A dendritic cell-based assay for measuring memory T cells specific to dengue envelope proteins in human peripheral blood

Dengue envelope (E) protein is a dominant immune inducer and E protein-based vaccines elicited partial to complete protection in non-human primates. To study the immunogenicity of these vaccines in humans, an enzyme linked immunospot (ELISPOT) assay for measuring interferon gamma (IFN-gamma) production was developed. Cells from two subject groups, based on dengue-exposure, were selected for assay development. The unique feature of the IFN-gamma ELISPOT assay is the utilization of dendritic cells pulsed with E proteins as antigen presenting cells. IFN-gamma production, ranging from 53-513 spot forming units per million peripheral blood mononuclear cells (PBMCs), was observed in dengue-exposed subjects as compared to 0-45 IFN-gamma spot forming units in dengue-unexposed subjects. Further, both CD4(+) and CD8(+) T cells, and cells bearing CD45RO memory marker, were the major sources of IFN-gamma production. The assay allowed quantification of E-specific IFN-gamma-secreting memory T cells in subjects 9 years after exposure to a live-attenuated virus vaccine and live-virus challenge. Results suggested that the dendritic cell-based IFN-gamma assay is a useful tool for assessing immunological memory for clinical research. (C) 2011 Elsevier B.V. All rights reserved.