Porcine serum amyloid A3 is expressed in extrahepatic tissues and facilitates viral replication during porcine respiratory and reproductive syndrome virus infection

Transcriptomic Analysis of the Porcine Gut in Response to Heat Stress and Dietary Soluble Fiber from Beet Pulp

This study aimed to investigate the impact of heat stress (HS) and the effects of dietary soluble fiber from beet pulp (BP) on gene expression (differentially expressed genes, DEGs) of the porcine jejunum. Out of the 82 DEGs, 47 genes were up-regulated, and 35 genes were downregulated between treatments. The gene ontology (GO) enrichment analysis showed that the DEGs were related mainly to the actin cytoskeleton organization and muscle structure development in biological processes, cytoplasm, stress fibers, Z disc, cytoskeleton, and the extracellular regions in cellular composition, and actin binding, calcium ion binding, actin filament binding, and pyridoxal phosphate binding in the molecular function. The KEGG pathway analysis showed that the DEGs were involved in hypertrophic cardiomyopathy, dilated cardiomyopathy, vascular smooth muscle contraction, regulation of actin cytoskeleton, mucin type O-glycan biosynthesis, and African trypanosomiasis. Several of the genes (HSPB6, HSP70, TPM1, TAGLN, CCL4) in the HS group were involved in cellular oxidative stress, immune responses, and cellular differentiation. In contrast, the DEGs in the dietary BP group were related to intestinal epithelium integrity and immune response to pathogens, including S100A2, GCNT3, LYZ, SCGB1A1, SAA3, and ST3GAL1. These findings might help understand the HS response and the effect of dietary fiber (DF) regarding HS and be a valuable reference for future studies.

Targeted mass spectrometry for Serum Amyloid A (SAA) isoform profiling in sequential blood samples from experimentally Staphylococcus aureus infected pigs

Serum amyloid A (SAA) is a well-described acute phase protein induced during the acute phase response (APR) to infection. Four isoform specific genes are found in most mammals. Depending on species, SAA3 and SAA4 are generally preferentially expressed extrahepatically whereas SAA1 and SAA2 are hepatic isoforms dominating the SAA serum pool. Little is known about how specific infections affect the serum SAA isoform profile, as SAA isoform discriminating antibodies are not generally available. An antibody independent, quantitative targeted MS method (Selected Reaction Monitoring, SRM) based on available information on porcine SAA isoform genes was developed and used to profile SAA in serum samples from pigs experimentally infected with Staphylococcus aureus (Sa). While results suggest SAA2 as the main circulating porcine SAA isoform, induced around 10 times compared to non-infected controls, total SAA serum concentrations reached only around 4 μg/mL, much lower than established previously by immunoassays. This might suggest that SAA isoform variants not detected by the SRM method might be present in porcine serum. The assay allows monitoring host responses to experimental infections, infectious diseases and inflammation states in the pig at an unprecedented level of detail. It can also be used in a non-calibrated (relative quantification) format. SIGNIFICANCE: We developed an SRM MS method which for the first time allowed the specific quantification of each of the circulating porcine SAA isoforms (SAA2, SAA3, SAA4). It was found that SAA2 is the dominating circulating isoform of SAA in the pig and that, during the acute phase response to Sa infection SAA2, SAA3 and SAA4 are induced approx. 10, 15 and 2 times, respectively. Absolute levels of the isoforms as determined by SRM MS were much lower than reported previously for total SAA quantified by immunosassays, suggesting the existence of hitherto non-described SAA variants. SRM MS holds great promise for the study of the basic biology of SAA isoforms with the potential to study an even broader range of SAA variants.

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.