Sequential production of cytokines by dengue virus-infected human peripheral blood leukocyte cultures

The study was undertaken to elucidate the sequence of appearance of T helpe r (Th)l- and Th2-type cytokines in human peripheral blood leucocyte culture s infected in vitro with dengue type 2 virus. Commercial sandwich enzyme-li nked immunosorbent assay kits were used to assay the levels of tumour necro sis factor-alpha (TNF-alpha), interferon-gamma (IFN- gamma), interleukin (I L)-2, IL-4, IL-5, IL-6, and IL-10 in culture supernatants. Culture supernat ants were also screened for the cytotoxic factor and the dengue virus titre s determined. The cytokines that appeared in the culture supernatants on th e first day post-infection (p.i.) were cytotoxic factor, TNF-alpha, IL-2, a nd IL-6; their levels were highest on the second day p.i. IFN-gamma appeare d on the second day with a peak on the third day p.i. The levels of these c ytokines declined quickly, except for human cytotoxic factor (hCF) and IL-2 . The cytokines that appeared later were IL-10 and IL-5 on the fourth day a nd IL-4 on the sixth day p.i. Dengue virus replicated in the peripheral blo od leucocyte (PBL) cultures and was present throughout the course of the st udy. The findings of the present study show that dengue virus induced a pre dominant Th1-type cytokine response during the first 3 days of infection of PBL cultures that was replaced by a Th2-type response later. (C) 1999 Wile y-Liss, Inc.