A sensitive immunoassay for the quantitation of Pig-MAP in pig saliva samples

The purpose of the study is to develop a sensitive assay for the proper quantification of the acute phase protein Pig-MAP in pig saliva samples. A time-resolved immunofluorometric assay (TR-IFMA) was developed using two pig-MAP-specific monoclonal antibodies. The limit of detection of the assay was 4 ng/mL, enough to measure pig-MAP concentration in saliva. Precision was evaluated for saliva samples of low, medium and high concentration, with inter assay CV of 4-14 % and inter-assay CV of 8-20 %. The assay kept linearity under dilution and a method comparison study performed with serum samples showed good correlation with ELISA. Median Pig-MAP concentration in saliva from healthy animals was 19 ng/mL whereas in pigs with different inflammatory conditions was 11 times higher. In the same animals median pig-MAP serum concentrations were 0.72 mg/mL in the healthy group and 4.61 in the diseased group. The Spearman coefficient of correlation between Pig-MAP concentration in serum and saliva was of 0.72. A correlation was also observed between the salivary concentration of pig-MAP and other two acute phase proteins such as haptoglobin (r = 0.62) or C-reactive protein (r = 0.65). The concentration of Pig-MAP in saliva of pigs with severe respiratory disease decreased significantly from a median value of 128 ng/mL at the time of disease detection to 8 ng/mL after 1 day of antibiotic therapy. Studies performed show that pig-MAP is present in saliva and this specimen may be an alternative to serum for pig-MAP quantification.