Fusion of mature dendritic cells and human T-lymphotropic virus type I infected T cells: its efficiency as an antigen-presenting cell.

Monocyte-derived dendritic cells (DCs) from adult T cell leukemia are impaired in taking up exogenous antigens. To overcome this impairment, we fused unpulsed DCs to human T-lymphotropic virus type I (HTLV-I)-infected CD4(+) T cells (fusion DC-T cells). The efficiency of fusion was 50% and the fusion cells expressed higher HLA-ABC and CD86 Ags than HTLV-I-infected DCs. The fusion DC-T cells stimulated autologous CD4(+) and CD8(+) T cells, but DCs fused to itself or PHA-blasts did not stimulate any subsets. The functionally highest fusion DC-T cells was obtained when a DC and HTLV-I-infected T cells were fused at a ratio of 3:1. Expression of HTLV-Igag Ag on CD4(+) T cells was up-regulated when infected in the presence of 8-azaguanine, and these fusion DC-T cells were quite efficient in induction of higher CD8(+) T cell response. The results suggest that fusion DC-T cells produce functionally competent Ag-presenting cells and may be a likely candidate for immunotherapeutic use.