Immunization with alloantibodies-covered melanoma cells induces regional antitumor effects that become systemic when combined with 5-FU treatment

Highlights

• High titer allo-IgG against melanoma promote tumor immunogenicity of allo-IgG-B16.

• cDCs in lymph nodes capture and present tumor antigens released by allo-IgG-B16.

• Allo-IgG-B16, together with 5-FU, induce a systemic antitumor response.

Abstract

Alloantibodies, in particular immunoglobulin G (allo-IgG), confer a rejection advantage to tumors sharing the same major histocompatibility complex (MHC) in mice. However, when administrated intratumorally, this effect can only be achieved in combination with dendritic cells (DCs) activation. Here, we developed high titer allo-IgG by multiple rounds of immunization with allogenic B16 melanoma cells, which allows for the strong binding with B16 cells. We demonstrate that B16 cells incubated with these allo-IgG (referred to as allo-IgG-B16) become highly immunogenic, which release tumor antigens that are efficiently presented by classic DCs in lymph nodes (LNs). Injection of allo-IgG-B16 turns the tumor into an immune hot one and even elicits a systemic antitumor response when used together with 5-fluorouracil (5-FU). This systemic response is tumor-specific and relies on the critical site – LNs. Our findings provide a rationale for the use of allo-IgG in cancer treatment.

Introduction

The host immune response to major histocompatibility complex (MHC)-mismatched antigens, i.e., alloantigen, present on donor cells or organs (called donor graft), is called alloimmunization [1]. This process leads to the generation of alloantibodies produced by B cells that are capable of binding specifically to alloantigen [2]. When released into the bloodstream, alloantibodies may allow the immune system to destroy the donor organs, thereby strongly correlating with allograft rejection [3,4]. Conversely, the removal and prevention of alloantibodies production appears to correlate with allograft tolerance [5]. In a similar manner, allogenic tumor cells injected subcutaneously can be rejected by the host immune system through the production of alloantibodies, in particular IgG class (allo-IgG) [6]. When injected intravenously, e.g., B16 melanoma cells (H-2Kb^lo) $\to$ Balb/c hosts (H-2Kd), induction of allo-IgG may contribute significantly to the rapid and complete rejection of the secondary subcutaneous B16 [7].

As such, adoptive transfer of allo-IgG can lead to the rejection of syngeneic tumors [6]. However, the use of intratumoral injection of allo-IgG as a therapeutic intervention against established tumors fails to delay tumor growth [6]. This limitation can be bypassed by the combination of allo-IgG with dendritic cells (DCs) stimuli that induce tumor associated DCs activation and accumulation [6]. Presumably, the addition of DCs stimuli increased the IgG binding, resulting in tumor eradication [6]. This notion is supported by the uptake of ovalbumin-immune complexes (IC) by DCs, which were subsequently presented to ovalbumin-specific T cells to elicit strong antitumor immune responses [8,9]. However, the antitumor potential of the administration of tumor cells coated with allo-IgG to acquire the immunogenicity of tumor cells per se and its subsequent immune effects in vivo (i.e., the uptake and presentation of tumor-released antigens), was never tested experimentally.

Current limitations in the use of allo-IgG, i.e., natural antibodies, which are present in the circulation of healthy donors and are apparently produced without overt exposure to the corresponding alloantigens [6], make it particularly challenging to ascertain the effectiveness of allo-IgG to tumor-specific immunotherapy. Here, we developed high titer allo-IgG by multiple rounds of alloimmunization with weakly immunogenic B16 melanoma cells. When incubated with B16 cells, these allo-IgG formed an IC with B16 cells (i.e., allo-IgG-B16), conferred high immunogenicity to B16 cells, which released tumor antigens that can be taken up and presented efficiently by classical DCs. We demonstrate that injection of allo-IgG-B16 results in effective local tumor control and when used together with 5-fluorouracil (5-FU), also in systemic antitumor response that is tumor-specific (against contralateral B16 tumor, but not MC38 tumor).