Borrelia burgdorferi chemotaxis toward tick protein Salp12 contributes to acquisition

Abstract Lyme diseaseis a common tick-borne infection caused by the spirochete Borrelia burgdorferi sensustricto (s.s.). B. burgdorferi s.s. may utilize chemotaxis, the directional migration towards or away from a chemical stimulus, for transmission, acquisition, and infection. However, the specific signals recognized by the spirochete for these events have not been defined. In this study, we identify an Ixodes scapularis salivary glandprotein, Salp12, that is a chemoattractant for the spirochete. We demonstrate that Salp12 is expressed in the I. scapularis salivary glandsand midgutand expression is not impacted by B. burgdorferi s.s. infection. Knockdown of Salp12 in the salivary glandsor passive immunizationagainst Salp12 reduces acquisition of the spirochete by ticks but acquisition is not completely prevented. Knockdown does not impact transmission of B. burgdorferi s.s. This work suggests a new role for chemotaxisin acquisition of the spirochete and suggests that recognition of Salp12 contributes to this phenomenon.