PubMed · 13021771
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J WIRTH. 1952. [Ornithosis].. https://pubmed.ncbi.nlm.nih.gov/13021771/
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Stable tetracycline resistance in Chlamydia suis is mediated by a family of genomic islands [the tet(C) islands] that are integrated into the chlamydial chromosome. The tet(C) islands contain several plasmid-specific genes, the tet(C) resistance gene and, in most cases, a novel insertion element (IScs605) encoding two predicted transposases. The hypothesis that IScs605 mediated the integration of the tet(C) resistance islands into the C. suis genome was tested using a plasmid-based transposition system in Escherichia coli. Both high- and medium-copy-number plasmids were used as carriers of IScs605 in these experiments. IScs605 integrated into a target plasmid (pOX38) when delivered by either donor plasmid, and integration of the entire donor plasmid was common. IScs605-mediated integration occurred at many positions within pOX38, with 36 of 38 events adjacent to a 5'-TTCAA-3' sequence. Deletions in each of the candidate transposase genes within IScs605 demonstrated that only one of the two ORFs was necessary for the observed transposition activity and target specificity. Analysis of progeny from the mating assays also indicated that IScs605 can excise following integration into a target DNA, and, in each tested case, the sequence 5'-AATTCAA-3' remained at the site of excision. Collectively, these results are consistent with the nucleotide sequence data collected for the tet(C) islands, and strongly suggest that a transposase within IScs605 is responsible for integration of these genomic islands into the C. suis chromosome.
Gamma interferon (IFN-gamma)-induced indoleamine dioxygenase (IDO), which inhibits chlamydial replication by reducing the availability of tryptophan, is up-regulated by interleukin-1beta (IL-1beta) and tumor necrosis factor alpha (TNF-alpha). The mechanisms by which this occurs include an increase in the synthesis of interferon regulatory factor-1 as well as a nuclear factor-kappaB (NF-kappaB)-dependent increase in the expression of IFN-gamma receptors (IFN-gammaR). Although Chlamydia is susceptible to IDO, it up-regulates IFN-gammaR expression to a greater degree than either IL-1beta or TNF-alpha, perhaps through interaction with Toll-like receptors (TLR). The purpose of this study was to determine the mechanism by which Chlamydia psittaci up-regulates IFN-gammaR expression and evaluate this effect on IDO induction. Infection of HEK 293 cells with C. psittaci increased IFN-gammaR expression only in cells expressing either TLR2 or TLR4 and the adaptor protein MD-2. In addition, up-regulation of IFN-gammaR expression in Chlamydia-infected HeLa cells could be blocked either by neutralizing TLRs with anti-TLR2 and/or anti-TLR4 or by inhibiting NF-kappaB transactivation with a proteasome inhibitor. Although the newly expressed IFN-gammaR in Chlamydia-infected cells were capable of binding IFN-gamma, they did not enhance IFN-gamma-induced IDO activity in a manner similar to those observed for IL-1beta and TNF-alpha. Instead, IDO activation in Chlamydia-infected cells was no different than that induced in uninfected cells, despite the increase in IFN-gammaR expression. Furthermore, the amount of IFN-gamma-induced signal transducer and activator of transcription 1 (STAT-1) activation in infected cells paralleled that observed in uninfected cells, suggesting that STAT-1 activation by these newly expressed receptors was impaired.
On the basis of high-resolution crystal structures of the antigen binding fragment of the chlamydia-specific monoclonal antibody S25-2 in complex with the trisaccharide alpha-Kdop-(2-->8)-alpha-Kdop-(2-->4)-alpha-Kdop and part structures thereof, seven modified alpha-Kdop-(2-->8)-alpha-Kdop disaccharide derivatives were synthesized starting from the protected disaccharide allyl ketoside 1. Hydroboration and subsequent oxidation as well as ozonolysis, respectively, followed by Wittig-reaction for chain elongation were used to install a terminal carboxylic group on spacer entities of various chain lengths. Furthermore, addition of methyl 2-thioacetate to the allyl group furnished the corresponding thioether derivative. Standard deprotection gave the target disaccharides as simplified trisaccharide analogues, which will be used to probe the contribution of the proximal carboxylic group in the binding of chlamydia-specific di- and trisaccharide-reactive monoclonal antibodies.