Integrins avb3 and a5b1 Mediate Attachment of Lyme Disease Spirochetes to Human Cells

Borrelia burgdorferi (sensu lato), the agent of Lyme disease, is able to cause chronic, multisystemic infections in human and animal hosts. Attachment of the spirochete to host cells is likely to be important for the colonization of diverse tissues. The platelet-specific integrin aIIbb3 was previously identified as a receptor for all three species of Lyme disease spirochetes (B. burgdorferi sensu stricto, B. garinii, and B. afzelii). Here we show that B. burgdorferi also recognizes the widely expressed integrins avb3 and a5b1, known as the vitronectin and fibronectin receptors, respectively. Three representatives of each species of Lyme disease spirochete were tested for the ability to bind to purified avb3 and a5b1. All of the strains tested bound to at least one integrin. Binding to one integrin was not always predictive of binding to other integrins, and several different integrin preference profiles were identified. Attachment of the infectious B. burgdorferi strain N40 to purified avb3 and a5b1 was inhibited by RGD peptides and the appropriate receptor-specific antibodies. Binding to avb3 was also shown by using a transfected cell line that expresses this receptor but not aIIbb3. Attachment of B. burgdorferi N40 to human erythroleukemia cells and to human saphenous vein endothelial cells was mediated by both a5b1 and avb3. Our results show that multiple integrins mediate attachment of Lyme disease spirochetes to host cells.