Search

BACKGROUND. NK cells are activated by innate cytokines and viral ligands to kill virus-infected cells. These functions are enhanced during secondary immune responses and after vaccination by synergy with effector T cells and virus-specific antibodies. In human Ebola virus infection, clinical outcome is strongly associated with the initial innate cytokine response, but the role of NK cells has not been thoroughly examined. METHODS. The novel 2-dose heterologous Adenovirus type 26.ZEBOV (Ad26.ZEBOV) and modified vaccinia Ankara-BN-Filo (MVA-BN-Filo) vaccine regimen is safe and provides specific immunity against Ebola glycoprotein, and is currently in phase 2 and 3 studies. Here, we analyzed NK cell phenotype and function in response to Ad26.ZEBOV, MVA-BN-Filo vaccination regimen and in response to in vitro Ebola glycoprotein stimulation of PBMCs isolated before and after vaccination. RESULTS. We show enhanced NK cell proliferation and activation after vaccination compared with baseline. Ebola glycoprotein-induced activation of NK cells was dependent on accessory cells and TLR-4-dependent innate cytokine secretion (predominantly from [CD14.sup.+] monocytes) and enriched within less differentiated NK cell subsets. Optimal NK cell responses were dependent on IL-18 and IL-12, whereas IFN-[gamma] secretion was restricted by high concentrations of IL-10. CONCLUSION. This study demonstrates the induction of NK cell effector functions early after Ad26.ZEBOV, MVA-BN-Filo vaccination and provides a mechanism for the activation and regulation of NK cells by Ebola glycoprotein. TRIAL REGISTRATION. ClinicalTrials.gov NCT02313077. FUNDING. United Kingdom Medical Research Council Studentship in Vaccine Research, Innovative Medicines Initiative 2 Joint Undertaking, EBOVAC (grant 115861) and Crucell Holland (now Janssen Vaccines and Prevention B.V.), European Union's Horizon 2020 research and innovation programme and European Federation of Pharmaceutical Industries and Associations (EFPIA)., Introduction Ebola virus infection causes a rapid-onset severe acute hemorrhagic fever (Ebola virus disease, EVD) with mortality ranging from 25% to 90% depending on the outbreak (1). Clinical development of [...]

Background: Antibody Fc-mediated functions, such as antibody-dependent cellular cytotoxicity, contribute to vaccine-induced protection against viral infections. Fc-mediated function of anti-Ebola glycoprotein (GP) antibodies suggest that Fc-dependent activation of effector cells, including natural killer (NK) cells, could play a role in vaccination against Ebola virus disease.Methods: We analyzed the effect on primary human NK cell activation of anti-Ebola GP antibody in the serum of United Kingdom-based volunteers vaccinated with the novel 2-dose heterologous adenovirus type 26.ZEBOV, modified vaccinia Ankara-BN-Filo vaccine regimen.Results: We demonstrate primary human NK cell CD107a and interferon γ expression, combined with down-regulation of CD16, in response to recombinant Ebola virus GP and post-vaccine dose 1 and dose 2 serum samples. These responses varied significantly with vaccine regimen, and NK cell activation was found to correlate with anti-GP antibody concentration. We also reveal an impact of NK cell differentiation phenotype on antibody-dependent NK cell activation, with highly differentiated CD56dimCD57+ NK cells being the most responsive.Conclusions: These findings highlight the dual importance of vaccine-induced antibody concentration and NK cell differentiation status in promoting Fc-mediated activation of NK cells after vaccination, raising a potential role for antibody-mediated NK cell activation in vaccine-induced immune responses. [ABSTRACT FROM AUTHOR]

Basophils are mostly known for their involvement in allergic reactions. Recent studies in mice indicate a role for basophils in the induction of adaptive immunity, especially T helper 2 ( Th2) responses. Therefore, it would be highly important to understand how basophils respond to pathogen-associated molecules, such as ligands for toll-like receptors ( TLRs), and if the basophils could promote Th2 responses via these stimuli. To this end, the activation of basophils via TLRs in combination with activation via Ig E was studied, as well as its effect on T helper cell skewing. Using quantitative PCR, we demonstrated the presence of m RNA for TLRs 1-8 in human basophils. Basophils responded to TLR triggering with differential cytokine production, but not with degranulation. Simultaneous triggering of TLRs and Ig E led to synergy in production of IL-4, IL-8, IL-13, and RANTES. Furthermore, the synergistic effects on basophils mediated by Ig E and TLR-4 triggering allowed robust Th2 skewing upon activation of naïve human CD4+ T cells. Our data show that human basophils respond to TLR ligands in synergy with Ig E-mediated activation and that the cytokines produced can promote Th2 differentiation. These results indicate a role for basophils in the regulation of T-cell responses in humans. [ABSTRACT FROM AUTHOR]

Both IL-21 and TLR agonists are important regulators of B cell responses, and the combination of IL-21 and TLR stimulation results in increased Ab production. However, it is not clear yet how IL-21 interacts with TLR signaling in B cells. In this study, we show that IL-21 enhances TLR-induced IgG production, whereas it has no effect on TLR-induced IL-6 production by human B cell cultures. These observations are explained by the finding that IL-21 augments TLR-induced IgG production via the TLR- MyD88-STAT3 pathway but not the classical TLR-MyD88-NF-κB pathway. We further demonstrate that stimulation of human B cells with IL-21 and TLR7/8 or TLR9 agonists increases the phosphorylation of STAT3, whereas the activation of NF-κB is not affected. Interestingly, like IL-21, IL-10 in combination with TLR signaling also enhances phosphorylation of STAT3, resulting in an increase of IgG production. Hence, IL-21 and IL-10 increase the activity of the TLR-MyD88-STAT3 pathway in human B cells via enhancing the phosphorylation of STAT3 for Ab production. [ABSTRACT FROM AUTHOR]

DX5+ CD4+ T cells have been shown to dampen collagen-induced arthritis and delayed-type hypersensitivity reactions in mice. These cells are also potent modulators of T-helper cell responses through direct effects on CD4+ T cells in an IL-4 dependent manner. To further characterize this T-cell population, we studied their effect on DCs and the potential consequences on T-cell activation. Here, we show that mouse DX5+ CD4+ T cells modulate DCs by robustly inhibiting IL-12 production. This modulation is IL-10 dependent and does not require cell contact. Furthermore, DX5+ CD4+ T cells modulate the surface phenotype of LPS-matured DCs. DCs modulated by DX5+ CD4+ T-cell supernatant express high levels of the co-inhibitor molecules PDL-1 and PDL-2. OVA-specific CD4+ T cells primed with DCs exposed to DX5+ CD4+ T-cell supernatant produce less IFN-γ than CD4+ T cells primed by DCs exposed to either medium or DX5− CD4+ T-cell supernatant. The addition of IL-12 to the co-culture with DX5+ DCs restores IFN-γ production. When IL-10 present in the DX5+ CD4+ T-cell supernatant is blocked, DCs re-establish their ability to produce IL-12 and to efficiently prime CD4+ T cells. These data show that DX5+ CD4+ T cells can indirectly affect the outcome of the T-cell response by inducing DCs that have poor Th1 stimulatory function. [ABSTRACT FROM AUTHOR]

Introduction: Abatacept is a fusion protein of human cytotoxic T-lymphocyte-associated protein (CTLA)-4 and the Fc portion of human immunoglobulin G1 (IgG1). It is believed to be effective in the treatment of rheumatoid arthritis by inhibiting costimulation of T cells via blocking CD28-B7 interactions as CTLA-4 binds to both B7.1 (CD80) and B7.2 (CD86). However, the interaction of CD28 with B7 molecules is crucial for activation of naive cells, whereas it is unclear whether the action of already activated CD4(+) T cells, which are readily present in established disease, also depends on this interaction. The aim of this study was to determine whether the mode of action of abatacept depends solely on its ability to halt T cell activation in established disease., Methods: Arthritis was induced in thymectomized male DBA/1 mice by immunisation with bovine collagen type II. The mice were subsequently depleted for CD4(+) T cells. Abatacept or control treatment was started when 80 % of the mice showed signs of arthritis. Arthritis severity was monitored by clinical scoring of the paws, and anti-collagen antibody levels over time were determined by enzyme-linked immunosorbent assay., Results: Treatment with abatacept in the absence of CD4(+) T cells resulted in lower disease activity. This was associated with decreasing levels of collagen-specific IgG1 and IgG2a antibodies, whereas the antibody levels in control or CD4(+) T cell-depleted mice increased over time., Conclusions: These results show that abatacept decreased disease activity in the absence of CD4(+) T cells, indicating that the mode of action of abatacept in established arthritis does not depend entirely on its effects on CD4(+) T cell activation.