Taiwan-Vietnam cooperation in developing a mild vaccine for passion fruit virus
The best way to combat the disease is to breed the passion fruit with disease resistance; however, there is no virus-resistant material for passion fruit now, so we cannot solve the problem through traditional breeding. Other methods are to use a mild vaccine to provide cross-protection against the virus, and to transfer the viral genes into passion fruit to develop genetically modified passion fruit. Since passion fruit is mostly used for juice production, Vietnam has not yet approved the genetically modified passion fruit, so the mild vaccine is the only choice to protect passion fruit in Vietnam. After vaccination, virus-free passion fruit seedlings can be propagated by grafting without increasing the production cost, which can effectively protect the plants from virus infection. It is an ideal way to control the disease, but the key is to develop a mild vaccine with no adverse event on passion fruit.
1. EAPV mild vaccine has been developed and is ready for the field test.
Prof. Shyi-Dong Yeh has already developed a mild PRSV HA 5-1 vaccine that protects papaya against papaya ringspot virus, which has been used for more than 30 years and is internationally recognized. Five years ago, Prof. Yeh began to develop a mild vaccine for passion fruit. First, he targeted the EAPV virus in Taiwan, constructed an infectious cDNA clone, and generated mutations of the HC-Pro gene, the pathogenic gene of the virus. In the end, we finally got several mutant strains that do not show symptoms after infecting passion fruit and successfully boost the immune response to protect passion fruit against the EAPV virus. After tests in the greenhouse, the EAPV-AC mild vaccine was proven to be 100% effective against EAPV in Taiwan and Vietnam. Currently, we are working with VAAS to conduct field tests in Son La, an EAPV-endemic area in Vietnam, which will provide a promising solution to the EAPV spread in northern Vietnam.
2. PaMoV mild vaccine has been developed and is now tested in the greenhouse.
PaMoV is responsible for 70% of passion fruit woodiness diseases in Vietnam, so it's our priority to cope with the virus. After three years of research, the identification of PaMoV and the detection of passion fruit viruses by specific nucleic acid primers are developed by Prof. Yeh's team with four students from Vietnam. In addition, the key infectious cDNA clone has been constructed, so that the pathogen can be eliminated. Using HC-Pro site-directed mutagenesis, we developed three mild strains of the virus, which are being evaluated for stability and inoculation in the greenhouse to fight PaMoV in Vietnam.
3. TelMV mild vaccine is still under development.
TelMV is not yet a major threat in Vietnam. However, just like EAPV, TelMV has caused serious damage in Taiwan's main cultivation area for passion fruit, Dapingding in Puli. TelMV also poses a threat in Thailand and Hainan Island, so Prof. Yeh's team has started to develop a mild vaccine for TelMV. After the whole genome sequencing, the infectious cDNA clone was constructed. Then, using HC-Pro site-directed mutagenesis to eliminate the pathogenicity, we got a few mild strains of the virus. Now we are evaluating the properties of the virus, hoping to overcome the threat of TelMV in various regions.
4. Vaccine field test and applications in industries
With the help from VAAS, the mild vaccines for EAPV and PaMoV are arranged for field tests in Vietnam. If the vaccines are proven to be effective in different places at different times, we can use them to fight against EAPV and PaMoV. Because of the co-infection by EAPV and PaMoV, we are developing a combined mild vaccine to cope with these two viruses. Since Prof. Yeh has developed a combined vaccine for melons before, we hope the same method can be applied to passion fruit, which will benefit the passion fruit industry in Taiwan and Vietnam.
Other Achievements of the Main Missions
1. The Promotion of Taiwanese Functional Foods in Vietnam
Since ASTIC was founded in 2017, promoting Taiwanese functional foods to ASEAN is also the main task of our center. In 2019, our team organized the Symposium on Functional Foods in VAAS and invited three major biotech companies in Taiwan, including MaxLuck Biotech Corp., Taiwan Leader Biotech Corp., and TCI Co., Ltd. Moreover, our partners in Vietnam invited local health officials to explain the application process of the import permit for functional foods, and a professor from the Vietnam National University of Agriculture introduced the production of traditional herbal medicine in Vietnam. The meeting was also attended by five companies and six government agencies in Vietnam. In total, 35 people attended the symposium, including professors, experts, and executives from Taiwan and Vietnam. It was a successful event, which paves the way for Taiwanese functional food to enter the Vietnamese market and to create more cooperation in the future.
Assisted by ASTIC, Taiwan Leader Biotech Corp. has successfully applied for Vietnam's import permits for three functional food products in July 2020 and two in January 2021. Based on this experience, our center will continue to assist MaxLuck Biotech Corp. to apply for Vietnam's import permit by the end of 2021. With the help from ASTIC, seven Taiwanese functional food products have reached the Vietnamese market in less than two years, which is a great success.
2. Talent Cultivation
Vietnamese talents including Thi-Thu-Yen Tran, Ngoc-Bich-Thi Tran, Duy-Hung Do, Xuan-Tung Ngo have joined Prof. Yeh's team in NCHU for many years. They have studied how to control the Papaya ringspot virus and passion fruit woodiness virus and achieved excellent results. Among them, Thi-Thu-Yen Tran and Duy-Hung Do have published their papers in international journals (Phytopathology, 2021. https://doi.org/10.1094/PHYTO-10-20-0481-R; https://doi.org/10.1094/PHYTO-06-21-0272-R). In addition, Vu Duy Minh, Nguyễn Nam Duong, and Hoang Manh Hung from Nafoods came to NCHU for four weeks of training to learn about virus detection techniques. In the future, these students and trainees will become R&D professionals in Vietnam's agricultural biotechnology industry and the main force for Taiwan-Vietnam cooperation.
With the five-year project between NCHU and UC Davis as well as the ASTIC plans under the Ministry of Science and Technology, Prof. Yeh has worked closely with Vietnam and provided them with a series of R&D measures for the passion fruit industry. It is crucial that agricultural cooperation requires our long-term efforts to achieve tangible results. Assisted by NCHU, Vietnam has established a virus-free passion fruit seedling farm and gained the ability to detect passion fruit viruses. The biggest achievement is that we turned Vietnam into the kingdom of passion fruit in Asia, with over 12,000 hectares of cultivation area. Through the long-term cooperation between NCHU and VAAS, we have created a rare New Southbound Policy model and achieved a win-win situation.
However, we need to develop strategies to control the passion fruit woodiness disease, otherwise, the flourishing passion fruit industry will fade away quickly one day. After five years of work, NCHU has developed mild vaccines for EAPV, PaMoV, and TelMV with the help of three Ph.D. students and one master student from Vietnam. Currently, the EAPV vaccine is ready for the field test, and the PaMoV and TelMV vaccines are being evaluated in the greenhouse. It is expected that these mild vaccines can help control the passion fruit viruses and continue to promote the passion fruit industry in Vietnam. In the meantime, Taiwan can receive the intellectual property revenue through technology export, creating a win-win situation for both Taiwan and Vietnam.