The vaccine could save the lives of young elephants.

A trial of a vaccine against elephant endotheliotropic herpesvirus (EEHV) has found the vaccine to be safe for use in young Asian elephants.

According to an international team, the vaccine triggers a virus-fighting immune response, which could save the lives of elephants from the deadly virus.

The proof-of-concept study has been conducted by an international team, which included the University of Surrey, Chester Zoo and the Animal and Plant Health Agency (APHA). The vaccine was tested on three healthy adult elephants, in order to assess how safe it was.

All three elephants had a history of EEHV detection and pre-existing humoral immunity. These traits had proven consistent with latent infection in adult animals prior to the study.

None of the elephants had records of prior MVA-based vaccination in the context of cowpox prevention.

The vaccine was given in two stages: a viral vector with two EEHV proteins (EE2 and major capsid protein) followed by a booster with purified proteins and an adjuvant to strengthen the response.

To assess the efficacy of the vaccine, researchers took blood samples in various ways. This included whole transcriptome sequencing – marking the first time systematic immune profiling has been carried out in elephants.

The results of the study suggest that the vaccine could protect calves from EEHV, the leading cause of death in young elephants.

Close monitoring of the vaccinated elephants raised no concerns for either the prime or boost vaccines. There were no mild or moderate symptoms at any point during the study.

It was found to trigger a strong virus-fighting immune response by triggering two key types of immune cells: CD4+ and CD8+ T cells to mediate the immune system’s fight against viruses. Systems immunology analysis has also confirmed broad activation of anti-viral immunity.

Falko Steinbach, professor of veterinary immunology, said: “This is a landmark moment in our work to develop safe and efficacious vaccines. 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.”

Tanja Maehr, lead author of the study from APHA, said: “Our findings give real hope that vaccination can become a practical tool for preventing severe disease and death due to EEHV.

“The next step would be to trial the vaccine in calves and in range countries, so we can begin to protect those most at risk.”

The full study can be found in the journal Nature Communications.

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