Regulation of porcine plasmacytoid dendritic cells by cytokines

Age-dependent immune response in pigs against foot-and-mouth disease virus in vitro

Foot-and-mouth disease, one of the most contagious diseases in cloven-hoofed animals, causes significant economic losses. The pathogenesis of foot-and-mouth disease virus (FMDV) infection is known to differ with age of the animals. In this study, we aimed to reveal the difference in immunological response in the initial stage of FMDV infection between piglets and adult pigs. Peripheral blood mononuclear cells (PBMCs) were isolated from 3 piglets (8 weeks old) and 3 pigs (35 weeks old) that were not vaccinated against FMDV. O-type FMDV (2 × 10² median tissue culture infectious dose) was inoculated into porcine PBMCs and the cells were incubated at 37.0°C under 5% CO₂ for various time periods (0, 1, 3, 6, 12, 24, and 48 h). The total RNA was obtained from the FMDV-inoculated PBMCs after each time point, and the virus titer was investigated in these RNA samples. Furthermore, dynamics of mRNA expression of the six tested cytokines (interferon [IFN]-α, IFN-γ, ‎interleukin [IL]-6, IL-8, IL-10, and tumor necrosis factor [TNF]-α) in FMDV-inoculated porcine PBMCs were evaluated by time-series analysis to determine the differences, if any, based on the age of the pigs. The PBMCs of piglets contained the highest quantity of FMDV mRNA at 6 hours post-inoculation (hpi), and the PBMCs of pigs had the highest quantity of FMDV mRNA at 3 hpi. The mean cycle threshold-value in the PBMCs steadily decreased after the peak time point in the piglets and pigs (6 and 3 hpi, respectively). The dynamics of mRNA expression of all cytokines except TNF-α showed age-dependent differences in FMDV-inoculated PBMCs. The mRNA expression of most cytokines was more pronounced in the piglets than in the pigs, implying that the immune response against FMDV showed an age-dependent difference in pigs. In conclusion, within 48 hpi, the 8-week-old piglets responded more rapidly and were more sensitive to FMDV infection than the 35-week-old pigs, which could be associated with the difference in the pathogenesis of FMDV infection among the pigs. These results provide valuable insights into the mechanisms underlying the age-dependent differences in immune response in pigs against FMDV infection.

Skin immune cell characterization in juvenile and adult Göttingen Minipigs

The skin hosts a sophisticated immune system involving responses from both innate and adaptive immune cell populations. Swine skin is close to human skin by its structure, composition and function. In addition, the minipig is considered the model of choice in toxicology studies for drugs applied by the dermal route and developed for both the adult and paediatric indications. However, knowledge on the skin immune system in minipigs, particularly in Göttingen Minipigs, is still limited. The objective of our work was first to characterize the main skin immune populations (Langerhans cells, dermal dendritic cells, macrophages and T lymphocytes) in Göttingen Minipigs. In parallel, we compared the skin immune populations from healthy and immunocompromised piglets following oral treatment with cyclosporin A (CsA) at 10 mg/kg/day. We also explored other pathological conditions using a contact dermatitis model in minipigs challenged with a sensitizer, 2,4-dinitrochlorobenzene (DNCB). Langerhans cells and dermal MHCII^lowCD163⁺ cells were increased one month after oral treatment with CsA at 10 mg/kg/day. The contact dermatitis model in Göttingen Minipigs challenged by DNCB suggested migration of Langerhans cells and dermal dendritic cells as well as T cell recruitment into the skin. These data bring new information in skin immunotoxicology in Göttingen Minipigs and could contribute to a better understanding of the effects of new therapeutic drugs on the developing immune system.

Interactions of human microglia cells with Japanese encephalitis virus

Background

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.

Methods

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.

Results

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.

Conclusion

Our findings suggest that human microglia may be a source of neuronal infection and sustain JEV brain pathogenesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-016-0675-3) contains supplementary material, which is available to authorized users.

Partial Protection against Porcine Influenza A Virus by a Hemagglutinin-Expressing Virus Replicon Particle Vaccine in the Absence of Neutralizing Antibodies

This work was initiated by previous reports demonstrating that mismatched influenza A virus (IAV) vaccines can induce enhanced disease, probably mediated by antibodies. Our aim was, therefore, to investigate if a vaccine inducing opsonizing but not neutralizing antibodies against the hemagglutinin (HA) of a selected heterologous challenge virus would enhance disease or induce protective immune responses in the pig model. To this end, we immunized pigs with either whole inactivated virus (WIV)-vaccine or HA-expressing virus replicon particles (VRP) vaccine based on recombinant vesicular stomatitis virus (VSV). Both types of vaccines induced virus neutralizing and opsonizing antibodies against homologous virus as shown by a highly sensitive plasmacytoid dendritic cell-based opsonization assay. Opsonizing antibodies showed a broader reactivity against heterologous IAV compared with neutralizing antibodies. Pigs immunized with HA-recombinant VRP vaccine were partially protected from infection with a mismatched IAV, which was not neutralized but opsonized by the immune sera. The VRP vaccine reduced lung lesions, lung inflammatory cytokine responses, serum IFN-α responses, and viral loads in the airways. Only the VRP vaccine was able to prime IAV-specific IFNγ/TNFα dual secreting CD4(+) T cells detectable in the peripheral blood. In summary, this work demonstrates that with the virus pair selected, a WIV vaccine inducing opsonizing antibodies against HA which lack neutralizing activity, is neither protective nor does it induce enhanced disease in pigs. In contrast, VRP-expressing HA is efficacious vaccines in swine as they induced both potent antibodies and T-cell immunity resulting in a broader protective value.

Pro-inflammatory, Th1, Th2, Th17 cytokines and dendritic cells: a cross-sectional study in chronic periodontitis

There are a limited number of studies correlating the different stages of dendritic cells (DC) maturation with cytokines in individuals presented chronic periodontitis (CP). The aim of the study was to evaluate the correlation among the expression of IL-2, IL-10, IL-4, IL-6, IFN-, TNF-α, and IL-17A with the presence of DC and mild-moderate or advanced CP. Gingival samples were obtained from 24 individuals with CP and six samples of normal mucosa (NM) overlapping third molar for controls of the levels of cytokines. Periodontal examination was performed. Immunohistochemical staining was carried out, revealing CD1a+ immature, Fator XIIIa+ immature, and CD83+ mature DCs. The inflammatory infiltrate was counted, and the cytokines were measured by flow cytometry. Densities of DCs and inflammatory infiltrate, cytokines, subtypes of CP, and clinical periodontal parameters were correlated and compared. IL-6 expression was correlated positively with the increased numbers of CD1a+ immature DCs. Levels of IL-2, TNF-α, IFN-, IL-10, and IL-17A were increased when compared with NM. The percentage of sites with clinical attachment level (CAL)>3 were positively correlated with densities of inflammatory infiltrate and negatively correlated with densities of immature DCs. IL-6 can contribute to the increase of the immature DCs in the CP. Higher levels of IL-2, TNF-α, IFN-, IL-10, and IL-17A cytokines were observed in CP. Higher densities of inflammatory infiltrate as well as lower densities of immature DCs can result in a more severe degree of human CP.

Impact of genotype 1 and 2 of porcine reproductive and respiratory syndrome viruses on interferon-α responses by plasmacytoid dendritic cells

Porcine reproductive and respiratory syndrome (PRRS) virus (PRRSV) infections are characterized by prolonged viremia and viral shedding consistent with incomplete immunity. Type I interferons (IFN) are essential for mounting efficient antiviral innate and adaptive immune responses, but in a recent study, North American PRRSV genotype 2 isolates did not induce, or even strongly inhibited, IFN-α in plasmacytoid dendritic cells (pDC), representing “professional IFN-α-producing cells”. Since inhibition of IFN-α expression might initiate PRRSV pathogenesis, we further characterized PRRSV effects and host modifying factors on IFN-α responses of pDC. Surprisingly, a variety of type 1 and type 2 PRRSV directly stimulated IFN-α secretion by pDC. The effect did not require live virus and was mediated through the TLR7 pathway. Furthermore, both IFN-γ and IL-4 significantly enhanced the pDC production of IFN-α in response to PRRSV exposure. PRRSV inhibition of IFN-α responses from enriched pDC stimulated by CpG oligodeoxynucleotides was weak or absent. VR-2332, the prototype genotype 2 PRRSV, only suppressed the responses by 34%, and the highest level of suppression (51%) was induced by a Chinese highly pathogenic PRRSV isolate. Taken together, these findings demonstrate that pDC respond to PRRSV and suggest that suppressive activities on pDC, if any, are moderate and strain-dependent. Thus, pDC may be a source of systemic IFN-α responses reported in PRRSV-infected animals, further contributing to the puzzling immunopathogenesis of PRRS.