Pig Lung Immune Cytokine Response to the Swine Influenza Virus and the Actinobacillus Pleuropneumoniae Infection

Effect of Feeding Saccharomyces cerevisiae boulardii CNCM I-1079 to Sows and Piglets on Piglets' Immune Response after Vaccination against Actinobacillus pleuropneumoniae

The aim of this study was to assess the effect that feeding Saccharomyces cerevisiae boulardii CNCM I-1079 (LSB) to lactating sows and their progeny has on inflammatory response and mucosal immunity after vaccination against Actinobacillus pleuropneumoniae. Sixty-seven Danbred sows were allotted into two treatments when they entered the farrowing room seven days before the expected farrowing date: control (CON: lactation diet) and LSB (CON + 12 × 109 colony forming units (CFU)/d until weaning). At weaning, piglets were equally allotted into two experimental diets according to sow diet: control (CON: 2-phase post-weaning diets) and LSB (CON + 2 × 109 CFU/kg and 1 × 109 CFU/kg in phases 1 and 2, respectively). The piglets were vaccinated at days 26 and 49 post-weaning. Growth performance and number of IgA producing cells and cytokine’s gene expression in lung, lymph node, and intestine samples at day 70 post-weaning were assessed and analyzed in SPSS Statistics 26: performance with a general linear model with sex, room, sow diet, piglet diet, and their interactions as main effects, and immunity with a Kruskal−Wallis test for k unrelated samples. Piglets from LSB-fed sows displayed a higher average daily gain (ADG; p < 0.01) and a heavier body weight (BW; p < 0.05) during lactation, tended (p < 0.1) to be heavier at day 49, and to have a higher ADG between days 26 and 49; had fewer number of IgA producing cells in the lymph node (p < 0.05); and all the cytokines studied were significantly under-regulated (p < 0.05) in the lung. It is concluded that feeding Saccharomyces cerevisiae boulardii CNCM I-1079 to sows improved piglet performance during lactation and showed a clear reduction in the inflammatory status of the lungs after vaccination against A. pleuropneumoniae, suggesting that there was a maternal imprinting effect on mucosal protection and a cross-talk between the gut microbiota and the lung.

Cytokine expression by CD163+ monocytes in healthy and Actinobacillus pleuropneumoniae-infected pigs

Distinct monocyte subpopulations have been previously described in healthy pigs and pigs experimentally infected with Actinobacillus pleuropneumoniae (APP). The CD163+ subpopulation of bone marrow (BM), peripheral blood (PB) and lung monocytes was found to play an important role in the inflammatory process. The inflammation is accompanied by elevation of inflammatory cytokines. The aim of the study was to evaluate the contribution of CD163+ monocytes and macrophages to cytokine production during APP-induced lung inflammation. Cytokine production was assessed by flow cytometry (FC) and quantitative PCR (qPCR) in CD163+ monocytes and by qPCR, immunohistochemistry/fluorescence in lungs and tracheobronchial lymph nodes (TBLN). Despite the systemic inflammatory response after APP infection, BM and PB CD163+ monocytes did not express elevated levels of a wide range of cytokines compared to control pigs. In contrast, significant amounts of IL-1β, IL-6, IL-8 and TNF-α were produced in lung lesions and IL-1β in the TBLN. At the protein level, TNF-α was expressed by both CD163+ monocytes and macrophages in lung lesions, whereas IL-1β, IL-6 and IL-8 expression was found only in CD163+ monocytes; no CD163+ macrophages were found to produce these cytokines. Furthermore, the quantification of CD163+ monocytes expressing the two cytokines IL-1β and IL-8 that were most elevated was performed. In lung lesions, 36.5% IL-1β positive CD163+ monocytes but only 18.3% IL-8 positive CD163+ monocytes were found. In conclusion, PB and BM CD163+ monocytes do not appear to contribute to the elevated cytokine levels in plasma. On the other hand, CD163+ monocytes contribute to inflammatory cytokine expression, especially IL-1β at the site of inflammation during the inflammatory process.

MALDI MSI Reveals the Spatial Distribution of Protein Markers in Tracheobronchial Lymph Nodes and Lung of Pigs after Respiratory Infection

Respiratory infections are a real threat for humans, and therefore the pig model is of interest for studies. As one of a case for studies, Actinobacillus pleuropneumoniae (APP) caused infections and still worries many pig breeders around the world. To better understand the influence of pathogenic effect of APP on a respiratory system-lungs and tracheobronchial lymph nodes (TBLN), we aimed to employ matrix-assisted laser desorption/ionization time-of-flight mass spectrometry imaging (MALDI-TOF MSI). In this study, six pigs were intranasally infected by APP and two were used as non-infected control, and 48 cryosections have been obtained. MALDI-TOF MSI and immunohistochemistry (IHC) were used to study spatial distribution of infectious markers, especially interleukins, in cryosections of porcine tissues of lungs (necrotic area, marginal zone) and tracheobronchial lymph nodes (TBLN) from pigs infected by APP. CD163, interleukin 1β (IL‑1β) and a protegrin-4 precursor were successfully detected based on their tryptic fragments. CD163 and IL‑1β were confirmed also by IHC. The protegrin-4 precursor was identified by MALDI-TOF/TOF directly on the tissue cryosections. CD163, IL‑1β and protegrin‑4 precursor were all significantly (p < 0.001) more expressed in necrotic areas of lungs infected by APP than in marginal zone, TBLN and in control lungs.

Effects of respiratory disease on Kele piglets lung microbiome, assessed through 16S rRNA sequencing

Background and Aim

Due to the incomplete development of the immune system in immature piglets, the respiratory tract is susceptible to invasion by numerous pathogens that cause a range of potential respiratory diseases. However, few studies have reported the changes in pig lung microorganisms during respiratory infection. Therefore, we aimed to explore the differences in lung environmental microorganisms between healthy piglets and piglets with respiratory diseases.

Materials and Methods

Histopathological changes in lung sections were observed in both diseased and healthy pigs. Changes in the composition and abundance of microbiomes in alveolar lavage fluid from eleven 4-week-old Chinese Kele piglets (three clinically healthy and eight diseased) were studied by IonS5™ XL sequencing of the bacterial16S rRNA genes.

Results

Histopathological sections showed that diseased pigs displayed more lung lesions than healthy pigs. Diseased piglets harbored lower bacterial operational taxonomic units, α-diversity, and bacterial community complexity in comparison to healthy piglets. Taxonomic composition analysis showed that in the diseased piglets, the majority of flora was composed of Ureaplasma, Mycoplasma, and Actinobacillus; while Actinobacillus, Sphingomonas, and Stenotrophomonas were dominant in the control group. The abundance of Ureaplasma was significantly higher in ill piglets (p<0.05), and the phylogenetic tree indicated that Ureaplasma was clustered in Ureaplasma diversum, a conditional pathogen that has the potential to affect the swine respiratory system.

Conclusion

The results of this study show that the microbial species and structure of piglets' lungs were changed during respiratory tract infection. The finding of Ureaplasma suggested that besides known pathogens such as Mycoplasma and Actinobacillus, unknown pathogens can exist in the respiratory system of diseased pigs and provide a potential basis for clinical treatment.

Differences in pig respiratory tract and peripheral blood immune responses to Actinobacillus pleuropneumoniae

Excessive cytokine production is an important component of the acute respiratory distress syndrome and multiple organ failure. Pneumonia can lead to an overexpression of cytokines, although comparatively little is known about the relevance and differences in cytokines between blood and lung. In this study, piglets were experimentally infected intranasally with Actinobacillus pleuropneumoniae (APP), and transcriptomes of lung tissue and peripheral blood mononuclear cells determined. In addition, the levels of 30 cytokines in broncheoalveolar lavage fluid (BALF) and sera were determined by ELISA. Post infection, there was an early increase in lung monocytes, and a later rise in inflammatory cytokines in BALF. Blood lymphocytes increased early in infection and there was a rise in inflammatory cytokines in the peripheral blood of infected piglets. Genes involved in cytokine production, leukocyte migration and differentiation, lymphocyte activation, and cytokine-mediated signaling pathways in the transcriptomes of lung tissue were significantly down-regulated early in infection. At this early phase of APP infection (0-6 h), the cytokines IL-1β, MCP-1, and IL-5 in sera increased rapidly and significantly, while many cytokines in BALF decreased. At 48 h post-infection, cytokines in sera were no longer significantly increased, although some were up-regulated in BALF, and there was aggravated pathological damage in the lungs at this time. The data indicate there are substantial differences between immune cells and cytokines in the lung and peripheral blood of APP infected piglets at equivalent time points. The results increase our understanding of pig-APP host interactive biology, and will be important in formulating future therapeutic and preventative strategies to prevent disease caused by APP.

iTRAQ-based quantitative proteomic analysis of peripheral blood serum in piglets infected with Actinobacillus pleuropneumoniae

Porcine pleuropneumonia caused by Actinobacillus pleuropneumoniae (APP) is a swine respiratory disease with an important impact around the world either as a single infection or part of the porcine respiratory disease complex. The data of interaction between hosts and pathogens has becoming more crucial for exploration of the mechanism. However, up to now, comparatively little information is available on the systemic and dynamic changes that occur in pig serum in response to APP infection. This study used iTRAQ to identify differentially expressed proteins (DEPs) in pig serum in response to APP infection. Compared with the APP un-infected group (S0),there were 137 up-regulated and 68 down-regulated proteins at 24 h (S24), and 81 up-regulated and 107 down-regulated proteins at 120 h (S120). At 24 h, the immune response was not significantly enriched, but cell adhesion, cytosol, Golgi apparatus, GTP and ATP binding and regulation of cell cycle were extremely active, implying host preparation of immune response starting. Subsequently, innate immune response, negative regulation of apoptotic process, immunological synapse, adaptive immune response, the regulation of inflammatory response, positive regulation of T cell proliferation were more enhanced at 120 h then that of 24 h, representing innate immunity transferring to the adaptive, while endocytosis, cell adhesion and platelet aggregation showed obvious decline. The pathways of T cell receptor signaling pathway, cytokine–cytokine receptor interaction, complement and coagulation cascades, leukocyte transendothelial migration were active remarkably during all infection period, and more pathways could connect to form innate immune defense networks. Surprisingly, the pathways like amoebiasis, rheumatoid arthritis and malaria had been found up-regulated. As a conclusion, APP could delay host inflammatory response to the infection at early stage, and induced innate immunity to convert from adhesion, interaction into complement activation, proteasome digestion, bacterial invasion at later stage. This would increase our understanding of the porcine distinct response to APP infection.

Proinflammatory Cytokine Changes in Bronchoalveolar Lavage Fluid Cells Isolated from Pigs Infected Solely with Porcine Reproductive and Respiratory Syndrome Virus or Co-infected with Swine Influenza Virus

Introduction

The study evaluated the patterns of local innate immune response in bronchoalveolar lavage fluid (BALF) cells of pigs infected with porcine reproductive and respiratory syndrome virus (PRRSV) alone or co-infected with swine influenza virus (SIV).

Material and Methods

The study was performed on 26 seven-week-old pigs in three groups: PRRSV-infected (n = 11), PRRSV and SIV-infected (n = 11), and control (n = 4). BALF was collected post euthanasia at 2 and 4 dpi (three piglets per inoculated group) and at 21 dpi (all remaining pigs). Expression of IFN-α, IFN-γ, IL-1β, IL-6, IL-8, and IL-10 mRNA was quantified in BALF cells. PRRSV RNA was quantified in BALF samples using a commercial real-time RT-PCR kit.

Results

The three cytokines IFN-α, IFN-γ, and IL-1β presented significant expression changes in all experimental pigs. In PRRSV-infected animals IL-8 also did, but in co-infected subjects IL-6 and IL-10 were the additional upregulated cytokines. The highest number of differentially expressed genes was observed at 4 dpi, and significant differences in cytokine gene expression did not occur between the experimental groups at any other time point. The mean PRRSV load in the BALF of PRRSV-infected pigs was higher than that of co-infected pigs at each time point, having statistical significance only at 4 dpi.

Conclusion

The results of the study indicate that infection with PRRSV alone as well as with SIV interferes with innate and adaptive immune response in the infected host. They also showed that co-infection demonstrates additive effects on IL-6 and IL-10 mRNA expression levels.