Antigen-specific IL-2 secretion correlates with NK cell responses after immunization of Tanzanian children with the RTSS/AS01 malaria vaccine

摘要

RTS,S/AS01, a vaccine targeting pre-erythrocytic stages of Plasmodium falciparum, is undergoing clinical trials. We report an analysis of cellular immune response to component antigens of RTS,S – hepatitis B surface antigen (HBs) and P. falciparum circumsporozoite (CS) protein – among Tanzanian children in a Phase IIb RTS,S/AS01E trial. RTS,S/AS01 E vaccinees make stronger T cell IFN-γ, CD69 and CD25 responses to HBs peptides than do controls, indicating that RTS,S boosts pre-existing HBs responses. T cell CD69 and CD25 responses to CS and CS-specific secreted IL-2, were augmented by RTS,S vaccination. Importantly, more than 50% of peptide-induced IFN-γ⁺ lymphocytes were NK cells and the magnitude of the NK cell CD69 response to HBs peptides correlated with secreted IL-2 concentration. CD69 and CD25 expression and IL-2 secretion may represent sensitive markers of RTS,S-induced, CS-specific T cells. The potential for T cell-derived IL-2 to augment NK cell activation in RTS,S-vaccinated individuals, and the relevance of this for protection, needs to be explored further.