Browsing by Subject "OspC"

Now showing 1 - 6 of 6
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    Corrigendum: Role of HK2 in the Enzootic Cycle of Borrelia burgdorferi
    (Frontiers Media, 2021-03-31) Liu, Qiang; Xu, Haijun; Zhang, Yan; Yang, Jing; Du, Jimei; Zhou, Yan; Yang, X. Frank; Lou, Yongliang; Microbiology and Immunology, School of Medicine
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    Elucidating the interaction of Borrelia burgdorferi OspC with phagocytes in the establishment of lyme borreliosis
    (2015-03-20) Carrasco, Sebastian Eduardo; Yang, X. Frank; Serezani, C. Henrique; Blum, Janice Sherry, 1957-; Johnson, Raymond M.; Bauer, Margaret E.
    Lyme disease, the most prevalent vector-borne illness in the United States, is a multisystem inflammatory disorder caused by infection with the spirochete Borrelia burgdorferi (Bb). This spirochete is maintained in nature through an enzootic cycle involving ticks and small mammals. The Bb genome encodes a large number of surface lipoproteins, many of which are expressed during mammalian infection. One of these lipoproteins is the major outer surface protein C (OspC) whose production is induced during transmission as spirochetes transition from ticks to mammals. OspC is required for Bb to establish infection in mice and has been proposed to facilitate evasion of innate immunity. However, the exact biological function of OspC remains elusive. Our studies show the ospC-deficient spirochete could not establish infection in NOD-scid IL2rγnull mice that lack B cells, T cells, NK cells, and lytic complement, whereas the wild-type spirochete was fully infectious in these mice. The ospC mutant also could not establish infection in SCID and C3H mice that were transiently neutropenic during the first 48 h post-challenge. However, depletion of F4/80+ phagocytes at the skin-site of inoculation in SCID mice allowed the ospC mutant to establish infection in vivo. In phagocyte-depleted SCID mice, the ospC mutant was capable to colonize the joints and triggered neutrophilia during dissemination in a similar pattern as wild-type bacteria. We then constructed GFP-expressing Bb strains to evaluate the interaction of the ospC mutant with phagocytes. Using flow cytometry and fluorometric assay for phagocytosis, we found that phagocytosis of GFP-expressing ospC mutant spirochetes by murine peritoneal macrophages and human THP-1 cells was significantly higher than parental wild-type Bb strains, suggesting that OspC has an anti-phagocytic property. This enhancement in phagocytosis was not mediated by MARCO and CD36 scavenger receptors and was not associated with changes in mRNA levels of TNFα, IL-1β, and IL-10. Phagocytosis assays with HL60 neutrophil-like cells showed that uptake of Bb strains was independent to OspC. Together, our findings reveal that F4/80+ phagocytes are important for clearance of the ospC mutant, and suggest that OspC promotes spirochetes' evasion of macrophages in the skin of mice during early Lyme borreliosis.
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    Identifying Factors Controlling Cell Shape and Virulence Gene Expression in Borrelia Burgdorferi
    (2019-08) Grothe, Amberly Nicole; Yang, X. Frank; Gilk, Stacey; Nelson, David
    Lyme disease is a multi-system inflammatory disorder that is currently the fastest growing arthropod-borne disease in the United States. The Lyme disease pathogen, Borrelia burgdorferi, exists within an enzootic cycle consisting of Ixodes tick vectors and a variety of vertebrate hosts. Borrelia lies within a distinct clade of microorganisms known as spirochetes which exhibit a unique spiral morphology. The underlying genetic mechanisms controlling for borrelial morphologies are still being discovered. One flagellar protein, FlaB, has been indicated to affect both spiral shape and motility of the organisms and significantly impacts the organism’s ability to establish infection. Due to the potential connection between morphological characteristics and pathogenesis, we sought to screen and identify morphological mutants in an attempt to identify genes associated with morphological phenotypes of Borrelia burgdorferi. Among Borrelia’s unique features is the presence of abundant lipoproteins making up its cellular membrane as opposed to the typical lipopolysaccharides. These proteins confer a wide variety of functions to the microorganism, among which include the abilities to circulate between widely differing hosts and to establish infection. Two important outer surface proteins, OspC and OspA, are found to be inversely expressed throughout the borrelial life cycle. OspC, in particular, becomes highly expressed during tick-feeding and transmission to the mammalian host. It has been found to be essential for establishment of infection. A global regulatory pathway has been shown to control for OspC, however there are missing links in this pathway between the external stimuli (such as temperature, pH, and cell density) and the regulatory pathway. We have performed a screening process to identify OspC expression mutants in order to identify novel genes associated with this pathway.
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    Investigation of ospC Expression Variation among Borrelia burgdorferi Strains
    (Frontiers, 2017-04-20) Xiang, Xuwu; Yang, Youyun; Du, Jimei; Lin, Tianyu; Chen, Tong; Yang, X. Frank; Lou, Yongliang; Microbiology and Immunology, School of Medicine
    Outer surface protein C (OspC) is the most studied major virulence factor of Borrelia burgdorferi, the causative agent of Lyme disease. The level of OspC varies dramatically among B. burgdorferi strains when cultured in vitro, but little is known about what causes such variation. It has been proposed that the difference in endogenous plasmid contents among strains contribute to variation in OspC phenotype, as B. burgdorferi contains more than 21 endogenous linear (lp) and circular plasmids (cp), and some of which are prone to be lost. In this study, we analyzed several clones isolated from B. burgdorferi strain 297, one of the most commonly used strains for studying ospC expression. By taking advantage of recently published plasmid sequence of strain 297, we developed a multiplex PCR method specifically for rapid plasmid profiling of B. burgdorferi strain 297. We found that some commonly used 297 clones that were thought having a complete plasmid profile, actually lacked some endogenous plasmids. Importantly, the result showed that the difference in plasmid profiles did not contribute to the ospC expression variation among the clones. Furthermore, we found that B. burgdorferi clones expressed different levels of BosR, which in turn led to different levels of RpoS and subsequently, resulted in OspC level variation among B. burgdorferi strains.
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    The oligopeptide ABC transporter OppA4 negatively regulates the virulence factor OspC production of the Lyme disease pathogen
    (Elsevier, 2018) Zhou, Bibi; Yang, Youyun; Chen, Tong; Lou, Yongliang; Yang, X. Frank; Microbiology and Immunology, School of Medicine
    Borrelia burgdorferi sensu lato, the agent of Lyme disease, exists in nature through a complex enzootic life cycle that involves both ticks and mammals. The B. burgdorferi genome encodes five Oligopeptide ABC transporters (Opp) that are predicted to be involve in transport of various nutrients. Previously, it was reported that OppA5 is important for the optimal production of OspC, a major virulence factor of B. burgdorferi. In this study, possible role of another Oligopeptide ABC transporter, OppA4 in ospC expression was investigated by construction of an oppA4 deletion mutant and the complemented strain. Inactivation of oppA4 resulted an increased production of OspC, suggesting that OppA4 has a negative impact on ospC expression. Expression of ospC is controlled by Rrp2-RpoN-RpoS, the central pathway essential for mammal infection. We showed that increased ospC expression in the oppA4 mutant was due to an increased rpoS expression. We then further investigated how OppA4 negatively regulates this pathway. Two regulators, BosR and BadR, are known to positively and negatively, respectively, regulate the Rrp2-RpoN-RpoS pathway. We found that deletion of oppA4 resulted in an increased level of BosR. Previous reports showed that bosR is mainly regulated at the post-transcriptional level by other factors. However, OppA4 appears to negatively regulate bosR expression at the transcriptional level. The finding of OppA4 involved in regulation of the Rrp2-RpoN-RpoS pathway further reinforces the importance of nutritional virulence to the enzootic cycle of B. burgdorferi.
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    The Rrp2-RpoN-RpoS pathway plays an important role in the blood-brain barrier transmigration of the Lyme disease pathogen
    (American Society for Microbiology, 2023) Alanazi, Fuad; Raghunandanan, Sajith; Priya, Raj; Yang, X. Frank; Microbiology and Immunology, School of Medicine
    Lyme disease, caused by Borrelia (or Borreliella) burgdorferi, is a complex multisystemic disorder that includes Lyme neuroborreliosis resulting from the invasion of both the central and peripheral nervous systems. However, factors that enable the pathogen to cross the blood-brain barrier (BBB) and invade the central nervous system (CNS) are still not well understood. The objective of this study was to identify the B. burgdorferi factors required for BBB transmigration. We utilized a transwell BBB model based on human brain-microvascular endothelial cells and focused on investigating the Rrp2-RpoN-RpoS pathway, a central regulatory pathway that is essential for mammalian infection by B. burgdorferi. Our results demonstrated that the Rrp2-RpoN-RpoS pathway is crucial for BBB transmigration. Furthermore, we identified OspC, a major surface lipoprotein controlled by the Rrp2-RpoN-RpoS pathway, as a significant contributor to BBB transmigration. Constitutive production of OspC in a mutant defective in the Rrp2-RpoN-RpoS pathway did not rescue the impairment in BBB transmigration, indicating that this pathway controls additional factors for this process. Two other major surface lipoproteins controlled by this pathway, DbpA/B and BBK32, appeared to be dispensable for BBB transmigration. In addition, both the surface lipoprotein OspA and the Rrp1 pathway, which are required B. burgdorferi colonization in the tick vector, were found not required for BBB transmigration. Collectively, our findings using in vitro transwell assays uncover another potential role of the Rrp2-RpoN-RpoS pathway in BBB transmigration of B. burgdorferi and invasion into the CNS.