Modification of CEA with both CRT and TAT PTD induces potent anti-tumor immune responses in RNA-pulsed DC vaccination

CEA vaccines

Carcinoembryonic antigen (CEA) is a glycosylated cell surface oncofetal protein involved in adhesion, proliferation, and migration that is highly upregulated in multiple carcinomas and has long been a promising target for cancer vaccination. This review summarizes the progress to date in the development of CEA vaccines, examining both pre-clinical and clinical studies across a variety of vaccine platforms that in aggregate, begin to reveal some critical insights. These studies demonstrate the ability of CEA vaccines to break immunologic tolerance and elicit CEA-specific immunity, which associates with improved clinical outcomes in select individuals. Approaches that have combined replicating viral vectors, with heterologous boosting and different adjuvant strategies have been particularly promising but, these early clinical trial results will require confirmatory studies. Collectively, these studies suggest that clinical efficacy likely depends upon harnessing a potent vaccine combination in an appropriate clinical setting to fully realize the potential of CEA vaccination.

mRNA vaccines in disease prevention and treatment

mRNA vaccines have emerged as highly effective strategies in the prophylaxis and treatment of diseases, thanks largely although not totally to their extraordinary performance in recent years against the worldwide plague COVID-19. The huge superiority of mRNA vaccines regarding their efficacy, safety, and large-scale manufacture encourages pharmaceutical industries and biotechnology companies to expand their application to a diverse array of diseases, despite the nonnegligible problems in design, fabrication, and mode of administration. This review delves into the technical underpinnings of mRNA vaccines, covering mRNA design, synthesis, delivery, and adjuvant technologies. Moreover, this review presents a systematic retrospective analysis in a logical and well-organized manner, shedding light on representative mRNA vaccines employed in various diseases. The scope extends across infectious diseases, cancers, immunological diseases, tissue damages, and rare diseases, showcasing the versatility and potential of mRNA vaccines in diverse therapeutic areas. Furthermore, this review engages in a prospective discussion regarding the current challenge and potential direction for the advancement and utilization of mRNA vaccines. Overall, this comprehensive review serves as a valuable resource for researchers, clinicians, and industry professionals, providing a comprehensive understanding of the technical aspects, historical context, and future prospects of mRNA vaccines in the fight against various diseases.

Protein transduction domain-mediated influenza NP subunit vaccine generates a potent immune response and protection against influenza virus in mice

The nucleoprotein (NP) is a highly conserved internal protein of the influenza virus, a major target for universal influenza vaccine. Our previous studies have proven NP-based subunit vaccine can provide partial protection in mice. It is reported that the protein transduction domain (PTD) TAT protein from human immunodeficiency virus-1 (HIV-1) is able to penetrate cells when added exogenous protein and could effectively enhance the immune response induced by the exogenous protein. In present study, the recombinant protein TAT-NP, a fusion of TAT and NP was effectively expressed in Escherichia coli and purified as a candidate component for an influenza vaccine. We evaluated the immunogenicity and protective efficacy of recombinant influenza TAT-NP vaccine by intranasal immunization. In vitro experiments showed that TAT-NP could efficiently penetrate into cells. Animal results showed that mice vaccinated with TAT-NP could not only induce higher levels of IgG and mucosal IgA, but also elicit a robust cellular immune response. Moreover, the TAT-NP fusion protein could significantly increase the protection of mice against lethal doses of homologous influenza virus PR8 and could also provide mice protection against a lethal dose challenge against heterosubtypic H9N2 and H3N2 influenza virus. In conclusion, the recombinant TAT-NP might be a universal vaccine candidate against influenza virus.

mRNA Cancer Vaccines-Messages that Prevail

During the last decade, mRNA became increasingly recognized as a versatile tool for the development of new innovative therapeutics. Especially for vaccine development, mRNA is of outstanding interest and numerous clinical trials have been initiated. Strikingly, all of these studies have proven that large-scale GMP production of mRNA is feasible and concordantly report a favorable safety profile of mRNA vaccines. Induction of T-cell immunity is a multi-faceted process comprising antigen acquisition, antigen processing and presentation, as well as immune stimulation. The effectiveness of mRNA vaccines is critically dependent on making the antigen(s) of interest available to professional antigen-presenting cells, especially DCs. Efficient delivery of mRNA into DCs in vivo remains a major challenge in the mRNA vaccine field. This review summarizes the principles of mRNA vaccines and highlights the importance of in vivo mRNA delivery and recent advances in harnessing their therapeutic potential.

Cell Type Preference of a Novel Human Derived Cell-Permeable Peptide dNP2 and TAT in Murine Splenic Immune Cells

Cell-permeable peptides (CPPs) have been widely studied as an attractive drug delivery system to deliver therapeutic macromolecules such as DNA, RNA, and protein into cells. However, its clinical application is still limited and controversial due to the lack of a complete understanding of delivery efficiency in target cells. Previously we identified and characterized the novel and superior CPP, named dNP2, and here we comparatively analyzed intracellular delivery efficiency of dNP2 and TAT in various immune cells of mouse spleen to demonstrate their cell type preference. dNP2- or TAT-conjugated fluorescent proteins were most efficiently taken up by phagocytic cells such as dendritic cells and macrophages while little protein uptake was seen by lymphocytes including T cells, B cells, and NK cells. Interestingly CD8⁺ lymphoid dendritic cells and CD62L^loCD44^hi memory like T cell subsets showed significantly better uptake efficiency in vitro and in vivo relative to other dendritic cells or T cells, respectively. In addition, activated macrophages, T cells, and B cells took up the proteins more efficiently relative to when in the resting state. Importantly, only dNP2, not TAT, shows significant intracellular protein delivery efficiency in vivo. Collectively, this study provides important information regarding heterogeneous intracellular delivery efficiency of CPPs such as dNP2 and TAT with cell type preference in the spleen needed for its application in phagocytic cells or activated immune cells.

MC32 tumor cells acquire Ag-specific CTL resistance through the loss of CEA in a colon cancer model

We previously reported that MC32 cells resist carcinoembryonic antigen (CEA) DNA vaccination by losing their antigen presentation to Ag-specific CTLs in the context of MHC class I antigens in a colon cancer therapeutic model. In this study, we selected 2 tumor cells, MC32-S2-2 and MC32-S4-2, which have the ability to form tumors in CEA DNA vaccine-immunized mice. Wild type MC32 cells grew significantly less in CEA-immunized mice (with Ag-specific CTL lytic activity) than in control mice (with no Ag-specific CTL lytic activity). However, MC32-S2-2 and MC32-S4-2 cells grew at a similar rate in both control and CEA-immunized mice, confirming their resistant status against CEA DNA vaccination. MC32-S2-2 and MC32-S4-2 cells were not susceptible to lysis by CEA-specific CD8+ T cells. Moreover, when MC32-S2-2 and MC32-S4-2 cells were used as stimulating agents of CEA-specific immune cells for IFN-γ production, these cells failed to stimulate the induction of Ag-specific IFN-γ, suggesting a loss of tumor cell recognition by Ag-specific immune cells. However, MC32-S2-2 and MC32-S4-2 cells expressed MHC class I antigens in a manner similar to that of wild type MC32 cells. Finally, Western blot assay confirmed that in MC32-S2-2 and MC32-S4-2 cells, CEA expression remained absent but mouse CEA was expressed. Taken together, these data show that MC32 cells may also be able to achieve resistance to CEA-specific CTLs by antigen loss in this model.

Development of oral CTL vaccine using a CTP-integrated Sabin 1 poliovirus-based vector system

We developed a CTL vaccine vector by modification of the RPS-Vax system, a mucosal vaccine vector derived from a poliovirus Sabin 1 strain, and generated an oral CTL vaccine against HIV-1. A DNA fragment encoding a cytoplasmic transduction peptide (CTP) was integrated into the RPS-Vax system to generate RPS-CTP, a CTL vaccine vector. An HIV-1 p24 cDNA fragment was introduced into the RPS-CTP vector system and a recombinant poliovirus (rec-PV) named vRPS-CTP/p24 was produced. vRPS-CTP/p24 was genetically stable and efficiently induced Th1 immunity and p24-specific CTLs in immunized poliovirus receptor-transgenic (PVR-Tg) mice. In challenge experiments, PVR-Tg mice that were pre-immunized orally with vRPS-CTP/p24 were resistant to challenge with a lethal dose of p24-expressing recombinant vaccinia virus (rMVA-p24). These results suggested that the RPS-CTP vector system had potential for developing oral CTL vaccines against infectious diseases.

A loss of antitumor therapeutic activity of CEA DNA vaccines is associated with the lack of tumor cells' antigen presentation to Ag-specific CTLs in a colon cancer model

Human colon cancers express carcinoembryonic antigen (CEA). Thus, CEA has been considered as a potential vaccine target for immune therapy against colon cancer. In this study, CEA DNA vaccines plus anti-4-1BB Abs treatment was found to increase Ag-specific CTL activity and antitumor protective responses to MC32 cells. However, CEA DNA vaccines alone displayed few antitumor therapeutic effects while significantly inducing Ag-specific CTL responses. Anti-4-1BB Abs alone displayed antitumor therapeutic effects. Intratumoral electroporation with IL-12 cDNA also showed antitumor therapeutic activity against MC32 cells in a CD8+ T cell-dependent and CEA-non-specific manner, suggesting that established MC32 cells are still susceptible to CTL-mediated killing. Finally, our in vitro assays (Western blot assay, IFN-γ, CTL and apoptosis assays, FACS analysis) and animal studies demonstrated that a lack of antitumor therapeutic activity of CEA DNA vaccines might result from acquisition of tumor cell resistance to Ag-specific CTL-mediated killing through the loss of tumor cells' antigen presentation to Ag-specific CTLs. Taken together, these data show that MC32 cells may resist CEA DNA vaccination by their loss of antigen presentation to CEA-specific CTLs in the therapeutic model.

Antigen-specific mRNA transfection of autologous dendritic cells

Several reports have described the use of tumor-extracted RNA as source of tumor antigen for the preparation of vaccines based on dendritic cells (DC) and its potential use for antigen-specific or polyvalent tumor vaccination. Upon transfection, RNA is transcribed into proteins that enter the cytoplasmic degradation pathway and can be presented by DC through class I major histocompatibility complex (MHC)-I, thus inducing specific T cell cytotoxic responses. In this chapter, we present a protocol to transfect murine dendritic cells with tumor mRNA by means of electroporation.

Cancer vaccines targeting carcinoembryonic antigen: state-of-the-art and future promise

Concurrent with the US FDA's approval of the first therapeutic cancer vaccine, and supported by mounting clinical evidence indicating that targeting carcinoembryonic antigen (CEA) can safely overcome pre-existing tolerance, a multitude of novel CEA cancer vaccines are now in various stages of development. Since cancer-driven immune suppression often limits the efficacy of vaccines, numerous strategies are being examined in both preclinical and clinical settings to overcome immunosuppressive elements, including the combined use of vaccines with certain chemotherapies, immune checkpoint inhibitors, small-molecule targeted therapies and radiation. This review discusses the current state and future direction of therapeutic cancer vaccines targeting CEA, based on advances achieved over the last 5 years.

RNA vaccines for anti-tumor therapy

The immune system is able to recognize tumor antigens and this has been the basis for the development of cancer immunotherapies. The immune system can be instructed to recognize and attack tumor cells by means of vaccination strategies. One such strategy involves the delivery of tumor antigen as genetic material. Herewith we describe the use of RNA encoding tumor antigens for vaccination purposes in tumor settings. RNA has features that are interesting for vaccination. Upon transfection, the RNA has no possibility of integration into the genome, and the tumor translated proteins enter the intrinsic antigen processing pathway thus enabling presentation by MHC-I molecules. This can specifically activate cytotoxic CD8 T cells that can attack and kill tumor cells. RNA can be delivered as a naked molecule for vaccination purposes or can be used to transfect dendritic cells. The combination of RNA technology with dendritic cell vaccination provides a powerful tool for cancer immunotherapies.

A suppressor of cytokine signaling 1 antagonist enhances antigen-presenting capacity and tumor cell antigen-specific cytotoxic T lymphocyte responses by human monocyte-derived dendritic cells

The suppressor of cytokine signaling 1 (SOCS1) has emerged as a critical inhibitory molecule for controlling the cytokine response and antigen presentation by dendritic cells (DCs), thereby regulating the magnitude of both innate and adaptive immunity. The aim of this study was to investigate whether the SOCS1 antagonist pJAK2(1001-1013) peptide can weaken or block the inhibition function of SOCS1 in DCs by evaluating the phenotype and cytokine production, antigen-presenting, and specific T-cell-activating capacities of DCs electroporated with human gastric cancer cell total RNA. Furthermore, STAT1 activation of the JAK/STAT signal pathway mediated by SOCS1 was analyzed by Western blotting. The results demonstrate that the SOCS1 antagonist pJAK2(1001-1013) peptide upregulated the expression of the maturation marker (CD83) and costimulatory molecule (CD86) of RNA-electroporated human monocyte-derived mature DCs (mDCs), potentiated the capacity of mDCs to induce T-cell proliferation, stimulated the secretion of proinflammatory cytokines, and enhanced the cytotoxicity of tumor cell antigen-specific CTLs activated by human gastric cancer cell total RNA-electroporated mDCs. Data from Western blot analysis indicate that STAT1 was further activated in pJAK2(1001-1013) peptide-loaded mDCs. These results imply that the SOCS1 antagonist pJAK2(1001-1013) peptide is an effective reagent for the enhancement of antigen-specific antitumor immunity by DCs.

Complexes of streptavidin-fused antigens with biotinylated antibodies targeting receptors on dendritic cell surface: a novel tool for induction of specific T-cell immune responses

The choice of tools that enable efficient targeting of exogenous antigens (Ag) for processing and presentation by professional Ag-presenting cells (APC) remains limited. This represents, indeed, a bottleneck in development of vaccines inducing specific T-cell responses. Here, we describe a novel strategy of Ag delivery into APCs. The Ag of choice is fused to the N- or C-terminus of streptavidin (SA) and tetrameric Ag-SA or SA-Ag fusion proteins are produced in E. coli and purified by 2-Iminobiotin-Agarose affinity chromatography. Alternatively, Ag-SA proteins are purified from urea extracts of E. coli inclusion bodies and refolded in vitro into functional tetramers. Complexes with biotinylated antibodies targeting cell surface receptors are formed and used to deliver the Ags of choice for processing and presentation by APCs and induction of Ag-specific CD4+ and CD8+ T-cell responses in vitro and in vivo.

Recombinant adenovirus-mediated Hsp70 gene expression inhibits tumor growth in a rat xenograft model of pancreatic cancer

AIM: To observe the effect of recombinant adenovirus Ad5-pCEA-Hsp70-mediated Hsp70 gene expression on tumor growth in a rat xenograft model of pancreatic cancer, and to analyze the underlying mechanism.

METHODS: A rat xenograft model of pancreatic cancer was established, and model animals were randomly divided into three groups, which were given Ad5-pCEA-Hsp70, Ad5-control and PBS treatment, respectively. Antitumor effect was evaluated by comparing tumor size at different time points among the three groups. ELISA was used to detect the peripheral blood levels of Hsp70 protein, INF-g, TNF-a and IL-6. HE staining was used to detect lymphocyte infiltration. Animal spleen mononuclear cells were isolated to determine the proportion of CD83+ cells by flow cytometry. Cell-killing ability of spleen lymphocytes was observed in vitro.

RESULTS: At 4, 6, and 8 weeks after treatment, tumor volume in the Ad5-CEA-Hsp70 group was significantly lower than that in the Ad5-control group and PBS group (724.4 mm³ ± 81.6 mm³vs 901.3 mm³ ± 103.9 mm³, 987.5 mm³ ± 126.0 mm³; 681.3 mm³ ± 64.9 mm³vs 1 270.6 mm³ ± 131.6 mm³, 1 398.5 mm³ ± 193.0 mm³; 648.0 mm³ ± 65.9 mm³vs 1 487.0 mm³ ± 243.0 mm³, 1 660.0 mm³ ± 167.0 mm3; all P < 0.01). The levels of Hsp70 protein and cytokines INF-g, TNF-a and IL-6 in peripheral blood in the Ad5-pCEA-Hsp70 group were significantly higher than those in the Ad5-control group and PBS group (all P < 0.01). Compared to the Ad5-control group and PBS group, Ad5-pCEA-Hsp70 group had more lymphocytic infiltration. The proportion of CD83+ cells in the Ad5-pCEA-Hsp70 group was significantly higher than that in the Ad5-control group and PBS group (10.8% ± 1.3% vs 5.1% ± 0.6%, 4.8% ± 0.6%; both P < 0.01). In the lymphocyte-mediated CTL experiment, when the cell ratio of effect: target was 1:1, there was no significant difference in the cell killing ability among the three groups (P > 0.05), but with the increase in the effect: target cell ratio, the cell killing ability in the Ad5-pCEA-Hsp70 group was significantly increased (P < 0.05, P < 0.01).

CONCLUSION: Hsp70 gene expression mediated by recombinant adenovirus Ad5-pCEA-Hsp70 could inhibit tumor growth in a rat xenograft model of pancreatic cancer via mechanisms that are related to the promotion of dentritic cell maturation, induction of cytokine secretion, and promotion of lymphocyte infiltration.

Tumor vaccination using messenger RNA: prospects of a future therapy

While the endeavor to vaccinate against cancer has been pursued for over 20 years, only recently was the first tumor vaccine approved. Among the different antigen formats assessed for vaccination, coding messenger RNA (mRNA) is emerging as a particularly attractive option. It can code for all types of transcript based proteins, is easy and cost efficient to produce, has a favorable safety profile and enables induction of combined immune responses. Within the last few years major developments have been achieved in this field. Clinical approaches use mRNA either for direct administration or for engineering of adoptively transferred dendritic cells. However, there are still challenges to be overcome for successful clinical application of mRNA-based immunotherapies.

RNA vaccines in cancer treatment

The Cancer Report from the World Health Organization states that in the year 2000 12% of all death cases worldwide were caused by cancer. In the western world, the cancer death rates are often devastating, being at about 25%. This fact stresses the urgency to find effective cures against malignant diseases. New approaches in the treatment of cancer focus on the development of immunotherapies to fight the disease. Besides other methods, the usage of tumor-specific RNA as part of vaccines is investigated lately. RNA, administered alone or used for transfection of dendritic cells, shows several advantages as a vaccine including feasibility, applicability, safeness, and effectiveness when it comes to the generation of immune responses. This review concentrates on results from in vitro experiments and recent trials using RNA vaccines to present an overview about this specific strategy.

The delivery of HBcAg via Tat-PTD enhances specific immune response and inhibits Hepatitis B virus replication in transgenic mice

Recent studies have indicated that the therapeutic vaccine based on enhancement of HBV-specific cytotoxic T-lymphocyte (CTL) activity may lead to viral clearance in chronically infected individuals. It is demonstrated that protein transduction domains (PTD) from HIV-1-Tat protein is able to enter cells when combined with exogenous antigens and induce specific CTL responses. We have previously testified that the expressed and purified fusion protein containing Tat-PTD47-57 and HBcAg could enter cytoplasm of dendritic cells, and enhance T cells response to generate HBcAg-specific CTLs efficiently in vitro. In the present study, we evaluated HBcAg-specific immune responses of PTD-HBcAg fusion protein in BALB/c mice and antiviral immunity in HBV transgenic mice. The studies showed that PTD-HBcAg not only induced significantly higher antibody responses, but also increased production of cytokine (IFN-gamma, IL-2, IL-4 and IL-10) compared to HBcAg alone and PBS. Moreover, PTD-HBcAg fusion protein increased significantly the percentages of IFN-gamma+CD8+ T cells and HBcAg-specific (CTL) responses. Also, enhancement of immune response induced by fusion protein reduced HBV DNA and HBsAg levels and decreased the expression of HBsAg in liver tissue of HBV transgenic mice. In conclusion, PTD-HBcAg fusion protein could enhance not only cell immune response but also humoral immune response, and induce robust specific CTL activity and therapeutic effects in HBV transgenic mice.

Protective anti-tumour immune responses by murine dendritic cells pulsed with recombinant Tat-carcinoembryonic antigen derived from Escherichia coli

Carcinoembryonic antigen (CEA) is over-expressed on various human cancer cells and has been the target of immunotherapies using dendritic cells (DCs) pulsed with CEA-specific RNA or peptides, or transduced by CEA-expressing adenovirus or vaccinia virus. Because activated DCs do not phagocytose soluble protein antigens efficiently and pure immature DCs are not obtained easily ex vivo, an efficacious whole CEA protein-loaded DC vaccine has not been reported. To improve the antigen delivery into DCs, we utilized CEA conjugated to a protein-transduction domain, human immunodeficiency virus transactivating Tat. Furthermore, we purified the truncated non-glycosylated CEA from Escherichia coli to overcome the safety concerns and immunosuppressive functions associated with the native CEA protein. Using confocal microscopy and fluorescence activating cell sorter analysis, we demonstrated that the Tat-CEA protein entered the cytoplasm of DCs efficiently within 10 min of co-culture, compared with the negligible amount of CEA into DCs 30 min later. CEA-specific T cell proliferation and cytotoxic T cell responses were enhanced significantly in mice immunized with Tat-CEA-pulsed DCs [DC (Tat-CEA)] compared with those immunized with CEA-pulsed DCs [DC (CEA)]. T helper type 1 responses were more prominent in the DC (Tat-CEA) immunized mice whose splenocytes secreted more interferon-gamma and less interleukin-4 than those from DC (CEA) immunized mice. In vivo, the DC (Tat-CEA) vaccine delayed tumour growth significantly and prolonged survival of tumour-bearing mice. These results suggest that protective epitopes are well preserved on bacteria-derived recombinant Tat-CEA. This strategy may provide a basic platform for DC-based anti-CEA vaccines that could be utilized in combination with advanced immune-enhancing therapeutics.

The heat shock protein 27 (Hsp27) operates predominantly by blocking the mitochondrial-independent/extrinsic pathway of cellular apoptosis

Heat shock protein 27 (Hsp27) is a molecular chaperone protein which regulates cell apoptosis by interacting directly with the caspase activation components in the apoptotic pathways. With the assistance of the Tat protein transduction domain we directly delivered the Hsp27 into the myocardial cell line, H9c2 and demonstrate that this protein can reverse hypoxia-induced apoptosis of cells. In order to characterize the contribution of Hsp27 in blocking the two major apoptotic pathways operational within cells, we exposed H9c2 cells to staurosporine and cobalt chloride, agents that induce mitochondria-dependent (intrinsic) and -independent (extrinsic) pathways of apoptosis in cells respectively. The Tat-Hsp27 fusion protein showed a greater propensity to inhibit the effect induced by the cobalt chloride treatment. These data suggest that the Hsp27 predominantly exerts its protective effect by interfering with the components of the extrinsic pathway of apoptosis.