N-terminally fusion of Her2/neu to HSP70 decreases efficiency of Her2/neu DNA vaccine

Hashemi

Hassan

2011

Self Cite

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.

Section: Since Cd8supporting

confidence: 89%

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

Hashemi

Hassan

2011

Self Cite

“…We previously reported that N-terminally fusion of Her2/ neu to HSP70 (pHSP70/He2) decreased the efficiency of Her2/neu DNA vaccine (Pakravan et al 2010b). Tumor progression and IFN-γ/IL-4 levels were similar to that of pNT/Her2, but pHSP70/Her2 decreased Treg percentage at the tumor site and, importantly, increased survival rate.…”

Section: Discussionmentioning

confidence: 97%

Comparison of adjuvant activity of N- and C-terminal domain of gp96 in a Her2-positive breast cancer model

Hassan

2011

Self Cite

It has been frequently reported that gp96 acts as a strong biologic adjuvant. Some studies have even investigated adjuvant activity of the gp96 C-or N-terminal domain. The controversy surrounding adjuvant activity of gp96 terminal domains prompted us to compare adjuvant activity of gp96 C-or N-terminal domain toward Her2/neu, as DNA vaccine in a Her2/neu-positive breast cancer model. To do so, mice were immunized with DNA vaccine consisting of transmembrane and extracellular domain (TM + ECD) of rat Her2/neu alone or fused to N-or C-terminal domain of gp96. Treatment with Her2/neu fused to Nterminal domain of gp96 resulted in tumor progression, compared to the groups vaccinated with pCT/Her2 or pHer2. Immunological examination revealed that treatment with Her2/neu fused to N-terminal domain of gp96 led to significantly lower survival rates, higher interferon-γ secretion, and induced infiltration of CD4 + /CD8 + cells to the tumor site. However, it could not induce cytotoxic T lymphocyte activity, did not decrease regulatory T cell percentage at the tumor site, and eventually led to tumor progression. Our results reveal that gp96 N-terminal domain does not have adjuvant activity toward Her2/neu. It is also proposed that adjuvant activity and the resultant immune response of gp96 terminal domains may be directed by the antigen applied.

“…We previously (Pakravan et al 2010a) demonstrated that fusion of GP96 C-terminal to Her2 could raise IL-4/IFN-γ level, which was concomitant with better control of tumor growth. Another study revealed that administration of HSP70 and Her2 (Pakravan et al 2010b) led to tumor progression while IL-4/IFN-γ level was much more than that of GP96 C-terminal fused to Her2. Presumably, there is an optimum range and balanced level for IL-4/IFN-γ.…”

Section: Discussionmentioning

confidence: 99%

Co-administration of GP96 and Her2/neu DNA vaccine in a Her2 breast cancer model

Langroudi

Hajimoradi

et al. 2010

Self Cite

Heat-shock proteins have biochemical and immunological roles in chaperoning/signaling and activation of innate and adaptive immune responses, respectively. Their effect on the immune response is due to a phenomenon known as cross-priming of antigen, in which exogenous antigens are presented via MHC class I by antigen presenting cells. GP96 exerts adjuvant activity with some viral and bacterial antigens when applied in the form of a DNA vaccine. In this study, animals with Her2-expressing tumors were vaccinated by co-administration of GP96+ Her2/neu DNA vaccines. Analyses of the immune response, 2 weeks after the last immunization revealed decreased CD4+ CD25+ Foxp3+ naturally occurring regulatory T cells (Tregs) at the tumor site and increased IFN-γ/IL-4 level. Nevertheless, the graph of tumor size demonstrated a bi-phasic pattern in which partial control of tumor progression initially occurred, but finally its effectiveness was inversely affected by tumor size.