Parvovirus H1-induced tumor cell death enhances human immune response via crosspresentation of dendritic cells

Zeidler M, Cornelis J, Koch U, Woelfel T, Rommeleare J, Galle PR, Heike M, Moehler M., University of Mainz, I. Dept. Medicine

e-mail: maja.zeidler@web.de

Autonomous parvoviruses and their derivates are under evaluation as antitumor agents since they preferentially replicate and kill in vitro-transformed cells and reduce the incidence of spontaneous and implanted animal tumors. However, the oncolytic properties are not yet understood. Therefore, we analysed maturation and crosspriming of dendritic cells (DC) as well as CTL activation after phagocytosis of H1-induced tumor cell lysates by DC using human SK29Mel melanoma cells with autologous CTL clones.

Cell death was detected with Annexin V/Propidiumjodide during FACscan. For phagocytosis, PKH-2 stained immature DC were cocultured with PKH-26 stained H1-induced melanoma lysates and quantified via FACscan and microscopy. Comparably, FACscan was used to determine DC maturation. Crosspresentation of tumor cell antigens to CTL clones via DC were detected by IFNg-release with a HLA-A2 loss SK29Mel subclone.

Both, the HLA-A2 positive (SK29Mel-1) and HLA-A2 loss (SK29Mel-1.22) melanoma cell lines were equally susceptible to H1-induced cell killing. Monocyt-derived, immature DC pagocytosed H1-mediated lysates better than mechanically destroyed cells. These DC were more perceptive to late than to early H1 infected cell lysates. DC cocultured with late apoptotic H1 induced SK29Mel-1 cells presented typical markers of maturation and activation. Furthermore SK29Mel-1.22 activated DC confirmed crosspresentation to and activation of autologous CTL. Cytokine release of DC-CTL cocultures strengthend the Th1-response.

Thus, we showed to the first time that parvovirus-induced tumor cell killing stimulates DC and CTL. The immune system may rapidly detect and respond to H1-infected tumors, thus making the clinical perspectives of autonomous parvoviruses even more promising.