Interleukin-15 enhances host protection against acute Toxoplasma gondii infection in T-cell receptor alpha-/-deficient mice

A potential role for T-cell receptor (TCR)-gamma delta cells in response to Toxoplasma gondii has been described. This study was undertaken to evaluat e whether exogenous rIL-15 can enhance the production of gamma delta T cell s in response to infection with T. gondii. For this, C57BL/6 and TCR alpha- gene deficient mice (alpha-/-) were vaccinated with Toxoplasma lysate antig en (TLA) in combination with interleukin (IL)-15. The cellular and humoral immune response was assessed following immunization. Administration of IL-1 5/TLA to alpha-/-mice lengthened survival time post lethal challenge. Sever al immunological parameters were increased in the alpha-/-mice following im munization with IL-15/TLA including serum immunoglobulin (Ig)GI and IgG2a a ntibody titres and splenocyte lymphoproliferation in response to parasite a ntigen. Further, the CTL response to parasite infected target cells as well as the production of interferon gamma was enhanced by IL-15/TLA administra tion in the alpha-/-mice. These observations indicate that the gamma delta T cells response to this parasite can be enhanced by the administration of exogenous IL-15 in the presence of parasite lysate antigen.