title: Myxoma virus expressing a fusion protein of interleukin-15 (IL15) and IL15 receptor alpha has enhanced antitumor activity.
abstract: Myxoma virus, a rabbit poxvirus, can efficiently infect various types of mouse and human cancer cells. It is a strict rabbit-specific pathogen, and is thought to be safe as a therapeutic agent in all non-rabbit hosts tested including mice and humans. Interleukin-15 (IL15) is an immuno-modulatory cytokine with significant potential for stimulating anti-tumor T lymphocytes and NK cells. Co-expression of IL15 with the α subunit of IL15 receptor (IL15Rα) greatly enhances IL15 stability and bioavailability. Therefore, we engineered a new recombinant myxoma virus (vMyx-IL15Rα-tdTr), which expresses an IL15Rα-IL15 fusion protein plus tdTomato red fluorescent reporter protein. Permissive rabbit kidney epithelial (RK-13) cells infected with vMyx-IL15Rα-tdTr expressed and secreted the IL15Rα-IL15 fusion protein. Functional activity was confirmed by demonstrating that the secreted fusion protein stimulated proliferation of cytokine-dependent CTLL-2 cells. Multi-step growth curves showed that murine melanoma (B16-F10 and B16.SIY) cell lines were permissive to vMyx-IL15Rα-tdTr infection. In vivo experiments in RAG1-/- mice showed that subcutaneous B16-F10 tumors treated with vMyx-IL15Rα-tdTr exhibited attenuated tumor growth and a significant survival benefit for the treated group compared to the PBS control and the control viruses (vMyx-IL15-tdTr and vMyx-tdTr). Immunohistological analysis of the subcutaneous tumors showed dramatically increased infiltration of NK cells in vMyx-IL15Rα-tdTr treated tumors compared to the controls. In vivo experiments with immunocompetent C57BL/6 mice revealed a strong infiltrate of both NK cells and CD8+ T cells in response to vMyx-IL15Rα-tdTr, and prolonged survival. We conclude that delivery of IL15Rα-IL15 in a myxoma virus vector stimulates both innate and adaptive components of the immune system.
authors.affiliation: Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America.
authors.forename: Vesna
authors.initials: V
authors.lastname: Tosic
authors.affiliation: Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America.
authors.forename: Diana L
authors.initials: DL
authors.lastname: Thomas
authors.affiliation: Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America.
authors.forename: David M
authors.initials: DM
authors.lastname: Kranz
authors.affiliation: Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Jia
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Grant
authors.initials: G
authors.lastname: McFadden
authors.affiliation: Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America.
authors.forename: Joanna L
authors.initials: JL
authors.lastname: Shisler
authors.affiliation: Department of Pathobiology at College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America.
authors.forename: Amy L
authors.initials: AL
authors.lastname: MacNeill
authors.affiliation: Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America.
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Roy
mesh_terms: D000818:Animals; D002452:Cell Count; D002460:Cell Line; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D004274:DNA, Recombinant / Q000235:genetics; D005818:Genetic Engineering; D019409:Interleukin-15 / Q000235:genetics*; D053720:Interleukin-15 Receptor alpha Subunit / Q000235:genetics*; D007694:Killer Cells, Natural / Q000166:cytology / Q000276:immunology; D008545:Melanoma / Q000276:immunology / Q000473:pathology / Q000821:virology; D051379:Mice; D009233:Myxoma virus / Q000235:genetics* / Q000502:physiology*; D050504:Oncolytic Viruses / Q000235:genetics* / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000235:genetics*; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology
chemical_list: D004274:DNA, Recombinant; D019409:Interleukin-15; D053720:Interleukin-15 Receptor alpha Subunit; D011993:Recombinant Fusion Proteins