Screening for T cell-eliciting proteins of Japanese encephalitis virus in a healthy JE-endemic human cohort using recombinant baculovirus-infected insect cell preparations.

The analysis of cell-mediated immune responses in virus-exposed but healthy individuals may contribute to define the features of the T cell response associated with resistance. We report, for the first time, on adaptive T cell responses to 5 largest of the 10 proteins that together constitute 76% of the coding potential of the Japanese encephalitis virus (JEV) genome in a naturally exposed healthy JE-immune human cohort. Fixed and sonified whole cell preparations of insect cells individually expressing recombinant prM, E, NS1, NS3 and NS5 proteins of JEV were used in vitro to stimulate lymphocytes from individuals who had experienced subclinical JEV infections. NS3-specific memory T cells were detected in up to 86% of the JEV-infected cohort whereas prM, E and NS1 each elicited reactions in approximately 45% among individuals tested, suggesting that NS3 is an important target for JEV-specific cell-mediated immune responses. Responses to NS5, the largest viral protein were in contrast the poorest, seen in only 13% of the cohort. Moreover, NS3 stimulated interferon-gamma production in both CD4(+) and CD8(+) T cells indicating that a Th1 immune response to the NS3 protein may be a critical determinant of immune control of JEV infection.