Characterization of the poliovirus 147S particle: new insights into poliovirus uncoating

A Sabin 1 strain poliovirus (PV) mutant, S1(2Y-1I), carrying a Tyr at amino acid position VP2(142) and an Ile at position VP1(160), can establish persistent infections in HEp-2c cells. This mutant forms atypical 147S particles upon interaction at 0 degrees C with either cells expressing PV receptor (PVR) CD155, or PVR-IgG2a, a chimeric molecule consisting of an extracellular moiety of PVR and the hinge and Fc portion of a mouse IgG2a. Upon interaction with PVR at 37 degrees C, S1(2Y-1I), similar to the parental strain, forms both 135S A particles and 80S empty capsids. At 0 degrees C, surprisingly, at a concentration equal to or greater than 5 nM, PVR-IgG2a induced both the extrusion of VP4 from the capsid of S1(2Y-1I) and the formation of 80S particles. The same transitions were observed at 0 degrees C with the parental strain Sabin 1 at 40 nM PVR-IgG2a. Thus, the formation of 80S particles and VP4 extrusion, considered as one of the steps of PV uncoating, can be temperature-independent at high PVR concentration. This implies that structural changes of the PV capsid occurred following adsorption at low temperature.     

Escherichia coli strains from pregnant women and neonates: intraspecies genetic distribution and prevalence of virulence factors

To determine the extent to which the vagina, endocervix, and amniotic fluid screen the Escherichia coli strains responsible for neonatal infections, we studied the genetic relationships among 105 E. coli strains isolated from all of the ecosystems involved in this infectious process. Twenty-four strains were isolated from the intestinal flora, and 25 strains were isolated from the vaginas of pregnant women. Twenty-seven strains were isolated from the amniotic fluid, blood, and cerebrospinal fluid (CSF) of infected neonates. The intraspecies genetic characteristics of all of the isolates were determined by random amplified polymorphic DNA (RAPD) analysis, PCR ECOR (E. coli reference) grouping, and PCR virulence genotyping. A correlation was found between the intraspecies distributions of the strains in the A, B1, B2, and D ECOR groups and in the two major RAPD groups (I and II). Nevertheless, the distribution of the E. coli strains in the RAPD groups according to their anatomical origins was more significant than their distribution in the ECOR groups. This may be explained by the existence of an E. coli subpopulation, defined by the RAPD I group, within the ECOR B2 group. This RAPD I group presents a major risk for neonates: 75% of the strains isolated from patients with meningitis and 100% of the strains isolated from patients with bacteremia were in this group. The vagina and the amniotic fluid are two barriers that favor colonization by highly infectious strains. Indeed, only 17% of fecal strains belonged to the RAPD I group, whereas 52% of vaginal strains and 67% of amniotic fluid strains belonged to this subpopulation. The ibeA and iucC genes were significantly associated with CSF strains, whereas the hly and sfa/foc genes were more frequent in blood strains. These findings could serve as a basis for developing tools to recognize vaginal strains, which present a high risk for neonates, for use in prophylaxis programs.     

Detection of Pseudomonas aeruginosa producing metallo-beta-lactamases in a large centralized laboratory

Metallo-beta-lactamases (MBLs) have been increasingly recognized from clinical isolates worldwide, but the laboratory detection of these strains is not well defined. We report a study that developed an EDTA disk screen test and a molecular diagnostic assay for the detection of MBL-producing Pseudomonas aeruginosa. Using NCCLS disk methodology, inhibition zone diameters were determined in tests with imipenem (IPM) and meropenem (MEM) disks alone and in combination with 930 microg of EDTA. This test was compared with the MBL Etest. The duplex PCR assay showed 100% sensitivity and specificity for detecting MBL-producing control strains. Of the 241 clinical strains of IPM-nonsusceptible P. aeruginosa from the Calgary Health Region isolated from 2002 to 2004, 110/241 (46%) were MBL positive using phenotypic methods while 107/241 (45%) were PCR positive for MBL genes: 103/241 (43%) for bla(VIM) and 4/241 (2%) for bla(IMP). The EDTA disk screen test using MEM showed 100% sensitivity and 97% specificity for detecting MBLs in control and clinical strains. The EDTA disk screen test is simple to perform and to interpret and can easily be introduced into the workflow of a clinical laboratory. We recommend that all IPM-nonsusceptible P. aeruginosa isolates be routinely screened for MBL production using the EDTA disk screen test and that PCR confirmation be performed at a regional laboratory.     

Mapping of B-Cell Epitopes in a Trypanosoma cruzi Immunodominant Antigen Expressed in Natural Infections

Tc40 is an immunodominant antigen present in natural Trypanosoma cruzi infections. This immunogen was thoroughly mapped by using overlapping amino acid sequences identified by gene cloning and chemical peptide synthesis. To map continuous epitopes of the Tc40 antigen, an epitope expression library was constructed and screened with sera from human chagasic patients. A major, linear B-cell epitope spanning residues 403 to 426 (PAKAAAPPAA) was identified in the central domain of Tc40. A synthetic peptide spanning this region reacted strongly with 89.8% of the serum samples from T. cruzi-infected individuals. This indicates that the main antigenic site is defined by the linear sequence of the peptide rather than a conformation-dependent structure. The major B-cell epitope of Tc40 shares a high degree of sequence identity with T. cruzi ribosomal and RNA binding proteins, suggesting the existence of cross-reactivity among these molecules.     

Absence of proteinase-activated receptor-1 signaling affords protection from bleomycin-induced lung inflammation and fibrosis

Activation of the coagulation cascade is commonly observed in the lungs of patients with both acute and chronic inflammatory and fibrotic lung disorders, as well as in animal models of these disorders. The aim of this study was to examine the contribution of the major thrombin receptor, proteinase-activated receptor-1 (PAR-1), during the acute inflammatory and chronic fibrotic phases of lung injury induced by intratracheal instillation of bleomycin in mice. Inflammatory cell recruitment and increases in bronchoalveolar lavage fluid (BALF) protein were attenuated by 56 +/- 10% (P < 0.05) and 53 +/- 12% (P < 0.05), respectively, in PAR-1-deficient (PAR-1-/-) mice compared with wild-type (WT) mice. PAR-1-/- mice were also protected from bleomycin-induced pulmonary fibrosis with total lung collagen accumulation reduced by 59 +/- 5% (P < 0.05). The protection afforded by PAR-1 deficiency was accompanied by significant reductions in pulmonary levels of the potent PAR-1-inducible proinflammatory and profibrotic mediators, monocyte chemoattractant protein-1 (MCP-1), transforming growth factor-beta-1 (TGF-beta1), and connective tissue growth factor/fibroblast-inducible secreted protein-12 (CTGF/FISP12). In addition, PAR-1 was highly expressed in inflammatory and fibroproliferative lesions in lung sections obtained from patients with fibrotic lung disease. These data show for the first time that PAR-1 signaling plays a key role in experimentally induced lung injury, and they further identify PAR-1 as one of the critical receptors involved in orchestrating the interplay between coagulation, inflammation, and remodeling in response to tissue injury.     

Autoantibodies directed against the amino-terminal domain I of human calpastatin (ACAST-DI Ab) in connective tissue diseases. High levels of ACAST-DI Ab are associated with vasculitis in lupus

To identify new autoantibody populations in patients with rheumatic diseases, a cDNA expression library was immunoscreened with a rheumatoid arthritis (RA) patient's serum which contains autoantibodies binding to uncharacterized polypeptides by Western-blotting. One clone encoding the amino-terminal region (Nt) [domain L and half of domain I] of human calpastatin was selected. Different fragments of the selected cDNA were prepared and the corresponding recombinant polypeptides were produced by in vitro translation and analysed by Western blotting. Most RA sera bound to recombinant amino-terminal region and domain I but not to domain L. This prompted us to use a recombinant polypeptide corresponding to the domain I of calpastatin as the antigen in a solid-phase ELISA to test sera from patients with various systemic rheumatic diseases and healthy controls.Anti-calpastatin domain I antibodies (ACAST-DI Ab), were detected by ELISA in RA, systemic lupus erythematosus (SLE), Sj?gren's syndrome and control sera at respective frequencies of 10, 9, 0 and 1%. These Ab did not have prognostic value in early RA; high levels were significantly associated with vasculitis in SLE. Antibodies reacting with the calpastatin amino-terminal region are produced during systemic rheumatic diseases and are predominantly directed against domain I. High levels of these Ab may constitute a marker of vasculitis in SLE.     

Towards immunotherapy for peanut allergy

PURPOSE OF REVIEW: Food allergy is a major cause of life-threatening hypersensitivity reactions. Peanut allergy is the most serious of the hypersensitivity reactions to foods due to its persistence and high risk of severe anaphylaxis. Currently, strict avoidance of the allergenic food and ready access to self-injectable epinephrine is the 'standard of care' for food allergy. Based on extensive characterization of food allergens and a better understanding of the immunological mechanisms underlying allergic disease, promising therapeutic modalities for food allergy treatment and prevention are being developed. RECENT FINDINGS: Immunotherapeutic strategies include peptide immunotherapy, mutated protein immunotherapy and DNA immunization, which all strive to decrease the deleterious Th2 response. Another approach already in clinical trials for peanut allergy is the anti-IgE therapy which prevents circulating IgE from binding to effector cells, consequently decreasing clinical symptoms after peanut ingestion. In order to be applicable, these strategies must be well tolerated, inexpensive and easily administered. Realistic treatment options would likely involve a combination of different approaches. SUMMARY: Food allergy affects approximately 4-6% of children and 3-4% of adults. Peanut allergy can be devastating as reactions range from urticaria to severe anaphylactic shock and death. The only preventive measure for peanut allergy is strict avoidance of the incriminating food. It is likely immunotherapy will be available in the near future as a well tolerated and effective therapy for treating peanut allergy. The use of the anti-IgE therapy in conjunction with other immunotherapy would possibly be the best treatment option in the future.