1. ¹Abramson Family Cancer Research Institute, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
2. ²Department of Pathobiology, University of Pennsylvania School of Veterinary Medicine, Philadelphia, PA, USA
3. ³Department of Clinical Studies, University of Pennsylvania School of Veterinary Medicine, Philadelphia, PA, USA
4. ⁴Division of Oncology, Department of Pediatrics, Children's Hospital of Philadelphia, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
5. ⁵Oncology Service, Red Bank Veterinary Hospital, Red Bank, NJ, USA
6. ⁶Institute of Animal Neurology, University of Bern, Bern, Switzerland
7. ⁷Hematology-Oncology Division, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA, USA

Correspondence: Dr RH Vonderheide, Abramson Family Cancer Research Institute, University of Pennsylvania School of Medicine, 551 BRB II/III, 421 Curie Blvd, Philadelphia, PA 19104, USA. E-mail: rhv@mail.med.upenn.edu

⁸These authors contributed equally to this work.

Received 23 July 2007; Revised 11 December 2007; Accepted 17 January 2008; Published online 13 March 2008.

Abstract

Cell-based vaccination strategies to induce functional tumor-specific T cells in cancer patients have focused on using autologous dendritic cells. An alternative approach is to use RNA-loaded CD40 activated B cells (CD40-B) that are highly efficient antigen-presenting cells capable of priming naive T cells, boosting memory T-cell responses and breaking tolerance to tumor antigens. The use of tumor RNA as the antigenic payload allows for gene transfer without viruses or vectors and permits major histocompatibility complex (MHC)-independent, multiple-antigen targeting. Here, we use CD40L transfected K562 cells to generate functional CD40-B cells from the peripheral blood of humans and dogs. Testing of RNA-loaded CD40-B cells in dogs allows not only for its development in veterinary medicine but also for determination of its safety and efficacy in a large animal model of spontaneous cancer prior to initiation of human clinical trials. We found that CD40-B cells from healthy humans, healthy dogs and tumor-bearing dogs express increased levels of immune molecules such as MHC and CCR7. Moreover, RNA-loaded CD40-B cells induce functional, antigen-specific T cells from healthy dogs and dogs with lymphoma. These findings pave the way for immunotherapy trials using tumor RNA-loaded CD40-B cells to stimulate antitumor immunity in a large animal model of spontaneous neoplasia.