Antigen Delivery Systems: Past, Present, and Future

The COVID-19 pandemic has increased demand for safe and effective vaccines. Research to develop vaccines against diseases including Middle East respiratory syndrome, Ebolavirus, human immunodeficiency virus, and various cancers would also contribute to global well-being. For successful vaccine development, the advancement of technologies such as antigen (Ag) screening, Ag delivery systems and adjuvants, and manufacturing processes is essential. Ag delivery systems are required not only to deliver a sufficient amount of Ag for vaccination, but also to enhance immune response. In addition, Ag types and their delivery systems determine the manufacturing processes of the vaccine product. Here, we analyze the characteristics of various Ag delivery systems: plasmids, viral vectors, bacterial vectors, nanoparticles, self-assembled particles, natural and artificial cells, and extracellular vesicles. This review provides insight into the current vaccine landscape and highlights promising avenues of research for the development and improvement of Ag delivery systems.

Vitisin B inhibits influenza A virus replication by multi-targeting neuraminidase and virus-induced oxidative stress

The development of drug-resistant influenza and new pathogenic virus strains underscores the need for antiviral therapeutics. Currently, neuraminidase (NA) inhibitors are commonly used antiviral drugs approved by the US Food and Drug Administration (FDA) for the prevention and treatment of influenza. Here, we show that vitisin B (VB) inhibits NA activity and suppresses H1N1 viral replication in MDCK and A549 cells. Reactive oxygen species (ROS), which frequently occur during viral infection, increase virus replication by activating the NF-κB signaling pathway, downmodulating glucose-6-phosphate dehydrogenase (G6PD) expression, and decreasing the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) antioxidant response activity. VB decreased virus-induced ROS generation by increasing G6PD expression and Nrf2 activity, and inhibiting NF-κB translocation to the nucleus through IKK dephosphorylation. In addition, VB reduced body weight loss, increased survival, decreased viral replication and the inflammatory response in the lungs of influenza A virus (IAV)-infected mice. Taken together, our results indicate that VB is a promising therapeutic candidate against IAV infection, complements existing drug limitations targeting viral NA. It modulated the intracellular ROS by G6PD, Nrf2 antioxidant response pathway, and NF-κB signaling pathway. These results demonstrate the feasibility of a multi-targeting drug strategy, providing new approaches for drug discovery against IAV infection.

A Novel Anti-PD-L1 Antibody Exhibits Antitumor Effects on Multiple Myeloma in Murine Models via Antibody-Dependent Cellular Cytotoxicity

Multiple myeloma is a malignant cancer of plasma cells. Despite recent progress with immunomodulatory drugs and proteasome inhibitors, it remains an incurable disease that requires other strategies to overcome its recurrence and non-response. Based on the high expression levels of programmed death-ligand 1 (PD-L1) in human multiple myeloma isolated from bone marrow and the murine myeloma cell lines, NS-1 and MOPC-315, we propose PD-L1 molecule as a target of anti-multiple myeloma therapy. We developed a novel anti-PD-L1 antibody containing a murine immunoglobulin G subclass 2a (IgG2a) fragment crystallizable (Fc) domain that can induce antibody-dependent cellular cytotoxicity. The newly developed anti-PD-L1 antibody showed significant antitumor effects against multiple myeloma in mice subcutaneously, intraperitoneally, or intravenously inoculated with NS-1 and MOPC-315 cells. The anti-PD-L1 effects on multiple myeloma may be related to a decrease in the immunosuppressive myeloidderived suppressor cells (MDSCs), but there were no changes in the splenic MDSCs after combined treatment with lenalidomide and the anti-PD-L1 antibody. Interestingly, the newly developed anti-PD-L1 antibody can induce antibody-dependent cellular cytotoxicity in the myeloma cells, which differs from the existing anti-PD-L1 antibodies. Collectively, we have developed a new anti-PDL1 antibody that binds to mouse and human PD-L1 and demonstrated the antitumor effects of the antibody in several syngeneic murine myeloma models. Thus, PD-L1 is a promising target to treat multiple myeloma, and the novel anti-PD-L1 antibody may be an effective anti-myeloma drug via antibody-dependent cellular cytotoxicity effects.

Morin Hydrate Inhibits Influenza Virus entry into Host Cells and Has Anti-inflammatory Effect in Influenzainfected Mice

Influenza virus is the major cause of seasonal and pandemic flu. Currently, oseltamivir, a potent and selective inhibitor of neuraminidase of influenza A and B viruses, is the drug of choice for treating patients with influenza virus infection. However, recent emergence of oseltamivir-resistant influenza viruses has limited its efficacy. Morin hydrate (3,5,7,2′,4′-pentahydroxyflavone) is a flavonoid isolated from Morus alba L. It has antioxidant, anti-inflammatory, neuroprotective, and anticancer effects partly by the inhibition of the NF-кB signaling pathway. However, its effects on influenza virus have not been studied. We evaluated the antiviral activity of morin hydrate against influenza A/Puerto Rico/8/1934 (A/ PR/8; H1N1) and oseltamivir-resistant A/PR/8 influenza viruses in vitro. To determine its mode of action, we carried out time course experiments, and time of addition, hemolysis inhibition, and hemagglutination assays. The effects of the co-administration of morin hydrate and oseltamivir were assessed using the murine model of A/PR/8 infection. We found that morin hydrate reduced hemagglutination by A/PR/8 in vitro. It alleviated the symptoms of A/PR/8-infection, and reduced the levels of pro-inflammatory cytokines and chemokines, such as TNF-α and CCL2, in infected mice. Co-administration of morin hydrate and oseltamivir phosphate reduced the virus titers and attenuated pulmonary inflammation. Our results suggest that morin hydrate exhibits antiviral activity by inhibiting the entry of the virus.

Murine γδ T Cells Render B Cells Refractory to Commitment of IgA Isotype Switching

γδ T cells are abundant in the gut mucosa and play an important role in adaptive immunity as well as innate immunity. Although γδ T cells are supposed to be associated with the enhancement of Ab production, the status of γδ T cells, particularly in the synthesis of IgA isotype, remains unclear. We compared Ig expression in T cell receptor delta chain deficient (TCRδ⁻/⁻) mice with wild-type mice. The amount of IgA in fecal pellets was substantially elevated in TCRδ⁻/⁻ mice. This was paralleled by an increase in surface IgA expression and total IgA production by Peyer's patches (PPs) and mesenteric lymph node (MLN) cells. Likewise, the TCRδ⁻/⁻ mice produced much higher levels of serum IgA isotype. Here, surface IgA expression and number of IgA secreting cells were also elevated in the culture of spleen and bone marrow (BM) B cells. Germ-line α transcript, an indicator of IgA class switch recombination, higher in PP and MLN B cells from TCRδ⁻/⁻ mice, while it was not seen in inactivated B cells. Nevertheless, the frequency of IgA+ B cells was much higher in the spleen from TCRδ⁻/⁻ mice. These results suggest that γδ T cells control the early phase of B cells, in order to prevent unnecessary IgA isotype switching. Furthermore, this regulatory role of γδ T cells had lasting effects on the long-lived IgA-producing plasma cells in the BM.

Antiviral and Anti-Inflammatory Activities of Pochonin D, a Heat Shock Protein 90 Inhibitor, against Rhinovirus Infection

Human rhinoviruses (HRV) are one of the major causes of common cold in humans and are also associated with acute asthma and bronchial illness. Heat-shock protein 90 (Hsp90), a molecular chaperone, is an important host factor for the replication of single-strand RNA viruses. In the current study, we examined the effect of the Hsp90 inhibitor pochonin D, in vitro and in vivo, using a murine model of human rhinovirus type 1B (HRV1B) infection. Our data suggested that Hsp90 inhibition significantly reduced the inflammatory cytokine production and lung damage caused by HRV1B infection. The viral titer was significantly lowered in HRV1B-infected lungs and in Hela cells upon treatment with pochonin D. Infiltration of innate immune cells including granulocytes and monocytes was also reduced in the bronchoalveolar lavage (BAL) by pochonin D treatment after HRV1B infection. Histological analysis of the lung and respiratory tract showed that pochonin D protected the mice from HRV1B infection. Collectively, our results suggest that the Hsp90 inhibitor, pochonin D, could be an attractive antiviral therapeutic for treating HRV infection.

Development of New Preventive and Therapeutic Vaccines for Tuberculosis

Tuberculosis (TB) is a contagious disease that has been responsible for the death of one billion people in the last 200 years. Until now, the only vaccine approved for the prevention of TB is Bacillus Calmette-Guérin (BCG), which is prepared by attenuating Mycobacterium bovis. However, one of the limitations of BCG is that its preventive effect against pulmonary TB varies from person to person. Therefore, there arises a need for a new TB vaccine to replace or supplement BCG. In this review, we have summarized the findings of current clinical trials on preventive and therapeutic TB vaccine candidates. In addition, we have discussed a novel vaccination approach using the cell-based vaccine presenting early secretory antigenic target-6 (ESAT-6), which is a potent immunogenic antigen. The role of ESAT-6 in hosts has also been described.

Anti-Human Rhinovirus 1B Activity of Dexamethasone viaGCR-Dependent Autophagy Activation

OBJECTIVES: Human rhinoviruses (HRVs) are the major cause of the common cold. Currently there is no registered, clinically effective, antiviral chemotherapeutic agent to treat diseases caused by HRVs. In this study, the antiviral activity of dexamethasone (DEX) against HRV1B was examined. METHODS: The anti–HRV1B activity of DEX was assessed by sulforhodamine B assay in HeLa cells, and by RT-PCR in the lungs of HRV1B-infected mice. Histological evaluation of HRV1B-infected lungs was performed and a histological score was given. Anti-HRV1B activity of DEX via the glucocorticoid receptor (GCR)-dependent autophagy activation was assessed by blocking with chloroquine diphosphate salt or bafilomycin A1 treatment. RESULTS: In HRV1B-infected HeLa cells, treatment with DEX in a dose-dependent manner, resulted in a cell viability of > 70% indicating that HRV1B viral replication was reduced by DEX treatment. HRV1B infected mice treated with DEX, had evidence of reduced inflammation and a moderate histological score. DEX treatment showed antiviral activity against HRV1B via GCR-dependent autophagy activation. CONCLUSION: This study demonstrated that DEX treatment showed anti-HRV1B activity via GCR-dependent autophagy activation in HeLa cells and HRV1B infected mice. Further investigation assessing the development of topical formulations may enable the development of improved DEX effectiveness.

Antiviral Activity of Itraconazole against Echovirus 30 Infection In Vitro

OBJECTIVES: Echovirus 30 is a major cause of meningitis in children and adults. The aim of this study was to investigate whether the antifungal drug itraconazole could exhibit antiviral activity against echovirus 30. METHODS: The cytopathic effect and viral RNA levels were assessed in RD cells as indicators of viral replication. The effects of itraconazole were compared to those of two known antiviral drugs, rupintrivir and pleconaril. The time course and time-of-addition assays were used to approximate the time at which itraconazole exerts its activity in the viral cycle. RESULTS: Itraconazole and rupintrivir demonstrated the greatest potency against echovirus 30, demonstrating concentration-dependent activity, whereas pleconaril showed no antiviral activity. Itraconazole did not directly inactivate echovirus 30 particles or impede viral uptake into RD cells, but did affect the initial stages of echovirus 30 infection through interference with viral replication. CONCLUSION: Itraconazole can be considered a lead candidate for the development of antiviral drugs against echovirus 30 that may be used during the early stages of echovirus 30 replication.

Inhibitory Effects of Norwogonin, Oroxylin A, and Mosloflavone on Enterovirus 71

Severe complications associated with EV71 infections are a common cause of neonatal death. Lack of effective therapeutic agents for these infections underlines the importance of research for the development of new antiviral compounds. In the present study, the anti-EV71 activity of norwogonin, oroxylin A, and mosloflavone from Scutellaria baicalensis Georgi was evaluated using a cytopathic effect (CPE) reduction method, which demonstrated that all three compounds possessed strong anti-EV71 activity and decreased the formation of visible CPEs. Norwogonin, oroxylin A, and mosloflavone also inhibited virus replication during the initial stage of virus infection, and they inhibited viral VP2 protein expression, thereby inhibiting viral capsid protein synthesis. However, ribavirin has a relatively weaker efficacy compared to the other drugs. Therefore, these findings provide important information that will aid in the utilization of norwogonin, oroxylin A, and mosloflavone for EV71 treatment.

Regulation of Intestinal Immune System by Dendritic Cells

Innate immune cells survey antigenic materials beneath our body surfaces and provide a front-line response to internal and external danger signals. Dendritic cells (DCs), a subset of innate immune cells, are critical sentinels that perform multiple roles in immune responses, from acting as principal modulators to priming an adaptive immune response through antigen-specific signaling. In the gut, DCs meet exogenous, non-harmful food antigens as well as vast commensal microbes under steady-state conditions. In other instances, they must combat pathogenic microbes to prevent infections. In this review, we focus on the function of intestinal DCs in maintaining intestinal immune homeostasis. Specifically, we describe how intestinal DCs affect IgA production from B cells and influence the generation of unique subsets of T cell.

Antiviral Activity of Chrysin Derivatives against Coxsackievirus B3 in vitro and in vivo

Chrysin is a 5,7-dihydroxyflavone and was recently shown to potently inhibit enterovirus 71 (EV71) by suppressing viral 3C protease (3Cpro) activity. In the current study, we investigated whether chrysin also shows antiviral activity against coxsackievirus B3 (CVB3), which belongs to the same genus (Enterovirus) as EV71, and assessed its ability to prevent the resulting acute pancreatitis and myocarditis. We found that chrysin showed antiviral activity against CVB3 at 10 muM, but exhibited mild cellular cytotoxicity at 50 muM, prompting us to synthesize derivatives of chrysin to increase the antiviral activity and reduce its cytotoxicity. Among four 4-substituted benzyl derivatives derived from C(5) benzyl-protected derivatives 7, 9-11 had significant antiviral activity and showed the most potent activity against CVB3 with low cytotoxicity in Vero cells. Intraperitoneal injection of CVB3 in BALB/c mice with 1x106 TCID50 (50% tissue culture infective dose) of CVB3 induced acute pancreatitis with ablation of acinar cells and increased serum CXCL1 levels, whereas the daily administration of 9 for 5 days significantly alleviated the pancreatic inflammation and reduced the elevation in serum CXCL1 levels. Collectively, we assessed the anti-CVB3 activities of chrysin and its derivatives, and found that among 4-substituted benzyl derivatives, 9 exhibited the highest activity against CVB3 in vivo, and protected mice from CVB3-induced pancreatic damage, simultaneously lowering serum CXCL1 levels.

Anti-Influenza Activity of Betulinic Acid from Zizyphus jujuba on Influenza A/PR/8 Virus

Betulinic acid, a pentacyclic triterpene isolated from Jujube tree (Zizyphus jujuba Mill), has been known for a wide range of biological and medicinal properties such as antibacterial, antimalarial, anti-inflammatory, antihelmintic, antinociceptive, and anticancer activities. In the study, we investigated the antiviral activity on influenza A/PR/8 virus infected A549 human lung adenocarcinoma epithelial cell line and C57BL/6 mice. Betulinic acid showed the anti-influenza viral activity at a concentration of 50 muM without a significant cytotoxicity in influenza A/PR/8 virus infected A549 cells. Also, betulinic acid significantly attenuated pulmonary pathology including increased necrosis, numbers of inflammatory cells and pulmonary edema induced by influenza A/PR/8 virus infection compared with vehicle- or oseltamivir-treated mice in vivo model. The down-regulation of IFN-gamma level, which is critical for innate and adaptive immunity in viral infection, after treating of betulinic acid in mouse lung. Based on the obtained results, it is suggested that betulinic acid can be the potential therapeutic agent for virus infection via anti-inflammatory activity.

Myeloid-Derived Suppressor Cells in Inflammatory Bowel Disease

Immature myeloid cells, also known as myeloid-derived suppressor cells (MDSCs), include neutrophilic and monocytic myeloid cells, and are found in inflammatory loci and secondary lymphoid organs in mice with intestinal inflammation, inflammatory bowel disease (IBD) patients, and tumor tissues. However, the roles of MDSCs in IBD are not yet well understood, and there are controversies regarding their immunosuppressive functions in IBD. In addition, recent studies have suggested that endoplasmic reticulum (ER) stress in intestinal epithelial cells, especially in Paneth cells, is closely associated with the induction of IBD. However, the ER stress in MDSCs accumulated in the inflamed tissues of IBD patients is not yet fully understood. In the current review, we discuss the presence of accumulated MDSCs in the intestines of IBD patients, and further speculate on their physiological roles in the inflammatory condition with interleukin 17-producing cells, including Th17 cells. In particular, we will discuss the divergent functions of MDSCs in ER stressed intestinal environments, including their pro-inflammatory or immunosuppressive roles, based on the consideration of unfolded protein responses initiated in intestinal epithelial cells by ER stress.

Myeloid-Derived Suppressor Cells in Inflammatory Bowel Disease

Immature myeloid cells, also known as myeloid-derived suppressor cells (MDSCs), include neutrophilic and monocytic myeloid cells, and are found in inflammatory loci and secondary lymphoid organs in mice with intestinal inflammation, inflammatory bowel disease (IBD) patients, and tumor tissues. However, the roles of MDSCs in IBD are not yet well understood, and there are controversies regarding their immunosuppressive functions in IBD. In addition, recent studies have suggested that endoplasmic reticulum (ER) stress in intestinal epithelial cells, especially in Paneth cells, is closely associated with the induction of IBD. However, the ER stress in MDSCs accumulated in the inflamed tissues of IBD patients is not yet fully understood. In the current review, we discuss the presence of accumulated MDSCs in the intestines of IBD patients, and further speculate on their physiological roles in the inflammatory condition with interleukin 17-producing cells, including Th17 cells. In particular, we will discuss the divergent functions of MDSCs in ER stressed intestinal environments, including their pro-inflammatory or immunosuppressive roles, based on the consideration of unfolded protein responses initiated in intestinal epithelial cells by ER stress.

Neuroprotective Effect of Steamed and Fermented Codonopsis lanceolata

Codonopsis lanceolata has been used as an herbal medicine for several lung infl ammatory diseases, such as asthma, tonsillitis, and pharyngitis. Previously, we showed the neuroprotective effect of steamed and fermented C. lanceolata (SFC) in vitro and in vivo. In the current study, the treatment of HT22 cells with SFC decreased glutamate-induced cell death, suggesting that SFC protected HT22 cells from glutamate-induced cytotoxicity. Based on these, we sought to elucidate the mechanisms of the neuroprotective effect of SFC by measuring the oxidative stress parameters and the expression of Bax and caspase-3 in HT22 cells. SFC reduced contents of ROS, Ca2+ and NO. Moreover, SFC restored contents of glutathione and glutathione reductase as well as inhibited Bax and caspase-3 activity in HT22 cells. These results indicate that steamed and fermented C. lanceolata (SFC) extract protected HT22 cells by anti-oxidative effect and inhibition of the expression of Bax and caspase-3.

Mucosal dendritic cells shape mucosal immunity

Dendritic cells (DCs) are key modulators that shape the immune system. In mucosal tissues, DCs act as surveillance systems to sense infection and also function as professional antigen-presenting cells that stimulate the differentiation of naive T and B cells. On the basis of their molecular expression, DCs can be divided into several subsets with unique functions. In this review, we focus on intestinal DC subsets and their function in bridging the innate signaling and adaptive immune systems to maintain the homeostasis of the intestinal immune environment. We also review the current strategies for manipulating mucosal DCs for the development of efficient mucosal vaccines to protect against infectious diseases.

Antiviral Activity of Hederasaponin B from Hedera helix against Enterovirus 71 Subgenotypes C3 and C4a

Enterovirus 71 (EV71) is the predominant cause of hand, foot and mouth disease (HFMD). The antiviral activity of hederasaponin B from Hedera helix against EV71 subgenotypes C3 and C4a was evaluated in vero cells. In the current study, the antiviral activity of hederasaponin B against EV71 C3 and C4a was determined by cytopathic effect (CPE) reduction method and western blot assay. Our results demonstrated that hederasaponin B and 30% ethanol extract of Hedera helix containing hederasaponin B showed significant antiviral activity against EV71 subgenotypes C3 and C4a by reducing the formation of a visible CPE. Hederasaponin B also inhibited the viral VP2 protein expression, suggesting the inhibition of viral capsid protein synthesis.These results suggest that hederasaponin B and Hedera helix extract containing hederasaponin B can be novel drug candidates with broad-spectrum antiviral activity against various subgenotypes of EV71.

Antiviral Activity of Hederasaponin B from Hedera helix against Enterovirus 71 Subgenotypes C3 and C4a

Enterovirus 71 (EV71) is the predominant cause of hand, foot and mouth disease (HFMD). The antiviral activity of hederasaponin B from Hedera helix against EV71 subgenotypes C3 and C4a was evaluated in vero cells. In the current study, the antiviral activity of hederasaponin B against EV71 C3 and C4a was determined by cytopathic effect (CPE) reduction method and western blot assay. Our results demonstrated that hederasaponin B and 30% ethanol extract of Hedera helix containing hederasaponin B showed significant antiviral activity against EV71 subgenotypes C3 and C4a by reducing the formation of a visible CPE. Hederasaponin B also inhibited the viral VP2 protein expression, suggesting the inhibition of viral capsid protein synthesis.These results suggest that hederasaponin B and Hedera helix extract containing hederasaponin B can be novel drug candidates with broad-spectrum antiviral activity against various subgenotypes of EV71.

Shigella flexneri Inhibits Intestinal Inflammation by Modulation of Host Sphingosine-1-Phosphate in Mice

Infection with invasive Shigella species results in intestinal inflammation in humans but no symptoms in adult mice. To investigate why adult mice are resistant to invasive shigellae, 6~8-week-old mice were infected orally with S. flexneri 5a. Shigellae successfully colonized the small and large intestines. Mild cell death was seen but no inflammation. The infected bacteria were cleared 24 hours later. Microarray analysis of infected intestinal tissue showed that several genes that are involved with the sphingosine-1-phosphate (S1P) signaling pathway, a lipid mediator which mediates immune responses, were altered significantly. Shigella infection of a human intestinal cell line modulated host S1P-related genes to reduce S1P levels. In addition, co-administration of S1P with shigellae could induce inflammatory responses in the gut. Here we propose that Shigella species have evasion mechanisms that dampen host inflammatory responses by lowering host S1P levels in the gut of adult mice.