Combining tumor-targeted superantigens with interferon-alpha results in synergistic anti-tumor effects

Innate immune suppression by SARS-CoV-2 mRNA vaccinations: The role of G-quadruplexes, exosomes, and MicroRNAs

The mRNA SARS-CoV-2 vaccines were brought to market in response to the public health crises of Covid-19. The utilization of mRNA vaccines in the context of infectious disease has no precedent. The many alterations in the vaccine mRNA hide the mRNA from cellular defenses and promote a longer biological half-life and high production of spike protein. However, the immune response to the vaccine is very different from that to a SARS-CoV-2 infection. In this paper, we present evidence that vaccination induces a profound impairment in type I interferon signaling, which has diverse adverse consequences to human health. Immune cells that have taken up the vaccine nanoparticles release into circulation large numbers of exosomes containing spike protein along with critical microRNAs that induce a signaling response in recipient cells at distant sites. We also identify potential profound disturbances in regulatory control of protein synthesis and cancer surveillance. These disturbances potentially have a causal link to neurodegenerative disease, myocarditis, immune thrombocytopenia, Bell's palsy, liver disease, impaired adaptive immunity, impaired DNA damage response and tumorigenesis. We show evidence from the VAERS database supporting our hypothesis. We believe a comprehensive risk/benefit assessment of the mRNA vaccines questions them as positive contributors to public health.

Granzyme B and perforin produced by SEC2 mutant-activated human CD4+ T cells and CD8+ T cells induce apoptosis of K562 leukemic cells by the mitochondrial apoptotic pathway

Staphylococcal enterotoxin C2 (SEC2), a classical representative of superantigens, activates T cells that produce massive cytokines. This characteristic makes SEC2 a promising candidate drug for cancer immunotherapy. Previous study showed that ST-4, a SEC2 mutant, enhanced recognition of mouse T-cell receptor Vβ regions, and activated the increased number of T cells that produced more cytokines. However, the underlying molecular mechanism for stimulation of human peripheral blood mononuclear cells (PBMCs) and antitumor effect on human tumor cells remains unknown. Herein, we showed that ST-4 significantly activated TCR Vβ 12, 13A, 14, 15, 17, and 20 CD4⁺ and CD8⁺ T cells, which produced substantial amounts of granzyme B and perforin. These cytokines exhibited antitumor effect on K562 cells by promoting apoptosis and inducing S-phase cell cycle arrest. Conversely, the granzyme B inhibitor or perforin inhibitor significantly weakened antitumor effect of ST-4, accompanied by a decrease of cleaved proapoptotic BAX and cytochrome c, and an increase of antiapoptotic BCL2. Taken together, these data suggest that granzyme B and perforin produced by ST-4-activated CD4⁺ T cells and CD8⁺ T cells play a pivotal role in inducing K562 cell apoptosis by the mitochondrial apoptotic pathway, and support ST-4 as a potential candidate for cancer immunotherapy.

Studies on vascular response to full superantigens and superantigen derived peptides: Possible production of novel superantigen variants with less vasodilation effect for tolerable cancer immunotherapy

Superantigens (SAgs) are a class of antigens that cause non-specific activation of T-cells resulting in polyclonal T cell activation and massive cytokine release and causing symptoms similar to sepsis, e.g. hypotension and subsequent hyporeactivity. We investigated the direct effect of SAgs on vascular tone using two recombinant SAgs, SEA and SPEA. The roles of Nitric Oxide (NO) and potentially hyperpolarization, which is dependent on the K⁺ channel activation, were also explored. The data show that SEA and SPEA have direct vasodilatory effects that were in part NO-dependent, but completely dependent on activation of K⁺ channels. Our work also identified the functional regions of one of the superantigens, SPEA, that are involved in causing the vasodilation and possible hypotension. A series of 20 overlapping peptides, spanning the entire sequence of SPEA, were designed and synthesized. The vascular response of each peptide was measured, and the active peptides were identified. Our results implicate the regions, (61-100), (101-140) and (181-220) which cause the vasodilation and possible hypotension effects of SPEA. The data also shows that the peptide 181-220 exert the highest vasodilation effect. This work therefore, demonstrates the direct effect of SAgs on vascular tone and identify the active region causing this vasodilation. We propose that these three peptides could be effective novel antihypertensive drugs. We also overexpressed, in E.coli, four superantigens from codon optimized genes.

Construction, Expression, and Characterization of rSEA-EGF and In Vitro Evaluation of its Antitumor Activity Against Nasopharyngeal Cancer

Staphylococcal enterotoxin A is well known as a superantigen and able to be used for cancer immunotherapy. In this study, recombinant Staphylococcal enterotoxin A was genetically conjugated to epidermal growth factor to produce a chimeric protein recombinant Staphylococcal enterotoxin A–epidermal growth factor expressed in Escherichia coli. The recombinant Staphylococcal enterotoxin A–epidermal growth factor protein was purified using Strep-Tactin affinity chromatography and Endotoxin Removal Resin and identified by sodium dodecyl sulfate-polyacrylamide gel electropheresis and liquid chromatography-tandem mass spectrometry analysis. Furthermore, in vitro experiments showed purified recombinant Staphylococcal enterotoxin A–epidermal growth factor could successfully bind to the human nasopharyngeal carcinoma cell line CNE2, significantly promote the proliferation of human peripheral blood mononuclear cells, and enhance the secretion of several cytokines that have broad antitumor activities, such as interferon-γ, tumor necrosis factor-α, and interleukin-2 . Importantly, recombinant Staphylococcal enterotoxin A–epidermal growth factor significantly inhibited proliferation of CNE2 cells and promoted apoptosis in CNE2 cells when cocultured with peripheral blood mononuclear cells. Finally, both the binding of recombinant Staphylococcal enterotoxin A–epidermal growth factor and the toxicity of recombinant Staphylococcal enterotoxin A–epidermal growth factor-activated peripheral blood mononuclear cells were demonstrated as specific and only effective on high epidermal growth factor receptor-expressing cell lines. In all, our work suggests that recombinant Staphylococcal enterotoxin A–epidermal growth factor serves as a promising novel immunotherapeutic agent. More in vivo and in vitro studies are needed to verify its antitumor potency, as well as investigate the underlying mechanisms in cancer immunotherapy.

Superantigen staphylococcal enterotoxin C1 inhibits the growth of bladder cancer

Superantigens can induce cell-mediated cytotoxicity preferentially against MHC II-positive target cells with large amounts of inflammatory cytokines releasing. In this study, superantigen staphylococcal enterotoxin C (SEC) 1 was investigated to evaluate its potential in bladder cancer immunotherapy in vitro and in vivo. Our results revealed that SEC1 could stimulate the proliferation of human peripheral blood mononuclear cells (PBMCs) in a dose-dependent manner, accompanied with the release of interleukin-2, interferon-γ, and tumor necrosis factor-α, and increased the population of CD4+ T cells and CD8+ T cells. PBMCs stimulated by SEC1 could initiate significant cytotoxicity towards human bladder cancer cells in vitro. The results of in vivo antitumor experiment indicated that SEC1 could decrease the rate of tumor formation and prolong the survival time of tumor-bearing mice. Our study demonstrated that SEC1 inhibited the growth of bladder cancer. And it is also suggested that SEC1 may become a candidate for bladder cancer immunotherapy.

Naptumomab estafenatox: targeted immunotherapy with a novel immunotoxin

Improvement of cancer therapy by introducing new concepts is still urgent even though there have been major advancements lately. Immunotherapy is well on the way to becoming an established tool in the cancer treatment armory. It seems that a combination of (1) activation of immune effector cells and selective targeting of them to tumors and (2) the inhibition of immune suppression often induced by the tumor itself are necessary to achieve the therapeutic goal. The immunotoxin naptumomab estafenatox was developed in an effort to activate and target the patient’s own T cells to their tumor, by fusing a superantigen (SAg) variant that activates T lymphocytes to the Fab moiety of a tumor-reactive monoclonal antibody. Naptumomab estafenatox targets the 5T4 tumor antigen, a 72-kDa oncofetal trophoblast protein expressed on many carcinomas, including renal cell carcinoma. The therapeutic effect is associated with activation of SAg-binding T cells. The SAg-binding T lymphocytes expand, differentiate to effector cells, and infiltrate the tumor. The therapeutic efficacy is most likely related to the dual mechanism of tumor cell killing: (1) direct lysis by cytotoxic T lymphocytes of tumor cells expressing the antigen recognized by the antibody moiety of the fusion protein and (2) secretion of cytokines eliminating antigen-negative tumor cell variants. Naptumomab estafenatox has been clinically tested in a range of solid tumors with focus on renal cell carcinoma. This review looks at the clinical experience with the new immunotoxin and its potential.

Control of established colon cancer xenografts using a novel humanized single chain antibody-streptococcal superantigen fusion protein targeting the 5T4 oncofetal antigen

Superantigens (SAgs) are microbial toxins that cross-link T cell receptors with major histocompatibility class II (MHC-II) molecules leading to the activation of large numbers of T cells. Herein, we describe the development and preclinical testing of a novel tumor-targeted SAg (TTS) therapeutic built using the streptococcal pyrogenic exotoxin C (SpeC) SAg and targeting cancer cells expressing the 5T4 tumor-associated antigen (TAA). To inhibit potentially harmful widespread immune cell activation, a SpeC mutation within the high-affinity MHC-II binding interface was generated (SpeC_D203A) that demonstrated a pronounced reduction in mitogenic activity, yet this mutant could still induce immune cell-mediated cancer cell death in vitro. To target 5T4⁺ cancer cells, we engineered a humanized single chain variable fragment (scFv) antibody to recognize 5T4 (scFv5T4). Specific targeting of scFv5T4 was verified. SpeC_D203A fused to scFv5T4 maintained the ability to activate and induce immune cell-mediated cytotoxicity of colorectal cancer cells. Using a xenograft model of established human colon cancer, we demonstrated that the SpeC-based TTS was able to control the growth and spread of large tumors in vivo. This required both TAA targeting by scFv5T4 and functional SAg activity. These studies lay the foundation for the development of streptococcal SAgs as ‘next-generation’ TTSs for cancer immunotherapy.

Delivery of interferons and siRNA targeting STAT3 using lentiviral vectors suppresses the growth of murine melanoma

Interferons (IFNs) have been investigated as important cytokines in immunotherapy. The use of IFNs in cancer immunotherapy has had limited success. In this study, IFN genes were delivered into B16 melanoma cells by lentiviral vectors, and their effects on B16 melanoma were comprehensively analyzed. Type II IFN significantly impaired the viability of B16 cells in vitro. Expression of IFNα and IFNβ in B16 cells efficiently suppressed the establishment of inoculated melanoma. However, intratumoral delivery of IFNs alone with lentiviral vectors had no therapeutic effects on established melanoma. To address the lack of response, a lentivector was constructed to simultaneously transfer therapeutic genes and small interfering RNAs (siRNAs). IFNs and siRNA targeting signal transducer and activator of transcription 3 (STAT3), which is a major immune suppressive transcription factor in melanoma, were delivered simultaneously into the tumor milieu. This treatment successfully rescued the response to IFNγ and attenuated the growth of established tumors. This method has the potential to improve the therapeutic effects of IFNs in cancer immunotherapy.

Novel antibody-based proteins for cancer immunotherapy

The relative success of monoclonal antibodies in cancer immunotherapy and the vast manipulation potential of recombinant antibody technology have encouraged the development of novel antibody-based antitumor proteins. Many insightful reagents have been produced, mainly guided by studies on the mechanisms of action associated with complete and durable remissions, results from experimental animal models, and our current knowledge of the human immune system. Strikingly, only a small percent of these new reagents has demonstrated clinical value. Tumor burden, immune evasion, physiological resemblance, and cell plasticity are among the challenges that cancer therapy faces, and a number of antibody-based proteins are already available to deal with many of them. Some of these novel reagents have been shown to specifically increase apoptosis/cell death of tumor cells, recruit and activate immune effectors, and reveal synergistic effects not previously envisioned. In this review, we look into different approaches that have been followed during the past few years to produce these biologics and analyze their relative success, mainly in terms of their clinical performance. The use of antibody-based antitumor proteins, in combination with standard or novel therapies, is showing significant improvements in objective responses, suggesting that these reagents will become important components of the antineoplastic protocols of the future.

Human TGFalpha-derived peptide TGFalphaL3 fused with superantigen for immunotherapy of EGFR-expressing tumours

Background

Monoclonal antibodies have been employed as targeting molecules of superantigen for the preclinical treatment of a variety of tumours. However, other targeting molecules, such as tumour-related ligands or peptides, are less exploited. Here, we tested other targeting molecules by genetically fusing the third loop of transforming growth factor alpha (TGFalphaL3) to mutant staphylococcal enterotoxin A (SEA_D227A).

Results

The resultant fusion proteins were expressed in E. coli and purified to homogeneity through a Ni-NTA affinity column. Fusion protein TGFalphaL3SEA_D227A can promote splenocyte proliferation to a level comparable to recombinant SEA (rSEA) and bind to EGFR-expressing tumour cells in an EGFR-dependent way. Consistent with these observations, TGFalphaL3SEA_D227A exerted an inhibitory effect on the growth of EGFR-expressing tumour cells both in vitro and in vivo. Notably, significant infiltrations of CD8⁺ and CD4⁺ T cells were detected in the tumour tissues of these C57BL/6 mice treated with TGFalphaL3SEA_D227A, suggesting the involvement of T cells in this tumour-inhibitory process.

Conclusions

The data here showed that TGFαL3 is capable of targeting superantigen to tumours and exerting an inhibitory effect on tumour growth, which enables TGFαL3SEA_D227A to be an attractive candidate for the immunotherapy of EGFR-expressing tumours.

An oral TLR7 agonist is a potent adjuvant of DNA vaccination in transgenic mouse tumor models

In vivo electroporation of plasmid DNA (DNA-EP) is an efficient and safe method for vaccines resulting in increased DNA uptake, enhanced protein expression and increased immune responses to the target antigen in a variety of species. To further enhance the efficacy of DNA-EP, we have evaluated the toll-like receptor7 (TLR7) agonist-2, 9, substituted 8-hydroxyadenosine derivative or SM360320--as an adjuvant to vaccines against HER2/neu and CEA in BALB-neuT and CEA transgenic mice (CEA.Tg), respectively. SM360320 induced in vivo secretion of interferon alpha (IFNalpha) and exerted a significant antitumor effect in CEA.Tg mice challenged with a syngenic tumor cell line expressing CEA and an additive effect with a CEA vaccine. Additionally, combination of SM360320 with plasmid encoding the extracellular and transmembrane domain of ratHER2/neu affected the spontaneous tumor progression in BALB-neuT mice treated in an advanced disease setting. The antitumor effect in mice treated with DNA-EP and SM360320 was associated with an anti-CEA and anti-p185(neu) antibody isotype switch from IgG1 to IgG2a. These data demonstrate that SM360320 exerts significant antitumor effects and can act in association with DNA-EP for CEA-positive colon cancer and HER2-positive mammary carcinoma. These observations therefore emphasize the potential of SM360320 as immunological adjuvant for therapeutic DNA vaccines.