Non-Injectable Mucosal Vaccines Providing Safe and Less Stressful Immunization Professor Future Medicine and Research Organization, Chiba University / Chiba University Hospital Hiroshi KIYONO

At Chiba University (CU), one key area of research is mucosal immunology and mucosal vaccines being conducted under the international collaborative roof of the CU-UCSD Center for Mucosal Immunology, Allergy and Vaccines (cMAV). Mucosal vaccines are administered orally or via nasal spray and are thus considered the less stressful vaccination strategy when compared with widely used needle-type vaccines. In addition, oral and nasal vaccination can provide dual protection against pathogens at the mucosal surface and inside the body. One type of oral vaccine is also called a ‘green vaccine’ because it is made from rice grown in a closed hydroponic system with no associated industrial or medical waste generated to dispose of and requires no refrigeration for storage.

From Dental Caries to Mucosal Vaccine Research

Dr. Kiyono said that dental caries constituted a major oral health problem when he graduated from Nihon University School of Dentistry at Matsudo in 1977. At that time, a project to develop a vaccine to prevent dental caries was launched mainly in Europe and the United States. Immediately after graduation, he went to study at the Jerry McGee Lab at the University of Alabama in Birmingham and joined their vaccine development team.

Back then, the immune system was considered to exist only inside the body cavity, for example, in the peripheral lymph nodes, spleen, and bone marrow. Few believed that elements of adaptive and flexible immunity are present in the gastrointestinal and respiratory systems, such as in the oral cavity and nasopharynx, which are lined with mucous membranes.

He and his team collated basic research in this area and proved that an adaptive and flexible immune system does exist in the oral, digestive, and respiratory tracts. Today, all immunological studies include mucosal immunity, which has become one of the major areas of research in immunology.

Old Yet New Nasal Vaccines

In the 1990s, he and his colleagues set up a laboratory for the study of mucosal immunity – the first of its kind in Japan – at the Research Institute for Microbial Diseases at Osaka University. The late Dr. Yoshiomi Okuno and others at The University of Osaka had already conducted a trial in which tens of thousands of Japanese schoolchildren were administered a nasal spray of attenuated influenza viruses. The effectiveness of this spray vaccine was compared with that of the injected vaccine by evaluating absenteeism from school due to viral infection in the two groups, because the effects of mucosal immunity were not considered at that time. Meanwhile, scientific evidence was gradually accumulating, including Dr. Kiyono and his team’s studies to support the effectiveness of aerodigestive mucosal immune systems. They subsequently decided to develop a safe mucosal vaccine without side effects.

Rice-Based Vaccines

In 2003, Dr. Kiyono and his team established a new mucosal immunology laboratory at the Institute of Medical Science, University of Tokyo, and continued basic research on advancing mucosal immunology along with clinical research leading to the development of mucosal vaccines. Developing countries were the primary targets for oral vaccine development because injectable vaccines need to be frozen or refrigerated after production until they are transported to vaccination sites, known as a cold chain, and this task is difficult and expensive in developing countries. Additionally, injectable vaccines require syringes and needles; in developing countries, this can lead to secondary infections and pose environmental risks because they are often reused or not disposed of properly.
To overcome these challenges, the team began developing the cold-chain- and syringe/needle-free rice-based mucosal vaccine as a prototype of a ‘green vaccine.’ Therefore, this ‘green vaccine’ was a truly novel and unique approach in the vaccinology field.

MucoRice: Introducing Vaccine Antigen Genes into Rice

Dr. Kiyono’s team members, Dr. Yoshikazu Yuki, Dr. Tomonori Nochi (Professor at Tohoku University), and others in the laboratory, together with our excellent collaborators in the fields of agriculture science and plant science, conducted fusion research on introducing vaccine antigen genes into rice. The research was carried out under the guidance of experts in rice science from the Graduate School of Agriculture at Kyoto Prefectural University, the National Agriculture and Food Research Organization, and the National Institute of Agrobiological Resources.

In collaboration with Dr. Eiji Goto of the Graduate School of Horticulture at Chiba University and a team of investigators from Asahi Kogyosha Co., Ltd., his team also developed the world’s first fully closed hydroponic cultivation system for producing GMP-grade rice-based oral vaccines. His team named it MucoRice and obtained a patent and trademark for it.

Establishing Production Systems

With this technology, the oral vaccine MucoRice CTB against cholera toxin was developed. In phase I clinical trials, healthy Japanese volunteers were recruited, and the effectiveness of the vaccine in inducing antigen-specific immunity in humans was investigated. The results were published in a paper as joint research by Chiba University, the University of Tokyo, and UCSD in 2021. Additionally, the phase I clinical trials were conducted in the US in cooperation with Astellas Pharma Inc., and the vaccine’s safety and immunogenicity were confirmed. Dr. Goto’s team, in collaboration with Asahi Kogyosha Co., Ltd., is currently constructing a facility for the stable production of MucoRice using LEDs at Chiba University’s Kashiwanoha Campus. This project fortunately received funding from two government initiatives: the Strategic Center of Biomedical Advanced Vaccine Research and Development for Preparedness and Response (SCARDA), funded by Japan Agency for Medical Research and Development (AMED), and the Program for Forming Japan’s Peak Research Universities (J-PEAKS), supported by Japan Society for the Promotion of Science (JSPS).

Challenges to Using Nasal Spray Vaccines

Next, Dr. Kiyono and his colleagues began work on nasal vaccines. Simply administering the vaccine in the nose causes frequent nasal discharge and sneezing. The patient ends up blowing his/her nose, which physically expels the vaccine out of the nose. Therefore, it was a technique to effectively and safely administer and affix the vaccine antigen onto the nasal mucosa.

Meanwhile, Drs. Yuki and Nochi, together with Dr. Akiyoshi Kazunari of Tokyo Medical and Dental University (now Project Professor at Kyoto University), proposed the idea of attaching a nanogel to the nasal mucosa using an electric charge. When the nanogel is administered to the nasal mucosa, the vaccine binds tightly to it. This new nasal vaccine delivery technique, called cationized nanogel, was a breakthrough and the result of collaboration between the fields of medicine and engineering. Based on this technology, Dr. Kiyono launched a university-based venture named HanaVax to advance the development of mucosal vaccines. Currently, the company is working on intranasal vaccines as a subsidiary of Shionogi & Co., Ltd.

Licensing and External Supply

The first application of this cationized nanogel nasal vaccine was to immunize against Streptococcus pneumoniae. Injectable vaccines for Streptococcus pneumoniae already exist, but they can only prevent severe disease development and not the infection itself.

However, when the protein antigen PspA from S. pneumoniae is incorporated into the cationized nanogel and nasally administered, it induces very effective and broad protective immunity against different strains of Streptococcus pneumoniae.
At present, the effectiveness has been confirmed in different species ranging from mice to monkeys. The cationized nanogel nasal vaccine for S. pneumoniae has been licensed and contracted to Shionogi & Co., Ltd. for production through HanaVax, and research and development for human use are ongoing through industry-academia collaboration.

Researcher, Clinician, and Communicator Training

Continuous advancement of this interdisciplinary research and training in mucosal immunology and vaccinology, as well as identification of stakeholders who can interpret the information and make it understandable to the laypeople, is required. It is very important nowadays to recruit individuals who are equipped with the skills to collect and distribute information through the appropriate use of social networking services to help society make informed decisions based on the scientific and objective evidence generated by the leading research in the fields of vaccinology, immunology, and other related medical science.

One of Dr. Kiyono’s dreams is to build a completely closed, large-scale vaccine production facility for MucoRice as part of a sustainable ‘green vaccine’ production system. Utilizing fallow land is also a potential option. Dr. Kiyono and his colleagues are fully committed to developing a new generation of mucosal vaccines and turning the dream into reality. To achieve this, his creation of “One Team CHIBA” aims to strengthen and accelerate the newly created ‘Chiba University Synergy Institute for Futuristic Mucosal Vaccine Research and Development (cSIMVa)’ into a central vaccine research and development hub for industry-academia collaboration.

Originally published on June 6, 2022, this article was subsequently updated on April 8, 2025, to reflect the latest available information.