Investigating the prophylactic potential of Borrelia burgdorferi outer membrane vesicles

The causative agent of Lyme disease, Borrelia burgdorferi (Bb), is responsible for the most prevalent tick-borne illness in the Northern Hemisphere. Bb exists in an enzootic cycle, transitioning between an Ixodes tick vector and vertebrate hosts. These environments require Bb to express different surface-exposed proteins to allow for survival in the tick and vertebrate host, which includes persistent infection. Bb has been shown to produce outer membrane vesicles (OMVs) in vivo and in vitro. However, during in vitro culture, Bb typically expresses genes involved in survival in the tick vector. We used a strain we recently developed that produces large amounts of OMVs and over-expresses proteins involved in vertebrate infection through the induction of the alternative sigma factor RpoS. Our results from mass-spectrometry and western blot showed that when RpoS is induced, BbOMVs contain outer-surface proteins such as OspC, which is vital for vertebrate infection. OspA, a tick specific protein, was detected in BbOMVs during RpoS over-expression. As OspA, along with other tick-specific proteins can induce autoimmune pathologies, we engineered suicide vectors to knock out ospA, ospD, and napA and vlsE which is required for persistent infection. These findings will help further studies to determine the prophylactic potential of BbOMVs.