O004 Using type III interferon to improve the efficacy of vaccine and oncolytic viral vectors
Introduction Vaccines based on replicating viral vectors that express foreign antigens can generate superior durable antibody and memory CD8 T cell responses compared to inactivated virus or recombinant protein, with the added benefit of potential needle-free intranasal administration. Despite these significant advantages, safety concerns related to viral vectors as vaccine platforms can be an issue with this approach. Replicating viral vectors are perceived as less safe alternatives compared to other immunization modalities, especially in the context of intranasal administration, where the potential exists for systemic virus spread from the lung. The type III interferons (IL-29, IL-28A, IL-28B; also known as IFN-lambda1, 2, and 3) play a critical role in protecting epithelial cells in the lung and gut from virus infection, and can also stimulate adaptive immunity. We therefore examined the ability of this cytokine family to improve the safety and efficacy of a viral vector by limiting its systemic spread and vector-associated pathological effects after intranasal delivery. Methods Vesicular stomatitis virus (VSV) based vectors are promising candidates for use as vaccines and oncolytic agents. We generated recombinant VSV vectors expressing mouse IL-28A either from the fifth position or the more highly expressing first position of the viral genome, and measured virus replication in cell culture and mice. Results We found that IL-28A is properly expressed, secreted, and active when produced by VSV-infected cells. In cell culture, expression of IL-28A from VSV attenuated virus replication in type III IFN-sensitive cells, but not in type III IFN-resistant cells. Following intranasal inoculation in mice, spread of the VSV.IL28A vector from the lung to the lymph nodes, spleen, blood, liver, and brain was significantly reduced compared to recombinant wild-type VSV. Despite this attenuation, the VSV.mIL28A vector generated virus-specific CD8 T cell and antibody responses in mice that were comparable to wild-type VSV. Conclusion These studies demonstrate the ability of the type III interferon cytokine family to improve the safety and efficacy of a clinically promising viral vaccine vector. These results may potentially also inform the enhancement of VSV oncolytic activity by increasing selectivity of the virus for type III IFN-resistant tumor cells.