Association of Mycobacterium avium subsp. paratuberculosis with multiple sclerosis in Sardinian patients

Abstract

Mycobacterium avium subsp. paratuberculosis (MAP) infection is highly spread in the ruminant herds of Sardinia, in the Western Mediterranean. The objective of this study was to investigate prevalence of MAP infection in association with Multiple Sclerosis (MS) using clinical specimen from patients and controls. We analyzed samples for the presence of MAP specific DNA and to demonstrate humoral response to a MAP protein (MAP2694), a predicted homologue of the T-cell receptor gamma-chain/complement component 1 of the host. We found presence of MAP DNA in 42% of the MS patients and an extremely significant humoral immune response revealed by the MS patients against the MAP protein. In our opinion, this is the first report that significantly associates MAP infection with MS. Further studies will be required to confirm if MAP could be one of the triggers of MS, according to the molecular mimicry theory, in susceptible (and genetically at risk) individuals.

Figure 1. Blast alignments with masking-off segments of the query sequence that have low compositional complexity.

Results show region of identity, strongly similar amino acids with a plus (+) and missing region in dashes (–). Query sequence is MAP2694.

Figure 2. Computational prediction of the MAP2694 structure and properties such as different helices and turns, hydrophobicity, antigenicity and surface probability, etc. using Protean software from the DNAstar package (DNAstar Inc., Madison, USA).

In the inset is the highlighted antigenic index value which corresponded to the homology between MAP2964 (Aa 301-209) and T-cell receptor gamma/complement component 1.

Figure 3. Evaluation of serum samples against MAP2694 recombinant protein.

MS patients sera are shown in the left column whereas Healthy Controls sera are shown in the right column. Data are presented as OD values observed in ELISA, as also described in the text. Data from a representative experiment out of three are shown. The mean value for each group is indicated by a thick horizontal line. IS900 PCR positive samples are indicated as black solid figures.

Figure 4. AUC-ROC Test.

Evaluation of serum samples from 50 MS patients (right column) and 56 healthy controls (left column) against MAP2694 recombinant protein by the AUC-ROC test. The horizontal blue line highlights the cut-off value(s) which gives a specificity of 25%. Data are presented as OD values observed in ELISA. Area under curve (AUC) = 0,686; P = 0,0003.