The Issue
Allergic Rhinitis
Allergic rhinitis, often caused by hay fever, is a common chronic inflammatory disease where the nasal mucosa is triggered by allergens such as pollen. Globally, it affects an estimated number of four hundred million people worldwide and ranks among the most chronic diseases. Prevalence continues to rise especially in industrialized regions and in Japan, seasonal pollinosis which includes cedar and cypress pollen allergy has reached epidemic levels - over one in three people of the population experience months of debilitating symptoms. Moreover, the economic fallout stands out: research done by Panasonic co. ltd states that it is estimated that 232 billion yen (approx 1.74 billion USD) of economic loss happens daily in Japan. Aside from such numbers, allergic rhinitis erodes people's QOL, school/work performance, and can even aggravate asthma and sinusitis. In one of the surveys we conducted, one hay fever patient explained that hay fever diminishes their ability to enjoy cuisine, due to nasal congestion. Another patient complained that hay fever stops them from enjoying the Hanami season, which is during the spring where people have picnics outdoors and enjoy Japanese sakura. As we can see, hay fever not only annoys people as a seasonal burden, but it also restricts people from enjoyment and pleasure.
Problems with current treatment
Standard therapies such as antihistamines, nasal corticosteroids, and decongestants provide temporary symptom relief. They can definitely reduce sneezing, congestion, and itching, but some side effects come along which results in diminishing efficacy of these therapies. Antihistamines can cause drowsiness and impair recognition and concentration; nasal steroids can irritate the mucosa, and with prolonged use, it can possibly thin the nasal lining; decongestants could raise blood pressure and cause rebound congestion if it is overused. The core problem lies in how no single therapy can comprehensively address the multiphase mechanism of hay fever. Allergic rhinitis involves inflammation, sensitization, chronic immune dysregulation, and acute inflammation where each of these conditions are governed by different molecular pathways.
Therefore, we propose an idea to take a holistic/multi-target approach. Our project is built on the understanding of the need to come up with a combined therapeutic strategy to tackle allergic rhinitis. The two solutions that we will propose form a unified platform that addresses multiple domains of the allergic mechanism and offers a path for allergic patients towards safer, more effective, and a systemically balanced therapy.
Project
Project Motive
HG-Tokyo was made during winter 2025.
In our team, approximately 60% of the team members
in HG-Tokyo struggle daily due to severe allergies. One member especially, having been
suffering from multiple allergic diseases such as atopic dermatitis, allergic rhinitis,
chronic allergic rhinitis, allergic conjunctivitis, atopic dermatitis and more, faces
multiple struggles and frustrations. Due to these backgrounds, they have not only tested out
oral anti-histamine medication but have used nasal steroids, oral steroids,
immunosuppressants, and biologics.
They have been taking oral antihistamines for a long time; however, the sedative side effects have been a persistent problem. Although they have tried multiple generations of antihistamines, all of them have caused some degree of drowsiness. When they used systemic immunosuppressants, oral steroids, and biologics, which were originally prescribed for atopic dermatitis but also act on the immune pathways involved in allergic rhinitis, the symptoms of hay fever and rhinitis improved dramatically. The effect was much stronger and more fundamental than the symptomatic relief achieved with antihistamines, which only block histamine receptors. However, although these solutions worked significantly stronger than nasal steroid sprays, the severe side effects related to immune suppressions remain as a large downside of these solutions. Immunosuppressants and steroids both work on the T cells weakening the immune system while allergic symptoms are well treated. This results in side effects where when you get sick, the symptoms get quite severe and long lasting due to its features. This is significant and tough since you have to deal with such symptoms as a runny nose or sore throats longer than other people. It is very troublesome living a normal life due to these symptoms since they last longer and stronger.
Therefore, a new solution that can act on the broader immune mechanisms while maintaining local and safe administration would be ideal.
Hearing this story, the members of HG-Tokyo united with a collective aspiration to find an innovative and effective, yet side-effect-free, solution to hay fever.
Our Hollistic-approached Solution
Our project began with a clear goal: to create a better treatment for hay fever. Many people in Japan, including many of our own team members, suffer from allergic rhinitis every year. Despite this, current treatments often have significant drawbacks, such as side effects or a long treatment duration. Hence, this motivated us to find a superior solution using synthetic biology.
As we researched the allergic reaction through reading multiple peer-reviewed literature, we recognized its complex mechanism. It unfolds in multiple stages and involves many different biological pathways. This led us to a decision point in our design process, where we identified two promising but fundamentally different approaches. After discussing within the team, instead of committing to only one, we made the decision to explore both, and take a dual approach.
To start with, our first project is inspired by nature. We chose to focus on narirutin from the Japanese C. jabara fruit. By using C. jabara in our project, our team aims to spread the name of this fruit and contribute to the regional revitalization of Kitayama village, its place of origin. We selected narirutin because it is a proven compound known to calm the allergic response in several different ways. Therefore, our goal was to take this effective natural ingredient and create a scalable way to mass-produce it using yeast.
Moving on, our second project is based on precision engineering. For this, we rationally designed a novel fusion peptide, a single "smart" molecule engineered to release different therapeutic components that target the early, late, and resolution phases of the allergic reaction. This approach is about building a powerful, multi-stage solution from the ground up.
Ultimately, by pursuing both a nature-inspired and a precision-engineered solution, our project demonstrates the versatile and flexible power of synthetic biology to tackle a complex disease from multiple angles. This is significant because pursuing these dual approaches can provide patients with different types of solutions depending on their unique needs.
Solution 1: Narirutin Biosynthesis
Introduction
Citrus jabara, is a citrus fruit that originates from Kitayama Village, located in the Wakayama Prefecture in Japan, and is still the main cultivation place to this day. From previous research, it is proven that the peels of C. jabara contain a high portion of narirutin, where over 99% of the flavonoids included in the peel consist of this compound. In comparison with other research, C. jabara contains 10 times as much narirutin than Citrus kawachiensis (Kawachi Bankan) and 20 times of Citrus maxima (Pomelo). Since narirutin has proven anti allergic effects and has minimal side effects, we focused on the possibilities of narirutin. Also, as said C. jabara has the most amount of narirutin contained amongst natural objects. Due to such reasons, we focused on C. jabara and narirutin.
However, although C. jabara contains a relatively large amount of narirutin, it still is not enough to suffice for the millions of people suffering with hay fever. It is unrealistic to derive a sufficient amount of narirutin from the C. jabara fruits currently grown, and it would take a tremendous amount of time to newly plant many jabara trees and gather narirutin from the fruits. Therefore, to propose a fast and effective solution that substitutes the idea of mass production of C. jabara, our project aims to develop a novel biotherapeutic solution for hay fever by reconstructing the narirutin biosynthetic pathway in yeast. While the current stage focuses on establishing a proof-of-concept using homologous enzymes from Antirrhinum majus (F7GT) and Citrus sinensis (16RT), the ultimate goal of our project is to develop a complete reconstruction of the narirutin biosynthetic pathway.
Narirutin is a bioactive flavonoid glycoside with anti-allergic properties that are found naturally in citrus fruits. By engineering yeast to produce narirutin at scale, we seek to create a sustainable source of this compound for potential use as a preventive treatment for allergic rhinitis. The ultimate goal of this project is to demonstrate a proof-of-concept living factory that can biosynthesize narirutin by feeding glucose, which lays the groundwork for a new allergy relief product in the future.
Narirutin Biosynthetic Pathway
Narirutin (naringenen-7-O-neophsperiodoside) is a flavanone glycoside which belongs to the citrus family. The biosynthetic pathway begins with the phenylpropanoid pathway where phenylalanine is converted to cinnamic acid by phenylalanine ammonia-lyase (PAL). Then cinnamate 4-hydroxylase (C4H) and 4-coumaroyl-CoA ligase (4CL) produce 4-coumaroyl-CoA, which is the central precursor for flavonoid biosynthesis.
The flavonoid-specific pathway involves chalcone synthase (CHS) catalyzing the condensation of 4-coumaroyl-CoA with three molecules of malonyl-CoA to form naringenin chalcone. Chalcone isomerase (CHI) then cyclizes this intermediate to produce naringenin, which is the aglycone backbone of narirutin.
The glycosylation of naringenin to form narirutin occurs through two enzymatic steps. In the first glycosylation, Flavonoid 7-O-glucosyltransferase (F7GT) adds UDP-glucose to naringenin, which forms naringenin-7-O-glucoside. In the second glycosylation, 1,6-rhamnosyltransferase (6RT) adds UDP-rhamnose to the glucose at the 1 to 6 position, forming the final disaccharide neohesperidose attached at the 7-hydroxyl position of naringein.
This two-step glycosylation process leads to narirutin yield, with each step requiring specific glucosyltransferases and appropriate sugar nucleotide donors of UDP-glucose and UDP-rhamnose.
Our Core Technology
| Parts Code | Parts Name | Type I | Type II | Impact on Project |
|---|---|---|---|---|
| UGT BBa_25LXHO9N | UDP-Glucosyltransferase | Basic Part | Coding Sequence | Transfers a glucose molecule from UDP-glucose to the C7 hydroxyl group of Naringenin to form Naringenin-7-O-glucoside. |
| 16RT BBa_25QUZU2Z | Rhamnosyltransferase | Basic Part | Coding Sequence | Transfers a rhamnose molecule from UDP-rhamnose to the C6 position of the previously attached glucose, forming the Rutinoside disaccharide, resulting in the final product Narirutin. |
At our core, our project relied heavily on one of the homologous enzymes we selected: F7GT (UDP-Glucosyltransferase) from Antirrhinum majus. This built the foundation of the pathway and led to the achievement of producing narirutin with our original biosynthetic pathway that we reconstructed. To be even more precise, the F7GT enzyme that we used was based on a mutant variant of UGT88D7(S127T/R350W) which was reported by Noguchi’s paper - this enhances UDP-glucose donor specificity and the double substitution of S127→Thr and Arg350 →Trp) significantly improves enzyme activity toward UDP-glucose while maintaining its stability. Both parts were codon-optimized for yeast expression and these enzymes together established the two-step glycosylation cascade required for narirutin synthesis. Together, these parts, especially F7GT, opens a new path for future iGEMers to utilize this specific variant for further research.
Narirutin effects
Narirutin tackles allergic symptoms from multiple ways in the pathway for allergic symptoms. Not like antihistamines, steroids and immunotherapy, which only approach the solution only from several ways, such as blocking histamine to bind with histamine receptors or suppressing the production of pro-inflammatory cytokines and immune cells particularly Th2 cells. However narirutin approaches the pathway in multiple steps. It suppresses the production of pro-inflammatory cytokines by inhibiting signaling pathways such as MAPK and NF‑κB, thereby preventing the excessive activation of immune responses. It also inhibits the formation of the NLRP3 inflammasome, which reduces the release of IL‑1β and IL‑18 and prevents secondary inflammation caused by the overactivation of eosinophils and macrophages. Furthermore, by suppressing the activation of Th2 cells, it decreases the production of IL‑4 and IgE, leading to the inhibition of mast cell sensitization and degranulation. As a result, histamine release is suppressed, contributing to the overall attenuation of allergic responses. Not only does it have a wide range of effectiveness, it has very few side effects, unlike the medicines that we have listed before.
Narirutin Effectiveness
Based on multiple murine studies, narirutin demonstrates significant anti-allergic and anti-inflammatory efficacy in vivo.
In the OVA-induced airway inflammation model (Funaguchi et al., 2007), oral administration of 10 mg/kg/day reduced eosinophilic infiltration and serum IgE levels by approximately 50%, and suppressed IL-4 expression by nearly 90%.
In the more recent HDM-induced allergic rhinitis model (Wang et al., 2025), 20–40 mg/kg/day of narirutin markedly decreased nasal inflammation and behavioral symptoms such as sneezing and nose-rubbing by 60-75%, and simultaneously suppressed the USP15-NLRP3-IL-1β/Caspase-1 signaling axis by up to 80%, indicating strong inhibition of inflammasome activation.
Collectively, these findings indicate that narirutin exerts pharmacologically validated effects on both adaptive and innate immune pathways—reducing Th2-associated cytokines (IL-4, IgE) as well as inflammasome-related mediators (NLRP3, IL-1β, Caspase-1). Because these molecular changes are accompanied by observable behavioral improvements, narirutin can be considered scientifically effective in alleviating allergic responses in mice. (Refer to narirutin)
Solution 2: Fusion Peptide
Fusion peptides are engineered molecules that combine multiple short peptides, each designed to perform a specific function, into a single chain. Therefore, engineering fusion peptides is a promising approach to tackling allergic rhinitis, which has multiple phases and steps. However, this approach to allergic rhinitis has not yet been taken, and therefore we aim to pioneer this new holistic approach, opening a new path for hay fever treatment. The goal of the second project is to make a fusion peptide that works on multiple phases by combining peptides each with effects on different phases and utilizing the proteases released throughout the phases to manage the effects of the peptides to minimize side effects.
Our fusion peptide is made with 3 peptides each with anti-allergic properties, one spacer, one Cell Penetrating Peptide (CPP), and four linkers. Each peptide other than the spacer and the CPP in the fusion peptide work on different stages of the mechanism of allergic rhinitis. The peptides and linkers were carefully selected from our options taken from research papers, through performing multiple tests using software such as AlphaFold2 and ProsperousPlus, to predict the structure and cleavage of the fusion peptide.
Fig.2: Making our fusion peptide
Peptides
CPP (GRKKRRQRRRPPQ)
→The CPP is attached to the first peptide to
ensure that the domain 1 peptide is delivered to the intracellular cytoplasm, to
interfere with the NF-κB pathway.
Domain 1 (KPV)
→The first peptide works on the sensitization phase by
inhibiting the activation of the NF-κB pathway and reducing the production of the
interleukins.
Domain 2 (CKGERF)
→The second peptide works on the secondary reaction
phase by blocking CCR3 and preventing eosinophil recruitment and activation.
Spacer Peptide (EEEE)
→The spacer between domain 2 and domain 3
functions as a placeholder for overall peptide stability, and ensures that the peptide
for domain 4 exhibits its effects at the correct stage.
Domain 3 (MYPPPY)
→The third peptide works on the allergy
sensitization phase by promoting regulatory T cell activation and immune tolerance,
reducing the risk of allergic responses and supporting long-term remission.
Linkers
Each peptide exhibits its effect after complete cleavage from the initial fusion peptide.
Linker 1 (PLGLAG)
→Domain 1 will reach the intracellular region upon
full cleavage from the initial fusion peptide following the detection of matrix
metalloproteinase 9 (MMP-9) by the cleavable linker 1, during the allergy sensitization
phase.
Linker 2 (GFLG)
→Domain two will cleave off of the rest of the fusion
peptide after the detection of cathepsin B by the cleavable linker 2, during the
secondary reaction phase.
Linker 3 (IEPD)
→When the cleavable linker 3 detects granzyme B, the
spacer cleaves off of domain 3, and the spacer does not exhibit any effects, while
domain 3 will exhibit its effects to reduce further sensitization.
(Refer to Fusion Peptide)
Nasal Spray
For our two solutions, narirutin and the fusion peptide, a nasal spray is the most beneficial way of delivery to the nasal area. For both narirutin and the fusion peptide, nasal delivery would reduce the amount of substance required to obtain the desirable effects, as well as decreasing the time needed to achieve these effects. Furthermore, for the fusion peptide, nasal delivery would help minimize adverse side effects, since the fusion peptide would not have to enter the digestive system etc.
However, researching the current solutions and medication for allergic rhinitis, we noticed that nasal sprays carry a major problem: they are not 100% recyclable. Therefore, in addition to our biological approaches to tackle hay fever, we also focused on the environmental consequences current solutions to hay fever cause, and created a new, 100% recyclable nasal spray. We designed a 3D-printed nasal spray that avoids the metal springs used in conventional sprays, making it fully recyclable. Our model uses a pull-back piston mechanism to maintain spraying function.
With modular, replaceable parts, the device ensures that individual parts can be replaced when a part is damaged, or when more fluid is needed. This approach extends the device's lifespan and reduces both cost and environmental impact compared to purchasing an entirely new spray unit.
(Refer to Hardware)
Conclusion
Driven by the desire to create an innovative and holistic solution for allergic rhinitis, HG-Tokyo has developed two approaches through natural and engineered approaches.
We are the first team in the world to successfully reconstruct the biosynthetic pathway of narirutin in yeast with the help of the crucial enzyme F7GT derived from snapdragon. We contribute to further iGEM teams in studying flavonoid compounds that lead to healthier lives.
In parallel, our fusion peptide module is a unique and rationally designed peptide that targets multiple phases of the allergic response, and ultimately, we offer a precise and less-side-effect peptide as a new therapeutic solution.
Combining our recyclable nasal spray delivery system, we contribute to the public to form an integrated, sustainable, and socially conscious solution that combats hay fever and alleviates the struggle and burden allergic patients carry.
