bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cytoadherence of
Babesia bovis
-Infected Erythrocytes to Bovine Brain Capillary Endothelial Cells Provides an In Vitro Model for Sequestration
Authors: O’Connor Roberta M. , Long Jennifer A. , Allred David R. 
Published: December 2019

ABSTRACT

Babesia bovis
, an intraerythrocytic parasite of cattle, is sequestered in the host microvasculature, a behavior associated with cerebral and vascular complications of this disease. Despite the importance of this behavior to disease etiology, the underlying mechanisms have not yet been investigated. To study the components involved in sequestration,
B. bovis
parasites that induce adhesion of the infected erythrocytes (IRBCs) to bovine brain capillary endothelial cells (BBEC) in vitro were isolated. Two clonal lines, CD7
A+I+
and CE11
A+I−
, were derived from a cytoadherent, monoclonal antibody 4D9.1G1-reactive parasite population. This antibody recognizes a variant, surface-exposed epitope of the variant erythrocyte surface antigen 1 (VESA1) of
B. bovis
IRBCs. Both clonal lines were cytoadhesive to BBEC and two other bovine endothelial cell lines but not to COS7 cells, FBK-4 cells, C32 melanoma cells, or bovine brain pericytes. By transmission electron microscopy, IRBCs were observed to bind to BBEC via the knobby protrusions on the IRBC surface, indicating involvement of components associated with these structures. Inhibition of protein export in intact, trypsinized IRBCs ablated both erythrocyte surface reexpression of parasite protein and cytoadhesion. IRBCs allowed to recover surface antigen expression regained the ability to bind endothelial cells, demonstrating that parasite protein export is required for cytoadhesion. We propose the use of this assay as an in vitro model to study the components involved in
B. bovis
cytoadherence and sequestration.
A Random Survey of the
Cryptosporidium parvum
Genome
Authors: Liu Chang , Vigdorovich Vladimir , Kapur Vivek , Abrahamsen Mitchell S. 
Published: December 2019

ABSTRACT

Cryptosporidium parvum
is an obligate intracellular pathogen responsible for widespread infections in humans and animals. The inability to obtain purified samples of this organism’s various developmental stages has limited the understanding of the biochemical mechanisms important for
C. parvum
development or host-parasite interaction. To identify
C. parvum
genes independent of their developmental expression, a random sequence analysis of the 10.4-megabase genome of
C. parvum
was undertaken. Total genomic DNA was sheared by nebulization, and fragments between 800 and 1,500 bp were gel purified and cloned into a plasmid vector. A total of 442 clones were randomly selected and subjected to automated sequencing by using one or two primers flanking the cloning site. In this way, 654 genomic survey sequences (GSSs) were generated, corresponding to >320 kb of genomic sequence. These sequences were assembled into 408 contigs containing >250 kb of unique sequence, representing ∼2.5% of the
C. parvum
genome. Comparison of the GSSs with sequences in the public DNA and protein databases revealed that 107 contigs (26%) displayed similarity to previously identified proteins and rRNA and tRNA genes. These included putative genes involved in the glycolytic pathway, DNA, RNA, and protein metabolism, and signal transduction pathways. The repetitive sequence elements identified included a telomere-like sequence containing hexamer repeats, 57 microsatellite-like elements composed of dinucleotide or trinucleotide repeats, and a direct repeat sequence. This study demonstrates that large-scale genomic sequencing is an efficient approach to analyze the organizational characteristics and information content of the
C. parvum
genome.
Thymic Independence of Adaptive Immunity to the Intracellular PathogenShigella flexneriSerotype 2a
Authors: Way Sing Sing , Borczuk Alain C. , Goldberg Marcia B. 
Published: December 2019

ABSTRACTShigella flexneriis a facultative intracellular pathogen. While immunity to several intracellular pathogens is mediated by T lymphocytes, it is unknown whether cellular immune responses are important to adaptive immunity toS. flexneri. We show that vaccination withS. flexneriserotype 2a confers protection to mice that lack T lymphocytes or gamma interferon (IFN-γ), specific depletion of T lymphocytes does not alter the protection, and adoptive transfer of splenocytes from vaccinated mice does not confer protection to naive mice. In contrast, vaccination conferred no protection to mice that lack B lymphocytes and adoptive transfer of immune sera conferred partial protection to naive mice. These data demonstrate that in the mouse bronchopulmonary model, adaptive immunity toS. flexneri2a is an antibody-mediated, B-lymphocyte-dependent process and can be generated in the absence of T lymphocytes or IFN-γ.
New Exfoliative Toxin Produced by a Plasmid-Carrying Strain of
Staphylococcus hyicus
Authors: Sato Hisaaki , Watanabe Takao , Murata Yasuko , Ohtake Ayumi , Nakamura Mayumi , Aizawa Chikara , Saito Hiroshi , Maehara Nobutoshi 
Published: December 2019

ABSTRACT

A new serotype of
Staphylococcus hyicus
exfoliative toxin (SHET), serotype B, was isolated from the culture filtrate of a plasmid-carrying strain of
S. hyicus
. The new SHET was purified by precipitation with 70% saturated ammonium sulfate, gel filtration on a Sephadex G-75 column, column chromatography on DEAE–Cellulofine A-500, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The new SHET caused exfoliation of the epidermis as determined by the so-called Nikolsky sign when inoculated into 1-day-old chickens. The new SHET was serologically different from
Staphylococcus aureus
exfoliative toxins (ETs) (ETA, ETB, and ETC) and from the SHET from the plasmidless strain but showed the same molecular weight as the other serotypes of toxins on SDS-PAGE. It was thermolabile and lost its toxicity after being heated at 60°C for 30 min. We propose that the new SHET be designated SHETB and that the SHET produced by the plasmidless strain be designated SHETA.
Characterization of an Enterotoxigenic
Escherichia coli
Strain from Africa Expressing a Putative Colonization Factor
Authors: Khalil Sami B. , Cassels Frederick J. , Shaheen Hind I. , Pannell Lewis K. , El-Ghorab Nemat , Kamal Karim , Mansour Moustafa , Savarino Stephen J. , Peruski Leonard F. 
Published: December 2019

ABSTRACT

An enterotoxigenic
Escherichia coli
(ETEC) strain of serotype O114:H− that expressed both heat-labile and heat-stable enterotoxins and tested negative for colonization factors (CF) was isolated from a child with diarrhea in Egypt. This strain, WS0115A, induced hemagglutination of bovine erythrocytes and adhered to the enterocyte-like cell line Caco-2, suggesting that it may elaborate novel fimbriae. Surface-expressed antigen purified by differential ammonium sulfate precipitation and column chromatography yielded a single protein band with
M
r
14,800 when resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (16% polyacrylamide). A monoclonal antibody against this putative fimbrial antigen was generated and reacted with strain WS0115A and also with CS1-, CS17-, and CS19-positive strains in a dot blot assay. Reactivity was temperature dependent, with cells displaying reactivity when grown at 37°C but not when grown at 22°C. Immunoblot analysis of a fimbrial preparation from strain WS0115A showed that the monoclonal antibody reacted with a single protein band. Electron microscopy and immunoelectron microscopy revealed fimbria-like structures on the surface of strain WS0115A. These structures were rigid and measured 6.8 to 7.4 nm in diameter. Electrospray mass-spectrometric analysis showed that the mass of the purified fimbria was 14,965 Da. The N-terminal sequence of the fimbria established that it was a member of the CFA/I family, with sequence identity to the amino terminus of CS19, a new CF recently identified in India. Cumulatively, our results suggest that this fimbria is CS19. Screening of a collection of ETEC strains isolated from children with diarrhea in Egypt found that 4.2% of strains originally reported as CF negative were positive for this CF, suggesting that it is biologically relevant in the pathogenesis of ETEC.
A Murine Model for Infection withBurkholderia cepaciawith Sustained Persistence in the Spleen
Authors: Speert David P. , Steen Barbara , Halsey Keith , Kwan Eddie 
Published: December 2019

ABSTRACTBurkholderia cepaciais an opportunistic pathogen that causes severe systemic infections in patients with chronic granulomatous disease (CGD) or with cystic fibrosis (CF), but its mechanisms of virulence are poorly understood. We developed a murine model of systemic infection in wild-type (WT) and gamma interferon knockout (GKO) BALB/c mice to facilitate dissection of components of pathogenicity and host defense. Both WT and GKO mice were susceptible to chronic splenic infection withB. cepacia, but not withPseudomonas aeruginosa. B. cepaciastrains from patients with CGD persisted longer than those from CF patients. C57BL/6 mice were the most susceptible murine strain; bacteria persisted in the spleen for 2 months. DBA/2, BALB/c, and A/J strains of mice were relatively resistant to infection. Certain strains ofB. cepaciacomplex can persist in the murine spleen after systemic infection; this may provide clues to its virulence in compromised hosts, such as those with CGD and CF.
TheTreponema denticolaMajor Sheath Protein Is Predominantly Periplasmic and Has Only Limited Surface Exposure
Authors: Caimano Melissa J. , Bourell Kenneth W. , Bannister Teresa D. , Cox David L. , Radolf Justin D. 
Published: December 2019

ABSTRACTThe recent discovery that theTreponema pallidumgenome encodes 12 orthologs of theTreponema denticolamajor sheath protein (Msp) prompted us to reexamine the cellular location and topology of theT. denticolapolypeptide. Experiments initially were conducted to ascertain whether Msp forms an array on or within theT. denticolaouter membrane. Transmission electron microscopy (EM) of negatively stained and ultrathin-sectioned organisms failed to identify a typical surface layer, whereas freeze-fracture EM revealed that theT. denticolaouter membrane contains heterogeneous transmembrane proteins but no array. In contrast, a lattice-like structure was observed in vesicles released from mildly sonicated treponemes; combined EM and biochemical analyses demonstrated that this structure was the peptidoglycan sacculus. Immunoelectron microscopy (IEM) subsequently was performed to localize Msp inT. denticola. Examination of negatively stained whole mounts identified substantial amounts of Msp in sonicated organisms. IEM of ultrathin-sectioned, intact treponemes also demonstrated that the preponderance of antigen was unassociated with the outer membrane. Lastly, immunofluorescence analysis of treponemes embedded in agarose gel microdroplets revealed that only minor portions of Msp are surface exposed. Taken as a whole, our findings challenge the widely held belief that Msp forms an array within theT. denticolaouter membrane and demonstrate, instead, that it is predominantly periplasmic with only limited surface exposure. These findings also have implications for our evolving understanding of the contribution(s) of Msp/Tpr orthologs to treponemal physiology and disease pathogenesis.
Differential Regulation ofSalmonella typhimuriumType III Secreted Proteins by Pathogenicity Island 1 (SPI-1)-Encoded Transcriptional Activators InvF and HilA
Authors: Eichelberg Katrin , Galán Jorge E. 
Published: December 2019

ABSTRACTSalmonella entericaencodes a type III protein secretion system within a pathogenicity island (SPI-1) that is located at centisome 63 of its chromosome. This system is required for the ability of these bacteria to stimulate cellular responses that are essential for their pathogenicity. Expression of components and substrates of this system is subject to complex regulatory mechanisms. These mechanisms involve the function of HilA and InvF, two transcriptional regulatory proteins encoded within SPI-1. In this study, we examined the functional relationship between these two regulatory proteins. We found that strains carrying loss-of-function mutations in eitherhilAorinvFdiffer in their ability to stimulate cellular responses. AnS. typhimurium hilAmutant strain retained considerable signaling capacity that resulted in significant levels of internalization into host cells. In contrast, introduction of a nonpolar loss-of-function mutation ininvFrenderedS. typhimuriumsignificantly impaired in its ability to enter host cells. Consistent with these different phenotypes, we found that HilA and InvF control the expression of different genes. HilA regulates the expression of components of the type III secretion machinery, whereas InvF controls the expression of type III secreted proteins encoded outside of SPI-1. We also found that the expression of secreted proteins encoded within SPI-1 are under the control of both HilA and InvF. Our results therefore indicate that InvF and HilA differentially control the expression of components and substrates of the invasion-associated type III secretion system.
Intranasal Immunization with Pneumococcal Polysaccharide Conjugate Vaccines Protects Mice against Invasive Pneumococcal Infections
Authors: Jakobsen Håvard , Saeland Eiríkur , Gizurarson Sveinbjörn , Schulz Dominique , Jónsdóttir Ingileif 
Published: December 2019

ABSTRACT

Host defenses against
Streptococcus pneumoniae
depend largely on opsonophagocytosis mediated by antibodies and complement. Since pneumococcus is a respiratory pathogen, mucosal immune responses may play a significant role in the defense against pneumococcal infections. Thus, mucosal vaccination may be an alternative approach to current immunization strategies, but effective adjuvants are required. Protein antigens induce significant mucosal immunoglobulin A (IgA) and systemic IgG responses when administered intranasally (i.n.) with the glyceride-polysorbate based adjuvant RhinoVax (RV) both in experimental animals and humans. The immunogenicity and efficacy of pneumococcal polysaccharide conjugate vaccines (PNC) of serotypes 1 and 3 was studied in mice after i.n. immunization with RV. Antibodies were measured in serum (IgM, IgG, and IgA) and saliva (IgA) and compared to antibody titers induced by parenteral immunization. The PNCs induced significant systemic IgG and IgA antibodies after i.n. immunization only when given with RV and, for serotype 1, serum IgG titers were comparable to titers induced by subcutaneous immunization. In addition, i.n. immunization with PNC-1 in RV elicited detectable mucosal IgA. These results demonstrate that RV is a potent mucosal adjuvant for polysaccharides conjugated to proteins. A majority of the PNC-1-immunized mice were protected against both bacteremia and pneumonia after i.n. challenge with a lethal dose of serotype 1 pneumococci, and protection correlated significantly with the serum IgG titers. Similarly, the survival of mice immunized i.n. with PNC-3 in RV was significantly prolonged. These results indicate that mucosal vaccination with PNC and adjuvants may be an alternative strategy for prevention against pneumococcal infections.
Elevated Chemokine Concentrations in Sera of Human Immunodeficiency Virus (HIV)-Seropositive and HIV-Seronegative Patients with Tuberculosis: a Possible Role for Mycobacterial Lipoarabinomannan
Authors: Juffermans Nicole P. , Verbon Annelies , van Deventer Sander J. H. , van Deutekom Henk , Belisle John T. , Ellis Michael E. , Speelman Peter , van der Poll Tom 
Published: December 2019

ABSTRACTLevels of interleukin 8 (IL-8), gamma interferon-inducible protein 10 (IP-10), monocyte chemoattractant protein 1 (MCP-1), and macrophage inflammatory protein 1β (MIP-1β) were elevated in patients with tuberculosis. IP-10 and MCP-1 levels were higher in human immunodeficiency virus (HIV)-seropositive patients than in HIV-seronegative patients with tuberculosis. Lipoarabinomannan induced IL-8, MCP-1, and MIP-1β in vitro, which was partly inhibited by anti-tumor necrosis factor antibody.
Iron Modulates Phenotypic Variation and Phosphorylation of P270 in Double-Stranded RNA Virus-Infected
Trichomonas vaginalis
Authors: Alderete J. F. 
Published: December 2019

ABSTRACT

Trichomonas vaginalis
infected with a double-stranded RNA virus undergoes phenotypic variation on the basis of surface versus cytoplasmic expression of the immunogenic protein P270. Examination of batch cultures by flow cytofluorometry with monoclonal antibody (MAb) to P270 yields both fluorescent and nonfluorescent trichomonads. Greater numbers and intensity of fluorescent organisms with surface P270 reactive with MAb were evident in parasites grown in medium depleted of iron. Placement of iron-limited organisms in medium supplemented with iron gave increased numbers of nonfluorescent trichomonads. Purified subpopulations of trichomonads with and without surface P270 obtained by fluorescence-activated cell sorting reverted to nonfluorescent and fluorescent phenotypes when placed in high- and low-iron media, respectively. No similar regulation by iron of P270 was evident among virus-negative
T. vaginalis
isolates or virus-negative progeny trichomonads derived from virus-infected isolates. Equal amounts of P270 were detectable by MAb on immunoblots of total proteins from identical numbers of parasites grown in low- and high-iron media. Finally, P270 was found to be highly phosphorylated in high-iron parasites. Iron, therefore, plays a role in modulating surface localization of P270 in virus-harboring parasites.
Intranasal Administration of Synthetic Recombinant Peptide-Based Vaccine Protects Mice from Infection bySchistosoma mansoni
Authors: Ben-Yedidia T. , Tarrab-Hazdai R. , Schechtman D. , Arnon R. 
Published: December 2019

ABSTRACTSchistosomiasis is the cause of a chronic debilitating disease which accounts for significant mortality and morbidity every year, especially in tropical and subtropical areas. An epitope derived from the protective surface protein 9B-Ag ofSchistosoma mansoni, designated 9B peptide-1, was previously showed to be protective in mice when conjugated to bovine serum albumin and administered subcutaneously in complete Freund’s adjuvant. In this work, this protective peptide was expressed in the flagellin of aSalmonellavaccine strain, and the isolated recombinant flagella were used for immunization of mice. Since during the invasion of the parasite into the host the schistosomula migrate first to the lungs, the intranasal route of administration was employed in order to halt the parasite at an early stage of the infection. Such intranasal immunization with this peptide expressed in flagellin, without the addition of adjuvants, resulted in a significant humoral response and also led to protection against challenge infection, manifested as a reduction of the worm burden by an average of 42%.
A Defect in Interleukin-10 Leads to Enhanced Malarial Disease inPlasmodium chabaudi chabaudiInfection in Mice
Authors: Li Ching , Corraliza Inés , Langhorne Jean 
Published: December 2019

ABSTRACTInfection of interleukin-10 (IL-10)-nonexpressing (IL-10−/−) mice withPlasmodium chabaudi chabaudi(AS) leads to exacerbated pathology in female mice and death in a proportion of them. Hypoglycemia, hypothermia, and loss in body weight were significantly greater in female IL-10−/−mice than in male knockout mice and all wild-type (WT) mice during the acute phase of infection. At this time, both female and male IL-10−/−mice produced more gamma interferon (IFN-γ), tumor necrosis factor alpha (TNF-α), and IL-12p40 mRNA than their respective WT counterparts. Inactivation of IFN-γ in IL-10−/−mice by the injection of anti-IFN-γ antibodies or by the generation of IL-10−/−IFN-γ receptor−/−double-knockout mice resulted in reduced mortality but did not affect body weight, temperature, or blood glucose levels. The data suggest that IFN-γ-independent pathways may be responsible for these pathological features ofP. chabaudimalaria and may be due to direct stimulation of TNF-α by the parasite. Since male and female knockout mice both produce more inflammatory cytokines than their WT counterparts, it is likely that the mortality seen in females is due to the nature or magnitude of the response to these cytokines rather than the amount of IFN-γ or TNF-α produced.
Reactivation of Latent Tuberculosis: Variations on the Cornell Murine Model
Authors: Scanga Charles A. , Mohan V. P. , Joseph Heather , Yu Keming , Chan John , Flynn JoAnne L. 
Published: December 2019

ABSTRACTMycobacterium tuberculosiscauses active tuberculosis in only a small percentage of infected persons. In most cases, the infection is clinically latent, although immunosuppression can cause reactivation of a latentM. tuberculosisinfection. Surprisingly little is known about the biology of the bacterium or the host during latency, and experimental studies on latent tuberculosis suffer from a lack of appropriate animal models. The Cornell model is a historical murine model of latent tuberculosis, in which mice infected withM. tuberculosisare treated with antibiotics (isoniazid and pyrazinamide), resulting in no detectable bacilli by organ culture. Reactivation of infection during this culture-negative state occurred spontaneously and following immunosuppression. In the present study, three variants of the Cornell model were evaluated for their utility in studies of latent and reactivated tuberculosis. The antibiotic regimen, inoculating dose, and antibiotic-free rest period prior to immunosuppression were varied. A variety of immunosuppressive agents, based on immunologic factors known to be important to control of acute infection, were used in attempts to reactivate the infection. Although reactivation of latent infection was observed in all three variants, these models were associated with characteristics that limit their experimental utility, including spontaneous reactivation, difficulties in inducing reactivation, and the generation of altered bacilli. The results from these studies demonstrate that the outcome of Cornell model-based studies depends critically upon the parameters used to establish the model.
Characterization of VspB of
Borrelia turicatae
, a Major Outer Membrane Protein Expressed in Blood and Tissues of Mice
Authors: Pennington Pamela M. , Cadavid Diego , Barbour Alan G. 
Published: December 2019

ABSTRACT

Serotypes A and B of the relapsing fever spirochete
Borrelia turicatae
produce different disease manifestations in infected mice. Whereas serotype B causes more severe arthritis and reaches higher densities in the blood of mice than serotype A, serotype A invades the central nervous system earlier than serotype B during infection. These differences between serotypes A and B in mice are associated with the expression of different surface proteins, VspA and VspB, respectively, in the culture medium. To determine whether these proteins, in particular, VspB, are also expressed in vivo,
scid
mice infected with
B. turicatae
were studied. The expression of VspB by spirochetes in the blood was demonstrated in Coomassie blue-stained polyacrylamide gels and Western blots with a specific monoclonal antibody. Indirect immunofluorescence and immunoperoxidase studies confirmed the expression of VspB in the blood and also demonstrated VspB expression in the joints and heart. The gene for VspB was next identified and cloned by using partial amino acid sequencing, reverse transcriptase PCR, and a specific monoclonal antibody. The
vspB
gene encodes a protein of 216 amino acids that is 68% identical to VspA of
B. turicatae
and 44 to 56% identical to representative Vsp and OspC lipoproteins of other
Borrelia
spp. The processed VspB protein was distinguished from 26 other Vsp and OspC proteins by a high predicted isoelectric point at 9.39. The promoter region for
vspB
was similar to the promoter region for the
vsp33
gene of
Borrelia hermsii
and for the
ospC
gene of
Borrelia burgdorferi
, two genes known to be environmentally regulated. These studies established that the virulence-associated VspB protein is expressed by spirochetes in the mouse and that VspB is a novel member of the Vsp-OspC family of proteins.