Two-Allergen Model Reveals Complex Relationship between IgE Crosslinking and Degranulation

SummaryAllergy is an immune response to complex mixtures of multiple allergens, yet current models use a single synthetic allergen. Multiple allergens were modeled using two well-defined tetravalent allergens, each specific for a distinct IgE, thus enabling a systematic approach to evaluate the effect of each allergen and percentage of allergen-specific IgE on mast cell degranulation. We found the overall degranulation response caused by two allergens is additive for low allergen concentrations or low percent specific IgE, does not change for moderate allergen concentrations with moderate to high percent specific IgE, and is reduced for high allergen concentrations with moderate to high percent specific IgE. These results provide further evidence that supraoptimal IgE crosslinking decreases the degranulation response and establishes the two-allergen model as a relevant experimental system to elucidate mast cell degranulation mechanisms

Inhibition of weak-affinity epitope-IgE interactions prevents mast cell degranulation

Development of specific inhibitors of allergy has had limited success, in part, owing to a lack of experimental models that reflect the complexity of allergen-IgE interactions. We designed a heterotetravalent allergen (HtTA) system, which reflects epitope heterogeneity, polyclonal response and number of immunodominant epitopes observed in natural allergens, thereby providing a physiologically relevant experimental model to study mast cell degranulation. The HtTA design revealed the importance of weak-affinity epitopes in allergy, particularly when presented with high-affinity epitopes. The effect of selective inhibition of weak-affinity epitope-IgE interactions was investigated with heterobivalent inhibitors (HBIs) designed to simultaneously target the antigen- and nucleotide-binding sites on the IgE Fab. HBI demonstrated enhanced avidity for the target IgE and was a potent inhibitor of degranulation in vitro and in vivo. These results demonstrate that partial inhibition of allergen-IgE interactions was sufficient to prevent mast cell degranulation, thus establishing the therapeutic potential of the HBI design

Эффективность использования игры скрэбл (Scrabble) для закрепления лексики (английский язык, технический вуз)

Rhodobacter capsulatus was used for the phototrophic hydrogen production on effluent solution derived from the thermophilic fermentation of Miscanthus hydrolysate by Thermotoga neapolitana. Pretreatments such as centrifugation, dilution, buffer addition, pH adjustment and sterilization were suggested for the effluent before being fed to the photofermentation. Batch-wise experiments showed that R. capsulatus grows and produces hydrogen on the pretreated effluent solution. Moreover, it was found that the hydrogen yield increased from 0.3 to 1.0 L/L-culture by addition of iron to the effluent solution

A heterobivalent ligand inhibits mast cell degranulation via selective inhibition of allergen-IgE interactions in vivo

Current treatments for allergies include epinephrine and antihistamines, which treat the symptoms after an allergic response has taken place; steroids, which result in local and systemic immune suppression; and IgE-depleting therapies, which can be used only for a narrow range of clinical IgE titers. The limitations of current treatments motivated the design of a heterobivalent inhibitor (HBI) of IgE-mediated allergic responses that selectively inhibits allergen-IgE interactions, thereby preventing IgE clustering and mast cell degranulation. The HBI was designed to simultaneously target the allergen binding site and the adjacent conserved nucleotide binding site (NBS) found on the Fab of IgE Abs. The bivalent targeting was accomplished by linking a hapten to an NBS ligand with an ethylene glycol linker. The hapten moiety of HBI enables selective targeting of a specific IgE, whereas the NBS ligand enhances avidity for the IgE. Simultaneous bivalent binding to both sites provided HBI with 120-fold enhancement in avidity for the target IgE compared with the monovalent hapten. The increased avidity for IgE made HBI a potent inhibitor of mast cell degranulation in the rat basophilic leukemia mast cell model, in the passive cutaneous anaphylaxis mouse model of allergy, and in mice sensitized to the model allergen. In addition, HBI did not have any observable systemic toxic effects even at elevated doses. Taken together, these results establish the HBI design as a broadly applicable platform with therapeutic potential for the targeted and selective inhibition of IgE-mediated allergic responses, including food, environmental, and drug allergies

Neutralizing positive charges at the surface of a protein lowers its rate of amide hydrogen exchange without altering its structure or increasing its thermostability

This paper combines two techniques—mass spectrometry and protein charge ladders—to examine the relationship between the surface charge and hydrophobicity of a protein (bovine carbonic anhydrase II; BCA II) and its rate of amide hydrogen-deuterium (H/D) exchange. Mass spectrometric analysis indicated that the sequential acetylation of surface lysine-$\epsilon$-NH$_{3}$$^{+}$ groups—a type of modification that increases the net negative charge and hydrophobicity of the surface of BCA II without affecting its 2° or 3° structure—resulted in a linear increase in the total number of backbone amide hydrogen that are protected from exchange with solvent (2 h, pD 7.4, 15 ºC). Each successive acetylation produced BCA II proteins with one additional hydrogen protected after two hours in deuterated buffer (pD 7.4, 15 ºC). NMR spectroscopy demonstrated that these protected hydrogen atoms were not located on the side chain of the acetylated lysine residues (i.e., lys-$\epsilon$-NHCOCH$_{3}$). The decrease in rate of exchange associated with acetylation paralleled a decrease in thermostability: the most slowly exchanging rungs were the least thermostable (as measured by differential scanning calorimetry). The fact that the rates of H/D exchange were similar for perbutyrated BCA II (e.g., [lys-$\epsilon$-NHCO(CH$_{2}$)$_{2}$CH$_{3}$]$_{18}$) and peracetylated BCA II (e.g., [lys-$\epsilon$-NHCOCH$_{3}$]$_{18}$) suggests that the charge is more important than the hydrophobicity of surface groups in determining the rate of H/D exchange. These kinetic electrostatic effects could complicate the interpretation of experiments in which H/D exchange methods are used to probe the structural effects of non-isoelectric perturbations to proteins (i.e., phosphorylation, acetylation, or the binding of the protein to an oligonucleotide or another charged ligand or protein).Chemistry and Chemical Biolog