Searching for foreign antigens as possible triggering factors of autoimmunity: Torque Teno virus DNA prevalence is elevated in sera of patients with bullous pemphigoid.

OBJECTIVE: The Torque Teno virus (TTV), a member of virus genus Anellovirus has been shown to be commonly present in humans, yet without detectable pathogenicity. Recent studies imply that TTV may contribute to provoke autoimmune progresses in systemic lupus erythematosus and idiopathic inflammatory myopathies. We aimed to study the presence of TTV in a group of patients with autoimmune bullous diseases with a further goal to identify long-lasting foreign antigen, such as TTV as possible triggers of skin-specific autoimmunity. PATIENTS AND METHODS: We performed in silico research to study similarities between known TTV sequences and antigens of bullous pemphigoid (BP), pemphigus vulgaris (PV) and dermatitis herpetiformis (DH). Basic Local Alignment Search Tool results showed matching regions for the major BP antigens BP180 and BP230, PV antigen desmoglein 3 and DH antigen transglutaminase 3 and disclosed overlapping, antigen-predicted sequences only for BP180 regions. We also assessed the prevalence of TTV in these disorders and compared them with the results from two healthy blood donor groups (group 1: sex- and age-matched for the general bullous group, n = 95; group 2: sex- and age-matched for BP, n = 50). Furthermore, we assayed lymphocytes from four TTV DNA and BP180 NC16A blot-positive BP patients and three controls in a standard lymphocyte transformation test with a TTV peptide from the conserved ORF(Open Reading Frame)1/N22 region.
RESULTS: We found that the detection rate of TTV was comparable with that in healthy controls in the group of PV (19/33); whereas detection rates in DH showed a slight, but not significant tendency for elevation (17/20). Contrary, the TTV prevalence in BP patients was significantly elevated (group 1: 36/40 vs group 2: 31/50, P < 0.032). Lymphocytes from all four virus-positive BP patients heavily reacted to TTV peptide while two of the three healthy controls have shown not to recognize the viral sequences. Only the TTV carrier healthy control had a minor reaction at lowest peptide concentration. The combined in silico, polymerse chain reaction and in vitro cell assay data of the present study indicate that a TTV persistence may contribute to the pathogenesis of BP.