bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carbohydrate Biopolymers Enhance Antibody Responses to Mucosally Delivered Vaccine Antigens
Authors: Bacon A. , Makin J. , Sizer P. J. , Jabbal-Gill I. , Hinchcliffe M. , Illum L. , Chatfield S. , Roberts M. 
Published: July 2002

ABSTRACTWe have evaluated the ability of two carbohydrate biopolymers, chitosan and gellan, to enhance antibody responses to subunit influenza virus vaccines delivered to the respiratory tracts of mice. Groups of mice were vaccinated three times intranasally (i.n.) with 10 μg of purified influenza B/Panama virus surface antigens (PSAs), which consist of hemagglutinin (HA) and neuraminidase (NA), either alone or admixed with chitosan or gellan solutions. Separate groups were vaccinated subcutaneously (s.c.) with PSAs adsorbed to Alhydrogel or chitosan or gellan alone i.n. Serum antibody responses were determined by enzyme-linked immunosorbent assay (ELISA) for influenza virus-specific immunoglobulin G (IgG) and by HA inhibition (HAI) and NA inhibition (NAI) assays. The local respiratory immune response was measured by assaying for influenza virus-specific IgA antibody in nasal secretions and by enumerating nasal and pulmonary lymphocytes secreting IgA, IgG, and IgM anti-influenza virus-specific antibodies by enzyme-linked immunospotting (ELISPOT). When administered alone i.n., B/Panama PSA was poorly immunogenic. Parenteral immunization with B/Panama PSA with Alhydrogel elicited high titers of anti-B/Panama antibodies in serum but a very poor respiratory anti-B/Panama IgA response. In contrast, i.n. immunization with PSA plus chitosan stimulated very strong local and systemic anti-B/Panama responses. Gellan also enhanced the local and serum antibody responses to i.n. PSA but not to the same extent as chitosan. The ability of chitosan to augment the immunogenicity of influenza vaccines given i.n. was confirmed using PSA prepared from an influenza A virus (A/Texas H1N1).
Regulation of
Salmonella enterica
Serovar Typhimurium Invasion Genes by
csrA
Authors: Altier Craig , Suyemoto Mitsu , Lawhon Sara D. 
Published: July 2002

ABSTRACT

Penetration of intestinal epithelial cells by
Salmonella enterica
serovar Typhimurium requires the expression of invasion genes, found in
Salmonella
pathogenicity island 1 (SPI1), that encode components of a type III secretion apparatus. These genes are controlled in a complex manner by regulators within SPI1, including HilA and InvF, and those outside SPI1, such as the two-component regulators PhoP/PhoQ and BarA/SirA. We report here that epithelial cell invasion requires the serovar Typhimurium homologue of
Escherichia coli csrA
, which encodes a regulator that alters the stability of specific mRNA targets. A deletion mutant of
csrA
was unable to efficiently invade cultured epithelial cells and showed reduced expression of four tested SPI1 genes,
hilA, invF, sipC
, and
prgH
. Overexpression of
csrA
from an induced
araBAD
promoter also negatively affected the expression of these genes, indicating that CsrA can act as both a positive and a negative regulator of SPI1 genes and suggesting that the bacterium must tightly control the level or activity of CsrA to achieve maximal invasion. We found that CsrA affected
hilA
, a regulator of the other three genes we tested, probably by controlling one or more genetic elements that regulate
hilA
. We also found that both the loss and the overexpression of
csrA
reduced the expression of two regulators of
hilA, hilC
and
hilD
, suggesting that
csrA
exerts its control of
hilA
through one or both of these regulators. We further found, however, that CsrA could affect the expression of both
invF
and
sipC
independent of its effects on
hilA
. One additional striking phenotype of the
csrA
mutant, not observed in a comparable
E. coli
mutant, was its slow growth. Phenotypic revertants that had normal growth rates, while maintaining the
csrA
mutation, were common. These suppressed strains, however, did not recover the ability to invade cultured cells, indicating that the
csrA
-mediated loss of invasion cannot be attributed simply to poor growth and that the growth and invasion deficits of the
csrA
mutant arise from effects of CsrA on different targets.
Role of Listeriolysin O in Cell-to-Cell Spread of
Listeria monocytogenes
Authors: Gedde Margaret M. , Higgins Darren E. , Tilney Lewis G. , Portnoy Daniel A. 
Published: July 2002

ABSTRACT

Listeria monocytogenes
is a facultative intracellular bacterial pathogen that escapes from a host vacuolar compartment and grows rapidly in the cytosol. Listeriolysin O (LLO) is a secreted pore-forming protein essential for the escape of
L. monocytogenes
from the vacuole formed upon initial internalization. However, its role in intracellular growth and cell-to-cell spread events has not been testable by a genetic approach. In this study, purified six-His-tagged LLO (HisLLO) was noncovalently coupled to the surface of nickel-treated LLO-negative mutants. Bound LLO mediated vacuolar escape in approximately 2% of the mutants. After 5.5 h of growth, cytosolic bacteria were indistinguishable from wild-type bacteria with regard to formation of pseudopod-like extensions, here termed listeriopods, and spread to adjacent cells. However, bacteria in adjacent cells failed to multiply and were found in double-membrane vacuoles. Addition of bound LLO to mutants lacking LLO and two distinct phospholipases C (PLCs) also resulted in spread to adjacent cells, but these triple mutants became trapped in multiple-membrane vacuoles that are reminiscent of autophagocytic vacuoles. These studies show that neither LLO nor the PLCs are necessary for listeriopod formation and uptake of bacteria into neighboring cells but that LLO is required for the escape of
L. monocytogenes
from the double-membrane vacuole that forms upon cell-to-cell spread.
Chlamydial Development Is Adversely Affected by Minor Changes in Amino Acid Supply, Blood Plasma Amino Acid Levels, and Glucose Deprivation
Authors: Harper Angela , Pogson Christopher I. , Jones Meirion L. , Pearce John H. 
Published: July 2002

ABSTRACT

This study has demonstrated the extreme sensitivity of
Chlamydia trachomatis
growing in McCoy cells to small changes in external amino acid supply. In the absence of cycloheximide, a decrease in the amino acid concentration of medium to 75% of control values was sufficient to induce the growth of enlarged chlamydial forms of reduced infectivity. Morphology became more distorted and the yield of infectious particles from inclusions declined as medium amino acid levels were further reduced. These events correlated with a general decline in intracellular amino acids, as measured by high-performance liquid chromatography, suggesting that chlamydiae require a minimum concentration of each amino acid for normal development. Cycloheximide enhanced the production of normal organisms and increased infectivity yield in media, suggesting that the drug increased the available pool of amino acids. This was supported by intracellular amino acid analyses. Aberrant forms with reduced infectivity were also induced during supply of infected cell cultures with medium containing blood plasma amino acid concentrations, supporting the proposal that nutrient levels in vivo could promote abnormal chlamydial development. Markedly abnormal forms were also observed during glucose deprivation, providing further evidence that aberrant development is a general stress-related response.
Cellular Changes and Apoptosis in the Spleens and Peripheral Blood of Mice Infected with Blood-StagePlasmodium chabaudi chabaudiAS
Authors: Helmby Helena , Jönsson Gun , Troye-Blomberg Marita 
Published: July 2002

ABSTRACTInfection with blood-stagePlasmodium chabaudi chabaudiAS results in splenomegaly, peripheral leukocytosis, and a major activation of the immune system. The frequencies and absolute numbers of T-cell, B-cell, and macrophage populations in spleen and peripheral blood fromP. chabaudi-infected BALB/c mice were compared and found to be significantly altered during acute infection. The kinetics of the redistribution of the different cell types in spleen and peripheral blood were different, with T and B cells appearing in the blood when their frequencies and absolute numbers in the spleen were low. The frequency and absolute number of apoptotic cells in the spleen were increased during acuteP. chabaudiinfection and involved both T cells, B cells, and macrophages. Both Fas and Fas-ligand expression were increased in the spleen. Taken together, our data provide new information on the complex cellular interactions that take place in the immune system during blood-stage malaria infection in a mouse model.
Role of Adhesins and Toxins in Invasion of Human Tracheal Epithelial Cells by
Bordetella pertussis
Authors: Bassinet Laurence , Gueirard Pascale , Maitre Bernard , Housset Bruno , Gounon Pierre , Guiso Nicole 
Published: July 2002

ABSTRACT

Bordetella pertussis
, the agent of whooping cough, can invade and survive in several types of eukaryotic cell, including CHO, HeLa 229, and HEp-2 cells and macrophages. In this study, we analyzed bacterial invasiveness in nonrespiratory human HeLa epithelial cells and human HTE and HAE0 tracheal epithelial cells. Invasion assays and transmission electron microscopy analysis showed that
B. pertussis
strains invaded and survived, without multiplying, in HTE or HAE0 cells. This phenomenon was
bvg
regulated, but invasive properties differed between
B. pertussis
strains and isolates and the
B. pertussis
reference strain. Studies with
B. pertussis
mutant strains demonstrated that filamentous hemagglutinin, the major adhesin, was involved in the invasion of human tracheal epithelial cells by bacteria but not in that of HeLa cells. Fimbriae and pertussis toxin were not found to be involved. However, we found that the production of adenylate cyclase-hemolysin prevents the invasion of HeLa and HTE cells by
B. pertussis
because an adenylate cyclase-hemolysin-deficient mutant was found to be more invasive than the parental strain. The effect of adenylate cyclase-hemolysin was mediated by an increase in the cyclic AMP concentration in the cells. Pertactin (PRN), an adhesin, significantly inhibited the invasion of HTE cells by bacteria, probably via its interaction with adenylate cyclase-hemolysin. Isolates producing different PRNs were taken up similarly, indicating that the differences in the sequences of the PRNs produced by these isolates do not affect invasion. We concluded that filamentous hemagglutinin production favored invasion of human tracheal cells but that adenylate cyclase-hemolysin and PRN production significantly inhibited this process.
Effect ofChlamydia trachomatisInfection and Subsequent Tumor Necrosis Factor Alpha Secretion on Apoptosis in the Murine Genital Tract
Authors: Perfettini Jean-Luc , Darville Toni , Gachelin Gabriel , Souque Philippe , Huerre Michel , Dautry-Varsat Alice , Ojcius David M. 
Published: July 2002

ABSTRACTThe pathology observed duringChlamydiainfection is due initially to localized tissue damage caused by the infection itself, followed by deleterious host inflammatory responses that lead to permanent scarring. We have recently reported that the infection byChlamydiain vitro results in apoptosis of epithelial cells and macrophages and that infected monocytes secrete the proinflammatory cytokine interleukin-1β. At the same time, proinflammatory cytokines such as tumor necrosis factor alpha (TNF-α) can also trigger apoptosis of susceptible cells. To study the possible relationship betweenChlamydia trachomatisinfection and apoptosis in vivo, we used the terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling technique to determine whether infection may cause apoptosis in the genital tract of mice and, conversely, whether cytokines produced during the inflammatory response may modulate the level of apoptosis. Our results demonstrate that infected cells in the endocervix at day 2 or 7 after infection are sometimes apoptotic, although there was not a statistically significant change in the number of apoptotic cells in the endocervix. However, large clumps of apoptotic infected cells were observed in the lumen, suggesting that apoptotic cells may be shed from the endocervix. Moreover, there was a large increase in the number of apoptotic cells in the uterine horns and oviducts after 2 or 7 days of infection, which was accompanied by obvious signs of upper tract pathology. Interestingly, depletion of TNF-α led to a decrease in the level of apoptosis in the uterine horns and oviducts of animals infected for 7 days, suggesting that the inflammatory cytokines may exert part of their pathological effect via apoptosis in infected tissues.
Purification, Characterization, and Molecular Analysis of the Gene Encoding Glucosyltransferase from
Streptococcus oralis
Authors: Fujiwara Taku , Hoshino Tomonori , Ooshima Takashi , Sobue Shizuo , Hamada Shigeyuki 
Published: July 2002

ABSTRACT

Streptococcus oralis
is a member of the oral streptococcal family and an early-colonizing microorganism in the oral cavity of humans.
S. oralis
is known to produce glucosyltransferase (GTase), which synthesizes glucans from sucrose. The enzyme was purified chromatographically from a culture supernatant of
S. oralis
ATCC 10557. The purified enzyme, GTase-R, had a molecular mass of 173 kDa and a pI of 6.3. This enzyme mainly synthesized water-soluble glucans with no primer dependency. The addition of GTase markedly enhanced the sucrose-dependent resting cell adhesion of
Streptococcus mutans
at a level similar to that found in growing cells of
S. mutans
. The antibody against GTase-R inhibited the glucan-synthesizing activities of
Streptococcus gordonii
and
Streptococcus sanguis
, as well as
S. oralis
. The N-terminal amino acid sequence of GTase-R exhibited no similarities to known GTase sequences of oral streptococci. Using degenerate PCR primers, an 8.1-kb DNA fragment, carrying the gene (
gtfR
) coding for GTase-R and its regulator gene (
rgg
), was cloned and sequenced. Comparison of the deduced amino acid sequence revealed that the
rgg
genes of
S. oralis
and
S. gordonii
exhibited a close similarity. The
gtfR
gene was found to possess a species-specific nucleotide sequence corresponding to the N-terminal 130 amino acid residues. Insertion of
erm
or
aphA
into the
rgg
or
gtfR
gene resulted in decreased GTase activity by the organism and changed the colony morphology of these transformants. These results indicate that
S. oralis
GTase may play an important role in the subsequent colonizing of mutans streptoccoci.
Cytophilic Immunoglobulin Responses toPlasmodium falciparumGlutamate-Rich Protein Are Correlated with Protection against Clinical Malaria in Dielmo, Senegal
Authors: Oeuvray Claude , Theisen Michael , Rogier Christophe , Trape Jean-Francois , Jepsen Søren , Druilhe Pierre 
Published: July 2002

ABSTRACTThe goal of this study was to analyze antibody responses toPlasmodium falciparumglutamate-rich protein (GLURP) using clinical data and plasma samples obtained from villagers of Dielmo, Senegal. This molecule was chosen because it is targeted by human antibodies which induce parasite growth inhibition in antibody-dependent cellular inhibition (ADCI) assays. The results showed a strong correlation between protection against malaria attacks and levels of immunoglobulin G2 (IgG2) and IgG3 against GLURP94–489(R0) and IgG3 against GLURP705–1178(R2) when corrected for the confounding effect of age-related exposure to malaria. Thus, GLURP may play a role in the induction of protective immunity againstP. falciparummalaria.
Pyrogenic Toxin Superantigen Site Specificity in Toxic Shock Syndrome and Food Poisoning in Animals
Authors: Schlievert Patrick M. , Jablonski Lynn M. , Roggiani Manuela , Sadler Ingrid , Callantine Scott , Mitchell David T. , Ohlendorf Douglas H. , Bohach Gregory A. 
Published: July 2002

ABSTRACTStaphylococcus aureusandStreptococcus pyogenesexpress pyrogenic toxin superantigens (PTSAgs) that are associated with toxic shock syndrome (TSS) and staphylococcal food poisoning (SFP). Most PTSAgs cause TSS in deep-tissue infections, whereas only TSS toxin 1 (TSST-1) is associated with menstrual, vaginal TSS. In contrast, SFP has been linked only with staphylococcal enterotoxins (SEs). Because of the differential abilities of PTSAgs to cause systemic or localized symptoms in a site-dependent manner, the present study was undertaken to assess the toxins' abilities to cross mucosal barriers. The activity of three PTSAgs when delivered orally, vaginally, or intravenously to rabbits and orally to monkeys was investigated. TSST-1 induced shock via all three routes in rabbits. Although active when administered intravenously, SEC1 and streptococcal pyrogenic exotoxin A (SPEA) did not cause symptoms when administered orally or vaginally. Only SEC1 induced emesis in the monkey feeding assay. TSST-1, albeit less stable than SEC1 and SPEA to pepsin, induced diarrhea in monkeys. Our results may explain the unique association of TSST-1 with menstrual TSS and why SPEA is only rarely associated with TSS after pharyngitis, despite being highly associated with TSS after subcutaneous infections. Finally, our studies indicate that enterotoxicity in SFP is not the result of superantigenicity.
Constitutive Mutations of the
Salmonella enterica
Serovar Typhimurium Transcriptional Virulence Regulator
phoP
Authors: Gunn John S. , Ernst Robert K. , McCoy Andrea J. , Miller Samuel I. 
Published: July 2002

ABSTRACT

The PhoP-PhoQ two-component system is necessary for the virulence of
Salmonella
spp. and is responsible for regulating several modifications of the lipopolysaccharide (LPS). Mutagenesis of the transcriptional regulator
phoP
resulted in the identification of a mutant able to activate transcription of regulated genes ∼100-fold in the absence of PhoQ. Sequence analysis showed two single-base alterations resulting in amino acid changes at positions 93 (S93N) and 203 (Q203R). These mutations were individually created, and although each resulted in a constitutive phenotype, the double mutant displayed a synergistic effect both in the induction of PhoP-activated gene expression and in resistance to antimicrobial peptides. The constitutive
phoP
gene was placed under the control of an arabinose-inducible promoter to examine the kinetics of PhoP-activated gene induction and the resultant modifications of LPS. Gene induction and 2-hydroxymyristate modification of the lipid A were shown to occur within minutes of the addition of arabinose and to peak at 4 h. As the first constitutive mutant of
phoP
identified, this allele will be invaluable to future genetic and biochemical studies of this and likely other regulatory systems.
Natural History of
Streptococcus sanguinis
in the Oral Cavity of Infants: Evidence for a Discrete Window of Infectivity
Authors: Caufield Page W. , Dasanayake Ananda P. , Li Yihong , Pan Yaping , Hsu Jay , Hardin J. Michael 
Published: July 2002

ABSTRACT

The heterogeneous group of oral bacteria within the sanguinis (sanguis) streptococci comprise members of the indigenous biota of the human oral cavity. While the association of
Streptococcus sanguinis
with bacterial endocarditis is well described in the literature,
S. sanguinis
is thought to play a benign, if not a beneficial, role in the oral cavity. Little is known, however, about the natural history of
S. sanguinis
and its specific relationship with other oral bacteria. As part of a longitudinal study concerning the transmission and acquisition of oral bacteria within mother-infant pairs, we examined the initial acquisition of
S. sanguinis
and described its colonization relative to tooth emergence and its proportions in plaque and saliva as a function of other biological events, including subsequent colonization with mutans streptococci. A second cohort of infants was recruited to define the taxonomic affiliation of
S. sanguinis
. We found that the colonization of the
S. sanguinis
occurs during a discrete “window of infectivity” at a median age of 9 months in the infants. Its colonization is tooth dependent and correlated to the time of tooth emergence; its proportions in saliva increase as new teeth emerge. In addition, early colonization of
S. sanguinis
and its elevated levels in the oral cavity were correlated to a significant delay in the colonization of mutans streptococci. Underpinning this apparent antagonism between
S. sanguinis
and mutans streptococci is the observation that after mutans streptococci colonize the infant, the levels of
S. sanguinis
decrease. Children who do not harbor detectable levels of mutans streptococci have significantly higher levels of
S. sanguinis
in their saliva than do children colonized with mutans streptococci. Collectively, these findings suggest that the colonization of
S. sanguinis
may influence the subsequent colonization of mutans streptococci, and this in turn may suggest several ecological approaches toward controlling dental caries.
High Intracellular Level of Guanosine Tetraphosphate in
Mycobacterium smegmatis
Changes the Morphology of the Bacterium
Authors: Ojha Anil K. , Mukherjee Tapan K. , Chatterji Dipankar 
Published: July 2002

ABSTRACT

Almost one-third of the world population today harbors the tubercle bacillus asymptomatically. It is postulated that the morphology and staining pattern of the long-term persistors are different from those of actively growing culture. Interestingly, it has been found that the morphology and staining pattern of the starved in vitro population of mycobacteria is similar to the persistors obtained from the lung lesions. In order to delineate the biochemical characteristics of starved mycobacteria,
Mycobacteria smegmatis
was grown in 0.2% glucose as a sole carbon source along with an enriched culture in 2% glucose. Accumulation of the stringent factor guanosine tetraphosphate (ppGpp) with a concomitant change in morphology was observed for
M. smegmatis
under carbon-deprived conditions. In addition,
M. smegmatis
assumed a coccoid morphology when ppGpp was ectopically produced by overexpressing
Escherichia coli relA
, even in an enriched medium. The
Mycobacterium tuberculosis relA
and
spoT
homologue, when induced in
M. smegmatis
, also resulted in the overproduction of ppGpp with a change in the bacterium's growth characteristics.
CD4+Cells Are Indispensable for Ulcer Development in Murine Cutaneous Leishmaniasis
Authors: Terabe Masaki , Kuramochi Takashi , Ito Mamoru , Hatabu Toshimitsu , Sanjoba Chizu , Chang Kwang-Poo , Onodera Takashi , Matsumoto Yoshitsugu 
Published: July 2002

ABSTRACTOne of the most characteristic clinical features in cutaneous leishmaniasis is the development of nodules followed by ulcerations at the site of infection.Leishmania amazonensis-infected mice show similar ulcerative lesions.Leishmania-infected severe combined immunodeficiency (SCID) mice, however, have been shown to develop nonulcerative nodules. In the present study, the roles of T cells in ulceration were examined using SCID mice in cell reconstitution experiments. After development of nonulcerative nodules, SCID mice were inoculated with splenocytes from eitherLeishmania-infected or naive immunocompetent mice, resulting in ulceration in all mice. When naive splenocytes were depleted of CD4+, CD8+, or B220+cell populations and the remaining cells were injected intoLeishmania-infected SCID mice after the development of nodules, only SCID mice inoculated with splenocytes depleted of CD4+cells did not show ulceration. The evidence obtained in this study clearly shows that the CD4+cell population is indispensable for ulceration in leishmaniasis lesions of SCID mice.