Transcription analysis on response of porcine alveolar macrophages to Haemophilus parasuis

Evaluation of immunoregulation and immunoprotective efficacy of Glaesserella parasuis histidine kinase QseC

QseC is a membrane sensor kinase that enables bacteria to perceive autoinducers -3, adrenaline, and norepinephrine to initiate downstream gene transcription. In this study, we found that the QseC protein of Glaesserella parasuis can serve as an effective antigen to activate the host's immune response. Therefore, we investigated the immunogenicity and host protective effect of this protein. ELISA and indirect immunofluorescence results showed that QseC protein can induce high titer levels of humoral immunity in mice and regularly generate specific serum antibodies. We used MTS reagents to detect lymphocyte proliferation levels and found that QseC protein can cause splenic lymphocyte proliferation with memory and specificity. Further immunological analysis of the spleen cell supernatant revealed significant upregulation of levels of IL-1β, IL-4 and IFN-γ in the QseC + adjuvant group. In the mouse challenge experiment, it was found that QseC + adjuvant can provide effective protection. The results of this study demonstrate that QseC protein provides effective protection in a mouse model and has the potential to serve as a candidate antigen for a novel subunit vaccine for further research.

Assessment of the Macrophage Scavenger Receptor CD163 in Mediating Glaesserella parasuis Infection of Host Cells

The macrophage CD163 surface glycoprotein is a member of the SRCR family class B, which has been identified as the key trigger in host-pathogen interactions, but its specific roles in sensing Glaesserella parasuis (G. parasuis) infection are largely unknown. Here, we investigated porcine CD163 in mediating the adhesion and immune response of G. parasuis using in vitro host-bacteria interaction models. CD163-overexpressing Chinese hamster ovary K1 cells (CHO-K1) showed obvious subcellular localization in the cytoplasm, especially in the cytomembrane. Although detection using scanning electron microscopy (SEM) confirmed the bacterial adhesion, there was no significant difference in the adhesion of G. parasuis to CHO-K1 cells between the presence and absence of CD163. In addition, similar results were observed in 3D4/21 cells. Meanwhile, bindings of G. parasuis to nine synthetic peptides, the bacterial binding motifs within SRCR domains of CD163, were weak based on a solid-phase adhesion assay and agglutination assay. Moreover, CD163 had no effect on the expression of G. parasuis-induced inflammatory cytokines (IL-6, INF-γ, IL-10, IL-4 and TGF-β) in CHO-K1 cells. In conclusion, these findings indicate that porcine CD163 plays a minor role in sensing G. parasuis infection.

Upregulation of TLR4-Dependent ATP Production Is Critical for Glaesserella parasuis LPS-Mediated Inflammation

Glaesserella parasuis (G. parasuis), an important pathogenic bacterium, cause Glässer's disease, and has resulted in tremendous economic losses to the global swine industry. G. parasuis infection causes typical acute systemic inflammation. However, the molecular details of how the host modulates the acute inflammatory response induced by G. parasuis are largely unknown. In this study, we found that G. parasuis LZ and LPS both enhanced the mortality of PAM cells, and at the same time, the level of ATP was enhanced. LPS treatment significantly increased the expressions of IL-1β, P2X7R, NLRP3, NF-κB, p-NF-κB, and GSDMD, leading to pyroptosis. Furthermore, these proteins' expression was enhanced following extracellular ATP further stimulation. When reduced the production of P2X7R, NF-κB-NLRP3-GSDMS inflammasome signaling pathway was inhibited, and the mortality of cells was reduced. MCC950 treatment repressed the formation of inflammasome and reduced mortality. Further exploration found that the knockdown of TLR4 significantly reduced ATP content and cell mortality, and inhibited the expression of p-NF-κB and NLRP3. These findings suggested upregulation of TLR4-dependent ATP production is critical for G. parasuis LPS-mediated inflammation, provided new insights into the molecular pathways underlying the inflammatory response induced by G. parasuis, and offered a fresh perspective on therapeutic strategies.

Francisella tularensis Glyceraldehyde-3-Phosphate Dehydrogenase Is Relocalized during Intracellular Infection and Reveals Effect on Cytokine Gene Expression and Signaling

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is known for its multifunctionality in several pathogenic bacteria. Our previously reported data suggest that the GAPDH homologue of Francisella tularensis, GapA, might also be involved in other processes beyond metabolism. In the present study, we explored GapA's potential implication in pathogenic processes at the host cell level. Using immunoelectron microscopy, we demonstrated the localization of this bacterial protein inside infected macrophages and its peripheral distribution in bacterial cells increasing with infection time. A quantitative proteomic approach based on stable isotope labeling of amino acids in cell culture (SILAC) combined with pull-down assay enabled the identification of several of GapA's potential interacting partners within the host cell proteome. Two of these partners were further confirmed by alternative methods. We also investigated the impact of gapA deletion on the transcription of selected cytokine genes and the activation of the main signaling pathways. Our results show that ∆gapA-induced transcription of genes encoding several cytokines whose expressions were not affected in cells infected with a fully virulent wild-type strain. That might be caused, at least in part, by the detected differences in ERK/MAPK signaling activation. The experimental observations together demonstrate that the F. tularensis GAPDH homologue is directly implicated in multiple host cellular processes and, thereby, that it participates in several molecular mechanisms of pathogenesis.

Baicalin Alleviate Apoptosis via PKC-MAPK Pathway in Porcine Peritoneal Mesothelial Cells Induced by Glaesserella parasuis

Glaesserella parasuis (GPS), a causative agent of Glässer’s disease, is thought to be the main fatal cause of peritonitis in swine, thus resulting in high mortality and morbidity and significant economic losses to the swine industry. However, the mechanisms of GPS infection-induced apoptosis and possible therapeutic pathway for GPS infection in peritonitis remain unclear. Baicalin has important biological functions during disease treatment, such as antiviral, bacterial inhibition, anti-apoptosis, and anti-inflammatory. However, whether baicalin has anti-apoptotic effects during the process of GPS infection in peritonitis is unclear. In the present study, the anti-apoptotic effect and mechanisms of baicalin in GPS infection-induced apoptosis were investigated in porcine peritoneal mesothelial cells (PPMC). The results showed that baicalin could inhibit the apoptosis rate occurrence of PPMC induced by GPS to various degrees and inhibit the expression of apoptosis-related genes and cleaved caspase-3. Meanwhile, baicalin significantly antagonized the expression of p-JNK, p-p38, and p-ERK induced by GPS in PPMC. These findings for the first time demonstrate that baicalin exerted the effect of antagonizing GPS induced apoptosis in PPMC by inhibiting the activation of the PKC-MAPK pathway and could be a therapeutic option in the management of GPS infection.

Transcriptome profile of spleen tissues from locally-adapted Kenyan pigs (Sus scrofa) experimentally infected with three varying doses of a highly virulent African swine fever virus genotype IX isolate: Ken12/busia.1 (ken-1033)

Background

African swine fever (ASF) is a lethal hemorrhagic disease affecting domestic pigs resulting in up to 100% mortality rates caused by the ASF virus (ASFV). The locally-adapted pigs in South-western Kenya have been reported to be resilient to disease and harsh climatic conditions and tolerate ASF; however, the mechanisms by which this tolerance is sustained remain largely unknown. We evaluated the gene expression patterns in spleen tissues of these locally-adapted pigs in response to varying infective doses of ASFV to elucidate the virus-host interaction dynamics.

Methods

Locally adapted pigs (n = 14) were experimentally infected with a high dose (1x10⁶HAD₅₀), medium dose (1x10⁴HAD₅₀), and low dose (1x10²HAD₅₀) of the highly virulent genotype IX ASFV Ken12/busia.1 (Ken-1033) isolate diluted in PBS and followed through the course of infection for 29 days. The in vivo pig host and ASFV pathogen gene expression in spleen tissues from 10 pigs (including three from each infective group and one uninfected control) were analyzed in a dual-RNASeq fashion. We compared gene expression between three varying doses in the host and pathogen by contrasting experiment groups against the naïve control.

Results

A total of 4954 differentially expressed genes (DEGs) were detected after ASFV Ken12/1 infection, including 3055, 1771, and 128 DEGs in the high, medium, and low doses, respectively. Gene ontology and KEGG pathway analysis showed that the DEGs were enriched for genes involved in the innate immune response, inflammatory response, autophagy, and apoptosis in lethal dose groups. The surviving low dose group suppressed genes in pathways of physiopathological importance. We found a strong association between severe ASF pathogenesis in the high and medium dose groups with upregulation of proinflammatory cytokines and immunomodulation of cytokine expression possibly induced by overproduction of prostaglandin E synthase (4-fold; p < 0.05) or through downregulation of expression of M1-activating receptors, signal transductors, and transcription factors. The host-pathogen interaction resulted in induction of expression of immune-suppressive cytokines (IL-27), inactivation of autophagy and apoptosis through up-regulation of NUPR1 [5.7-fold (high dose) and 5.1-fold (medium dose) [p < 0.05] and IL7R expression. We detected repression of genes involved in MHC class II antigen processing and presentation, such as cathepsins, SLA-DQB1, SLA-DOB, SLA-DMB, SLA-DRA, and SLA-DQA in the medium and high dose groups. Additionally, the host-pathogen interaction activated the CD8⁺ cytotoxicity and neutrophil machinery by increasing the expression of neutrophils/CD8⁺ T effector cell-recruiting chemokines (CCL2, CXCL2, CXCL10, CCL23, CCL4, CXCL8, and CXCL13) in the lethal high and medium dose groups. The recovered pigs infected with ASFV at a low dose significantly repressed the expression of CXCL10, averting induction of T lymphocyte apoptosis and FUNDC1 that suppressed neutrophilia.

Conclusions

We provide the first in vivo gene expression profile data from locally-adapted pigs from south-western Kenya following experimental infection with a highly virulent ASFV genotype IX isolate at varying doses that mimic acute and mild disease. Our study showed that the locally-adapted pigs induced the expression of genes associated with tolerance to infection and repression of genes involved in inflammation at varying levels depending upon the ASFV dose administered.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08754-8.

[Opportunities and risks of the use of genetic resistances to infectious diseases in pigs - an overview]

Demands for health, performance and welfare in pigs, as well as the desire for consumer protection and reduced antibiotic use, require optimal measures in advance of disease development. This includes, in principle, the use of genetically more resistant lines and breeding animals, whose existence has been proven for a wide range of pathogen-host interactions. In addition, attempts are being made to identify the gene variants responsible for disease resistance in order to force the selection of suitable populations, also using modern biotechnical technics. The present work is intended to provide an overview of the research status achieved in this context and to highlight opportunities and risks for the future.The evaluation of the international literature shows that genetic disease resistance exist in many areas of swine diseases. However, polygenic inheritance, lack of animal models and the influence of environmental factors during evaluation render their implementation in practical breeding programs demanding. This is where modern molecular genetic methods, such as Gene Editing, come into play. Both approaches possess their pros and cons, which are discussed in this paper. The most important infectious diseases in pigs, including general diseases and epizootics, diseases of the respiratory and digestive tract and diseases of the immune system are taken into account.

Toxoplasma gondii SAG1 targeting host cell S100A6 for parasite invasion and host immunity

Toxoplasma gondii surface antigen 1 (TgSAG1) is a surface protein of tachyzoites, which plays a crucial role in toxoplasma gondii infection and host cell immune regulation. However, how TgSAG1 regulates these processes remains elucidated. We utilized the biotin ligase -TurboID fusion with TgSAG1 to identify the host proteins interacting with TgSAG1, and identified that S100A6 was co-localized with TgSAG1 when T. gondii attached to the host cell. S100A6, either knocking down or blocking its functional epitopes resulted in inhibited parasites invasion. Meanwhile, S100A6 overexpression in host cells promoted T. gondii infection. We further verified that TgSAG1 could inhibit the interaction of host cell vimentin with S100A6 for cytoskeleton organization during T. gondii invasion. As an immunogen, TgSAG1 could promote the secretion of tumor necrosis factor alpha (TNF-α) through S100A6-Vimentin/PKCθ-NF-κB signaling pathway. In summary, our findings revealed a mechanism for how TgSAG1 functioned in parasitic invasion and host immune regulation.

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TgSAG1 interacts with host protein S100A6 then regulates T. gondii infection

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TgSAG1 could regulate binding vimentin with S100A6 during T. gondii infection

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TgSAG1 regulate TNFα secretion through S100A6-vimentin/PKCθ-NF-κB signaling pathway

Transcriptome profiling identifies immune response genes against porcine reproductive and respiratory syndrome virus and Haemophilus parasuis co-infection in the lungs of piglets

Background

Co-infections of the porcine reproductive and respiratory syndrome virus (PRRSV) and the Haemophilus parasuis (HPS) are severe in Chinese pigs, but the immune response genes against co-infected with 2 pathogens in the lungs have not been reported.

Objectives

To understand the effect of PRRSV and/or HPS infection on the genes expression associated with lung immune function.

Methods

The expression of the immune-related genes was analyzed using RNA-sequencing and bioinformatics. Differentially expressed genes (DEGs) were detected and identified by quantitative real-time polymerase chain reaction (qRT-PCR), immunohistochemistry (IHC) and western blotting assays.

Results

All experimental pigs showed clinical symptoms and lung lesions. RNA-seq analysis showed that 922 DEGs in co-challenged pigs were more than in the HPS group (709 DEGs) and the PRRSV group (676 DEGs). Eleven DEGs validated by qRT-PCR were consistent with the RNA sequencing results. Eleven common Kyoto Encyclopedia of Genes and Genomes pathways related to infection and immune were found in single-infected and co-challenged pigs, including autophagy, cytokine-cytokine receptor interaction, and antigen processing and presentation, involving different DEGs. A model of immune response to infection with PRRSV and HPS was predicted among the DEGs in the co-challenged pigs. Dual oxidase 1 (DUOX1) and interleukin-21 (IL21) were detected by IHC and western blot and showed significant differences between the co-challenged pigs and the controls.

Conclusions

These findings elucidated the transcriptome changes in the lungs after PRRSV and/or HPS infections, providing ideas for further study to inhibit ROS production and promote pulmonary fibrosis caused by co-challenging with PRRSV and HPS.

LncRNA-MEG3 Regulates the Inflammatory Responses and Apoptosis in Porcine Alveolar Macrophages Infected with Haemophilus parasuis Through Modulating the miR-210/TLR4 Axis

Haemophilus parasuis (H. parasuis, HPS) can elicit serious inflammatory responses and cause enormous economic loss to swine industry worldwide. However, the factors responsible for systemic infection and inflammatory responses of HPS have not yet been fully clarified. In this study, we found that lncRNA-MEG3 was significantly up-regulated in porcine alveolar macrophages (PAMs) infected with HPS. The gain- and loss-of-function analysis confirmed that lncRNA-MEG3 participated in the inflammatory responses and apoptosis in HPS-infected PAMs, which was assessed via several inflammatory cytokine genes (TNF-α, IL-1β, and IL-6) and apoptotic factors (Bcl-2, Bax, and C-caspase-3). Based on biotin-labeled RNA pull-down assay, we found that lncRNA-MEG3 bound with miR-210 in HPS-infected PAMs. Based on both overexpression and knockdown analysis of lncRNA-MEG3, our results indicated that lncRNA-MEG3 promoted the expression of TLR4 in HPS-infected PAMs. Using dual-luciferase reporter assays, we showed that lncRNA-MEG3 positively regulated the expression of TLR4 gene in HPS-infected PAMs through miR-210 pathway. Taken together, our results indicated that lncRNA-MEG3 participated in the inflammatory responses and apoptosis in HPS-infected PAMs through modulating the miR-210/TLR4 axis. The results from this investigation provided significant information for a novel target to control HPS infection in swine.

Glaesserella parasuis induces inflammatory response in 3D4/21 cells through activation of NLRP3 inflammasome signaling pathway via ROS

Glaesserella parasuis (G. parasuis) is an important pathogenic bacterium that can cause Glässer's disease, and it has resulted in tremendous economic losses to the global swine industry. The intensive pulmonary inflammatory response caused by G. parasuis infection is the main cause of lung injury and death in pigs. However, the exact mechanism by which it causes severe pulmonary inflammation is not fully understood yet. In this study, severe pneumonia was observed in piglets infected with G. parasuis; and an infection cell model was established using porcine alveolar macrophages cell line 3D4/21, which was determined to be susceptible to G. parasuis infection in vitro. G. parasuis infection of 3D4/21 cells induced upregulation of proinflammatory cytokines TNF-α, IL-1β, IL-18 and production of intracellular reactive oxygen species (ROS). The expression of IL-1β related to activation of the NLRP3 inflammasome signaling pathway, which had not been shown before in G. parasuis infection. Furthermore, it was first found that release of intracellular ROS, which was mediated by NADPH oxidase in 3D4/21 cells, was found crucial for the activation of the NLRP3 signaling pathway and promoted the expression of proinflammatory cytokines, such as TNF-α and IL-1. In general, this study explored the specific mechanism of severe pulmonary inflammation caused by G. parasuis infection, and provides a foundation for further elucidating the pathogenic mechanism of G. parasuis.

Highly multiplexed quantitative PCR-based platform for evaluation of chicken immune responses

To address the need for sensitive high-throughput assays to analyse avian innate and adaptive immune responses, we developed and validated a highly multiplexed qPCR 96.96 Fluidigm Dynamic Array to analyse the transcription of chicken immune-related genes. This microfluidic system permits the simultaneous analysis of expression of 96 transcripts in 96 samples in 6 nanolitre reactions and the 9,216 reactions are ready for interpretation immediately. A panel of 89 genes was selected from an RNA-seq analysis of the transcriptional response of chicken macrophages, dendritic cells and heterophils to agonists of innate immunity and from published transcriptome data. Assays were confirmed to be highly specific by amplicon sequencing and melting curve analysis and the reverse transcription and preamplification steps were optimised. The array was applied to RNA of various tissues from a commercial line of broiler chickens housed at two different levels of biosecurity. Gut-associated lymphoid tissues, bursa, spleen and peripheral blood leukocytes were isolated and transcript levels for immune-related genes were defined. The results identified blood cells as a potentially reliable indicator of immune responses among all the tissues tested with the highest number of genes significantly differentially transcribed between birds housed under varying biosecurity levels. Conventional qPCR analysis of three differentially transcribed genes confirmed the results from the multiplex qPCR array. A highly multiplexed qPCR-based platform for evaluation of chicken immune responses has been optimised and validated using samples from commercial chickens. Apart from applications in selective breeding programmes, the array could be used to analyse the complex interplay between the avian immune system and pathogens by including pathogen-specific probes, to screen vaccine responses, and as a predictive tool for immune robustness.

Haemophilus parasuis infection in 3D4/21 cells induces autophagy through the AMPK pathway

Haemophilus parasuis (H. parasuis) is a common commensal in the upper respiratory tract of pigs, but causes Glässer's disease in stress conditions. To date, many studies focused on the immune evasion and virulence of H. parasuis; very few have focused on the role autophagy played in H. parasuis infection, particularly in porcine alveolar macrophages (PAMs). In this study, a PAM cell line, 3D4/21 cells were used to study the role of autophagy in H. parasuis infection. 3D4/21 cells tandemly expressing GFP, mCherry, and LC3 were infected with H. parasuis serovar 5 (Hps5). Western blot analysis and confocal and transmission electron microscopy showed that H. parasuis infection effectively induces autophagy. Using Hps strains of varying virulence (Hps4, Hps5, and Hps7) and UV-inactivated Hps5, we demonstrated that autophagy is associated with the internalisation of living virulent strains into cells. In 3D4/21 cells pretreated with rapamycin and 3-MA then infected by Hps4, Hps5, and Hps7, we demonstrated that autophagy affects invasion of H. parasuis in cells. AMPK signal results showed that Hps5 infection can upregulate the phosphorylation level of AMPK, which is consistent with the autophagy development. 3D4/21 cells pretreated with AICAR or Compound C then infected by Hps5 revealed that the autophagy induced by Hps5 infection is associated with the AMPK pathway. Our study contributes to the theoretical basis for the study of H. parasuis pathogenesis and development of novel drugs target for prevention Glässer's disease.

Coinfection with Haemophilus parasuis serovar 4 increases the virulence of porcine circovirus type 2 in piglets

Background

Postweaning multisystemic wasting syndrome (PMWS) is an emerging disease in swine. Pigs with PMWS are often infected with a variety of other pathogens, including bacteria, viruses and mycoplasm, in addition to porcine circovirus type 2 (PCV2). PCV2 and Haemophilus parasuis serovar 4 (HPS4) coinfection remain epidemic in China.

Methods

Here we report construction of a three-week-old naturally farrowed, colostrum-deprived (NFCD) piglet’s infection model and demonstrate that PCV2-infected piglets with the HPS4 coinfection increased the virulence of PCV2 and these pathogens interact acquired PMWS.

Results

All the single infected piglets were transiently bacteremic or viremic. All the PCV2/HPS4 coinfected piglets developed PMWS, characterized by dyspnea, anorexia, prostration and lose weight severely. Co-infection with PCV2 and HPS4 resulted in an increased amount of virus in serum and tissues, presented a slower generation and lower levels of antibodies against PCV2. Co-infection with PCV2 and HPS4 resulted in further reductions in total and differential peripheral blood leukocyte counts. Meantime, PCV2/ HPS4 coinfection potentiated the severity of lung and lymphoid lesions by PCV2-associated, increased the virulence of PCV2-antigen and enhanced the incidence of PMWS in piglets.

Conclusion

Co-infection with PCV2 and HPS4 induce the exacerbation of system injuries and enhance the pathogenicity of PCV2 in piglets.

Transcription analysis of the responses of porcine heart to Erysipelothrix rhusiopathiae

Erysipelothrix rhusiopathiae (E. rhusiopathiae) is the causative agent of swine erysipelas. This microbe has caused great economic losses in China and in other countries. In this study, high-throughput cDNA microarray assays were employed to evaluate the host responses of porcine heart to E. rhusiopathiae and to gain additional insights into its pathogenesis. A total of 394 DE transcripts were detected in the active virulent E. rhusiopathiae infection group compared with the PBS group at 4 days post-infection. Moreover, 262 transcripts were upregulated and 132 transcripts were downregulated. Differentially expressed genes were involved in many vital functional classes, including inflammatory and immune responses, signal transduction, apoptosis, transport, protein phosphorylation and dephosphorylation, metabolic processes, chemotaxis, cell adhesion, and innate immune responses. Pathway analysis demonstrated that the most significant pathways were Chemokine signaling pathway, NF-kappa B signaling pathway, TLR pathway, CAMs, systemic lupus erythematosus, chemokine signaling pathway, Cytokine–cytokine receptor interaction, PI3K-Akt signaling pathway, Phagosome, HTLV-I infection, Measles, Rheumatoid arthritis and natural-killer-cell-mediated cytotoxicity. The reliability of our microarray data was verified by performing quantitative real-time PCR. This study is the first to document the response of piglet heart to E. rhusiopathiae infection. The observed gene expression profile could help screen potential host agents that can reduce the prevalence of E. rhusiopathiae. The profile might also provide insights into the underlying pathological changes that occur in pigs infected with E. rhusiopathiae.

Transcriptomic analysis of porcine PBMCs in response to FMDV infection

Foot-and-mouth disease (FMD) is a significant zoonotic infectious disease. It has an important economic impact throughout the world. As well, it is a considerable threat to food security. At present, the molecular mechanism of FMDV infection is not clear to a large extent. Innate immune response is the first line of defense against infectious diseases. The systematic analysis of the host immune response to infection has an important role in understanding the pathogenesis of infection. However, there are few reports about effect of immune regulation on virus replication in the interaction of virus and host cellular. High-throughput RNA-seq technology as a powerful and efficient means for transcript analysis provides a new insight into FMDV study. In this study, RNA extracted from pig PBMCs infected with O subtype FMDV at 4 dpi. A total of 29942658 and 31452917 Illumina read pairs were obtained from the non-infected (NI) group and infected (I) group, respectively. The clean bases for all samples are 3.61G (NI group) and 3.79G (I group), respectively. The clean reads of the NI and I group that mapped to pig genome data were 47195073 (81.82%) and 46556714 (76.85%), respectively. Most of the clean reads were distributed in the exon region, followed by intron region and intergenic region. Differently expressed (DE) genes were analyzed using edgeR software. 451 genes were differentially expressed between the infected and the non-infected groups. According to the comparison analysis, more genes were down-regulated in the non-infected samples than in those infected with FMDV.66 out of 451 genes were down-regulated, 385 out of 451 genes were up-regulated following FMDV infection. For function classification and pathway analysis, among 17741 assembled unigenes, there are 349 genes which are different genes of GO notes. Moreover, 49 genes were down-regulated, 300 genes were up-regulated associate with GO term. 1621 were successfully annotated by GO assignments, belonging to one or more of the three categories: biological process, cellular component, and molecular function. According to KEGG analysis,the main pathway was represented including protein processing in endoplasmic reticulum, phagosome, cell cycle and cytokine-cytokine receptor interaction. Some key DE genes related to immune process and signaling pathways were analyzed and quantified by RT-PCR. This is the first systematical transcriptome analysis of pig PBMCs infected by FMDV. These findings will help us better understand the host Cell-FMDV interaction and its relationship to pathogenesis, as well as contribute to the prevention and control of FMDV.

Proteomic insight into the effects of the Salmonella ubiquitin ligase SlrP on host cells

The virulence of the human and animal pathogen Salmonella enterica serovar Typhimurium is dependent on two type III secretion systems. These systems translocate proteins called effectors into eukaryotic host cells. SlrP is a Salmonella type III secretion effector with ubiquitin ligase activity. Here, we used two complementary proteomic approaches, two-dimensional gel electrophoresis and iTRAQ (isobaric tags for relative and absolute quantification) to study the consequences of the presence of SlrP in human epithelial cells. We identified 37 proteins that were differentially expressed in HeLa cells expressing slrP compared to control cells. Microarray analysis revealed that more than a half of differentially expressed proteins did not show changes in the transcriptome, suggesting post-transcriptional regulation. A gene ontology overrepresentation test carried out on the differentially expressed proteins revealed enrichment of ontology terms related to several types of junctions mediating adhesion in epithelial cells. Consistently, slrP-transfected cells showed defects in migration and adhesion. Our results suggest that the modification of cell-cell interaction ability of the host could be one of the final consequences of the action of SlrP during an infection.

Mycoplasma bovis-derived lipid-associated membrane proteins activate IL-1β production through the NF-κB pathway via toll-like receptor 2 and MyD88

Mycoplasma bovis causes pneumonia, otitis media, and arthritis in young calves, resulting in economic losses to the cattle industry worldwide. M. bovis pathogenesis results in part from excessive immune responses. Lipid-associated membrane proteins (LAMPs) can potently induce host innate immunity. However, interactions between M. bovis-derived LAMPs and Toll-like receptors (TLRs), or signaling pathways eliciting active inflammation and NF-κB activation, are incompletely understood. Here, we found that IL-1β expression was induced in embryonic bovine lung (EBL) cells stimulated with M. bovis-derived LAMPs. Subcellular-localization analysis revealed nuclear p65 translocation following EBL cell stimulation with M. bovis-derived LAMPs. An NF-κB inhibitor reversed M. bovis-derived LAMP-induced IL-1β expression. TLR2 and myeloid differentiation primary response gene 88 (MyD88) overexpression increased LAMP-dependent IL-1β induction. TLR2-neutralizing antibodies reduced IL-1β expression during LAMP stimulation. LAMPs also inhibited IL-1β expression following overexpression of a dominant-negative MyD88 protein. These results suggested that M. bovis-derived LAMPs activate IL-1β production through the NF-κB pathway via TLR2 and MyD88.

Haemophilus parasuis: infection, immunity and enrofloxacin

Haemophilus parasuis is an early colonizer of the porcine upper respiratory tract and is the etiological agent of Glasser’s disease. The factors responsible for H. parasuis colonization and systemic infection are not yet well understood, while prevention and control of Glasser’s disease continues to be challenging. Recent studies on innate immunity to H. parasuis have demonstrated that porcine alveolar macrophages (PAMs) are able to differentially up-regulate several genes related to inflammation and phagocytosis, and several pro-inflammatory cytokines are produced by porcine cells upon exposure to H. parasuis. The susceptibility of H. parasuis strains to phagocytosis by PAMs and the bactericidal effect of complement are influenced by the virulent phenotype of the strains. While non-virulent strains are susceptible to phagocytosis and complement, virulent strains are resistant to both. However, in the presence of specific antibodies against H. parasuis, virulent strains become susceptible to phagocytosis. More information is still needed, though, in order to better understand the host immune responses to H. parasuis. Antimicrobials are commonly used in the swine industry to help treat and control Glasser’s disease. Some of the common antimicrobials have been shown to reduce colonization by H. parasuis, which may have implications for disease dynamics, development of effective immune responses and immunomodulation. Here, we provide the current state of research on innate and adaptive immune responses to H. parasuis and discuss the potential effect of enrofloxacin on the development of a protective immune response against H. parasuis infection.

Haemophilus parasuis induces activation of NF-κB and MAP kinase signaling pathways mediated by toll-like receptors

Glässer's disease in pigs caused by Haemophilus parasuis is characterized by a severe membrane inflammation. In our previous study, we have identified activation of the transcription factor NF-κB after H. parasuis infection of porcine epithelial cells. In this study, we found that H. parasuis infection also contributed to the activation of p38/JNK MAPK pathway predominantly linked to inflammation, but not the ERK MAPK pathway associated with growth, differentiation and development. Inhibition of NF-κB, p38 and JNK but not ERK activity significantly reduced IL-8 and CCL4 expression by H. parasuis. We also found TLR1, TLR2, TLR4 and TLR6 were required for NF-κB, p38 and JNK MAPK activation. Furthermore, MyD88 and TRIF signaling cascades were essential for H. parasuis-induced NF-κB activation. These results provided new insights into the molecular pathways underlying the inflammatory response induced by H. parasuis.

Molecular characterization of the porcine S100A6 gene and analysis of its expression in pigs infected with highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV)

Our previous microarray study revealed that S100A6 was significantly upregulated in porcine alveolar macrophages (PAMs) infected with highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV). In the present study, we cloned both cDNA and genomic DNA sequences of the gene. Transient transfection indicated that the porcine S100A6 protein was located in the nucleus and cytoplasm. Reverse transcription polymerase chain reaction (RT-PCR) revealed that the porcine S100A6 gene was highly expressed in the kidney and subcutaneous fat. Polyinosinic-polycytidylic acid [poly (I:C)] induced porcine S100A6 gene expression in PK-15 cells. Quantitative real-time PCR (Q-PCR) analysis further showed that the porcine S100A6 gene was upregulated in different cells and tissues of Tongcheng pigs infected with HP-PRRSV. Chromosome walking obtained the porcine S100A6 promoter region and then luciferase reporter assays confirmed its regulatory activities. We observed a putative NF-κB binding site in the core promoter region, which may explain the upregulation of porcine S100A6 in response to PRRSV. Transfection of NF-κB (p65 subunit) intensely induced the promoter activity of the porcine S100A6 gene, while an NF-κB inhibitor, pyrrolidine dithiocarbamate (PDTC), inhibited this activity. Furthermore, compared to its wild type, the promoter activity was significantly reduced when it contained a mutant NF-κB binding site. All these results provide a solid foundation to further investigate how S100A6 is involved in PRRSV infection.

Differential gene expression profiling of Actinobacillus pleuropneumoniae during induction of primary alveolar macrophage apoptosis in piglets

Actinobacillus pleuropneumoniae (A. pleuropneumoniae) is the causative agent of porcine pleuropneumonia, a disease that causes serious problems for the swine industry. Successful infection by this bacterium requires breaking the first line of defence in the lungs, the primary alveolar macrophages (PAMs). Therefore, exploring A. pleuropneumoniae-PAM interactions will provide vital groundwork for the scientific control of this infectious disease, which has been little studied up to now. In this work, PAMs were isolated from piglets and co-incubated with A. pleuropneumoniae serovar 5b strain L20 in vitro, and their interaction, PAM cell death, and differential gene expression of A. pleuropneumoniae in response to PAM cell death were observed and analysed using confocal microscopy, electron microscopy, RT-PCR, Western blot, flow cytometry and the use of a gene expression profile chip. A. pleuropneumoniae quickly adhered to and invaded PAMs, inducing apoptosis, which was confirmed using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The highest percentage of apoptosis in cells was confirmed using flow cytometry when the cells were infected at a multiplicity of infection (MOI) of 10 and incubated for 5 h, with higher expression of activated caspase-3 as measured by Western blot. Using microarray gene chips with 2868 probes containing nearly all of the genomic sequence of A. pleuropneumoniae serotype 5b strain L20, a total of 185 bacterial genes were found to be differentially expressed (including 92 up-regulated and 93 down-regulated genes) and involved in the process of apoptosis, as compared with the expression of control bacteria cultured without PAMs in BHI medium (mean expression ratios >1.5-fold, p < 0.05). The up-regulated genes are involved in energy metabolism, gene transcription and translation, virulence related gene such as LPS, Trimeric Autotransporter Adhesin, RTX and similar genes. The down-regulated genes are involved in amino acid, cofactor, and vitamin metabolism, and also include ABC transporters. These data demonstrate that A. pleuropneumoniae induces apoptosis of PAMs and undergoes complex changes in gene transcription, including expression changes in known and potential virulence factors. Some potentially novel virulence targets have been identified, suggesting new strategies for the development of vaccines and medicines for both preventive and clinical use.

Current transcriptomics in pig immunity research

Swine performance in the face of disease challenge is becoming progressively more important. To improve the pig’s robustness and resilience against pathogens through selection, a better understanding of the genetic and epigenetic factors in the immune response is required. This review highlights results from the most recent transcriptome research, and the meta-analyses performed, in the context of pig immunity. A technological overview is given including wholegenome microarrays, immune-specific arrays, small-scale high-throughput expression methods, high-density tiling arrays, and next generation sequencing (NGS). Although whole genome microarray techniques will remain complementary to NGS for some time in domestic species, research will transition to sequencing-based methods due to cost-effectiveness and the extra information that such methods provide. Furthermore, upcoming high-throughput epigenomic studies, which will add greatly to our knowledge concerning the impact of epigenetic modifications on pig immune response, are listed in this review. With emphasis on the insights obtained from transcriptomic analyses for porcine immunity, we also discuss the experimental design in pig immunity research and the value of the newly published porcine genome assembly in using the pig as a model for human immune response. We conclude by discussing the importance of establishing community standards to maximize the possibility of integrative computational analyses, such as was clearly beneficial for the human ENCODE project.

Transcription analysis on response of porcine alveolar macrophages to co-infection of the highly pathogenic porcine reproductive and respiratory syndrome virus and Mycoplasma hyopneumoniae

Porcine respiratory disease complex (PRDC) is of great concern economically, for swine producers worldwide. Co-infections with porcine reproductive and respiratory syndrome virus (PRRSV) and Mycoplasma hyopneumoniae (Mhp) are considered the major causative agents of PRDC, and responsible for mass mortality in pigs. Nevertheless, the molecular mechanisms underlying the host factors involved in pathogenesis and persistent infection have not been clearly established because of a lack of information regarding host responses following co-infection. In the current study, high throughput cDNA microarray assays were employed to evaluate host responses of porcine alveolar macrophages (PAM) to co-infection with highly pathogenic PRRSV (HP-PRRSV) and Mhp. A total of 2152 and 1760 genes were identified as being differentially expressed between the control group and PRRSV+Mhp co-infected group at 6 and 15 h post infection, respectively. The DE genes were involved in many vital functional classes, including inflammatory response, immune response, apoptosis, defense response, signal transduction. The pathway analysis demonstrated that the most significant pathways were associated with chemokine signaling pathway, cytokine, TLR, RLR and NLR signaling pathways and Jak-STAT signaling pathway. STRING analysis demonstrated that IL-1β is an integral gene in co-infections with PRRSV and Mhp. The present study is the first to document the response of PAMs to co-infection with HP-PRRSV and Mhp. The observed gene expression profile could help with the screening of potential host agents for reducing the prevalence of co-infections, and to further develop our understanding of the molecular pathogenesis associated with PRRSV and Mhp co-infection in pigs.

Transcription analysis of the porcine alveolar macrophage response to Mycoplasma hyopneumoniae

Mycoplasma hyopneumoniae is considered the major causative agent of porcine respiratory disease complex, occurs worldwide and causes major economic losses to the pig industry. To gain more insights into the pathogenesis of this organism, the high throughput cDNA microarray assays were employed to evaluate host responses of porcine alveolar macrophages to M. hyopneumoniae infection. A total of 1033 and 1235 differentially expressed genes were identified in porcine alveolar macrophages in responses to exposure to M. hyopneumoniae at 6 and 15 hours post infection, respectively. The differentially expressed genes were involved in many vital functional classes, including inflammatory response, immune response, apoptosis, cell adhesion, defense response, signal transduction, protein folding, protein ubiquitination and so on. The pathway analysis demonstrated that the most significant pathways were the chemokine signaling pathway, Toll-like receptor signaling pathway, RIG-I-like receptor signaling pathway, nucleotide-binding oligomerization domains (Nod)-like receptor signaling pathway and apoptosis signaling pathway. The reliability of the data obtained from the microarray was verified by performing quantitative real-time PCR. The expression kinetics of chemokines was further analyzed. The present study is the first to document the response of porcine alveolar macrophages to M. hyopneumoniae infection. The data further developed our understanding of the molecular pathogenesis of M. hyopneumoniae.

Porcine coronin 1A contributes to nuclear factor-kappa B (NF-κB) inactivation during Haemophilus parasuis infection

Haemophilus parasuis (H.parasuis) is the etiological agent of porcine polyserositis and arthritis (Glässer's disease) characterized by fibrinous polyserositis, meningitis and polyarthritis, causing severe economic losses to the swine industry. Currently, the molecular basis of this infection is largely unkonwn. Coronin 1A (Coro1A) plays important roles in host against bacterial infection, yet little is known about porcine Coro1A. In this study, we investigated the molecular characterization of porcine Coro1A, revealing that porcine Coro1A was widely expressed in different tissues. Coro1A could be induced by lipopolysaccharide (LPS), polyinosinic acid-polycytidylic acid [poly (I:C)] and H.parasuis in porcine kidney-15 (PK-15) cells. Functional analyses revealed that porcine Coro1A suppressed the NF-κB activation during H.parasuis infection by inhibiting the degradation of IκBα and nuclear translocation of p65. Overexpression of porcine Coro1A inhibited the transcription of NF-κB-mediated downstream genes [Interleukin-6 (IL-6), Interleukin-8 (IL-8) and COX-2] through down-regulation of NF-κB. The results indicated that porcine Coro1A is an important immunity related gene that helps to inhibit NF-kB activation during H. parasuis infection.

Changes in macrophage phenotype after infection of pigs with Haemophilus parasuis strains with different levels of virulence

Haemophilus parasuis is a colonizer of healthy piglets and the etiological agent of Glässer's disease. Differences in virulence among strains of H. parasuis have been widely observed. In order to explore the host-pathogen interaction, snatch-farrowed colostrum-deprived piglets were intranasally infected with 4 strains of H. parasuis: reference virulent strain Nagasaki, reference nonvirulent strain SW114, field strain IT29205 (from a systemic lesion and virulent in a previous challenge), and field strain F9 (from the nasal cavity of a healthy piglet). At different times after infection, two animals of each group were euthanized and alveolar macrophages were analyzed for the expression of CD163, CD172a, SLA I (swine histocompatibility leukocyte antigen I), SLA II, sialoadhesin (or CD169), and CD14. At 1 day postinfection (dpi), virulent strains induced reduced expression of CD163, SLA II, and CD172a on the surfaces of the macrophages, while nonvirulent strains induced increased expression of CD163, both compared to noninfected controls. At 2 dpi, the pattern switched into a strong expression of CD172a, CD163, and sialoadhesin by the virulent strains, which was followed by a steep increase in interleukin 8 (IL-8) and soluble CD163 in serum at 3 to 4 dpi. The early increase in surface expression of CD163 induced by nonvirulent strains went along with higher levels of IL-8 in serum than those induced by virulent strains in the first 2 days of infection. Alpha interferon (IFN-α) induction was observed only in animals infected with nonvirulent strains. Overall, these results are compatible with a delay in macrophage activation by virulent strains, which may be critical for disease production.

Systems infection biology: a compartmentalized immune network of pig spleen challenged with Haemophilus parasuis

BACKGROUND

Network biology (systems biology) approaches are useful tools for elucidating the host infection processes that often accompany complex immune networks. Although many studies have recently focused on Haemophilus parasuis, a model of Gram-negative bacterium, little attention has been paid to the host's immune response to infection. In this article, we use network biology to investigate infection with Haemophilus parasuis in an in vivo pig model.

RESULTS

By targeting the spleen immunogenome, we established an expression signature indicative of H. parasuis infection using a PCA/GSEA combined method. We reconstructed the immune network and estimated the network topology parameters that characterize the immunogene expressions in response to H. parasuis infection. The results showed that the immune network of H. parasuis infection is compartmentalized (not globally linked). Statistical analysis revealed that the reconstructed network is scale-free but not small-world. Based on the quantitative topological prioritization, we inferred that the C1R-centered clique might play a vital role in responding to H. parasuis infection.

CONCLUSIONS

Here, we provide the first report of reconstruction of the immune network in H. parasuis-infected porcine spleen. The distinguishing feature of our work is the focus on utilizing the immunogenome for a network biology-oriented analysis. Our findings complement and extend the frontiers of knowledge of host infection biology for H. parasuis and also provide a new clue for systems infection biology of Gram-negative bacilli in mammals.

Immunogenomics for identification of disease resistance genes in pigs: a review focusing on Gram-negative bacilli

Over the past years, infectious disease has caused enormous economic loss in pig industry. Among the pathogens, gram negative bacteria not only cause inflammation, but also cause different diseases and make the pigs more susceptible to virus infection. Vaccination, medication and elimination of sick pigs are major strategies of controlling disease. Genetic methods, such as selection of disease resistance in the pig, have not been widely used. Recently, the completion of the porcine whole genome sequencing has provided powerful tools to identify the genome regions that harboring genes controlling disease or immunity. Immunogenomics, which combines DNA variations, transcriptome, immune response, and QTL mapping data to illustrate the interactions between pathogen and host immune system, will be an effective genomics tool for identification of disease resistance genes in pigs. These genes will be potential targets for disease resistance in breeding programs. This paper reviewed the progress of disease resistance study in the pig focusing on Gram-negative bacilli. Major porcine Gram-negative bacilli and diseases, suggested candidate genes/pathways against porcine Gram-negative bacilli, and distributions of QTLs for immune capacity on pig chromosomes were summarized. Some tools for immunogenomics research were described. We conclude that integration of sequencing, whole genome associations, functional genomics studies, and immune response information is necessary to illustrate molecular mechanisms and key genes in disease resistance.