Serum IL-18 and IL-18BP Levels in Patients with Chikungunya Virus Infection

Chikungunya virus infection has recently emerged in several countries. The inflammatory response is suggested to be involved in the pathology observed in this infectious disease. Interleukin-18 (IL-18) is an inducer of interferon-gamma (IFN-gamma) production and has been shown to play a role in several inflammatory diseases. IL-18 binding protein (IL-18BP) is a natural regulator of IL-18. In this study, we determined the levels of IL-18 and IL-18BP in patients with Chikungunya virus infection. Acute and convalescent sera were collected from each patient. The levels of both IL-18 and IL-18BP were measured by ELISA assays. IL-18 and IL-18BP levels were higher in patients than in controls. In addition, the level of IL-18 was higher in convalescent than in acute sera. However, the level of IL-18BP was lower in convalescent than in acute sera. These data suggest that production of both IL-18 and IL-18BP was induced following Chikungunya virus infection. IL-18BP was increased to regulate the activity of IL-18. The ratio of IL-18 to IL-18BP was higher in convalescent than in acute sera. The lower level of IL-18BP in convalescent sera was probably due to loss following IL-18 neutralization. Our data suggest that Chikungunya virus infection promotes the T helper-1 (Th-1) response by inducing IL-18 production. Manipulation of IL-18 and IL-18BP levels could be a promising therapeutic approach to alleviate symptoms in patients with Chikungunya virus infection.