Abstract 4562: Exploring the immune stimulatory properties of oncolytic Newcastle Disease Virus

Newcastle Disease Virus (NDV) is an avian paramyxovirus, which has significant oncolytic activity against mammalian cancers. It is multi-modal in its anti-tumour activity and offers a tumour selective, self-propagating therapeutic with oncolytic activity and immunostimulatory properties. Within the tumour itself, NDV infection is able to modulate the immune suppressive microenvironment and induce positive anti-tumour inflammatory responses. Additionally, we have enhanced the immune modulatory properties of NDV by engineering the virus to express granulocyte/macrophage colony-stimulating factor (GM-CSF). To better understand the immune modulatory mechanisms by which NDV infection is able to alter the tumour microenvironment we investigated the responses of normal human PBMCs and isolated immune cell populations following NDV exposure. Using flow cytometry, cytokine and gene expression analysis we demonstrated activation of the innate immune cells and a robust type I IFN and pro-inflammatory response. 24 hours post infection, innate immune cells (macrophages, natural killer cells and dendritic cells) had upregulated cell surface activation markers and secreted high levels of cytokines in a dose-dependent fashion. Furthermore, by using NDV constructs encoding fluorescent proteins we showed, in a specific subset of myeloid cells, the preferential uptake of virus and subsequent self-limiting viral replication. In a co-culture system, these infected myeloid cells were able to function as ‘virus cellular carriers’ and were able to mediate the efficient transfer of infectious NDV to tumour cells resulting in their oncolytic death. To further investigate the ability of NDV to infect, spread and kill tumour cells in vivo, we utilised tissue slice cultures of fresh patient samples. These studies demonstrated virus replication and transgene expression in tumour slices, as well as the uptake of virus in a small fraction of specific cells in slices of normal liver. Moreover, evidence that NDV was able to alter the tumour microenvironment could be demonstrated in such cultures by sampling the culture supernatants over time. By investigating the immune modulatory properties of NDV in vitro and in vivo we will gain greater insight and understanding of the anti-cancer properties of NDV. This work will also help guide the selection of transgenes for next generation approaches to augment the inherent immunostimulatory properties of NDV, and help inform clinical dosing options