TMV-peptide fusion vaccines induce cell-mediated immune responses and tumor protection in two murine models

Fusion of peptides to viral carriers has proven an effective method for improving cellular immunity. In this study we explore the ability of a plant virus, Tobacco mosaic virus (TMV), to stimulate cellular immunity by interacting directly with immune cells. Fluorescently labeled TMV was incubated in vitro with murine spleen or lymph node cells, and near quantitative labeling of lymphocytes was achieved after 2 h, which persisted for up to 48 h. Direct TMV uptake and upregulation of the CD86 activation marker was measured in nearly all dendritic cells (DCs) by flow cytometry. To demonstrate that TMV can also provide functional antigen delivery and immune stimulation in vivo, two well-characterized T-cell epitopes that provide protection against tumor challenge in mice were fused to TMV coat protein by genetic manipulation, or by chemical conjugation. Vaccination of C57BL/6 mice elicited measurable cellular responses by interferon gamma (IFN gamma) ELISpot and resulted in significantly improved protection from tumor challenge in both the EG.7-Ova and B16 melanoma models. From these results we conclude that TMV was an effective antigen carrier for inducing cellular immune responses to less than 1 microg of peptide.