Molecular biomarkers as a prognostic tool for clinical courses of experimental autoimmune encephalomyelitis in rats immunized with spinal cord homogenate

Abstract

Experimental autoimmune encephalomyelitis (EAE) in inbred rodents commonly shows different clinical courses, so that the diseased animals can be clustered into four groups: mild. moderate, severe and lethal. Our aim was to determine biomolecular markers in the preclinical phase of EAE that allow the prediction of clinical course. Methods: Female Dark Agouti rats were immunized with spinal cord homogenate without adjuvant and examined for four weeks for clinical signs of EAE. Cells and sera from blood collected on days 0, 3, and 7 after immunization were processed for detection of proinflammatory cytokines (IL-1, IL-6, TNF, and IFN) by "real-time" RT-PCR and ELISA, respectively. Results: Induction of EAE resulted in the downregulation of IFN and TNF in the preclinical phase of disease, whereas IL-1 and IL-6 expression levels were unaffected. However, there was no correlation between the relative expression of IFN or TNF and the cumulative clinical score (sum of daily clinical scores), suggesting that they are not predictive markers of EAE severity. Our preliminary results that suggest a negative correlation between IL-1 expression level before EAE induction and cumulative score require further justification. Conclusion: The proinflammatory cytokines investigated so far in our study cannot be considered as good biomarkers of EAE severity. However, the downregulation of IFN and TNF in the blood cells during the asymptomatic phase of EAE suggests that they enter the central nervous system early from the bloodstream, which argues for the study of chemokine and/or chemokine receptors expression as potential biomarkers for the clinical courses of EAE.