Last data update: May 13, 2024. (Total: 46773 publications since 2009)
Records 1-3 (of 3 Records) |
Query Trace: Cox DL[original query] |
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Evaluation of a digital flocculation reader for the rapid plasma reagin test for the serological diagnosis of syphilis
Castro AR , Binks DD , Raymer DL , Kikkert SE , Jost HA , Park MM , Card BD , Cox DL . Sex Transm Dis 2012 39 (3) 223-5 We described the ASiManager-AT digital flocculation reader to demonstrate concordance between visual and digital readings of the rapid plasma reagin test for detection of antibodies in the serum of patients with syphilis. A qualitative and quantitative rapid plasma reagin was performed on each serum samples giving a concordance of 98.6% and 99.7%, respectively, for reactives and 100% for nonreactives. |
Surface immunolabeling and consensus computational framework to identify candidate rare outer membrane proteins of Treponema pallidum
Cox DL , Luthra A , Dunham-Ems S , Desrosiers DC , Salazar JC , Caimano MJ , Radolf JD . Infect Immun 2010 78 (12) 5178-94 Treponema pallidum reacts poorly with the antibodies present in rabbit and human syphilitic sera, a property attributed to the paucity of proteins in its outer membrane. To better understand the basis for the syphilis spirochete's "stealth pathogenicity", we used a dual-label, 3-step amplified assay in which treponemes encapsulated in gel microdroplets were probed with syphilitic sera in parallel with anti-FlaA antibodies. A small (approx. 5-10%) but reproducible fraction of intact treponemes bound IgG and/or IgM antibodies. Three lines of evidence supported that the surface antigens were likely beta-barrel-forming outer membrane proteins (OMPs): (i) surface-labeling with anti-lipoidal (VDRL) antibodies was not observed, (ii) immunoblot analysis confirmed prior results that T. pallidum glycolipids are not immunoreactive, and (iii) labeling of intact organisms was not appreciably affected by proteinase K (PK) treatment. With this method, we also demonstrate that TprK (TP0897), an extensively studied candidate OMP, and TP0136, a lipoprotein recently reported to be surface-exposed, are both periplasmic. Consistent with the immunolabeling studies, TprK also was found to lack amphiphilicity, a characteristic property of beta-barrel-forming proteins. Using a consensus computational framework that combined subcellular localization and beta-barrel structural prediction tools, we generated ranked groups of candidate rare OMPs, the predicted T. pallidum outer membrane proteome (OMPeome), which we postulate includes the surface-exposed molecules detected by our enhanced gel microdroplet assay. In addition to underscoring the syphilis spirochete's remarkably poor surface antigenicity, our findings help to explain the complex and shifting balance between pathogen and host defenses that characterizes syphilitic infection. |
Cryo-electron tomography elucidates the molecular architecture of Treponema pallidum, the syphilis spirochete
Izard J , Renken C , Hsieh CE , Desrosiers DC , Dunham-Ems S , La Vake C , Gebhardt LL , Limberger RJ , Cox DL , Marko M , Radolf JD . J Bacteriol 2009 191 (24) 7566-80 Cryo-electron tomography (CET) was used to examine the native cellular organization of Treponema pallidum, the syphilis spirochete. T. pallidum cells appeared to form flat waves, did not contain an outer coat, and, except for bulges over the basal bodies and widening in the vicinity of flagellar filaments, displayed a uniform periplasmic space. Although the outer membrane (OM) generally was smooth in contour, OM extrusions and blebs frequently were observed, highlighting the structure's fluidity and lack of attachment to underlying periplasmic constituents. Cytoplasmic filaments converged from their attachment points opposite the basal bodies to form arrays that run roughly parallel to the flagellar filaments along the inner surface of the cytoplasmic membrane (CM). Motile treponemes stably attached to rabbit epithelial cells predominantly via their tips. CET revealed that T. pallidum cell ends have a complex morphology and assume at least four distinct morphotypes. Images of dividing treponemes and organisms shedding cell envelope-derived blebs provided evidence for the spirochete's complex membrane biology. In the regions without flagellar filaments, PG was visualized as a thin layer that divided the periplasmic space into zones of higher and lower electron density adjacent to the CM and OM, respectively. Flagellar filaments were observed overlying the PG layer, while image modeling placed the PG-basal body contact site in the vicinity of the stator-P-collar junction. Bioinformatics and homology modeling indicated that the MotB proteins of T. pallidum, T. denticola, and B. burgdorferi have membrane topologies and PG binding sites highly similar to those of their well characterized E. coli and H. pylori orthologs. Collectively, our results help to clarify fundamental differences in cell envelope ultrastructure between spirochetes and Gram-negatives. They also confirm that PG stabilizes the flagellar motor and enable us to propose that in most spirochetes motility results from rotation of the flagellar filaments against the PG. |
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