Selective induction of the monocyte-attracting chemokines MCP-1 and IP-10 in vesicular stomatitis virus-infected human monocytes

TLR7 and TLR8 activate distinct pathways in monocytes during RNA virus infection

Human blood CD14+monocytes are bone marrow–derived white blood cells that sense and respond to pathogens. Although innate immune activation by RNA viruses preferentially occurs through intracellular RIG-I–like receptors, other nucleic acid recognition receptors, such as Toll-like receptors (TLRs), play a role in finely programming the final outcome of virus infection. Here, we dissected how human monocytes respond to infection with either Coxsackie (CV), encephalomyocarditis (EMCV), influenza A (IAV), measles (MV), Sendai (SV), or vesicular stomatitis (VSV) virus. We found that in monocytes, type I interferon (IFN) and cytokine responses to infection were RNA virus specific and differentially involved TLR7 and TLR8, which sense single-stranded RNA. These TLRs activated distinct signaling cascades in monocytes, which correlated with differences in the production of cytokines involved in the polarization of CD4+T helper cells. Furthermore, we found that TLR7 signaling specifically increased expression of the transcription factor FOSL1, which reduced IL-27 and TNFα production by monocytes. TLR7, but not TLR8, activation of monocytes also stimulated Ca2+flux that prevented type I IFN responses. Our work demonstrates that in human monocytes, TLR7 and TLR8 triggered different signaling pathways that contribute to distinct phenotypes during RNA virus infection. In addition, we defined individual targets within these pathways that promoted specific T helper and antiviral responses.

A dose-dependent plasma signature of the safety and immunogenicity of the rVSV-Ebola vaccine in Europe and Africa

The 2014-2015 Ebola epidemic affected several African countries, claiming more than 11,000 lives and leaving thousands with ongoing sequelae. Safe and effective vaccines could prevent or limit future outbreaks. The recombinant vesicular stomatitis virus-vectored Zaire Ebola (rVSV-ZEBOV) vaccine has shown marked immunogenicity and efficacy in humans but is reactogenic at higher doses. To understand its effects, we examined plasma samples from 115 healthy volunteers from Geneva who received low-dose (LD) or high-dose (HD) vaccine or placebo. Fifteen plasma chemokines/cytokines were assessed at baseline and on days 1, 2 to 3, and 7 after injection. Significant increases in monocyte-mediated MCP-1/CCL2, MIP-1β/CCL4, IL-6, TNF-α, IL-1Ra, and IL-10 occurred on day 1. A signature explaining 68% of cytokine/chemokine vaccine-response variability was identified. Its score was higher in HD versus LD vaccinees and was associated positively with vaccine viremia and negatively with cytopenia. It was higher in vaccinees with injection-site pain, fever, myalgia, chills, and headache; higher scores reflected increasing severity. In contrast, HD vaccinees who subsequently developed arthritis had lower day 1 scores than other HD vaccinees. Vaccine dose did not influence the signature despite its influence on specific outcomes. The Geneva-derived signature associated strongly (ρ = 0.97) with that of a cohort of 75 vaccinees from a parallel trial in Lambaréné, Gabon. Its score in Geneva HD vaccinees with subsequent arthritis was significantly lower than that in Lambaréné HD vaccinees, none of whom experienced arthritis. This signature, which reveals monocytes' critical role in rVSV-ZEBOV immunogenicity and safety across doses and continents, should prove useful in assessments of other vaccines.

Role for monocyte chemoattractant protein-1 in the induction of chronic muscle pain in the rat

While raised levels of monocyte chemoattractant protein 1 (MCP-1) have been observed in patients with chronic muscle pain, direct evidence for its role as an algogen in skeletal muscle is still lacking. In the rat, MCP-1 induces a dose-dependent mechanical hyperalgesia lasting for up to 6weeks. Following recovery, rats exhibited a markedly prolonged hyperalgesia to an intramuscular injection of prostaglandin E2, hyperalgesic priming. Intrathecal pretreatment with isolectin B4 (IB4)-saporin, which selectively destroys IB4-positive (IB4+) nociceptors, markedly decreased MCP-1-induced hyperalgesia and prevented the subsequent development of priming. To evaluate the involvement of MCP-1 in stress-induced chronic pain we administered, intrathecally, antisense (AS) or mismatch oligodeoxynucleotides directed against CCR2 (the canonical receptor for MCP-1) mRNA, during the exposure to water-avoidance stress, a model of stress-induced persistent muscle pain. The AS treatment attenuated this hyperalgesia, whereas IB4-saporin abolished water-avoidance stress-induced muscle hyperalgesia and prevented stress-induced hyperalgesic priming. These results indicate that MCP-1 induces persistent muscle hyperalgesia and a state of latent chronic sensitization to other algogens, by action on its cognate receptor on IB4+ nociceptors. Because MCP-1 also contributes to stress-induced widespread chronic muscle pain, it should be considered as a player in chronic musculoskeletal pain syndromes.

Antibody and inflammatory response-mediated severity of pandemic 2009 (pH1N1) influenza virus

Influenza A virus causes significant morbidity and mortality each year worldwide due to antigenic drift, punctuated by infrequent pandemics following antigenic shift. H1N1 subtype of pandemic 2009 (pH1N1) influenza virus lineages has continued to circulate in humans and raised severe concerns about its pandemic developments. The pathogenesis of the disease and its progression as post-infectious sequelae is not well understood. Moderate inflammatory response protects against the ill effects and hyper-inflammatory response promotes the pathogenesis in disease progression. Samples were screened by RT-PCR and classified in pandemic 2009 (pH1N1), Influenza A virus infected patient. Further antibody titer was analyzed by hemagglutination inhibition assay and cytokine/chemokine response by Cytometric bead array assy. Screening of 216 patients shows 63 were belongs to pH1N1 influenza virus infection and 47 were Influenza A virus infected and 106 samples were negative for these viruses, were used as a disease control. Apart from that 100 samples were taken for healthy control. Lower antibody titer was found in patient infected with pH1N1/Influenza A virus and expression of cytokines (IL-6, IL-8, and IL-10) and chemokine MCP-1 was higher in patient infected with pH1N1 compare to healthy/disease control however there was no significant difference observed in the expression of pro-inflammatory cytokines TNF-α and antiviral cytokine IFN-γ in pH1N1 influenza virus infected patients.

The tiers and dimensions of evasion of the type I interferon response by human cytomegalovirus

Human cytomegalovirus (HCMV) is a member of the β-herpesvirus family that invariably occupies hosts for life despite a consistent multi-pronged antiviral immune response that targets the infection. This persistence is enabled by the large viral genome that encodes factors conferring a wide assortment of sophisticated, often redundant phenotypes that disable or otherwise manipulate impactful immune effector processes. The type I interferon system represents a first line of host defense against infecting viruses. The physiological reactions induced by secreted interferon act to effectively block replication of a broad spectrum of virus types, including HCMV. As such, the virus must exhibit counteractive mechanisms to these responses that involve their inhibition, tolerance, or re-purposing. The goal of this review is to describe the impact of the type I interferon system on HCMV replication and to showcase the number and diversity of strategies employed by the virus that allow infection of hosts in the presence of interferon-dependent activity.

Use of type I interferon-inducible mRNAs as pharmacodynamic markers and potential diagnostic markers in trials with sifalimumab, an anti-IFNα antibody, in systemic lupus erythematosus

Type I interferons are implicated in the pathogenesis of systemic lupus erythematosus (SLE). Type I interferon-inducible mRNAs are widely and concordantly overexpressed in the periphery and involved tissues of a subset of SLE patients, and provide utility as pharmacodynamic biomarkers to aid dose selection, as well as potential indicators of patients who might respond favorably to anti-IFNα therapy in SLE. We implemented a three-tiered approach to identify a panel of type I interferon-inducible mRNAs to be used as potential pharmacodynamic biomarkers to aid dose selection in clinical trials of sifalimumab, an anti-IFNα monoclonal antibody under development for the treatment of SLE. In a single-dose escalation phase 1 trial, we observed a sifalimumab-specific and dose-dependent inhibition of the overexpression of type I interferon-inducible mRNAs in the blood of treated subjects. Inhibition of expression of type I interferon-inducible mRNAs and proteins was also observed in skin lesions of SLE subjects from the same trial. Inhibiting IFNα resulted in a profound downstream effect in these SLE subjects that included suppression of mRNAs of B-cell activating factor belonging to the TNF family and the signaling pathways of TNFα, IL-10, IL-1β, and granulocyte-macrophage colony-stimulating factor in both the periphery and skin lesions. A scoring method based on the expression of type I interferon-inducible mRNAs partitioned SLE patients into two distinct subpopulations, which suggests the possibility of using these type I interferon-inducible genes as predictive biomarkers to identify SLE patients who might respond more favorably to anti-type I interferon therapy.

Gene expression contributing to recruitment of circulating cells in response to vesicular stomatitis virus infection of the CNS

During acute Vesicular Stomatitis Virus (VSV) infection of the mouse central nervous system, neutrophils, natural killer (NK) cells, macrophages, and CD4+ and CD8+ T cells are recruited from the circulation in response to chemokines and cytokines. This study elucidated the production of these factors and infiltration of these peripheral cells. Chemokines that were observed included CCL1, CXCL10 (IP-10), CCL5 (RANTES), CCL3 (MIP-1alpha), CCL4 (MIP-1beta), CXCL1 (MIP-2), CCL2 (MCP-1), and CCL11 (eotaxin). Cytokines produced in response to the infection include IL-1 and interferon-gamma, but not type I interferons. Neutrophils are the first recruited cell type, appearing as early as 24 h after intranasal application of the virus. NK cells follow, but T cells are not detected until 6 days postinfection.

Rabies virus stimulates nitric oxide production and CXC chemokine ligand 10 expression in macrophages through activation of extracellular signal-regulated kinases 1 and 2

Macrophages represent an essential part of innate immunity, and the viral infection of macrophages results in the release of multiple proinflammatory mediators, such as nitric oxide (NO), cytokines, and chemokines. This study was undertaken to define the molecular mechanism of macrophage activation in response to rabies virus (RV) infection. In RAW264 murine macrophage cells, a well-characterized macrophage model, RV replication was strictly restricted, whereas cell proliferation was significantly enhanced upon RV inoculation. Transcriptional analyses for the expression of inducible forms of NO synthase (iNOS), cytokines, and chemokines revealed that RV virions potentiate the gene expression of iNOS and CXC chemokine ligand 10 (CXCL10), a major chemoattractant of T helper cell type 1. However, RV stimulation had little or no effect on the expression profiles of proinflammatory cytokines and other types of chemokines. In macrophages stimulated with UV-inactivated RV virions, as well as infectious viruses, the phosphorylation of extracellular signal-regulated kinase (ERK) 1 and 2, members of the mitogen-activated protein kinase family, was significantly induced. Specific inhibitors of MAPK/ERK kinase reduced the RV-induced production of NO and CXCL10. Furthermore, the RV-induced activation of the ERK1/2 pathway was severely impaired by the neutralization of the endosomal and lysosomal pH environment with lysosomotropic agents, indicating that endocytosis is a key step leading to the activation of ERK1/2 signaling. Taken together, these results suggest that the ERK1/2-mediated signaling pathway plays a cardinal role in the selective activation of macrophages in response to RV virions, thereby regulating cellular functions during virus infection.

The inducible CXCR3 ligands control plasmacytoid dendritic cell responsiveness to the constitutive chemokine stromal cell-derived factor 1 (SDF-1)/CXCL12

The recruitment of selected dendritic cell (DC) subtypes conditions the class of the immune response. Here we show that the migration of human plasmacytoid DCs (pDCs), the blood natural interferon alpha-producing cells, is induced upon the collective action of inducible and constitutive chemokines. Despite expression of very high levels of CXCR3, pDCs do not respond efficiently to CXCR3 ligands. However, they migrate in response to the constitutive chemokine stromal cell-derived factor 1 (SDF-1)/CXCL12 and CXCR3 ligands synergize with SDF-1/CXCL12 to induce pDC migration. This synergy reflects a sensitizing effect of CXCR3 ligands, which, independently of a gradient and chemoattraction, decrease by 20-50-fold the threshold of sensitivity to SDF-1/CXCL12. Thus, the ability of the constitutive chemokine SDF-1/CXCL12 to induce pDC recruitment might be controlled by CXCR3 ligands released during inflammation such as in virus infection. SDF-1/CXCL12 and the CXCR3 ligands Mig/CXCL9 and ITAC/CXCL1 display adjacent expression both in secondary lymphoid organs and in inflamed epithelium from virus-induced pathologic lesions. Because pDCs express both the lymph node homing molecule l-selectin and the cutaneous homing molecule cutaneous lymphocyte antigen, the cooperation between inducible CXCR3 ligands and constitutive SDF-1/CXCL12 may regulate recruitment of pDCs either in lymph nodes or at peripheral sites of inflammation.