Enhanced immune reactivity in MS patients in comparison with healthy control subjects as identified by systematic studies [34, 35] ; consensus in other proteins to the EBV sequence given by * for identical amino acid, ? for similar amino acid (conservative exchange), and / for missing amino acid; one additional homology in vaccinia virus regulation within the cells via reduced levels of glutathione peroxidase [10] . In MS there is still another environmental risk factor, namely, suboptimal levels of bio-active vitamin D [4] , which, as demonstrated in rat astrocytes, may impair via c-glutamyl transpeptidase intra-cellular glutathione levels [56] . Table 3 MS-associated pathogens and homologies in proteins thereof to candidate epitopes No. 1 (EBV EBNA1, putative T reg ) and No. 2 (HERV-W) * for identical amino acid; ? = conserved amino acid exchange; / = missing amino acid; arabic numbers for additional amino acids: 1 = TEE; 2 = AG; 3 = QKE; 4 = YCK; 5 = AT; 6 = V; 7 = V; 8 = LAT Pathogens against which higher antibody concentrations were observed as compared with control individuals. Homologies to both epitopes were also found in the following pathogens causing respiratory and gastrointestinal diseases: Bordetella parapertussis, Corynebacterium diphtheriae, cytomegalo virus, Haemophilus influenzae, human corona virus, human rota virus, Mycobacterium tuberculosis (also M. bovis, strain BCG), Salmonella enterica, Pseudomonas aeruginosa, Serratia marcescens, A and in two parasites causing gastrointestinal infections: Entamoeba histolytica, Giardia lamblia Proteins with homologies to epitope 1/epitope 2, respectively: adeno virus: DNA stabilization protein/protein V; Chlamydia pneumoniae: hypothetical protein cpB U609/hypothetical protein; Epstein-Barr virus: EBNA1/BBLF2/BBLF3; herpes simplex-1: tegument/tegument; herpes simplex-2: tegument/tegument; HHV-6: tegument/major capsid; measles virus: nucleoprotein/nucleoprotein; Mycoplasma pneumoniae: phosphate import ATP-binding protein pstB/enolase; parainfluenza-2: large protein/nucleocapsid; RSV: fusion protein precursor/glycoprotein; rubella: RNA-directed RNA polymerase/E1; vaccinia: 14K membrane protein/putative DNA-binding core; varicella virus: tegument/tegument In cell culture experiments, gangliosides of the neolacto series, such as LM1, were identified as possible relevant mediators as they suppress HERV genes [10] and induce lytic replication cycles in cells latently infected with EBV [57, 58] , thereby releasing a viral antigen which would be readily recognisable by the specific immune system. The failure of such protective mechanisms would facilitate an uncontrolled establishment of the observed extensive EBV infection of brain lymphatic tissue in MS, albeit only at a low level of virus activity [59] [60] [61] [62] . The specificity of the process for the brain may be associated with the high content of gangliosides in nervous tissue, as other gangliosides may antagonize the activity of those that possibly protect against MS.