Transgenic expression of CD40L and interleukin-2 induces an autologous antitumor immune response in patients with non-Hodgkin's lymphoma

The malignant B cells of non-Hodgkin's lymphoma (B-NHL cells) express peptides derived from tumor-specific antigens such as immunoglobulin idiotypes, and also express major histocompatibility complex antigens. However, they do not Express costimulatory molecules, which likely contributes to their protection from host antitumor immunity. To stimulate NHL-specific immune responses, we attempted to transfer the human CD40 ligand (hCD40L) gene to B-NHL cells and enhance their costimulatory potential. We found that an adenoviral vector encoding human CD40L (AdhCD40L) was ineffective at transducing B-NHL cells because these cells lack the coxsackievirus B-adenovirus receptor and alpha (v) integrins. However, preculture of the B-NHL cells with the human embryonic lung fibroblast line, MRC-5, significantly up-regulated expression of integrin alpha (v)beta3 and markedly increased their susceptibility to adenoviral vector transduction. After prestimulation, transduction with AdhCD40L increased CD40L expression on B-NHL cells from 1.3 +/-0.2% to 40.8 +/- 11.9%. Transduction of control adenoviral vector had no effect. Expression of transgenic human CD40L on these CD40-positive eel Is was in turn associated with up-regulation of other co-stimulatory molecules including B7-1/-2. Transduced B-NHL cells were now able to stimulate DNA synthesis of autologous T cells. However, the stimulated T cells were unable to recognize unmodified lymphoma cells, a requirement for an effective tumor vaccine. Based on previous results in an animal model, we determined the effects of combined use of B-NHL cells transduced with AdhCD40L and AdhlL2 vectors. The combination enhanced initial T-cell activation and generated autologous T cells capable of specifically recognizing and killing parental (unmodified) B-NHL cells via major histocompatibility complex-restricted cytotoxic T lymphocytes. These findings suggest that the combination of CD40L and IL2 gene-modified B-NHL cells will induce a cytotoxic immune response in vivo directed against unmodified tumor cells.