Figure 1.

Immunity against DENV triggers pathogenesis. Primary infection with DENV triggers the release of several cytokines and chemokines together with the activation of cell-mediated immunity and humoral immunity. The reinfection, especially with a different serotype, induces the heightened threat of developing severe dengue (DHF). While the primary infection imparts the cross-reactive protective immunity, the secondary infection may be oppositely pathogenic. The direct role for DENV serotype cross-reactive antibodies is shown in this model during the severe dengue outbreak. Besides, the serotype-specific T cells prevails the primary infection; however, during the secondary infection, the memory T cells recognize the conserved epitopes and thereby increase together with naïve serotype, leading to the severe dengue. DENV: Dengue virus, DHF: Dengue hemorrhagic fever