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In Treponema pallidum, homopolymeric guanosine repeats of varying length are present upstream of both Subfamily I ( tprC, D, F and I) and II ( tprE, G and J) tpr genes, a group of potential virulence factors, immediately upstream of the +1 nucleotide. To investigate the influence of these poly-G sequences on promoter activity, tprE, G, J, F and I promoter regions containing homopolymeric tracts with different numbers of Gs, the ribosomal binding site and start codon were cloned in frame with the green fluorescent protein reporter gene (GFP), and promoter activity was measured both as fluorescence emission from Escherichia coli cultures transformed with the different plasmid constructs and using quantitative RT-PCR. For tprJ, G and E-derived clones, fluorescence was significantly higher with constructs containing eight Gs or fewer, while plasmids containing the same promoters with none or more Gs gave modest or no signal above the background. In contrast, tprF/I-derived clones induced similar levels of fluorescence regardless of the number of Gs within the promoter. GFP mRNA quantification showed that all of the promoters induced measurable transcription of the GFP gene; however, only for Subfamily II promoters was message synthesis inversely correlated to the number of Gs in the construct. [ABSTRACT FROM AUTHOR]

Stimulation of isolated rat Kupffer cells by viable Leptospira interrogans, Treponema pallidum and Borrelia garinii elicited cellular responses resulting in the release of different tumor necrosis factor α (TNF-α) levels, depending on the spirochetes. L. interrogans induced TNF-α levels higher than those achieved with B. garinii and T. pallidum (in this order), but lower than the levels achieved with lipopolysaccharide (LPS). In contrast to L. interrogans, pretreatment of borreliae and treponemes with polymyxin B did not substantially diminish the ability of B. garinii and T. pallidum to stimulate Kupffer cells. Purified T. pallidum lipoproteins TpN47, TmpA, TpN15–TpN17, and B. garinii OspA induced TNF-α responses comparable to that achieved by LPS. This response was almost insensitive to the action of polymyxin B. [Copyright &y& Elsevier]