Humoral And Cellular Immunity Against Angiogenesis Induced By A Fusion Vaccine Recruiting And Targerting Antigen Presenting Cells

Angiogenesis plays a central role in the process of growth and metastasisof primary solid tumors. Anti-angiogenesis is thought as an effective strategyfor cancer therapy. Vascular endothelial growth factor (VEGF) and itsreceptors (VEGFRs) are principal regulators of blood vessel formation.VEGFR2 transduces the major signals for angiogenesis. So, is a direct signaltransducer for pathological angiogenesis including cancer. Thus, VEGFR2itself and the signaling were thought to be critical targets for the suppressionof angiogenesis. Previous studies indicated that humoral or cellular immuneresponse to murine vascular endothelial growth factor 2(mFlk-1) were elicitedindependedly with different vaccines based the same extracelluar region ofmFlk-1. It's obvious that targets of humoral and cellular immune responseboth lie in extracellular region of mFlk-1 on which a new vaccine could bedesigned to induce both cellular and humoral immune response toantiangiogensis.Here we describe a novel genetic fusion DNA vaccination strategybased on the targeting of a modified mFlk-1 to antigen presenting cells(APCs), especially, to immature dendritic cells (iDCs), by a murine betadefensin2 (MBD2) protein. The fusion mFlk-1 then was internalized intoAPCs through the internalization receptor, MBD2, which thus enhanceantigen presentation and immune responses.The fusion protein MBD2-mFlk-1 kept the capacity of chemotaxis toiDCs. Inhibition of tumor growth was found in mice models immunized withpMBD2-mFlk-1 which indicated protective immunity was provoked. The pMBD2-mFlk-1 induced specific protective response may be long-lastingbecause inhibition of tumor growth was observed when LL/2 challenged 6months after last vaccination. Besides, inhibition of angiogenesis wasobserved in mice tumor tissue and an alginate-encapsulate tumor cell assay.Autoantibodies against mFlk-1 but not MBD2 from pMBD2-mFlk-1immunized mice were identified by Western blot analysis. T cells isolatedfrom mice immunized with pMBD2-mFlk-1 showed increased cytotoxicityagainst mFlk-1-positive target cells. The antitumor activity and the inhibitionof angiogenesis were acquired by the adoptive transfer of the purifiedimmunoglobulins or isolated TLs. Furthermore, the effects of the fusionvaccine were restrained by the depletion of CD4+ or CD8+ T lymphocytesand impaired in CD4^-/-,CD8^-/- and IgH^-/- mice, which indicated thatpMBD2-mFlk-1 vaccine works in part depend on humoral immune presponseand cellular immune response depended on CD8+ T lymphocytes also play animportant role.These results also indicated that covalent linkage of MBD2 and mFlk-1was necessary to elicit immune response to mFlk-1 and MBD2 could beexploited to enhance the cellular and humoral immune responses against othertumor associated antigens (TAAs) or self antigens. And, based previousstudies, the study further suggested that the breakdown of immune toleranceand different immune responses to the same self antigen might depend ondifferent antigen presenting ways.