The infectious etiology of the antiphospholipid syndrome: links between infection and autoimmunity

Like many other autoimmune diseases, the antiphospholipid syndrome (APS) is considered as of a multifactorial etiology, mainly genetic susceptibility coinciding with environmental triggers, of which infectious agents are considered most prominent. Different clinical and experimental studies of the β2 glycoprotein I (β2GPI) molecule, one of the target autoantigens in APS, have linked infection to the development of APS. Using a peptide phage library, it has been shown that target epitopes of β2GPI share similarities with common infectious pathogens. Also, circulating anti-β2GPI antibodies have been identified in the sera of patients with different infectious conditions, and have been associated with various clinical APS manifestations. Molecular mimicry as a key mechanism linking infection and APS has been demonstrated in experimental models. In these studies, APS was induced by immunization of mice to various microbial pathogens. Anti-β2GPI titers were found to be especially high following immunization with Haemophilus influenzae, Neisseria gonorrheae or tetanus toxoid. These findings contribute greatly to the understanding of APS pathogenesis, as well as create new directions for therapy modalities, namely specific peptide toleragens and antimicrobial treatment.