Structure Of Allergens Research Articles

Crystal structure and biochemical characterization of CJP38, a β-1,3-glucanase and allergen of Cryptomeria japonica pollen

A 38 kDa β-1,3-glucanase allergen from Cryptomeria japonica pollen (CJP38) was recombinantly produced in E. coli and purified to homogeneity with the use of Ni-affinity resin. CJP38 hydrolyzed β-1,3-glucans such as CM-curdlan and laminarioligosaccharides in an endo-splitting manner. The optimum pH and temperature for β-1,3-glucanase activity were approximately 4.5 and 50 °C, respectively. The enzyme was stable at 30–60 °C and pH 4.0–10.5. Furthermore, CJP38 catalyzed a transglycosylation reaction to yield reaction products with a molecular weight higher than those of the starting laminarioligosaccharide substrates. The three-dimensional structure of CJP38 was determined using X-ray crystallography at 1.5 Å resolution. CJP38 exhibited the typical (β/α)8 TIM-barrel motif, similar to allergenic β-1,3-glucanases from banana (Mus a 5) and rubber tree latex (Hev b 2). Amino acid sequence alignment of these proteins indicated that the two-consensus IgE epitopes identified on the molecular surfaces of Mus a 5 and Hev b 2 were highly conserved in CJP38. Their conformations and surface locations were quite similar for these proteins. Sequence and structural conservation of these regions suggest that CJP38 is a candidate allergen responsible for the pollen-latex-fruit syndrome relating to Japanese cedar pollinosis.

Development of Rice-Seed-Based Oral Allergy Vaccines Containing Hypoallergenic Japanese Cedar Pollen Allergen Derivatives for Immunotherapy.

Allergen-specific immunotherapy is the only available curative treatment for IgE-mediated allergen diseases. A safe hypoallergenic allergen derivative with high efficiency is required as a tolerogen to induce immune tolerance to the causitive allergens. In this study, to generate a rice-based oral allergy vaccine for Japanese cedar (JC) pollinosis, the tertiary structures of major JC pollen allergens, Cry j 1 and Cry j 2, were more completely destructed by shuffling than the previous ones without losing immunogenicity and then were specifically expressed in the endosperm of transgenic rice seed. They accumulated at high levels and were deposited in endoplasmic reticulum (ER) and ER-derived protein bodies. The low allergenicity of these deconstructed Cry j 1 and Cry j 2 allergens was evaluated by examining their binding activities to the specific IgE antibody and by the basophil degranulation test.

Structural characteristics of lipocalin allergens: Crystal structure of the immunogenic dog allergen Can f 6.

Lipocalins represent the most important protein family of the mammalian respiratory allergens. Four of the seven named dog allergens are lipocalins: Can f 1, Can f 2, Can f 4, and Can f 6. We present the structure of Can f 6 along with data on the biophysical and biological activity of this protein in comparison with other animal lipocalins. The Can f 6 structure displays the classic lipocalin calyx-shaped ligand binding cavity within a central β-barrel similar to other lipocalins. Despite low sequence identity between the different dog lipocalin proteins, there is a high degree of structural similarity. On the other hand, Can f 6 has a similar primary sequence to cat, horse, mouse lipocalins as well as a structure that may underlie their cross reactivity. Interestingly, the entrance to the ligand binding pocket is capped by a His instead of the usually seen Tyr that may help select its natural ligand binding partner. Our highly pure recombinant Can f 6 is able to bind to human IgE (hIgE) demonstrating biological antigenicity.

Fertility and allergy: Is there a correlation?

Approximately 10% of couples have difficulties conceiving. Idiopathic infertility affects 10–15% of infertile couples. Some suspected causes of idiopathic infertility are lifestyle factors such as stress, diet, smoking, obesity, lack of physical exercise and alcohol consumption. At the same time, allergies and bronchial asthma are growing health problems in developed countries. Therefore, this study addresses the possible correlation between atopic diseases and fertility. Several interesting cases of patients presenting symptoms of HSPH (human seminal plasma hypersensitivity) have been reported to date. In the majority of cases, allergy to semen is the IgE-dependent response to proteins contained in the seminal plasma. Observations indicating that patients presenting symptoms of HSPH are primarily allergic to allergens of dogs are particularly interesting. The structure of dog allergen Can f 5 is similar to the human PSA (55–60% similarity in the sequence of amino acids). This may explain the presence of IgE-dependent reactions following contact with semen during sexual intercourse in women allergic to dog fur. This article presents the current state of knowledge on the phenomenon.

Recombinant allergens for immunotherapy: state of the art.

Purpose of reviewMore than 30 years ago, the first molecular structures of allergens were elucidated and defined recombinant allergens became available. We review the state of the art regarding molecular AIT with the goal to understand why progress in this field has been slow, although there is huge potential for treatment and allergen-specific prevention.Recent findingsOn the basis of allergen structures, several AIT strategies have been developed and were advanced into clinical evaluation. In clinical AIT trials, promising results were obtained with recombinant and synthetic allergen derivatives inducing allergen-specific IgG antibodies, which interfered with allergen recognition by IgE whereas clinical efficacy could not yet be demonstrated for approaches targeting only allergen-specific T-cell responses. Available data suggest that molecular AIT strategies have many advantages over allergen extract-based AIT.SummaryClinical studies indicate that recombinant allergen-based AIT vaccines, which are superior to existing allergen extract-based AIT can be developed for respiratory, food and venom allergy. Allergen-specific preventive strategies based on recombinant allergen-based vaccine approaches and induction of T-cell tolerance are on the horizon and hold promise that allergy can be prevented. However, progress is limited by lack of resources needed for clinical studies, which are necessary for the development of these innovative strategies.

In silico prediction of B-cell epitopes for twenty-five mite allergens: The therapeutic potentials for immunotherapy

Mite allergens are one of the major allergens; however, their structures and epitopes have not been thoroughly studied. In the present study, we predicted the tertiary structures of several mite allergens and also identified the B-cell epitopes, which can be suggested as potential epitopes for allergen immunotherapy. Twenty-five mite allergens, from six mite allergen groups, were investigated; homology modeling and structure refinement were performed for seventeen allergens with unknown structures. Furthermore, various servers were employed to predict linear and conformational B-cell epitopes and consensus B-cell epitopes were identified (172 linear and 64 conformational epitopes). Conservation and epitope identity were also determined among the allergens of the same group and some conserved epitopes were identified. Some regions of the predicted epitopes were identified as novel epitope regions. The predicted consensus epitopes can be applied as suitable candidates to design immunotherapeutic vaccines.

Correlating the structure and reactivity of a contact allergen, DNCB, and its analogs to sensitization potential.

We report a study that seeks to find a correlation between the overall sensitization potential quantified by the expression of IL-8 by stimulated monocytes and the chemical structure of a model contact allergen, 2,4-dinitrochlorobenzene (DNCB). We show that structure and reactivity of the chemical compounds play an important role in activation of the monocytes and subsequent inflammation in tissue. However, we observed a non-linear correlation between the rate of reaction and biological activity indicating a required balance of stability and reactivity.

Advances in Molecular Mechanisms of Wheat Allergenicity in Animal Models: A Comprehensive Review.

The prevalence of wheat allergy has reached significant levels in many countries. Therefore, wheat is a major global food safety and public health issue. Animal models serve as critical tools to advance the understanding of the mechanisms of wheat allergenicity to develop preventive and control methods. A comprehensive review on the molecular mechanisms of wheat allergenicity using animal models is unavailable at present. There were two major objectives of this study: To identify the lessons that animal models have taught us regarding the molecular mechanisms of wheat allergenicity and to identify the strengths, challenges, and future prospects of animal models in basic and applied wheat allergy research. Using the PubMed and Google Scholar databases, we retrieved and critically analyzed the relevant articles and excluded celiac disease and non-celiac gluten sensitivity. Our analysis shows that animal models can provide insight into the IgE epitope structure of wheat allergens, effects of detergents and other chemicals on wheat allergenicity, and the role of genetics, microbiome, and food processing in wheat allergy. Although animal models have inherent limitations, they are critical to advance knowledge on the molecular mechanisms of wheat allergenicity. They can also serve as highly useful pre-clinical testing tools to develop safer genetically modified wheat, hypoallergenic wheat products, novel pharmaceuticals, and vaccines.

Quality and potency profile of eight recombinant isoallergens, largely mimicking total Bet v 1-specific IgE binding of birch pollen.

To date, only limited information on structure, expression levels and IgE binding of Bet v 1 variants, which are simultaneously expressed in birch pollen, is available. To analyse and compare structure and serum IgE/IgG binding of rBet v 1 variants to Bet v 1.0101. Recombinant Bet v 1 variants were studied with sera of 20 subjects allergic to birch pollen. Folding, aggregation and solubility of the rBet v 1 variants were analysed to attribute diverging IgE binding to either allergen structure or methodological features. IgE/IgG binding was studied with rBet v 1 in solution or adsorbed to solid phases. Allergen-mediated cross-linking of FcεRI receptors was determined by mediator release of sensitized humanized rat basophil leukaemia cells. All variants, except for rBet v 1.0113, were monomeric and had Bet v 1-type conformation. Serum IgE binding to variants adsorbed to solid phase was reduced to 6.6%-36.5% compared with Bet v 1.0101. In contrast, inhibition of IgE binding to Bet v 1.0101 by rBet v 1 variants ranged from 62% to 83%. Similarly, mediator release ranged from 30.7% to 55.2% for all variants and was only clearly reduced for rBet v 1.0301 (10.4%). The IgE-binding potency of rBet v 1 variants representing their native quantities in birch pollen was only slightly lower compared to extract. IgG binding to variants was between 50.9% and 134.5% compared with rBet v 1.0101 (100%). Bet v 1 variants previously classified as hypoallergenic can exhibit similar functional IgE binding as Bet v 1.0101. Eight rBet v 1 variants largely reproduce total Bet v 1-specific IgE binding of birch pollen extracts. Assay format-dependent variation in IgE-binding properties needs to be considered in the development of diagnostic or therapeutic products.

Crystal structure of the dog allergen Can f 6 and structure-based implications of its cross-reactivity with the cat allergen Fel d 4

Several dog allergens cause allergic reactions in humans worldwide. Seven distinct dog allergens, designated Canis familiaris allergen 1 to 7 (Can f 1–Can f 7), have been identified thus far. Can f 6 shows high sequence similarity and cross-reactivity with Fel d 4 and Equ c 1, major cat and horse allergens, respectively. This study was conducted on the allergenic epitopes of Can f 6 based on its structural characterization. We demonstrated that sera from 18 out of 38 (47%) dog-sensitized patients reacted to recombinant Can f 6 protein (rCan f 6). We then determined the crystal structure of rCan f 6 by X-ray crystallography, which exhibited a conserved tertiary structural architecture found in lipocalin family proteins. Based on the tertiary structure and sequence similarities with Fel d 4 and Equ c 1, we predicted three IgE-recognizing sites that are possibly involved in cross-reactivity. Substituting three successive amino acids in these sites to triple alanine decreased IgE reactivity to the allergen. However, the degree of reduction in IgE reactivity largely depended on the site mutated and the serum used, suggesting that Can f 6 is a polyvalent allergen containing multiple epitopes and Can f 6-reactive sera contain varied amounts of IgE recognising individual Can f 6 epitopes including those predicted in this study. We also demonstrated that the predicted epitopes are partly involved in IgE cross-reactivity to Fel d 4. Interestingly, the effect of the mutation depended on whether the protein was structured or denatured, indicating that the bona fide tertiary structure of Can f 6 is essential in determining its IgE epitopes.

Hypoallergenic Proteins for the Treatment of Food Allergy

Food allergy is a growing health problem worldwide that impacts millions of individuals. Current treatment options are limited and strict dietary avoidance remains the standard of care. Immunotherapy using whole, native allergens is under active clinical investigation but harbors the risk of severe side effects including anaphylaxis. Newer food-specific therapies with hypoallergenic proteins may potentially offer safer treatment alternatives, and this review seeks to investigate the evidence supporting the use of these modalities. The utilization of different methods to alter allergen structure and IgE binding leads to reduced allergenicity and decreases the risk for systemic reactions, making the use of potential therapies including extensively heated egg/milk, peptide immunotherapy, recombinant allergen immunotherapy, and DNA vaccines safe and possibly efficacious forms of treatment in food allergy. However, for the majority of these treatment modalities, limited data currently exists looking at the safety and efficacy in human subjects with food allergy. This review provides a comprehensive overview of the current evidence examining the safety and efficacy of hypoallergenic proteins in the treatment of food allergies.

A Comprehensive Review on Kiwifruit Allergy: Pathogenesis, Diagnosis, Management, and Potential Modification of Allergens Through Processing.

Kiwifruit is rich in bioactive components including dietary fibers, carbohydrates, natural sugars, vitamins, minerals, omega-3 fatty acids, and antioxidants. These components are beneficial to boost the human immune system and prevent cancer and heart diseases. However, kiwifruit is emerging as one of the most common elicitors of food allergies worldwide. Kiwifruit allergy results from an abnormal immune response to kiwifruit proteins and occur after consuming this fruit. Symptoms range from the oral allergy syndrome (OAS) to the life-threatening anaphylaxis. Thirteen different allergens have been identified in green kiwifruit and, among these allergens, Act d 1, Act d 2, Act d 8, Act d 11, and Act d 12 are defined as the "major allergens." Act d 1 and Act d 2 are ripening-related allergens and are found in abundance in fully ripe kiwifruit. Structures of several kiwifruit allergens may be altered under high temperatures or strong acidic conditions. This review discusses the pathogenesis, clinical features, and diagnosis of kiwifruit allergy and evaluates food processing methods including thermal, ultrasound, and chemical processing which may be used to reduce the allergenicity of kiwifruit. Management and medical treatments for kiwifruit allergy are also summarized.

Cross-Reactivity between Major IgE Epitopes of Family 5 Allergens from Dermatophagoides pteronyssinus and Blomia tropicalis

Background: The aim of this work was to understand the molecular features that trigger the cross-reactivity observed between Der p 5 from Dermatophagoides pteronyssinus, Blo t 5 from Blomia tropicalis, and Der f 5 from D. farinae. Methods: We collected serum from 60 house dust mite (HDM)-allergic patients residing in the Dellys area of Boumerdès province in northern Algeria. The presence of specific IgE to Der p 5, Der f 5, and Blo t 5 was analyzed. We performed in silico analysis of the structure of the different allergens in order to identify epitopes that can elicit the cross-reactivity of the sera. Synthetic peptides corresponding to the linear epitope sequence of Der p 5, Der f 5, and Blo t 5 were used to evaluate its implication in the cross-reactivity between the allergens. We also modified the sequence of the conformational epitope of Der p 5 by site-directed mutagenesis to mimic Blo t 5. Results: Several sera of patients allergic to HDM contained specific IgE antibodies to Der p 5 and Blo t 5. We demonstrated that the linear epitope of Der p 5 and Blo t 5 is not involved in the cross-reactivity of the sera. Furthermore, mutations introduced in the sequence of Der p 5 to mimic Blo t 5 could not modulate the cross-reactivity between them. Conclusions: The major linear IgE epitopes of Der p 5 and Blo t 5 are involved in species-specific recognition. Our results may be useful for the development of a hypoallergenic vaccine against HDM group 5 allergens.

Effects of different thermal processing methods on the structure and allergenicity of peanut allergen Ara h 1.

Boiling and frying can alter the structure of peanut allergens and therefore change the IgE‐binding capacity of the Ara h 1. In this research, we aim to clarify the connections between structural changes and the allergenicity alteration, and recommend an effective thermal method to minimize the allergenicity of Ara h 1. Anion exchange chromatography was used to isolate Ara h 1 from non/heat‐treated peanuts. Ara h 1 in boiled peanuts has a relatively low hydrophobic index, reduced maximum emission wavelength in the fluorescence, less content of α‐helix, and the lowest IgE‐binding efficiency. On the contrary, Ara h 1 in fried peanuts present a much higher degeneration degree, a red shift in fluorescence, and a decrease in the content of α‐helix. These data indicate that boiling can reduce the allergenicity of Ara h 1, thus can be utilized in peanut processing from a security point of view.

Immunoinformatics Based Vaccine Design for Zea M 1 Pollen Allergen

Objective: Zea m1 is one of the most common aeroallergens, causing allergy. This pollen allergen, present in maize, is responsible for type I hypersensitivity reaction. Despite having available X ray crystal structure of this pollen allergen, no definite vaccine has been developed for allergic disorder in humans. Method: In our present study, an epitope-based peptide vaccine against Zea m 1 pollen allergen, using a combination of B cell and T cell epitope predictions, followed by molecular docking and molecular dynamics simulation methods are carried out. Here, protein sequences of homologous pollen allergens of Zea m1 are collected and conserved regions present in them are investigated. Result: From the identified region of the allergenic protein, the peptide sequence KVPPGPNITTNY and the sequence AEWKPMKLSM are considered as the most potential B cell and T cell epitopes respectively. Furthermore, this predicted T cell epitope AEWKPMKLSM interacted with MHC allelic protein HLAB* 44:02 with the lowest IC 50 value (7.94 nM). This epitope perfectly fitted into the epitope binding groove of alpha helix of MHC I molecule with lowest energy weighted score -620.0, showing stability in MHC binding. This epitope also showed a good conservancy of 69.75% in world population coverage. Conclusion: The epitopes KVPPGPNITTNY and AEWKPMKLSM may be considered as potential peptide for peptide vaccine for pollen allergen after further experimental study. Key words: Immunoinformatics, Vaccine design, Zea m1 pollen allergen, B cell epitope, T cell epitope, Molecular docking, Molecular dynamics.

Investigation of the interaction of allergens of Glycine max with IgE-antibody for designing of peptidomimetics based anti-allergen

Allergen induced IgE dependent type I hypersensitivity is the main cause of the allergy, which would be a burden on medical setup in coming years. Allergens of Glycine max have been isolated, and their disease relationships are documented. Therefore, it becomes important to investigate the interaction of different allergens of Glycine max with IgE and also screen suitable therapeutics to prevent this interaction. The amino acid sequences of all allergens of Glycine max and their isoallergens have been taken, and 3D structure of allergens (Gly m 3, Gly m 4, Gly m 5, Gly m 6 and Gly m 8) and their isoallergens were generated using Modeller v9.17. The modeled structures were further validated using PSVS, ProSA, RAMPAGE, and PDBsum. HL domain of Fab region of human IgE (PDBID: 2R56) was generated using UCSFchimera. The HL domain was minimized by Schrodinger software using the OPLS_2005 force field. SiteMap identified epitope binding site of the minimized domain. All the predicted epitopes of different allergens were docked to the binding site of HL domain using the Patchdock server. We have also designed a peptidomimetics based inhibitor targeted at interaction interface of Gly m8 and IgE, using in-silico virtual screening, molecular mechanics, and molecular dynamics simulation studies. These studies identified BDE32166344 ((N-(1-{[1-(1-aminocyclopentanecarbonyl)-3-hydroxypyrrolidin-3-yl]methyl}piperidin-4-yl)acetamide) as a peptidomimetics based lead with binding energy of −72.77 kcal/mol. Therefore, the present study investigates the interaction between different Gly m allergens and IgE antibody and identifies peptidomimetics based lead that might be developed as a suitable therapeutics against allergy caused by allergen of Glycine max.

Similar localization of conformational IgE epitopes on the house dust mite allergens Der p 5 and Der p 21 despite limited IgE cross-reactivity.

BackgroundDue to high IgE recognition frequency and high allergenic activity, Der p 5 and Der p 21 are clinically important house dust mite (HDM) allergens. The objective of this study was to characterize the immunodominant IgE epitopes of Der p 5 and Der p 21 responsible for their high allergenic activity.MethodsA panel of 12 overlapping peptides spanning the Der p 5 and Der p 21 sequence were synthesized to search for sequential IgE epitopes by direct testing for allergic patients' IgE reactivity. Peptide‐specific antibodies raised in rabbits were used in inhibition studies for localizing conformational IgE epitopes which were visualized on the surfaces of the allergen structures by molecular modelling. IgE cross‐reactivity between the allergens was investigated by IgE inhibition studies.ResultsImmunodominant IgE epitopes defined by allergic patients' IgE on Der p 5 and Der p 21 were primarily of the conformational, discontinuous type including N‐ and C‐terminal portions of the protein. They could be located on each allergen on one area with similar localization, but despite similar structure of the allergens, no relevant IgE cross‐reactivity could be detected.ConclusionOur study shows that Der p 5 and Der p 21 contain a major conformational IgE epitope‐containing area located on similar portions of their structure, but they lack relevant IgE cross‐reactivity. These data are important for the development of modern allergy vaccines based on defined molecules for allergen‐specific immunotherapy of HDM allergy.

Component-resolved diagnostics to direct in venom immunotherapy: Important steps towards precision medicine.

Stings of Hymenoptera can induce IgE-mediated systemic and even fatal allergic reactions. Venom-specific immunotherapy (VIT) is the only disease-modifying and curative treatment of venom allergy. However, choosing the correct venom for VIT represents a necessary prerequisite for efficient protection against further anaphylactic sting reactions after VIT. In the past, therapeutic decisions based on the measurement of specific IgE (sIgE) levels to whole venom extracts were not always straightforward, especially when the patient was not able to identify the culprit insect. In the last years, the increasing knowledge about the molecular structure and relevance of important venom allergens and their availability as recombinant allergens, devoid of cross-reactive carbohydrate determinants, resulted in the development of an advanced component-resolved diagnostics (CRD) approach in venom allergy. Already to date, CRD has increased the sensitivity of sIgE detection and enabled the discrimination between primary sensitization and cross-reactivity, particularly in patients with sensitization to both honeybee and vespid venom. Hence, CRD in many patients improves the selection of the appropriate immunotherapeutic intervention. Moreover, the detailed knowledge about sensitization profiles on a molecular level might open new options to identify patients who are at increased risk of side-effects or not to respond to immunotherapy. Therefore, increasing potential of CRD becomes evident, to direct therapeutic decisions in a personalized and patient-tailored manner. Reviewed here are the state of the art options, recent developments and future perspectives of CRD of Hymenoptera venom allergy.

Thermal treatment reduces gliadin recognition by IgE, but a subsequent digestion and epithelial crossing permits recovery

Wheat is one of the most important crops in the world in terms of human nutrition. With regards to health, some individuals exhibit wheat-related disorders such as food allergy to wheat (FAW). In this disorder, gluten is involved, particularly the gliadins which are among the main proteins responsible for FAW. Food processing, as well as digestibility and intestinal transport are key factors to consider since they may affect the allergenic potential of food allergens.Wheat is always consumed after heat processing and this step may impact epitope accessibility by inducing aggregation and may irreversibly destroy conformational epitopes. Our aim was to investigate the effects of heating and digestion on the structure of well-known allergens (total gliadins and α-gliadins) and their capacity to maintain their allergenic potential after crossing an intestinal barrier.The sizes of the processed (heated and heated/digested) proteins were characterized by laser light scattering and chromatographic reverse phase. The IgE-binding capacities of native and processed proteins were checked using a dot blot with sera from wheat allergenic patients. Furthermore, the abilities of these samples to cross the intestinal barrier and to induce mast cell degranulation were investigated by combining two in vitro cellular models, Caco-2 and RBL-SX38.The heat treatment of total gliadins and α-gliadins induced the production of large aggregates that were hardly recognized by IgE of patients in dot-blot. However, after limited pepsin hydrolysis, the epitopes were unmasked, and they were able to bind IgE again. Native proteins (gliadins and α-type) and processed forms were able to cross the Caco-2 cells in small amount. Permeability studies revealed the capacity of α-gliadins to increase paracellular permeability. In the RBL assay, the total native gliadins were able to trigger cell degranulation, but none of their processed forms. However after crossing the CaCo-2 monolayer, processed gliadins recovered their degranulation capacity to a certain extent. Total native gliadins remained the best allergenic form compared to α-type.

Peptide and Recombinant Allergen Vaccines for Food Allergy.

Food allergy is a significant public health problem, with no suitable treatments available for patients. Currently, patients are limited to avoidance and the use of readily available emergency medications. Immunotherapy is an appealing therapeutic strategy for inducing tolerance. Studies with whole native allergens have demonstrated the efficacy of immunotherapy for food allergy; however, the risk of IgE-mediated reactions with such treatment is significant. Advances in molecular biology techniques, including purification, sequencing, and cloning, have allowed researchers to identify specific allergen components and T cell binding epitopes. Support for the use of recombinant and peptide vaccines for food allergy comes from prior studies involving aeroallergens and hymenoptera venom. By manipulating allergen structure and IgE binding, allergenicity can be reduced, thereby reducing systemic reactions, making recombinant and peptide vaccines a safe and effective form of immunotherapy. Pre-clinical studies using in vitro and murine models demonstrated a more tolerant state following the use of these therapies. Studies with human subjects will be necessary to characterize the effects of recombinant and peptide food allergy vaccines and to demonstrate a safe treatment option for patients.