Dengue virus-reactive CD8+ T cells display quantitative and qualitative differences in their response to variant epitopes of heterologous viral serotypes

Reactivation of serotype cross-reactive CD8(+) memory T lymphocytes is thought to contribute to the immunopathogenesis of dengue disease during secondary infection by a heterologous serotype. Using cytokine flow cytometry, we have defined four novel HLA-A*02-restricted dengue viral epitopes recognized by up to 1.5% of circulating CD8(+) T cells in four donors after primary vaccination. All four donors had the highest cytolkine response to the epitope NS4b 2353. We also studied the effect of sequence differences in heterologous dengue serotypes on dengue-reactive CD8(+) memory T cell cytolkine and proliferative responses. The D3 variant of a different NS4b epitope 2423 and the D2 variant of the NS4a epitope 2148 induced the largest cytokine response, compared with their respective heterologous sequences in all donors regardless of the primary vaccination serotype. Stimulation with variant peptides also altered the relative frequencies of the various subsets of cells that expressed IFN-gamma, TNF-alpha, MIP-1 beta, and combinations of these cytolkines. These results indicate that the prior infection history of the individual as well as the serotypes of the primary and heterologous secondary viruses influence the nature of the secondary response. These differences in the effector functions of serotype cross-reactive memory T cells induced by heterologous variant epitopes, which are both quantitative and qualitative, may contribute to the clinical outcome of secondary dengue infection.