus-specific antibody secretion following mucosal infection were a direct result of pDC-derived type I IFN. Importantly, viral shedding significantly increased in pDC-deficient mice, suggesting that pDC-dependent antibody production influences viral clearance. Thus, mucosal pDCs critically influence the course of rotavirus infection through rotavirus recognition and subsequent IFN production and display powerful adjuvant properties to initiate and enhance humoral immunity.

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Rotaviruses are the leading cause of severe dehydrating diarrhea in children worldwide. Rotavirus-induced immune responses, especially the T and B cell responses, have been extensively characterized; however, little is known about innate immune mechanisms involved in the control of rotavirus infection. Although increased levels of systemic type I interferon (IFNα and β) correlate with accelerated resolution of rotavirus disease, multiple rotavirus strains, including rhesus rotavirus (RRV), have been demonstrated to antagonize type I IFN production in a variety of epithelial and fibroblast cell types through several mechanisms, including degradation of multiple interferon regulatory factors by a viral nonstructural protein. This report demonstrates that stimulation of highly purified primary human peripheral plasmacytoid dendritic cells (pDCs) with either live or inactivated RRV induces substantial IFNα production by a subset of pDCs in which RRV does not replicate. Characterization of pDC responses to viral stimulus by flow cytometry and Luminex revealed that RRV replicates in a small subset of human primary pDCs and, in this RRV-permissive small subset, IFNα production is diminished. pDC activation and maturation were observed independently of viral replication and were enhanced in cells in which virus replicates. Production of IFNα by pDCs following RRV exposure required viral dsRNA and surface proteins, but neither viral replication nor activation by trypsin cleavage of VP4. These results demonstrate that a minor subset of purified primary human peripheral pDCs are permissive to RRV infection, and that pDCs retain functionality following RRV stimulus. Additionally, this study demonstrates trypsin-independent infection of primary peripheral cells by rotavirus, which may allow for the establishment of extraintestinal viremia and antigenemia. Importantly, these data provide the first evidence of IFNα induction in primary human pDCs by a dsRNA virus, while simultaneously demonstrating impaired IFNα production in primary human cells in which RRV replicates. Rotavirus infection of primary human pDCs provides a powerful experimental system for the study of mechanisms underlying pDC-mediated innate immunity to viral infection and reveals a potentially novel dsRNA-dependent pathway of IFNα induction.

IBD patients harbor distinct microbial communities with functional capabilities different from those seen with healthy people. But is this cause or effect? Answering this question requires data on changes in gut microbial communities leading to disease onset. By performing weekly metagenomic sequencing and mixed-effects modeling on an established mouse model of IBD, we identified several functional pathways encoded by the gut microbiome that covary with host immune status. These pathways are novel early biomarkers that may either enable microbes to live inside an inflamed gut or contribute to immune activation in IBD mice. Future work will validate the potential roles of these microbial pathways in host-microbe interactions and human disease. This study was novel in its longitudinal design and focus on microbial pathways, which provided new mechanistic insights into the role of gut microbes in IBD development.

Endocytosis has recently been implicated in rotavirus (RV) entry. We examined the role of Rabs, which regulate endosomal trafficking, during RV entry. Several structural proteins of neuraminidase-sensitive and -insensitive RVs colocalized with Rab5, an early endosome marker, but not Rab7, a late endosome marker. Dominant-negative and constitutively active mutants demonstrated that Rab5 but not Rab4 or Rab7 affects rhesus RV (RRV) infectivity. These data suggest that early RRV trafficking is confined to the early endosome compartment and requires Rab5. R otavirus (RV), a nonenveloped member of the Reoviridae family, is the single most important cause of severe diarrhea globally and is a leading cause of death in children under the age of 5 (17). The virus particle encloses 11 double-stranded RNA segments within a triple-layered icosahedral capsid. The outermost layer is composed of the glycoprotein VP7 and protruding spikes of trimeric VP4. Two major domains comprise VP4. VP5* forms the foot of the spike, whereas VP8* is the head (5, 6). While the mechanisms governing RV cellular entry are not fully understood, both VP7 and VP4 are required for binding and penetration (15,21). Like fusion mechanisms in enveloped viruses, VP5* is believed to rearrange upon uncoating and membrane interaction, resulting in a folded-back trimeric structure which is proposed to mediate membrane penetration (4,5,26,28,29). Although RV entry was initially thought to occur via direct plasma membrane penetration (7, 13), recent studies indicate that RV traffics through the endosomal pathway (1, 10, 22, 27). As different RV strains, which vary in neuraminidase (NA) sensitivity of cell binding, may use distinct endocytic pathways, a definitive model of RV entry does not currently exist (10,22,27). We recently demonstrated that rhesus RV (RRV) enters a polarized epithelium using the endosomal route, as evidenced by colocalization of trimeric VP7 and VP5* with endosomal markers Rab4 and Rab5 (27). Furthermore, specific pharmacological interventions reduced RRV infectivity (27). Rabs, small cellular GTPases important in endosomal trafficking, are powerful tools for studying endocytosis due to their unique expression in specific endocytic compartments and fine regulation of vesicular trafficking (24). Dominantnegative (DN) and constitutively active (CA) Rab mutants have been widely used to identify the entry trafficking steps required by various viral infections (11,14,16,19,23). Rab5, which is present at the plasma membrane but is preferentially associated with early endosome (EE) vacuoles (23), functions in internalization, transport of newly formed vesicles to the EE, fusion, and trafficking to the late endosome (LE). Rab4 localizes primarily to the EE and regulates recycling to the plasma membrane. Rab7, present on the LE, governs transfer to lysosomes. Rab5 and Rab7 are proposed to be present on the maturing endosome, an intermediary vesicle between the EE and LE (16).Here, we examined the roles of Rab proteins during RRV entry. Rab5 has p...