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Invariant natural killer T (iNKT) cells are capable of rapid activation and
production of cytokines upon recognition of antigenic lipids presented by
CD1d molecules. They have been shown to play a significant role in many
viral infections and were observed to be highly activated in patients with
acute dengue infection. In order to characterize further their role in dengue
infection, we investigated the proportion of iNKT cells and their phenotype
in adult patients with acute dengue infection. The functionality of iNKT
cells in patients was investigated by both interferon (IFN)-g and interleukin
(IL)24 ex-vivo enzyme-linked immunospot (ELISPOT) assays following
stimulation with alpha-galactosyl-ceramide (aGalCer). We found that
circulating iNKT cell proportions were significantly higher (P 5 003) in
patients with acute dengue when compared to healthy individuals and were
predominantly of the CD41 subset. iNKT cells of patients with acute
dengue had reduced proportions expressing CD8a and CD161 when
compared to healthy individuals. The iNKT cells of patients were highly
activated and iNKT activation correlated significantly with dengue virusspecific immunoglobulin (Ig)G antibody levels. iNKT cells expressing Bcl-6
(P 5 00003) and both Bcl-6 and inducible T cell co-stimulator (ICOS)
(P 5 0006) were increased significantly in patients when compared to
healthy individuals. Therefore, our data suggest that in acute dengue
infection there is an expansion of highly activated CD41 iNKT cells, with
reduced expression of CD161 markers.
