Adjuvant activity of GP96 C-terminal domain towards Her2/neu DNA vaccine is fusion direction-dependent

Abstract

The Her2 is one of tumor-associated antigens (TAA), regarded as an ideal target of immunotherapy. DNA encoding full-length or truncated rat Her2/neu have shown protective and therapeutics potentials against Her2/neuexpressing mammary tumors. However, the efficacy of active vaccination is limited since Her2 is a self-tolerated antigen. Hence, new strategies are required to enhance both the quality and quantity of the immune response against Her2-expressing tumors. Many studies have used Her2/neu gene with cytokine or other molecules involved in regulation of immune response to enhance the potency of Her2/neu DNA vaccines. Some studies fused adjuvant gene to C-terminal domain of Her2/neu gene, while others fused the adjuvant gene N-terminally to Her2/neu gene, but no comparison on how direction of fusion could affect efficiency of DNA vaccine has ever been made. Based on previous reports demonstrating potent adjuvant activity of gp96 C-terminal domain, we chose it as adjuvant. The aim of this study was to investigate if direction of fusion could affect adjuvant activity of gp96 C-terminal domain or potency of Her2/neu DNA vaccination. To do so, we fused Cterminal domain of gp96 to downstream or C-terminal end of transmembrane and extracellular domain (TM+ECD) of rat Her2/neu and resultant immune response to DNA vaccination was evaluated. The results were compared with that of Nterminally fusion of gp96 C-terminal domain to TM+ECD of rat Her2/neu. Our results revealed that adjuvant activity of gp96 C-terminal domain is enhanced when fused Nterminally to TM+ECD of rat Her2/neu. It suggests that adjuvant activity of gp96 C-terminal domain towards Her2/ neu is fusion direction-dependent.

The Contribution of NT‐gp96 as an Adjuvant for Increasing HPV16 E7‐Specific Immunity in C57BL /6 Mouse Model

“…The dose and orientation of the antigen towards HSP in the fusion gene may have clinical implications for the design and optimization of HSP‐based vaccines [21, 29, 55, 56]. Regarding to the previous studies, the increasing amount of N‐terminal fragment of gp96 leads to rise in the percentage of the peptide‐specific T cells responses [21].…”

The critical roles of endoplasmic reticulum chaperones and unfolded protein response in tumorigenesis and anticancer therapies

“…Taken together, these studies demonstrate that the use of GRP94 as an antitumor vaccination can prevent cancer development. However, GRP94 vaccination in mice appears less promising in the treatment of established tumors 114,116,117 , and clinical trials across various types of tumors suggest that autologous tumor-derived GRP94 vaccination may have limited efficacy 118–121 .…”

Selection of Adjuvants for Enhanced Vaccine Potency

“…It has been shown that interaction of anti-CD4-binding site (CD4bs) Abs with HIV-1 gp120 induces conformation changes that lead to enhanced antigenicity and immunogenicity of neutralizing epitopes in the V3 loop and C1 regions of gp120 of several subtypes and the immune complexes as immunogens induced serum Abs to gp120 and V3 at significantly higher titers than those induced by the respective uncomplexed gp120s [377]. Fusion of the c-terminal domain of gp96 to transmembrane and extracellular domain of rat Her2/neu enhanced the immunogenicity of Her2/neuIt DNA vaccine [378]. It is possible that such an immunogenicity enhancement is due to increased rigidity of the protein antigen.…”