Enhanced therapeutic anti-tumor immunity induced by co-administration of 5-fluorouracil and adenovirus expressing CD40 ligand.

Bystander immune activation by chemotherapy has recently gained extensive interest and provided support for the clinical use of chemotherapeutic agents in combination with immune enhancers. The CD40 ligand (CD40L; CD154) is a potent regulator of the anti-tumor immune response and recombinant adenovirus (RAd)-mediated CD40L gene therapy has been effective in various cancer models and in man. In this study we have assessed the combined effect of local RAd-CD40L and 5-fluorouracil (5-FU) administration on a syngeneic MB49 mouse bladder tumor model. Whereas MB49 cells implanted into immunocompetent mice responded poorly to RAd-CD40L or 5-FU alone, administration of both agents dramatically decreased tumor growth, increased survival of the mice and induced systemic MB49-specific immunity. This combination treatment was ineffective in athymic nude mice, highlighting an important role for T cell mediated anti-tumor immunity for full efficacy. 5-FU up-regulated the expression of Fas and immunogenic cell death markers in MB49 cells and cytotoxic T lymphocytes from mice receiving RAd-CD40L immunotherapy efficiently lysed 5-FU treated MB49 cells in a Fas ligand-dependent manner. Furthermore, local RAd-CD40L and 5-FU administration induced a shift of myeloid-derived suppressor cell phenotype into a less suppressive population. Collectively, these data suggest that RAd-CD40L gene therapy is a promising adjuvant treatment to 5-FU for the management of bladder cancer.

The T-cell pool is anergized in patients with multiple sclerosis in remission.

Relapsing-remitting multiple sclerosis (RRMS) is a complex autoimmune disease of the central nervous system with oscillating phases of relapse and remission. RRMS has been considered to be driven by T helper type 1 (Th1) lymphocytes but new data indicate the involvement of Th17 responses. In the present study, blood samples from patients (n=48) and healthy individuals (n=44) were evaluated for their immunological status. T cells from patients with RRMS expressed high levels of the activation marker CD28 (P<0.05) and secreted both interferon-gamma (CD8: P<0.05) and interleukin-17 upon polyclonal mitogen or myelin oligodendrocyte glycoprotein antigen stimulation. However, T cells from patients with RRMS in remission, in contrast to relapse, had poor proliferative capacity (P<0.05) suggesting that they are controlled and kept in anergy. This anergy could be broken with CD28 stimulation that restored the T-cell replication. Furthermore, the patients with RRMS had normal levels of CD4(+) Foxp3(+) T regulatory cells but the frequency of Foxp3(+) cells lacking CD127 (interleukin-7 receptor) was lower in patients with MS (mean 12%) compared to healthy controls (mean 29%). Still, regulatory cells (CD25(+) sorted cells) from patients with RRMS displayed no difference in suppressive capacity. In conclusion, patients in relapse/remission demonstrate in vitro T-cell responses that are both Th1 and Th17 that, while in remission, appear to be controlled by tolerogenic mechanisms yet to be investigated.

A hexon and fiber-modified adenovirus expressing CD40L improves the antigen presentation capacity of dendritic cells.

CD40 ligand (CD40L), a strong stimulator of Th1 immune responses, acts via dendritic cells to trigger T-cell activation. AdCD40L therapy introduces the CD40L gene into the tumor microenvironment with an adenoviral vector and has shown promising results in experimental tumor models, dogs, and patients (phase I-II trials). The transduction efficiency of AdCD40L is dependent on the expression of CAR (coxsackie/adenovirus adhesion receptor), which is commonly downregulated on tumor cells. To enhance transduction efficiency, and therefore the therapeutic efficacy, a double-modified adenovirus was developed. The double-modified Ad5PTDf35(mCD40L) had a protein transduction domain (PTD) inserted into the hexon protein and the virus fiber is switched from serotype 5 to serotype 35. These modifications enable transduction of a wider range of cell types. In comparison with Ad5(mCD40L), Ad5PTDf35(mCD40L) showed increased transduction capacity on a variety of murine cells. Furthermore, antigen presentation was improved after transduction with Ad5PTDf35(mCD40L). This was demonstrated in an antigen presentation assay, both in vitro and in vivo, in which transduced dendritic cells were loaded with suboptimal concentrations of the human gp100 peptide and allowed to interact with gp100-specific transgenic T cells (pmel). Finally, Ad5PTDf35(mCD40L) could delay tumor growth in a murine cancer model at a particle load, wherein therapeutic efficacy of the Ad5(mCD40L) vector was lost. Hence, the Ad5PTDf35(CD40L) vector holds great promise as a second-generation immune stimulatory therapy, as it not only targets tumor cells but also antigen-presenting cells that are, among other cells, present in the tumor microenvironment.