Agonist anti-GITR antibody significantly enhances the therapeutic efficacy of Listeria monocytogenes-based immunotherapy

Rajeev Shrimali, Shamim Ahmad, Zuzana Berrong, Grigori Okoev, Adelaida Matevosyan, Ghazaleh Shoja E. Razavi, Robert Petit, Seema Gupta, Mikayel Mkrtichyan, Samir N. Khleif

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


Background: We previously demonstrated that in addition to generating an antigen-specific immune response, Listeria monocytogenes (Lm)-based immunotherapy significantly reduces the ratio of regulatory T cells (Tregs)/CD4+ and myeloid-derived suppressor cells (MDSCs) in the tumor microenvironment. Since Lm-based immunotherapy is able to inhibit the immune suppressive environment, we hypothesized that combining this treatment with agonist antibody to a co-stimulatory receptor that would further boost the effector arm of immunity will result in significant improvement of anti-tumor efficacy of treatment. Methods: Here we tested the immune and therapeutic efficacy of Listeria-based immunotherapy combination with agonist antibody to glucocorticoid-induced tumor necrosis factor receptor-related protein (GITR) in TC-1 mouse tumor model. We evaluated the potency of combination on tumor growth and survival of treated animals and profiled tumor microenvironment for effector and suppressor cell populations. Results: We demonstrate that combination of Listeria-based immunotherapy with agonist antibody to GITR synergizes to improve immune and therapeutic efficacy of treatment in a mouse tumor model. We show that this combinational treatment leads to significant inhibition of tumor-growth, prolongs survival and leads to complete regression of established tumors in 60% of treated animals. We determined that this therapeutic benefit of combinational treatment is due to a significant increase in tumor infiltrating effector CD4+ and CD8+ T cells along with a decrease of inhibitory cells. Conclusion: To our knowledge, this is the first study that exploits Lm-based immunotherapy combined with agonist anti-GITR antibody as a potent treatment strategy that simultaneously targets both the effector and suppressor arms of the immune system, leading to significantly improved anti-tumor efficacy. We believe that our findings depicted in this manuscript provide a promising and translatable strategy that can enhance the overall efficacy of cancer immunotherapy.

Original languageEnglish (US)
Article number64
JournalJournal for ImmunoTherapy of Cancer
Issue number1
StatePublished - Aug 15 2017
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2017 The Author(s).


  • Anti-GITR antibody
  • Co-stimulation
  • Immune tolerance
  • Immunotherapy
  • Listeria vaccine
  • Lm-LLO-E7


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