In vitro identification and verification of inflammatory biomarkers in swine

Development of a 3-transcript host expression assay to differentiate between viral and bacterial infections in pigs

Indiscriminate use of antibiotics to treat infections that are of viral origin contributes to unnecessary use which potentially may induce resistance in commensal bacteria. To counteract this a number of host gene transcriptional studies have been conducted to identify genes that are differently expressed during bacterial and viral infections in humans, and thus could be used as a tool to base decisions on the use of antibiotics. In this paper, we aimed to evaluate the potential of a selection of genes that have been considered biomarkers in humans, to differentially diagnose bacterial from viral infections in the pig. First porcine PBMC were induced with six toll-like receptor (TLR) agonists (FliC, LPS, ODN 2216, Pam3CSK4, poly I:C, R848) to mimic host gene expression induced by bacterial or viral pathogens, or exposed to heat-killed Actinobacillus pleuropneumoniae or a split influenza virus. Genes that were differentially expressed between bacterial and viral inducers were further evaluated on clinical material comprising eleven healthy pigs, and six pigs infected with A. pleuropneumoniae. This comprised three virally upregulated genes (IFI44L, MxA, RSAD2) and four bacterially upregulated genes (IL-1β, IL-8, FAM89A, S100PBP). All six infected pigs could be differentially diagnosed to healthy pigs using a host gene transcription assay based on the geometric average of the bacterially induced genes IL-8 and S100PBP over that of the virally induced gene MxA.

Lipopolysaccharide (LPS) induced inflammatory changes to differentially expressed miRNAs of the host inflammatory response

In veterinary medicine, inflammation in swine is evaluated principally by clinical signs. This method is often unreliable when assessing large animal populations because of inconsistent interpretations of clinical observations. This study examined whether changes in miRNA expression can predict the severity of the inflammatory response in swine after administration of Escherichia coli lipopolysaccharide (LPS). Whole blood from swine challenged with LPS at 0.125 μg/kg to 2.0 μg/kg body weight was collected at 0, 1, 3, and 8 h post LPS-challenge. Mature miRNAs were extracted from plasma and quantitative real-time-PCR (qRT-PCR) was used to evaluate the 84 most abundant swine miRNAs found in plasma. The miRNA changes in expression were assessed using the comparative CT Method (ΔΔCT method) for normalization with an exogenous control. The results revealed that expression of ssc-let-7e-5p, ssc-mir-22-3p, and ssc-miR-146a-5p were the most significantly changed miRNA over the time course. At 1 h post-LPS, ssc-let-7e-5p decreased as the LPS dosage levels increased from 0.125 to 1.0 μg/kg. Similarly, as the LPS doses increased from 0.125 to 0.5 μg/kg, ssc-miR-22-3p levels significantly decreased at 1 h post-LPS. In the 2.0 μg/kg LPS, ssc-miR-146a-5p levels increased between 0 and 3 h post-LPS; however, expression was downregulated with a 145 % decrease from 3 to 8 h. The three miRNA biomarkers suggest potentially useful surrogate endpoints for the evaluation of inflammatory and endotoxemia responses in swine.

Molecular mechanism of action responsible for carrageenan-induced inflammatory response

Carrageenan-induced inflammation has long been used as an in vivo model of local inflammation. We developed an in vitro model of inflammation using primary blood cells to characterize gene induction following carrageenan (λ-CGN) stimulation and identify the signal transduction pathway(s) through which λ-CGN worked, using swine whole blood cultures from Yorkshire barrows. Blood samples were divided into stimulated and unstimulated groups. Unstimulated blood was a control for λ-CGN treated cultures to delineate treatment effects from time-in-culture effects. All cultures were collected and separated into two fractions; supernatant for ELISA analyses and white blood cells for mRNA expression. Lambda (λ)-CGN induced MCP-1 at the proteomic and the genomic levels. Lambda-CGN increased IL-8 protein production but had no impact on serum amyloid A protein levels. Alveolar Macrophage-Derived Neutrophil Chemotactic Factor-II (AMCF-II), a swine-specific member of the IL8/GRO family, showed increased gene expression. TNF-α and IL-6 protein levels were not induced by λ-CGN stimulation. Stimulation of HEK-293 cells co-transfected with a single pattern recognition receptor and the secreted embryonic alkaline phosphatase (SEAP) read-out system demonstrated that λ-CGN signals through the TLR-2 and TLR-4 signal transduction pathways. Using silencing RNA to inhibit TLR6 expression in TLR2 transfected HEK-293 cells indicated that λ-CGN works through the TLR2/6 pathway. Silencing TLR6 expression in TLR4 transfected HEK-293 cells showed that λ-CGN stimulation of this cell line worked through a TLR4/6 heterodimer, as lipopolysaccharide (LPS) induced SEAP production through a TLR4 homodimer. These results demonstrate that although carrageenan can stimulate through TLR4 signaling pathways, it initiates an inflammatory response in these cells that differs from a typical endotoxin effect such as LPS stimulation, in terms of the pathways and gene products altered, suggesting that activation of TLR2/6 and TLR4/6 are the predominant pathways through which carrageenan induces inflammatory responses.

Innate immune responses induced by the saponin adjuvant Matrix-M in specific pathogen free pigs

Saponin-based adjuvants have been widely used to enhance humoral and cellular immune responses in many species, but their mode of action is not fully understood. A characterization of the porcine transcriptional response to Matrix-M was performed in vitro using lymphocytes, monocytes or monocyte-derived dendritic cells (MoDCs) and in vivo. The effect of Matrix-M was also evaluated in specific pathogen free (SPF) pigs exposed to conventionally reared pigs. The pro-inflammatory cytokine genes IL1B and CXCL8 were up-regulated in monocytes and lymphocytes after Matrix-M exposure. Matrix-M also induced IL12B, IL17A and IFNG in lymphocytes and IFN-α gene expression in MoDCs. Several genes were indicated as up-regulated by Matrix-M in blood 18 h after injection, of which the genes for IFN-α and TLR2 could be statistically confirmed. Respiratory disease developed in all SPF pigs mixed with conventional pigs within 1–3 days. Two out of four SPF pigs injected with saline prior to contact exposure displayed systemic symptoms that was not recorded for the four pigs administered Matrix-M. Granulocyte counts, serum amyloid A levels and transcription of IL18 and TLR2 coincided with disease progression in the pigs. These results support further evaluation of Matrix-M as a possible enhancer of innate immune responses during critical moments in pig management.

Biomarkers in Veterinary Medicine

This article summarizes the relevant definitions related to biomarkers; reviews the general processes related to biomarker discovery and ultimate acceptance and use; and finally summarizes and reviews, to the extent possible, examples of the types of biomarkers used in animal species within veterinary clinical practice and human and veterinary drug development. We highlight opportunities for collaboration and coordination of research within the veterinary community and leveraging of resources from human medicine to support biomarker discovery and validation efforts for veterinary medicine.

IPEC-J2 cells as reporter system of the anti-inflammatory control actions of interferon-alpha

Interferon-alpha (IFN-α) shows potent immunomodulatory properties, which underlies its use for low-dose oral treatments of diverse viral infections and immunopathological conditions. The studies on oral administration have been hampered by the lack of recognized in vitro models, reproducing the in vivo control action of IFN-α over inflammatory cytokine responses. Owing to these reasons, the aim of our study was to validate IPEC-J2 (a continuous cell line of porcine intestinal epithelial cells) as a reporter system of the properties of IFN-α. Three different experimental conditions (oxidative stress, inflammatory response, and amplification of lymphoid cell signals) were selected to evaluate the effects of porcine recombinant IFN-α1 (rIFN-α) and 2 natural porcine IFN-α preparations (nIFN-α). The IFNs under study showed significantly different control actions in IPEC-J2 cells. In particular, rIFN-α was shown to down-regulate interleukin (IL)-8, IL-1β, tumor necrosis factor (TNF)-α, and β-defensin 1 genes either directly, or indirectly through second messengers released by IFN-α-treated lymphoid cells. With regard to IL-6, only second messengers from IFN-α-treated lymphoid cells could regulate the expression of this cytokine. Our results suggest that IPEC-J2 cells can be a useful tool for investigating the regulatory actions of type I IFNs and the second messengers thereof. The results provided by this model could be conveniently exploited in studies on enteric diseases sustained by infectious or noninfectious stressors.

Fast measurement of serum amyloid A in different specimens from swine by using a new one-step time-resolved fluorescent immunoassay

The objective of the present study was to develop a one-step, fast, competitive time-resolved fluorescent immunoassay to determine porcine serum amyloid A (SAA) by using species-specific reagents. The assay consisted of an all-in-one format involving only 55 min of incubation that was adapted and validated for use in 3 different specimens: serum, saliva, and meat juice. The method had overall within- and between-run coefficients of variation under 8% and 12%, respectively, and coefficients of determination higher than 0.93 for linearity under dilution analysis for all specimens. The limits of detection were 0.32 mg/l, 0.28 mg/l, and 1.74 mg/l for serum, saliva, and meat juice measurements, respectively. Upper and lower limits of quantification were determined for each sample type and resulted in wide assay ranges that allowed a precise SAA measurement in all the fluids investigated. Statistically significant differences (P = 0.0004 for serum and P < 0.0001 for the saliva and meat juice samples) in SAA levels were found when healthy (n = 20) and diseased (n = 20) pigs were compared. The obtained results indicate that this fast, sensitive, and robust assay for SAA measurement could be of use to determine health and welfare status in swine by employing alternative samples to serum.