Seok-Yong Lee

Emerging infectious diseases (EIDs) are one of the greatest threats to human health today, thus requiring an urgent response. Vaccines are one of the most effective means of preventing the spread of infectious diseases, and their usefulness in responding to EIDs has been clearly proven through the process of overcoming the global COVID-19 pandemic. As the characteristics of various vaccine formulations differ, it is necessary to apply the most appropriate one according to the EID response strategy. In this review, we first consider which vaccine formulation is the most suitable for EID vaccines by comparing the pros and cons of different vaccine formulations, and then we discuss the utility of mRNA vaccine formulations, which are considered the most promising for EID vaccines.

Radiotherapy is widely used as an effective non-surgical strategy to control malignant tumors. However, recurrence is one of common causes of treatment failure even after the effective radiotherapy. In this study, we focused on the effects of radiation-induced exosomal miR-21 on the tumor microenvironment to investigate the causes of recurrence. Analysis of the TCGA database revealed that breast cancer patients with high levels of miR-21 have significantly reduced overall survival when treated with radiotherapy compared to those who did not receive radiotherapy, indicating a high hazard ratio for miR-21 in patients undergoing this treatment. Additionally, exosomal miR-21 is found to be highly expressed in the serum of breast adenocarcinoma patients. To explore how miR-21 induces poor prognosis in irradiated breast cancer, we irradiated 4T1 cell line with low or high doses of radiation, and examined the impact of secreted exosomal miR-21 on breast cancer cell and tumor microenvironment. After 10 Gy irradiation, 4T1 cells secreted 2.20 ± 0.10 times more exosomes and exhibited a 1.85 ± 0.01-fold increase in exosomal miR-21 levels. Treatment with exosomes from 10 Gy-irradiated cancer cells led to enhanced tumor cell proliferation, wound healing, and migration. The survival rate of 10 Gy-irradiated tumor cells incubated with 10 Gy-derived exosomes increased by 2.83-fold. Moreover, the growth of subcutaneous tumors treated with 10 Gy exosomes (n = 13) was significantly faster compared to tumors treated with 0 Gy exosomes (n = 10, P < 0.05). In summary, our study revealed high-dose irradiation-induced exosomes were found to enhance tumor proliferation and invasiveness via the transfer of exosomal miR-21. Based on these findings, we suggest that radiation-induced exosomal miR-21 may contribute to a poorer prognosis of breast cancer patients undergoing radiotherapy.

Activated hepatic stellate cells (HSCs) play a detrimental role in liver fibrosis progression. Natural killer (NK) cells are known to selectively recognize abnormal or transformed cells via their receptor activation and induce target cell apoptosis and, therefore, can be used as a potential therapeutic strategy for liver cirrhosis. In this study, we examined the therapeutic effects of NK cells in the carbon tetrachloride (CCl₄)-induced liver cirrhosis mouse model. NK cells were isolated from the mouse spleen and expanded in the cytokine-stimulated culture medium. Natural killer group 2, member D (NKG2D)-positive NK cells were significantly increased after a week of expansion in culture. The intravenous injection of NK cells significantly alleviated liver cirrhosis by reducing collagen deposition, HSC marker activation, and macrophage infiltration. For in vivo imaging, NK cells were isolated from codon-optimized luciferase-expressing transgenic mice. Luciferase-expressing NK cells were expanded, activated and administrated to the mouse model to track them. Bioluminescence images showed increased accumulation of the intravenously inoculated NK cells in the cirrhotic liver of the recipient mouse. In addition, we conducted QuantSeq 3′ mRNA sequencing-based transcriptomic analysis. From the transcriptomic analysis, 33 downregulated genes in the extracellular matrix (ECM) and 41 downregulated genes involved in the inflammatory response were observed in the NK cell-treated cirrhotic liver tissues from the 1532 differentially expressed genes (DEGs). This result indicated that the repetitive administration of NK cells alleviated the pathology of liver fibrosis in the CCl₄-induced liver cirrhosis mouse model via anti-fibrotic and anti-inflammatory mechanisms. Taken together, our research demonstrated that NK cells could have therapeutic effects in a CCl₄-induced liver cirrhosis mouse model. In particular, it was elucidated that extracellular matrix genes and inflammatory response genes, which were mainly affected after NK cell treatment, could be potential targets.