bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contribution of theMycobacterium tuberculosisMmpL Protein Family to Virulence and Drug Resistance
Authors: Domenech Pilar , Reed Michael B. , Barry Clifton E. 
Published: May 2005

ABSTRACTThe genome sequence ofMycobacterium tuberculosisrevealed the presence of 12 membrane proteins proposed to have a function in the transport of lipids. Insertional inactivation of 11 of these has revealed that only 1 (MmpL3) is apparently essential for viability. Five of these proteins are conserved within the genome ofMycobacterium leprae. The drug susceptibilities of these 11 mutants to a broad spectrum of agents are unaltered, suggesting that unlike their function in other organisms, these proteins do not play a significant role in intrinsic drug resistance. Each of these mutants was assessed for growth kinetics and lethality in a murine low-dose aerosol model of tuberculosis, and four were found to be impaired in one or both measures of virulence. Two of these, with mutations of MmpL4 and the previously characterized MmpL7, which transports phthiocerol dimycocerosate, were found to have both impaired growth kinetics and impaired lethality. Mutants with inactivation of MmpL8, which transports a precursor of the sulfatides, or MmpL11, which transports an unknown substrate, were found to establish infection normally but to be significantly attenuated for lethality in time-to-death studies. These studies support the concept that MmpL-mediated lipid secretion both contributes to the innate ability of the pathogen to survive intracellularly and also contributes directly to the host-pathogen dialogue that determines the ultimate outcome of infection.
Staphylococcus aureusStrains That Express Serotype 5 or Serotype 8 Capsular Polysaccharides Differ in Virulence
Authors: Watts Andrew , Ke Danbing , Wang Qun , Pillay Anil , Nicholson-Weller Anne , Lee Jean C. 
Published: May 2005

ABSTRACTMost isolates ofStaphylococcus aureusproduce a serotype 5 (CP5) or 8 (CP8) capsular polysaccharide. To investigate whether CP5 and CP8 differ in their biological properties, we created isogenic mutants ofS. aureusReynolds that expressed CP5, CP8, or no capsule. Biochemical analyses of CP5 and CP8 purified from the isogenicS. aureusstrains were consistent with published structures. The degree of O acetylation of each polysaccharide was similar, but CP5 showed a greater degree of N acetylation. Mice challenged with the CP5+strain showed a significantly higher bacteremia level than mice challenged with the CP8+strain. Similarly, the CP5+strain survived preferentially in the bloodstream and kidneys of infected mice challenged with a mixed inoculum containing both strains. The enhanced virulence of the CP5+strain in vivo correlated with its greater resistance to in vitro killing in whole mouse blood. Likewise, in vitro opsonophagocytic killing assays with human neutrophils and sera revealed greater survival of the Reynolds (CP5) strain, even though the kinetics of opsonization by C3b and iC3b was similar for both the CP5+and CP8+strains. Electron micrographs demonstrated C3 molecules on the cell wall beneath the capsule layer for both serotype 5 and 8 strains. Purified CP5 and CP8 stimulated a modest oxidative burst in human neutrophils but failed to activate the alternative complement pathway. These results indicate that CP5 and CP8 differ in a number of biological properties, and these differences likely contribute to the relative virulence of serotype 5 and 8S. aureusin vivo.
Identification and Characterization of an Autolysin-Encoding Gene of
Streptococcus mutans
Authors: Shibata Yukie , Kawada Miki , Nakano Yoshio , Toyoshima Kuniaki , Yamashita Yoshihisa 
Published: May 2005

ABSTRACT

We identified a gene (
atlA
) encoding autolytic activity from
Streptococcus mutans
Xc. The AtlA protein predicted to be encoded by
atlA
is composed of 979 amino acids with a molecular weight of 107,279 and has a conserved β-1,4-
N
-acetylmuramidase (lysozyme) domain in the C-terminal portion. Sodium dodecyl sulfate extracts of strain Xc showed two major bacteriolytic bands with molecular masses of 107 and 79 kDa, both of which were absent from a mutant with inactivated
atlA
. Western blot analysis revealed that the 79-kDa band was derived from the 107-kDa peptide by cleavage of its N-terminal portion. The inactivation of
atlA
resulted in a marked decrease in autolysis and the formation of very long chains of cells compared to the case for the parent strain. Although both the parent and mutant strains formed biofilms in the presence of sucrose, the biofilms formed by the mutant had a sponge-like architecture with large gaps and contained 30% less biomass than those formed by the parent strain. Furthermore, strain Xc formed glucose-dependent, loose biofilms in the absence of sucrose, but the mutant lost this ability. These results suggest that AtlA may play an important role in biofilm formation by
S. mutans
. The antibody produced against the C-terminal peptide containing the β-1,4-
N
-acetylmuramidase domain drastically inhibited the autolytic activity of strain Xc. This inhibition was specific among the oral streptococci to
S. mutans
. These results indicate that the catalytic domain of AtlA is located at the C terminus, suggesting that further characterization of this domain may provide a means to control cariogenic dental plaque formation.
Immunization of Volunteers withSalmonella entericaSerovar Typhi Strain Ty21a Elicits the Oligoclonal Expansion of CD8+T Cells with Predominant Vβ Repertoires
Authors: Salerno-Gonçalves Rosângela , Wahid Rezwanul , Sztein Marcelo B. 
Published: May 2005

ABSTRACTCD8+T cells are likely to play an important role in host defense againstSalmonella entericaserovar Typhi by several effector mechanisms, including lysis of infected cells (cytotoxicity) and gamma interferon (IFN-γ) secretion. In an effort to better understand these responses, we studied the T-cell receptor (TCR) repertoire of serovar Typhi-specific CD8+T cells in humans. To this end, we determined the TCR beta chain (Vβ) usage of CD8+T cells from three volunteers orally immunized with Ty21a typhoid vaccine by flow cytometry using a panel of monoclonal antibodies. Although TCR Vβ usage varied among volunteers, we identified oligoclonal Vβ subset expansions in individual volunteers (Vβ 2, 5.1, 8, 17, and 22 in volunteer 1; Vβ 1, 2, 5.1, 14, 17, and 22 in volunteer 2; and Vβ 3, 8, 14, and 16 in volunteer 3). These subsets were antigen specific, as shown by cytotoxicity and IFN-γ secretion assays on Vβ sorted cells and on T-cell clones derived from these volunteers. Moreover, eight-color flow cytometric analysis showed that these clones exhibited a T effector memory phenotype (i.e., CCR7−CD27−CD45RO+CD62L−) and coexpressed gut homing molecules (e.g., high levels of integrin α4β7, intermediate levels of CCR9, and low levels of CD103). In conclusion, our results show that long-term T-cell responses to serovar Typhi in Ty21a vaccinees are oligoclonal, involving multiple TCR Vβ families. Moreover, these serovar Typhi-specific CD8+T cells bearing defined Vβ specificities are phenotypically and functionally consistent with T effector memory cells with preferential gut homing potential.
Impairment of Protective Immunity to Blood-Stage Malaria by Concurrent Nematode Infection
Authors: Su Zhong , Segura Mariela , Morgan Kenneth , Loredo-Osti J. Concepcion , Stevenson Mary M. 
Published: May 2005

ABSTRACTHelminthiases, which are highly prevalent in areas where malaria is endemic, have been shown to modulate or suppress the immune response to unrelated antigens or pathogens. In this study, we established a murine model of coinfection with a gastrointestinal nematode parasite,Heligmosomoides polygyrus, and the blood-stage malaria parasitePlasmodium chabaudiAS in order to investigate the modulation of antimalarial immunity by concurrent nematode infection. Chronic infection with the nematode for 2, 3, or 5 weeks beforeP. chabaudiAS infection severely impaired the ability of C57BL/6 mice to control malaria, as demonstrated by severe mortality and significantly increased malaria peak parasitemia levels. Coinfected mice produced significantly lower levels of gamma interferon (IFN-γ) duringP. chabaudiAS infection than mice infected with malaria alone. Concurrent nematode infection also suppressed production of type 1-associated, malaria-specific immunoglobulin G2a. Mice either infected with the nematode alone or coinfected with the nematode and malaria had high transforming growth factor β1 (TGF-β1) levels, and concurrent nematode and malaria infections resulted in high levels of interleukin-10 in vivo. Splenic CD11c+dendritic cells (DC) from mice infected with malaria alone and coinfected mice showed similarly increased expression of CD40, CD80, and CD86, but DC from coinfected mice were unable to induce CD4+T-cell proliferation and optimal IFN-γ production in response to the malaria antigen in vitro. Importantly, treatment of nematode-infected mice with an anthelmintic drug prior to malaria infection fully restored protective antimalarial immunity and reduced TGF-β1 levels. These results demonstrate that concurrent nematode infection strongly modulates multiple aspects of immunity to blood-stage malaria and consequently impairs the development of protective antimalarial immunity.
Vaccination of Cattle with a CpG Oligodeoxynucleotide-Formulated Mycobacterial Protein Vaccine andMycobacterium bovisBCG Induces Levels of Protection against Bovine Tuberculosis Superior to Those Induced by Vaccination with BCG Alone
Authors: Wedlock D. Neil , Denis Michel , Skinner Margot A. , Koach Jessica , de Lisle Geoffrey W. , Vordermeier H. Martin , Hewinson R. Glyn , van Drunen Littel-van den Hurk Sylvia , Babiuk Lorne A. , Hecker Rolf , Buddle Bryce M. 
Published: May 2005

ABSTRACTThe development of a subunit protein vaccine for bovine tuberculosis which could be used either in combination withMycobacterium bovisBCG (to improve the efficacy of that vaccine) or alone would offer significant advantages over currently available strategies. A study was conducted with cattle to determine the protective efficacy of a strategy based on concurrent immunization with anM. bovisculture filtrate (CFP) vaccine and BCG compared to vaccination with either vaccine alone. One group of calves (10 animals per group) was vaccinated subcutaneously with CFP formulated with Emulsigen and combined with a CpG oligodeoxynucleotide (ODN). A second group was vaccinated with both the CFP vaccine and BCG injected at adjacent sites (CFP-BCG). One further group was vaccinated subcutaneously with BCG, while another group served as nonvaccinated control animals. Vaccination with CFP-BCG induced levels of antigen-specific gamma interferon (IFN-γ) and interleukin-2 (IL-2) in whole-blood cultures that were higher than those induced by vaccination with BCG alone. The combination of CFP and BCG did not enhance the production of antibodies toM. bovisCFP compared to vaccination with CFP alone. Vaccination with CFP alone led to delayed antigen-specific IFN-γ and IL-2 responses. Vaccination with CFP-BCG induced a high level of protection against an intratracheal challenge with virulentM. bovis, based on a significant enhancement of six pathological and microbiological parameters of protection compared with the nonvaccinated group. In contrast, vaccination with BCG alone induced a significant enhancement of protection in only one parameter, while CFP alone induced no protection. These results suggest that a combination of a CpG ODN-formulated protein vaccine and BCG offers better protection against bovine tuberculosis than does BCG alone.
Peripheral Blood and Pleural Fluid Mononuclear Cell Responses to Low-Molecular-Mass Secretory Polypeptides ofMycobacterium tuberculosisin Human Models of Immunity to Tuberculosis
Authors: Sable Suraj B. , Kumar Rajnish , Kalra Mamta , Verma Indu , Khuller G. K. , Dobos Karen , Belisle John T. 
Published: May 2005

ABSTRACTA total of 104 polypeptides were purified from the low-molecular-mass secretory proteome ofMycobacterium tuberculosisH37Rv using a combination of anion exchange column chromatography and high resolution preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by electroelution. The goal of this study was to identify polypeptides from a low-molecular-mass secretory proteome recognized by human subjects infected withM. tuberculosisand to ascertain the differences in specificity of antigen recognition by the peripheral blood mononuclear cells (PBMCs) and pleural fluid mononuclear cells (PFMCs) of these individuals. The study identified CFP-8 (Rv0496), CFP-11 (Rv2433c), CFP-14.5 (Rv2445c), and CFP-31 (Rv0831c) as novel T-cell antigens apart from previously characterized ESAT-6, TB10.4, CFP10, GroES, MTSP14, MTSP17, CFP21, MPT64, Ag85A, and Ag85B on the basis of recognition by PBMCs of tuberculosis contacts and treated tuberculosis patients. Further, polypeptides prominently recognized by PFMCs of tuberculous pleurisy patients were the same as those recognized by PBMCs of healthy contacts and treated tuberculosis patients. The results of our study indicate the homogeneity of antigenic target recognition by lymphocytes at the site of infection and at the periphery in the human subjects studied and the need to evaluate these antigenic targets as components of future antituberculous vaccines.
Cytolethal Distending Toxin Is Essential forHelicobacter hepaticusColonization in Outbred Swiss Webster Mice
Authors: Ge Zhongming , Feng Yan , Whary Mark T. , Nambiar Prashant R. , Xu Shilu , Ng Vivian , Taylor Nancy S. , Fox James G. 
Published: May 2005

ABSTRACTHelicobacter hepaticus, which induces chronic hepatitis and typhlocolitis in susceptible mouse strains, produces a cytolethal distending toxin (CDT) consisting of CdtA, CdtB, and CdtC. AcdtB-deficientH. hepaticusisogenic mutant (HhcdtBm7) was generated and characterized for colonization parameters in four intestinal regions (jejunum, ileum, cecum, and colon) of outbred Swiss Webster (SW) mice. Inactivation of thecdtBgene abolished the ability of HhcdtBm7 to colonize female mice at both 8 and 16 weeks postinfection (wpi), whereas HhcdtBm7 colonized all of four intestinal regions of three of five males at 8 wpi and then was eliminated by 16 wpi. Wild-type (WT)H. hepaticuswas detected in the corresponding intestinal regions of both male and female mice at 8 and 16 wpi; however, colonization levels of WTH. hepaticusin the cecum and colon of male mice were approximately 1,000-fold higher than in females (P< 0.0079) at 16 wpi. Infection with WTH. hepaticus, but not HhcdtBm7, at 8 wpi was associated with significantly increased mRNA level of ileal and cecal gamma interferon (IFN-γ) in females (P< 0.016 and 0.031 between WTH. hepaticus-infected and sham-dosed females, respectively). In contrast, the mRNA levels of IFN-γ were significantly higher in the colon (P< 0.0079) and trended to be higher in the cecum (P< 0.15) in the HhcdtBm7-colonized male mice versus the sham-dosed controls at 8 wpi. In addition, mRNA levels of ileal IFN-γ were significantly higher in the control females than males at 8 wpi (P< 0.016). There were significantly higher Th1-associated immunoglobulin G2a (IgG2a), Th2-associated IgG1 and mucosal IgA (P< 0.002, 0.002, 0.002, respectively) responses in the mice infected with WTH. hepaticuswhen compared to HhcdtBm7 at 16 wpi. Colonic interleukin-10 (IL-10) expressions at 16 wpi were significantly lower in both female and male mice colonized by WTH. hepaticusor in males transiently colonized through 8 wpi by HhcdtBm7 versus control mice (P< 0.0159). These lines of evidence indicate that (i)H. hepaticusCDT plays a crucial role in the persistent colonization ofH. hepaticusin SW mice; (ii) SW female mice are more resistant toH. hepaticuscolonization than male mice; (iii) there was persistent colonization of WTH. hepaticusin cecum, colon, and jejunum but only transient colonization ofH. hepaticusin the ileum of female mice; (iv)H. hepaticuscolonization was associated with down-regulation of colonic IL-10 production.
Inducible Antisense RNA Expression in the Characterization of Gene Functions in
Streptococcus mutans
Authors: Wang Bing , Kuramitsu Howard K. 
Published: May 2005

ABSTRACT

In order to examine gene function in
Streptococcus mutans
, we have recently initiated an antisense RNA strategy. Toward this end, we have now constructed and evaluated three
Escherichia coli-S. mutans
shuttle expression vectors with the
fruA
and
scrB
promoters from
S.
mutans
, as well as the
tetR
-controlled
tetO
promoter from
Staphylococcus aureus
. Among these, the
tetO
/
tetR
system proved to be the most tightly controlled promoter. By using this shuttle plasmid system, modulation of gene function by inducible antisense RNA expression was demonstrated for
comC
antisense fragments of different sizes as well as for distinct
gtfB
antisense fragments. It was demonstrated that the size, but not the relative position, of an antisense DNA fragment is important in mediating the antisense phenomenon. Furthermore, by constructing and screening random DNA libraries with the
tet
expression shuttle system, 78 growth-retarded transformants harboring antisense DNA fragments were also identified. Almost all of them corresponded to homologous essential genes in other bacteria. In addition, a novel essential gene, the
coaE
gene, encoding dephospho-coenzyme A kinase, which is involved in the final step of coenzyme A catabolism in
S. mutans
, was identified and characterized. These results suggest that the antisense RNA strategy can be useful for identifying novel essential genes in
S. mutans
bacteria as well as further characterizing the physiology (including potential virulence factors) of these organisms.
Gamma Interferon-Induced T-Cell Loss in VirulentMycobacterium aviumInfection
Authors: Flórido Manuela , Pearl John E. , Solache Alejandra , Borges Margarida , Haynes Laura , Cooper Andrea M. , Appelberg Rui 
Published: May 2005

ABSTRACTInfection by virulentMycobacterium aviumcaused progressive severe lymphopenia in C57BL/6 mice due to increased apoptosis rates. T-cell depletion did not occur in gamma interferon (IFN-γ)-deficient mice which showed increased T-cell numbers and proliferation; in contrast, deficiency in nitric oxide synthase 2 did not prevent T-cell loss. Although T-cell loss was IFN-γ dependent, expression of the IFN-γ receptor on T cells was not required for depletion. Similarly, while T-cell loss was optimal if the T cells expressed IFN-γ, CD8+T-cell depletion could occur in the absence of T-cell-derived IFN-γ. Depletion did not require that the T cells be specific for mycobacterial antigen and was not affected by deficiencies in the tumor necrosis factor receptors p55 or p75, the Fas receptor (CD95), or the respiratory burst enzymes or by forced expression ofbcl-2in hematopoietic cells.
Safety and Enhanced Immunogenicity of a Hepatitis B Core ParticlePlasmodium falciparumMalaria Vaccine Formulated in Adjuvant Montanide ISA 720 in a Phase I Trial
Authors: Oliveira Giane A. , Wetzel Kristiane , Calvo-Calle J. Mauricio , Nussenzweig Ruth , Schmidt Annette , Birkett Ashley , Dubovsky Filip , Tierney Eveline , Gleiter Christoph H. , Boehmer Gabriele , Luty Adrian J. F. , Ramharter Michael , Thornton George B. , Kremsner Peter G. , Nardin Elizabeth H. 
Published: May 2005

ABSTRACTHighly purified subunit vaccines require potent adjuvants in order to elicit optimal immune responses. In a previous phase I trial, an alum formulation of ICC-1132, a malaria vaccine candidate comprising hepatitis B core (HBc) virus-like particle containingPlasmodium falciparumcircumsporozoite (CS) protein epitopes, was shown to elicitPlasmodium falciparum-specific antibody and cellular responses. The present study was designed as a single-blind, escalating-dose phase I trial to evaluate the safety and immunogenicity of single intramuscular doses of ICC-1132 formulated in the more potent water-in-oil adjuvant Montanide ISA 720 (ICC-1132/ISA 720). The vaccine was safe and well tolerated, with transient injection site pain as the most frequent complaint. All vaccinees that received either 20 μg or 50 μg of ICC-1132/ISA 720 developed antiimmunogen and anti-HBc antibodies. The majority of volunteers in these two groups developed sporozoite-specific antibodies, predominantly of opsonizing immunoglobulin G subtypes. Peak titers and persistence of parasite-specific antibody following a single injection of the ISA 720 formulated vaccine were comparable to those obtained following two to three immunizations with alum-adsorbed ICC-1132. Peripheral blood mononuclear cells of ICC-1132/ISA 720 vaccinees proliferated and released cytokines (interleukin 2 and gamma interferon) when stimulated with recombinantP. falciparumCS protein, and CS-specific CD4+T-cell lines were established from volunteers with high levels of antibodies to the repeat region. The promising results obtained with a single dose of ICC-1132 formulated in Montanide ISA 720 encourage further clinical development of this malaria vaccine candidate.
Human Immune Response to a Plague Vaccine Comprising Recombinant F1 and V Antigens
Authors: Williamson E. D. , Flick-Smith H. C. , LeButt C. , Rowland C. A. , Jones S. M. , Waters E. L. , Gwyther R. J. , Miller J. , Packer P. J. , Irving M. 
Published: May 2005

ABSTRACT

The human immune response to a new recombinant plague vaccine, comprising recombinant F1 (rF1) and rV antigens, has been assessed during a phase 1 safety and immunogenicity trial in healthy volunteers. All the subjects produced specific immunoglobulin G (IgG) in serum after the priming dose, which peaked in value after the booster dose (day 21), with the exception of one individual in the lowest dose level group, who responded to rF1 only. Three subjects, found to have an anti-rV titer at screening, were excluded from the overall analysis. Human antibody functionality has been assessed by quantification of antibody competing for binding to rV in vitro and also by the transfer of protective immunity in human serum into the naïve mouse. Human and macaque IgG competed for binding to rV in vitro with a mouse monoclonal antibody, previously shown to protect mice against challenge with plague, suggesting that this protective B-cell epitope on rV is conserved between these three species. Total IgG to rV in individuals and the titer of IgG competing for binding to rV correlated significantly at days 21 (
r
= 0.72;
P
< 0.001) and 28 (
r
= 0.82;
P
< 0.001). Passive transfer of protective immunity into mice also correlated significantly with total IgG titer to rF1 plus rV at days 21 (
r
2
= 98.6%;
P
< 0.001) and 28 (
r
2
= 76.8%;
P
< 0.03). However, no significant vaccination-related change in activation of peripheral blood mononuclear cells was detected at any time. Potential serological immune correlates of protection have been investigated, but no trends specific to vaccination could be detected in cellular markers.