Borrelia burgdorferi surface-localized proteins expressed during persistent murine infection are conserved among diverse Borrelia spp.

Borrelia burgdorferi, the causative agent of Lyme disease in the United States, regulates numerous genes encoding lipoproteins on linear plasmid 54 in response to environmental cues. We analyzed a subset of these genes/proteins that were historically categorized as paralogous gene family 54 (BBA64, BBA65, BBA66, BBA68, BBA69, BBA70, BBA71, and BBA73) and found that the expression of several genes was influenced by the sigma(N)-sigma(S) regulatory cascade at the level of transcription and protein synthesis. Moreover, we established in this and a previous study that BBA65, BBA66, BBA69, BBA71, and BBA73 are temporally expressed during persistent infection of immunocompetent mice, as determined by quantitative real time-PCR of ear tissue, by enzyme-linked immunosorbent assay, and by immunoblotting. Correspondingly, BBA65, BBA66, BBA71, and BBA73 proteins were detectable in infectious B. burgdorferi B31 isolates but undetectable in noninfectious isolates. BBA65, BBA66, BBA71, and BBA73 proteins were also found to partition into the Triton X-114 detergent phase and were sensitive to protease treatment of intact cells, indicating that they are membrane associated and surface localized. Lastly, Southern blotting and PCR with specific gene primer/probes for BBA64, BBA65, BBA66, BBA71, and BBA73 suggest that many of these genes are conserved among the B. burgdorferi sensu lato isolates and the relapsing-fever Borrelia species. Together, the data presented suggest that these genes may play a part in Borrelia infection and/or pathogenicity that could extend beyond the sensu lato group.