C-reactive protein, haptoglobin and Pig-Major acute phase protein profiles of pigs infected experimentally by different isolates of porcine reproductive and respiratory syndrome virus

Insights into genetic determinants of piglet survival during a PRRSV outbreak

Breeding animals to produce more robust and disease-resistant pig populations becomes a complementary strategy to the more conventional methods of biosecurity and vaccination. The objective of this study was to explore the ability of a panel of genetic markers and immunity parameters to predict the survival rates during a natural PRRSV outbreak. Ten-week-old female Duroc pigs (n = 129), obtained from 61 sows and 20 boars, were naturally infected with a highly pathogenic PRRSV genotype 1 strain. Prior to infection, piglets were screened for immunity parameters (IgG levels in plasma and SOX13 mRNA expression in blood) and genetic markers previously associated to PRRSV immune response and immunity traits. Additionally, the 20 boars were genotyped with a panel of 132 single nucleotide polymorphisms (SNPs). Survival analysis showed that mortality was significantly higher for animals with low basal IgG levels in plasma and/or high SOX13 mRNA expression in blood. The genotypes of sires for SNPs associated with IgG plasma levels, CRP in serum, percentage of γδ T cells, lymphocyte phagocytic capacity, total number of lymphocytes and leukocytes, and MCV and MCH were significantly associated with the number of surviving offspring. Furthermore, CD163 and GBP5 markers were also associated to piglet survival. The effects of these SNPs were polygenic and cumulative, survival decreased from 94 to 21% as more susceptible alleles were accumulated for the different markers. Our results confirmed the existence of genetic variability in survival after PRRSV infection and provided a set of genetic markers and immunity traits associated with PRRS resistance.

Stress Biomarkers in Pigs: Current Insights and Clinical Application

Our study aimed to contribute to the understanding of the stress process in pigs to better assess and control their stress levels. Nowadays, pigs in intensive farming are exposed to several stress factors, such as weaning, transportation, diseases and vaccinations. As a result, the animals experience significant stress responses and inflammatory reactions that affect their health, growth and productivity. Therefore, it is crucial to assess their stress levels, and the use of stress biomarkers could be useful in their evaluation. An up-to-date overview of the different biomarkers that can be used for the assessment of stress is given. It also discusses the methods used to investigate these biomarkers, particularly non-invasive approaches, such as saliva sampling, as practical tools for monitoring animal welfare. In conclusion, our study highlights the importance of using multiple biomarkers for a comprehensive evaluation of stress and points to the need for further research to standardize the sampling procedures and improve stress management in pig farming.

Multiplex Assay to Determine Acute Phase Proteins in Modified Live PRRSV Vaccinated Pigs

Acute phase protein (APP) response to vaccine challenges is an attractive alternative to natural infection for identifying pigs with increased disease resilience and monitoring the productive performance. Currently, the methods used for APP quantification are diverse and often based on techniques that use antibodies that are not necessarily pig specific. The objective of this work is the development of a method based on a UPLC-SRM/MS system for simultaneous determination of haptoglobin, apolipoprotein A1, C-reactive protein, pig-major acute protein, and serum amyloid A and its application in pigs to monitor the effect of a vaccine administered against porcine reproductive and respiratory syndrome virus (PRRSV). With the aim of tracing the complete analytical process for each proteotypic peptide, a synthetic QconCat polypeptide construct was designed. It was possible to develop an SRM method including haptoglobin, apolipoprotein A1, pig-MAP, and serum amyloid A1. The PRRSV vaccine only affected haptoglobin. The pigs with positive viremia tended to show higher values than negative pigs, reaching significant differences in the three haptoglobin SRM-detected peptides but not with the data acquired by immunoenzymatic and spectrophotometric assays. These results open the door to the use of SRM to accurately monitor APP changes in experimental pigs.

Biomarkers associated with vaccine-associated enhanced respiratory disease following influenza A virus infection in swine

Influenza A virus (IAV) is a major pathogen in the swine industry. Whole-inactivated virus (WIV) vaccines in swine are highly effective against homologous viruses but provide limited protection to antigenically divergent viruses and may lead to vaccine-associated enhanced respiratory disease (VAERD) after heterologous infection. Although VAERD is reproducible in laboratory studies, clinical diagnosis is challenging, as it would require both knowledge of prior vaccine history and evidence of severe disease by assessment of pathologic lesions at necropsy following infection with a heterologous virus. The objective of this study was to identify potential biomarkers for VAERD for antemortem clinical diagnosis. Naïve pigs were split into two groups, and one group was vaccinated with IAV WIV vaccine. All pigs were then challenged with a heterologous virus to induce VAERD in the vaccinated group and necropsied at 5 days post infection (dpi). Blood was collected on 0, 1, 3, and 5 dpi, and assessed by hematology, plasma chemistry, acute phase proteins, and citrullinated H3 histone (CitH3) assays. Additionally, cytokine and CitH3 levels were assessed in bronchoalveolar lavage fluid (BALF) collected at necropsy. Compared to nonvaccinated challenged pigs, blood collected from vaccinated and challenged (V/C) pigs with VAERD had elevated white blood cells and neutrophils, elevated C-reactive protein and haptoglobin acute phase proteins, and elevated CitH3. In BALF, the proinflammatory cytokine IL-8 and CitH3 were elevated in V/C pigs. In conclusion, a profile of elevated white blood cells and neutrophils, elevated C-reactive protein and haptoglobin, and elevated CitH3 may be relevant for a clinical antemortem IAV VAERD diagnosis.

Pig Acute Phase Proteins as Non-Antibody Systemic Biomarkers of Intracellular Infections

As an alternative to traditional serological markers, that is, antibodies, for serum-based specific diagnosis of infections, circulating non-antibody markers may be used to monitor active disease. Acute phase proteins (APPs) are a prominent class of such markers widely used for diagnosing ongoing inflammation and infection. In this chapter, basic theoretical and practical considerations on developing APP assays and using APPs as markers of ongoing infection are presented with a specific focus on intracellular infections in pigs. Examples on APP-based monitoring of infection in pigs with viruses such as porcine respiratory and reproductive syndrome virus (PRRSV), porcine endemic diarrhea virus (PEDV), and influenza A virus (IAV), as well as intracellular bacteria (Lawsonia intracellularis) and the protozoan intracellular parasites Toxoplasma gondii and Cryptosporidium parvum are presented, with an emphasis on major pig APPs C-reactive protein (CRP), haptoglobin, serum amyloid A (SAA), and pig major acute phase protein (pig-MAP). The performance of these APPs as biomarkers in a range of experimental infection studies in pigs is described as examples on their use for estimating the severity of infection, vaccine efficacy, herd health characterization, and differential diagnosis.

Effects of early postnatal gastric and colonic microbiota transplantation on piglet gut health

BACKGROUND

Diarrhea is a major cause of reduced growth and mortality in piglets during the suckling and weaning periods and poses a major threat to the global pig industry. Diarrhea and gut dysbiosis may in part be prevented via improved early postnatal microbial colonization of the gut. To secure better postnatal gut colonization, we hypothesized that transplantation of colonic or gastric content from healthy donors to newborn recipients would prevent diarrhea in the recipients in the post-weaning period. Our objective was to examine the impact of transplanting colonic or gastric content on health and growth parameters and paraclinical parameters in recipient single-housed piglets exposed to a weaning transition and challenged with enterotoxigenic Escherichia coli (ETEC).

METHODS

Seventy-two 1-day-old piglets were randomized to four groups: colonic microbiota transplantation (CMT, n = 18), colonic content filtrate transplantation (CcFT, n = 18), gastric microbiota transplantation (GMT, n = 18), or saline (CON, n = 18). Inoculations were given on d 2 and 3 of life, and all piglets were milk-fed until weaning (d 20) and shortly after challenged with ETEC (d 24). We assessed growth, diarrhea prevalence, ETEC concentration, organ weight, blood parameters, small intestinal morphology and histology, gut mucosal function, and microbiota composition and diversity.

RESULTS

Episodes of diarrhea were seen in all groups during both the milk- and the solid-feeding phase, possibly due to stress associated with single housing. However, CcFT showed lower diarrhea prevalence on d 27, 28, and 29 compared to CON (all P < 0.05). CcFT also showed a lower ETEC prevalence on d 27 (P < 0.05). CMT showed a higher alpha diversity and a difference in beta diversity compared to CON (P < 0.05). Growth and other paraclinical endpoints were similar across groups.

CONCLUSION

In conclusion, only CcFT reduced ETEC-related post-weaning diarrhea. However, the protective effect was marginal, suggesting that higher doses, more effective modalities of administration, longer treatment periods, and better donor quality should be explored by future research to optimize the protective effects of transplantation.

Acute phase proteins in cattle and swine: A review

The major acute phase proteins (APPs) in cattle are haptoglobin (Hp) and serum amyloid A (SAA), and in swine, are Hp, SAA, C-reactive protein (CRP), and Pig major acute phase protein (Pig-MAP). Many methodologic assays are presently available to measure these parameters, which are still being improved to increase their specificity, sensitivity, user-friendliness, and economic availability. In cattle, the main applications are the diagnosis and monitoring of frequent diseases such as mastitis and metritis in dairy cows and respiratory problems in young calves. In pigs, APPs are useful in the control of bacterial and viral infections, and they may be used at the slaughterhouse to monitor subclinical pathologies and improve food safety. The utility of APP in animal production must not be forgotten; optimization of protocols to improve performance, welfare, and nutrition may benefit from the use of APPs. Other sample types besides serum or plasma have potential uses; APP determination in milk is a powerful tool in the control of mastitis, saliva is a non-invasive sample type, and meat juice is easily obtained at the slaughterhouse. Increasing our knowledge of reference intervals and the influence of variables such as age, breed, sex, and the season is important. Finally, worldwide harmonization and standardization of analytical procedures will help to expand the use of APPs.

Biosecurity and Lairage Time versus Pork Meat Quality Traits in a Farm-Abattoir Continuum

The modern pig production chain is increasingly focused on biosecurity, quality, and safety of meat and is associated with many challenges impacting world meat markets, such as animal disease outbreaks and sanitary restrictions, trade regulations and quality requirements. To overcome such challenges and assure more consistent pork meat quality (and safety), there is a need to develop an effective and reliable monitoring system in a farm-abattoir continuum that can be based on selected biomarkers. This study assessed interrelations of selected stress and inflammation biomarkers (acute phase proteins (APP)) between farm biosecurity score versus pork meat quality traits after two different lairage periods. Briefly, the maximum recorded levels of stress hormones (436.2 and 241.2 ng/mL, for cortisol and Chromogranin A (CgA), respectively) and APP (389.4 and 400.9 μg/mL, Pig Major Acute Proteins (MAP) and Haptoglobin (Hp), respectively) at four commercial farms were within the recommended threshold values. Cortisol and APP were negatively correlated to the internal and total biosecurity scores of farms. The increase of level of both sets of biomarkers was found at bleeding (after transportation and lairage period), but with lower values after long (18-20 h) versus short (1-3 h) lairage lay-over time. In general, negative correlation was confirmed between stress and inflammation biomarkers and carcass/meat quality traits. The farm total biosecurity level significantly affected chilling yield, meat temperature, and a* value. Pig-MAP emerged as a good biomarker with a promising potential for assessment and anticipation of broad aspects in the pork meat chain. It can be used for detection of failures in the pig production system and might be incorporated in certification programs for the pork meat industry.

Inflammation and necrosis syndrome is associated with alterations in blood and metabolism in pigs

BACKGROUND

Swine inflammation and necrosis syndrome (SINS) can lead to significant clinical alterations at tail, ears, claws and other parts of the body in suckling piglets, weaners and fatteners. Clinical findings are associated with vasculitis, intima proliferation and thrombosis. The syndrome can be found in newborns, indicating a primarily endogenous aetiology. It has been hypothesized that SINS is triggered by gut-derived microbial-associated molecular patterns, causing derangements in liver metabolism and activity of peripheral white blood cells involving inflammation and blood haemostasis. In order to characterize these metabolic derangements of SINS for the first time, red and white blood counts, parameters of blood haemostasis, serum metabolites and acute phase proteins in the serum were analysed in 360 piglets, weaners and fatteners, each with significantly different SINS scores.

RESULTS

SINS scores and haematological/clinical chemical parameters were significantly associated (P < 0.05), especially in weaners and fatteners. Higher degrees of clinical SINS were associated with increased numbers of monocytes and neutrophils. Blood coagulation was altered in weaners and a thrombocytopenia was found in fatteners. Additionally, acute phase proteins, especially C-reactive protein and fibrinogen were increased in serum. Serum metabolites and serum liver enzymes were slightly altered. Aspartate transaminase levels overall exceeded physiological limit and increased in parallel with SINS scores in fatteners.

CONCLUSION

Clinical inflammation and necrosis at tail, ears, claws and other parts of the body were significantly associated with haematology and serum clinical chemistry, especially in weaners and fatteners. The involvement of inflammatory cells, blood coagulation, acute phase proteins and certain serum metabolites support the inflammatory-necrotising character of the syndrome and provide starting points for further studies to decipher its exact pathogenesis. The low to moderate variations seem less suitable for diagnostic use.

Acute phase protein pattern and antibody response in pigs experimentally infected with a moderate dose of Trichinella spiralis, T. britovi, and T. pseudospiralis

The aim of the present study was to evaluate the acute-phase protein (APP) response in three groups of pigs experimentally infected with a moderate infective dose, i.e. 1000 muscle larvae (ML) of Trichinella spiralis, 3000 ML of Trichinella britovi, and 2000 ML of Trichinella pseudospiralis. Over a 62-day period of infection, we examined the serum level and kinetics of the haptoglobin (Hp), C-reactive protein (CRP), serum amyloid A (SAA), and pig major acute-phase protein (pig-MAP). In addition, to better understand the immune response of pigs experimentally infected with three different species of Trichinella, the kinetics of IgG and IgM antibodies against excretory-secretory (ES) antigens of Trichinella ML were also investigated. In order to assess anti-Trichinella IgG dynamics, we used a commercial and an in-house ELISA based on both heterologous (T. spiralis) and homologous (T. spiralis, T. britovi, and T. pseudospiralis) Trichinella species ES antigens. Among the four APPs analyzed, the concentration of CRP and pig-MAP significantly increased only in T. britovi-infected swine when compared with control pigs. This took place as early as 6 days post-infection (dpi). Hp was the only APP whose concentration significantly increased in pigs infected with T. pseudospiralis, this occurring as late as on day 62 pi. Despite the statistical differences found, increases in pig-MAP, CRP, and Hp levels were rather mild and transitory; none of these proteins were found to be elevated in the serum of all experimental groups of pigs at the same time point after infection. Specific IgG antibodies against ES antigens of Trichinella ML were first detected by the commercial and in-house T. spiralis ML ES-antigen ELISAs on days 30, 36 and 36 pi in pigs experimentally infected with T. spiralis, T. britovi, and T. pseudospiralis, respectively. However, seroconversion in pigs experimentally infected with T. britovi was detected slightly earlier (30 dpi) when the ELISA based on homologous rather than heterologous ES antigens was applied. In serum samples from pigs infected with T. spiralis, statistically significant increases in the level of specific IgM antibodies against T. spiralis ML ES antigens were first detected on day 30 pi and after this time, their concentration began to decrease. No changes in the level of anti-Trichinella IgM were observed in T. britovi- or T. pseudospiralis-infected pigs throughout the entire period of the experiment.

Kinetics of single and dual simultaneous infection of pigs with swine influenza A virus and porcine reproductive and respiratory syndrome virus

Background

Simultaneous viral infections exhibit the phenomenon of viral interference, but understanding of the effect of one virus on another is limited.

Objective

Evaluate and compare clinical characteristics, immune and acute phase response, viral shedding and viral load in pigs singly and doubly inoculated with swine influenza A virus (swIAV) and porcine reproductive and respiratory syndrome virus (PRRSV).

Animals

Fifty‐four 7‐week‐old piglets.

Methods

Clinical status and gross lung lesions were scored. Titration of swIAV was carried out in Madin‐Darby canine kidney cells. The PRRSV RNA was quantified using a commercial qPCR kit. Antibodies were detected by hemagglutination inhibition assay and commercial ELISA. A lymphocyte proliferation assay was used to measure antigen‐specific T‐cell responses. Acute phase proteins were determined using ELISA.

Results

No differences were found between mean clinical scores, swIAV and PRRSV shedding, and magnitude of the humoral and T‐cell response between single‐inoculated and dual‐inoculated groups. Concentrations of C‐reactive protein and haptoglobin increased in PRRSV‐inoculated and coinoculated groups, whereas serum amyloid A concentration was increased in groups inoculated or coinoculated with swIAV. Mean swIAV TCID₅₀ titers in the lungs did not differ significantly between coinoculated and swIAV single‐inoculated pigs. A significantly higher mean copy number of PRRSV was found in the lungs of PRRSV only‐inoculated pigs at 2 day postinoculation (DPI). From 4 DPI, no significant differences in PRRSV load were identified.

Conclusions and Clinical Importance

Coinfection of pigs with swIAV and PRRSV did not potentiate clinical signs, lung lesions, immune response, and replication of the viruses in the respiratory tract.

ITRAQ-based quantitative proteomics reveals the first proteome profiles of piglets infected with porcine circovirus type 3

Porcine circovirus type 3 (PCV3) infection induces porcine dermatitis and nephropathy syndrome, reproductive failure, and multisystemic inflammatory lesions in piglets and sows. To better understand the host responses to PCV3 infection, isobaric tags for relative and absolute quantification (iTRAQ) labeling combined with LC-MS/MS analysis was used for quantitative determination of differentially regulated cellular proteins in the lungs of specific-pathogen-free piglets after 4 weeks of PCV3 infection. Totally, 3429 proteins were detected in three independent mass spectrometry analyses, of which 242 differential cellular proteins were significantly regulated, consisting of 100 upregulated proteins and 142 downregulated proteins in PCV3-infected group relative to control group. Bioinformatics analysis revealed that these higher or lower abundant proteins involved primarily metabolic processes, innate immune response, MHC-I and MHC-II components, and phagosome pathways. Ten genes encoding differentially regulated proteins were selected for investigation via real-time RT-PCR. The expression levels of six representative proteins, OAS1, Mx1, ISG15, IFIT3, SOD2, and HSP60, were further confirmed by Western blotting and immunohistochemistry. This study attempted for the first time to investigate the protein profile of PCV3-infected piglets using iTRAQ technology; our findings provide valuable information to better understand the mechanisms underlying the host responses to PCV3 infection in piglets. SIGNIFICANCE: Our study identified differentially abundant proteins related to a variety of potential signaling pathways in the lungs of PCV3-infected piglets. These findings provide valuable information to better understand the mechanisms of host responses to PCV3 infection.

Acute phase protein response to viral infection and vaccination

Organisms respond in multiple ways to microbial infections. Pathogen invasion tipically triggers an inflammatory response where acute phase proteins (APP) have a key role. Pentraxins (PTX) are a family of highly conserved APP that play a part in the host defense against infection. The larger proteins of the family are simply named pentraxins, while c-reactive proteins (CRP) and serum amyloid proteins (SAA, SAP) are known as short pentraxins. Although high APP levels have been broadly associated with bacterial infections, there is a growing body of evidence revealing increased PTX, CRP and SAP expression upon viral infection. Furthermore, CRP, PTX and SAP have shown their potential as diagnostic markers and predictors of disease outcome. Likewise, the measurement of APP levels can be valuable to determine the efficacy of antiviral therapies and vaccines. From the practical point of view, the ability of APP to reduce viral infectivity has been observed in several virus-host models. This has prompted investigation efforts to assess the role of acute phase response proteins as immunoregulatory molecules and their potential as therapeutic reagents. This work aims to present an overview of the APP response to viral infections reviewing the current knowledge in the field.

Identifying physiological measures of lifetime welfare status in pigs: exploring the usefulness of haptoglobin, C- reactive protein and hair cortisol sampled at the time of slaughter

BACKGROUND

Physiological measures indicative of the welfare status of animals during rearing could form part of an abattoir-based animal health and welfare assessment tool. A total of 66 pigs were used in this study, the aim of which was to assess how serum concentrations of haptoglobin (Hp) and C-reactive protein (CRP) (assessed in 51 pigs), and hair concentrations of cortisol (assessed in 65 pigs), measured at or close to slaughter, reflected welfare-related indicators recorded from the animal during its lifetime. These indicators were recorded at intervals between 7 and 21 weeks of age and included assigning scores for levels of tail and skin lesions, recording the presence or absence of certain health issues, and conducting qualitative behavioural assessments (QBA).

RESULTS

Pigs recorded as having tail lesions during their lifetime had higher hair cortisol levels than those with no tail lesions (tail lesions: 47.87 ± 3.34 pg/mg, no tail lesions: 42.20 ± 3.29 pg/mg, P = 0.023), and pigs recorded as having moderate or severe tail lesions had higher Hp levels than those with no or mild tail lesions (moderate/severe: 1.711 mg/ml ± 0.74, none/mild: 0.731 mg/ml ±0.10, P = 0.010). Pigs recorded as being lame during their lifetime tended to have higher hair cortisol levels than non-lame pigs (lame: 52.72 pg/mg ± 3.83, not lame: 43.07 pg/mg ± 2.69, P = 0.062). QBA scores were not associated with any of the physiological measures (P > 0.05). Receiver Operator Curve (ROC) analysis was also carried out to get a better understanding of the usefulness of the physiological measures in discriminating animals that had had welfare-related issues recorded during their lifetime from those that had not. Hair cortisol was determined as having 'moderate' accuracy in discriminating pigs that were tail bitten on-farm from unbitten pigs (AUC: 0.748) while Hp and CRP were determined to have no meaningful discriminatory ability (AUC < 0.600).

CONCLUSION

This research should be repeated on a larger scale, but the results suggest that hair cortisol measured at slaughter could provide insight into the welfare status of pigs during their lifetime. Hp may be a useful indicator of tail lesions in pigs. However, further research utilising a greater proportion of severely bitten pigs is required before conclusions can be drawn.

Pathogenicity of three genetically diverse strains of PRRSV Type 1 in specific pathogen free pigs

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The pathogenicity of two PRRSV-1 strains BOR59, ILI6 and 18794 was compared specific pathogen free pigs.

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The most pronounced clinical signs, the highest viremia and the earliest acute phase proteins response were in pigs infected with BOR59 strain.

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BOR59 strain can be considered a highly virulent strain, while the virulence of strain ILI6 was intermediate between BOR59 and 18794.

Studies from Eastern European countries proved that porcine reproductive and respiratory syndrome virus Type 1 (PRRSV-1) harbours high genetic diversity and that genetically divergent subtypes 2–4 circulate in this area.

In the present study, we compared the pathogenicity of two different PRRSV-1 subtype 2 strains and a strain representing PRRSV-1 subtype 1. Four groups of 8-week-old specific pathogen free pigs were either infected with subtype 2 strain ILI6, subtype 2 strain or BOR59, subtype 1 strain 18794, or mock inoculated.

The most pronounced clinical signs were observed in pigs infected with BOR59. Pigs from both subtype 2 strain infected groups exhibited significantly elevated mean body temperatures on DPI 2 compared to the other two groups, the difference remaining significant up to DPI 13 for the BOR59 group, only. The pigs in the latter group also displayed significantly highest levels of early viremia together with the most rapid APP response.

Overall, the results indicated that BOR59 strain can be considered a highly pathogenic strain, similarly to subtype 3 strains Lena and SU1-bel, while the virulence of the other subtype 2 strain ILI6 was intermediate between BOR59 and subtype 1 strain.