Abstract
The majority of routinely given vaccines require two or three immunisations for full protective efficacy. Single dose vaccination has long been considered a key solution to improving the global immunisation coverage. Recent infectious disease outbreaks have further highlighted the need for vaccines that can achieve full efficacy after a single administration. Viral vectors are a potent immunisation platform, benefiting from intrinsic immuno-stimulatory features while retaining excellent safety profile through the use of non-replicating viruses. We investigated the scope for enhancing the protective efficacy of a single dose adenovirus-vectored malaria vaccine in a mouse model of malaria by co-administering it with vaccine adjuvants. Out of 11 adjuvants, only two, biscor (R)-100 and CoVaccineHT (TM), enhanced vaccine efficacy and sterile protection following malaria challenge. The CoVaccineHT (TM) adjuvanted vaccine induced significantly higher proportion of antigen specific central memory CD8(+) cells, and both adjuvants resulted in increased proportion of CD8(+) T cells expressing the CD107a degranulation marker in the absence of IFN gamma, TNF alpha and IL2 production. Our results show that the efficacy of vaccines designed to induce protective T cell responses can be positively modulated with chemical adjuvants and open the possibility of achieving full protection with a single dose immunisation.