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Two regulatory elements required for enhancing ospA expression in Borrelia burgdorferi grown in vitro but repressing its expression during mammalian infection.

ABSTRACT: During cycling between the tick vector and a mammal, the Lyme disease spirochaete Borrelia burgdorferi must coordinate expression of outer-surface proteins (Osps) A and B to quickly respond to environmental changes. The pathogen abundantly produces OspA/B in the tick, but represses their expression during mammalian infection. This paper reports a regulatory structure, consisting of two sequences flanking the ospAB promoter, that is required for enhancing ospA expression in B. burgdorferi grown in vitro, but repressing its expression during murine infection. Deletion or replacement of either the upstream or downstream sequence of the ospAB promoter caused a significant decrease in ospA expression in vitro, but a dramatic increase during murine infection. Fusion of either sequence with the flaB reporter promoter led to increased expression of an ospA reporter gene in vitro, but a decrease in the murine host. Furthermore, simultaneous fusion of both sequences with the reporter promoter showed a synergistic effect in enhancing expression of the ospA reporter in vitro, but repressing its expression during murine infection. Taken together, the results demonstrate that the regulatory structure functions oppositely in the two different environments and potentially provides B. burgdorferi with a molecular mechanism to quickly adapt to the distinct environments during its enzootic life cycle.

SUBMITTER: Xu Q

PROVIDER: S-EPMC3068683 | biostudies-other | 2010 Jul

REPOSITORIES: biostudies-other

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Two regulatory elements required for enhancing ospA expression in Borrelia burgdorferi grown in vitro but repressing its expression during mammalian infection.

Xu Qilong Q McShan Kristy K Liang Fang Ting FT

Microbiology (Reading, England) 20100415 Pt 7

During cycling between the tick vector and a mammal, the Lyme disease spirochaete Borrelia burgdorferi must coordinate expression of outer-surface proteins (Osps) A and B to quickly respond to environmental changes. The pathogen abundantly produces OspA/B in the tick, but represses their expression during mammalian infection. This paper reports a regulatory structure, consisting of two sequences flanking the ospAB promoter, that is required for enhancing ospA expression in B. burgdorferi grown i ...[more]

PMID: 20395273

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Project description:Previously, it has been shown that polyclonal antibodies to Borrelia burgdorferi and some monoclonal antibodies (MAbs) to borrelia major surface proteins caused inhibition of adherence of the bacteria to cultured human umbilical vein endothelial (HUVE) cells. In this study, fragment antigen binding (Fab) molecules generated from the immunoglobulin G fraction of rabbit anti-recombinant OspA serum were found to inhibit the adherence of B. burgdorferi to HUVE cells by 73%. Subsequently, MAbs were generated for use in determining whether or how B. burgdorferi outer surface proteins (Osps) A and/or B are involved in mediating attachment to, and/or invasion of, HUVE cells by B. burgdorferi. Twenty-two MAbs were generated to borrelial proteins with apparent molecular masses (determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis) of 19, 31 (OspA), 34 (OspB), and 35 kDa. Fab molecules from one anti-OspA MAb, 9B3D, demonstrated an inhibitory effect on bacterial association with HUVE cells. None of the other MAbs, including the other anti-OspA MAbs, showed an inhibitory effect on cell association of greater than 5%. This effect of Fab 9B3D was concentration dependent and plateaued at approximately 6 micrograms of Fab per ml (nearly 80% inhibition of the bacterial association with the monolayer). Penetration assays and cell association experiments performed by using immunofluorescence also suggested that the inhibitory action of 9B3D occurs at the level of adherence. MAb 9B3D recognized the OspA of every North American strain tested (n = 19) but only 3 [corrected] of 20 strains from western Europe, Russia, and Japan, suggesting that the North American strains and strains from other parts of the world may use different molecules and/or different OspA epitopes to interact with endothelial cells. Immunoblots of Escherichia coli expressing different OspA fusion peptides suggested that the 9B3D epitope resides in the carboxy-terminal half of OspA. MAb 9B3D promises to be a valuable tool for elucidating the domain or domains of OspA involved in the endothelial cell cytadherence of North American strains of B. burgdorferi.

Dataset Information

Two regulatory elements required for enhancing ospA expression in Borrelia burgdorferi grown in vitro but repressing its expression during mammalian infection.

Publications

Two regulatory elements required for enhancing ospA expression in Borrelia burgdorferi grown in vitro but repressing its expression during mammalian infection.

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