Construction and Characterization of a Recombinant Vaccinia Virus Expressing Murine Intercellular Adhesion Molecule-1: Induction and Potentiation of Antitumor Responses

Abstract

The intercellular adhesion molecule-1 (ICAM-1) has been associated with cellular migration into inflammatory sites and with facilitating interactions between lymphocytes and tumor targets in the pathway of cell-mediated cytotoxicity. More recently, ICAM-1 has become increasingly implicated in the costimulation of T cell functions, such as antigen-dependent T cell proliferation. Previous murine studies have shown that the introduction of the ICAM-1 gene into tumor cells using retroviral vectors led to enhanced antitumor responses. In this study, we report the construction, characterization, and immunological consequences of a recombinant vaccinia virus expressing murine ICAM-1. Vaccinia virus represents an attractive vector for the delivery of molecules such as ICAM-1 due to its wide host range, rapid infection, and functional expression of inserted gene products. The infection of tumor cells with this recombinant virus resulted in the expression of functional ICAM-1. Infected tumors provide accessory or secondary signals to lymphoblasts in vitro, resulting in enhanced cytokine production or alloreactive cytotoxic T lymphocyte (CTL) activity. In vivo, we demonstrated that weakly immunogenic syngeneic tumors, infected with and expressing rV-ICAM-1, were rejected by immunocompetent hosts. Furthermore, immunization with rV-ICAM-1-infected tumors resulted in the rejection of subsequent tumor challenge, providing evidence for recall response and immunological memory. These studies demonstrated the utility of a recombinant vaccinia virus to deliver and efficiently express ICAM-1 molecules on tumor cells for potential gene therapy and recombinant approaches to cancer immunotherapy. This paper examines an alternative “gene therapy” approach, in which the gene for intercellular adhesion molecule-1 (ICAM-1) was transiently introduced into an ICAM-1-negative tumor cell line by infection with a recombinant vaccinia virus (rV-ICAM-1). After infection with rV-ICAM-1, ICAM-1 on MC38 tumor cells was synthesized, and functional expression of recombinant ICAM-1 was demonstrated in vitro by its capacity to provide appropriate signals leading to efficient cytokine production (e.g., tumor necrosis factor-α) by primary cultures of concanavalin A-induced T lymphoblasts, and to enhance allospecific cytotoxic T lymphocyte activity. Syngeneic C57BL/6 mice that rejected a primary tumor challenge of rV-ICAM-1-infected MC38 also rejected a rechallenge of wild-type MC38 tumor cells at a distal site, up to 5 weeks after the initial administration of the immunogen. ICAM-1 expressed by the primary tumor immunogen was necessary for the development and maintenance of specific antitumor immunity.