bluuebunny/crossref_metadata_2025_split huggingface dataset:
Haemophilus ducreyiInfection Causes Basal Keratinocyte Cytotoxicity and Elicits a Unique Cytokine Induction Pattern in an In Vitro Human Skin Model
Authors: Hobbs Marcia M. , Paul Terry R. , Wyrick Priscilla B. , Kawula Thomas H. 
Published: December 2019

ABSTRACTHaemophilus ducreyiis the etiologic agent of the sexually transmitted genital ulcer disease chancroid. Predominantly a cutaneous pathogen,H. ducreyiis present in chancroid ulcers that are characterized by extensive neutrophil accumulation in intraepidermal lesions accompanied by a mononuclear infiltrate in the dermis. We used an in vitro human skin model composed of foreskin fibroblasts and keratinocytes to examine host skin cell interactions withH. ducreyi35000. Bacteria replicated and persisted in artificial skin for at least 14 days. We observedH. ducreyiinside suprabasal keratinocytes using transmission electron microscopy. Although no bacteria were seen in the basal keratinocyte region, these cells were disrupted in infected cocultures.H. ducreyiinfection stimulated increased secretion of interleukin-6 (IL-6) and IL-8 by skin cells. Conversely, tumor necrosis factor alpha and IL-1α levels were not elevated. IL-8 produced in response toH. ducreyiinfection may be involved in recruiting polymorphonuclear leukocytes and other inflammatory cells, thereby contributing to the tissue necrosis and ulcer formation characteristic of chancroid.
Evaluation of New Vaccines in the Mouse and Guinea Pig Model of Tuberculosis
Authors: Baldwin Susan L. , D’Souza Celine , Roberts Alan D. , Kelly Brian P. , Frank Anthony A. , Lui Margaret A. , Ulmer Jeffrey B. , Huygen Kris , McMurray David M. , Orme Ian M. 
Published: December 2019

ABSTRACTThe results of this study provide the first evidence that two completely separate vaccine approaches, one based on a subunit vaccine consisting of a mild adjuvant admixed with purified culture filtrate proteins and enhanced by the cytokine interleukin-2 and the second based on immunization with DNA encoding the Ag85A protein secreted byMycobacterium tuberculosis, could both prevent the onset of caseating disease, which is the hallmark of the guinea pig aerogenic infection model. In both cases, however, the survival of vaccinated guinea pigs was shorter than that conferred byMycobacterium bovisBCG, with observed mortality of these animals probably due to consolidation of lung tissues by lymphocytic granulomas. An additional characteristic of these approaches was that neither induced skin test reactivity to commercial tuberculin. These data thus provide optimism that development of nonliving vaccines which can generate long-lived immunity approaching that conferred by the BCG vaccine is a feasible goal.
LcrG is Required for Efficient Translocation of
Yersinia
Yop Effector Proteins into Eukaryotic Cells
Authors: Sarker Mahfuzur R. , Sory Marie-Paule , Boyd Aoife P. , Iriarte Maite , Cornelis Guy R. 
Published: December 2019

ABSTRACT

Extracellular
Yersinia
disables the immune system of its host by injecting effector Yop proteins into host cells. We show that a
Yersinia enterocolitica
nonpolar
lcrG
mutant is severely impaired in the translocation of YopE, YopH, YopM, YpkA/YopO, and YopP into eukaryotic cells. LcrG is thus required for efficient internalization of all the known Yop effectors.
Entamoeba histolyticaInduces Host Cell Death in Amebic Liver Abscess by a Non-Fas-Dependent, Non-Tumor Necrosis Factor Alpha-Dependent Pathway of Apoptosis
Authors: Seydel Karl B. , Stanley Samuel L. 
Published: December 2019

ABSTRACTAmebic liver abscess is characterized by extensive areas of dead hepatocytes that form cavities surrounded by a thin rim of inflammatory cells and fewEntamoeba histolyticatrophozoites.E. histolyticaproduces pore-forming proteins and proteinases, but how trophozoites actually kill host cells has been unclear. Here, we report thatE. histolyticainduces apoptosis in both inflammatory cells and hepatocytes in a severe combined immunodeficient (SCID) mouse model of amebic liver abscess. By studying infection in C57/BL6.lpr and C57/BL6.gld mice, we found thatE. histolytica-induced apoptosis does not require the Fas/Fas ligand pathway of apoptosis, and by using mice with a targeted deletion of the tumor necrosis factor receptor I gene, we have shown thatE. histolytica-induced apoptosis is not mediated by tumor necrosis factor alpha. Our data indicate that apoptosis plays a prominent role in the host cell death seen in amebic liver abscess in a mouse model of disease and suggest thatE. histolyticainduces cell death without using two common pathways for apoptosis.
Extracellular Release of Antigenic Proteins by
Helicobacter pylori
Authors: Cao Ping , McClain Mark S. , Forsyth Mark H. , Cover Timothy L. 
Published: December 2019

ABSTRACT

Screening a
Helicobacter pylori
genomic library with antisera raised against
H. pylori
broth culture supernatant resulted in the identification of six antigens: urease, HspB, Lpp20, DnaK, MsrA, and a cysteine-rich 28-kDa protein (designated HcpA).
H. pylori
antigens may be released into the extracellular space by multiple mechanisms, including specific secretion pathways, autolysis, and membrane vesicle formation.
Acute and Chronic Phases ofToxoplasma gondiiInfection in Mice Modulate the Host Immune Responses
Authors: Nguyen T. D. , Bigaignon G. , Van Broeck J. , Vercammen M. , Nguyen T. N. , Delmee M. , Turneer M. , Wolf S. F. , Coutelier J. P. 
Published: December 2019

ABSTRACTMurine antibody responses to soluble proteins are generally restricted to the immunoglobulin G1 (IgG1) isotype. When mice were infected withToxoplasma gondiiBeverley and concomitantly immunized with a soluble unrelated protein antigen, a modification in the isotypic distribution of antibodies directed against this nonparasite antigen was observed, with a preferential production of IgG2a. Interestingly, when mice were immunized with a soluble protein antigen during the chronic phase (day 40) of infection withT. gondiiBeverley, a similar modification in the isotypic distribution of antiprotein antibodies was observed.
Phase 1 Evaluation ofVibrio choleraeO1, Serotype Inaba, Polysaccharide-Cholera Toxin Conjugates in Adult Volunteers
Authors: Gupta Rajesh K. , Taylor David N. , Bryla Dolores A. , Robbins John B. , Szu Shousun C. 
Published: December 2019

ABSTRACTConjugate vaccines were prepared by binding hydrazine-treated lipopolysaccharide (DeALPS) fromVibrio choleraeO1, serotype Inaba, to cholera toxin (CT) variants CT-1 and CT-2. Volunteers (n= 75) were injected with either 25 μg of DeALPS, alone or as a conjugate, or the licensed cellular vaccine containing 4 × 109organisms each of serotypes Inaba and Ogawa per ml. No serious adverse reactions were observed. DeALPS alone did not elicit serum LPS or vibriocidal antibodies in mice and only low levels of immunoglobulin M (IgM) anti-LPS in the volunteers. Recipients of the cellular vaccine had the highest IgM anti-LPS levels, but the difference was not statistically significant from that elicited by the conjugates. The conjugates elicited the highest levels of IgG anti-LPS (DeALPS-CT-2 > DeALPS-CT-1 > cellular vaccine). Both conjugates and the cellular vaccine elicited vibriocidal antibodies: after 8 months, recipients of cellular vaccine had the highest geometric mean titer (1,249), followed by DeALPS-CT-2 (588) and DeALPS-CT-1 (330). The correlation coefficient between IgG anti-LPS and 2-mercaptoethanol (2-ME)-resistant vibriocidal antibodies was 0.81 (P= 0.0004). Convalescent sera from cholera patients had a mean vibriocidal titer of 2,525 that was removed by treatment with 2-ME. The vibriocidal activities of sera from all vaccine groups and from the patients were absorbed (>75%) by LPS but not by either CT-1 or CT-2. Conjugate-induced IgG vibriocidal antibodies persisted longer than those elicited by the whole-cell vaccine. Both conjugates, but not the cellular vaccine, elicited IgG anti-CT.
Purification of the
inlB
Gene Product of
Listeria monocytogenes
and Demonstration of Its Biological Activity
Authors: Müller Simone , Hain Torsten , Pashalidis Philippos , Lingnau Andreas , Domann Eugen , Chakraborty Trinad , Wehland Jürgen 
Published: December 2019

ABSTRACT

Entry of
Listeria monocytogenes
into nonphagocytic cells requires the
inlAB
gene products. InlA and InlB are bacterial cell wall-associated polypeptides that can be released by sodium dodecyl sulfate treatment. By applying more gentle extraction methods, we have purified InlB in its native form. Treatment of bacteria with various nondenaturating agents including mutanolysin, thiol reagents, sodium chloride, and detergents like Triton X-100 or 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate did not release substantial amounts of InlB from the bacterial cell wall. Instead, InlB was nearly quantitatively extracted in a solubilized form by treatment of bacteria with 1 M Tris-Cl or other protonated amines at pH 7.5. However, the reduced solubility of the extracted InlB in low-salt buffers hampered further biochemical purification. A panel of monoclonal antibodies against listerial Tris-Cl extracts containing InlB was therefore produced to generate reagents for use in affinity chromatography. One of the monoclonal antibodies enabled purification of the InlB protein to homogeneity with relatively high yields. When added externally, purified InlB associated with the surface of noninvasive bacteria such as
Listeria innocua
or an
L. monocytogenes inlB2
mutant, where it promoted entry of these strains into Vero cells >300- and 17-fold, respectively. This effect was even more dramatic for HeLa cells, where the observed invasion was increased about 9,000- and 4,000-fold, respectively. The availability of purified native, invasion-competent InlB will allow analysis of the molecular basis of InlB-mediated entry into tissue culture cell lines in greater detail.
Cloning and Characterization of an Outer Membrane Protein of
Vibrio vulnificus
Required for Heme Utilization: Regulation of Expression and Determination of the Gene Sequence
Authors: Litwin Christine M. , Byrne Burke L. 
Published: December 2019

ABSTRACT

Vibrio vulnificus
is a halophilic, marine pathogen that has been associated with septicemia and serious wound infections in patients with iron overload and preexisting liver disease. For
V. vulnificus
, the ability to acquire iron from the host has been shown to correlate with virulence.
V. vulnificus
is able to use host iron sources such as hemoglobin and heme. We previously constructed a
fur
mutant of
V. vulnificus
which constitutively expresses at least two iron-regulated outer membrane proteins, of 72 and 77 kDa. The N-terminal amino acid sequence of the 77-kDa protein purified from the
V. vulnificus fur
mutant had 67% homology with the first 15 amino acids of the mature protein of the
Vibrio cholerae
heme receptor, HutA. In this report, we describe the cloning, DNA sequence, mutagenesis, and analysis of transcriptional regulation of the structural gene for HupA, the heme receptor of
V. vulnificus
. DNA sequencing of
hupA
demonstrated a single open reading frame of 712 amino acids that was 50% identical and 66% similar to the sequence of
V. cholerae
HutA and similar to those of other TonB-dependent outer membrane receptors. Primer extension analysis localized one promoter for the
V. vulnificus hupA
gene. Analysis of the promoter region of
V. vulnificus hupA
showed a sequence homologous to the consensus Fur box. Northern blot analysis showed that the transcript was strongly regulated by iron. An internal deletion in the
V. vulnificus hupA
gene, done by using marker exchange, resulted in the loss of expression of the 77-kDa protein and the loss of the ability to use hemin or hemoglobin as a source of iron. The
hupA
deletion mutant of
V. vulnificus
will be helpful in future studies of the role of heme iron in
V. vulnificus
pathogenesis.
Chronic Active Hepatitis Induced byHelicobacter hepaticusin the A/JCr Mouse Is Associated with a Th1 Cell-Mediated Immune Response
Authors: Whary M. T. , Morgan T. J. , Dangler C. A. , Gaudes K. J. , Taylor N. S. , Fox J. G. 
Published: December 2019

ABSTRACTHelicobacter hepaticusinfection in A/JCr mice results in chronic active hepatitis characterized by perivascular, periportal, and parenchymal infiltrates of mononuclear and polymorphonuclear cells. This study examined the development of hepatitis and the immune response of A/JCr mice toH. hepaticusinfection. The humoral and cell-mediated T helper immune response was profiled by measuring the postinfection (p.i.) antibody response in serum, feces, and bile and by the production of cytokines and proliferative responses by splenic mononuclear cells toH. hepaticusantigens. Secretory immunoglobulin A (IgA) and systemic IgG2a antibody developed by 4 weeks p.i. and persisted through 12 months. Splenocytes from infected mice proliferated and produced more gamma interferon (IFN-γ) than interleukin-4 (IL-4) or IL-5 when cultured withH. hepaticusouter membrane proteins. The predominantly IgG2a antibody response in serum and the in vitro production of IFN-γ in excess of IL-4 or IL-5 are consistent with a Th1 immune response reported in humans and mice infected withHelicobacter pyloriandHelicobacter felis, respectively. Mice infected withH. hepaticusdeveloped progressively severe perivascular, periportal, and hepatic parenchymal lesions consisting of lymphohistiocytic and plasmacytic cellular infiltrates. In addition, transmural typhlitis was observed at 12 months p.i. The characterization of a cell-mediated Th1 immune response toH. hepaticusinfection in the A/JCr mouse should prove valuable as a model for experimental regimens which manipulate the host response toHelicobacter.
Pet, an Autotransporter Enterotoxin from Enteroaggregative
Escherichia coli
Authors: Eslava Carlos , Navarro-García Fernando , Czeczulin John R. , Henderson Ian R. , Cravioto Alejandro , Nataro James P. 
Published: December 2019

ABSTRACT

Enteroaggregative
Escherichia coli
(EAEC) is an emerging cause of diarrheal illness. Clinical data suggest that diarrhea caused by EAEC is predominantly secretory in nature, but the responsible enterotoxin has not been described. Work from our laboratories has implicated a ca. 108-kDa protein as a heat-labile enterotoxin and cytotoxin, as evidenced by rises in short-circuit current and falls in tissue resistance in rat jejunal tissue mounted in an Ussing chamber. Here we report the genetic cloning, sequencing, and characterization of this high-molecular-weight heat-labile toxin. The toxin (designated the plasmid-encoded toxin [Pet]) is encoded on the 65-MDa adherence-related plasmid of EAEC strain 042. Nucleotide sequence analysis suggests that the toxin is a member of the autotransporter class of proteins, characterized by the presence of a conserved C-terminal domain which forms a β-barrel pore in the bacterial outer membrane and through which the mature protein is transported. The Pet toxin is highly homologous to the EspP protease of enterohemorrhagic
E. coli
and to EspC of enteropathogenic
E. coli
, an as yet cryptic protein. In addition to its potential role in EAEC infection, Pet represents the first enterotoxin within the autotransporter class of secreted proteins. We hypothesize that other closely related members of this class may also produce enterotoxic effects.
Induction of Protective Immune Responses by Immunization with Linear Multiepitope Peptides Based on Conserved Sequences fromPlasmodium falciparumAntigens
Authors: Bharadwaj Ashima , Sharma Pawan , Joshi Sunil K. , Singh Balwan , Chauhan V. S. 
Published: December 2019

ABSTRACTA cysteine-containing peptide motif, EWSPCSVTCG, is found highly conserved in the circumsporozoite protein (CSP) and the thrombospondin-related anonymous protein (TRAP) of all thePlasmodiumspecies analyzed so far and has been shown to be crucially involved in the sporozoite invasion of hepatocytes. We have recently shown that peptide sequences containing this motif, and also the antibodies raised against the motif, inhibit the merozoite invasion of erythrocytes. However, during natural infection, and upon immunization with recombinant CSP, this motif represents a cryptic epitope. Here we present the results of immunization studies with two linear multiepitopic constructs, a 60-residue (P60) and a 32-residue (P32) peptide, containing the conserved motif sequence. Both the peptides per se generated high levels of specific antibodies in BALB/c mice. P32 was found to be genetically restricted toH-2dandH-2bhaplotypes of mice, whereas P60 was found to be immunogenic in five different strains of mice. The antibody response was predominantly targeted to the otherwise cryptic, conserved motif sequence in P60. Anti-P60 antibodies specifically stained the asexual blood stages ofPlasmodium falciparumandPlasmodium yoeliiin an immunofluorescence assay, recognized a 60- to 65-kDa parasite protein in an immunoblot assay, and blockedP. falciparummerozoite invasion of erythrocytes in a dose-dependent manner. Immunization with P60 also induced significant levels of the cytokines interleukin-2 (IL-2), IL-4, and gamma interferon in BALB/c mice. Moreover, >60% of mice immunized with P60 survived a heterologous challenge infection with a lethal strain ofP. yoelii. These results indicate that appropriate medium-sized synthetic peptides might prove useful in generating specific immune responses to an otherwise cryptic but critical and putatively protective epitope in an antigen and could form part of a multicomponent malaria vaccine.
In Vitro Cellular Toxicity Predicts
Pseudomonas aeruginosa
Virulence in Lung Infections
Authors: Sawa Teiji , Ohara Maria , Kurahashi Kiyoyasu , Twining Sally S. , Frank Dara W. , Doroques David B. , Long Taicy , Gropper Michael A. , Wiener-Kronish Jeanine P. 
Published: December 2019

ABSTRACT

The role of quorum sensing by
Pseudomonas aeruginosa
in producing cytotoxicity has not been fully investigated. Strains of
P. aeruginosa
have been characterized as having an invasive or a cytotoxic phenotype (S. M. J. Fleiszig et al., Infect. Immun. 65:579–586, 1997). We noted that the application of a large inoculum of the invasive strain 6294 caused cytotoxicity of cultured epithelial cells. To investigate this dose-related cytotoxicity, we compared the behavior of 6294 to that of another invasive strain, PAO1, and determined whether the cytotoxicity could be related to quorum sensing. Both invasive strains, 6294 and PAO1, appear to have quorum-sensing systems that were operative when large doses of bacteria were applied to cultured lung epithelial cells or instilled into the lungs of animals. Nonetheless, only 6294 was cytotoxic. Cytotoxicity induced by 6294 correlated with increased elastase production. These experiments suggest that there are multiple mechanisms for the induction of cytotoxicity, pathology, and mortality in vivo. However, in vivo cytotoxicity and mortality, but not pathology, could be predicted by quantitative in vitro cellular damage experiments utilizing a range of bacteria-to-cell ratios. It appears that quorum sensing may inversely correlate with virulence in that strains that produced PAI [
N
-(3-oxododecanoyl) homoserine lactone] also appeared to attract more polymorphonuclear leukocytes in vivo and were possibly eliminated more quickly. In addition, exoproduct production in bacteriological medium in vitro may differ significantly from exoproduct expression from infections in vivo or during cocultivation of bacteria with tissue culture cells.
Bradyzoite Development in
Toxoplasma gondii
and the hsp70 Stress Response
Authors: Weiss Louis M. , Ma Yan Fen , Takvorian Peter M. , Tanowitz Herbert B. , Wittner Murray 
Published: December 2019

ABSTRACT

Toxoplasma gondii
is a well-described ubiquitous Apicomplexan protozoan parasite that is an important opportunistic pathogen. The factors affecting the transition of tachyzoites to the latent bradyzoite stage remain to be defined. The induction of bradyzoite development in vitro has been linked to temperature, pH, mitochondrial inhibitors, sodium arsenite, and many of the other stressors associated with heat shock protein (hsp) induction. There is evidence for other organisms that hsps are developmentally regulated. Therefore, we examined whether hsp induction is an early event in bradyzoite differentiation. Extracellular and intracellular
T. gondii
cells, after exposure to pH 8.1 or 7.1, were analyzed for the expression of inducible hsp70 by using monoclonal antibody C92F3A-5 (specific to hsp70). Western blotting demonstrated that a 72-kDa protein reactive with C92F3A-5 (hsp70), which we believe is part of the hsp70 family, is induced during bradyzoite development. By immunofluorescence and immunoelectron microscopy, we were able to demonstrate that hsp70 staining colocalized to
T. gondii
expressing bradyzoite-specific antigens and the presence of hsp70 in bradyzoites isolated from mouse brain. Quercetin, a bioflavonoid which inhibits the synthesis of hsp90, hsp70, and hsp27, suppresses the induction of bradyzoite development in vitro. Reverse transcription-PCR with conserved hsp70 primers demonstrated an increase in hsp70 in
T. gondii
on exposure to conditions which induce bradyzoite formation. A
T. gondii
hsp70 was subsequently cloned and sequenced by using this amplified fragment. We believe our evidence suggests that hsps are important in the process of bradyzoite differentiation.
Identification of Three Highly Attenuated
Salmonella typhimurium
Mutants That Are More Immunogenic and Protective in Mice than a Prototypical
aroA
Mutant
Authors: Valentine Peter J. , Devore Brian P. , Heffron Fred 
Published: December 2019

ABSTRACT

A panel of
Salmonella typhimurium
14028s mutants, which were previously shown to be highly attenuated in the BALB/c mouse model of infection, were analyzed for their potential as live
Salmonella
oral-vaccine candidates. A prototypical
aroA
mutant was chosen as a basis of comparison. From the panel of mutants initially chosen for this study, three mutants with comparable levels of attenuation elicited higher
Salmonella
-specific serum immunoglobulin G (IgG) and/or mucosal secretory-IgA antibody titers than the
aroA
vaccine strain. The three mutants, CL288, CL401, and CL554, also elicited a better protective immune response than the
aroA
control strain, after a single oral dose of 1 × 10
9
to 2 × 10
9
bacteria.
Immunogenicity of FourPlasmodium falciparumPreerythrocytic Antigens inAotus lemurinusMonkeys
Authors: Perlaza Blanca Liliana , Arévalo-Herrera Myriam , Brahimi Karima , Quintero Gustavo , Palomino Julio Cesar , Gras-Masse Hélène , Tartar André , Druilhe Pierre , Herrera Sócrates 
Published: December 2019

ABSTRACTAotus lemurinusmonkeys were immunized with pools of either lipid-tailed peptides injected in PBS or peptides in Montanide ISA-51, all derived from fourPlasmodium falciparumpre-erythrocytic antigens, namely, LSA1, LSA3, SALSA, and STARP. These formulations were well tolerated. Their immunogenicity was demonstrated by the induction of both B- and T-cell responses to most of the peptides studied (of the 12, 10 induced antibody production, 9 induced T-cell proliferative responses, and all 12 induced gamma interferon secretion). Immune responses proved to be long lasting, since some were still detectable 210 days after immunization. Of particular importance is the fact that B- and T-cell responses elicited in this way by synthetic peptides were specific for native parasite proteins onP. falciparumsporozoites and liver stage parasites.