Gaining knowledge about biomarkers of the immune system and inflammation in the saliva of pigs: The case of myeloperoxidase, S100A12, and ITIH4.

An assay for the measurement of myeloperoxidase (Mpx) in porcine saliva was developed and validated, and factors influencing Mpx and another two biomarkers of inflammation and immune system, the protein S100A12 and the inter-alpha-trypsin inhibitor heavy chain 4 (ITIH4), were studied. The spectrophotometric method for Mpx measurement validated in this assay showed an adequate analytical performance including precision and accuracy. When a group of twenty healthy pigs was sampled every 4 h from 8 a.m. until 8 p.m., Mpx and S100A12 showed significant increases at 4 p.m., whereas ITIH4 concentration showed a significant decrease at 12 a.m. Increases were also seen in salivary Mpx, S100A12, and ITIH4 levels 24 h after the intramuscular administration of Escherichia coli lipopolysaccharide in five pigs; whereas in a non-septic inflammation after the subcutaneous administration of turpentine oil to five pigs changes were seen in S100A12 at 3 h and in ITIH4 at 48 h. When a stressful situation consisting of the transportation and stay of 4 h to a slaughterhouse of 24 pigs was performed, all analytes were increased after 4 h of lairage in the slaughterhouse compared with the values that were obtained the day before at the same time of the day. Mpx can be measured in the saliva of pigs with the automated assay described in this report. Mpx, S100A12, and ITIH4 salivary levels can change depending on the hour of the day in which the sample is taken, and increases can be produced due to sepsis, non-septic inflammation and stress.