Abstract
Mammaglobin-A (MamA) is overexpressed in 40–80% of all human breast cancers. Recent phase I clinical trials of the MamA DNA vaccine showed encouraging safety outcomes. However, this vaccine elicited only a modest increase in MamA specific CD8+T lymphocyte (CTL) activation. As vaccine adjuvants play a critical role in enhancing the immunotherapeutic efficiency of vaccines, we tested the potential role of three synthetic CpG oligodeoxynucleotides (ODN2216—class A ODN, ODN2006—class B ODN, and ODN M362—class C ODN) to further enhance MamA specific CTL responses. Towards this, naïve CD8+T cells were obtained from healthy HLA-A2+ human donors. The HLA-A2 specific immunodominant epitope of MamA, MamA2.1 (LIYDSSLCDL), was utilized to activate naïve CD8+T cells. The THP-1 (HLA-A2+) cells were used as antigen presenting cells to stimulate naïve CD8+T cells along with (or without) co-treatment of various ODNs mentioned above. Activation of naïve CD8+T cells with the MamA2.1 peptide along with ODNs demonstrated enhanced MamA specific CTL mediated cytotoxicity on AU565 (HLA-A+/MamA+) breast cancer cells following co-treatment with ODN2006 and M362 compared to ODN2216 or MamA2.1 peptide alone. However, no significant cytotoxicity was noted upon treatment of MamA2.1 activated CTLs on MCF7 (HLA-A+/MamA−) cells, suggesting that the activation of CTLs is specific to the MamA antigen. Functional characterization studies demonstrated specific IL-12 mediated cross-talk between TLR-6 and -9 in THP-1 cells following stimulation with ODN2006 and M362, which was critical for the final cytotoxic activation of CD8+T lymphocytes. Based on these data, we conclude that ODN2006 and ODN M362 exerted a strong adjuvant effect through induction of the initial innate immune response through TLR9 upregulation followed by enhanced MamA specific CTL dependent adaptive immune responses. Our current data provide evidence for the application of Class-B/-C-CpG-ODNs as potential vaccine adjuvants towards enhancing the success of MamA based breast cancer vaccination.
Highlights
Cancer facts and figures (2018) estimate that breast cancer accounts for 15.5% of all newly diagnosed cancers in the United States [1]
In view of the limitations in performing full-fledged murine studies due to absence of murine breast cancer MamA ortholog, in this communication, we studied the impact of co-treatment of ODNs with the HLA-A2 restricted MamA peptide (MamA2.1 peptide) to characterize the potential activation and the effector capabilities of naïve CD8+T lymphocytes (CTLs) collected from HLA-A2+ healthy human subjects
We stimulated the naïve CD8+T cells collected from healthy HLA-A2 human subjects for five days with ODNs and MamA2.1-peptide presented by ODN-pretreated THP-1 cells
Summary
Cancer facts and figures (2018) estimate that breast cancer accounts for 15.5% of all newly diagnosed cancers in the United States [1]. Advances in the understanding of molecular biology and immunology provide an important futuristic application of DNA and peptide-based vaccines as viable long-term anti-cancer immunotherapeutic strategies. Recent availability of relatively low-cost recombinant plasmid development tools and high-throughput strategies to efficiently identify novel tumor associated antigens has significantly reduced the cost and the time involved in DNA vaccine preparation [2]. The long-lasting therapeutic success of a DNA vaccine depends upon the ability of the transfected gene coding for specific tumor associated antigens (TAA) in the plasmid backbone to efficiently activate antigen specific cytotoxic and memory CD8+T lymphocytes [3]. We recently proposed a “five-force immune hypothesis” to identify and develop various strategies towards the success of anti-cancer vaccine therapy [4]. Vaccine adjuvants play a critical role by acting as “indirect activators” to supplement immunogenicity and efficiency of DNA vaccines
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