bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphine Withdrawal Lowers Host Defense to Enteric Bacteria: Spontaneous Sepsis and Increased Sensitivity to OralSalmonella entericaSerovar Typhimurium Infection
Authors: Feng Pu , Truant Allan L. , Meissler Joseph J. , Gaughan John P. , Adler Martin W. , Eisenstein Toby K. 
Published: August 2006

ABSTRACTUnderstanding the consequences of drug withdrawal on immune function and host defense to infection is important. We, and others, previously demonstrated that morphine withdrawal results in immunosuppression and sensitizes to lipopolysaccharide-induced septic shock. In the present study, the effect of morphine withdrawal on spontaneous sepsis and on oral infection withSalmonella entericaserovar Typhimurium was examined. Mice were chronically exposed to morphine for 96 h by implantation of a slow-release morphine pellet. Abrupt withdrawal was induced by removal of the pellet. In the sepsis model, bacterial colonization was examined and bacterial species were identified by necropsy of various tissues. It was found that at 48 h postwithdrawal, morphine-treated mice had enteric bacteria that were detected in the Peyer's patches (4/5), mesenteric lymph nodes (4/5), spleens (4/10), livers (6/10), and peritoneal cavities (8/10). In placebo pellet-withdrawn mice, only 2/40 cultures were positive. The most frequently detected organisms in tissues of morphine-withdrawn mice wereEnterococcus faeciumfollowed byKlebsiella pneumoniae. Both organisms are part of the normal gastrointestinal flora. In the infection model, mice were orally inoculated withS. enterica24 h post-initiation of abrupt withdrawal from morphine. Withdrawal significantly decreased the mean survival time and significantly increased theSalmonellaburden in various tissues of infected mice compared to placebo-withdrawn animals. Elevated levels of the proinflammatory cytokines were observed in spleens of morphine-withdrawn mice, compared to placebo-withdrawn mice. These findings demonstrate that morphine withdrawal sensitizes to oral infection with a bacterial pathogen and predisposes mice to bacterial sepsis.
Comparison of the Host Responses to Wild-Type andcpsBMutantKlebsiella pneumoniaeInfections
Authors: Lawlor Matthew S. , Handley Scott A. , Miller Virginia L. 
Published: August 2006

ABSTRACTPreviously, we established an intranasal mouse model ofKlebsiella pneumoniaeinfection and validated its utility using a highly virulent wild-type strain and an avirulent capsular polysaccharide mutant. In the present study we compare the host responses to both infections by examining cytokine production, cellular infiltration, pulmonary histology, and intranasal immunization.
Anthrax Lethal Toxin Impairs Innate Immune Functions of Alveolar Macrophages and Facilitates
Bacillus anthracis
Survival
Authors: Ribot Wilson J. , Panchal Rekha G. , Brittingham Katherine C. , Ruthel Gordon , Kenny Tara A. , Lane Douglas , Curry Bob , Hoover Timothy A. , Friedlander Arthur M. , Bavari Sina 
Published: August 2006

ABSTRACT

Alveolar macrophages (AM) are very important for pulmonary innate immune responses against invading inhaled pathogens because they directly kill the organisms and initiate a cascade of innate and adaptive immune responses. Although several factors contribute to inhalational anthrax, we hypothesized that unimpeded infection of
Bacillus anthracis
is directly linked to disabling the innate immune functions contributed by AM. Here, we investigated the effects of lethal toxin (LT), one of the binary complex virulence factors produced by
B. anthracis
, on freshly isolated nonhuman primate AM. Exposure of AM to doses of LT that killed susceptible macrophages had no effect on the viability of AM, despite complete MEK1 cleavage. Intoxicated AM remained fully capable of
B. anthracis
spore phagocytosis. However, pretreatment of AM with LT resulted in a significant decrease in the clearance of both the Sterne strain and the fully virulent Ames strain of
B. anthracis
, which may have been a result of impaired AM secretion of proinflammatory cytokines. Our data imply that cytolysis does not correlate with MEK1 cleavage, and this is the first report of LT-mediated impairment of nonhuman primate AM bactericidal activity against
B. anthracis
.
Opacity-Associated Adhesin Repertoire in Hyperinvasive
Neisseria meningitidis
Authors: Callaghan Martin J. , Jolley Keith A. , Maiden Martin C. J. 
Published: August 2006

ABSTRACT

The opacity (Opa) proteins mediate a variety of interactions between the bacterium
Neisseria meningitidis
and its human host. These interactions are thought to be of central importance in both the asymptomatic colonization of the nasopharynx and the sporadic occurrence of meningococcal disease. The receptor specificities of a limited number of Opa protein variants have been explored, but the high level of amino acid sequence diversity among variants has complicated the assignment of specific roles to individual Opa variants or combinations of variants. In addition, the distribution of Opa protein variants among diverse meningococci, information that is potentially informative for studies of Opa function, is poorly understood. A systematic survey of the genetic diversity in the four
opa
gene loci in each of 77 meningococcal isolates was undertaken. These isolates were representative of the seven hyperinvasive meningococcal clonal complexes that caused the majority of meningococcal disease over the last 50 years. Consistent with previous studies, a high level of sequence diversity was observed among the
opa
genes and the proteins that they encoded; however, particular sets of Opa protein variants were consistently associated with each of the clonal complexes over time periods often spanning decades and during global spread. These observations were consistent with the postulate that particular combinations of Opa proteins confer fitness advantages to individual clonal complexes and have implications for studies of Opa function and the inclusion of Opa proteins in novel meningococcal vaccines.
Mechanisms of Resistance ofPorphyromonas gingivalisto Killing by Serum Complement
Authors: Slaney Jennifer M. , Gallagher Alexandra , Aduse-Opoku Joseph , Pell Keith , Curtis Michael A. 
Published: August 2006

ABSTRACTThe complement system plays an important role in the host defense against infection, and the formation of the terminal complement complex on the bacterial surface has been shown to be particularly important in killing of gram-negative bacteria. The gram-negative periodontal pathogenPorphyromonas gingivalisis resistant to complement killing, and possible mechanisms suggested for this resistance include protease production and capsule formation. In this study,P. gingivalisArg- and Lys-gingipain deletion mutants and polysaccharide synthesis deletion mutants have been used to investigate these hypotheses. When Arg- and Lys-gingipain protease mutants were incubated in 20% normal human serum, deposition of complement components on the cell surface was significantly increased compared to that for the wild-type organism. However, despite the increased deposition, the protease mutants maintained resistance to killing and their viability was equal to that seen with heat-inactivated serum. Similar data were obtained when the wild-type organism was treated with gingipain protease inhibitors. K-antigen expression mutants were also resistant to killing. However, mutants which no longer synthesized a surface anionic polysaccharide (APS) (a phosphorylated branched mannan) were extremely sensitive to serum killing. These mutants lack the organized dense glycan surface layer present on the parent strain on the basis of electron microscopy. We conclude that the production of APS at the surface ofP. gingivalisrather than Arg- and Lys-gingipain synthesis is the principal mechanism of serum resistance inP. gingivalis.
Thioredoxin 1 Promotes Intracellular Replication and Virulence of
Salmonella enterica
Serovar Typhimurium
Authors: Bjur Eva , Eriksson-Ygberg Sofia , Åslund Fredrik , Rhen Mikael 
Published: August 2006

ABSTRACT

The effect of the cytoplasmic reductase and protein chaperone thioredoxin 1 on the virulence of
Salmonella enterica
serovar Typhimurium was evaluated by deleting the
trxA
,
trxB
, or
trxC
gene of the cellular thioredoxin system, the
grxA
or
gshA
gene of the glutathione/glutaredoxin system, or the
dsbC
gene coding for a thioredoxin-dependent periplasmic disulfide bond isomerase. Mutants were tested for tolerance to oxidative and nitric oxide donor substances in vitro, for invasion and intracellular replication in cultured epithelial and macrophage-like cells, and for virulence in BALB/c mice. In these experiments only the
gshA
mutant, which was defective in glutathione synthesis, exhibited sensitization to oxidative stress in vitro and a small decrease in virulence. In contrast, the
trxA
mutant did not exhibit any growth defects or decreased tolerance to oxidative or nitric oxide stress in vitro, yet there were pronounced decreases in intracellular replication and mouse virulence. Complementation analyses using defined catalytic variants of thioredoxin 1 showed that there is a direct correlation between the redox potential of thioredoxin 1 and restoration of intracellular replication of the
trxA
mutant. Attenuation of mouse virulence that was caused by a deficiency in thioredoxin 1 was restored by expression of wild-type thioredoxin 1 in
trans
but not by expression of a catalytically inactive variant. These results clearly imply that in
S. enterica
serovar Typhimurium, the redox-active protein thioredoxin 1 promotes virulence, whereas in vitro tolerance to oxidative stress depends on production of glutathione.
Legionella pneumophila
Mip, a Surface-Exposed Peptidylproline
cis-trans
-Isomerase, Promotes the Presence of Phospholipase C-Like Activity in Culture Supernatants
Authors: DebRoy Sruti , Aragon Virginia , Kurtz Sherry , Cianciotto Nicholas P. 
Published: August 2006

ABSTRACT

The type II secretion system of
Legionella pneumophila
promotes pathogenesis. Among the
Legionella
type II-dependent exoenzymes is a
p
-nitrophenol phosphorylcholine (
p
-NPPC) hydrolase whose activity is only partially explained by the PlcA phospholipase C. In a screen to identify other factors that promote secreted hydrolase activity, we isolated a
mip
mutant.
L. pneumophila
Mip is a surface-exposed, FK506-binding protein that is needed for optimal infection and has peptidylproline
cis-trans
-isomerase (PPIase) activity. Since the molecular target of Mip was undefined, we investigated a possible relationship between Mip and the secreted
p-
NPPC hydrolase activity. In the
mip
mutant there was a 40 to 70% reduction in secreted activity that was successfully complemented by providing
mip
on a plasmid. A similar phenotype was observed when we examined four other independently derived
mip
mutants, and in all cases the defect was complemented by reintroduction of
mip
. Thus,
mip
promotes the presence of a
p
-NPPC hydrolase activity in culture supernatants. We also found that the C terminus of Mip is required for this effect. When supernatants were examined by anion-exchange chromatography, the
p
-NPPC hydrolase activity associated with Mip proved to be type II dependent but distinct from PlcA. This conclusion was supported by the phenotype of a newly constructed
mip plcA
double mutant. Thus, Mip promotes the elaboration of a new type II exoprotein. These data provide both the first evidence for a target for Mip and the first indication that a surface PPIase is involved in the secretion or activation of proteins beyond the outer membrane.
Identification of In Vivo-Induced Bacterial Protein Antigens during Human Infection with
Salmonella enterica
Serovar Typhi
Authors: Harris Jason B. , Baresch-Bernal Andrea , Rollins Sean M. , Alam Ashfaqul , LaRocque Regina C. , Bikowski Margaret , Peppercorn Amanda F. , Handfield Martin , Hillman Jeffery D. , Qadri Firdausi , Calderwood Stephen B. , Hohmann Elizabeth , Breiman Robert F. , Brooks W. Abdullah , Ryan Edward T. 
Published: August 2006

ABSTRACT

We applied an immunoscreening technique, in vivo-induced antigen technology (IVIAT), to identify immunogenic bacterial proteins expressed during human infection with
Salmonella enterica
serovar Typhi, the cause of typhoid fever. We were able to assign a functional classification to 25 of 35 proteins identified by IVIAT. Of these 25, the majority represent proteins with known or potential roles in the pathogenesis of
S. enterica
. These include proteins implicated in fimbrial structure and biogenesis, antimicrobial resistance, heavy metal transport, bacterial adhesion, and extracytoplasmic substrate trafficking as well as secreted hydrolases. The 10 remaining antigens represent proteins with unknown functions. Of the 35 identified antigens, four had no immunoreactivity when probed with control sera from individuals never exposed to serovar Typhi organisms; these four included PagC, TcfB, and two antigens of unknown function encoded by STY0860 and STY3683. PagC is a virulence factor known to be upregulated in vivo in
S. enterica
serovar Typhimurium infection of mice. TcfB is the major structural subunit of a fimbrial operon found in serovar Typhi with no homolog in serovar Typhimurium organisms. By examining differential immunoreactivities in acute- versus convalescent-phase human serum samples, we found specific anti-PagC and anti-TcfB immunoglobulin G responses in patients with serovar Typhi bacteremia. Serovar Typhi antigens identified by IVIAT warrant further evaluation for their contributions to pathogenesis, and they may have diagnostic, therapeutic, or preventive uses.
Dissecting the Contributions of
Clostridium perfringens
Type C Toxins to Lethality in the Mouse Intravenous Injection Model
Authors: Fisher Derek J. , Fernandez-Miyakawa Mariano E. , Sayeed Sameera , Poon Rachael , Adams Victoria , Rood Julian I. , Uzal Francisco A. , McClane Bruce A. 
Published: August 2006

ABSTRACT

The gram-positive anaerobe
Clostridium perfringens
produces a large arsenal of toxins that are responsible for histotoxic and enteric infections, including enterotoxemias, in humans and domestic animals.
C. perfringens
type C isolates, which cause rapidly fatal diseases in domestic animals and enteritis necroticans in humans, contain the genes for alpha toxin (
plc
), perfringolysin O (
pfoA
), beta toxin (
cpb
), and sometimes beta2 toxin (
cpb2
) and/or enterotoxin (
cpe
). Due to the economic impact of type C-induced diseases, domestic animals are commonly vaccinated with crude type C toxoid (prepared from inactivated culture supernatants) or bacterin/toxoid vaccines, and it is not clear which toxin(s) present in these vaccines actually elicits the protective immune response. To improve type C vaccines, it would be helpful to assess the contribution of each toxin present in type C supernatants to lethality. To address this issue, we surveyed a large collection of type C isolates to determine their toxin-producing abilities. When late-log-phase vegetative culture supernatants were analyzed by quantitative Western blotting or activity assays, most type C isolates produced at least three lethal toxins, alpha toxin, beta toxin, and perfringolysin O, and several isolates also produced beta2 toxin. In the mouse intravenous injection model, beta toxin was identified as the main lethal factor present in type C late-log-phase culture supernatants. This conclusion was based on monoclonal antibody neutralization studies and regression analyses in which the levels of alpha toxin, beta toxin, perfringolysin O, and beta2 toxin production were compared with lethality. Collectively, our results highlight the importance of beta toxin for type C-induced toxemia.
The GTPase Rab4 Interacts withChlamydia trachomatisInclusion Membrane Protein CT229
Authors: Rzomp K. A. , Moorhead A. R. , Scidmore M. A. 
Published: August 2006

ABSTRACTChlamydiae, which are obligate intracellular bacteria, replicate in a nonlysosomal vacuole, termed an inclusion. Although neither the host nor the chlamydial proteins that mediate the intracellular trafficking of the inclusion have been clearly identified, several enhanced green fluorescent protein (GFP)-tagged Rab GTPases, including Rab4A, are recruited to chlamydial inclusions. GFP-Rab4A associates with inclusions in a species-independent fashion by 2 h postinfection by mechanisms that have not yet been elucidated. To test whether chlamydial inclusion membrane proteins (Incs) recruit Rab4 to the inclusion, we screened a collection of chlamydial Incs for their ability to interact with Rab4A by using a yeast two-hybrid assay. From our analysis, we identified a specific interaction between Rab4A andChlamydia trachomatisInc CT229, which is expressed during the initial stages of infection. CT229 interacts with only wild-type Rab4A and the constitutively active GTPase-deficient Rab4AQ67L but not with the dominant-negative GDP-restricted Rab4AS22N mutant. To confirm the interaction between CT229 and Rab4A, we demonstrated that DsRed-CT229 colocalized with GFP-Rab4A in HeLa cells and more importantly wild-type and constitutively active GFP-Rab4A colocalized with CT229 at the inclusion membrane inC. trachomatisserovar L2-infected HeLa cells. Taken together, these data suggest that CT229 interacts with and recruits Rab4A to the inclusion membrane and therefore may play a role in regulating the intracellular trafficking or fusogenicity of the chlamydial inclusion.
The Contribution of PspC to Pneumococcal Virulence Varies between Strains and Is Accomplished by Both Complement Evasion and Complement-Independent Mechanisms
Authors: Kerr Alison R. , Paterson Gavin K. , McCluskey Jackie , Iannelli Francesco , Oggioni Marco R. , Pozzi Gianni , Mitchell Tim J. 
Published: August 2006

ABSTRACT

Pneumococcal surface protein C (PspC) is a virulence factor of
Streptococcus pneumoniae
previously shown to play a role in bacterial adherence, invasion, and evasion of complement. We investigated the role of this protein in our murine models of pneumococcal pneumonia with different pneumococcal strains. The deletion of
pspC
in strains of serotypes 2, 3, and 19F did not significantly alter host survival times in the pneumonia model. In contrast,
pspC
deletion significantly reduced the virulence of the serotype 4 strain, TIGR4, in both the pneumonia and bacteremia models. Therefore,
pspC
is a systemic and pulmonary virulence determinant for
S. pneumoniae
, but its effects are influenced by the pneumococcal strain. Finally, pneumonia infection of complement-deficient (C3
−/−
) mice enhanced
pspC
virulence, illustrating that PspC-mediated complement evasion contributes to virulence. However, other functions of PspC also contribute to virulence, as demonstrated by the finding that the
pspC
-deficient TIGR4 mutant was still attenuated relative to the wild-type parent, even in the absence of C3.
Extensive Genomic Plasticity in
Pseudomonas aeruginosa
Revealed by Identification and Distribution Studies of Novel Genes among Clinical Isolates
Authors: Shen Kai , Sayeed Sameera , Antalis Patricia , Gladitz John , Ahmed Azad , Dice Bethany , Janto Benjamin , Dopico Richard , Keefe Randy , Hayes Jay , Johnson Sandra , Yu Sujun , Ehrlich Nathan , Jocz Jennifer , Kropp Laura , Wong Ray , Wadowsky Robert M. , Slifkin Malcolm , Preston Robert A. , Erdos Geza , Post J. Christopher , Ehrlich Garth D. , Hu Fen Z. 
Published: August 2006

ABSTRACT

The distributed genome hypothesis (DGH) states that each strain within a bacterial species receives a unique distribution of genes from a population-based supragenome that is many times larger than the genome of any given strain. The observations that natural infecting populations are often polyclonal and that most chronic bacterial pathogens have highly developed mechanisms for horizontal gene transfer suggested the DGH and provided the means and the mechanisms to explain how chronic infections persist in the face of a mammalian host's adaptive defense mechanisms. Having previously established the validity of the DGH for obligate pathogens, we wished to evaluate its applicability to an opportunistic bacterial pathogen. This was accomplished by construction and analysis of a highly redundant pooled genomic library containing approximately 216,000 functional clones that was constructed from 12 low-passage clinical isolates of
Pseudomonas aeruginosa
, 6 otorrheic isolates and 6 from other body sites. Sequence analysis of 3,214 randomly picked clones (mean insert size, ∼1.4 kb) from this library demonstrated that 348 (10.8%) of the clones were unique with respect to all genomic sequences of the
P. aeruginosa
prototype strain, PAO1. Hypothetical translations of the open reading frames within these unique sequences demonstrated protein homologies to a number of bacterial virulence factors and other proteins not previously identified in
P. aeruginosa
. PCR and reverse transcription-PCR-based assays were performed to analyze the distribution and expression patterns of a 70-open reading frame subset of these sequences among 11 of the clinical strains. These sequences were unevenly distributed among the clinical isolates, with nearly half (34/70) of the novel sequences being present in only one or two of the individual strains. Expression profiling revealed that a vast majority of these sequences are expressed, strongly suggesting they encode functional proteins.
AttenuatedFrancisella novicidaTransposon Mutants Protect Mice against Wild-Type Challenge
Authors: Tempel Rebecca , Lai Xin-He , Crosa Lidia , Kozlowicz Briana , Heffron Fred 
Published: August 2006

ABSTRACTFrancisella tularensisis the bacterial pathogen that causes tularemia in humans and a number of animals. To date, there is no approved vaccine for this widespread and life-threatening disease. The goal of this study was to identifyF. tularensismutants that can be used in the development of a live attenuated vaccine. We screenedF. novicidatransposon mutants to identify mutants that exhibited reduced growth in mouse macrophages, as these cells are the preferred host cells ofFrancisellaand an essential component of the innate immune system. This approach yielded 16F. novicidamutants that were 100-fold more attenuated for virulence in a mouse model than the wild-type parental strain. These mutants were then tested to determine their abilities to protect mice against challenge with high doses of wild-type bacteria. Five of the 16 attenuated mutants (with mutations corresponding todsbB, FTT0742,pdpB,fumA, andcarBin theF. tularensisSCHU S4 strain) provided mice with protection against challenge with high doses (>8 × 105CFU) of wild-typeF. novicida. We believe that these findings will be of use in the design of a vaccine against tularemia.