Protein biomarkers that are secreted into the blood from infected host cells following infection may become the basis of early and specific disease diagnostics. To identify such mechanistic biomarkers, the human macrophage cell line THP-1 was infected with Brucella abortus 2308 or 544 for 20 hours. Light membrane vesicles were prepared from infected and control cultures and the secretory protein-enriched soluble content recovered for proteomics analysis. Statistical analysis identified 184 significantly differentially expressed proteins from the infected macrophages. Upregulated proteins were used for MRM qualication. One hundred forty four (144) peptides corresponding to 65 proteins were monitored.