Biomarker biological activity marker

Much of the discussion about disease biomarkers is in the context of markers that measure some aspect of disease status, extent, or activity. Such biomarkers are often proposed for use in early detection of disease or as a surrogate endpoint for evaluating prevention or therapeutic interventions. The validation of such biomarkers is difficult for a variety of reasons, but particularly because the molecular pathogenesis of many diseases is incompletely understood, and hence it is not possible to establish the biological relevance of a measure of disease status. 

Proteomics have been used to develop biomarkers. This is achieved by comparative analysis of protein expression in healthy and diseased tissues to identify expressed proteins to be used as new markers, by analysis of secreted proteins in cell lines and primary cultures, and by direct serum protein profiling. MALDI seems to be a good technique for direct protein analysis in biological fluids (e.g., the identification of the small proteins-defensin 1, 2 and 3 as related to the anti-HIV-1 activity of CD8 antiviral factor). 

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