Improved T cell responses to Plasmodium falciparum circumsporozoite protein in mice and monkeys induced by a novel formulation of RTS,S vaccine antigen.

Protection against Plasmodium falciparum sporozoite infection can be achieved by vaccination with the recombinant circumsporozoite protein-based vaccine RTS,S formulated with the AS02A Adjuvant System. Since this protection is only partial and wanes over time, we have developed a new RTS,S-based vaccine adjuvanted with AS01B. RTS,S/AS01B-induced high specific antibody titers and increased the frequency of mouse CD4(+) and CD8(+) T cells expressing IFN-gamma, and of monkey CD4(+) T cells expressing IL-2 and/or IFN-gamma and/or TNF-alpha upon stimulation with vaccine antigens. Our data provides clear evidence that combining RTS,S antigen with a potent adjuvant induces strong humoral and cellular responses in vivo.