Mode of disulfide bond formation of a heat-stable enterotoxin (STh) produced by a human strain of enterotoxigenic Escherichia coli

AbstractTo determine the modes of three disulfide linkages in the heat-stable enterotoxin (STh) produced by a human strain of enterotoxigenic Escherichia coli, we synthesized STh(6–18), which consists of 13 amino acid residues and has the same intramolecular disulfide linkages as native STh [(1985) FEBS Lett. 181, 138–142], by stepwise and selective formation of disulfide bonds using different types of removable protecting groups for the Cys residues. Synthesis of the peptide with different modes of disulfide bond formation provided three peptides consistent with standard STh(6–18) in their physicochemical and biological properties, thereby indicating that the disulfide bonds in STh(6–18) are

Amino acid sequence of heat-stable enterotoxin produced by Vibrio cholerae non-01

AbstractThe amino acid sequence of heat-stable enterotoxin, produced by Vibrio cholerae non-01 and isolated from its culture supernatant, was determined by both Edman degradation of native and reductively carboxy-methylated enterotoxin and also a combination of fast atom bombardment mass spectrometry and carboxy-peptidase Y digestion of native enterotoxin to be as follows: Ile-Asp-Cys-Cys-Glu-Ile-Cys-Cys-Asn-Pro-Ala-Cys-Phe-Gly-Cys-Leu-Asn. This sequence is very similar, but not identical, to those of heat-stable enterotoxins produced by enterotoxigenic Escherichia coli and Yersinia enterocolitica

A Newly Identified Insertion Mutation in the Thyroid Hormone Receptor-β Gene in a Korean Family with Generalized Thyroid Hormone Resistance

Thyroid hormone resistance syndrome (RTH) is a rare disorder and is characterized by elevated levels of circulating free thyroid hormones, inappropriate secretion of thyroid stimulating hormone (TSH), and reduced peripheral tissue response to thyroid hormone. 90% of RTH subjects, when studied at the level of the gene, have been found to harbor mutations in the thyroid hormone receptor-β (THRB) gene. These affected individuals have been shown to possess a variety of missense mutations, resulting from changes in a single nucleotide in the THRB gene that corresponds to amino acid alternation. However, insertion or deletion mutations in the THRB gene sequence are quite rare, and have been observed in only a very few cases. In this study, we describe two such cases, in which two members of the same family were determined to harbor an insertion mutation in exon 10, and had also been diagnosed with generalized RTH. This insertion mutation, specifically the insertion of a cytosine at nucleotide 1358 of the THRB gene, is, to the best of our knowledge, the first such mutation reported among RTH patients in Korea

Reactive Oxygen Species Enhance TLR10 Expression in the Human Monocytic Cell Line THP-1

We investigated TLR10 expression in human monocytes, THP-1 cells, cultured in hypoxia (3% O2). Levels of both TLR10 mRNA and protein in THP-1 cells cultured in hypoxia were significantly higher than those cultured in normoxia (20% O2). We examined intracellular reactive oxygen species (ROS) content in hypoxic cells, and TLR10 expression in cells treated with hydrogen peroxide (H2O2), to determine whether the increase in TLR10 expression observed with hypoxia was due to an increase in intracellular ROS levels. We found that the level of intracellular ROS in cells subject to hypoxia was significantly higher than in normoxia. Experiments with ROS synthesis inhibitors revealed that hypoxia induced ROS production is mainly due to NADPH oxidase activity. TLR10 mRNA expression was increased by treatment with H2O2 at concentrations ranging from 50 to 250 μM. We screened the TLR10 promoter and found putative binding sites for transcription factors (TFs), such as NF-κB, NF-AT and AP-1. Next, we examined TF activities using a luciferase reporter assay. Activities of NF-κB, NF-AT and AP-1 in the cells treated with H2O2 were significantly higher than in untreated cells. The experiment with TF inhibitors revealed that ROS-induced upregulation of TLR10 expression is mainly due to NF-κB activation. Overall, our results suggest that hypoxia or ROS increase TLR10 expression in human monocytes and the transcriptional activities of NF-κB are involved in this process. Therefore, it is suggested that ROS produced by various exogenous stimuli may play a crucial role in the regulation of expression and function of TLR10 as second messengers

Stimulatory Effect of β-glucans on Immune Cells

β-Glucans are naturally occurring polysaccharides that are produced by bacteria, yeast, fungi, and many plants. Although their pharmacological activities, such as immunomodulatory, anti-infective and anti-cancer effects, have been well studied, it is still unclear how β-glucans exert their activities. However, recent studies on the β-glucan receptors shed some light on their mechanism of action. Since β-glucans have large molecular weights, they must bind surface receptors to activate immune cells. In this review, we summarize the immunopharmacological activities and the potential receptors of β-glucans in immune cells

Prevalence of tick-borne encephalitis virus in ticks from southern Korea

The prevalence of tick-borne encephalitis virus (TBEV) in southern Korea was determined by collecting ticks using tick drags. A total of 4,077 of 6,788 ticks collected were pooled (649 pools) according to collection site, species, and developmental stage and assayed for TBEV. The TBEV protein E and NS5 gene fragments were detected using RT-nested PCR in six pools of nymphs collected from Jeju Island (2,491 ticks). The minimum field detection rates for TBEV were 0.17% and 0.14% for Haemaphysalis longicornis and Haemayphysalis flava nymphs, respectively. The 252 bp NS5 and 477 bp protein E gene amplicons were sequenced. Phylogenetic analysis showed that the NS5 and protein E genes of the Jeju strain were clustered with Western subtype (98.0% and 99.4% identity, respectively). The Western subtype of TBEV is endemic in Korea, including Jeju Island. The study of vector and zoonotic host susceptibility to TBEV is required to better understand its potential impact on public health

Comparison of population-based measles-rubella immunoglobulin G antibody prevalence between 2014 and 2019 in Lao People's Democratic Republic: Impacts of the national immunization program.

OBJECTIVES: We evaluated the effectiveness of the Lao People's Democratic Republic's measles-rubella immunization program using the seroprevalence from two cross-sectional surveys. METHODS: The nationwide surveys occurred in 2014 and 2019 using a multistage cluster sampling, both requiring samples from 2184 individuals from 52 randomly selected villages. Immunoglobulin G titers, measured using enzyme-linked immunosorbent assay, were considered positive at ≥120 mIU/ml (measles) and ≥10 IU/ml (rubella). We calculated the vaccination-related reduction in the force of rubella infection and the number of congenital rubella syndrome cases averted in 2019. RESULTS: We collected 2135 (women: 55.2%, mean age: 23.2 years) and 2001 (52.7%, 23.1 years) samples in 2014 and 2019, respectively. During 2014-2019, immunoglobulin G prevalence increased from 83.9% (95% confidence interval [CI]: 83.8-84.0) to 98.3% (97.7-98.8) for measles and from 75.4% (75.3-75.5) to 87.8% (86.4-89.2) for rubella. The most plausible reduction in the average force of rubella infection was 100% (95% CI: 28-100) since vaccination started, averting 78 (95% CI: 42-128) congenital rubella syndrome cases in 2019. CONCLUSION: This is the first population-based study for measles and rubella at two different time points in developing countries. Measles and rubella seroprevalence increased significantly during 2014-2019, greatly exceeding the immunity thresholds for their elimination

Impact of HIV on Cell Survival and Antiviral Activity of Plasmacytoid Dendritic Cells

Plasmacytoid dendritic cells (pDCs) are important mediators of innate immunity that act mainly through secretion of interferon (IFN)-α. Previous studies have found that these cells can suppress HIV in vitro; additionally, pDCs have been shown to be severely reduced in the peripheral blood of HIV-infected individuals. In the present study, we sought to determine the ability of pDCs to directly suppress viral replication ex vivo and to delineate the potential mechanisms whereby pDCs are depleted in HIV-infected individuals. We demonstrate that activated pDCs strongly suppress HIV replication in autologous CD4(+) T cells via a mechanism involving IFN-α as well as other antiviral factors. Of note, unstimulated pDCs from infected individuals who maintain low levels of plasma viremia without antiretroviral therapy were able to suppress HIV ex vivo via a mechanism requiring cell-to-cell contact. Our data also demonstrate that death of pDCs by both apoptosis and necrosis is induced by fusion of HIV with pDCs. Taken together, our data suggest that pDCs play an important role in the control of HIV replication and that high levels of viral replication in vivo are associated with pDC cell death via apoptosis and necrosis. Elucidation of the mechanism by which pDCs suppress HIV replication in vivo may have clinically relevant implications for future therapeutic strategies