Cloning, expression, and characterization of Der f 7, an allergen of Dermatophagoides farinae from China

Consideration of methods for identifying mite allergens

House dust mites are small arthropods that produce proteins—found in their feces, body parts, and eggs—that are major triggers of human allergies worldwide. The goal of this review is to describe the current methods used to identify these allergens. A literature search for allergen identification methods employed between 1995 and 2016 revealed multiple techniques that can be broadly grouped into discovery and confirmation phases. The discovery phase employs screening for mite proteins that can bind IgEs in sera from animals or patients allergic to dust mites. The confirmation phase employs biochemical methods to isolate either native or recombinant mite proteins, confirms the IgE binding of the purified allergens, and uses either in vitro or in vivo assays to demonstrate that the purified antigen can stimulate an immune response. The methods used in the two phases are defined and their strengths and weaknesses are discussed. The majority of HDM-allergic patients may respond to just a small subset of proteins, but new protein discovery methods are still warranted in order to develop a complete panel of HDM allergens for component resolved diagnosis and patient-tailored therapies.

Chinese Guideline on allergen immunotherapy for allergic rhinitis

The present document is based on a consensus reached by a panel of experts from Chinese Society of Allergy (CSA) and Chinese Allergic Rhinitis Collaborative Research Group (C2AR2G). Allergen immunotherapy (AIT), has increasingly been used as a treatment for allergic rhinitis (AR) globally, as it has been shown to provide a long-term effect in improving nasal and ocular symptoms, reducing medication need, and improving quality of life. AIT is currently the only curative intervention that can potentially modify the immune system in individuals suffering from AR and prevent the development of new sensitization and the progression of disease from AR to asthma. Although the use of AIT is becoming more acceptable in China, to date no AR immunotherapy guideline from China is available for use by the international community. This document has thus been produced and covers the main aspects of AIT undertaken in China; including selection of patients for AIT, the allergen extracts available on the Chinese market, schedules and doses of allergen employed in different routes of AIT, assessment of effect and safety, patients' administration and follow-up, and management of adverse reactions. The Chinese guideline for AR immunotherapy will thus serve as a reference point by doctors, healthcare professionals and organizations involved in the AIT of AR in China. Moreover, this guideline will serve as a source of information for the international community on AIT treatment strategies employed in China.

Sequential epitopes of Dermatophagoides farinae allergens identified using peptide microarray-based immunoassay

House dust mites produce over 30 proteins proposed to induce immunoglobulin E (IgE) antibody production in patients. Continued identification of IgE-binding epitopes of these allergens is critical to advancing diagnosis and treatment of allergic disease. To identify possible sequential IgE-binding epitopes of the major- and mid-potency allergens from the house dust mite Dermatophagoides farinae by peptide microarray-based immunoassay, nucleotide sequences of D. farinae allergens (Der f) 1, 2, 4, 5, and 7 were used to generate overlapping peptides covering the full protein sequences minus signal peptides. Short peptides were printed onto microarray chips. Because asthma occurs as a symptom of mite allergy more commonly among children than adults, the peptide chips were exposed to sera pooled from six serum-positive pediatric patients with D. farinae hypersensitivity and six serum-negative control children for screening sequential IgE-binding epitopes by IgE immunolabeling. Higher-than-average immunolabel signal intensity was observed for 21 short peptides in the serum-positive group (P < 0.01). Due to sequence overlap, these 21 signals represented four fragments of Der f 1 (amino acid positions 46-53, 71-78, 99-110, 179-186), three fragments of Der f 2 (15-22, 80-89, 106-113), six fragments of Der f 4 (69-82, 107-116, 225-232, 261-268, 355-365, 483-496), one fragment of Der f 5 (102-109), and three fragments of Der f 7 (32-39, 52-64, 100-107). These findings not only demonstrate the utility of a peptide microarray immunoassay in identifying epitopes for these allergens, but also provide a foundation for future exploration of specific immunotherapies. © 2016 IUBMB Life, 68(10):792-798, 2016.

Dust mite allergen Der f 4: Expression, characterization, and IgE binding in pediatric asthma

BACKGROUND

House dust mite hypersensitivity affects millions of people worldwide, and although many allergens produced by house dust mite species have been identified, some of the less potent allergens remain to be studied.

METHODS

The full-length cDNA encoding the group 4 allergen of the house dust mite species Dermatophagoides farinae (Der f 4) was generated through degenerate primer-based PCR, 5' RACE, and 3' RACE, and the cDNA fragment was cloned into an expression vector for nucleotide sequencing. Following codon optimization and removal of the signal peptide sequence, the mature gene fragment was subcloned into pET-28b (+) and transfected into E. coli BL21 cells for expression. The recombinant protein was purified by nickel affinity chromatography, identified by SDS-PAGE, Western blotting, and MALDI-TOF, and tested by ELISA for IgE reactivity with sera from individuals with asthma. Bioinformatics analyses were used to identify features of Der f 4.

RESULTS

SDS-PAGE and Western blotting of the codon-optimized expression product showed a specific band. The mature recombinant Der f 4 was characterized as a stable and hydrophilic 57.9-kDa protein, and its secondary structure comprised alpha helix (25.3%), extended strand (22.51%), and random coils (52.19%). The structure of the recombinant protein was consistent with that of α-amylase. Among 27 pediatric asthma patients, 40.74% exhibited reactivity to rDer f 4 by ELISA.

CONCLUSIONS

This initial cloning and characterization of the Der f 4 allergen serves as a foundation for future studies into the clinical importance and application of this protein for house dust mite allergy.

Expression, cloning, and IgE-binding of the full-length dust mite allergen Der f 8

Dermatophagoides farinae, a domestic mite species, produces some of the most potent allergens that contribute to allergy in China and worldwide. We sought to clone and express the group 8 allergen of D. farinae (Der f 8) to investigate its IgE-binding reactivity. The full-length cDNA encoding Der f 8 was generated by using RT-PCR and 5' RACE, cloned into pCold-TF expression vector, confirmed by nucleotide sequencing, sub-cloned into pET-28b (+), and transfected into E. coli BL21 cells for expression. After purification by nickel affinity chromatography and identified by SDS-PAGE, the recombinant Der f 8 bound with sera from 40.9 % (9/22) of mite-allergic patients according to ELISA testing. Analysis of the recombinant DNA sequence revealed a 231 amino acid open reading frame encoding a protein with a derived molecular mass of 26.4 kDa and an isoelectric point of 6.84. The deduced amino acid sequence has nine phosphorylation sites, displaying strong homology with glutathione S-transferase, and its secondary structure comprises alpha helix (45.5 %), extended strand (11.3 %), and random coils (43.3 %). BLAST through the National Center for Biotechnology Information database and alignment identified similarity with group 8 allergens or glutathione S-transferases of Dermatophagoides pteronyssinus, Suidasia medanensis, Lepidoglyphus destructor, Glycyphagus domesticus, and Aleuroglyphus ovatus (64, 65, 53, 53, and 50 %, respectively). The first recombinant Der f 8 protein produced in full length successfully bound with patient IgE, demonstrating the importance of Der f 8 in mite allergy.

When mites attack: domestic mites are not just allergens

Domestic mite species found in indoor environments and in warm or tropical regions are well known for causing allergic disorders. However, little is known about human acariasis, in which mites invade and parasitize the human body in various tissues from the gastrointestinal tract to the lung. Here, we summarize the reported cases of human acariasis of pulmonary, intestinal, oral (anaphylaxis), urinary, otic, and vaginal systems. Because the clinical symptoms of acariasis often overlap with other disease symptoms leading to frequent misdiagnosis, we highlight the need for more attention on these infections.

Arsenic trioxide inhibits viability of pancreatic cancer stem cells in culture and in a xenograft model via binding to SHH-Gli

OBJECTIVE

Overexpression of the sonic hedgehog (SHH) signaling pathway is an essential characteristic of pancreatic cancer stem cells (PCSCs) and arsenic trioxide (ATO) is described as a SHH inhibitor. This study evaluates whether ATO has the potential to inhibit viability of PCSCs via binding to SHH-Gli proteins.

METHODS

Cell counting kit-8 and flow cytometry were used for analyzing apoptosis in cells in vitro. The animal model was an athymic nude mouse model bearing subcutaneous xenografts of SW1990 pancreatic cancer cells. The terminal deoxynucleotidyl transferase dUTP nick end labeling assay and immunohistochemistry were used for tumor tissue analysis. The interaction between Gli1 and ATO was examined by a confocal system and an ultraviolet absorption spectrum assay.

RESULTS

ATO induced apoptosis in pancreatic cancer cells, especially CD24(+)CD44(+) cells in vitro. Combination treatment of ATO and low dose gemcitabine inhibited tumor growth by 60.9% (P = 0.004), and decreased the expression of CD24, CD44, and aldehyde dehydrogenase 1 family, member A1 significantly in vivo. ATO changed the structure of the recombinant Gli1 zinc finger peptides in a cell-free condition and the binding action of ATO to recombinant Gli1 was observed in cultured pancreatic cancer cells.

CONCLUSION

ATO may have the potential to inhibit viability of PCSCs via binding to SHH-Gli proteins in vitro and in vivo.

Arsenic trioxide inhibits viability of pancreatic cancer stem cells in culture and in a xenograft model via binding to SHH-Gli

Objective

Overexpression of the sonic hedgehog (SHH) signaling pathway is an essential characteristic of pancreatic cancer stem cells (PCSCs) and arsenic trioxide (ATO) is described as a SHH inhibitor. This study evaluates whether ATO has the potential to inhibit viability of PCSCs via binding to SHH-Gli proteins.

Methods

Cell counting kit-8 and flow cytometry were used for analyzing apoptosis in cells in vitro. The animal model was an athymic nude mouse model bearing subcutaneous xenografts of SW1990 pancreatic cancer cells. The terminal deoxynucleotidyl transferase dUTP nick end labeling assay and immunohistochemistry were used for tumor tissue analysis. The interaction between Gli1 and ATO was examined by a confocal system and an ultraviolet absorption spectrum assay.

Results

ATO induced apoptosis in pancreatic cancer cells, especially CD24⁺CD44⁺ cells in vitro. Combination treatment of ATO and low dose gemcitabine inhibited tumor growth by 60.9% (P = 0.004), and decreased the expression of CD24, CD44, and aldehyde dehydrogenase 1 family, member A1 significantly in vivo. ATO changed the structure of the recombinant Gli1 zinc finger peptides in a cell-free condition and the binding action of ATO to recombinant Gli1 was observed in cultured pancreatic cancer cells.

Conclusion

ATO may have the potential to inhibit viability of PCSCs via binding to SHH-Gli proteins in vitro and in vivo.

The group 10 allergen of Dermatophagoides farinae (Acari: Pyroglyphidae): cDNA cloning, sequence analysis, and expression in Escherichia coli BL21

Dermatophagoides farinae Hughes, American house dust mite, is highly allergenic, producing symptoms in people worldwide. Identifying and cloning the allergens in this species may enable better diagnostic and therapeutic approaches. Here, we cloned, sequenced, and expressed the full-length cDNA encoding D. farinae group 10 allergen (Der f 10) isolated from dust mites in China. Bioinformatic analysis indicated that the 888 bp sequence encoded a cytoskeleton protein 295 amino acids long, with a molecular weight of approximately equal 34 kDa. Sequence alignment with the group 10 allergens of Pyroglyphidae, Acaridae, and Glycyphagidae families revealed that the group 10 allergen from D. farinae is 95% similar to D. pteronyssinus Trouessart and Psoroptes ovis (Hering). These findings lay the groundwork for future studies, including large-scale production of recombinant Der f 10 allergen for diagnostic and therapeutic agents.

Crystal structure of Der f 7, a dust mite allergen from Dermatophagoides farinae

BACKGROUND

Der f 7 is the group 7 allergen from the dust mite Dermatophagoides farinae, homologous to the major allergen Der p 7 from D. pteronyssinus. Monoclonal antibody that bind to residues Leu48 and Phe50 was found to inhibit IgE binding to residue Asp159, which is important for the cross-reactivity between Der f 7 and Der p 7.

METHODOLOGY/PRINCIPAL FINDINGS

Here, we report the crystal structure of Der f 7 that shows an elongated and curved molecule consisting of two anti-parallel β-sheets--one 4-stranded and the other 5-stranded--that wrap around a long C-terminal helix. The overall fold of Der f 7 is similar to Der p 7 but key difference was found in the β1-β2 loop region. In Der f 7, Leu48 and Phe50 are in close proximity to Asp159, explaining why monoclonal antibody binding to Leu48 and Phe50 can inhibit IgE binding to Asp159. Both Der f 7 and Der p 7 bind weakly to polymyxin B via a similar binding site that is formed by the N-terminal helix, the 4-stranded β-sheet and the C-terminal helix. The thermal stability of Der f 7 is significantly lower than that of Der p 7, and the stabilities of both allergens are highly depend on pH.

CONCLUSION/SIGNIFICANCE

Der f 7 is homologous to Der p 7 in terms of the amino acid sequence and overall 3D structure but with significant differences in the region proximal to the IgE epitope and in thermal stability. The crystal structure of Der f 7 provides a basis for studying the function and allergenicity of this group of allergens.

Cloning, bioinformatics analysis, and expression of the dust mite allergen Der f 5 of Dermatophagoides farinae

Crude extracts of house dust mites are used clinically for diagnosis and immunotherapy of allergic diseases, including bronchial asthma, perennial rhinitis, and atopic dermatitis. However, crude extracts are complexes with non-allergenic antigens and lack effective concentrations of important allergens, resulting in several side effects. Dermatophagoides farinae (Hughes; Acari: Pyroglyphidae) is one of the predominant sources of dust mite allergens, which has more than 30 groups of allergen. The cDNA coding for the group 5 allergen of D. farinae from China was cloned, sequenced and expressed. According to alignment using the VECTOR NTI 9.0 software, there were eight mismatched nucleotides in five cDNA clones resulting in seven incompatible amino acid residues, suggesting that the Der f 5 allergen might have sequence polymorphism. Bioinformatics analysis revealed that the matured Der f 5 allergen has a molecular mass of 13604.03 Da, a theoretical pI of 5.43 and is probably hydrophobic and cytoplasmic. Similarities in amino acid sequences between Der f 5 and allergens of other domestic mite species, viz. Der p 5, Blo t 5, Sui m 5, and Lep d 5, were 79, 48, 53, and 37%, respectively. Phylogenetic analysis indicated that Der f 5 and Der p 5 clustered together. Blo t 5 and Ale o 5 also clustered together, although Blomia tropicalis and Aleuroglyphus ovatus belong to different mite families, viz. Echimyopodidae and Acaridae, respectively.

Cloning of the surface layer gene sllB from Bacillus sphaericus ATCC 14577 and its heterologous expression and purification

A cDNA fragment encoding the S-layer protein SllB cloned from Bacillus sphaericus ATCC 14577 was expressed on the surface of E. coli BL21 (DE3) cells and confirmed by the square lattice structure at the nanoscale level. The amplified gene fragment designed with PCR primers from a specified reference sequence (GenBank accession no. AJ849550) showed a high degree of sequence identity with the known sequences for S-layer protein. The best alignment scores were seen in B. sphaericus strains JG-A12 and NCTC9602, which code for a pre-form protein with a predicted cleavage site located between the two alanine residues 31 and 32. After this signal peptide sequence was removed, the mature protein had a molecular mass of 116.2613 kDa and a theoretical pI of 5.40. Further bioinformatic analysis revealed three S-layer homology (SLH) domains in the N-terminus of the mature protein, positioned at the 1–61, 63–128 and 137–197 residues. The mature S-layer protein was composed of alpha helices (24.86%), extended strands (27.01%), and rich random coils (48.13%). Bioinformatics-driven characterization of SllB may provide scientific evidence for further application of this gene in the fields of nanobiotechnology and biomimetics in the future.

Cloning, expression, purification, crystallization and preliminary X-ray diffraction studies of a major group 7 allergen, Der f 7, from the dust mite Dermatophagoides farinae

Der f 7 is a major group 7 allergen from the dust mite Dermatophagoides farinae that shows 86% sequence identity to the homologous allergen Der p 7 from D. pteronyssinus. Der f 7 was successfully overexpressed in an Escherichia coli expression system and purified to homogeneity using Ni-NTA affinity and size-exclusion column chromatography. SeMet-labelled Der f 7 was crystallized by the hanging-drop vapour-diffusion method using a reservoir solution consisting of 0.1 M bis-tris pH 7.4 and 28% polyethylene glycol monomethyl ether 2000 at 293 K. X-ray diffraction data were collected to 2.24 Å resolution using synchrotron radiation. The crystals belonged to the orthorhombic system, space group P2(1)2(1)2(1), with unit-cell parameters a = 50.19, b = 58.67, c = 123.81 Å. Based on the estimated Matthews coefficient (2.16 Å(3) Da(-1)), two molecules of Der f 7 could be present in the asymmetric unit of the crystal lattice.