Analysis of soluble CD14 and its use as a biomarker in neonatal foals with septicemia and horses with recurrent airway obstruction

Soluble CD14 (sCD14) binds bacterial lipopolysaccharide (LPS) and acts as an anti-inflammatory LPS-inhibitor in vivo. In humans, sCD14 is one of the soluble biomarkers used for various inflammatory diseases and conditions, however, sCD14 assays have not yet been evaluated in horses. Here, we developed and optimized a bead-based assay for the quantification of sCD14 in horses. The assay was then used to determine native sCD14 concentrations in serum from healthy and septic foals, in the colostrum of healthy mares and in plasma from adult horses with recurrent airway obstruction (RAO) and control horses. Healthy foals and adult horses had sCD14 concentrations in serum or plasma in the high ng/ml range. The concentration of sCD14 in colostrum samples from healthy mares was in the μg/ml range. Foals with septicemia and adult horses with RAO had significantly higher sCD14 concentrations in their circulation than the respective control groups. The findings suggest that sCD14 can become a valuable biomarker for neonatal septicemia, RAO and possibly also for other inflammatory diseases in horses. Further studies and larger samples numbers are required to determine normal sCD14 concentration ranges and those that are indicative of disease progression, severity or prognosis.