A single dose vectored Taenia solium vaccine

Taenia solium is the aetiological agent of neurocysticercosis in humans and is associated with a high frequency of epilepsy in endemic areas. Pigs are the almost exclusive natural animal intermediate host for T. solium and immunisation of pigs offers the opportunity for disease prevention. Despite the general difficulty of effective immunisation against complex parasites, Professor Lightowlers in Melbourne has developed a highly effective protein in adjuvant vaccine based on the TSOL18 antigen. Two doses of this vaccine lead to very high level protection of >98% in pigs in a variety of rural disease settings where the vaccine is most needed.

However, deployment of two doses of vaccine in pigs in such settings is proving highly logistically problematic and a single dose of this vaccine has been found to be insufficiently protective.

We propose here to assess for the first time the potential of a viral vectored adenovirus vaccine encoding the same TSOL18 antigen. Adenoviral vectors are known to provide excellent antibody responses with a single dose in a range of animal species, including pigs, and in humans, as illustrated by their use as a single dose vaccine in the Ebola rapid response vaccine programme in 2014. We propose to make adenoviral vectors for this Taenia antigen, test immune responses in mice initially and then critically in pigs. By comparing the immune response generated in pigs by a single dose of the new adenoviral vaccine to that generated by two doses of the existing protein in adjuvant vaccine, we will be able to determine whether a single dose adenoviral vaccine is a viable option for further development as a single dose vaccine for prevention of Taenia solium disease.

Project outcomes

As expected, very high antibody titres were detected in pigs immunized with TSOL 18 protein-based vaccine as a prime boost. However, antibody titres below the levels consistent with protection were induced in pigs that received a single dose of 1010 infectious units of ChAdOx-1 TSOL 18.

Therefore, adenovirus viral vectors expressing TSOL 18 are not suitable to immunise pigs against Taenia solium.