High Prevalence of Both Humoral and Cellular Immunity to Zaire ebolavirus among Rural Populations in Gabon

To better understand Zaire ebolavirus (ZEBOV) circulation and transmission to humans, we conducted a large serological survey of rural populations in Gabon, a country characterized by both epidemic and non epidemic regions. The survey lasted three years and covered 4,349 individuals from 220 randomly selected villages, representing 10.7% of all villages in Gabon. Using a sensitive and specific ELISA method, we found a ZEBOV-specific IgG seroprevalence of 15.3% overall, the highest ever reported. The seroprevalence rate was significantly higher in forested areas (19.4%) than in other ecosystems, namely grassland (12.4%), savannah (10.5%), and lakeland (2.7%). No other risk factors for seropositivity were found. The specificity of anti-ZEBOV IgG was confirmed by Western blot in 138 individuals, and CD8 T cells from seven IgG+ individuals were shown to produce IFN-γ after ZEBOV stimulation. Together, these findings show that a large fraction of the human population living in forested areas of Gabon has both humoral and cellular immunity to ZEBOV. In the absence of identified risk factors, the high prevalence of “immune” persons suggests a common source of human exposure such as fruits contaminated by bat saliva. These findings provide significant new insights into ZEBOV circulation and human exposure, and raise important questions as to the human pathogenicity of ZEBOV and the existence of natural protective immunization

Intestinal intraepithelial lymphocyte activation promotes innate antiviral resistance.

Unrelenting environmental challenges to the gut epithelium place particular demands on the local immune system. In this context, intestinal intraepithelial lymphocytes (IEL) compose a large, highly conserved T cell compartment, hypothesized to provide a first line of defence via cytolysis of dysregulated intestinal epithelial cells (IEC) and cytokine-mediated re-growth of healthy IEC. Here we show that one of the most conspicuous impacts of activated IEL on IEC is the functional upregulation of antiviral interferon (IFN)-responsive genes, mediated by the collective actions of IFNs with other cytokines. Indeed, IEL activation in vivo rapidly provoked type I/III IFN receptor-dependent upregulation of IFN-responsive genes in the villus epithelium. Consistent with this, activated IEL mediators protected cells against virus infection in vitro, and pre-activation of IEL in vivo profoundly limited norovirus infection. Hence, intraepithelial T cell activation offers an overt means to promote the innate antiviral potential of the intestinal epithelium.Support was provided by the Wellcome Trust (A.C.H., J.L.H., G.R) and Cancer Research UK (A.C.H.), Department of Health via the National Institute for Health Research (NIHR) comprehensive Biomedical Research Centre award to Guy’s & St Thomas’ NHS Foundation Trust (L.A.-D.; A.C.H.); Marie Curie and EMBO fellowships (M.S.).This is the final published version. It first appeared at http://www.nature.com/ncomms/2015/150519/ncomms8090/full/ncomms8090.html

The neuropeptide NMU amplifies ILC2-driven allergic lung inflammation

Type 2 innate lymphoid cells (ILC2s) both contribute to mucosal homeostasis and initiate pathologic inflammation in allergic asthma. However, the signals that direct ILC2s to promote homeostasis versus inflammation are unclear. To identify such molecular cues, we profiled mouse lung-resident ILCs using single-cell RNA sequencing at steady state and after in vivo stimulation with the alarmin cytokines IL-25 and IL-33. ILC2s were transcriptionally heterogeneous after activation, with subpopulations distinguished by expression of proliferative, homeostatic and effector genes. The neuropeptide receptor Nmur1 was preferentially expressed by ILC2s at steady state and after IL-25 stimulation. Neuromedin U (NMU), the ligand of NMUR1, activated ILC2s in vitro, and in vivo co-administration of NMU with IL-25 strongly amplified allergic inflammation. Loss of NMU-NMUR1 signalling reduced ILC2 frequency and effector function, and altered transcriptional programs following allergen challenge in vivo. Thus, NMUR1 signalling promotes inflammatory ILC2 responses, highlighting the importance of neuro-immune crosstalk in allergic inflammation at mucosal surfaces

Human but not mouse hepatocytes respond to interferon-lambda in vivo

The type III interferon (IFN) receptor is preferentially expressed by epithelial cells. It is made of two subunits: IFNLR1, which is specific to IFN-lambda (IFN-γ) and IL10RB, which is shared by other cytokine receptors. Human hepatocytes express IFNLR1 and respond to IFN-γ. In contrast, the IFN-γ response of the mouse liver is very weak and IFNLR1 expression is hardly detectable in this organ. Here we investigated the IFN-γ response at the cellular level in the mouse liver and we tested whether human and mouse hepatocytes truly differ in responsiveness to IFN-γ. When monitoring expression of the IFN-responsive Mx genes by immunohistofluorescence, we observed that the IFN-γ response in mouse livers was restricted to cholangiocytes, which form the bile ducts, and that mouse hepatocytes were indeed not responsive to IFN-γ. The lack of mouse hepatocyte response to IFN-γ was observed in different experimental settings, including the infection with a hepatotropic strain of influenza A virus which triggered a strong local production of IFN-γ. With the help of chimeric mice containing transplanted human hepatocytes, we show that hepatocytes of human origin readily responded to IFN-γ in a murine environment. Thus, our data suggest that human but not mouse hepatocytes are responsive to IFN-γ in vivo. The non-responsiveness is an intrinsic property of mouse hepatocytes and is not due to the mouse liver micro-environment. © 2014 Hermant et al

Crystal structure of the trimeric prefusion EBOV GP viewed from the top (above) and side (below) [21].

<p>The three monomers in the complex are colored different shades of grey. Immunodominant regions identified in GP are indicated in color for survivors and asymptomatic patients. The color code matches that of the epitopes identified in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0096360#pone-0096360-g003" target="_blank">Figure 3</a>. Molecular surface of the GP trimer viewed from the side (left) and top (right), as viewed down the three-fold axis. Protein Data Bank file number: 3CSY.</p

Mean OD values at 1∶400 serum dilution in patients infected with EBOV during three outbreaks in Gabon, 7 days after symptom onset (Day 7, early humoral response) and 7 or 11 years later (2008, late humoral response), and also in anti-EBOV IgG+ asymptomatic individuals who had never had clinical signs of hemorrhagic fever or who lived in non epidemic areas*.

<p>ODs are color-coded to indicate their intensity (yellow to red). The different colored regions in the proteins indicate the immunodominant domains identified here. *Blank cells indicate that the mean OD was lower than the cut-off. OD: Optical Density. The absorbance cut-off used to identify reactive epitopes is described in the Methodology section.</p

Map of Gabonese villages where the 1996 and 2001 outbreaks occurred.

<p>Map of Gabonese villages where the 1996 and 2001 outbreaks occurred.</p

Leukocyte-Derived IFN-α/β and Epithelial IFN-λ Constitute a Compartmentalized Mucosal Defense System that Restricts Enteric Virus Infections

<div><p>Epithelial cells are a major port of entry for many viruses, but the molecular networks which protect barrier surfaces against viral infections are incompletely understood. Viral infections induce simultaneous production of type I (IFN-α/β) and type III (IFN-λ) interferons. All nucleated cells are believed to respond to IFN-α/β, whereas IFN-λ responses are largely confined to epithelial cells. We observed that intestinal epithelial cells, unlike hematopoietic cells of this organ, express only very low levels of functional IFN-α/β receptors. Accordingly, after oral infection of IFN-α/β receptor-deficient mice, human reovirus type 3 specifically infected cells in the lamina propria but, strikingly, did not productively replicate in gut epithelial cells. By contrast, reovirus replicated almost exclusively in gut epithelial cells of IFN-λ receptor-deficient mice, suggesting that the gut mucosa is equipped with a compartmentalized IFN system in which epithelial cells mainly respond to IFN-λ that they produce after viral infection, whereas other cells of the gut mostly rely on IFN-α/β for antiviral defense. In suckling mice with IFN-λ receptor deficiency, reovirus replicated in the gut epithelium and additionally infected epithelial cells lining the bile ducts, indicating that infants may use IFN-λ for the control of virus infections in various epithelia-rich tissues. Thus, IFN-λ should be regarded as an autonomous virus defense system of the gut mucosa and other epithelial barriers that may have evolved to avoid unnecessarily frequent triggering of the IFN-α/β system which would induce exacerbated inflammation.</p></div

IFN-λ restricts reovirus replication in the epithelium and determines virus shedding in feces, whereas type I IFN blocks replication in the lamina propria and inhibits systemic dissemination.

<p>(A-D) Adult wild-type (n = 25), <i>Ifnar1</i>^<i>-/-</i> (n = 18) and <i>Ifnlr1</i>^<i>-/-</i> (n = 27) mice were inoculated intragastrically with 10⁸ pfu of reovirus T3D. Data pooled from several independent experiments. (A) At day 4 post-infection, reovirus replication in small intestinal tissue was analyzed by virus titration. (B) Reovirus titers in feces samples collected from wild-type and mutant mice at day 4 post-infection. (C, D) Immunostaining for reovirus antigen (green), E-cadherin (red) and DAPI (blue) in (C) small intestinal tissue or (D) Peyer’s patches. Images are representative of three independent experiments. Bar = 100 μm. ns = non-significant, ** p<0.01, *** p<0.001.</p