Molecular structure and function of the carboxy-terminus of the alpha-toxin from Clostridium perfringens type A.

In order to interpret the molecular structure and biological characteristics of Clostridium perfringens alpha-toxin (CPA), the CPA251-370 gene was cloned and the 120 amino acid carboxy terminal of CPA (CPA251-370) was obtained. The secondary and three-dimensional (3D) structures of CPA251-370 were predicted. The secondary structure of CPA251-370 consisted primarily of 35.48% ß-sheets and 44.35% random coils. Compared with the CPA toxin consisting of 10 α-helices and eight ß-sheets, the 3D structure of CPA251-370 only contained eight ß-sheets. The circular dichroism (CD) spectrum detection showed that the CD spectrum of CPA251-370 changed slightly compared with the CD spectrum of CPA. Biological activity assays showed that CPA251-370 had lost the phospholipase C (PLC) activity and haemolytic activity of CPA. More importantly, the mice immunized with CPA251-370 were protected against a challenge with 1 MLD C. perfringens type A strain C57-1. This study laid a solid foundation for explaining the relationship between molecular structure and biological characteristics of CPA in the future. Our research also provides CPA251-370 as a candidate strains for genetic engineering subunit vaccines of C. perfringens type A.

Study of the Structure and Biological Activity of the Amino-Terminus of the α-Toxin from Clostridium welchii Type A.

To explore the biological activity of Clostridium welchii α-toxin (CPA), the Asp56 residue of CPA was mutated to glycine (CPA D56G) by site-directed mutagenesis, and the 250 amino acid amino-terminal phospholipase C (PLC)-containing domain of CPA (PLC1-250) was isolated. The secondary and three-dimensional (3D) structures of CPA D56G and PLC1-250 were predicted, and the results showed that the secondary structures of CPA D56G and PLC1-250 were composed of α-helices and random coils. The 3D structures of CPA D56G and PLC1-250 were similar to the 3D structures of CPA. The circular dichroism (CD) spectrum of CPA D56G differed from the CD spectrum of CPA, but the CD spectrum of PLC1-250 was similar to the CD spectrum of CPA. Biological activity assays showed that CPA D56G lost the PLC activity of CPA and that mice immunized with CPA D56G were protected against a challenge with 1 MLD C. welchii type A strain C57-1. In addition, PLC1-250 contained the PLC activity of CPA. This study laid a solid foundation for future studies on the relationship between the molecular structure and biological function of CPA and its molecular mechanism. Our study also provided CPA D56G as a candidate strain for engineering a CPA subunit vaccine for C. welchii type A.

Plasma SCF/c-kit Levels in Patients with Dipper and Non-Dipper Hypertension.

Objective The aim of this study was to investigate the relationship between peripheral plasma stem cell factor (SCF)/c-kit levels and the types of dipper and non-dipper hypertension in hypertensive patients. Methods This cross-sectional study included newly diagnosed hypertensive patients who underwent 24-hour ambulatory blood pressure monitor (ABPM) between January 2009 and 2012 in Jiangning city. Patients were divided into the dipper group and the non-dipper group according to ABPM measurements. The levels of SCF and its receptor c-kit, tumor necrosis factor-α (TNF-α) and interleukin 6 (IL-6) in peripheral blood were measured via enzyme-linked immunosorbent assays. The serum levels of glucose and lipid were examined as well. The levels of SCF/c-kit were compared between the dippers and the non-dippers; and their correlation with 24-hour mean systolic blood pressure (MSBP), 24-hour mean diastolic blood pressure (MDBP), TNF-α and IL-6 were investigated using linear regression analyses statistically. Results A total of 247 patients with newly diagnosed hypertension were recruited into the study, including 116 non-dippers and 131 dippers. The levels of peripheral plasma SCF were higher in non-dipper group (907.1±52.7 ng/L vs. 778.7±44.6 ng/L; t=2.837, P<0.01), and the levels of c-kit were higher in non-dipper group too (13.2±1.7 µg/L vs 9.57±1.4 µg/L; t=2.831, P<0.01). Linear regression analysis revealed that SCF/c-kit levels were significantly positively correlated with MSBP, MDBP, plasma TNF-α, and IL-6 levels (all P<0.01). Conclusions Peripheral plasma SCF/c-kit levels are higher in patients with non-dipper hypertension than those with dipper one, and significantly correlate with 24-hour MSBP, 24-hour MDBP, serum TNF-α and IL-6 levels.

Production of a new tetravalent vaccine targeting fimbriae and enterotoxin of enterotoxigenic Escherichia coli.

Enterotoxigenic Escherichia coli (ETEC) is an important type of pathogenic bacteria that causes diarrhea in pigs. The objective of this study was to prepare a novel tetravalent vaccine to effectively prevent piglet diarrhea caused by E. coli. In order to realize the production of K88ac-K99-ST1-LTB tetravalent inactivated vaccine, the biological characteristics, stability, preservation conditions, and safety of the recombinant strain BL21(DE3) (pXKKSL4) were studied, and the vaccine efficacy and minimum immune dose were measured. The results indicated that the biological characteristics, target protein expression, and immunogenicity of the 1st to 10th generations of the strain were stable. Therefore, the basic seed generation was preliminarily set as the 1st to 10th generations. The results of the efficacy tests showed that the immune protection rate could reach 90% with 1 minimum lethal dose (MLD) virulent strain attack in mice. The immunogenicity was stable, and the minimum immune dose was 0.1 mL per mouse. Our research showed that the genetically engineered vaccine developed in this way could prevent piglet diarrhea caused by enterotoxigenic E. coli through adhesin and enterotoxin. In order to realize industrial production of the vaccine as soon as possible, we conducted immunological tests and production process research on the constructed K88ac-K99-ST1-LTB tetravalent inactivated vaccine. The results of this study provide scientific experimental data for the commercial production of vaccines and lay a solid foundation for their industrial production.

Escherichia coli entérotoxinogènes (ETEC) est un type important de bactéries pathogènes qui cause de la diarrhée chez les porcs. L'objectif de l'étude était de préparer un nouveau vaccin tétravalent pour prévenir efficacement la diarrhée causée par E. coli chez les porcelets. Afin de réaliser la production du vaccin tétravalent inactivé K88ac-K99-ST1-LTB, les caractéristiques biologiques, la stabilité, les conditions de conservation, et la sécurité de la souche recombinante (BL21(DE3)(pXKKSL4) ont été étudiées et l'efficacité du vaccin et la dose immunitaire minimum ont été mesurées. Les résultats indiquent que les caractéristiques biologiques, l'expression des protéines cibles, et l'immunogénicité de la 1ère à la 10e génération de la souche étaient stables. Ainsi, la génération germinale de base a été établie de manière préliminaire comme étant de la 1ère à la 10e générations. Les résultats des tests d'efficacité ont démontré que le taux de protection immunitaire pouvait atteindre 90 % avec une attaque au moyen de 1 dose léthale minimale (MLD) d'une souche virulente chez les souris. L'immunogénicité était stable et la dose immunitaire minimum était de 0,1 mL par souris. Nos travaux ont démontré que le vaccin génétiquement élaboré développé de cette façon pourrait prévenir la diarrhée chez les porcelets causée par des E. coli entérotoxigénique via les adhésines et les entérotoxines. Afin d'atteindre la production industrielle de ce vaccin aussitôt que possible, nous avons mené des tests immunologiques et de la recherche sur le processus de production du vaccin tétravalent inactivé K88ac-K99-ST1-LTB. Les résultats de la présente étude fournissent des données scientifiques expérimentales pour la production commerciale de vaccins et jettent une base solide pour leur production industrielle.(Traduit par Docteur Serge Messier).

Review of advances in molecular structure and biological function of alpha toxin of Clostridium perfringens.

Alpha toxin has become the subject of research in recent years. The objective of this article was to review and summarize recent research on the molecular structure and biological function of the alpha toxin of Clostridium perfringens. This includes the work of our research team, as well as that of other researchers. Clostridium perfringens is an anaerobic, spore-forming, Gram-positive bacillus. It can cause various intestinal diseases, such as gas gangrene, food poisoning, non-foodborne diarrhea, and enteritis. Clostridium perfringens can be classified into 5 toxinotypes A, B, C, D, and E, based on the production of major toxins. Each type of C. perfringens produces alpha toxin, which is one of the most important lethal and dermonecrotic toxins and is considered a primary virulence factor. Alpha toxin is a multifunctional metalloenzyme with phospholipase C and sphingomyelinase activities that simultaneously hydrolyze phosphatidylcholine and sphingomyelin. It can therefore destroy the integrity of cell membranes and eventually cause cell lysis. The clinical effects of alpha toxins are characterized by cytotoxicity, hemolytic activity, lethality, skin necrosis, platelet aggregation, and increased vascular permeability. Future research will concentrate on the pathogenesis of a lpha toxin exposure, clarifying the interaction between alpha toxin and the cell membrane and investigating the mechanism of activating platelet function. This research will have substantial theoretical and practical value in controlling disease progression, identifying targeted therapeutic sites, and reducing the toxic effects of vaccines.

La toxine alpha est devenue l'objet de recherches ces dernières années. L'objectif de cet article était de passer en revue et de résumer les recherches récentes sur la structure moléculaire et la fonction biologique de la toxine alpha de Clostridium perfringens. Cela inclut les travaux de notre équipe de recherche, ainsi que ceux d'autres chercheurs. Clostridium perfringens est un bacille anaérobie, sporulé et à Gram positif. Il peut provoquer diverses maladies intestinales, telles que la gangrène gazeuse, une intoxication alimentaire, de la diarrhée non alimentaire et une entérite. Clostridium perfringens peut être classé en 5 toxinotypes A, B, C, D et E, en fonction de la production des principales toxines. Chaque type de C. perfringens produit de la toxine alpha, qui est l'une des toxines létales et dermonécrotiques les plus importantes et est considérée comme un facteur de virulence primaire. La toxine alpha est une métalloenzyme multifonctionnelle possédant des activités de phospholipase C et de sphingomyélinase qui hydrolysent simultanément la phosphatidylcholine et la sphingomyéline. Elle peut donc détruire l'intégrité des membranes cellulaires et éventuellement provoquer une lyse cellulaire. Les effets cliniques des toxines alpha sont caractérisés par une cytotoxicité, une activité hémolytique, une létalité, une nécrose cutanée, une agrégation plaquettaire et une augmentation de la perméabilité vasculaire. Les recherches futures se concentreront sur la pathogénèse de l'exposition à la toxine alpha, en clarifiant l'interaction entre la toxine alpha et la membrane cellulaire et en étudiant le mécanisme d'activation de la fonction plaquettaire. Ces recherches auront une valeur théorique et pratique substantielle pour contrôler la progression de la maladie, identifier les sites thérapeutiques ciblés et réduire les effets toxiques des vaccins.(Traduit par Docteur Serge Messier).

NPC1L1 Plays a Novel Role in Nonalcoholic Fatty Liver Disease.

Niemann-Pick C1-Like 1 (NPC1L1) is a key protein in the transport of cholesterol, which exists in the brush marginal membrane of the intestinal epithelial cells and the timid duct membrane of the liver. It affects cholesterol absorption and plasma low-density lipoprotein levels. Cholesterol is both an important component of the cell membrane and a precursor of bile acid and steroid hormone synthesis. Abnormal cholesterol metabolism is closely related to nonalcoholic steatohepatitis (NASH). NASH can progress to fibrosis and cirrhosis, with serious consequences. NPC1L1 is involved in the regulation of cholesterol and lipid metabolism and plays an important role in maintaining the balance of cholesterol metabolism in the body. It also plays an important role in some metabolic diseases such as nonalcoholic fatty liver disease, obesity, and hypercholesterolemia. Therefore, it is necessary to elucidate the molecular pathological mechanism of NPC1L1 in the regulation of cholesterol metabolism and the occurrence and development of NASH, which can provide a target for the development of novel drugs for the treatment of NASH and other diseases. More importantly, it helps to accelerate the development of drugs that regulate lipid metabolism at multiple levels and reduce liver steatosis, which is extremely important for the prevention and treatment of NASH and related severe metabolic diseases.

Preparation of novel trivalent vaccine against enterotoxigenic Escherichia coli for preventing newborn piglet diarrhea.

OBJECTIVE: To develop a trivalent genetically engineered inactivated Escherichia coli vaccine (K88ac-3STa-LTB) that neutralizes the STa toxin by targeting fimbriae and entertoxins for the treatment of enterotoxigenic E coli. ANIMALS: 18- to 22-g mice, rabbits, pregnant sows. PROCEDURES: Using PCR, the K88ac gene and LTB gene were cloned separately from the template C83902 plasmid. At the same time, the 3 STa mutant genes were also amplified by using the gene-directed mutation technology. Immune protection experiments were performed, and the minimum immune dose was determined in mice and pregnant sows. RESULTS: The ELISA test could be recognized by the STa, LTB, and K88ac antibodies. Intragastric administration in the suckling mouse confirmed that the protein had lost the toxicity of the natural STa enterotoxin. The results of the immune experiments showed that K88ac-3STa-LTB protein could stimulate rabbits to produce serum antibodies and neutralize the toxicity of natural STa enterotoxin. The efficacy test of the K88ac-3STa-LTB-inactivated vaccine showed that the immune protection rate of the newborn piglets could reach 85% on the first day after suckling. At the same time, it was determined that the minimum immunization doses for mice and pregnant sows were 0.2 and 2.5 mL, respectively. CLINICAL RELEVANCE: This research indicates that the K88ac-3STa-LTB trivalent genetically engineered inactivated vaccine provides a broad immune spectrum for E coli diarrhea in newborn piglets and prepares a new genetically engineered vaccine candidate strain for prevention of E coli diarrhea in piglets.

Development of a new candidate vaccine against piglet diarrhea caused by Escherichia coli.

Enterotoxigenic Escherichia coli (ETEC) is an important type of pathogenic bacteria that causes diarrhea in humans and young livestock. The pathogen has a high morbidity and mortality rate, resulting in significant economic losses in the pig industry. To effectively prevent piglet diarrhea, we developed a new tetravalent genetically engineered vaccine that specifically targets ETEC. To eliminate the natural toxin activity of ST1 enterotoxin and enhance the preventive effect of the vaccine, the mutated ST 1, K88ac, K99, and LT B genes were amplified by PCR and site-specific mutation techniques. The recombinant strain BL21(DE3)(pXKK3SL) was constructed and achieved high expression. Animal experiments showed that the inactivated vaccine had eliminated the natural toxin activity of ST1. The immune protection test demonstrated that the inclusion body and inactivated vaccine exhibited a positive immune effect. The protection rates of the inclusion body group and inactivated vaccine group were 96 and 98%, respectively, when challenged with 1 minimum lethal dose, indicating that the constructed K88ac-K99-3ST1-LTB vaccine achieved a strong immune effect. Additionally, the minimum immune doses for mice and pregnant sows were determined to be 0.2 and 2 mL, respectively. This study suggests that the novel K88ac-K99-3ST1-LTB vaccine has a wide immune spectrum and can prevent diarrhea caused by ETEC through enterotoxin and fimbrial pathways. The aforementioned research demonstrates that the K88ac-K99-3ST1-LTB vaccine offers a new genetically engineered vaccine that shows potential for preventing diarrhea in newborn piglets.

Glycyrrhizic acid ameliorates myocardial ischemic injury by the regulation of inflammation and oxidative state.

BACKGROUND: Glycyrrhizic acid (GA), a bioactive triterpenoid saponin isolated from the roots of licorice plants (Glycyrrhiza glabra), has been shown to exert a variety of pharmacological activities and is considered to have potential therapeutic applications. The purpose of the present study was to investigate the cardioprotective effect of GA on myocardial ischemia (MI) injury rats induced by isoproterenol (ISO), and explore the potential mechanisms underlying these effects. MATERIALS AND METHODS: The rats were randomized into five groups: control, ISO, ISO+diltiazem (10 mg/kg), ISO+GA (10 mg/kg), and ISO+GA (20 mg/kg). Electrocardiogram and histopathological examination were performed. Markers of cardiac marker enzymes (creatine kinase-MB, lactate dehydrogenase), oxidative stress (superoxide dismutase, malondialdehyde [MDA]), and inflammation (TNF-α, IL-1ß, and IL-6) were also measured in each group. Proteins involved in NF-κB and Nrf-2/HO-1 pathway were detected by Western blot. RESULTS: GA decreased the ST elevation induced by MI, decreased serum levels of creatine kinase, lactate dehydrogenase, malondialdehyde, IL-6, IL-1ß, and TNF-α, and increased serum superoxide dismutase and malondialdehyde activities. Furthermore, GA increased the protein levels of Nrf-2 and HO-1 and downregulated the phosphorylation of IκB, and NF-κB p65 in ISO-induced MI. CONCLUSION: These observations indicated that GA has cardioprotective effects against MI, and these effects might be related to the activation of Nrf-2/HO-1 and inhibition of NF-κB signaling pathway in the myocardium.

[Expression of alpha-toxin gene of Clostridium perfringens type A and its primary immunological protective function].

Alpha-toxin gene was amplified from chromosomal DNA of Clostridium perfringens type A by polymerase chain reaction (PCR). PCR product was inserted into vector pGEM-T directly. The cloned recombinant plasmid pXCPA02 possesses positive nucleotide sequence of alpha-toxin. A 1.2 kb alpha-toxin gene fragment was cleaved with restriction endonucleases Nco I /EcoR I from plasmid pXCPA02, and then inserted into an expression vector pET-28c which cleaved with Nco I /EcoR I by blunt-end ligation. The recombinant expression plasmid pXETA02 was studied in detail by restriction endonucleases analysis and nucleotide sequencing. The results showed that the recombinant expression pXETA02 possessed a positive alpha-toxin gene sequence and reading frame. BL21 (DE3) (pXETA02) could produce alpha-toxin and the expressed products were recognized by alpha-toxin monoclonal antibodies with ELISA and Western blot. The expression optimization result indicated that the alpha toxin gene expression optimized condition with IPTG induction is culture medium pH 7.5, culture temperature 37 degrees C, joining IPTG to final concentration 0.8 mmol/L when the recombinant strain growth density OD600 achieved 0.8, and induction time 5h. The expression level of the alpha-toxin proteins were about 34.28% of total cellular protein with IPTG induction by SDS-PAGE and thin-layer gel scanning analysis. The alpha toxin gene expression optimized condition with lactose induction is culture medium pH 7.5, culture temperature 37 degrees C, joining lactose to final concentration 0.1 g/L when the recombinant strain growth density OD600 achieved 0.8, and induction time 5h. The expression level of the alpha-toxin proteins were about 23.82% of total cellular protein with lactose induction by SDS-PAGE and thin-layer gel scanning analysis. More importantly, Immunization in a mouse model with crude preparation containing the alpha-toxin protein inclusion bodies or inactivated recombinant strain induced protection against at least 1 MLD of the toxin from Clostridium perfringens type A.

[Fusion of betal-toxin gene and beta2-toxin gene from Clostridium perfringens type C].

Betal-toxin and beta2-toxin genes from chromosomal DNA of Clostridium perfringens type C were amplified by PCR, PCR products were cleaved with restriction endonucleases and recovered. The recombinant plasmid pETXB1-2 containing beta1-beta2 fusion genes was constructed by recombinant technique and then transformed into Escherichia coli BL21 (DE3). The beta1-beta2 fusion proteins were expressed in recombinant strain BL21 (DE3) (pETXB1-2), and the expression level of the beta1-beta2 fusion proteins was about 15.36% of total cellular protein by SDS-PAGE and thin-layer gel scanning analysis. More importantly, immunization in a mouse model with crude preparation containing the fusion protein inclusion bodies or inactivated recombinant strain induced protection against at least 1 MLD of the toxin from Clostridium perfringens type C. Hence the fusion proteins possess a good immunogenicity. The constructed recombinant strain BL21 (DE3) (pETXB1-2) can be used as a candidate of vaccine strain.