The clinical potential of blood-proteomics in multiple sclerosis

The aetiology of multiple sclerosis (MS) remains unknown. This hampers molecular diagnosis and the discovery of bio-molecular markers. Consequently, MS diagnostic procedures are complex and criteria for assessing therapeutic efficacy are controversial, suggesting that a pathophysiological rather than an aetiological approach to the disease would be more appropriate. In this regard, blood-proteomics represents a still-unexplored tool. We investigated the potential of proteomics as applied to peripheral blood mononuclear cells (PBMCs) for differentiating treatment-naive RR-MS patients from healthy controls and from IFN-treated RR-MS patients.

A comparative analysis of PBMC proteins isolated from 13 unselected IFN-treated RR-MS patients, 6 IFN-untreated RR-MS patients and 14 matched healthy controls was performed using two-dimensional gel electrophoresis and MALDI-TOF mass spectrometry. We considered the volume of each spot, expressed as a percentage of the total volume of all spots in the gel. Heuristic clustering was applied to a composite population made up of a random sequence of gels from the different groups in comparison. For the differentially expressed proteins, we applied the Student's t-test to identify only those down- or up-regulated at least 2.5-fold [Ratio(R) ≥ 2.5] with respect to the homologous spots of the compared groups.

Rho-GDI2, Rab2 and Cofilin1 were found to be associated with down-regulated and naïve group phenotypes; Cortactin and Fibrinogen beta-Chain Precursor were found to be associated with down-regulated and group-related IFN-treated RR-MS phenotypes. Thus, by means of similarity analysis, the proteomes were homogeneously segregated into three distinct groups corresponding to naive, IFN-treated and healthy control subjects. Interestingly, no separation was found between IFN-treated and healthy controls. Moreover, the molecular phenotypes were consistent with disease pathogenesis.

We demonstrated for the first time, albeit only with preliminary data, the aprioristic possibility of distinguishing naive and IFN-treated MS groups from controls, and naive from IFN-treated MS patients using a blood sample-based methodology (i.e. proteomics) alone. The functional profile of the identified molecules provides new pathophysiological insight into MS. Future development of these techniques could open up novel applications in terms of molecular diagnosis and therapy monitoring in MS patients.