Seungyeop Lee

Pneumococcal pep27 mutant immunization stimulates cytokine secretion and confers long-term immunity with a wide range of protection, including against non-typeable strains

Streptococcus pneumoniae is comprised of more than 90 serotypes and is the major causative agent of pneumonia, which results in over 1million deaths worldwide every year. Currently available injectable vaccines can protect against only 13-23 serotypes, and result in decrease of colonization against vaccine serotypes. However, they are neither effective for inhibition of non-vaccine serotypes colonization nor inhibition against initial colonization in the nasopharynx against various serotypes. Thus, development of a vaccine conveying broader protection at the colonization stage is required. This study examined whether the Δpep27 mutant could provide protection at the nasopharynx against a broad range of serotypes. Δpep27 immunization stimulated secretion of IL-4, IL-10, TNF-α, INF-γ and IL-17, and significantly increased secretory-IgA levels in bronchoalveolar lavage fluid. Colonization and opsonophagocytosis assays demonstrated that Δpep27 immunization could protect against many heterologous infections, including non-typeable strains, at the nasopharynx, and prompted efficient killing of heterologous strains, suggesting that Δpep27 immunization provides a wide range of cross-protection. Furthermore, Δpep27 immunization significantly increased both the survival rate and the level of IgG 3months post-immunization, demonstrating long-lasting immunity. Thus, Δpep27 could serve as a highly feasible mucosal vaccine once it is further developed into a non-transformable strain.

Effects of ginseng on stress-related depression, anxiety, and the hypothalamic–pituitary–adrenal axis

Ginseng effectively regulates the immune response and the hormonal changes due to stress, thus maintaining homeostasis. In addition to suppressing the occurrence of psychological diseases such as anxiety and depression, ginseng also prevents stress-associated physiological diseases. Recent findings have revealed that ginseng is involved in adjusting the hypothalamic–pituitary–adrenal axis and controlling hormones, thus producing beneficial effects on the heart and brain, and in cases of bone diseases, as well as alleviating erectile dysfunction. Recent studies have highlighted the potential use of ginseng in the prevention and treatment of chronic inflammatory diseases such as diabetes, rheumatoid arthritis, and allergic asthma. However, the mechanism underlying the effects of ginseng on these stress-related diseases has not been completely established. In this review, we focus on the disease pathways caused by stress in order to determine how ginseng acts to improve health. Central to our discussion is how this effective and stable therapeutic agent alleviates the anxiety and depression caused by stress and ameliorates inflammatory diseases.

Effect of decreased BCAA synthesis through disruption of ilvC gene on the virulence of Streptococcus pneumoniae

Streptococcus pneumoniae (pneumococcus) is responsible for significant morbidity and mortality worldwide. It causes a variety of life-threatening infections such as pneumonia, bacteremia, and meningitis. In bacterial physiology, the metabolic pathway of branched-chain amino acids (BCAAs) plays an important role in virulence. Nonetheless, the function of IlvC, one of the enzymes involved in the biosynthesis of BCAAs, in S. pneumoniae remains unclear. Here, we demonstrated that downregulation of BCAA biosynthesis by ilvC ablation can diminish BCAA concentration and expression of pneumolysin (Ply) and LytA, and subsequently attenuate virulence. Infection with an ilvC mutant showed significantly reduced mortality and colonization in comparison with strain D39 (serotype 2, wild type), suggesting that ilvC can potentiate S. pneumoniae virulence due to adequate BCAA synthesis. Taken together, these results suggest that the function of ilvC in BCAA synthesis is essential for virulence factor and could play an important role in the pathogenesis of respiratory infections.

Pulmonary Colonization Resistance to Pathogens via Noncanonical Wnt and Interleukin-17A by Intranasal pep27 Mutant Immunization

Background Previous studies have focused on colonization resistance of the gut microbiota against antibiotic resistant strains. However, less research has been performed on respiratory colonization resistance. Methods Because respiratory colonization is the first step of respiratory infections, intervention to prevent colonization would represent a new approach for preventive and therapeutic measures. The Th17 response plays an important role in clearance of respiratory pathogens. Thus, harnessing the Th17 immune response in the mucosal site would be an effective method to design a respiratory mucosal vaccine. Results In this study, we show that intranasal Δpep27 immunization induces noncanonical Wnt and subsequent interleukin (IL)-17 secretion, and it inhibits Streptococcus pneumoniae, Staphylococcus aureus, and Klebsiella pneumoniae colonization. Moreover, IL-17A neutralization or nuclear factor of activated T-cell inhibition augmented bacterial colonization, indicating that noncanonical Wnt signaling is involved in pulmonary colonization resistance. Conclusions Therefore, Δpep27 immunization can provide nonspecific respiratory colonization resistance via noncanonical Wnt signaling and IL-17A-related pathways.

Induction of the pneumococcal vncRS operon by lactoferrin is essential for pneumonia

ABSTRACT Streptococcus pneumoniae (pneumococcus), the major pathogen for pneumonia, commonly colonizes the lung, but the mechanism underlying the coordination of virulence factors during invasion via the host protein remains poorly understood. Bacterial lysis releases the components of the cell wall, and triggers innate immunity and the subsequent secretion of pro-inflammatory cytokines. Previously, the virulence of the pep27 mutant was shown to be attenuated as a feasible candidate for vaccine development. However, the role of pep27 gene, belonging to the vancomycin-resistance locus (vncRS operon), in virulence, is largely unknown. This study demonstrates that transferrin in the host serum reduces the survival of the host during S. pneumoniae infections in mice. The exposure of the pneumococcal D39 strain to lactoferrin induced the vncRS operon, lysis, and subsequent in vivo cytokine production, resulting in lung inflammation. However, these responses were significantly attenuated in pneumococci harboring a mutation in pep27. Mechanistically, the VncS ligand, identified as lactoferrin, induced the vncRS operon and increased the in vivo mortality rates. Thus, serum-induced activation of vncRS plays an essential role in inducing pneumonia.

ATF3 Stimulates IL-17A by Regulating Intracellular Ca2+/ROS-Dependent IL-1β Activation During Streptococcus pneumoniae Infection

Activating transcription factor-3 (ATF3) in the ER stress pathway induces cytokine production and promotes survival during gram-positive bacterial infection. IL-17A is a critical cytokine that is essential for clearance of Streptococcus pneumoniae. However, the mechanism by which ATF3 induces IL-17A production remains unknown. Here, we show that ATF3 induces IL-17A production via NLRP3 inflammasome-dependent IL-1β secretion. Survival rates were comparable in IL-17A-depleted and ATF3 KO mice but were lower than in WT mice treated with isotype control, indicating that ATF3 positively regulated IL-17A production. Indeed, ATF3 KO mice showed a marked reduction in IL-17A protein and mRNA expression compared to levels in WT mice. Moreover, mitochondrial IL-1β production by bone marrow-derived macrophages was significantly reduced in ATF3 KO mice as a result of the disruption of cellular ROS and Ca2+ homeostasis. Accordingly, ATF3 KO mice displayed diminished survival and bacterial clearance following S. pneumoniae infection. Taken together, these data suggest a mechanism in which macrophage ATF3 promotes IL-17A production in γδ T cells to rapidly induce host defenses during early S. pneumoniae infection.

Estrogen receptor-β of microglia underlies sexual differentiation of neuronal protection via ginsenosides in mice brain

Streptococcus pneumoniae infection in acute bacterial meningitis can lead to widespread brain damage and mortality. Inflammatory responses by immune cells in the brain are thought to determine the degree of brain injury. Yet, the mechanisms underlying host responses to pneumococcal meningitis are largely unknown. To explore host responses as a potential therapeutic target for preventing brain injury after pneumococcal meningitis.

Inhibition of Autolysis by Lipase LipA in Streptococcus pneumoniae Sepsis

More than 50% of sepsis cases are associated with pneumonia. Sepsis is caused by infiltration of bacteria into the blood via inflammation, which is triggered by the release of cell wall components following lysis. However, the regulatory mechanism of lysis during infection is not well defined. Mice were infected with Streptococcus pneumoniae D39 wild-type (WT) and lipase mutant (ΔlipA) intranasally (pneumonia model) or intraperitoneally (sepsis model), and survival rate and pneumococcal colonization were determined. LipA and autolysin (LytA) levels were determined by qPCR and western blotting. S. pneumoniae Spd_1447 in the D39 (type 2) strain was identified as a lipase (LipA). In the sepsis model, but not in the pneumonia model, mice infected with the ΔlipA displayed higher mortality rates than did the D39 WT-infected mice. Treatment of pneumococci with serum induced LipA expression at both the mRNA and protein levels. In the presence of serum, the ΔlipA displayed faster lysis rates and higher LytA expression than the WT, both in vitro and in vivo. These results indicate that a pneumococcal lipase (LipA) represses autolysis via inhibition of LytA in a sepsis model.

Korean red ginseng enhances pneumococcal Δpep27 vaccine efficacy by inhibiting reactive oxygen species production

Background Streptococcus pneumoniae, more than 90 serotypes of which exist, is recognized as an etiologic agent of pneumonia, meningitis, and sepsis associated with significant morbidity and mortality worldwide. Immunization with a pneumococcal pep27 mutant (Δpep27) has been shown to confer comprehensive, long-term protection against even nontypeable strains. However, Δpep27 is effective as a vaccine only after at least three rounds of immunization. Therefore, treatments capable of enhancing the efficiency of Δpep27 immunization should be identified without delay. Panax ginseng Mayer has already been shown to have pharmacological and antioxidant effects. Here, the ability of Korean Red Ginseng (KRG) to enhance the efficacy of Δpep27 immunization was investigated. Methods Mice were treated with KRG and immunized with Δpep27 before infection with the pathogenic S. pneumoniae strain D39. Total reactive oxygen species production was measured using lung homogenates, and inducible nitric oxide (NO) synthase and antiapoptotic protein expression was determined by immunoblotting. The phagocytic activity of peritoneal macrophages was also tested after KRG treatment. Results Compared with the other treatments, KRG significantly increased survival rate after lethal challenge and resulted in faster bacterial clearance via increased phagocytosis. Moreover, KRG enhanced Δpep27 vaccine efficacy by inhibiting reactive oxygen species production, reducing extracellular signal–regulated kinase apoptosis signaling and inflammation. Conclusion Taken together, our results suggest that KRG reduces the time required for immunization with the Δpep27 vaccine by enhancing its efficacy.

Corrigendum: ATF3 provides protection from Staphylococcus aureus and Listeria monocytogenes infections

School of Pharmacy, Sungkyunkwan University, Su-Won 440–746, South Korea ∗Corresponding Author: School of Pharmacy, Sungkyunkwan University, 300 Chunchundong, Su-won 440–746, South Korea. Tel: +82-31-2907707; Fax: +82-31-2907727; E-mail: dkrhee@skku.ac.kr †Present Address: Department of Microbiology & Molecular Genetics, University of Texas Health Science Center, Houston, TX 77030, USA. One sentence summary: Gram-positive Staphylococcus aureus and Listeria monocytogenes infections induce ATF3 (eukaryotic transcriptional regulator), which subsequently functions as a positive regulator for cytokine production and provides protection from these lethal infections. Editor: Jan-Ingmar Flock