scholarly journals The Coxiella burnetii QpH1 Plasmid Is a Virulence Factor for Colonizing Bone Marrow-Derived Murine Macrophages

2021 ◽  
Vol 203 (9) ◽  
Author(s):  
Shengdong Luo ◽  
Shanshan Lu ◽  
Huahao Fan ◽  
Zeliang Chen ◽  
Zhihui Sun ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Coxiella Burnetii ◽  
Virulence Factor ◽  
Unknown Function ◽  
Shuttle Vector ◽  
Critical Role ◽  
Growth Defect ◽  
Content Type ◽  
Murine Macrophages

ABSTRACT Coxiella burnetii strains carry one of four large, conserved, autonomously replicating plasmids (QpH1, QpRS, QpDV, or QpDG) or a QpRS-like chromosomally integrated sequence of unknown function. Here, we report the characterization of the QpH1 plasmid of C. burnetii Nine Mile phase II by making QpH1-deficient strains. A shuttle vector pQGK containing the CBUA0036 to CBUA0039a region (predicted as being required for QpH1 maintenance) was constructed. The pQGK vector can be stably transformed into Nine Mile II and maintained at a similar low copy number like QpH1. Importantly, transformation with pQGK cured the endogenous QpH1 due to plasmid incompatibility. Compared to a Nine Mile II transformant of an RSF1010-ori-based vector, the pQGK transformant shows a similar growth curve in both axenic media and Buffalo green monkey kidney cells, a variable growth defect in macrophage-like THP-1 cells depending on the origin of inoculum, and dramatically reduced ability to colonize wild-type bone marrow-derived murine macrophages. Furthermore, we found that CBUA0037 to CBUA0039 open reading frames (ORFs) are essential for plasmid maintenance, and CBUA0037 and CBUA0038 ORFs account for plasmid compatibility. In addition, plasmid-deficient C. burnetii can be isolated by using CBUA0037 or CBUA0038 deletion vectors. Furthermore, QpH1-deficient C. burnetii strains caused a lesser extent of splenomegaly in SCID mice, but, intriguingly, they had significant growth in SCID mouse-sourced macrophages. Taken together, our data suggest that QpH1 encodes a factor(s) essential for colonizing murine, not human, macrophages. This study suggests a critical role of QpH1 for C. burnetii persistence in rodents and expands the toolkit for genetic studies in C. burnetii. IMPORTANCE All C. burnetii isolates carry one of four large, conserved, autonomously replicating plasmids or a plasmid-like chromosomally integrated sequence. The plasmid is a candidate virulence factor of unknown function. Here, we describe the construction of novel shuttle vectors that allow making plasmid-deficient C. burnetii mutants. With this plasmid-curing approach, we characterized the role of the QpH1 plasmid in in vitro and in vivo C. burnetii infection models. We found that the plasmid plays a critical role for C. burnetii growth in murine macrophages. Our work suggests an essential role of the QpH1 plasmid for the acquisition of colonizing capability in rodents by C. burnetii. This study represents a major step toward unravelling the mystery of the C. burnetii cryptic plasmids.

scholarly journals The Coxiella burnetii QpH1 plasmid is a virulence factor for colonizing bone marrow-derived murine macrophages

2020 ◽  
Author(s):  
Shengdong Luo ◽  
Zhihui Sun ◽  
Huahao Fan ◽  
Shanshan Lu ◽  
Yan Hu ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Coxiella Burnetii ◽  
Virulence Factor ◽  
Critical Role ◽  
Murine Macrophages ◽  
Infection Models

AbstractCoxiella burnetii carries a large conserved plasmid or plasmid-like chromosomally integrated sequence of unknown function. Here we report the curing of QpH1 plasmid from C. burnetii Nine Mile phase II, the characterization of QpH1-deficient C. burnetii in in vitro and in vivo infection models, and the characterization of plasmid biology. A shuttle vector pQGK, which is composed of the CBUA0036-0039a region (predicted for QpH1 maintenance), an E. coli plasmid ori, eGFP and kanamycin resistance genes was constructed. The pQGK vector can be stably transformed into Nine Mile II and maintained at a similar low copy like QpH1. Importantly, transformation with pQGK cured the endogenous QpH1 due to plasmid incompatibility. Compared to a Nine Mile II transformant of a RSF1010-based vector, the pQGK transformant shows an identical one-step growth curve in axenic media, a similar growth curve in Buffalo green monkey kidney cells, an evident growth defect in macrophage-like THP-1 cells, and dramatically reduced ability of colonizing bone marrow-derived murine macrophages. In the SCID mouse infection model, the pQGK transformants caused a lesser extent of splenomegaly. Moreover, the plasmid biology was investigated by mutagenesis. We found CBUA0037-0039 are essential for plasmid maintenance, and CBUA0037-0038 account for plasmid compatibility. Taken together, our data suggest that QpH1 encodes factor(s) essential for colonizing murine macrophages, and to a lesser extent for colonizing human macrophages. This study highlights a critical role of QpH1 for C. burnetii persistence in rodents, and expands the toolkit for genetic studies in C. burnetii.Author summaryIt is postulated that C. burnetii recently evolved from an inherited symbiont of ticks by the acquisition of novel virulence factors. All C. burnetii isolates carry a large plasmid or have a chromosomally integrated plasmid-like sequence. The plasmid is a candidate virulence factor that contributes to C. burnetii evolution. Here we describe the construction of novel shuttle vectors that allow to make plasmid-deficient C. burnetii mutants. With this plasmid-curing approach, we characterized the role of the QpH1 plasmid in in vitro and in vivo C. burnetii infection models. We found that the plasmid plays a critical role for C. burnetii growth in macrophages, especially in murine macrophages, but not in axenic media and BGMK cells. Our work highlights an essential role of the plasmid for the acquisition of colonizing capability in rodents by C. burnetii. This study represents a major step toward unravelling the mystery of the C. burnetii cryptic plasmids.

scholarly journals Physiologic Expression of the Candida albicans Pescadillo Homolog Is Required for Virulence in a Murine Model of Hematogenously Disseminated Candidiasis

2012 ◽  
Vol 11 (12) ◽  
pp. 1552-1556 ◽  
Author(s):  
Priya Uppuluri ◽  
Ashok K. Chaturvedi ◽  
Niketa Jani ◽  
Read Pukkila-Worley ◽  
Carlos Monteagudo ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Murine Model ◽  
Critical Role ◽  
Growth Defect ◽  
Mammalian Host ◽  
Developmental Cycle ◽  
Yeast Growth ◽  
Content Type ◽  
Disseminated Candidiasis

ABSTRACT Morphogenetic conversions contribute to the pathogenesis of Candida albicans invasive infections. Many studies to date have convincingly demonstrated a link between filamentation and virulence; however, relatively little is known regarding the role of the filament-to-yeast transition during the pathogenesis of invasive candidiasis. We previously identified the C. albicans pescadillo homolog ( PES1 ) as essential during yeast growth and growth of lateral yeast on hyphae but not during hyphal growth. Furthermore, we demonstrated that PES1 is required for virulence in vivo in a Galleria mellonella larva model of candidiasis. Here, we have used a regulatable tetO-PES1 / pes1 strain to assess the contribution of C. albicans PES1 to pathogenesis in the commonly used and clinically relevant murine model of hematogenously disseminated candidiasis. Our results indicate that a physiologically controlled level of PES1 expression is required for full virulence in this animal model, with virulence defects observed both when PES1 is overexpressed and and when it is depleted. The pathogenetic defect of cells depleted of PES1 is not due to a general growth defect, as demonstrated by the fact that PES1 -depleted cells still kill Caenorhabditis elegans as efficiently as the wild type due to hyphal outgrowth through worm tissues. Our results suggest a critical role of lateral yeast growth in the ability of C. albicans to normally proliferate within tissues, as well as a pivotal role for Pes1 in the normal developmental cycle of C. albicans within the mammalian host during infection.

scholarly journals Role of B Cells in Host Defense against Primary Coxiella burnetii Infection

2015 ◽  
Vol 83 (12) ◽  
pp. 4826-4836 ◽  
Author(s):  
Laura Schoenlaub ◽  
Alexandra Elliott ◽  
Danielle Freches ◽  
William J. Mitchell ◽  
Guoquan Zhang
Keyword(s):  
B Cells ◽  
Host Defense ◽  
Coxiella Burnetii ◽  
Critical Role ◽  
Interleukin 10 ◽  
Content Type ◽  
B1a Cells

DespiteCoxiella burnetiibeing an obligate intracellular bacterial pathogen, our recent study demonstrated that B cells play a critical role in vaccine-induced immunity toC. burnetiiinfection by producing protective antibodies. However, the role of B cells in host defense against primaryC. burnetiiinfection remains unclear. In this study, we investigated whether B cells play an important role in host defense against primaryC. burnetiiinfection. The results showed that peritoneal B cells were able to phagocytose virulentC. burnetiibacteria and formCoxiella-containing vacuoles (CCVs) and thatC. burnetiican infect and replicate in peritoneal B1a subset B cellsin vitro, demonstrating a potential role for peritoneal B cells in host defense againstC. burnetiiinfectionin vivo. In addition, the results showing that B1a cells secreted a high level of interleukin-10 (IL-10) in response toC. burnetiiinfectionin vitrosuggest that B1a cells may play an important role in inhibiting theC. burnetiiinfection-induced inflammatory response. The observation that adoptive transfer of peritoneal B cells did not significantly affect the severity ofC. burnetiiinfection-induced diseases in both severe combined immunity-deficient (SCID) and μMT mice indicates that peritoneal B cells alone may not be able to controlC. burnetiiinfection. In contrast, our finding thatC. burnetiiinfection induced more-severe splenomegaly and a higher bacterial burden in the spleens of B1a cell-deficient Bruton's tyrosine kinase x-linked immunity-deficient (BTKxid) mice than in their wild-type counterparts further suggests that B1a cells play an important role in host defense against primaryC. burnetiiinfection.

scholarly journals Host and Bacterial Factors Control Susceptibility of Drosophila melanogaster to Coxiella burnetii Infection

2017 ◽  
Vol 85 (7) ◽  
Author(s):  
Reginaldo G. Bastos ◽  
Zachary P. Howard ◽  
Aoi Hiroyasu ◽  
Alan G. Goodman
Keyword(s):  
Drosophila Melanogaster ◽  
Coxiella Burnetii ◽  
Q Fever ◽  
Animal Health ◽  
Critical Role ◽  
Content Type ◽  
Imd Pathway ◽  
Tnf Superfamily ◽  
Necrosis Factor

ABSTRACT Coxiella burnetii is the causative agent of Q fever, a zoonotic disease that threatens both human and animal health. Due to the paucity of experimental animal models, little is known about how host factors interface with bacterial components and affect pathogenesis. Here, we used Drosophila melanogaster, in conjunction with the biosafety level 2 (BSL2) Nine Mile phase II (NMII) clone 4 strain of C. burnetii, as a model to investigate host and bacterial components implicated in infection. We demonstrate that adult Drosophila flies are susceptible to C. burnetii NMII infection and that this bacterial strain, which activates the immune deficiency (IMD) pathway, is able to replicate and cause mortality in the animals. We show that in the absence of Eiger, the only known tumor necrosis factor (TNF) superfamily homolog in Drosophila, Coxiella-infected flies exhibit reduced mortality from infection. We also demonstrate that the Coxiella type 4 secretion system (T4SS) is critical for the formation of the Coxiella-containing vacuole and establishment of infection in Drosophila. Altogether, our data reveal that the Drosophila TNF homolog Eiger and the Coxiella T4SS are implicated in the pathogenesis of C. burnetii in flies. The Drosophila/NMII model mimics relevant aspects of the infection in mammals, such as a critical role of host TNF and the bacterial T4SS in pathogenesis. Our work also demonstrates the usefulness of this BSL2 model to investigate both host and Coxiella components implicated in infection.

scholarly journals The Role of the Bone Marrow Microenvironment in the Response to Infection

2020 ◽  
Vol 11 ◽  
Author(s):  
Courtney B. Johnson ◽  
Jizhou Zhang ◽  
Daniel Lucas
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Immune Cells ◽  
Critical Role ◽  
Primary Source ◽  
Bone Marrow Microenvironment ◽  
Future Research ◽  
Multipotent Stem Cells ◽  
Hematopoietic Stem

Hematopoiesis in the bone marrow (BM) is the primary source of immune cells. Hematopoiesis is regulated by a diverse cellular microenvironment that supports stepwise differentiation of multipotent stem cells and progenitors into mature blood cells. Blood cell production is not static and the bone marrow has evolved to sense and respond to infection by rapidly generating immune cells that are quickly released into the circulation to replenish those that are consumed in the periphery. Unfortunately, infection also has deleterious effects injuring hematopoietic stem cells (HSC), inefficient hematopoiesis, and remodeling and destruction of the microenvironment. Despite its central role in immunity, the role of the microenvironment in the response to infection has not been systematically investigated. Here we summarize the key experimental evidence demonstrating a critical role of the bone marrow microenvironment in orchestrating the bone marrow response to infection and discuss areas of future research.

scholarly journals The critical role of T cells in glucocorticoid-induced osteoporosis

2020 ◽  
Vol 12 (1) ◽  
Author(s):  
Lin Song ◽  
Lijuan Cao ◽  
Rui Liu ◽  
Hui Ma ◽  
Yanan Li ◽  
...  
Keyword(s):  
Bone Marrow ◽  
T Cells ◽  
Steady State ◽  
Side Effects ◽  
Critical Role ◽  
Wild Type ◽  
Receptor Activator ◽  
Steady State Levels ◽  
Induced Apoptosis

AbstractGlucocorticoids (GC) are widely used clinically, despite the presence of significant side effects, including glucocorticoid-induced osteoporosis (GIOP). While GC are believed to act directly on osteoblasts and osteoclasts to promote osteoporosis, the detailed underlying molecular mechanism of GC-induced osteoporosis is still not fully elucidated. Here, we show that lymphocytes play a pivotal role in regulating GC-induced osteoporosis. We show that GIOP could not be induced in SCID mice that lack T cells, but it could be re-established by adoptive transfer of splenic T cells from wild-type mice. As expected, T cells in the periphery are greatly reduced by GC; instead, they accumulate in the bone marrow where they are protected from GC-induced apoptosis. These bone marrow T cells in GC-treated mice express high steady-state levels of NF-κB receptor activator ligand (RANKL), which promotes the formation and maturation of osteoclasts and induces osteoporosis. Taken together, these findings reveal a critical role for T cells in GIOP.

Understanding destination evangelism: a social media viewpoint

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Purvendu Sharma
Keyword(s):  
Social Media ◽  
Information Seeking ◽  
Structural Equation ◽  
Structural Equation Models ◽  
Critical Role ◽  
Content Type ◽  
Mediating Role ◽  
Information Seeking Behaviors ◽  
Role Of Information

PurposeThe present research aims to introduce and understand the promising nature of destination evangelism in the context of social media-based tourism communities (SMTCs). Further, factors that influence evangelism and information-seeking behaviors on SMTCs are examined.Design/methodology/approachA conceptual model is developed that features an interplay of destination distinctiveness, destination evangelism, travel commitment and information-seeking engagement. Data were collected from 215 active users of SMTCs and analyzed using structural equation models.FindingsThe research findings indicate that destination distinctiveness and information-seeking positively lead to destination evangelism. Information-seeking is found to mediate the relationship between (1) destination evangelism and travel commitment and (2) destination evangelism and distinctiveness.Research limitations/implicationsThe research offers meaningful insights into exploring constituents of destination evangelism. The research also understands and highlights the critical role of information-seeking engagement about distinct destinations.Practical implicationsThis research highlights key areas to build, improve and inspire destination evangelism on SMTCs.Originality/valueThis study offers a fresh contribution to tourism literature by investigating destination evangelism and its drivers. This is explained by closely uniting vital research streams of evangelism, tourism and engagement. It further highlights the dual mediating role of information seeking, suggesting that these engagements are critical to evangelizing destinations.

scholarly journals Phagocytes from Mice Lacking the Sts Phosphatases Have an Enhanced Antifungal Response to Candida albicans

mBio ◽  
2018 ◽  
Vol 9 (4) ◽  
Author(s):  
David Frank ◽  
Shamoon Naseem ◽  
Gian Luigi Russo ◽  
Cindy Li ◽  
Kaustubh Parashar ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Immune Response ◽  
Candida Albicans ◽  
Tyrosine Kinase ◽  
Critical Role ◽  
Inflammasome Activation ◽  
Wild Type ◽  
Content Type ◽  
Enhanced Production ◽  
Immunological Mechanisms

ABSTRACT Mice lacking expression of the homologous phosphatases Sts-1 and Sts-2 (Sts−/− mice) are resistant to disseminated candidiasis caused by the fungal pathogen Candida albicans. To better understand the immunological mechanisms underlying the enhanced resistance of Sts−/− mice, we examined the kinetics of fungal clearance at early time points. In contrast to the rapid C. albicans growth seen in normal kidneys during the first 24 h postinfection, we observed a reduction in kidney fungal CFU within Sts−/− mice beginning at 12 to 18 h postinfection. This corresponds to the time period when large numbers of innate leukocytes enter the renal environment to counter the infection. Because phagocytes of the innate immune system are important for host protection against pathogenic fungi, we evaluated responses of bone marrow leukocytes. Relative to wild-type cells, Sts−/− marrow monocytes and bone marrow-derived dendritic cells (BMDCs) displayed a heightened ability to inhibit C. albicans growth ex vivo. This correlated with significantly enhanced production of reactive oxygen species (ROS) by Sts−/− BMDCs downstream of Dectin-1, a C-type lectin receptor that plays a critical role in stimulating host responses to fungi. We observed no visible differences in the responses of other antifungal effector pathways, including cytokine production and inflammasome activation, despite enhanced activation of the Syk tyrosine kinase downstream of Dectin-1 in Sts−/− cells. Our results highlight a novel mechanism regulating the immune response to fungal infections. Further understanding of this regulatory pathway could aid the development of therapeutic approaches to enhance protection against invasive candidiasis. IMPORTANCE Systemic candidiasis caused by fungal Candida species is becoming an increasingly serious medical problem for which current treatment is inadequate. Recently, the Sts phosphatases were established as key regulators of the host antifungal immune response. In particular, genetic inactivation of Sts significantly enhanced survival of mice infected intravenously with Candida albicans. The Sts−/− in vivo resistance phenotype is associated with reduced fungal burden and an absence of inflammatory lesions. To understand the underlying mechanisms, we studied phagocyte responses. Here, we demonstrate that Sts−/− phagocytes have heightened responsiveness to C. albicans challenge relative to wild-type cells. Our data indicate the Sts proteins negatively regulate phagocyte activation via regulating selective elements of the Dectin-1–Syk tyrosine kinase signaling axis. These results suggest that phagocytes lacking Sts respond to fungal challenge more effectively and that this enhanced responsiveness partially underlies the profound resistance of Sts−/− mice to systemic fungal challenge.

Institutional effect on born global firms in China: the role of Sun Tzu’s The Art of War strategies

2016 ◽  
Vol 10 (1) ◽  
pp. 1-19 ◽  
Author(s):  
Man Zhang ◽  
Qian Gao ◽  
Jane V. Wheeler ◽  
Jungsook Kwon
Keyword(s):  
Emerging Markets ◽  
Institutional Environment ◽  
Critical Role ◽  
Born Global ◽  
Internationalization Process ◽  
Content Type ◽  
International Performance ◽  
The Relationship ◽  
Born Global Firms

Purpose – This paper aims to investigate the role of Sun Tzu’s significant strategies on the relationship between the institutional environment and international performance of Chinese born global firms, a type of small- and medium-sized enterprise (SME) characterized by the company’s limited resources and its early efforts to internationalize. Design/methodology/approach – The methodology is based on a multi-case analysis of interviews conducted with four chosen born global firms, coupled with public database and Web site searches. Through the use of qualitative methods, propositions were developed. Findings – This paper provides insights regarding how the institutional environment, both formal and informal, has a strong positive relationship with born global firm’s international performance. Moreover, Sun Tzu’s significant strategies play a critical role in the internationalization process of born global firms in emerging markets. Originality/value – Although existing studies discuss the application of Eastern philosophical strategies adopted by firms in emerging markets, to the best of our knowledge, this is one of the earliest studies which evaluates the moderation effect of Sun Tzu’s significant strategies on the relationship between institutional environment and business performance. The paper contributes to scholarly discourse on the influencing factors of born global firm’s internationalization process. It also has practical relevance to international entrepreneurs and SMEs from emerging markets.

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