Multiplex analysis of pro-inflammatory cytokines in serum of Actinobacillus pleuropneumoniae-infected pigs

Effects of fisetin on virulence of Actinobacillus Pleuropneumoniae

Porcine infectious pleuropneumonia (PCP), caused by Actinobacillus pleuropneumoniae (APP), is a highly infectious respiratory disease of pigs, resulting in significant economic losses to the industry. Apx toxins are cytolytic virulence factors produced by APP. The natural flavonoid fisetin has a variety of biological activities, including antioxidant and anti-inflammatory properties. This study aimed to investigate the protective effects of fisetin against APP. Fisetin was found to effectively inhibit the hemolytic activity of both APP culture supernatants and the purified toxins, and blood agar plate results also showed that the addition of fisetin to APP reduced the diameter of the hemolytic zone. Fisetin did not influence the expression of Apx toxins, although it reduced that of the virulence factor CPS. In vitro, fisetin effectively inhibited APP cytotoxicity and intracellular colonization, as well as intracellular ROS production. Furthermore, it reduced the expression of IL-6, TNF-α, and TLR4 in porcine alveolar macrophages (3D4/21). In vivo, fisetin reduced APP colonization of mouse lung tissues and improved the survival rate of APP-infected mice. In conclusion, fisetin was found to reduce the release of pro-inflammatory cytokines and ROS, decrease the risk of hemolysis, and attenuate APP virulence. The findings highlight the potential therapeutic value of fisetin in the management of APP infection. Further investigations into the mechanisms underlying the effects of fisetin are warranted.

Actinobacillus pleuropneumoniae infection activates IL-1β expression in porcine alveolar macrophages via β-amyloid production

Actinobacillus pleuropneumoniae (A. pleuropneumoniae), a porcine respiratory tract pathogen, causes porcine pleuropneumonia. Porcine alveolar macrophages (PAMs) play a crucial role during A. pleuropneumoniae infection. Amyloid precursor protein (APP) can be cleaved by β- and γ-secretase to produce β-amyloid (Aβ). APP and Aβ are associated with the inflammatory response. They activate microglia and astrocytes to secrete IL-1β, IL-6, and other cytokines. In this study, we found that during the interaction between A. pleuropneumoniae and PAMs, the two-component system CpxAR upregulates wecA expression, increasing lipopolysaccharide (LPS) production. LPS promotes APP production and cleavage to generate Aβ. The Aβ activates NF-κB, leading to increased IL-1β expression. We hypothesize that A. pleuropneumoniae infection of PAMs regulates APP production and cleavage to control Aβ levels. Different quantities of Aβ induce PAMs to produce varying amounts of cytokines, leading to different pathological processes in porcine pleuropneumonia.

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.

Biomarkers of sepsis in pigs, horses and cattle: from acute phase proteins to procalcitonin

Sepsis is a complex clinical syndrome triggered by an inflammatory host response to an infection. It is usually complicated to detect and diagnose, and has severe consequences in human and veterinary health, especially when treatment is not started early. Therefore, efforts to detect sepsis accurately are needed. In addition, its proper diagnosis could reduce the misuse of antibiotics, which is essential fighting against antimicrobial resistance. This case is a particular issue in farm animals, as antibiotics have been traditionally given massively, but now they are becoming increasingly restricted. When sepsis is suspected in animals, the most frequently used biomarkers are acute phase proteins such as C-reactive protein, serum amyloid A and haptoglobin, but their concentrations can increase in other inflammatory conditions. In human patients, the most promising biomarkers to detect sepsis are currently procalcitonin and presepsin, and there is a wide range of other biomarkers under study. However, there is little information on the application of these biomarkers in veterinary species. This review aims to describe the general concepts of sepsis and the current knowledge about the biomarkers of sepsis in pigs, horses, and cattle and to discuss possible advances in the field.

A Proposed Role for Pro-Inflammatory Cytokines in Damaging Behavior in Pigs

Sickness can change our mood for the worse, leaving us sad, lethargic, grumpy and less socially inclined. This mood change is part of a set of behavioral symptoms called sickness behavior and has features in common with core symptoms of depression. Therefore, the physiological changes induced by immune activation, for example following infection, are in the spotlight for explaining mechanisms behind mental health challenges such as depression. While humans may take a day off and isolate themselves until they feel better, farm animals housed in groups have only limited possibilities for social withdrawal. We suggest that immune activation could be a major factor influencing social interactions in pigs, with outbreaks of damaging behavior such as tail biting as a possible result. The hypothesis presented here is that the effects of several known risk factors for tail biting are mediated by pro-inflammatory cytokines, proteins produced by the immune system, and their effect on neurotransmitter systems. We describe the background for and implications of this hypothesis.

The effect of lipopolysaccharide (LPS) on inflammatory markers in blood and brain and on behavior in individually-housed pigs

Most of us have experienced deterioration of mood while ill. In humans, immune activation is associated with lethargy and social withdrawal, irritability and aggression; changes in social motivation could, in theory, lead to less functional interactions. This might also be the case for animals housed in close confinement. Tail biting in pigs is an example of damaging social behavior, and sickness is thought to be a risk factor for tail biting outbreaks. One possible mechanism whereby sickness may influence behavior is through cytokines. To identify possible mediators between immune activation and behavioral change, we injected 16 gilts with lipopolysaccharide (LPS; O111:B4; 1.5 μg kg^-1 IV through a permanent catheter). In LPS-treated pigs, a significant increase in cortisol, TNF-α, IL-1 receptor antagonist, IL-6, and IL-8 was observed alongside decreased activity within the first 6 h after the injection. CRP was elevated at 12 and 24 h after injection, and food intake was reduced for the first 24 h after injection. Three days post-injection, LPS pigs had lower levels of noradrenaline in their hypothalamus, hippocampus and frontal cortex compared to saline-injected pigs. Pigs injected with LPS also had higher levels of the pro-inflammatory cytokine IFN-γ in their frontal cortex compared to saline-injected pigs. Thus, a low dose of LPS can induce changes in brain cytokine levels and neurotransmitter levels that persist after inflammatory and stress markers in the periphery have returned to baseline levels.

Update on Actinobacillus pleuropneumoniae-knowledge, gaps and challenges

Porcine pleuropneumonia, caused by the bacterial porcine respiratory tract pathogen Actinobacillus pleuropneumoniae, leads to high economic losses in affected swine herds in most countries of the world. Pigs affected by peracute and acute disease suffer from severe respiratory distress with high lethality. The agent was first described in 1957 and, since then, knowledge about the pathogen itself, and its interactions with the host, has increased continuously. This is, in part, due to the fact that experimental infections can be studied in the natural host. However, the fact that most commercial pigs are colonized by this pathogen has hampered the applicability of knowledge gained under experimental conditions. In addition, several factors are involved in development of disease, and these have often been studied individually. In a DISCONTOOLS initiative, members from science, industry and clinics exchanged their expertise and empirical observations and identified the major gaps in knowledge. This review sums up published results and expert opinions, within the fields of pathogenesis, epidemiology, transmission, immune response to infection, as well as the main means of prevention, detection and control. The gaps that still remain to be filled are highlighted, and present as well as future challenges in the control of this disease are addressed.

To be blamed or pitied? The effect of illness on social behavior, cytokine levels and feed intake in undocked boars

Tail biting is detrimental to animal welfare and has negative consequences for producer economy. Poor health is one of the risk factors for tail biting. The first aim of this study was therefore to test for links between health status and behavior related to tail biting at the individual level. The second aim of this study was to test whether variation in cytokines was related to variation in social behavior. These small molecules produced upon immune activation are known to influence behavior both in the direction of withdrawal and increased aggression. This could potentially increase non-functional social behavior and thereby the risk of a tail biting outbreak. To investigate this, we collected behavioral data, health data, feeding data and blood samples from undocked boars at a test station farm in Norway. We compared groups with three different diagnoses: osteochondrosis diagnosed by computer tomography scanning (OCSAN), osteochondrosis diagnosed by clinical examination (OCCLIN) and respiratory tract disease (RESP), with healthy controls (CTR). We tested whether the diagnoses were associated with feeding and growth, social behavior and cytokine levels. We then tested whether there were correlations between cytokine levels and social behavior. We also provide raw data on cytokine levels in the extended sample (N=305) as there are few publications on cytokine levels measured in pigs living under commercial conditions. OCCLIN pigs visited the feeder less, and fed longer compared to CTR pigs. Pigs diagnosed with RESP showed a large drop in growth the first week after filming, which corresponds to the week they were likely to have been diagnosed with illness, and a tendency to compensatory increase in the week after that. Social behavior differed between experimental groups with OCSCAN pigs receiving more social behavior (both aggressive and non-aggressive) compared to CTR, and RESP pigs tending to perform more ear- and tail-biting than controls. There were no differences in absolute levels of cytokines between categories. However IL1-ra and IL-12 showed correlations with several behaviors that have been shown by others to be associated with current or future tail biting activity. To our knowledge, this is the first published study indicating a role for illness in non-functional social behavior in pigs and the first showing a correlation between cytokine levels and social behavior.

Host-pathogen interplay at primary infection sites in pigs challenged with Actinobacillus pleuropneumoniae

Background

Actinobacillus (A.) pleuropneumoniae is the causative agent of porcine pleuropneumonia and causes significant losses in the pig industry worldwide. Early host immune response is crucial for further progression of the disease. A. pleuropneumoniae is either rapidly eliminated by the immune system or switches to a long-term persistent form. To gain insight into the host-pathogen interaction during the early stages of infection, pigs were inoculated intratracheally with A. pleuropneumoniae serotype 2 and humanely euthanized eight hours after infection. Gene expression studies of inflammatory cytokines and the acute phase proteins haptoglobin, serum amyloid A and C-reactive protein were carried out by RT-qPCR from the lung, liver, tonsils and salivary gland. In addition, the concentration of cytokines and acute phase proteins were measured by quantitative immunoassays in bronchoalveolar lavage fluid, serum and saliva. In parallel to the analyses of host response, the impact of the host on the bacterial pathogen was assessed on a metabolic level. For the latter, Fourier-Transform Infrared (FTIR-) spectroscopy was employed.

Results

Significant cytokine and acute phase protein gene expression was detected in the lung and the salivary gland however this was not observed in the tonsils. In parallel to the analyses of host response, the impact of the host on the bacterial pathogen was assessed on a metabolic level. For the latter investigations, Fourier-Transform Infrared (FTIR-) spectroscopy was employed. The bacteria isolated from the upper and lower respiratory tract showed distinct IR spectral patterns reflecting the organ-specific acute phase response of the host.

Conclusions

In summary, this study implies a metabolic adaptation of A. pleuropneumoniae to the porcine upper respiratory tract already during early infection, which might indicate a first step towards the persistence of A. pleuropneumoniae. Not only in lung, but also in the salivary gland an increased inflammatory gene expression was detectable during the acute stage of infection.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-017-0979-6) contains supplementary material, which is available to authorized users.

Cytokine response to Hantaan virus infection in patients with hemorrhagic fever with renal syndrome

Hantaan virus (HTNV) infection of the human body causes a severe acute infectious disease known as hemorrhagic fever renal syndrome (HFRS). The aim of this study was to correlate patient cytokine profiles to HFRS severity. In this study, we discuss the clinical significance of evaluating HFRS treatment outcomes using cytokine information. The levels of 18 cytokines were quantitatively determined in three groups: 34 HTNV IgM+ cases, 63 HTNV IgM- negative cases, and 78 healthy volunteers. The level of 14 serum cytokines were higher in the patient group than that in the healthy control group. In the 34 HTNV IgM+ patient sera, a set of 27 cytokines was further assessed. The cytokines of TNF-β, IL-1ra, and IL-6 were detected at higher level in the IgM+ group than that in the IgM- group. The deterioration of HFRS was accompanied with multiple cytokines increased, such as IL-1ra, IL-12p70, IL-10, IP-10, IL-17, IL-2, and IL-6. Our data indicate that serum cytokine levels are associated with the progression of HFRS.