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dc.contributor.authorGuillotte, Mark L
dc.contributor.authorChandler, Courtney E
dc.contributor.authorVerhoeve, Victoria I
dc.contributor.authorGillespie, Joseph J
dc.contributor.authorDriscoll, Timothy P
dc.contributor.authorRahman, M Sayeedur
dc.contributor.authorErnst, Robert K
dc.contributor.authorAzad, Abdu F
dc.date.accessioned2021-05-11T20:00:40Z
dc.date.available2021-05-11T20:00:40Z
dc.date.issued2021-05-05
dc.identifier.urihttp://hdl.handle.net/10713/15618
dc.description.abstractSpecies of Rickettsia (Alphaproteobacteria: Rickettsiales) are obligate intracellular parasites of a wide range of eukaryotes, with recognized arthropod-borne human pathogens belonging to the transitional group (TRG), typhus group (TG), and spotted fever group (SFG) rickettsiae. Growing in the host cytosol, rickettsiae pilfer numerous metabolites to make a typical Gram-negative bacterial cell envelope. The O-antigen of rickettsial lipopolysaccharide (LPS) is immunogenic and has been shown to tether the S-layer to the rickettsial surface; however, little is known about the structure and immunogenicity of the Rickettsia lipid A moiety. The structure of lipid A, the membrane anchor of LPS, affects the ability of this molecule to interact with components of the host innate immune system, specifically the MD-2/TLR4 receptor complex. To dissect the host responses that can occur during Rickettsia in vitro and in vivo infection, structural analysis of Rickettsia lipid A is needed. Lipid A was extracted from four Rickettsia species and structurally analyzed. R. akari (TRG), R. typhi (TG), and R. montanensis (SFG) produced a similar structure, whereas R. rickettsii (SFG) altered the length of a secondary acyl group. While all structures have longer acyl chains than known highly inflammatory hexa-acylated lipid A structures, the R. rickettsii modification should differentially alter interactions with the hydrophobic internal pocket in MD2. The significance of these characteristics toward inflammatory potential as well as membrane dynamics between arthropod and vertebrate cellular environments warrants further investigation. Our work adds lipid A to the secretome and O-antigen as variable factors possibly correlating with phenotypically diverse rickettsioses.IMPORTANCE Spikes in rickettsioses occur as deforestation, urbanization, and homelessness increase human exposure to blood-feeding arthropods. Still, effective Rickettsia vaccines remain elusive. Recent studies have determined that Rickettsia lipopolysaccharide anchors the protective S-layer to the bacterial surface and elicits bactericidal antibodies. Furthermore, growing immunological evidence suggests vertebrate sensors (MD-2/TLR4 and noncanonical inflammasome) typically triggered by the lipid A portion of lipopolysaccharide are activated during Rickettsia infection. However, the immunopotency of Rickettsia lipid A is unknown due to poor appreciation for its structure. We determined lipid A structures for four distinct rickettsiae, revealing longer acyl chains relative to highly inflammatory bacterial lipid A. Surprisingly, lipid A of the Rocky Mountain spotted fever agent deviates in structure from other rickettsiae. Thus, lipid A divergence may contribute to variable disease phenotypes, sounding an alarm for determining its immunopotency and possible utility (i.e., as an adjuvant or anti-inflammatory) for development of more prudent rickettsiacidal therapies.en_US
dc.description.urihttps://doi.org/10.1128/mSphere.00184-21en_US
dc.description.urihttps://msphere.asm.org/content/6/3/e00184-21en_US
dc.language.isoenen_US
dc.publisherAmerican Society for Microbiologyen_US
dc.relation.ispartofmSphereen_US
dc.rightsCopyright © 2021 Guillotte et al.en_US
dc.subjectRickettsiaen_US
dc.subjectlipid Aen_US
dc.subjectlipopolysaccharideen_US
dc.subjectpathogenesisen_US
dc.subjectrickettsiosesen_US
dc.subjectspotted fever groupen_US
dc.subjecttransitional groupen_US
dc.subjecttyphus groupen_US
dc.titleLipid A Structural Divergence in Rickettsia Pathogens.en_US
dc.typeArticleen_US
dc.identifier.doi10.1128/mSphere.00184-21
dc.identifier.pmid33952661
dc.source.volume6
dc.source.issue3
dc.source.countryUnited States
dc.source.countryUnited States
dc.source.countryUnited States
dc.source.countryUnited States


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