FIGURE 1. Protein interaction involved in Borrelia burgdorferi infection of mammalian hosts transmitted via Ixodes ticks.

B. burgdorferi (Borrelia) is transmitted to the mammalian dermis at the tick-bite site. A spirochete outer surface protein (OspC), via interaction with a tick salivary gland protein (Salp15), carries the latter protein in the dermis where it assists the pathogen evasion of host immune insults. Protection from the vertebrate immune system, as well as dissemination through extracellular matrix or vasculature, is also mediated by interactions between additional sets of B. burgdorferi proteins, like BBK32, CRASP1–5, VlsE, Erp proteins, OspC, BBA70, and Enolase amongst others. The pathogen also uses its chemotaxis machinery system, including several Che proteins to disseminate into the host. The bacteria also use its own protease, BbHtrA, to degrade host extracellular matrix components and promote the infection. During and/or after dissemination to distant tissue locations, spirochetes interact with specific host molecules like matrix metalloproteases (MMP), collagen, or integrins and use specific adhesins like BBK32, DBPA/DBPB, P66, RevA, BBA33, BBB07, BB0172, Erp proteins, and Lmp1, amongst others to colonise the tissues and to facilitate its persistence in the infected organs