Circular RNA vaccines against SARS-CoV-2 and emerging variants.

As the emerging variants of SARS-CoV-2 continue to drive the worldwide pandemic, there is a constant demand for vaccines that offer more effective and broad-spectrum protection. Here, we report a circular RNA (circRNA) vaccine that elicited potent neutralizing antibodies and T cell responses by expressing the trimeric RBD of the spike protein, providing robust protection against SARS-CoV-2 in both mice and rhesus macaques. Notably, the circRNA vaccine enabled higher and more durable antigen production than the 1mΨ-modified mRNA vaccine and elicited a higher proportion of neutralizing antibodies and distinct Th1-skewed immune responses. Importantly, we found that the circRNARBD-Omicron vaccine induced effective neutralizing antibodies against the Omicron but not the Delta variant. In contrast, the circRNARBD-Delta vaccine protected against both Delta and Omicron or functioned as a booster after two doses of either native- or Delta-specific vaccination, making it a favorable choice against the current variants of concern (VOCs) of SARS-CoV-2.

Nanomedicine targets iron metabolism for cancer therapy.

Iron is an essential element for cell proliferation and homeostasis by engaging in cell metabolism including DNA synthesis, cell cycle, and redox cycling; however, iron overload could contribute to tumor initiation, proliferation, metastasis, and angiogenesis. Therefore, manipulating iron metabolisms, such as using iron chelators, transferrin receptor 1 (TFR1) Abs, and cytotoxic ligands conjugated to transferrin, has become a considerable strategy for cancer therapy. However, there remain major limitations for potential translation to the clinic based on the regulation of iron metabolism in cancer treatment. Nanotechnology has made great advances for cancer treatment by improving the therapeutic potential and lowering the side-effects of the proved drugs and those under various stages of development. Early studies that combined nanotechnology with therapeutic means for the regulation of iron metabolism have shown certain promise for developing specific treatment options based on the intervention of cancer iron acquisition, transportation, and utilization. In this review, we summarize the current understanding of iron metabolism involved in cancer and review the recent advances in iron-regulatory nanotherapeutics for improved cancer therapy. We also envision the future development of nanotherapeutics for improved treatment for certain types of cancers.

PEGylation and antioxidant effects of a human glutathione peroxidase 1 mutant.

Human glutathione peroxidase1 (hGPx1) is a good antioxidant and potential drug, but the limited availability and poor stability of hGPx1 have affected its development and application. To solve this problem, we prepared a hGPx1 mutant (GPx1M) with high activity in an Escherichia coli BL21(DE3)cys auxotrophic strain using a single protein production (SPP) system. In this study, the GPx1M was conjugated with methoxypolyethylene glycol-succinimidyl succinate (SS-mPEG, Mw = 5 kDa) chains to enhance its stability. SS-mPEG-GPx1M and GPx1M exhibited similar enzymatic activity and stability toward pH and temperature change, and in a few cases, SS-mPEG-GPx1M was discovered to widen the range of pH stability and increase the temperature stability. Lys 38 was confirmed as PEGylated site by liquid-mass spectrometry. H9c2 cardiomyoblast cells and Sprague-Dawley (SD) rats were used to evaluate the effects of GPx1M and SS-mPEG-GPx1M on preventing or alleviating adriamycin (ADR)-mediated cardiotoxicity, respectively. The results indicated that GPx1M and SS-mPEG-GPx1M had good antioxidant effects in vitro and in vivo, and the effect of SS-mPEG-GPx1M is more prominent than GPx1M in vivo. Thus, PEGylation might be a promising method for the application of GPx1M as an important antioxidant and potential drug.

Study on antioxidant effect of recombinant glutathione peroxidase 1.

Glutathione peroxidase 1 (GPx1) is an important antioxidant selenium enzyme and has a good prospect for drug development. However, the expression of GPx1 requires a complex expression mechanism, which makes the drug development of recombinant GPx1 (rGPx1) difficult. In the previous study, we expressed highly active rhGPx1 in amber-less Escherichia coli by using a novel chimeric tRNAUTuT6. However, the antioxidant effect of rhGPx1 at the cellular and animal levels has not been verified. In this study, we established isoproterenol (ISO)-induced oxidative stress injury models to study the antioxidant effect of rhGPx1 at the cellular and animal levels. Meanwhile, in order to more accurately reflect the antioxidant effect of rGPx1 in mice, we used the same method to express recombinant mouse GPx1 (rmGPx1) as a control for rhGPx1. The results of a study showed that rhGPx1 has a good antioxidant effect at the cellular and animal levels. However, due to species differences, rhGPx1 had immunogenicity in mice and antibodies of rhGPx1 could inhibit its antioxidant activity, so the antioxidant effect of rhGPx1 was not as good as rmGPx1 in mice. Nevertheless, this study provides a reliable theoretical basis for the development of rhGPx1 as an antioxidant drug.

Bacterial cytoplasmic membranes synergistically enhance the antitumor activity of autologous cancer vaccines.

Cancer vaccines based on resected tumors from patients have gained great interest as an individualized cancer treatment strategy. However, eliciting a robust therapeutic effect with personalized vaccines remains a challenge because of the weak immunogenicity of autologous tumor antigens. Utilizing exogenous prokaryotic constituents that act as adjuvants to enhance immunogenicity is a promising strategy to overcome this limitation. However, nonspecific stimulation of the immune system may elicit an undesirable immunopathological state. To specifically trigger sufficient antitumor reactivity without notable adverse effects, we developed an antigen and adjuvant codelivery nanoparticle vaccine based on Escherichia coli cytoplasmic membranes (EMs) and tumor cell membranes (TMs) from resected autologous tumor tissue. Introduction of the EM into the hybrid membrane nanoparticle vaccines (HM-NPs) induced dendritic cell maturation, thus activating splenic T cells. HM-NPs showed efficacy in immunogenic CT26 colon and 4T1 breast tumor mouse models and also efficiently induced tumor regression in B16-F10 melanoma and EMT6 breast tumor mouse models. Furthermore, HM-NPs provoked a strong tumor-specific immune response, which not only extended postoperative animal survival but also conferred long-term protection (up to 3 months) against tumor rechallenge in a CT26 colon tumor mouse model. Specific depletion of different immune cell populations revealed that CD8+ T and NK cells were crucial to the vaccine-elicited tumor regression. Individualized autologous tumor antigen vaccines based on effective activation of the innate immune system by bacterial cytoplasmic membranes hold great potential for personalized treatment of postoperative patients with cancer.

Expression and characterization of recombinant bifunctional enzymes with glutathione peroxidase and superoxide dismutase activities.

To balance the production and decomposition of reactive oxygen species, living organisms have generated antioxidant enzymes and non-enzymatic antioxidant defense systems. Glutathione peroxidase (GPx) and superoxide dismutase (SOD) are two important antioxidant enzymes. Apart from their catalytic functions, they protect each other, resulting in more efficient removal of reactive oxygen species, protection of cells against injury, and maintenance of the normal metabolism of reactive oxygen species. SOD catalyzes the dismutation of the superoxide anion (O2•-) to oxygen (O2) and hydrogen peroxide (H2O2). H2O2 is then detoxified to water by GPx. In this study, human GPx1Ser and the Alvinella pompejana SOD (ApSOD) gene were used to design and generate several recombinant proteins with both GPx and SOD activities by combining traditional fusion protein technology, a cysteine auxotrophic expression system, and a single protein production (SPP) system. Among the fusion proteins, Se-hGPx1Ser-L-ApSOD exhibited the highest SOD and GPx activities. Additional research was conducted to better understand the properties of Se-hGPx1Ser-L-ApSOD. The synergism of Se-hGPx1Ser-L-ApSOD was evaluated by using an in vitro model. This research may facilitate future studies on the cooperation and catalytic mechanisms of GPx and SOD. We believe that the bifunctional enzyme has potential applications as a potent antioxidant.