Regulation and expression of bba66 encoding an immunogenic infection‐associated lipoprotein in Borrelia burgdorferi

Abstract

SummaryWhen Borrelia burgdorferi (Bb) is transmitted from a tick vector to a mammalian host the spirochaete alters gene expression, allowing for adaptation to the new host. We evaluated the regulation of paralogous gene family (pgf) 54 members in response to environmental cues and focused our efforts on determining the molecular mechanisms influencing bba66 expression. By qRT-PCR, bba65, bba66, bba71 and bba73 displayed regulation similar to ospC under mammalian-like conditions. Of the pgf 54 members, bba66 demonstrated the greatest and second greatest change in expression in response to pH or temperature shift respectively. Furthermore, Bb-infected mice and patients with early disseminated Lyme disease produced detectable antibodies to BBA66. A protein(s) active in Bb at pH 7 was able to interact with the bba66 upstream region and was specific as bba64 and ospC promoters were unable to outcompete for binding. bba66 promoter mapping revealed putative s 70 and s S consensus sequences, enabling us to narrow the protein binding site to a region within an imperfect inverted repeat upstream of the -35 region. Moreover, BBA66 production is associated with an infectious phenotype, and loss of either s N or s S resulted in loss of BBA66. Promoter-GFP fusion analysis indicated that the s 70 and/or s S consensus sequences alone were not sufficient to initiate transcription and a portion of the upstream inverted repeat was required. These results suggest a primary role for BBA66 in Bb transmission and infection.

Transcriptional interplay among the regulators Rrp2, RpoN and RpoS in Borrelia burgdorferi

“…Even for those genes categorized as being regulated by both RpoN and RpoS, the relative changes in gene expression were slight. Many genes that were shown to be significantly induced by RpoS, including bba25 (dbpB), bba66 and bb0844 (Caimano et al, 2007;Clifton et al, 2006;Hubner et al, 2001), were regulated only moderately (less than fourfold) by RpoS in their microarray experiments (Fisher et al, 2005). In addition, bba24 (dbpA) was found to be induced 1.6-fold by RpoS alone, but not by RpoN, which is inconsistent with previous reports (Hubner et al, 2001;Yang et al, 2003a).…”

“…Plasmid lp54 has been implicated as being important for the survival of B. burgdorferi in both tick and mammalian hosts, largely because of the presence of the ospAB and dbpBA operons (Caimano et al, 2005;Hagman et al, 1998;Neelakanta et al, 2007;Shi et al, 2008;Yang et al, 2004). Many other genes encoded on lp54 have been found to be differentially regulated in response to temperature, pH and other mammalian-derived signals, which are presumed to be mediated, at least in part, by RpoS (Caimano et al, 2005;Clifton et al, 2006;Ojaimi et al, 2003;Revel et al, 2002). Consistent with these previous findings, our data provided further evidence that 22 lp54-encoded genes are regulated by RpoS.…”

Role of the BBA64 Locus of Borrelia burgdorferi in Early Stages of Infectivity in a Murine Model of Lyme Disease

“…To test the contribution of the BBA64 gene to the infectivity of B. burgdorferi for the mammalian host, it was necessary to confirm if different environmental signals induced comparable levels of expression of pgf 54 members in the strains to be used in the infectivity analysis (12,22,43). Immunoblot analysis using monospecific rat anti-BBA64 or anti-BBA66 (5) or monospecific mouse anti-BBA65 antibodies was used to detect the levels of these proteins.…”

“…Members of pgf 54 that are clustered on the right terminal region of lp54 are a part of the lp54-specific "transcriptome" observed in response to exposure of B. burgdorferi to multiple mammalian host-specific signals (2,11,21,44,45,53,66). Among these pgf 54 members, BBA64, BBA65, BBA66, and BBA73 have been shown to be transcriptionally elevated in response to mammalian host-specific pH (7.0) or temperature (35°C) present in fed ticks (12,44,53). This is in contrast to a lack of expression of BBA64 and BBA66 at pH 8.0 and 23°C, mimicking the conditions associated with unfed ticks (66).…”

“…A recent study demonstrated the presence of antibodies against BBA64 and BBA66 in the serum of mice experimentally infected with B. burgdorferi and in serum samples of patients diagnosed with early, disseminated Lyme disease (42). Moreover, the temporal expression of various members of the pgf 54 in an infected mammalian host was also attributed to the involvement of multiple regulatory pathways (12,22). Taken together, these observations suggest that BBA64 may play a role in B. burgdorferi infection either independently or in association with other members of the pgf 54.…”