1,721,007 research outputs found
Identification of immunodominant epitopes in the filamentous hemagglutinin of Bordetella pertussis.
No full textThe filamentous hemagglutinin (FHA) of Bordetella pertussis is a principal adhesin, which plays a key role in the colonization of the upper respiratory tract. FHA is also a protective antigen, which has been incorporated in the new generation of acellular vaccines against whooping cough. The protein is synthesized as a large 367-kDa precursor, which is then processed into a 220-kDa secreted polypeptide. To optimize the use of this protein for vaccine purposes it would be helpful to define the regions encompassing immunodominant epitopes. Twelve recombinant plasmids have been generated encoding fusion proteins between fragments of the matured-secreted 220-kDa form of FHA and the vector-encoded phage MS2 polymerase. Protein extracts of the resulting recombinant clones have been tested for reactivity with sera from 20 patients convalescent from whooping cough, and two human standard sera. The results indicate the presence of an immunodominant B cell epitope in the polypeptide coded by a 1-kb DNA fragment encompassing positions 5781-6800 of the published sequence. These results suggest that the identified fragment should be conserved in the formulation of vaccines against pertussis
The inhibitory co-receptors: a way to save from anergy the HIV-specific T cells.
No full textThe functional impairment of HIV-specific CD4(+) T cells during chronic HIV infection is thought to be closely linked to viral replication and to T cell exhaustion. T cell exhaustion in the presence of ongoing antigen exposure is a common feature of chronic viral infection, in which dysfunctional T cells fail to eliminate the virus. Otherwise, antiviral T cell function impairment is a poorly understood mechanism. Increasing evidences show that HIV-specific T lymphocytes up-regulated inducible co-receptors, such as the Cytoxic T Lymphocyte Antigen-4, (CTLA-4, or CD152) and Programmed Death-1 (PD-1) and that blockade of the CD152 or PD-1 pathway restores HIV-specific CD4(+) T cell function in HIV infection. This review will focus on finding a possible role for inhibitory receptors on virus-specific CD4(+) T cells. The analysis of the role of CD152 and PD-1 in HIV-1 infection could provide important insight into the mechanism of viral induced immune dysfunction and lead to immunotherapeutic strategies to reverse immune suppression in this pathology
Cranberry polyphenols regulate in vitro human T cell responses induced by E.coli bacteria isolated from urinary infection.
No full textRapid method for identification of Staphylococcus aureus when both human and animal staphylococci are tested: comparison with a new immunoenzymatic assay.
No full textA new immunoenzymatic assay (IEA) for the identification of Staphylococcus aureus strains of both human and animal origin was compared with rapid commercial kits. The sensitivities and specificities of the commercial kits varied from 90.2 to 96% and 90.8 to 93.7%, respectively. The IEA did not give any false-negative or false-positive results, while commercial kits gave high percentages of false-positive results among clumping factor-positive non-S. aureus strains. The IEA is particularly useful for isolates for which identification is doubtful, for large-scale epidemiological studies, and for identifying isolates from animals as S. aureus
Virulence factors in urinary Escherichia coli strains: phylogenetic background and quinolone and fluoroquinolone resistance.
No full textQuinolone- and fluoroquinolone-resistant Escherichia coli strains harbor fewer virulence factors than susceptible strains. The reasons underlying this correlation are incompletely understood. We investigated the phylogenetic background, the presence of the papC, hlyA, and cnf1 (pathogenicity island II(J96)-associated), fimA, iss, and iutA genes, and the presence of type 1 fimbriae, P fimbriae, and hemolysin in 243 urinary E. coli isolates resistant only to quinolones (8%), resistant to both quinolones and fluoroquinolones (51%), or susceptible to both drugs (41%). Group B2 accounted for 56% of the isolates, showing a significantly higher prevalence among fluoroquinolone-susceptible strains than among resistant strains (65% versus 50% [P = 0.03]). hly and cnf1 were significantly more associated with susceptibility (P < 0.001) and with group B2 (P < 0.001 for group B2 versus groups A and D). However, within group B2, fluoroquinolone-resistant strains showed lower prevalences of papC, hlyA, and cnf1 than their susceptible counterparts (P < 0.001). In contrast, the incidence of iutA appeared higher for refractory isolates, including group B2, than for susceptible isolates (P < 0.001). Only in group B2 did fluoroquinolone-resistant strains reveal a lesser ability to agglutinate Saccharomyces cerevisiae (7%) than quinolone-resistant (87%) and susceptible (80%) isolates, despite uniform possession of fimA genes. No similar contrast emerged for expression of hemolysin and P fimbriae. Mutations conferring quinolone and fluoroquinolone resistance may thus require a particular genetic background, not strictly correlated with phylogenetic groups. More interestingly, the mutational event itself can affect the expression of type 1 fimbriae, at least in the prevalent and complex B2 strains
Rapid methods in S. aureus identification when both human and animal staphylococci are tested: comparison with a new immunoenzymatic assay.
No full textIdentification of Salmonella enterica Serovar Typhi DNA Fragments with Transcriptional Activity Under Different Growth Conditions.
No full textAbstract: Salmonella enterica serovar Typhi is a human pathogenic microorganism with a very complex infective cycle, involving the transit of bacteria across different microenvironments; to optimize the performance of attenuated Salmonella strains suitable as live carriers of heterologous antigens, fine tuning of wild type bacteria gene expression is essential. Several DNA fragments were obtained from a Salmonella enterica serovar Typhi (vi+, fim+) blood isolate and 18 clones were selected according to the dimension of the insert (range <0.2-1.6 kb). These fragments showed a transcriptional activity in a promoterless vector cloned in Escherichia coli background, according to homogeneous parameters. The results obtained provide an insight about signals mediating gene activation in vivo, particularly in the microenvironments known to exist during the infectious process, even if the fragments are not promoters sequences. Finally, the functional characterization of several fragments showed that they possessed an efficient and homogeneous transcriptional activity, worth to be further investigated
Synthesis, Characterization, and Bactericidal Activity of a 4-Ammoniumbuthylstyrene-Based Random Copolymer
No full textThe growing resistance of bacteria to current chemotherapy is a global concern that urgently requires new and effective antimicrobial agents, aimed at curing untreatable infection, reducing unacceptable healthcare costs and human mortality. Cationic polymers, that mimic antimicrobial cationic peptides, represent promising broad-spectrum agents, being less susceptible to develop resistance than low molecular weight antibiotics. We, thus, designed, and herein report, the synthesis and physicochemical characterization of a water-soluble cationic copolymer (P5), obtained by copolymerizing the laboratory-made monomer 4-ammoniumbuthylstyrene hydrochloride with di-methyl-acrylamide as uncharged diluent. The antibacterial activity of P5 was assessed against several multi-drug-resistant clinical isolates of both Gram-positive and Gram-negative species. Except for strains characterized by modifications of the membrane charge, most of the tested isolates were sensible to the new molecule. P5 showed remarkable antibacterial activity against several isolates of genera Enterococcus, Staphylococcus, Pseudomonas, Klebsiella, and against Escherichia coli, Acinetobacter baumannii and Stenotrophomonas maltophilia, displaying a minimum MIC value of 3.15 µM. In time-killing and turbidimetric studies, P5 displayed a rapid non-lytic bactericidal activity. Due to its water-solubility and wide bactericidal spectrum, P5 could represent a promising novel agent capable of overcoming severe infections sustained by bacteria resistant the presently available antibiotics
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