Giant cell arteritis, infections and biologics

To the editor,

Numerous infectious agents have been implicated in the aetiology and/or pathogenesis of systemic vasculitides through direct damage of the vessel wall or autoimmune disorders. Mechanisms by which pathogens cause autoimmunity may include molecular mimicry (cross-reactivity between pathogen-derived and self-derived epitopes), epitope spreading (the immune response to a persisting pathogen), bystander activation (non-specific activation of autoimmune cells by the inflammatory environment during infection) or immune response to cryptic antigens (subdominant epitopes which are normally hidden from T-cell recognition).1 The causative role of infectious agents is clearly established in polyarteritis nodosa and cryoglobulinemic vasculitis that are commonly associated with hepatitis B virus and hepatitis C virus (HCV), respectively. Microbial pathogens may probably contribute to the development of other systemic vasculitides as well. However, the evidence for a definitive link between infection and induced autoimmunity in many vasculitides is less strong or lacking. Epidemiological studies showing an...