[99, 100] Murine NKT cells are present in large amounts in the liver (10–30% of intra-hepatic T cells),[101] and mouse models have shown a pivotal role for NKT/iNKT cell activation in liver pathology during virus-induced and concanavalin A-induced hepatitis.[102, 103] In a closely related

manner, liver function is frequently affected in patients during DHF/DSS.[1, 16, 19] As the studies on the impact of iNKT activity on check details viral immunity continues to develop, iNKT cells will probably be found to contribute to the host response in different viral infections.[96] Their role during hepatitis C virus, a hepacivirus of the Flaviviridae family, has been investigated in humans, although conflicting data about the frequency and function of iNKT cells in both liver and blood have been reported.[102]

Some evidence also suggests the mast cell-mediated recruitment of NKT cells to sites of DENV infection.[104] In our experimental model of DENV-2 infection using the adapted P23085 strain, we consistently observed that mice lacking iNKT cells (Jα18−/− mice) were resistant to severe DENV infection.[70] Haemoconcentration and plasma leakage were strongly reduced in DENV-infected Jα18−/− mice compared with infected WT mice. In parallel, histopathological analysis of liver sections revealed that infected Jα18−/− mice developed less hepatic damage. Hence, in agreement with other studies aminophylline Selleckchem PD0332991 that demonstrated a detrimental role of iNKT cells in liver disease,[101, 103, 105, 106] our data strongly suggest that iNKT cells contribute to hepatic

injury during DENV infection. The viral load was significantly reduced in spleen and liver of Jα18−/− mice compared with WT animals. Previous findings have suggested that pro-inflammatory mediators favour DENV replication in vivo and in vitro,[107] so it is likely that in our experimental setting, iNKT cells indirectly favour virus replication by promoting inflammation. As the inflammatory response is strongly reduced in Jα18−/− mice, this positive feedback for viral replication would be down-regulated. Importantly, Jα18−/− mice reconstituted with purified iNKT cells from naive intra-hepatic leucocytes presented 80% lethality. The incomplete restoration of the WT phenotype could be due to an interfering effect of vNKT cells. In some disease conditions, vNKT cells and iNKT cells exert opposing functions in immune regulation.[96, 100] The exact mechanisms by which iNKT cells contribute to DENV pathogenesis are yet to be defined. It is possible that they act through an early production of inflammatory cytokines that are able to directly and/or indirectly promote injury.