Chemical Targeting and Manipulation of Type III Secretion in the Phytopathogen Xanthomonas campestris for Control of Disease.

Xanthomonas campestris pv. campestris is the causative agent of black rot disease in crucifer plants. This Gram-negative bacterium utilizes the type III secretion system (T3SS), encoded by the hrp gene cluster, to aid in its resistance to host defenses and the ability to cause disease. The T3SS injects a set of proteins known as effectors into host cells that come into contact with the bacterium. The T3SS is essential for the virulence and hypersensitive response (HR) of X. campestris pv. campestris, making it a potential target for disease control strategies. Using a unique and straightforward high-throughput screening method, we examined a large collection of diverse small molecules for their potential to modulate the T3SS without affecting the growth of X. campestris pv. campestris. Screening of 13,129 different compounds identified 10 small molecules that had a significant inhibitory influence on T3SS. Moreover, reverse transcription-quantitative PCR (qRT-PCR) assays demonstrated that all 10 compounds repress the expression of the hrp genes. Interestingly, the effect of these small molecules on hrp genes may be through the HpaS and ColS sensor kinase proteins that are key to the regulation of the T3SS in planta Five of the compounds were also capable of inhibiting X. campestris pv. campestris virulence in a Chinese radish leaf-clipping assay. Furthermore, seven of the small molecules significantly weakened the HR in nonhost pepper plants challenged with X. campestris pv. campestris. Taken together, these small molecules may provide potential tool compounds for the further development of antivirulence agents that could be used in disease control of the plant pathogen X. campestris pv. campestris.IMPORTANCE The bacterium Xanthomonas campestris pv. campestris is known to cause black rot disease in many socioeconomically important vegetable crops worldwide. The management and control of black rot disease have been tackled with chemical and host resistance methods with variable success. This has motivated the development of alternative methods for preventing this disease. Here, we identify a set of novel small molecules capable of inhibiting X. campestris pv. campestris virulence, which may represent leading compounds for the further development of antivirulence agents that could be used in the control of black rot disease.

[Preparation Method and Quality Evaluation of Novel Frozen Human Platelets].

OBJECTIVE: To optimize the technical parameters related to the preparation of novel frozen human platelets and formulate corresponding protocol for its preparation. METHODS: Novel frozen human platelets were prepared with O-type bagged platelet-rich plasma (PRP), the key technical parameters (DMSO addition, incubation time, centrifugation conditions, etc.) of the preparation process were optimized, and the quality of the frozen platelets was evaluated by routine blood tests, apoptosis rate, platelet activation rate and surface protein expression level. RESULTS: In the preparation protocol of novel frozen human platelets, the operation of centrifugation to remove supernatant was adjusted to before the procedure of platelets freezing, and the effect of centrifugation on platelets was minimal when the centrifugation condition was 800×g for 8 min. In addition, platelets incubated with DMSO for 30 min before centrifugation exhibited better quality after freezing and thawing. The indexes of novel frozen human platelets prepared with this protocol remained stable after long-term cryopreservation. CONCLUSION: The preparation technique of novel frozen human platelets was established and the protocol was formulated. It was also confirmed that the quality of frozen platelets could be improved by incubating platelets with DMSO for 30 min and then centrifuging them at 800×g for 8 min in the preparation of novel frozen human platelets.

[Improvement of Preparation Method of Rats Platelet-Rich Plasma and Quality Detection].

OBJECTIVE: To optimize the single centrifugation preparation protocol of rat platelet-rich plasma (PRP). METHODS: The arterial blood of rats obtained by carotid artery intubation was collected by heparin sodium anticoagulant tubes, and then the blood divided into sterile EP tubes, adjusting the red blood cell concentration with normal saline, while rat PRP was prepared by centrifugation under different conditions (the centrifugal force was 200×g-240×g, and the centrifugal time was 8-12 min). Subsequently, the blood cell count and quality evaluation of anticoagulat whole blood and PRP were performed by hematology analyzer and flow cytometry, respectively, and the differences between different groups were compared. RESULTS: The red blood cell concentration to (5.5-6.5)×1012/L after anticoagulation of rat whole blood was good for PRP extraction. When the blood samples was centrifuged at 220×g for 10 min, the platelet recovery rate was the highestï¼»(53.52±0.63)%ï¼½. The level of apoptosis and activation of plateles in PRP were not significantly different compared to whole blood(P>0.05), and the release level of growth factor was significantly increased(P<0.05). CONCLUSION: It is a key to improve the PRP extraction efficiency by reducing the amount of mixed red blood cell, and this study successfully modified the preparation method of rat PRP, with platelets high recovery rate and stable quality.

Noninvasive molecular imaging of interferon beta activation in mouse liver.

BACKGROUND/AIMS: Interferon beta (IFN-ß) is the priming cytokine in the interferons (IFNs) response that plays essential roles in innate immune system. Only very few studies on IFN activation in animals have been reported before, therefore, we embarked to develop a novel method to dynamically examine IFN-ß activation in mouse liver by noninvasive molecular imaging. METHODS: Interferon beta promoter-directed firefly luciferase gene was integrated into chromosomes of hepatocytes by hydrodynamic injection. Mouse hepatitis virus type 3 (MHV-3) and polyinosinic-polycytidylic acid [poly(I:C)] were used to stimulate the activation of IFN-ß. Luciferase activity was used as an indicator of the IFN-ß promoter activity in vitro and in vivo. The expression level of IFN-ß in the sera and firefly luciferase in the liver was assessed by ELISA and bioluminescence imaging respectively. Western blot was used for detecting proteins expression. RESULTS: A rapid and elevated luciferase expression in the mouse liver induced by poly (I:C) and MHV-3 was detected by bioluminescence imaging. The detectable level of IFN-ß in the sera was not induced by MHV-3. Moreover, IFN-ß activation was significantly inhibited by the hepatitis C virus (HCV) NS3/4A protease in mouse liver. These results were consistent with IFN-ß production in the sera. Therefore, a novel visual method to monitor IFN-ß promoter activity was established in the current study. CONCLUSION: This novel sensitive method can be used for not only assessing IFN-ß activation or inhibition in the liver under different conditions, but also screening drug candidates of stimulating or inhibiting of IFN-ß production.

[Factors Affecting the Preservation of Human Peripheral Blood Mononuclear Cells at 4 ℃].

OBJECTIVE: To analyze the preservation effect and related influencing factors of human peripheral blood mononuclear cells under serum-free condition at 4 ℃. METHODS: Human peripheral blood mononuclear cells were isolated by density gradient centrifugation, and stored at 4 ℃ under different cell concentrations, supplemented with human serum albumin, and glucose. The cell viability, total cell number, viable cell number and cell phenotype were detected during preservation of 72 h. RESULTS: With the prolongation of storage time, the number of human peripheral blood mononuclear cells gradually decreased(r=0.982). Compared with the cell concentration of (5-6)×106 cells/ml, the cell number decreased more slowly when the cell storage concentration was (1-2)×106 cells/ml; Adding human serum albumin and glucose can effectively improve the survival rate of human peripheral blood mononuclear cells, among which 2% human serum albumin has a better preservation effect; Compared with the blank control group, the analysis results of cell subsets showed that the downward trends of NK cells and T cells were significantly slowed after adding albumin and glucose. CONCLUSION: The cell density of (1-2)×106/ml and 2% human serum albumin are more suitable for the preservation of PBMC, and 5% glucose can improve the preservation effect of human peripheral blood mononuclear cells at 4 ℃.

Bioluminescence imaging of hepatitis B virus enhancer and promoter activities in mice.

By bioluminescence imaging and hydrodynamic gene transfer technology, the activities of hepatitis B virus (HBV) promoters and the effects of HBV enhancers on these promoters in mice under true physiological conditions have been assessed. Our studies reveal that either of the two HBV enhancers can stimulate HBV major promoter activity in hepa 1-6 cells (in vitro) and in mouse liver (in vivo), and the enhancer effects on the three promoters (S1, S2 and X promoter) are markedly greater in vivo than in vitro. The two HBV enhancers have no cooperative action on HBV promoters in vitro or in vivo.

Phospholemman, a major regulator of skeletal muscle Na+/K+-ATPase, is not mutated in probands with hypokalemic periodic paralysis.

The pathogenesis of hypokalemic periodic paralysis (HypoPP) remains unclear. Though some mutations in skeletal muscle ion channels were revealed previously, the exact mechanism remains to be fully elucidated. Increased Na+/K+-ATPase activity in skeletal muscle is postulated to contribute to attacks of HypoPP. Before the link between Na+/K+-ATPase dysfunction and these ion channel mutations is established, mutations in Na+/K+-ATPase and their regulators are the first to be excluded. Phospholemman, which is a protein encoded by the FXYD domain-containing ion transport regulator 1 (FXYD1) gene, is predominantly expressed in skeletal muscle and is the major regulator of Na+/K+-ATPase. Therefore, the aim of the present study was to determine the genetic involvement of phospholemman in HypoPP development. Genomic DNA was extracted from the peripheral blood of five HypoPP probands with typical manifestations. The coding exons of FXYD1, exons 2-7, were polymerase chain reaction (PCR)-amplified and sequenced. No mutations were detected in FXYD1 in any of the subjects studied. To conclude, mutations in phospholemman encoding genes may not be involved with HypoPP and the relationship between phospholemman and Na+/K+-ATPase dysfunction in attacks of HypoPP requires further study.

Mutation analysis of CACNA1S and SCN4A in patients with hypokalemic periodic paralysis.

Mutations in CACNA1S (calcium channel, voltage­dependent, L type, alpha 1S subunit) and SCN4A (sodium channel, voltage­gated, type IV, alpha subunit) are associated with hypokalemic periodic paralysis (HPP). The aim of the current study was to investigate CACNA1S and SCN4A mutations in patients with HPP. Mutations in CACNA1S and SCN4A were detected in three familial hypokalemic periodic paralysis (FHPP) pedigrees and in two thyrotoxic hypokalemic periodic paralysis (THPP) pedigrees using polymerase chain reaction, DNA sequencing and sequence alignment with GenBank data. A single base mutation from cytosine to guanine at site 1582 was identified in exon 11 of CACNA1S in one FHPP pedigree, resulting in an arginine to glycine (R528G) substitution. A single base mutation from thymine to cytosine at site 2012 was identified in exon 12 of SCN4A in one THPP pedigree, resulting in a phenylalanine to serine (F671S) substitution. No mutations in CACNA1S or SCN4A were identified in the remaining three pedigrees. The present study indicated that CACNA1S and SCN4A mutations are relatively rare in patients with HPP, and further studies are required to determine whether these mutation­associated substitutions are representative of patients with HPP.

A mouse model for studying the clearance of hepatitis B virus in vivo using a luciferase reporter.

Hepatitis B virus(HBV) infection remains a global problem, despite the effectiveness of the Hepatitis B vaccine in preventing infection. The resolution of Hepatitis B virus infection has been believed to be attributable to virus-specific immunity. In vivo direct evaluation of anti-HBV immunity in the liver is currently not possible. We have developed a new assay system that detects HBV clearance in the liver after the hydrodynamic transfer of a reporter gene and over-length, linear HBV DNA into hepatocytes, followed by bioluminescence imaging of the reporter gene (Fluc). We employed bioluminescence detection of luciferase expression in HBV-infected hepatocytes to measure the Hepatitis B core antigen (HBcAg)-specific immune responses directed against these infected hepatocytes. Only HBcAg-immunized, but not mock-treated, animals decreased the amounts of luciferase expression, HBsAg and viral DNA from the liver at day 28 after hydrodynamic infection with over-length HBV DNA, indicating that control of luciferase expression correlates with viral clearance from infected hepatocytes.

Kinetics of interaction of HLA-B2705 with natural killer cell immunoglobulin-like receptor 3DS1.

The recognition of human leukocyte antigen (HLA) molecules by specific receptors is a crucial step in the regulation of natural killer (NK) cell function. Killer cell immunoglobulin-like receptor (KIR) 3DS1 is one of the activating receptors of NK cell and is implicated in slowing disease progression in HIV infection. KIR3DS1 play an important role in the outcome of multiple diseases associated with viral infections. In contrast to the inhibitory receptor, much less is known about the ligands of KIR3DS1. In order to achieve a better understanding of the biology of KIR3DS1 and its ligand systems, it is necessary to identify the ligands of KIR3DS1. In this work, we utilized recombinant HLA-B2705 molecules and DsbA-KIR3DS1 fusion protein to monitor the interaction between HLA-B2705 complexes and DsbA-KIR3DS1 using BIAcore 3000 SPR sensor and found that the specific binding between KIR3DS1 and HLA-B2705 existed and the affinity was 6.95x10(-6) mol//L. So we concluded that HLA-B2705 is a possible ligand of KIR3DS1.

Bioluminescence imaging allows monitoring hepatitis C virus core protein inhibitors in mice.

BACKGROUND: The development of small molecule inhibitors of hepatitis C virus (HCV) core protein as antiviral agents has been intensively pursued as a viable strategy to eradicate HCV infection. However, lack of a robust and convenient small animal model has hampered the assessment of in vivo efficacy of any antiviral compound. METHODOLOGY/PRINCIPAL FINDINGS: The objective of this work was to develop a novel method to screen anti-core protein siRNA in the mouse liver by bioluminescence imaging. The inhibitory effect of two shRNAs targeting the highly conserved core region of the HCV genome, shRNA452 and shRNA523, was examined using this method. In the transient mouse model, the effect of shRNA-523 was detectable at as early as 24 h and became even more pronounced at later time points. The effect of shRNA-452 was not detectable until 48 h post-transduction. In a stable mouse model, shRNA523 reduced luciferase levels by up to 76.4±26.0% and 91.8±8.0% at 6 h and 12 h after injection respectively, and the inhibitory effect persisted for 1 day after a single injection while shRNA-Scramble did not seem to have an effect on the luciferase activity in vivo. CONCLUSIONS/SIGNIFICANCE: Thus, we developed a simple and quantitative assay for real-time monitoring of HCV core protein inhibitors in mice.

Screening compounds against HCV based on MAVS/IFN-ß pathway in a replicon model.

AIM: To develop a sensitive assay for screening compounds against hepatitis C virus (HCV). METHODS: The proteolytic cleavage of NS3/4A on enhanced yellow fluorescent protein (eYFP)-mitochondrial antiviral signaling protein (MAVS) was examined by reporter enzyme secreted placental alkaline phosphatase (SEAP), which enabled us to perform ongoing monitoring of anti-HCV drugs through repeated chemiluminescence. Subcellular localization of eYFP-MAVS was assessed by fluorescence microscopy. Cellular localization and protein levels were examined by Western blotting. RESULTS: HCV NS3/4A protease cleaved eYFP-MAVS from mitochondria to block the activation of interferon (IFN)-ß promoter, thus resulting in downregulation of SEAP activity. The decrease in SEAP activity was proportional to the dose of active NS3/4A protease. Also this reporter assay was used to detect anti-HCV activity of IFN-α and cyclosporine A. CONCLUSION: Our data show that this reporter system is a sensitive and quantitative reporter of anti-HCV inhibitors. This system will constitute a new tool to allow the efficient screening of HCV inhibitors.