bluuebunny/crossref_metadata_2025_split huggingface dataset:
Expression of Mucin-Type Glycoprotein K88 Receptors Strongly Correlates with Piglet Susceptibility to K88+EnterotoxigenicEscherichia coli, but Adhesion of This Bacterium to Brush Borders Does Not
Authors: Francis David H. , Grange Philippe A. , Zeman David H. , Baker Diane R. , Sun Ronggai , Erickson Alan K. 
Published: March 2020

ABSTRACTThree antigenic variants of the K88 fimbrial adhesin exist in nature, K88ab, K88ac, and K88ad. EnterotoxigenicEscherichia coli(ETEC) strains that produce these fimbriae cause life-threatening diarrhea in some but not all young pigs. The susceptibility of pigs to these organisms has been correlated with the adherence of bacteria to isolated enterocyte brush borders. Whether that correlation holds for multiple K88 variants and over a broad genetic base of pigs is unknown and was the impetus for this study. We also desired to examine the correlation of the expression of a porcine intestinal brush border mucin-type glycoprotein (IMTGP) which binds K88ab and K88ac with the susceptibility of piglets to K88+ETEC. Of 31 neonatal gnotobiotic pigs inoculated with K88ab+or K88ac+ETEC, 13 developed severe diarrhea, became dehydrated, and died or became moribund. Another pig became severely lethargic but not dehydrated. In vitro brush border adherence analysis was not possible for 10 of the severely ill pigs due to colonization by challenge strains. However, of the 17 pigs that did not become severely ill, 8 (47%) had brush borders that supported the adherence of K88ab+and K88ac+bacteria in vitro, suggesting a poor correlation between in vitro brush border adherence and piglet susceptibility to K88+ETEC. By contrast, the expression of IMTGP was highly correlated with susceptibility to K88+ETEC. Of the 12 pigs that produced IMTGP, 11 developed severe diarrhea. The other pig that produced IMTGP became lethargic but not severely diarrheic. Only 2 of 18 pigs that did not produce IMTGP became severely diarrheic. Colonizing bacteria were observed in histologic sections of intestines from all pigs that expressed IMTGP except for the one that did not develop severe diarrhea. However, colonizing bacteria were observed in histologic sections from only one pig that did not produce IMTGP. The bacterial concentration in the jejuna and ilea of pigs expressing IMTGP was significantly greater (P< 0.005) than that in pigs not expressing IMTGP. These observations suggest the IMTGP is a biologically relevant receptor for K88ab+and K88ac+E. colior a correlate for expression for such a receptor.
Stimulation of Nitric Oxide Production in Macrophages byBabesia bovis
Authors: Stich Roger W. , Shoda Lisl K. M. , Dreewes Miriam , Adler Barbara , Jungi Thomas W. , Brown Wendy C. 
Published: March 2020

ABSTRACTGamma interferon (IFN-γ)-activated macrophages are believed to play a key role in resistance toBabesia bovisthrough parasite suppression by macrophage secretory products. However, relatively little is known about interactions between this intraerythrocytic parasite and the macrophages of its bovine host. In this study, we examined the in vitro effect of intact and fractionatedB. bovismerozoites on bovine macrophage nitric oxide (NO) production. In the presence of IFN-γ,B. bovismerozoites stimulated NO production, as indicated by the presence of increasedl-arginine-dependent nitrite (NO2−) levels in culture supernatants of macrophages isolated from several cattle. The merozoite crude membrane (CM) fraction stimulated greater production of NO, in a dose-dependent manner, than did the merozoite homogenate or the soluble, cytosolic high-speed supernatant fraction. Stimulation of NO production by CM was enhanced by as little as 1 U of IFN-γ per ml of culture medium. Upregulation of inducible NO synthase mRNA in bovine macrophages by eitherB. bovis-parasitized erythrocytes and IFN-γ or CM was also observed.B. bovis-specific T-helper lymphocyte culture supernatants, all of which contained IFN-γ, were also found to inducel-arginine-dependent NO2−production. Supernatants that induced the highest levels of NO also contained biologically active TNF. These results show thatB. bovismerozoites and antigen-stimulatedB. bovis-immune T cells can induce the production of NO, a molecule implicated in both protection and pathologic changes associated with hemoprotozoan parasite infections.
Production and Characterization of a Set of Mouse-Human Chimeric Immunoglobulin G (IgG) Subclass and IgA Monoclonal Antibodies with Identical Variable Regions Specific forPseudomonas aeruginosaSerogroup O6 Lipopolysaccharide
Authors: Preston Michael J. , Gerçeker A. Alev , Reff Mitchell E. , Pier Gerald B. 
Published: March 2020

ABSTRACTThe heavy- and light-chain variable regions from a murine monoclonal antibody that recognizePseudomonas aeruginosaserogroup O6 lipopolysaccharide (LPS) were used to generate a series of chimeric mouse-human monoclonal antibodies with identical variable regions. The murine variable-region gene segments were cloned into an immunoglobulin (Ig) cDNA expression vector that contained the human kappa light-chain and IgG1 constant regions. The IgG1 heavy-chain constant region was then replaced with the human IgG2, IgG3, IgG4, or IgA1 heavy-chain constant region. The five different expression vectors were transfected into Chinese hamster ovary cells for antibody production. The chimeric antibodies exhibited immunoreactivity and affinity similar to that of the parental murine IgG antibody toward whole cells of a serogroup O6 strain. In vitro complement deposition assays demonstrated that the chimeric IgG4 and IgA antibodies did not mediate the deposition of complement component C3 onto the surface of either purified LPS or whole bacteria. The chimeric IgG1 and IgG3 antibodies were similar in their ability to deposit C3 onto the surface of both bacteria and LPS, while IgG2 antibody was more effective at depositing C3 onto the surface of bacteria than onto purified LPS. The pattern of opsonophagocytic activity of the chimeric monoclonal antibodies was similar to that of complement deposition onto bacterial cells in that the chimeric IgG1 and IgG3 had the highest opsonic activity. Although IgG2 deposited more C3 onto the bacterial surface than did IgG4 or IgA, all three of these isotypes had low opsonic activity against the serogroup O6 target strain. This series of related antibodies will help reveal functional differences in efficacy among protective antibodies toP. aeruginosaand will be critical for defining the optimal formulation of either a vaccine for active immunization or a polyclonal intravenous IgG or monoclonal antibody cocktail for passive immunotherapy.
Requirement of theShigella flexneriVirulence Plasmid in the Ability To Induce Trafficking of Neutrophils across Polarized Monolayers of the Intestinal Epithelium
Authors: McCormick Beth A. , Siber Andrew M. , Maurelli Anthony T. 
Published: March 2020

ABSTRACTAttachment of an array of enteric pathogens to epithelial surfaces is accompanied by recruitment of polymorphonuclear leukocytes (PMN) across the intestinal epithelium. In this report, we examine howShigella-intestinal epithelium interactions evoke the mucosal inflammatory response. We modeled these interactions in vitro by using polarized monolayers of the human intestinal epithelial cell line, T84, isolated human PMNs, andShigella flexneri. We show thatShigellaattachment to T84-cell basolateral membranes was a necessary component in the signaling cascade for induction of basolateral-to-apical directed transepithelial PMN migration, the direction of PMN transepithelial migration in vivo. In contrast, attachment ofShigellato the T84-cell apical membrane failed to stimulate a directed PMN transepithelial migration response. Importantly, the ability ofShigellato induce PMN migration across epithelial monolayers was dependent on the presence of the 220-kb virulence plasmid. Moreover, examination ofShigellagenes necessary to signal subepithelial neutrophils established the requirement of a functional type III secretion system. Our results indicate that the ability ofShigellato elicit transepithelial signaling to neutrophils from the basolateral membrane of epithelial cells represents a mechanism involved inShigella-elicited enteritis in humans.
The Phosphorylcholine Epitope Undergoes Phase Variation on a 43-Kilodalton Protein in
Pseudomonas aeruginosa
and on Pili of
Neisseria meningitidis
and
Neisseria gonorrhoeae
Authors: Weiser Jeffrey N. , Goldberg Joanna B. , Pan Nina , Wilson Lynn , Virji Mumtaz 
Published: March 2020

ABSTRACT

Phosphorylcholine (ChoP) is a component of the teichoic acids of
Streptococcus pneumoniae
and has been recently identified on the lipopolysaccharide of
Haemophilus influenzae
, also a major pathogen of the human respiratory tract. Other gram-negative pathogens that frequently infect the human respiratory tract were surveyed for the presence of the ChoP epitope as indicated by binding to monoclonal antibodies (MAbs) recognizing this structure. The ChoP epitope was found on a 43-kDa protein on all clinical isolates of
Pseudomonas aeruginosa
examined and on several class I and II pili of
Neisseria meningitidis
. The specificity of the anti-ChoP MAb was demonstrated by the inhibition of binding in the presence of ChoP but not structural analogs. As in the case of
H. influenzae
, the expression of this epitope was phase variable on these species. In
P. aeruginosa
, this epitope was expressed at detectable levels only at lower growth temperatures. Expression of the ChoP epitope on piliated neisseriae displayed phase variation, both linked to pilus expression and independently of fully piliated bacteria.
Contribution of Regulation by the
bvg
Locus to Respiratory Infection of Mice by
Bordetella pertussis
Authors: Merkel Tod J. , Stibitz Scott , Keith Jerry M. , Leef Mary , Shahin Roberta 
Published: March 2020

ABSTRACT

Whooping cough is an acute respiratory disease caused by the small, gram-negative bacterium
Bordetella pertussis. B. pertussis
expresses several factors that contribute to its ability to cause disease. These factors include surface-associated molecules, which are involved in the adherence of the organism to respiratory epithelial cells, as well as several extracellular toxins that inhibit host defenses and induce damage to host tissues. The expression of virulence factors in
B. pertussis
is dependent upon the
bvg
locus, which consists of three genes:
bvgA
,
bvgS
, and
bvgR
. The
bvgAS
genes encode a two-component regulatory system consisting of a sensor protein, BvgS, and a transcriptional activator, BvgA. Upon modification by BvgS, BvgA binds to the promoter regions of the
bvg
-activated genes and activates transcription. One of the
bvg
-activated genes,
bvgR
, is responsible for the regulation of the
bvg
-repressed genes, the functions of which are unknown. The fact that these genes are regulated by the
bvg
locus suggests that they play a role in the pathogenesis of the bacterium. In order to evaluate the contribution of
bvg
-mediated regulation to the virulence of
B. pertussis
and determine if expression of the
bvg
-repressed genes is required for the virulence of
B. pertussis
, we examined the ability of
B. pertussis
mutants, defective in their ability to regulate the expression of the
bvg
-activated and/or the
bvg
-repressed genes, to cause disease in the mouse aerosol challenge model. Our results indicate that the
bvgR
-mediated regulation of gene expression contributes to respiratory infection of mice.
Entry of
Listeria monocytogenes
into Neurons Occurs by Cell-to-Cell Spread: an In Vitro Study
Authors: Dramsi S. , Lévi S. , Triller A. , Cossart P. 
Published: March 2020

ABSTRACT

Listeria monocytogenes
is an intracellular pathogen that causes severe central nervous system infection in humans and animals. The ability of this bacterium to penetrate nerve cells was investigated by using rat spinal cell cultures. Entry into distinct cell types, i.e., glial cells and neurons, was monitored by a differential immunofluorescence technique with antibodies against cell type-specific markers and the bacterial pathogen.
L. monocytogenes
was detected predominantly within macrophages constituting the microglia. Astrocytes and oligodendrocytes, the major components of macroglia, were infected to a lesser extent. Surprisingly,
Listeria innocua
, a noninvasive and nonpathogenic species, also has the capacity to enter into these three types of glial cells. Entry into neurons was a very rare event. In contrast, we found that
L. monocytogenes
could efficiently invade neurons when these latter cells were cocultivated with
Listeria
-infected mouse macrophages. In this case, infection of neurons occurs by cell-to-cell spread via an
actA
-dependent mechanism. These data support the notion that infected phagocytes can be vectors by which
L. monocytogenes
gains access to privileged niches such as the central nervous system.
Role of CR4 inMycobacterium tuberculosis-Human Macrophages Binding and Signal Transduction in the Absence of Serum
Authors: Zaffran Yona , Zhang Li , Ellner Jerrold J. 
Published: March 2020

ABSTRACTThe β2 integrin CR4 is involved inMycobacterium tuberculosisphagocytosis by human mononuclear phagocytes through the opsonin C3bi. In this study, we demonstrate thatM. tuberculosiscan bind directly to monocyte-derived macrophages via CR4 in the absence of any opsonins. CR4-transfected CHO cells gave similar results, suggesting recognition by CR4 of bacterial structure. Furthermore, binding ofM. tuberculosistransduced a potent signal, resulting in tyrosine phosphorylation of macrophage proteins, which was in part mediated by CR4.
Escherichia coliO157:H7 Requires Intimin for Enteropathogenicity in Calves
Authors: Dean-Nystrom Evelyn A. , Bosworth Brad T. , Moon Harley W. , O’Brien Alison D. 
Published: March 2020

ABSTRACTEnterohemorrhagicEscherichia coli(EHEC) strains require intimin to induce attaching and effacing (A/E) lesions in newborn piglets. Infection of newborn calves with intimin-positive or intimin-negative EHEC O157:H7 demonstrated that intimin is needed for colonization, A/E lesions, and disease in cattle. These results suggest that experiments to determine if intimin-based vaccines reduce O157:H7 levels in cattle are warranted.
Phase Variations of the
Mycoplasma penetrans
Main Surface Lipoprotein Increase Antigenic Diversity
Authors: Neyrolles Olivier , Chambaud Isabelle , Ferris Stéphane , Prevost Marie-Christine , Sasaki Tsuguo , Montagnier Luc , Blanchard Alain 
Published: March 2020

ABSTRACT

Mycoplasma penetrans
is a recently identified mycoplasma, isolated from urine samples collected from human immunodeficiency virus (HIV)-infected patients. Its presence is significantly associated with HIV infection. The major antigen recognized during natural and experimental infections is an abundant P35 lipoprotein which, upon extraction, segregates in the Triton X-114 detergent phase and is the basis of
M. penetrans
-specific serological assays. We report here that the P35 antigen undergoes spontaneous and reversible phase variation at high frequency, leading to heterogeneous populations of mycoplasmas, even when derived from a clonal lineage. This variation was found to be determined at the transcription level, and although this property is not unique among the members of the class
Mollicutes
, the mechanism by which it occurs in
M. penetrans
differs from those previously described for other
Mycoplasma
species. Indeed, the P35 phase variation was due neither to a
p35
gene rearrangement nor to point mutations within the gene itself or its promoter. The P35 phase variation in the different variants obtained was concomitant with modifications in the pattern of other expressed lipoproteins, probably due to regulated expression of selected members of a gene family which was found to potentially encode similar lipoproteins.
M. penetrans
variants could be selected on the basis of their lack of colony immunoreactivity with a polyclonal antiserum against a Triton X-114 extract, strongly suggesting that the mechanisms involved in altering surface antigen expression might allow evasion of the humoral immune response of the infected host.
Lipopolysaccharide Enhances the Production of Vascular Endothelial Growth Factor by Human Pulp Cells in Culture
Authors: Matsushita K. , Motani R. , Sakuta T. , Nagaoka S. , Matsuyama T. , Abeyama K. , Maruyama I. , Takada H. , Torii M. 
Published: March 2020

ABSTRACTWe investigated whether vascular endothelial growth factor (VEGF) production by human pulp cells (HPC) is regulated by lipopolysaccharide (LPS) in relation to the pathogenesis of pulpitis. Although HPC incubated with medium alone only marginally expressed VEGF mRNA and produced a low level of VEGF as detected by enzyme-linked immunosorbent assay, the VEGF mRNA expression and VEGF production were markedly enhanced upon stimulation with LPS fromEscherichia coli. Prevotella intermediaLPS, phorbol 12-myristate 13-acetate, and interleukin-6 also induced VEGF mRNA expression in HPC. A simian virus 40-infected HPC line also exhibited increased VEGF mRNA expression in response toE. coliLPS, but lung and skin fibroblasts did not. Fetal bovine serum (FBS) increased the sensitivity of HPC to LPS in a dose-dependent manner. HPC did not express membrane CD14 on their surfaces. However, the anti-CD14 monoclonal antibody MY4 inhibited VEGF induction upon stimulation with LPS in HPC cultures in the presence of 10% FBS but not in the absence of FBS. LPS augmented the VEGF production in HPC cultures in the presence of recombinant human soluble CD14 (sCD14). To clarify the mechanisms of VEGF induction by LPS, we examined the possible activation of the transcription factor AP-1 in HPC stimulated with LPS, by a gel mobility shift assay. AP-1 activation in HPC was clearly observed, whereas that in skin fibroblasts was not. The AP-1 inhibitor curcumin strongly inhibited LPS-induced VEGF production in HPC cultures. In addition, a protein synthesis inhibitor, cycloheximide, inhibited VEGF mRNA accumulation in response to LPS. These results suggest that the enhanced production of VEGF in HPC induced by LPS takes place via an sCD14-dependent pathway which requires new protein synthesis and is mediated in part through AP-1 activation.
Molecular Characterization of aHaemaphysalis longicornisTick Salivary Gland-Associated 29-Kilodalton Protein and Its Effect as a Vaccine against Tick Infestation in Rabbits
Authors: Mulenga Albert , Sugimoto Chihiro , Sako Yasuhito , Ohashi Kazuhiko , Musoke Anthony , Shubash Mozaria , Onuma Misao 
Published: March 2020

ABSTRACTThe use of tick vaccines in mammalian hosts has been shown to be the most promising alternative tick control method to current use of acaricides, which suffers from a number of limitations. However, the success of this method is dependent on the identification, cloning, and in vitro expression of tick molecules involved in the mediation of key physiological roles with respect to the biological success of a tick as a vector and pest. We have sequenced and characterized aHaemaphysalis longicornistick salivary gland-associated cDNA coding for a 29-kDa extracellular matrix-like protein. This protein is expressed in both unfed and fed immature and matureH. longicornisticks. The predicted amino acid sequence of p29 shows high homology to sequences of some known extracellular matrix like-proteins with the structural conservation similar to all known collagen proteins. Immunization with the recombinant p29 conferred a significant protective immunity in rabbits, resulting in reduced engorgement weight for adult ticks and up to 40 and 56% mortality in larvae and nymphs that fed on the immunized rabbits. We speculate that this protein is associated with formation of tick cement, a chemical compound that enables the tick to remain attached to the host, and suggest a role for p29 as a candidate tick vaccine molecule for the control of ticks. We have discussed our findings with respect to the search of tick molecules for vaccine candidates.
Cryptococcus neoformans
Differential Gene Expression Detected In Vitro and In Vivo with Green Fluorescent Protein
Authors: del Poeta Maurizio , Toffaletti Dena L. , Rude Thomas H. , Sparks Sara D. , Heitman Joseph , Perfect John R. 
Published: March 2020

ABSTRACT

Synthetic green fluorescent protein (GFP) was used as a reporter to detect differential gene expression in the pathogenic fungus
Cryptococcus neoformans
. Promoters from the
C. neoformans
actin, GAL7, or mating-type alpha pheromone (MFα1) genes were fused to GFP, and the resulting reporter genes were used to assess gene expression in serotype A
C. neoformans
. Yeast cells containing an integrated pACT::GFP construct demonstrated that the actin promoter was expressed during vegetative growth on yeast extract-peptone-dextrose medium. In contrast, yeast cells containing the inducible GAL7::GFP or MFα1::GFP reporter genes expressed significant GFP activity only during growth on galactose medium or V-8 agar, respectively. These findings demonstrated that the GAL7 and MFα1 promoters from a serotype D
C. neoformans
strain function when introduced into a serotype A strain. Because the MFα1 promoter is induced by nutrient deprivation and the
MATα
locus containing the MFα1 gene has been linked with virulence, yeast cells containing the pMFα1::GFP reporter gene were analyzed for GFP expression in the central nervous system (CNS) of immunosuppressed rabbits. In fact, significant GFP expression from the MFα1::GFP reporter gene was detected after the first week of a CNS infection. These findings suggest that there are temporal, host-specific cues that regulate gene expression during infection and that the MFα1 gene is induced during the proliferative stage of a CNS infection. In conclusion, GFP can be used as an effective and sensitive reporter to monitor specific
C. neoformans
gene expression in vitro, and GFP reporter constructs can be used as an approach to identify a novel gene(s) or to characterize known genes whose expression is regulated during infection.
Risk Factors in the Pathogenesis of Invasive Group A Streptococcal Infections: Role of Protective Humoral Immunity
Authors: Basma Hesham , Norrby-Teglund Anna , Guedez Yajaira , McGeer Allison , Low Donald E. , El-Ahmedy Omar , Schwartz Benjamin , Kotb Malak 
Published: March 2020

ABSTRACTAn impressive change in the epidemiology and severity of invasive group A streptococcal infections occurred in the 1980s, and the incidence of streptococcal toxic shock syndrome cases continues to rise. The reason for the resurgence of severe invasive cases remains a mystery—has there been a change in the pathogen or in host protective immunity? To address these questions, we have studied 33 patients with invasive infection caused by genotypically indistinguishable M1T1 strains ofStreptococcus pyogeneswho had different disease outcomes. Patients were classified as having severe (n= 21) and nonsevere (n= 12) invasive infections based on the presence or absence of shock and organ failure. Levels of anti-M1 bactericidal antibodies and of anti-streptococcal superantigen neutralizing antibodies in plasma were significantly lower in both groups than in age- and geographically matched healthy controls (P< 0.01). Importantly, the levels of these protective antibodies in plasma samples from severe and nonsevere invasive cases were not different. Together the data suggest that low levels of protective antibodies may contribute to host susceptibility to invasive streptococcal infection but do not modulate disease outcome. Other immunogenetic factors that regulate superantigen responses may influence the severity of systemic manifestations associated with invasive streptococcal infection.