Demarcated thresholds of tumor-specific CD8 T cells elicited by MCMV-based vaccine vectors provide robust correlates of protection

Elham Beyranvand Nejad, Robert B. Ratts, Eleni Panagioti, Christine Meyer, Jennifer D. Oduro, Luka Cicin-Sain, Klaus Früh, Sjoerd H. Van Der Burg, Ramon Arens

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


Background: The capacity of cytomegalovirus (CMV) to elicit long-lasting strong T cell responses, and the ability to engineer the genome of this DNA virus positions CMV-based vaccine vectors highly suitable as a cancer vaccine platform. Defined immune thresholds for tumor protection and the factors affecting such thresholds have not well been investigated in cancer immunotherapy. We here determined using CMV as a vaccine platform whether critical thresholds of vaccine-specific T cell responses can be established that relate to tumor protection, and which factors control such thresholds. Methods: We generated CMV-based vaccine vectors expressing the E7 epitope and tested these in preclinical models of HPV16-induced cancer. Vaccination was applied via different doses and routes (intraperitoneal (IP), subcutaneous (SC) and intranasal (IN)). The magnitude, kinetics and phenotype of the circulating tumor-specific CD8 + T cell response were determined. Mice were subsequently challenged with tumor cells, and the tumor protection was monitored. Results: Immunization with CMV-based vaccines via the IP or SC route eliciting vaccine-induced CD8 + T cell responses of > 0.3% of the total circulating CD8 T cell population fully protects mice against lethal tumor challenge. However, low dose inoculations via the IP or SC route or IN vaccination elicited vaccine-induced CD8 + T cell responses that did not reach protective thresholds for tumor protection. In addition, whereas weak pre-existing immunity did not alter the protective thresholds of the vaccine-specific T cell response following subsequent immunization with CMV-based vaccine vectors, strong pre-existing immunity inhibited the development of vaccine-induced T cells and their control on tumor progression. Conclusions: This study highlight the effectiveness of CMV-based vaccine vectors, and shows that demarcated thresholds of vaccine-specific T cells could be defined that correlate to tumor protection. Together, these results may hold importance for cancer vaccine development to achieve high efficacy in vaccine recipients.

Original languageEnglish (US)
Article number25
JournalJournal for immunotherapy of cancer
Issue number1
StatePublished - Jan 31 2019
Externally publishedYes


  • CMV-based vaccine vector
  • Cancer
  • Pre-existing immunity
  • T cells

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology
  • Molecular Medicine
  • Oncology
  • Pharmacology
  • Cancer Research


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