Intraspleen DNA inoculation elicits protective cellular immune responses

DNA immunization or inoculation is a recent vaccination method that induces both humoral and cellular immune responses in a range of hosts. Independen t of the route or site of vaccination, the transfer of antigen-presenting c ells (APC) or antigens into lymphoid organs is necessary. The aim of this i nvestigation was to test whether intraspleen (i.s.) DNA inoculation is capa ble of inducing a protective immune response. We immunized mice by a single i.s. injection of a DNA construct expressing the immunoglobulin (Ig) heavy -chain variable domain (V-H) in which the complementarity-determining regio ns (CDR) had been replaced by a Taenia crassiceps T-cell epitope, In these mice, immune reponses and protective effects elicited by the vaccine were m easured. We have shown here for the first time that i.s. DNA inoculation ca n induce protective cellular immune responses and activate CD8(+) T cells, Also, Ig V-H appeared to be the minimal delivery unit of "antigenized" Ig c apable of inducing T-cell activation in a lymphoid organ. The strategy of i ntroducing T-cell epitopes into the molecular context of the V-H domain in combination with i.s. DNA immunization could have important implications an d applications for human immunotherapy.