Immobilized stem–loop structured probes as conformational switches for enzymatic detection of microbial 16S rRNA

We have designed and evaluated novel DNA stem–loop structured probes for enzymatic detection of nucleic acid targets. These probes constitute a novel class of conformational switches for enzymatic activity, which in the absence of a target sterically shield an affinity label and upon hybridization of the target to the recognition sequence that forms the loop of the probe restore accessibility of the label for the binding of a reporter enzyme. Analysis of probe characteristics revealed stem stability as the most important parameter governing detection functionality, while other factors such as the length of linker molecules attaching the label to the stem–loop structure and the nature of the solid support proved to be less critical. Apparently, the bulky nature of the reporter enzyme facilitates shielding of the label in the absence of the target, thereby conferring considerable structural tolerance to the conformational switch system. The stem–loop structured probes allow sensitive detection of unlabeled nucleic acid targets. Employing a microtiter assay format, 4 ng of bacterial 16S ribosomal RNA corresponding to 8 fmol could be detected, which can be compared favorably with current immobilized molecular beacon concepts based on fluorescence detection

Recombinant phospholipase A1 (Ves v 1) from yellow jacket venom for improved diagnosis of hymenoptera venom hypersensitivity

<p>Abstract</p> <p>Background</p> <p>Hymenoptera venoms are known to cause life-threatening IgE-mediated anaphylactic reactions in allergic individuals. Proper diagnosis of hymenoptera venom allergy using venom extracts is severely affected by molecular cross-reactivities. Although non-glycosylated marker allergens would facilitate the identification of the culprit venom, the major allergen phospholipase A1 (Ves v 1) from yellow jacket venom (YJV) remained unavailable so far.</p> <p>Methods</p> <p>Expression of Ves v 1 as wild type and enzymatically inactivated mutant and Ves v 5 in insect cells yielded soluble proteins that were purified via affinity chromatography. Functionality of the recombinant allergens was assessed by enzymatic and biophysical analyses as well as basophil activation tests. Diagnostic relevance was addressed by ELISA-based analyses of sera of YJV-sensitized patients.</p> <p>Results</p> <p>Both major allergens Ves v 1 and Ves v 5 could be produced in insect cells in secreted soluble form. The recombinant proteins exhibited their particular biochemical and functional characteristics and were capable for activation of human basophils. Assessment of IgE reactivity of sera of YJV-sensitized and double-sensitized patients emphasised the relevance of Ves v 1 in hymenoptera venom allergy. In contrast to the use of singular molecules the combined use of both molecules enabled a reliable assignment of sensitisation to YJV for more than 90% of double-sensitised patients.</p> <p>Conclusions</p> <p>The recombinant availability of Ves v 1 from yellow jacket venom will contribute to a more detailed understanding of the molecular and allergological mechanisms of insect venoms and may provide a valuable tool for diagnostic and therapeutic approaches in hymenoptera venom allergy.</p

Component resolution reveals additional major allergens in patients with honeybee venom allergy

BackgroundDetection of IgE to recombinant Hymenoptera venom allergens has been suggested to improve the diagnostic precision in Hymenoptera venom allergy. However, the frequency of sensitization to the only available recombinant honeybee venom (HBV) allergen, rApi m 1, in patients with HBV allergy is limited, suggesting that additional HBV allergens might be of relevance.ObjectiveWe performed an analysis of sensitization profiles of patients with HBV allergy to a panel of HBV allergens.MethodsDiagnosis of HBV allergy (n = 144) was based on history, skin test results, and allergen-specific IgE levels to HBV. IgE reactivity to 6 HBV allergens devoid of cross-reactive carbohydrate determinants (CCD) was analyzed by ImmunoCAP.ResultsIgE reactivity to rApi m 1, rApi m 2, rApi m 3, nApi m 4, rApi m 5, and rApi m 10 was detected in 72.2%, 47.9%, 50.0%, 22.9%, 58.3%, and 61.8% of the patients with HBV allergy, respectively. Positive results to at least 1 HBV allergen were detected in 94.4%. IgE reactivity to Api m 3, Api m 10, or both was detected in 68.0% and represented the only HBV allergen–specific IgE in 5% of the patients. Limited inhibition of IgE binding by therapeutic HBV and limited induction of Api m 3– and Api m 10–specific IgG4 in patients obtaining immunotherapy supports recent reports on the underrepresentation of these allergens in therapeutic HBV preparations.ConclusionAnalysis of a panel of CCD-free HBV allergens improved diagnostic sensitivity compared with use of rApi m 1 alone, identified additional major allergens, and revealed sensitizations to allergens that have been reported to be absent or underrepresented in therapeutic HBV preparations

Stereotypical Chronic Lymphocytic Leukemia B-Cell Receptors Recognize Survival Promoting Antigens on Stromal Cells

Chronic lymphocytic leukemia (CLL) is the most common leukemia in the Western world. Survival of CLL cells depends on their close contact with stromal cells in lymphatic tissues, bone marrow and blood. This microenvironmental regulation of CLL cell survival involves the stromal secretion of chemo- and cytokines as well as the expression of adhesion molecules. Since CLL survival may also be driven by antigenic stimulation through the B-cell antigen receptor (BCR), we explored the hypothesis that these processes may be linked to each other. We tested if stromal cells could serve as an antigen reservoir for CLL cells, thus promoting CLL cell survival by stimulation through the BCR. As a proof of principle, we found that two CLL BCRs with a common stereotyped heavy chain complementarity-determining region 3 (previously characterized as “subset 1”) recognize antigens highly expressed in stromal cells – vimentin and calreticulin. Both antigens are well-documented targets of autoantibodies in autoimmune disorders. We demonstrated that vimentin is displayed on the surface of viable stromal cells and that it is present and bound by the stereotyped CLL BCR in CLL-stroma co-culture supernatant. Blocking the vimentin antigen by recombinant soluble CLL BCR under CLL-stromal cell co-culture conditions reduces stroma-mediated anti-apoptotic effects by 20–45%. We therefore conclude that CLL BCR stimulation by stroma-derived antigens can contribute to the protective effect that the stroma exerts on CLL cells. This finding sheds a new light on the understanding of the pathobiology of this so far mostly incurable disease

Component resolved diagnostics for hymenoptera venom allergy.

PURPOSE OF REVIEW Component-resolved diagnostics makes use of defined allergen molecules to analyse IgE-mediated sensitizations at a molecular level. Here, we review recent studies on the use of component-resolved diagnostics in the field of Hymenoptera venom allergy (HVA) and discuss its benefits and limitations. RECENT FINDINGS Component resolution in HVA has moved from single molecules to panels of allergens. Detection of specific immunoglobulin E (sIgE) to marker and cross-reactive venom allergens has been reported to facilitate the discrimination between primary sensitization and cross-reactivity and thus, to provide a better rationale for prescribing venom immunotherapy (VIT), particularly in patients sensitized to both honeybee and vespid venom. Characterization of IgE reactivity to a broad panel of venom allergens has allowed the identification of different sensitization profiles that in honeybee venom allergy were associated with increased risks for side effects or treatment failure of VIT. In contrast, component resolution so far has failed to provide reliable markers for the discrimination of sensitizations to venoms of different members of Vespidae. SUMMARY Component-resolved diagnostics allows a better understanding of the complexity of sensitization and cross-reactivities in HVA. In addition, the enhanced resolution and precision may allow identification of biomarkers, which can be used for risk stratification in VIT. Knowledge about the molecular composition of different therapeutic preparations may enable the selection of appropriate preparations for VIT according to individual sensitization profiles, an approach consistent with the goals of personalized medicine

Complement Inactivation by Recombinant Human C3 Derivatives

From the implications of the complement system in a large number of diseases, an urgent need for therapeutics effecting reduced complement activity in vivo has emerged. In this study we report the design of a novel class of enzymes of human origin that obliterate functional complement by a noninhibitory, catalytic mechanism. Combining the framework of human C3 and the enzymatic mechanism of cobra venom factor, a nontoxic snake venom protein, we established molecules capable of forming stable C3 convertase complexes. Although the half-life of naturally occurring C3 convertase complexes ranges between 1 and 2 min, these complexes exhibit a half-life of up to several hours. Because the overall identity to human C3 could be extended to >90%, the novel C3 derivatives can be assumed to exhibit low immunogenicity and, therefore, represent promising candidates for therapeutic reduction of complement activity in vivo.PeerReviewe

Structure of linker molecules employed for biotin attachment to the stem–loop structures

<p><b>Copyright information:</b></p><p>Taken from "Immobilized stem–loop structured probes as conformational switches for enzymatic detection of microbial 16S rRNA"</p><p>Nucleic Acids Research 2005;33(11):e101-e101.</p><p>Published online 24 Jun 2005</p><p>PMCID:PMC1159122.</p><p>© The Author 2005. Published by Oxford University Press. All rights reserved</p> ARP-biotin [-(aminooxyacetyl)--(-biotinoyl)hydrazine] is attached via Schiff base chemistry to an aldehyde group generated by oxidative cleavage of the terminal ribose moiety of cytidin (rC). C3-Biotin contains a C3-ether-glycerol linker attached to the biotin residue via an amide bond. In TEG-biotin, the C3-ether-glycerol linker is extended by a triethyleneglycol (TEG) moiety