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Factors contributing to stress adaptation of human pathogen Bordetella pertussis
Hejnarová, Václava ; Večerek, Branislav (advisor) ; Černý, Ondřej (referee)
The role of bivalent metals as cofactors in various enzymes is essential for all domains of life. Their importance can be seen in interactions of hosts with patogens such as Bor- detella pertussis. This bacterium has several mechanisms that protect it from oxidative stress in phagosomes of immune cells. One example is Mn-dependent enzyme superoxide dismutase. Phagosome itself is an environment with limiting concentrations of several key bivalent metals. Thus, the transport of these metals must be controlled to ensure sufficent concentration for enzymatic activity and prevent from toxic cumulation and mismetallation. This study focuses on a particular locus BP3083-BP3077 that is highly expressed in B. pertussis surviving after internalization by THP-1 macrophages. The locus consists of two transporters, one of which shares homology with SitABCD Mn2` impor- ter of Salmonella enterica and is regulated by Fur family repressor. Bacterial cells were exposed to toxic concentrations of several bivalent metals and the level of gene expres- sion was studied by RT-qPCR. Deletion mutants were used for examination of bacterial phenotype. Results of the study show that the locus encodes Mn2` and Co2` transporters and becomes negatively regulated by Fur family repressor in toxic concentration of Co2` . The...
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Identification of residues of acylated domain of RTX toxins involved in acyltransferase binding
Grobarčíková, Michaela ; Mašín, Jiří (advisor) ; Černý, Ondřej (referee)
Both adenylate cyclase toxin (CyaA) and α-hemolysin (HlyA) are members of Repeats in ToXins (RTX) cytolysins that play key roles in the virulence of Bordetella pertussis and Escherichia coli, respectively. Bacterial RTX toxins represent a growing group of proteins produced by gram- negative bacteria. These pore-forming RTX toxins share several notable common features: (1) they require post-translational activation by attachment of fatty acid chains to two lysine residues; (2) they contain a hydrophobic domain that forms cation-selective pores in target cell membranes; (3) they are secreted by a type I secretion system; (4) after secretion, they become biologically active by binding of Ca2+ to the nonapeptide glycine- and aspartate-rich repeats. CyaA translocates a unique AC enzyme to the cytosol of phagocytes and subverts their bactericidal functions by unregulated conversion of ATP to cAMP. CyaA and HlyA also permeabilize the cell membrane of eukaryotic cells through cation-selective pores. Both toxins preferentially bind to cells expressing β2 integrins but can also interact with a variety of cells that do not express integrins or with naked lipid membranes. Both toxins are activated from protoxin form by post- translational acylation mediated by a specific acyltransferase. CyaA is activated by...
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Structural-functional aspects of the Bordetella pertussis adenylate cyclase toxin
Březinová, Karolína ; Bumba, Ladislav (advisor) ; Brzobohatá, Hana (referee)
Whooping cough (pertussis) is a highly infectious respiratory disease caused by the Gram-negative bacterium Bordetella pertussis. Even though the vaccination rate of the population is high, pertussis is one of the most widespread vaccine-preventable diseases. The bacterium produces a variety of virulence factors that facilitate the process of colonization of the ciliated epithelium and infection of the upper respiratory tract. Among the most important virulence factors is the adenylate cyclase toxin (CyaA). This toxin belongs to the so- called RTX (Repeat-In-ToXins) proteins, which are released from the bacterium using the Type 1 secretion apparatus (T1SS). CyaA is a multifunctional toxin, showing both hemolytic and cytotoxic activity. The cytotoxic activity is caused by the N-terminal adenylyl cyclase (AC) domain, which is translocated across the cytoplasmic membrane into the cell cytosol, where upon interaction with calmodulin catalyzes the uncontrolled conversion of adenosine triphosphate (ATP) to cyclic adenosine-3',5'-monophosphate (cAMP). CyaA is recognized by the integrin receptor CD11b/CD18 (also known as complement receptor type 3), which is primarily found on phagocytic cells of the host organism. This work focuses on the structural- functional aspects of the CyaA toxin and summarizes...
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Application of human monocytic cell line THP-1 for study of pathogenesis in whooping cough agent Bordetella pertussis
Čurnová, Ivana ; Petráčková, Denisa (advisor) ; Mašín, Jiří (referee)
Bordetella pertussis is strictly human pathogen that causes severe infection of the respiratory tract known as whooping cough, which is currently on the rise. B. pertussis was considered as an extracellular pathogen for a very long time. Recently it was shown the ability of B. pertussis to survive inside early endosomes of macrophages. This ability is studied in the human monocytic cell line THP-1 and also in primary macrophages from human donors. This diploma thesis is focused on THP-1 infectious model and mainly for the early phase of infection. A previously performed transcriptomic study showed significantly affected genes of B. pertussis during intracellular survival in THP-1 macrophages. In this study, we selected genes that are in some way related to intracellular survival inside human macrophages or have significantly effect for intracellular survival. The effect of the mutation in these genes was tested both on the level of cytotoxicity to THP-1 cells and the related number of surviving bacteria inside the macrophages. The deletion strain in two genes for cysteine dioxygenase (BP2871 and BP3011) and the mutant strain allocated in the Bvg+ phase were less cytotoxic than the control strain. Monitoring the effect of opsonization to intracellular survival have not such clear results. The effect...
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Mechanisms underlying subversion of host immunity by Bordetella pertussis
Klímová, Nela ; Bumba, Ladislav (advisor) ; Černý, Jan (referee) ; Filipp, Dominik (referee)
Bordetella pertussis is a Gram-negative human-adapted pathogen of the respiratory tract and the causative agent of the whooping cough (pertussis) illness. The bacterium produces a number of virulence factors, of which adenylate cyclase toxin (ACT) and pertussis toxin (PT) play important roles in manipulation of host immune response and establishment of the early catarrhal stage of infection. Although the toxins exert their cytotoxic activity by elevation of intracellular cAMP levels, both are distinct from each other in terms of their structures, mechanisms of secretion and cell intoxication, as well as in their ability to modulate the adaptive immune response of the host. The aim of this thesis was to determine the structure- function relationship underlying the mechanism of the Type I secretion system (T1SS)- mediated secretion of ACT and to decipher the immunomodulatory properties of ACT and PT in the course of B. pertussis infection. Integrative structural biology approaches revealed that the RTX domain of ACT consists of a contiguous assembly of five Ca2+ -loaded β-roll blocks, whose co-secretional folding constitute an intramolecular Brownian ratchet that prevents backsliding of the translocating polypeptide in the T1SS conduit, thus accelerating the secretion of ACT from bacterial cells by a...
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Immunomodulation of dendritic cells by adenylate cyclase toxin from B. pertussis
Jáňová, Hana ; Adkins, Irena (advisor) ; Brdička, Tomáš (referee)
Adenylate cyclase toxin (CyaA) produced by the causative agent of whooping cough Bordetella pertussis, is a key virulence factor important for colonization of the host. CyaA targets preferentially myeloid phagocytes expressing CD11b/CD18 integrin. By elevating cytosolic cAMP in the host cells, CyaA interferes with their phagocytic, chemotactic and oxidative burst capacities. Furthermore, CyaA modulates the secretion of cytokines and the maturation state in LPS-stimulated dendritic cells (DC) by affecting the expression of costimulatory molecules. In this study, we investigated the effects of CyaA on the capacity of murine bone-marrow DC to prime CD4+ and CD8+ T cells in response to ovalbumin epitopes delivered by the CyaA-AC- toxoid, as a model antigen. Further, we examined the possible impact of CyaA on the antigen uptake and processing for MHC class I and II-restricted presentation by DC, as we previously observed a decreased T cell stimulatory capacity of CyaA-treated DC in response to soluble ovalbumin. We found out that the high levels of cAMP generated by CyaA in LPS-stimulated DC account for the decreased presentation of ovalbumin epitopes carried by CyaA-AC- toxoid on MHC class I and II molecules, thereby impairing the CD8+ and CD4+ T cell responses. Whereas CyaA did not influence the...
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Adenylate cyclase toxin of Bordetella pertussis, its conformation and ion balance in host cell.
Motlová, Lucia ; Konopásek, Ivo (advisor) ; Krůšek, Jan (referee)
Adenylate cyclase (CyaA, ACT) toxin is one of the major virulence factors of Bordetella pertussis. Although CyaA binds to many types of membranes, it is assumed that the integrin CD11b/CD18 is its receptor which is expressed on the surface of myeloid cells. CyaA belongs to the family of RTX toxin-hemolysins. CyaA acts on the host cells by two independent activities. One of them is the conversion of ATP to cyclic AMP, which is catalyzed by adenylate cyclase (AC) domain after its translocation into the cytosol of the host cell, which leads to the entry of calcium cations into the host cell. Translocation is probably initiated by interaction of CyaA monomer with the target membrane. The second activity is the formation of CyaA channel selective for cations, which probably causes colloid osmotic lysis of target cells. The channel forming activity is provided by RTX hemolysin domain which most probably forms oligomers, although it was found that CyaA as a monomer causes leakage of potassium cations from the host cell. It is also not clear whether the oligomerization of CyaA would occur in solution, or after interaction with the host membrane. The aim of this study was to examine the flow of sodium ions on the membrane of murine macrophages J774A.1, which express integrin CD11b/CD18 on their surface....
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Expression and purification of N-terminal fragment of filamentous hemagglutinin from Bordetella Pertussis in E. Coli
Jurnečka, David ; Stiborová, Marie (advisor) ; Kavan, Daniel (referee)
: Whooping cough is highly contagious disease caused by gram-negative bacteria Bordetella pertussis. During infection the bacteria produces many types of toxins and adhesive molecules including a filamentous hemagglutinin(FHA). FHA is 220 kDa surface-exposed and secreted protein, which plays a key role in host-cell interactions. The project aims at construction of heterologous expression system for production of the N-terminal part of B. pertussis FHA (FHA1-862) in E. coli. The expression vector is composed of system of two independent T7/Lac promoters and enables secretion of FHA1-862 into the culture media. Downstream of the first promoter is fhaB gene encoding FHA1-862 and the letter is followed by fhaC gen encoding the FhaC transport protein, which allows translocation of FHA from periplasmic space to extracellular milieu. FHA1-862 was successfully secreted in E. coli strain BL21 carrying plasmid pMM100 (Laclq) at 30 řC and purified by affinity chromatography on Cellufine resin. These results indicate that FHA1-862 protein can be produced in E. coli, however, the system is inefficient and the yield of the protein is very low. (In Czech)
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Signalization of adenylate cyclase toxin of Bordetella pertussis in macrophages.
Černý, Ondřej ; Kamanová, Jana (advisor) ; Kuthan, Martin (referee)
Adenylate cyclase toxin (CyaA) is a key virulence factor of Bordetella pertussis, the causative agent of whooping cough. The toxin targets primarily myeloid phagocytes expressing CD11b/CD18 (αMβ2, CR3, Mac-1) and by elevation of cytosolic cAMP levels it paralyses their macropinocytic and opsono-phagocytic functions. Here, we dissected the cAMP-regulated pathway responsible for the block of macrophage macropinocytosis and characterized the capacity of CyaA-treated macrophages to shut- down Akt (protein kinase B, PKB) signaling; that controls nitric oxide (NO) production by macrophages. By using specific activators of protein kinase A (PKA) and for the exchange protein activated by cAMP (Epac), we show that activation of the cAMP effector Epac inhibits macropinocytosis in macrophages. Moreover, upon transfection of macrophages by the constitutively active and dominant negative variants of a downstream effector of Epac, the small GTPase Rap1, inhibition or upregulation of macrophage macropinocytosis was observed, respectively. It was reported previously that the Epac/Rap1 pathway regulates activity of tyrosin phosphatase SHP-1 as well as of protein phosphatase 2 A (PP2A). We show that inhibition of both tyrosin phosphatases and PP2A interferes with CyaA-mediated block of macropinocytosis. These...
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Bordetella pertussis and whooping cough: Bacterium and its virulence factors, epidemiology of disease and vaccination strategy.
Bočková, Barbora ; Holubová, Jana (advisor) ; Seydlová, Gabriela (referee)
Bordetella pertussis, a gram-negative bacterium, is a human pathogen which affects the upper respiratory tract. It is the causative agent of whooping cough or pertussis. B. pertussis produces several virulence factors consisting of toxins and adhesins. Whole cell vaccine and subsequent acellular vaccine were developed against pertussis in the past. However, a gradual increase of pertussis incidences has been reported in the last twenty years. This thesis provides basic information about B. pertussis and whooping cough. The main aim of the herein presented work is to summarize the contemporary epidemiologic situation along with determining reasons for increased pertussis cases. In addition, possible solutions for the present situation are proposed.
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