bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Vitro and In Vivo Stability aCryptococcus neoformansGlucuronoxylomannan Epitope That Elicits Protective Antibodies
Authors: Cleare Wendy , Cherniak Robert , Casadevall Arturo 
Published: December 2019

ABSTRACTThe monoclonal antibody (MAb) 2H1 defines an epitope inCryptococcus neoformanscapsular glucuronoxylomannan (GXM) that can elicit protective antibodies. In murine models of cryptococcosis, MAb 2H1 administration prolongs survival and reduces fungal burden but seldom clears the infection. The mechanism by whichC. neoformanspersists and escape antibody-mediated clearance is not understood. One possibility is that variants that do not bind MAb 2H1 emerge in the course of infection. Using an agglutination-sedimentation protocol, we recovered a variant of strain 24067 that did not agglutinate, could not be serotyped, and had marked reduction in GXMO-acetyl groups. Binding of MAb 2H1 to 24067 variant cells produced a different immunofluorescence pattern and lower fluorescence intensity relative to the parent 24067 cells. Addition of MAb 2H1 to 24067 variant cells had no effect on cell charge. Phagocytic assays demonstrated that MAb 2H1 was not an effective opsonin for the 24067 variant. The 24067 variant was less virulent than the 24067 parent strain in mice, and MAb 2H1 administration did not prolong survival in animals infected with the variant strain. To investigate whether variants which do not bind MAb 2H1 are selected in experimental infection, threeC. neoformansstrains were serially passaged in mice given either MAb 2H1 or no antibody. Analysis of passaged isolates by agglutination assay, flow cytometry, and indirect immunofluorescence revealed changes in MAb 2H1 epitope expression but no clear trend with regards to gain or loss of MAb 2H1 epitope.C. neoformansvariants with reduced MAb 2H1 epitope content can be isolated in vitro, but persistence of infection in mice given MAb 2H1 does not appear to be a result of selection of escape variants that lack the MAb 2H1 epitope.
Analysis of Vaginal Cell Populations during Experimental Vaginal Candidiasis
Authors: Fidel Paul L. , Luo Wei , Steele Chad , Chabain Joseph , Baker Marc , Wormley Floyd 
Published: December 2019

ABSTRACTStudies with an estrogen-dependent murine model of vaginal candidiasis suggest that local cell-mediated immunity (CMI) is more important than systemic CMI for protection against vaginitis. The present study, however, showed that, compared to uninfected mice, little to no change in the percentage or types of vaginal T cells occurred during a primary vaginal infection or during a secondary vaginal infection where partial protection was observed. Furthermore, depletion of polymorphonuclear leukocytes (PMN) had no effect on infection in the presence or absence of pseudoestrus. These results indicate a lack of demonstrable effects by systemic CMI or PMN against vaginitis and suggest that if local T cells are important, they are functioning without showing significant increases in numbers within the vaginal mucosa during infection.
Promoter Architecture of the
Porphyromonas gingivalis
Fimbrillin Gene
Authors: Xie Hua , Lamont Richard J. 
Published: December 2019

ABSTRACT

Porphyromonas gingivalis
fimbriae can mediate adherence to many of the available substrates in the oral cavity. Expression of
P. gingivalis
fimbriae is regulated at the transcriptional level by environmental signals, such as temperature and hemin concentration. The arrangement of the upstream promoter and regulatory sequences required for transcription and control of the fimbrial structural gene (
fimA
) was investigated. Primer extension analysis demonstrated that the transcriptional start site of the
fimA
gene is located 41 bp upstream from the translational start codon. A region (
upf
) spanning 648 bp upstream of the start codon to 44 bp downstream of the translational start site was cloned upstream of a promoterless
lacZ
reporter gene. A series of deletion and base substitution mutations were then generated in the
upf
region. The constructs were introduced into the chromosome of
P. gingivalis
, and promoter activity measured by assaying levels of β-galactosidase. The results showed that
fimA
contains sequences resembling ς
70
promoter consensus sequences, consisting of a −10 region (TATGAC) located at −18 to −23 and a −35 region (TTGTTG) located at −41 to −46 from the transcriptional start point. The AT-rich upstream sequences spanning bases −48 to −85 and bases −90 to −240 were required for full expression of the
fimA
gene, indicating the existence of positive regulation regions. Moreover, the −48 to −64 region may constitute an UP element, contributing to promoter activity in
P. gingivalis
. Thus, our data suggest that the
P. gingivalis fimA
gene has a transcription complex consisting of −10 and −35 sequences, an UP element, and additional AT-rich upstream regulatory sequences.
Coxiella burnetiiInfection Increases Transferrin Receptors on J774A.1 Cells
Authors: Howe Dale , Mallavia Louis P. 
Published: December 2019

ABSTRACTInoculation with viable, but not inactivated,Coxiella burnetiiresulted in the increased expression of transferrin receptors (TfR) in the murine macrophage-like cell line J774A.1. This upregulation was evident in immunoblots as early as 6 h postinfection, with TfR levels continuing to increase through the first 24 h of infection. Fluorescent labeling revealed that TfR upregulation occurred throughout infected monolayers, eliminating the possibility that it reflected a response by a minor subset of host cells. In addition, TfR trafficking did not appear to be affected byC. burnetiiinfection. Consistent with the increase in TfRs, inoculation with viableC. burnetiiresulted in a 2.5-fold increase in total cellular iron by 12 h postinoculation. Our further findings that the chelation of intracellular iron arrestsC. burnetiireplication and thatC. burnetiimetabolic activities in vitro are affected by iron concentration suggest that TfR upregulation is a salient factor inC. burnetiiinfection, and we speculate that it may represent a significant virulence mechanism.
Cytotoxic T-Lymphocyte Epitopes Fused to Anthrax Toxin Induce Protective Antiviral Immunity
Authors: Doling Amy M. , Ballard Jimmy D. , Shen Hao , Krishna Kaja Murali , Ahmed Rafi , Collier R. John , Starnbach Michael N. 
Published: December 2019

ABSTRACTWe have investigated the use of the protective antigen (PA) and lethal factor (LF) components of anthrax toxin as a system for in vivo delivery of cytotoxic T-lymphocyte (CTL) epitopes. During intoxication, PA directs the translocation of LF into the cytoplasm of mammalian cells. Here we demonstrate that antiviral immunity can be induced in BALB/c mice immunized with PA plus a fusion protein containing the N-terminal 255 amino acids of LF (LFn) and an epitope from the nucleoprotein (NP) of lymphocytic choriomeningitis virus. We also demonstrate that BALB/c mice immunized with a single LFn fusion protein containing NP and listeriolysin O protein epitopes in tandem mount a CTL response against both pathogens. Furthermore, we show that NP-specific CTL are primed in both BALB/c and C57BL/6 mice when the mice are immunized with a single fusion containing two epitopes, one presented by Ldand one presented by Db. The data presented here demonstrate the versatility of the anthrax toxin delivery system and indicate that this system may be used as a general approach to vaccinate outbred populations against a variety of pathogens.
Prevalence of, Antibody Response to, and Immunity Induced byHaemophilus ducreyiHemolysin
Authors: Dutro Susan M. , Wood Gwendolyn E. , Totten Patricia A. 
Published: December 2019

ABSTRACTHaemophilus ducreyi, the etiologic agent of chancroid, a genital ulcer disease, produces a cell-associated hemolysin whose role in virulence is not well defined. Hemolysin is encoded by two genes,hhdAandhhdB, which, based on their homology toSerratia marcescens shlAandshlBgenes, are believed to encode the hemolysin structural protein and a protein required for secretion and modification of this protein, respectively. In this study, we determined the prevalence and expression of the hemolysin genes in 90H. ducreyiisolates obtained from diverse geographic locations from 1952 to 1996 and found that all strains contained DNA homologous to thehhdBandhhdAgenes. In addition, all strains expressed a hemolytic activity. We also determined that hemolysin is expressed in vivo and is immunogenic, as indicated by the induction of antibodies to hemolysin in both the primate and rabbit disease models as well as in human patients with naturally acquired chancroid. Wild-type strain 35000 and isogenic hemolysin-negative mutants showed no difference in lesion development in the temperature-dependent rabbit model. However, immunization of rabbits with the purified hemolysin protein reduced the recovery of wild-typeH. ducreyi, but not hemolysin-negative mutants, from lesions. Our study indicates that hemolysin is a possible candidate for vaccine development due to its immunogenicity, expression in vitro and in vivo by most, if not all, strains, and the effect of immunization on reducing the recovery of viableH. ducreyiin experimental disease in rabbits.
Schistosoma mansoniActivates Host Microvascular Endothelial Cells To Acquire an Anti-Inflammatory Phenotype
Authors: Trottein Francois , Descamps Laurence , Nutten Sophie , Dehouck Marie-Pierre , Angeli Veronique , Capron Andre , Cecchelli Romeo , Capron Monique 
Published: December 2019

ABSTRACTSince endothelial cells (ECs) play a key role in immune defense mechanisms and in immunopathology, we investigated whether the intravascular helminth parasiteSchistosoma mansonicould interact with and activate resting ECs in vitro. Microscopic analysis revealed that the lung-stage schistosomula specifically attached to microvascular ECs. This adherence was associated to active cellular processes involving actin filament formation. Since variation of permeability of cultured capillary brain ECs is a good marker for endothelial activation, the transendothelial passage of a low-molecular-weight molecule (inulin) on monolayers of bovine brain capillary ECs (BBCEC) was measured in response to parasites. Schistosomula induced a dramatic decrease in transendothelial permeability, a characteristic marker for the generation of an anti-inflammatory phenotype to ECs. This paracellular barrier enhancing effect on endothelial monolayers was due to a soluble substance(s) (below 1 kDa in size) secreted fromS. mansonischistosomula and not by mechanisms associated to adherence between parasites and ECs. The reinforcement of the endothelial barrier function was accompanied by an elevation of intracellular concentration of cyclic AMP (cAMP). The use of specific kinase inhibitors confirms that schistosomula activate ECs through a cAMP/protein kinase A pathway that leads to an increased phosphorylation of the myosin light-chain kinase. These combined findings suggest that the secretory/excretory products from schistosomula possess anti-inflammatory factor(s) that signal host microvascular endothelium. The immunological consequences of such activation are discussed.
Chemokine Gene Expression duringPneumocystis carinii-Driven Pulmonary Inflammation
Authors: Wright Terry W. , Johnston Carl J. , Harmsen Allen G. , Finkelstein Jacob N. 
Published: December 2019

ABSTRACTSevere combined immunodeficient (SCID) mice lack functional lymphocytes and therefore developPneumocystis cariniipneumonia. However, when infected SCID mice are immunologically reconstituted with congenic spleen cells, a protective inflammatory cascade is initiated. Proinflammatory cytokines are produced, and lymphocytes and macrophages are recruited specifically to alveolar sites of infection. Importantly, uninfected regions of the lung remain free from inflammatory involvement, suggesting that there are specific mechanisms that limit inflammation in the infected lung. Therefore, to determine whether chemokines are involved in targeting theP. carinii-driven inflammatory response, steady-state mRNA levels of several chemokines were measured in the lungs of both reconstituted and nonreconstitutedP. carinii-infected SCID mice. Despite significant organism burdens in the lungs of 8- and 10-week-old SCID mice, there was no evidence of elevated chemokine gene expression, which is consistent with the lack of an inflammatory response in these animals. However, when 8-week-old infected SCID mice were immunologically reconstituted, signs of focal pulmonary inflammation were observed, and levels of RANTES, MCP-1, lymphotactin, MIP-1α, MIP-1β, and MIP-2 mRNAs were all significantly elevated. Chemokine mRNA abundance was elevated at day 10 postreconstitution (PR), was maximal at day 12 PR, and returned to baseline by day 22 PR. In situ hybridization demonstrated that during the peak of inflammation, RANTES gene expression was localized to sites of inflammatory cell infiltration andP. cariniiinfection. Thus, these observations indicate that chemokines play a role in the focal targeting of inflammatory cell recruitment to sites ofP. cariniiinfection after the passive transfer of lymphocytes to the host.
Dissemination ofListeria monocytogenesby Infected Phagocytes
Authors: Drevets Douglas A. 
Published: December 2019

ABSTRACTIn vitro data suggest that blood-borneListeria monocytogenesorganisms enter the central nervous system (CNS) by direct invasion of endothelial cells or by cell-to-cell spread from infected phagocytes to endothelial cells. However, a role for infected phagocytes in neuroinvasion and dissemination ofL. monocytogenesin vivo has not been confirmed experimentally. Experiments described here tested whetherL. monocytogenes-infected peripheral blood leukocytes (PBL) circulated in bacteremic mice and could establish organ infection in vivo. A mean of 30.5% of bacteria cultured from whole blood were PBL associated, and microscopy showed that 22.2% of monocytes and 1.6% of neutrophils were infected. PBL-associated bacteria spread to endothelial cells in vitro, indicating their potential for virulence in vivo. To test this possibility, mice were injected intravenously with infected PBL and CFU of bacteria in liver, spleen, and brain were quantified and compared with values for mice injected with broth-grown bacteria and in vitro-infected macrophage cell lines. An inoculum of infected macrophage cell lines led to greater numbers of bacteria in the liver than the numbers produced by a similar inoculum of broth-grown bacteria. In contrast, brain infection was best established by infected PBL. Results of intraperitoneal injection of infected peritoneal cells compared with results of injection with infected J774A.1 cells suggested that unrestricted intracellular bacterial replication within J774A.1 cells contributed to excessive liver infection in those mice. These data show dissemination of intracellularL. monocytogenesand indicate that phagocyte-facilitated invasion has a role in CNS infection in vivo. Heterogeneity with regard to bactericidal activity as well as to other phagocyte characteristics is a critical feature of this mechanism.
Role of the 85-Kilobase Plasmid and Plasmid-Encoded Virulence-Associated Protein A in Intracellular Survival and Virulence ofRhodococcus equi
Authors: Giguère Steeve , Hondalus Mary K. , Yager Julie A. , Darrah Patricia , Mosser David M. , Prescott John F. 
Published: December 2019

ABSTRACTRhodococcus equiis a facultative intracellular pathogen of macrophages and a cause of pneumonia in young horses (foals) and immunocompromised people. Isolates ofR. equifrom pneumonic foals typically contain large, 85- or 90-kb plasmids encoding a highly immunogenic virulence-associated protein (VapA). The objective of this study was to determine the role of the 85-kb plasmid and VapA in the intracellular survival and virulence ofR. equi. Clinical isolates containing the plasmid and expressing VapA efficiently replicated within mouse macrophages in vitro, while plasmid-cured derivatives of these organisms did not multiply intracellularly. An isolate harboring the large plasmid also replicated in the tissues of experimentally infected mice, whereas its plasmid-cured derivative was rapidly cleared. All foals experimentally infected with a plasmid-containing clinical isolate developed severe bronchopneumonia, whereas the foals infected with its plasmid-cured derivative remained asymptomatic and free of visible lung lesions. By day 14 postinfection, lung bacterial burdens had increased considerably in foals challenged with the plasmid-containing clinical isolate. In contrast, bacteria could no longer be cultured from the lungs of foals challenged with the isogenic plasmid-cured derivative. A recombinant, plasmid-cured derivative expressing wild-type levels of VapA failed to replicate in macrophages and remained avirulent for both mice and foals. These results show that the 85-kb plasmid ofR. equiis essential for intracellular replication within macrophages and for development of disease in the native host, the foal. However, expression of VapA alone is not sufficient to restore the virulence phenotype.
The Capsule Supports Survival but Not Traversal ofEscherichia coliK1 across the Blood-Brain Barrier
Authors: Hoffman Jill A. , Wass Carol , Stins Monique F. , Kim Kwang Sik 
Published: December 2019

ABSTRACTThe vast majority of cases of gram-negative meningitis in neonates are caused by K1-encapsulatedEscherichia coli. The role of the K1 capsule in the pathogenesis ofE. colimeningitis was examined with an in vivo model of experimental hematogenousE. coliK1 meningitis and an in vitro model of the blood-brain barrier. Bacteremia was induced in neonatal rats with theE. coliK1 strain C5 (O18:K1) or its K1−derivative, C5ME. Subsequently, blood and cerebrospinal fluid (CSF) were obtained for culture. Viable bacteria were recovered from the CSF of animals infected withE. coliK1 strains only; none of the animals infected with K1−strains had positive CSF cultures. However, despite the fact that their cultures were sterile, the presence of O18E. coliwas demonstrated immunocytochemically in the brains of animals infected with K1−strains and was seen by staining of CSF samples. In vitro, brain microvascular endothelial cells (BMEC) were incubated with K1+and K1−E. colistrains. The recovery of viable intracellular organisms of the K1+strain was significantly higher than that for the K1−strain (P= 0.0005). The recovery of viable intracellular K1−E. colibacteria was increased by cycloheximide treatment of BMEC (P= 0.0059) but was not affected by nitric oxide synthase inhibitors or oxygen radical scavengers. We conclude that the K1 capsule is not necessary for the invasion of bacteria into brain endothelial cells but is responsible for helping to maintain bacterial viability during invasion of the blood-brain barrier.
Early Events in the Pathogenesis of Avian Salmonellosis
Authors: Henderson S. Christine , Bounous Denise I. , Lee Margie D. 
Published: December 2019

ABSTRACTSalmonellae are gastrointestinal pathogens of man and animals. However, strains that are host-specific avian pathogens are often avirulent in mammals, and those which are nonspecific are commensal in poultry. The objective of this study was to determine whether host specificity was exhibited by bacterial abilities to invade epithelial cells or resist leukocyte killing. In this study, leukocytes isolated from humans and chickens were used to killSalmonellain vitro. BothSalmonella pullorum, an avian-specific serotype, andSalmonella typhimurium, a broad-host-range serotype, were sensitive to killing by polymorphonuclear leukocytes isolated from both species. Both serotypes replicated in cells of the MQ-NCSU avian-macrophage cell line. In contrast,S. pullorumwas noninvasive for cultured epithelial Henle 407, chick kidney, chick ovary, and budgerigar abdominal tumor cells. In the bird challenge, however,S. typhimuriumrapidly caused inflammation of the intestinal mucosa, butS. pullorumpreferentially targeted the bursa of Fabricius prior to eliciting intestinal inflammation.Salmonellaserotypes which cause typhoid fever in mice have been shown to target the gut-associated lymphoid tissue. Observations from this study show thatS. pulloruminitiated a route of infection in chicks comparable to the route it takes in cases of enteric fever.
Resistance of VirulentMycobacterium aviumto Gamma Interferon-Mediated Antimicrobial Activity Suggests Additional Signals for Induction of Mycobacteriostasis
Authors: Flórido Manuela , Gonçalves Ana Sofia , Silva Regina A. , Ehlers Stefan , Cooper Andrea M. , Appelberg Rui 
Published: December 2019

ABSTRACTThe cytokine gamma interferon (IFN-γ) plays a major role in the control ofMycobacterium aviuminfections. We assessed whether the progressive growth of virulent strains ofM. aviumwas associated with alterations in the production of this cytokine as evaluated by reverse transcription-PCR and detection of immunoreactive cytokine in the serum and in spleen homogenates. We found that IFN-γ was induced during infection by a virulent strain ofM. aviumto similar or even higher extents than the levels found during infections by a less virulent strain whose growth was controlled. IFN-γ produced during infection by both mycobacterial strains was partly derived from T cells and led to activation of macrophages, namely, those that were infected. Concomitant with the development of the infection with the virulent strain ofM. aviumthere was an extensive depletion of lymphocytes in the spleen. Thymectomy alone promoted the proliferation of the virulent, but not of the less virulent, strain ofM. avium. Our data indicate that virulent strains ofM. aviumresist the antimicrobial mechanisms of IFN-γ-activated macrophages and raise the possibility that a second, T-cell-dependent signal is required for the effective control of mycobacterial replication inside macrophages.