Aiming to IgE: Drug development in allergic diseases.

The incidence of allergic disease significantly increases in recent decades, causing it become a major public health problem all over the world. The common allergic diseases such as allergic dermatitis, allergy rhinitis, allergic asthma and food allergy are mediated, at least in part, by immunoglobulin E (IgE), and so IgE acts as a central role in allergic diseases. IgE can interact with its high-affinity receptor (FcεRⅠ) which is primarily expressed on tissue-resident mast cells and circulating basophils, initiating intracellular signal transduction and then causing the activation and degranulation of mast cells and basophils. On the other hand, IgE interaction with its low-affinity receptor (CD23), can regulate various IgE-mediated immune responses including IgE-allergen complex presentation, IgE synthesis, the growth and differentiation of both B and T cells, and the secretion of pro-inflammatory mediators. With the deeper mechanism research for allergic diseases, new therapeutic strategies for interfering IgE are developed and receive a great attention. In this review, we summarize a current profile of therapeutic strategies for interfering IgE in allergic diseases. Besides, we suggest that targeting memory B cells (including long-lived plasma cells and (or) IgE+ memory B cells) may help to completely control allergic diseases, and highlight that the development of drugs synergistically aiming to multiple targets can be a better choice for improving treatment efficacy which results from allergic diseases as the systemic disorders caused by an impaired immune system.

Colorimetric visualization of histamine secreted by basophils based on DSP-functionalized gold nanoparticles.

Histamine released by activated basophils has become an important biomarker and therapeutic target in the development of allergic diseases. To date, several gold nanoparticle (AuNP)-based nanosensors have been reported for histamine detection in foods. However, rapid, highly sensitive and direct detection of histamine in allergic diseases is still lacking due to the complexity of the physical environment. Herein, we developed a novel nanosensor for colorimetric visualization of histamine in activated basophils by simply coupling dithiobis(succinimidylpropionate) (DSP) on the surface of AuNPs (DSP-AuNPs). The DSP moiety serves as a linker and can react with the aliphatic amino group of histamine, and the imidazole ring of histamine can selectively bind with Au by means of p-p conjugation, thus inducing the aggregation of AuNPs. In this study, we experimentally proved that DSP-AuNPs showed good sensitivity and selectivity to histamine among various amino acids, including histidine. Additionally, this nanosensor displayed a rapid response to histamine with a linear range of 0.8-2.5 µM, and the limit of detection (LOD) was 0.014 µM, which is a relatively low LOD in comparison with those of other AuNP-based nanosensors. Finally, DSP-AuNPs are used, for the first time, to successfully detect endogenous histamine changes in activated basophils. Therefore, our work may provide a promising strategy to monitor histamine levels in the basophil activation test.

The development of a candidate of desensitization vaccines against Der f 2 nearly without IgE-binding activity.

Considering the important role of Der f 2 in house dust mites mediating allergic diseases and allergic adverse effects during allergen-specific immunotherapy (AIT), we intend to develop a candidate of desensitization vaccines against Der f 2 without allergenicity. According to the reported immunoglobulin E (IgE)-binding B and T cell epitopes of Der f 2, four candidates of desensitization vaccines against Der f 2 were developed. Recombinant wild-type Der f 2 (rWt-Der f 2) preserved conformational and linear IgE-binding B epitopes. rWt-Der f 2 linearized by reduction and alkylation reactions (rWt-Der f 2 (red/alk)) and recombinant modified-type Der f 2 (rMt-Der f 2) were developed via destroying conformational and linear IgE-binding B epitopes respectively. rMt-Der f 2 linearized by reduction and alkylation reactions (rMt-Der f 2 (red/alk)) was developed by destroying conformational and linear IgE-binding B epitopes. T cell epitopes of 4 candidates were preserved. The change of their IgE-binding activity was determined by enzyme linked immunosorbent assay (ELISA), western blot and inhibition ELISA. Compared with rWt-Der f 2, the IgE-binding activity of rWt-Der f 2 (red/alk), rMt-Der f 2 and rMt-Der f 2 (red/alk) all decreased, which was consistent with the result of western blot. The IgE-binding activity of rMt-Der f 2 and rMt-Der f 2 (red/alk) was not significantly different (P = 0.0863 > 0.05), which was comparable to that of their corresponding negative controls (P = 0.3488 and 0.4459, both > 0.05). The result of inhibition ELISA also showed that their IgE-binding activity decreased, and rMt-Der f 2 (red/alk) was the lowest. Conclusively, we developed the candidate of desensitization vaccines against Der f 2, rMt-Der f 2 or rMt-Der f 2 (red/alk), nearly without allergenicity, which would potentially prevent HDM allergic patients from allergic adverse effects caused by AIT.

A new cysteine protease allergen from Ambrosia trifida pollen: proforms and mature forms.

Giant ragweed (Ambrosia trifida) pollen is closely associated with respiratory allergy in late summer and autumn, and the prevalence of giant ragweed pollen allergy progressively increases. Compared with short ragweed (Ambrosia artemisiifolia), allergenic components from giant ragweed pollen are poorly investigated. To promote component-resolved diagnosis and treatment for giant ragweed pollen allergy, it becomes necessary to identify and characterize unknown allergens from giant ragweed pollen. In the present study, we identified and characterized a new cysteine-protease (CP) allergen from giant ragweed pollen, named as Amb t CP. The cloned Amb t CP gene encoded 387 amino acids. Recombinant Amb t CP (rAmb t CP) and natural Amb t CP (nAmb t CP) were purified by high-affinity Ni2+ resin and immunoaffinity chromatography respectively. During refolding, purified rAmb t CP could autocatalytically converted to its mature forms displaying a higher enzymatic activity. Moreover, the autocatalytic conversion of proforms to mature forms of nAmb t CP could cause their amount to change in giant ragweed pollen extracts. Then, the allergenicity of Amb t CP was characterized: 23 (33.8%) of 68 Chinese patients with ragweed pollen allergy showed positive IgE binding to nAmb t CP by enzyme-linked immunosorbent assay (ELISA); the result of subsequent ELISA showed that IgE-binding activity of proforms and mature forms of rAmb t CP was different, with positive rate of 39.1% (9/23) and 47.8% (11/23) respectively; Amb t CP showed IgE cross-reactivity with the CP components from short ragweed, Artemisia annua and Artemisia sieversiana pollen. Our findings will help to promote component-resolved diagnosis and treatment for giant ragweed pollen allergy, standardize allergen products and individualize allergen-specific immunotherapy.

Pyocyanin induces NK92 cell apoptosis via mitochondrial damage and elevated intracellular Ca2.

Pseudomonas aeruginosa-derived pigment pyocyanin (PCN) has been proved to induce cell apoptosis mediated by the generation of reactive oxygen species (ROS), which has been studied mainly in epithelial cells and neutrophils. However, we previously found that the PCN-producing strain PA14 induces cell apoptosis in human NK cell line NK92 more effectively than in PCN-deficient strain PA14-phZ1/2 via a yet undetermined mechanism. In the current study, we found that PCN-induced NK92 cell apoptosis occurs through mitochondrial damage despite inhibiting intracellular ROS generation. Intracellular Ca2+ ([Ca2+]i) and Bcl-2 family proteins act as important "priming signals" for apoptosis. PCN treatment increased [Ca2+]i in NK92 cells more than twofold after 2 h stimulation, whereas the Ca2+-chelating agent ethylene glycol tetra-acetic acid (EGTA) inhibited apoptosis. PCN triggered the activation of Bim, Bid, Bik, Bak, and phospho-Bad in NK92 cells in a concentration-dependent manner, but these pro-apoptotic Bcl-2 family proteins were not inhibited by EGTA. In this study, we describe the function of PCN in NK92 cells and identify mitochondrial damage as the mechanism underlying the apoptosis. [Ca2+]i and pro-apoptotic Bcl-2 family proteins are novel targets for PCN-induced apoptosis. Clarification of the cytotoxic diversity of PCN provides a new therapeutic target for defense from P. aeruginosa-induced immune cell damage.