Age-dependent enhancement of IFN-gamma responses to Plasmodium falciparum liver stage antigen-1 T cell epitopes.

We assessed the cellular immunological responses to two Plasmodium falciparum liver-stage antigen (LSA)-1-derived T-cell epitopes in healthy Gabonese children and adults. The N-terminal peptide, designated T1, induced interferon (IFN)-gamma production in peripheral blood mononuclear cells (PBMC) from a significantly lower proportion of children compared to adults, but both interleukin (IL)-10 and IL-12 were produced by similar proportions of PBMC from the two groups. The LSA-1 junction region peptide (LSA-J) also induced IFN-gamma in a lower, but in this case statistically non-significant, proportion of PBMC from children compared to adults, whilst the proportions producing either IL-10 or IL-12 were again similar. Higher amounts of both IFN-gamma and IL-10 were induced by LSA-J compared to T1. CD8+ T-cells were shown to be primarily responsible for the production of peptide-driven IFN-gamma. The results suggest a significant age-related increase in the proportion of individuals capable of producing IFN-gamma to the N-terminal T1 epitope, with a shift from a predominantly IL-10-led response in children.