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A Toll-like receptor recognizes bacterial DNA

Introduction Japanese encephalitis (JE) is among the most important viral encephalitides in Asia, especially in rural and suburban areas where rice culture and pig farming coexist. (1-3) It has also occurred rarely and sporadically in northern Australia and parts of the Western Pacific. (4-6) JE is due to infection with the JE virus (JEV), a mosquito-borne flavivirus. The main JEV transmission cycle involves Culex tritaeniorhynchus mosquitoes and similar species that lay eggs in rice paddies and other open water sources, with pigs and aquatic birds as principal vertebrate amplifying hosts. (1,2,7) Humans are generally thought to be dead-end JEV hosts, i.e. they seldom develop enough viremia to infect feeding mosquitoes. Fewer than 1% of human JEV infections result in JE. Approximately 20-30% of JE cases are fatal and 30-50% of survivors have significant neurologic sequelae. (8) JE is primarily a disease of children and most adults in endemic countries have natural immunity after childhood infection, but all age groups are affected. In most temperate areas of Asia, JEV is transmitted mainly during the warm season, when large epidemics can occur. In the tropics and subtropics, transmission can occur year-round but often intensifes during the rainy season. (1-3) The global incidence of JE is unknown because the intensity and quality of JE surveillance and the availability of diagnostic laboratory testing vary throughout the world. Countries that have implemented high-quality childhood JE vaccination programmes have seen a dramatic decline in JE incidence. Although JE is reportable to the World Health Organization (WHO) by its Member States, reporting is highly variable and incomplete. In the late 1980s, Burke and Leake estimated that 50 000 new cases of JE occurred annually among the 2.4 billion people living in the 16 Asian countries considered endemic at the time (approximate overall annual incidence: 2 per 100 000). (2) In the intervening two decades, despite major population growth, urbanization, changes in agricultural practices and increased use of the JE vaccine in many countries, this figure has been widely quoted, including very recently. (9-13) In 2000, assuming an annual, age-group-specific incidence of 25 cases per 100 000, Tsai estimated that in the absence of vaccination 175 000 cases of JE would occur annually among Asian children aged 0-14 years living in rural areas. (14) The current study used more recent, published, local or national incidence estimates and current population data to produce an updated estimate of the annual global incidence of JE. Methods We approximated the JE-affected territory of each of the 24 countries endemic for JE using a recent update (15) of an earlier approximation by Tsai (16) with some modifications (Table 1, available at: http://www.who.int/bulletin/ volumes/89/10/10-085233). Based on these same approximations, (15,16) we then stratified the JE-affected territory of some countries (e.g. China excluding Taiwan, India and Nepal) into two or more incidence strata. Because suitable studies of JE incidence were not available for every endemic country or incidence stratum, we sorted JE-endemic countries and incidence strata into 10 incidence groups (A, B, C1, C2 and D through I) based primarily on geographic proximity, ecologic similarity, vaccine programme similarity. Table 1 briefly describes the status of each endemic country's JE vaccination programme as of 2009, according to recent publications and unpublished sources. (8,17-20) Incidence data We identified studies that contained potentially useful data on the incidence of JE in Asia in a manner similar to the one used in a recent study of global typhoid fever incidence. (21) Whenever possible, this review followed the relevant guidelines for Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA). (22) The review process is described as follows and no protocol is available. …

Estimated Global Incidence of Japanese Encephalitis: A Systematic review/Estimation De L'incidence Mondiale De L'encephalite Japonaise: Une Evaluation Systematique/ Incidencia Global Estimada De la Encefalitis Japonesa: Una Revision Sistematica

The immunology of the porcine skin and its value as a model for human skin.

Hepatocyte growth factor (HGF) plays an important role in many biological events such as angiogenesis, cell proliferation, anti-fibrosis and antiapoptosis. It is well known that HGF promotes tumor progression and suppresses development of fibrosis after tissue injury. In contrast, its role in immune-mediated disorders has not been fully clarified. In the present study, we examined the role of HGF in Ag-specific immune response using in vitro studies and an experimental model of allergic airway inflammation. We first confirmed that dendritic cells (DCs) expressed the receptor for HGF, c-met, which was not expressed in T cells. Treatment with HGF both in vitro and in vivo potently suppressed DC functions such as Ag-presenting capacity, thus down-regulating Ag-induced Th1- and Th2-type immune responses. Exogenous administration of the HGF expression plasmid into Ag-primed mice markedly suppressed the development of airway eosinophilia and airway hyperresponsiveness, which was induced by Ag inhalation, with suppression of the Ag-presenting capacity of DCs in the lung. HGF exhibited these immunosuppressive effects without up-regulation of IL-10 or TGF-beta. We also found that expression of endogenous HGF in the lung significantly increased following Ag sensitization and inhalation challenges. Finally, neutralization of endogenous HGF in vivo significantly increased airway eosinophilia and airway hyperresponsiveness with up-regulation of the Ag-presenting capacity of DCs in the lung. These results demonstrated a novel, significant, and possibly therapeutic role of HGF as a potent regulator in immune-mediated disorders such as asthma.

A Novel Role of Hepatocyte Growth Factor as an Immune Regulator through Suppressing Dendritic Cell Function

Over the last few years, we have seen an increasing interest and demand for pigs in biomedical research. Domestic pigs (Sus scrofa domesticus) are closely related to humans in terms of their anatomy, genetics, and physiology, and often are the model of choice for the assessment of novel vaccines and therapeutics in a preclinical stage. However, the pig as a model has much more to offer, and can serve as a model for many biomedical applications including aging research, medical imaging, and pharmaceutical studies to name a few. In this review, we will provide an overview of the innate immune system in pigs, describe its anatomical and physiological key features, and discuss the key players involved. In particular, we compare the porcine innate immune system to that of humans, and emphasize on the importance of the pig as model for human disease.

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The porcine innate immune system: an update.

Despite the central role that dendritic cells (DC) play in immune regulation and antigen presentation, little is known about porcine DC In this study, two sources of DC were employed Bone marrow haematopoietic cell-derived DC (BM-DC) were generated using granulocyte-macrophage colony-stimulating factor (GM-CSF) in the presence or absence of tumour necrosis factor-alpha (TNF-alpha) Monocyte-derived DC (Momicron-DC) were generated with GM-CSF and interleukin-4 (IL-4) In both systems, non-adherent cells developed with dendritic morphology, expressing high levels of major histocompatibility complex (MHC) class II The presence of TNF-alpha increased the BM-DC yield, and enhanced T-cell stimulatory capacity Both BM-DC and Momicron-DC expressed the pan-myeloid marker SWC3, as well as CD1 and CD80/86, but were also CD14+ and CD16+ The CD16 molecule was functional, acting as a low-affinity Fc receptor In contrast, the CD14 on DC appeared to differ functionally from monocyte CD14: attempts to block CD14, in terms of lipopolysaccharide (LPS)-induced procoagulant activity (PCA), failed The use of TNF-alpha or LPS for DC maturation induced up-regulation of MHC class II and/or CD80/86, but also CD14 Allogeneic mixed leucocyte reactions and staphylococcal enterotoxin B antigen presentation assays demonstrated that these DC possessed potent T-cell stimulatory capacity No T helper cell polarization was noted Both the BM-DC and the Momicron-DC induced a strong interferon-gamma and IL-4 response Taken together, porcine DC generated in vitro possess certain characteristics relating them to DC from other species including humans, but the continued presence of CD14 and CD16 on mature and immature porcine DC was a notable difference

Porcine dendritic cells generated in vitro: morphological, phenotypic and functional properties.

Sensing of viruses by dendritic cell (DC) pathogen recognition receptors (PRRs) represents a critical event during innate antiviral immune responses. Identification of these PRRs has often posed a problem due to difficulties in performing gene function studies in the naturally targeted hosts. Consequently, we developed a lentivirus (LV)-based strategy for specific gene knockdown in porcine DC. Short hairpin RNAs (shRNAs) were designed, targeting toll-like receptor 7 (TLR7) and the adaptor protein MyD88. As cellular targets, monocyte-derived DC (MoDC) and Flt3 ligand-induced DC (Flt3L-DC), DC precursors including monocytes and haematopoietic stem cells (HSCs) as well as plasmacytoid DCs (pDCs) were employed. Transduction efficiencies ranged from 40 to 95%. The LV-mediated shRNA delivery was functionally active, reducing TLR7 and MyD88 mRNA in MoDC and conventional Flt3L-DC, and blunting the responsiveness to TLR7 ligands in Flt3L-DC. Although infection of MoDC by the LV did neither influence MHC class II and CD80/86 expressions, nor cytokine responses, the infection of Flt3L-DC induced a phenotypic maturation. Furthermore, the interaction of the LV with pDC induced high levels of interferon-α. Taken together, these studies characterize the interaction of the LV with different DC subsets and demonstrate the suitability of LV-mediated small interfering RNA delivery for targeting PRR knockout for MoDC and conventional Flt3L-DC.

Toll-like receptor 7 and MyD88 knockdown by lentivirus-mediated RNA interference to porcine dendritic cell subsets.

Japanese encephalitis virus (JEV) is a neurotropic flavivirus causing mortality and morbidity in humans. Severe Japanese encephalitis cases display strong inflammatory responses in the central nervous system and an accumulation of viral particles in specific brain regions. Microglia cells are the unique brain-resident immune cell population with potent migratory functions and have been proposed to act as a viral reservoir for JEV. Animal models suggest that the targeting of microglia by JEV is partially responsible for inflammatory reactions in the brain. Nevertheless, the interactions between human microglia and JEV are poorly documented. Using human primary microglia and a new model of human blood monocyte-derived microglia, the present study explores the interaction between human microglia and JEV as well as the role of these cells in viral transmission to susceptible cells. To achieve this work, vaccine-containing inactivated JEV and two live JEV strains were applied on human microglia. Live JEV was non-cytopathogenic to human microglia but increased levels of CCL2, CXCL9 and CXCL10 in such cultures. Furthermore, human microglia up-regulated the expression of the fraktalkine receptor CX3CR1 upon exposure to both JEV vaccine and live JEV. Although JEV vaccine enhanced MHC class II on all microglia, live JEV enhanced MHC class II mainly on CX3CR1+ microglia cells. Importantly, human microglia supported JEV replication, but infectivity was only transmitted to neighbouring cells in a contact-dependent manner. Our findings suggest that human microglia may be a source of neuronal infection and sustain JEV brain pathogenesis.

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Viviane Neuhaus

Papers

Porcine dendritic cells generated in vitro: morphological, phenotypic and functional properties.

Toll-like receptor 7 and MyD88 knockdown by lentivirus-mediated RNA interference to porcine dendritic cell subsets.

Interactions of human microglia cells with Japanese encephalitis virus.

Porcine B-cell activating factor promotes anti-FMDV antibodies in vitro but not in vivo after DNA vaccination of pigs.