Intratumoral Infection with Murine Cytomegalovirus Synergizes with PD-L1 Blockade to Clear Melanoma Lesions and Induce Long-term Immunity

Dan A. Erkes, Guangwu Xu, Constantine Daskalakis, Katherine A. Zurbach, Nicole A. Wilski, Toktam Moghbeli, Ann Hill, Christopher M. Snyder

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

Cytomegalovirus is an attractive cancer vaccine platform because it induces strong, functional CD8 + T-cell responses that accumulate over time and migrate into most tissues. To explore this, we used murine cytomegalovirus expressing a modified gp100 melanoma antigen. Therapeutic vaccination by the intraperitoneal and intradermal routes induced tumor infiltrating gp100-specific CD8 + T-cells, but provided minimal benefit for subcutaneous lesions. In contrast, intratumoral infection of established tumor nodules greatly inhibited tumor growth and improved overall survival in a CD8 + T-cell-dependent manner, even in mice previously infected with murine cytomegalovirus. Although murine cytomegalovirus could infect and kill B16F0s in vitro, infection was restricted to tumor-associated macrophages in vivo. Surprisingly, the presence of a tumor antigen in the virus only slightly increased the efficacy of intratumoral infection and tumor-specific CD8 + T-cells in the tumor remained dysfunctional. Importantly, combining intratumoral murine cytomegalovirus infection with anti-PD-L1 therapy was synergistic, resulting in tumor clearance from over half of the mice and subsequent protection against tumor challenge. Thus, while a murine cytomegalovirus-based vaccine was poorly effective against established subcutaneous tumors, direct infection of tumor nodules unexpectedly delayed tumor growth and synergized with immune checkpoint blockade to promote tumor clearance and long-term protection.

Original languageEnglish (US)
Pages (from-to)1444-1455
Number of pages12
JournalMolecular Therapy
Volume24
Issue number8
DOIs
StatePublished - Aug 1 2016

ASJC Scopus subject areas

  • Medicine(all)
  • Molecular Medicine
  • Molecular Biology
  • Genetics
  • Pharmacology
  • Drug Discovery

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