A proteomic reference map for pig serum proteins as a prerequisite for diagnostic applications

Proteomic methods for the study of porcine acute phase proteins - anything new to detect?

Acute phase proteins (APPs) reflect the health status of individuals and are important tools in diagnostics, as their altered levels are a sign of disturbed homeostasis. While, in most cases, quantitation of known serum APPs is routinely performed by immunoassays, proteomics is helpful in discovery of new biomarker candidates, especially in samples other than body fluids. Besides putting APP regulation into an overall context of differentially abundant proteins, this approach can detect further details or outright new features in protein structure or specific modifications, and help understand better their function. Thus, it can show up ways to make present diagnostic assays more sensitive and/or specific, or correlate regulations of disease-specific proteins. The APP repertoire is dependent on the species. The pig is both, an important farm animal and a model animal for human diseases, due to similarities in physiology. Besides reviewing existing literature, yet unpublished examples for two-dimensional electrophoresis in connection with pig APPs highlight some of the benefits of proteomics. Of further help would be the emerging targeted proteomics, offering the possibility to determine particular isoforms or proteoforms, without the need of specific antibodies, but this method is presently scarcely used in veterinary medicine.

Immunoproteomic Analysis of Trichinella britovi Proteins Recognized by IgG Antibodies from Meat Juice of Carnivores Naturally Infected with T. britovi

Infection with Trichinella nematodes elicits non-specific and specific immune responses; these depend on the dose of infection, the nematode, and the host species. Few studies have examined the presence of specific antibodies against Trichinella spp. in the meat juice of wild animals. The aims of the study were to determine the prevalence of antibodies against Trichinella spp. in meat juice and to identify the specific proteins reacting with the meat juice from free-living carnivores naturally infected with the parasite. Meat juice samples were taken from foxes, badgers, raccoon dogs, and martens and tested with indirect ELISA. Antibodies against Trichinella spp. were detected in 10% of foxes and 46% of raccoon dogs. The ELISA results were confirmed by immunoblot, which revealed different protein patterns in meat juice from red foxes, raccoon dogs, and badgers. The most frequently observed bands were sent for further analysis by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) for the detection of Trichinella britovi immunogenic proteins. The results confirm the presence of proteins such as serine protease and heat shock proteins associated with Trichinella infection. These findings provide that meat juice is a useful matrix for proteomic analysis.

Hemolymph proteins: An overview across marine arthropods and molluscs

In this compilation we collect information about the main protein components in hemolymph and stress the continued interest in their study. The reasons for such an attention span several areas of biological, veterinarian and medical applications: from the notions for better dealing with the species - belonging to phylum Arthropoda, subphylum Crustacea, and to phylum Mollusca - of economic interest, to the development of 'marine drugs' from the peptides that, in invertebrates, act as antimicrobial, antifungal, antiprotozoal, and/or antiviral agents. Overall, the topic most often on focus is that of innate immunity operated by classes of pattern-recognition proteins. SIGNIFICANCE: The immune response in invertebrates relies on innate rather than on adaptive/acquired effectors. At a difference from the soluble and membrane-bound immunoglobulins and receptors in vertebrates, the antimicrobial, antifungal, antiprotozoal and/or antiviral agents in invertebrates interact with non-self material by targeting some common (rather than some highly specific) structural motifs. Developing this paradigm into (semi) synthetic pharmaceuticals, possibly optimized through the modeling opportunities offered by computational biochemistry, is one of the lessons today's science may learn from the study of marine invertebrates, and specifically of the proteins and peptides in their hemolymph.

Generation of reference serum proteome map for monitoring swine health

To the best of our knowledge, it is the first report on pig serum proteome map generated with LAPs enriched serum using nano ESI LC-MS/MS method. A total of 224 proteins were identified including several proteins not yet reported in earlier pig serum proteome maps. Moreover, identification of many intracellular proteins indicates their usefulness in determination of altered cell functionality. Altogether, the identified proteins in our study can serve as baseline prerequisite for future analytical studies to understand different patho-physiological conditions in pigs.

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.

Characterizing the Serum Proteome of Donkeys (Equus asinus)

Serum and plasma are commonly used in clinical practice considering the widely accepted fact that the "normal" protein expression pattern of a healthy animal changes under disease conditions. We herein used a label-free mass spectrometry-based quantitative proteomics approach to characterize the serum proteome of donkeys. A total of 277 unique proteins were identified from 2,388 unique peptides. Gene ontology analyses showed that the most frequent processes were related to metabolic activities and biological regulation, response to stimulus, and immune system processes. The main annotated areas of origin were the extracellular region, extracellular region part, and organelle, and their molecular functions included binding, catalytic activity, and molecular function regulator. Analyses using the Clusters of Orthologous Groups for Eukaryotic Complete Genomes database indicated that the identified proteins could be categorized into three main groups: signal transduction mechanisms, amino acid transport and metabolism, and defense mechanisms. Most of the unique proteins were associated with the complement and coagulation cascades, and they participated in several disease-related metabolic pathways. Our results should be crucial for further analyses of changes in different physiological and pathophysiological conditions in donkeys.

Proteomics profiling of swine serum following lipopolysaccharide stimulation

RATIONALE

There are no approved animal drugs for management of inflammation in swine due to lack of validated animal models. To assess efficacy, it was essential to develop proteomics approaches to identify suitable biomarkers of inflammation as presented in this study.

METHODS

Serum samples were collected from a group of four pigs prior to (baseline) and 24 and 48 h following lipopolysaccharide (LPS) stimulation to reveal proteomic changes during inflammation. Two other pigs served as untreated controls. Proteins were separated by either one-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) or two-dimensional (2D) gel electrophoresis (2DE) prior to analysis by nano-flow liquid chromatography (nLC) coupled to tandem mass spectrometry (MS/MS).

RESULTS

We identified 165 proteins using SDS-PAGE, of which 47 proteins were also detected by 2DE prior to nLC/MS/MS. More than half (72%) of all characterized proteins were modulated as a result of LPS stimulation, many of which are known to be involved with innate and adaptive immunity. Pig serum samples obtained 24 h after LPS initiation of inflammation showed protein modulations of serum albumin, serotransferrin, light and heavy immunoglobulin chains (IGs), and major acute phase proteins including haptoglobin (HPT), serum amyloid A2 (SAA2), C-reactive protein (CRP), β-2-glycoprotein 1 (B-2GP1), alpha-2-HS-glycoprotein (A2HS), α-1-antitrypsin (A1AT), and α-1-acid glycoprotein (A1AG). SAA2 was distinguished from the other SAA isoforms by the unique peptide sequence of SAA2.

CONCLUSIONS

The results provided proteomics analysis of swine serum due to LPS stimulation and indicated the importance of SAA2, which appears to be unique and may be regarded as a potential clinical diagnostic biomarker of inflammation.

Comparative Proteomic Analysis of Serum from Pigs Experimentally Infected with Trichinella spiralis, Trichinella britovi, and Trichinella pseudospiralis

Although the available proteomic studies have made it possible to identify and characterize Trichinella stage-specific proteins reacting with infected host-specific antibodies, the vast majority of these studies do not provide any information about changes in the global proteomic serum profile of Trichinella-infested individuals. In view of the above, the present study aimed to examine the protein expression profile of serum obtained at 13 and 60 days postinfection (d.p.i.) from three groups of pigs experimentally infected with Trichinella spiralis, Trichinella britovi, and Trichinella pseudospiralis and from uninfected, control pigs by two-dimensional gel electrophoresis (2-DE) followed by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. The comparative proteomic analysis of the T. spiralis group vs. the control group revealed 5 differently expressed spots at both 13 and 60 d.p.i. Experimental infection with T. britovi induced significant expression changes in 3 protein spots at 13 d.p.i. and in 6 protein spots at 60 d.p.i. in comparison with the control group. Paired analyses between the group infected with T. pseudospiralis and the uninfected control group revealed 6 differently changed spots at 13 d.p.i. and 2 differently changed spots at 60 d.p.i. Among these 27 spots, 15 were successfully identified. Depending on the Trichinella species triggering the infection and the time point of serum collection, they were IgM heavy-chain constant region, antithrombin III-precursor, immunoglobulin gamma-chain, clusterin, homeobox protein Mohawk, apolipoprotein E precursor, serum amyloid P-component precursor, Ig lambda chains, complement C3 isoform X1, and apolipoprotein A-I. Our results demonstrate that various Trichinella species and different phases of the invasion produce a distinct, characteristic proteomic pattern in the serum of experimentally infected pigs.

Identification of potential serum biomarkers in pigs at early stage after Lipopolysaccharide injection

The identification of useful biological indicators to monitor the body response before the presentation of clinical diseases has practical value in livestock production. To identify potential biomarkers in pigs at the early stage during inflammation, 12 pigs were intramuscularly injected with 2mL of Lipopolysaccharide (LPS, 15μg/kg BW) or saline. Serum protein expression profiles were detected with two-dimensional electrophoresis (2-DE) and matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) techniques. Serum biochemical indicators and acute phase protein (APP) concentrations were analyzed with an automatic biochemical analyzer and ELISA, respectively. Of the serum biochemical indicators, creatinine concentration significantly increased 6h post infection, whereas albumin showed a decreased tendency. The 2-DE and MALDI-TOF mass spectrometry technique detected 17 protein spots representing 10 proteins: α-1-antichymotrypsin, albumin, bovine lactoferrin, serotransferrin, serpin A3-6, immunoglobulin light chain (κ chain, mu chain), complement C3 precursor, zinc-α-2-glycoprotein (ZAG), and ceruloplasmin. Two proteins were selected to confirm the mass spectrometry results, and resulting differences accorded with the proteomics results. Of the four typical acute phase protein (APPs) measured, the C-reactive protein (CRP) and haptoglobin (HP) concentrations increased significantly, while no differences were observed in the pig-major acute phase protein (Pig-MAP) and transthyretin (TTR) contents. The results showed that serum creatinine, CRP, HP, and ten other proteins content changed significantly after LPS injection. Of these proteins, ZAG was first reported in pigs during inflammation. These proteins show great promise as biomarkers to monitor the health status and welfare of pigs during the early stage of LPS-induced inflammation.

Nano-LC-MS/MS for the identification of proteins trapped in sorbent cartridges used for coupled plasma filtration-adsorption treatments of healthy pigs

A dedicated proteomic approach based on nano-Liquid Chromatography coupled with tandem mass spectrometry in ion trap is proposed for the analysis of proteins trapped in sorbent resin cartridges used to remove inflammatory mediators from blood by coupled plasma filtration adsorption (CPFA). The final purpose of the proposed proteomic approach was to obtain a reference map of plasma proteins trapped in CPFA sorbents used for the extracorporeal blood purification of healthy pigs, with the potential impact to design new bio-filters able to control the inflammatory imbalance under pathological conditions, such as severe sepsis. The five main steps of the proteomics analysis, (i) protein extraction from resin cartridges, (ii) two-dimensional gel electrophoresis (2D-PAGE) for protein separation and profiling, (iii) in-gel proteolytic digestion, (iv) tandem mass analysis of peptides resulting from enzymatic cleavage and (v) bioinformatics, for protein identification and post-processing validation of MS/MS data sets, have been carefully evaluated. Prior to electrophoresis, the efficiency of different extraction solutions and procedures to recovery plasma proteins trapped into the sorbents were tested. Then, a rapid one-step procedure for protein extraction was optimized. Protein bands corresponding to the main plasma proteins, namely porcine serum albumin, serotransferrin and immunoglobulins, were identified. In addition, the presence of haptoglobin, hemopexin, α-1 acid glycoprotein and fetuin-A, that are known as acute-phase reaction proteins, was observed, suggesting that CPFA resins led to a non-specifically protein depletion from plasma, rather than targeting specific molecules.

Growth promotion in pigs by oxytetracycline coincides with down regulation of serum inflammatory parameters and of hibernation-associated protein HP-27

The growth promoting effect of supplementing animal feed with antibiotics like tetracycline has traditionally been attributed to their antibiotic character. However, more evidence has been accumulated on their direct anti-inflammatory effect during the last two decades. Here we used a pig model to explore the systemic molecular effect of feed supplementation with sub therapeutic levels of oxytetracycline (OTC) by analysis of serum proteome changes. Results showed that OTC promoted growth, coinciding with a significant down regulation of different serum proteins related to inflammation, oxidation and lipid metabolism, confirming the anti-inflammatory mechanism of OTC. Interestingly, apart from the classic acute phase reactants also down regulation was seen of a hibernation associated plasma protein (HP-27), which is to our knowledge the first description in pigs. Although the exact function in non-hibernators is unclear, down regulation of HP-27 could be consistent with increased appetite, which is possibly linked to the anti-inflammatory action of OTC. Given that pigs are good models for human medicine due to their genetic and physiologic resemblance, the present results might also be used for rational intervention in human diseases in which inflammation plays an important role such as obesity, type 2 diabetes and cardiovascular diseases.

Concentration and pattern changes of porcine serum apolipoprotein A-I in four different infectious diseases

Apolipoprotein A-I (Apo A-I) is a major protein in lipid/lipoprotein metabolism and decreased serum levels have been observed in many species in response to inflammatory and infectious challenges. Little is known about the porcine homologue, therefore in this work we have characterized it through biochemical and proteomic techniques. In 2DE, porcine serum Apo A-I is found as three spots, the two more acidic ones corresponding to the mature protein, the more basic spot to the protein precursor. Despite high sequence coverage in LC-MS/MS, we did not find a sequence or PTM difference between the two mature protein species. Besides this biochemical characterization, we measured overall levels and relative species abundance of serum Apo A-I in four different viral and bacterial porcine infectious diseases. Lower overall amounts of Apo A-I were observed in Salmonella typhimurium and Escherichia coli infections. In the 2DE protein pattern, an increase of the protein precursor together with a lower level of mature protein species were detected in the porcine circovirus type 2-systemic disease and S. typhimurium infection. These results reveal that both the porcine serum Apo A-I concentration and the species pattern are influenced by the nature of the infectious disease.

Proteomics in farm animals models of human diseases

The need to provide in vivo complex environments to understand human diseases strongly relies on the use of animal models, which traditionally include small rodents and rabbits. It is becoming increasingly evident that the few species utilised to date cannot be regarded as universal. There is a great need for new animal species that are naturally endowed with specific features relevant to human diseases. Farm animals, including pigs, cows, sheep and horses, represent a valid alternative to commonly utilised rodent models. There is an ample scope for the application of proteomic techniques in farm animals, and the establishment of several proteomic maps of plasma and tissue has clearly demonstrated that farm animals provide a disease environment that closely resembles that of human diseases. The present review offers a snapshot of how proteomic techniques have been applied to farm animals to improve their use as biomedical models. Focus will be on specific topics of biomedical research in which farm animal models have been characterised through the application of proteomic techniques.

Proteogenomics of selective susceptibility to endotoxin using circulating acute phase biomarkers and bioassay development in sheep: a review

Scientists have injected endotoxin into animals to investigate and understand various pathologies and novel therapies for several decades. Recent observations have shown that there is selective susceptibility to Escherichia coli lipopolysaccharide (LPS) endotoxin in sheep, despite having similar breed characteristics. The reason behind this difference is unknown, and has prompted studies aiming to explain the variation by proteogenomic characterisation of circulating acute phase biomarkers. It is hypothesised that genetic trait, biochemical, immunological and inflammation marker patterns contribute in defining and predicting mammalian response to LPS. This review discusses the effects of endotoxin and host responses, genetic basis of innate defences, activation of the acute phase response (APR) following experimental LPS challenge, and the current approaches employed in detecting novel biomarkers including acute phase proteins (APP) and micro-ribonucleic acids (miRNAs) in serum or plasma. miRNAs are novel targets for elucidating molecular mechanisms of disease because of their differential expression during pathological, and in healthy states. Changes in miRNA profiles during a disease challenge may be reflected in plasma. Studies show that gel-based two-dimensional electrophoresis (2-DE) coupled with either matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) or liquid chromatography–mass spectrometry (LC-MS/MS) are currently the most used methods for proteome characterisation. Further evidence suggests that proteomic investigations are preferentially shifting from 2-DE to non-gel based LC-MS/MS coupled with data extraction by sequential window acquisition of all theoretical fragment-ion spectra (SWATH) approaches that are able to identify a wider range of proteins. Enzyme-linked immunosorbent assay (ELISA), quantitative real-time polymerase chain reaction (qRT-PCR), and most recently proteomic methods have been used to quantify low abundance proteins such as cytokines. qRT-PCR and next generation sequencing (NGS) are used for the characterisation of miRNA. Proteogenomic approaches for detecting APP and novel miRNA profiling are essential in understanding the selective resistance to endotoxin in sheep. The results of these methods could help in understanding similar pathology in humans. It might also be helpful in the development of physiological and diagnostic screening assays for determining experimental inclusion and endpoints, and in clinical trials in future.

Proteomics on porcine haptoglobin and IgG/IgA show protein species distribution and glycosylation pattern to remain similar in PCV2-SD infection

Haptoglobin (Hp) and immunoglobulins are plasma glycoproteins involved in the immune reaction of the organism after infection and/or inflammation. Porcine circovirus type 2-systemic disease (PCV2-SD), formerly known as postweaning multisystemic wasting syndrome (PMWS), is a globally spread pig disease of great economic impact. PCV2-SD affects the immunological system of pigs causing immunosuppression. The aim of this work was to characterize the Hp protein species of healthy and PCV2-SD affected pigs, as well as the protein backbone and the glycan chain composition of porcine Hp. PCV2-SD affected pigs had an increased overall Hp level, but it did not affect the ratio between Hp species. Glycoproteomic analysis of the Hp β subunits confirmed that porcine Hp is N-glycosylated and, unexpectedly, O-glycosylated, a PTM that is not found on Hp from healthy humans. The glyco-profile of porcine IgG and IgA heavy chains was also characterized; decreased levels of both proteins were found in the investigated group of PCV2-SD affected pigs. Obtained results indicate that no significant changes in the N- and O-glycosylation patterns of these major porcine plasma glycoproteins were detectable between healthy and PCV2-SD affected animals.

BIOLOGICAL SIGNIFICANCE

PCV2-SD is a disease of great economic importance for pig production, characterized by a complex response of the immune system. In the search of a better diagnostic/prognostic marker for porcine PCV2-SD, extensive analyses of the Hp protein backbone and the glycan chains were thoroughly analyzed by various techniques. This resulted in detection and confirmation of Hp O-glycosylation and the glyco-profiling of porcine IgG and IgA. The N- and O-glycosylation of these major porcine plasma glycoproteins appears to be not affected by PCV2-SD infection. Interestingly, these data suggest that this viral infection, which significantly affects the immune responses of the host, leaves the biosynthetic glycosylation processes in the liver and immune cells unaffected. Lack of PTM changes is in contrast to findings in humans where for both proteins pattern changes have been reported in several chronic and inflammatory diseases. This underlines the importance of studying species in detail and not reaching to conclusions by analogy. Furthermore, since Hp is usually quantified by immunoassays in clinical routine analyses, our findings indicate that no bias in Hp determination capabilities due to an altered carbohydrate pattern is to be expected.

Analysis of the bovine plasma proteome by matrix-assisted laser desorption/ionisation time-of-flight tandem mass spectrometry

In this study, the bovine plasma proteome was analysed using a three step protocol: (1) plasma was treated with a combinatorial peptide ligand library (CPLL) to assimilate the differences in concentrations of different proteins in raw plasma; (2) CPLL-treated material was fractionated by three standard electrophoretic separation techniques, and (3) samples were analysed by nano-liquid chromatography (nLC) matrix-assisted laser desorption/ionisation (MALDI) time-of-flight tandem (TOF/TOF) mass spectrometry. The efficiencies of three fractionation protocols for plasma proteome analysis were compared. After size fractionation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), resolution of proteins was better and yields of identified proteins were higher than after charge-based fractionation by preparative gel-free isoelectric focussing. For proteins with isoelectric points >6 and molecular weights ⩾ 63 kDa, the best results were obtained with a 'shotgun' approach, in which the CPLL-treated plasma was digested and the peptides, rather than the proteins, were fractionated by gel-free isoelectric focussing. However, the three fractionation techniques were largely complementary, since only about one-third of the proteome was identified by each approach.

Activation of NF-κB contributes to production of pig-major acute protein and serum amyloid A in pigs experimentally infected with porcine circovirus type 2

Acute phase proteins (APPs) have protective and regulatory roles in the inflammatory response. Previous studies indicate that APPs in serum change after pigs are infected with porcine circovirus type 2 (PCV2), but the mechanisms underlying APP production have remained unclear. In this present study, 35-day-old pigs were challenged with PCV2 and responses compared to an uninfected control group. To investigate the concentrations of APPs in serum and the activity of NF-κB in the liver, five pigs in the PCV2-infected group were euthanized at 14, 21 and 35days post inoculation (dpi) while four pigs were sacrificed in the control group at 0, 14, 21 and 35 days, respectively. The concentrations of pig-major acute protein (Pig-MAP), C-reactive protein (CRP) and serum amyloid A (SAA) in infected animals were increased at 14 and 21 dpi, while the concentration of alpha-1 acid glycoprotein (AGP) was lower at 35 dpi, indicating that PCV2 induced the production of APPs. Moreover, the DNA binding activity of NF-κB and expression levels of NF-κB p65 subunit (NF-κB p65) from the cytoplasm to nucleus were increased at 14 and 21 dpi in the liver of infected pigs, while the phosphorylation of IκBα (p-IκBα) in the liver was also increased at 21dpi. This demonstrated that PCV2 infection induced the activation of NF-κB. Both SAA and Pig-MAP concentrations correlated significantly with expression levels of NF-κB p65, indicating that activation of NF-κB contributes to the production of SAA and Pig-MAP.

Pig α1-acid glycoprotein: characterization and first description in any species as a negative acute phase protein

The serum protein α1-acid glycoprotein (AGP), also known as orosomucoid, is generally described as an archetypical positive acute phase protein. Here, porcine AGP was identified, purified and characterized from pooled pig serum. It was found to circulate as a single chain glycoprotein having an apparent molecular weight of 43 kDa by SDS-PAGE under reducing conditions, of which approximately 17 kDa were accounted for by N-bound oligosaccharides. Those data correspond well with the properties of the protein predicted from the single porcine AGP gene (ORM1, Q29014 (UniProt)), containing 5 putative glycosylation sites. A monoclonal antibody (MAb) was produced and shown to quantitatively and specifically react with all microheterogenous forms of pig AGP as analyzed by 2-D electrophoresis. This MAb was used to develop an immunoassay (ELISA) for quantification of AGP in pig serum samples. The adult serum concentrations of pig AGP were in the range of 1-3 mg/ml in a number of conventional pig breeds while it was lower in Göttingen and Ossabaw minipigs (in the 0.3 to 0.6 mg/ml range) and higher in young (2-5 days old) conventional pigs (mean: 6.6 mg/ml). Surprisingly, pig AGP was found to behave as a negative acute phase protein during a range of experimental infections and aseptic inflammation with significant decreases in serum concentration and in hepatic ORM1 expression during the acute phase response. To our knowledge this is the first description in any species of AGP being a negative acute phase protein.

Inflammatory serum proteome pattern in mice fed a high-fat diet

To investigate the influence of diet on serum protein pattern, mice were fed for 8 weeks either control chow or a high-fat diet (containing 21 % w/w milk fat and 0.2 % w/w cholesterol); sera were collected and analyzed by 2-DE. The main positive acute-phase reactant proteins, haptoglobin and hemopexin, were significantly up-regulated in animals receiving the high-fat diet. Data on all other proteins also pointed to an inflammatory condition in these animals. The largest change in concentration was observed for carboxylesterase N, a circulating enzyme seldom connected with lipid metabolism in earlier reports. These observations agree with the notion of a link between diet-induced hyperlipidemia and the inflammatory component of its cardiovascular sequels in humans, but the effects in the experimental animals are massive and obviously affect most of the major serum proteins.

Detection of potential markers for systemic disease in saliva of pigs by proteomics: a pilot study

Animals with different health status have been studied in order to extend the knowledge about protein composition of porcine saliva samples and to discover potential salivary markers for systemic disease in porcine production. Clinical examination of animals was performed at farm level where 10 healthy pigs and 10 animals with evident clinical signs of disease were randomly selected. Saliva and blood samples were obtained and afterwards animals were humanely sacrificed to perform a complete necropsy. Levels of two acute phase proteins, haptoglobin and C-reactive protein, were used to identify possible active infections of the animals. Moreover, serological analysis, to the main porcine infectious diseases in the area, was performed. Salivary proteins were separated by two-dimensional gel electrophoresis followed by mass spectrometry for the identification of specific proteins. A total of 58 spots out of 75 were successfully identified by MS, which correspond to 20 unique proteins. Two different approaches were used to perform a statistical comparison of saliva protein patterns from healthy and diseased animals using the relative spot volume (% spot volume/total volume of all spot in the gel, approach "A") or taking also into account the total protein content of each saliva sample (μg of spot/mL of saliva, approach "B"). Both analyses showed three proteins in common that are differentially regulated between states. However, approach B was selected for biomarker searching since it gave an estimation of protein concentration and showed differential expression of proteins between both health states in a total of 10 proteins, which were up-regulated in disease. Mass spectrometric analysis identified those proteins as salivary lipocalin, lipocalin 1, double headed protease inhibitor protein, adenosine deaminase, haptoglobin, albumin fragments, S100-A8, S100-A9, S100-A12 and pancreatic alpha amylase. These proteins could be considered as potential salivary markers of disease.

A proteomic analysis of serum from dogs before and after a controlled weight-loss program

The objective of this study was to investigate how weight-loss program would alter the proteome of the serum of Beagle dogs. For this purpose, serum samples from 5 Beagle dogs, before and after weight loss, were analyzed using 2-dimensional electrophoresis. Protein profiles of all samples were obtained, divided into 2 classes (obese and lean), and compared using specific 2-dimensional software, giving a total of 144 spot matches. Statistical analysis revealed 3 spot matches whose expressions were modulated in response to weight loss: 2 protein spots were upregulated and 1 protein spot was downregulated in the obese state in comparison with the lean state of the dogs. Mass spectrometric identification of differentially regulated spots revealed that these protein spots corresponded to retinol-binding protein 4, clusterin precursor, and α-1 antitrypsin, respectively, which could be considered potential markers of obesity and obesity-related disease processes in dogs.

Proteomic evaluation of sheep serum proteins

BACKGROUND

The applications of proteomic strategies to ovine medicine remain limited. The definition of serum proteome may be a good tool to identify useful protein biomarkers for recognising sub-clinical conditions and overt disease in sheep. Findings from bovine species are often directly translated for use in ovine medicine. In order to characterize normal protein patterns and improve knowledge of molecular species-specific characteristics, we generated a two-dimensional reference map of sheep serum. The possible application of this approach was tested by analysing serum protein patterns in ewes with mild broncho-pulmonary disease, which is very common in sheep and in the peripartum period which is a stressful time, with a high incidence of infectious and parasitic diseases.

RESULTS

This study generated the first reference 2-DE maps of sheep serum. Overall, 250 protein spots were analyzed, and 138 identified.Compared with healthy sheep, serum protein profiles of animals with rhino-tracheo-bronchitis showed a significant decrease in protein spots identified as transthyretin, apolipoprotein A1 and a significant increase in spots identified as haptoglobin, endopin 1b and alpha1B glycoprotein.In the peripartum period, haptoglobin, alpha-1-acid glycoprotein, apolipoprotein A1 levels rose, while transthyretin content dropped.

CONCLUSIONS

This study describes applications of proteomics in putative biomarker discovery for early diagnosis as well as for monitoring the physiological and metabolic situations critical for ovine welfare.

Proteomic characterization by 2-DE in bovine serum and whey from healthy and mastitis affected farm animals

Acute phase proteins (APP) have been identified in whey and sera from healthy and mastitis cows through the proteomic analysis using two-dimensional electrophoresis (2-DE) coupled with Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS). Although normal and mastitis serum samples show relatively similar protein composition, marked differences in expression levels and patterns can be observed. Conversely, normal and mastitis whey showed a very different composition, likely due to extravasation of blood proteins to the mammary gland. Different isoforms from the most abundant protein in milk, casein, were detected in both normal and mastitis whey. Other proteins, such as lactotransferrin, were only detected in the inflamed animal samples. Immunoglobulins showed different patterns but not increased levels in the inflamed whey. Also, many cellular proteins in mastitis cow's whey, that were absent from healthy cow's milk. They are responsible for the great change in composition between normal and mastitis whey, especially those which exert a biological function related to immune defense. Data collected in this work are of interest for gaining information about physiological changes in protein patterns in different fluids and, the correspondent modifications as result of an acute phase process in farm. This article is part of a Special Issue entitled: Proteomics: The clinical link.

Effects of waterborne Cu exposure in gilthead sea bream (Sparus aurata): a proteomic approach

Aquatic organisms may suffer from exposure to high Cu concentrations, since this metal is widely used in feed supplementation, in pesticide formulation and as antifouling. Chronic exposure to Cu, even at sub-lethal doses, may strongly affect fish physiology. To date, several biomarkers have been used to detect Cu exposure in fish producing contrasting results. Therefore, we used a proteomic approach to clarify how Cu exposure may affect the serum proteome of gilthead sea bream (Sparus aurata), since serum could be considered a good source of early-biomarkers of Cu toxicosis. For this purpose we exposed juvenile gilthead sea bream to waterborne Cu (0.5 mg/L). Our results indicate that fish tightly regulate circulating Cu levels, which are not affected by metal exposure. This homeostatic control is mainly achieved by the liver, able to excrete high amounts of the metal via bile. Cu exposure caused differential expression of several serum proteins, 10 of which were identified by Mascot and BLAST search. All these proteins, with the exception of growth hormone receptor and γ-glutamyl-carboxylase, can be related to: 1) Cu-induced hepatotoxicity (cytochrome oxidase subunit I, alanine aminotransferase, glutathione S-transferase); 2) potential immunosuppression due to interference of Cu with the inflammation/immunity network (α-1 antitrypsin, angiotensinogen, complement component C3, recombination-activating protein-1 and warm temperature acclimation-related 65 kDa protein).

The pig as a model animal for studying cognition and neurobehavioral disorders

In experimental animal research, a short phylogenetic distance, i.e., high resemblance between the model species and the species to be modeled is expected to increase the relevance and generalizability of results obtained in the model species. The (mini)pig shows multiple advantageous characteristics that have led to an increase in the use of this species in studies modeling human medical issues, including neurobehavioral (dys)functions. For example, the cerebral cortex of pigs, unlike that of mice or rats, has cerebral convolutions (gyri and sulci) similar to the human neocortex. We expect that appropriately chosen pig models will yield results of high translational value. However, this claim still needs to be substantiated by research, and the area of pig research is still in its infancy. This chapter provides an overview of the pig as a model species for studying cognitive dysfunctions and neurobehavioral disorders and their treatment, along with a discussion of the pros and cons of various tests, as an aid to researchers considering the use of pigs as model animal species in biomedical research.

Enrichment of low-abundance proteins from bovine and porcine serum samples for proteomic studies

One of the main applications of serum proteomics is the identification of new biomarkers for animal disease or animal production. However, potential obstacles to these studies are the poor performance of affinity serum depletion methods based on human antigens when using animal samples, and loss of minor serum components bound to albumin and other proteins. In the present study, we have analyzed the efficiency and reproducibility of the ProteoMiner® beads with bovine and porcine serum samples, and compared to a traditional immunoaffinity-based albumin and IgG depletion system specific for human samples. The ProteoMiner kit is based on the use of a combinatorial peptide binding library and intends to enrich low-abundance proteins.

Proteomic analysis of porcine saliva

Saliva contains a number of proteins that may be useful as biomarkers of health and disease and can be easily obtained from large numbers of animals in a non-invasive, stress-free way. The objective of this study was to explore the protein composition of porcine saliva from 10 specific pathogen free pigs using first one-dimensional SDS-PAGE and then two-dimensional electrophoresis and mass spectrometry. A reference proteome pattern for porcine saliva was established with the identification of 13 different, mainly saliva-specific, proteins. These reference data will facilitate the investigation of salivary proteins potentially altered in disease and could serve as novel diagnostic biomarkers.