Researchers have achieved a major breakthrough in wildlife conservation with the successful development and testing of the world's first vaccine against elephant endotheliotropic herpesvirus (EEHV), a devastating pathogen that represents a leading cause of death in young Asian elephants. The international collaboration, led by the University of Surrey in partnership with Chester Zoo and the Animal and Plant Health Agency, demonstrated that the vaccine is both safe and capable of triggering robust antiviral immune responses in adult elephants.
Published in Nature Communications, the proof-of-concept study marks a watershed moment in efforts to combat a viral threat that has long challenged elephant conservation programs globally. The trial was conducted on adult elephants at Chester Zoo, where researchers observed no adverse side effects while documenting strong activation of key immune pathways.
Innovative Two-Step Vaccination Approach
The vaccine employs a sophisticated two-step protocol designed to maximize immune response while ensuring safety. The initial dose utilizes a viral vector platform to deliver two critical EEHV proteins—EE2 and the major capsid protein—enabling the immune system to recognize and mount defenses against these viral components. This is followed by a booster injection containing purified versions of these proteins combined with an adjuvant to intensify and solidify the immune response.
"This is a landmark moment in our work to develop safe and efficacious vaccines," said Professor Falko Steinbach, senior author of the study and Professor of Veterinary Immunology at the University of Surrey. "For the first time, we have shown in elephants that a vaccine can trigger the type of immune response needed to protect them against EEHV."
Groundbreaking Immune System Analysis
One of the study's most significant innovations was the use of whole transcriptome sequencing to comprehensively profile immune responses at the molecular level—an approach never before applied to elephants. This cutting-edge methodology allowed researchers to identify which immune pathways were activated and understand how the vaccine orchestrates the body's viral defense mechanisms.
The analysis revealed pronounced activation of both CD4+ "helper" T cells and CD8+ "killer" T cells, crucial components in virus eradication and immune memory formation. Systems immunology analysis, conducted through a partnership between the University of Surrey and São Paulo, confirmed broad activation of antiviral immunity pathways.
Conservation Impact and Future Directions
The implications for elephant conservation are profound, particularly given that EEHV disproportionately affects calves—the most vulnerable and valuable members of both captive and wild populations. By potentially preventing this devastating disease in young elephants, the vaccine could dramatically reduce mortality rates and enhance population sustainability.
"Our findings give real hope that vaccination can become a practical tool for preventing severe disease and death due to EEHV," said Dr. Tanja Maehr, lead author of the study from the Animal and Plant Health Agency. "The next step could be to trial the vaccine in calves and in range countries, so we can begin to protect those most at risk."
Dr. Katie Edwards, Lead Conservation Scientist at Chester Zoo, reflected on the significance of the achievement: "This vaccine has been in development for several years and was first delivered to an elephant here at Chester Zoo in 2021. This publication marks a watershed moment. EEHV has taken the lives of so many elephants, both in human care and in the wild, but this vaccine offers hope."
Broader Scientific Implications
The success of this vaccine establishes a precedent for future wildlife disease interventions by demonstrating how modern immunological techniques, including viral vector technology and transcriptomic profiling, can be applied to complex viral threats in non-model species. The collaborative approach between zoological institutions, academic researchers, and government agencies showcases the vital role such partnerships play in addressing emerging conservation challenges.
The research team plans to expand trials to include juvenile elephants and evaluate the vaccine's effectiveness in elephant range countries across Asia, where natural EEHV outbreaks continue to threaten wild populations. Should subsequent studies confirm these initial findings, widespread vaccination could emerge as an indispensable tool in comprehensive strategies to protect Asian elephant populations worldwide.
