Lysis Gene Research Articles

Identification of the Burkholderia pseudomallei bacteriophage ST79 lysis gene cassette.

To identify and characterize the lysis gene cassette from the bacteriophage ST79 that lyses Burkholderia pseudomallei. Approximately 1·5kb of ST79 lysis genes were identified from the phage genome data. It was composed of holin, peptidase M15A or endolysin, lysB and lysC. Each gene and its combinations were cloned into Escherichia coli and the lytic effects were measured. Co-expression of holin and peptidase M15A showed the highest lysis activity. Expression of holin, lysB/C or holin-peptidase M15A-lysB/lysC lysed the E.coli membrane, whereas peptidase M15A alone did not. The predicted transmembrane structures of holin and lysB/C indicated that they could be inserted into the bacterial membrane to form pores, affecting cell permeability and causing lysis. This is the first report of an investigation into the lysis genes of B.pseudomallei's lytic phage using E.coli as a model. Burkholderia pseudomallei, a Gram-negative bacterium causing an infectious disease, is intrinsically resistant to several antibiotics, and a vaccine is not available. The lysis genes of ST79, the first reported lytic bacteriophage of B.pseudomallei, were characterized. The development of ST79 as an alternative treatment for skin ulceration, for example, or to be used as a gene cloning tool for B.pseudomallei may be possible with this knowledge.

Fed-Batch Production of Bacterial Ghosts Using Dielectric Spectroscopy for Dynamic Process Control.

The Bacterial Ghost (BG) platform technology evolved from a microbiological expression system incorporating the ϕX174 lysis gene E. E-lysis generates empty but structurally intact cell envelopes (BGs) from Gram-negative bacteria which have been suggested as candidate vaccines, immunotherapeutic agents or drug delivery vehicles. E-lysis is a highly dynamic and complex biological process that puts exceptional demands towards process understanding and control. The development of a both economic and robust fed-batch production process for BGs required a toolset capable of dealing with rapidly changing concentrations of viable biomass during the E-lysis phase. This challenge was addressed using a transfer function combining dielectric spectroscopy and soft-sensor based biomass estimation for monitoring the rapid decline of viable biomass during the E-lysis phase. The transfer function was implemented to a feed-controller, which followed the permittivity signal closely and was capable of maintaining a constant specific substrate uptake rate during lysis phase. With the described toolset, we were able to increase the yield of BG production processes by a factor of 8–10 when compared to currently used batch procedures reaching lysis efficiencies >98%. This provides elevated potentials for commercial application of the Bacterial Ghost platform technology.

Generation and use of Edwardsiella ictaluri ghosts as a vaccine against enteric septicemia of catfish (ESC)

The enteric septicemia of channel catfish, caused by Edwardsiella ictaluri, is one of the most severe diseases in channel catfish worldwide. Currently, a safe and highly effective vaccine is urgently needed for the control of this disease. In this study, E. ictaluri ghosts (EIGs) were first generated by PhiX174 lysis gene E, and the hematological indices and relative percent of survival (RPS) were examined in channel catfish (Ictalurus punctatus) after immunization. Generation of ghosts in the transformant of E. ictaluri carrying the plasmid pBV-lysisE was enhanced by increasing the incubation temperature up to 42°C. Lysis of E. ictaluri occurred 2h after induction and the process was complete in 6h. The efficiency of ghost induction in non-lyophilized E. ictaluri was 99.997%. Additionally, no bacterial growth was detected by culture on BHI plates after lyophilization of the ghosts. The immune response of channel catfish immunized with the E. ictaluri ghosts indicated that the number of erythrocytes and leucocytes reached a maximum value of 3.53×106 and 5.25×105cell/ml, at day 4 post-immunization, respectively, which were both significantly higher than in the control group inoculated with PBS only (P<0.01). The percentage of monocyte and neutrophils reached 7.33±1.52% and 26.3±2.08% at day 4 post-immunization, respectively. The phagocytic percentage (PP) and phagocytic index (PI) reached maximum values of 49.33±1.52% and 5.67±1.15, respectively, which were significantly higher than in control group (P<0.01). The percentage of lymphocytes and the serum antibody titers also increased significantly and peaked at 61.33±0.58% and a titer of 1:682.67 at day 21 post-immunization, respectively. The challenge evaluation showed that the RPS of immunized group was 89.3%. These results demonstrated that EIGs could induce significant immunological responses in channel catfish that resulted in high protection and suggest that EIGs may be a potential vaccine against ESC in channel catfish. Statement of relevanceIn the paper, we illustrated the generation method of Edwardsiella ictaluri ghosts and the immunological responses and protection in channel catfish after being immunized with E. ictaluri ghosts. The result of this paper indicated that E. ictaluri ghosts would be an effective approach for preventing ESC in channel catfish in the future.

Temperate phages promote colicin-dependent fitness of Salmonella enterica serovar Typhimurium.

Bacteria employ bacteriocins for interference competition in microbial ecosystems. Colicin Ib (ColIb), a pore-forming bacteriocin, confers a significant fitness benefit to Salmonella enterica serovar Typhimurium (S. Tm) in competition against commensal Escherichia coli in the gut. ColIb is released from S. Tm into the environment, where it kills susceptible competitors. However, colicin-specific release proteins, as they are known for other colicins, have not been identified in case of ColIb. Thus, its release mechanism has remained unclear. In the current study, we have established a new link between ColIb release and lysis activity of temperate, lambdoid phages. By the use of phage-cured S. Tm mutant strains, we show that the presence of temperate phages and their lysis genes is necessary and sufficient for release of active ColIb into the culture supernatant. Furthermore, phage-mediated lysis significantly enhanced S. Tm fitness in competition against a ColIb-susceptible competitor. Finally, transduction with the lambdoid phage 933W rescued the defect of E. coli strain MG1655 with respect to ColIb release. In conclusion, ColIb is released from bacteria in the course of phage lysis. Our data reveal a new mechanism for colicin release and point out a novel function of temperate phages in enhancing colicin-dependent bacterial fitness.

Natural mummification of the human gut preserves bacteriophage DNA.

The natural mummification process of the human gut represents a unique opportunity to study the resulting microbial community structure and composition. While results are providing insights into the preservation of bacteria, fungi, pathogenic eukaryotes and eukaryotic viruses, no studies have demonstrated that the process of natural mummification also results in the preservation of bacteriophage DNA. We characterized the gut microbiome of three pre-Columbian Andean mummies, namely FI3, FI9 and FI12, and found sequences homologous to viruses. From the sequences attributable to viruses, 50.4% (mummy FI3), 1.0% (mummy FI9) and 84.4% (mummy FI12) were homologous to bacteriophages. Sequences corresponding to the Siphoviridae, Myoviridae, Podoviridae and Microviridae families were identified. Predicted putative bacterial hosts corresponded mainly to the Firmicutes and Proteobacteria, and included Bacillus, Staphylococcus, Clostridium, Escherichia, Vibrio, Klebsiella, Pseudomonas and Yersinia. Predicted functional categories associated with bacteriophages showed a representation of structural, replication, integration and entry and lysis genes. The present study suggests that the natural mummification of the human gut results in the preservation of bacteriophage DNA, representing an opportunity to elucidate the ancient phageome and to hypothesize possible mechanisms of preservation.

Transcriptomic Characterization of an Infection of Mycobacterium smegmatis by the Cluster A4 Mycobacteriophage Kampy.

The mycobacteriophages, phages that infect the genus Mycobacterium, display profound genetic diversity and widespread geographical distribution, and possess significant medical and ecological importance. However, most of the majority of functions of mycobacteriophage proteins and the identity of most genetic regulatory elements remain unknown. We characterized the gene expression profile of Kampy, a cluster A4 mycobacteriophage, during infection of its host, Mycobacterium smegmatis, using RNA-Seq and mass spectrometry. We show that mycobacteriophage Kampy transcription occurs in roughly two phases, an early phase consisting of genes for metabolism, DNA synthesis, and gene regulation, and a late phase consisting of structural genes and lysis genes. Additionally, we identify the earliest genes transcribed during infection, along with several other possible regulatory units not obvious from inspection of Kampy's genomic structure. The transcriptional profile of Kampy appears similar to that of mycobacteriophage TM4 but unlike that of mycobacteriophage Giles, a result which further expands our understanding of the diversity of mycobacteriophage gene expression programs during infection.

Saccharomyces cerevisiae Ghosts Using the Sponge-Like Re-Reduced Protocol

Sponge-Like protocol for Ghosts preparation showing an increasing interest while it exceed the range of the E lysis gene protocol for Bacterial Ghosts preparation which is restricted only to gram-negative bacteria. The protocol can be used for nearly all bacterial strains. In this study, it succeeded for the first time to produce ghosts from Eukaryotic cell. In this study, S. cerevisiae yeast was turned to Ghost cells using Sponge-Like protocol for Ghosts preparation. However, centrifugation step was eliminated to avoid self-adhering or shrinking of the yeast empty cells. Instead, decantation was used. One unique properties of the yeast is that, it is able to decant. The protocol for ghost cells preparation was also reduced to use only the Minimum Inhibitory Concentration (MIC) of each of NaOH, SDS, NaHCO 3 and H 2 O 2 . NaHCO 3 was used instead of CaCO 3 due to the variation in the cell wall between the prokaryotic (Bacteria) and the eukaryotic (yeast) cells. Light and Scanning electron microscope were used to evaluate the quality of the S. cerevisiae Ghosts (S.c.Gs). Spectrophotometer was used to evaluate the amount of the realized DNA and Protein. The study show successful yeast ghost preparation with correct 3D structure.

Lysis to Kill: Evaluation of the Lytic Abilities, and Genomics of Nine Bacteriophages Infective for Gordonia spp. and Their Potential Use in Activated Sludge Foam Biocontrol.

Nine bacteriophages (phages) infective for members of the genus Gordonia were isolated from wastewater and other natural water environments using standard enrichment techniques. The majority were broad host range phages targeting more than one Gordonia species. When their genomes were sequenced, they all emerged as double stranded DNA Siphoviridae phages, ranging from 17,562 to 103,424 bp in size, and containing between 27 and 127 genes, many of which were detailed for the first time. Many of these phage genomes diverged from the expected modular genome architecture of other characterized Siphoviridae phages and contained unusual lysis gene arrangements. Whole genome sequencing also revealed that infection with lytic phages does not appear to prevent spontaneous prophage induction in Gordonia malaquae lysogen strain BEN700. TEM sample preparation techniques were developed to view both attachment and replication stages of phage infection.

Abstract 5326: Intracellular bacterial delivery of a NIPP1-peptide kills tumor cells

Abstract Protein phosphatase-1 (PP1) is a cancer target because it is involved in many cell signaling pathways. Its activity is tightly regulated by its interaction partners, mainly via the RVxF-binding motif. RVxF-containing peptides deregulate PP1 and have therapeutic potential as antagonists of increased cancer kinase signaling. Because PP1 is responsible for more than half of the dephosphorylations on Ser/Thr sites, it is essential in all eukaryotic cells and it is difficult to target systemically. Moreover, delivering peptides to cells extracellularly is inefficient because of poor cell permeability and proteolytic instability. To specifically transport therapeutic peptides into cancer cells, we engineered bacteria to be intracellular delivery vectors. A bacterial delivery system (BDS) was designed by creating a strain that lyses after cell invasion and releases its contents into the cytoplasm of cancer cells. A BDS strain was then manipulated to express a peptide containing the RVxF motif of Nuclear Inhibitor of PP1 (NIPP1; AA 142-224). The therapeutic potential of this strain was tested on MCF-7 cell monolayers and on 3D tumor tissue. The BDS was cloned by inserting the bacterial phage lysis gene E under the control of the sseJ promoter, a Salmonella promoter that is activated after cell invasion. The specificity of the sseJ promoter was tested by inserting GFP under its control and infecting MCF-7 cancer cells with Salmonella containing the plasmid. All intracellular bacteria expressed GPF after 4 hours of infection, while no fluorescence was measured in the bacteria outside the mammalian cells. After infection, the created BDS lysed in 78% of invaded cells. BDS delivery of the NIPP1-peptide to MCF-7 cancer cells killed 41% of infected cells while infection with control, empty BDS did not result in any death. When treating tumor tissue with BDS expressing NIPP1-peptide, 39% of tumor tissue was killed after 9.5 hours, compared to 8% when treated with BDS alone. These results indicate that targeting phosphatases with intracellular peptide delivery by bacteria is feasible and reduces tumor tissue viability. Citation Format: Nele Van Dessel, Neil S. Forbes. Intracellular bacterial delivery of a NIPP1-peptide kills tumor cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5326. doi:10.1158/1538-7445.AM2015-5326

Three of a Kind: Genetically Similar Tsukamurella Phages TIN2, TIN3, and TIN4.

Three Tsukamurella phages, TIN2, TIN3, and TIN4, were isolated from activated sludge treatment plants located in Victoria, Australia, using conventional enrichment techniques. Illumina and 454 whole-genome sequencing of these Siphoviridae viruses revealed that they had similar genome sequences, ranging in size between 76,268 bp and 76,964 bp. All three phages shared 74% nucleotide sequence identity to the previously described Gordonia phage GTE7. Genome sequencing suggested that phage TIN3 had suffered a mutation in one of its lysis genes compared to the sequence of phage TIN4, to which it is genetically very similar. Mass spectroscopy data showed the unusual presence of a virion structural gene in the DNA replication module of phage TIN4, disrupting the characteristic modular genome architecture of Siphoviridae phages. All three phages appeared highly virulent on strains of Tsukamurella inchonensis and Tsukamurella paurometabola.

Utilization of a Modified Phage E Protein Lysis System Accounts for Increased Biomass in Salmonella Gallinarum Ghosts.

A major limiting issue of bacterial ghost technology involves the stable maintenance of Phix174 lysis gene E expression. Unwanted leaky expression of gene E in the absence of induction temperature results in reduced biomass production of host bacterium, consequently leading to the lower yield of bacterial ghost. To mitigate the leaky expression status of lysis gene E, we utilized a novel E-lysis system in which gene E is located between sense λpR promoter with a CI857 regulator and antisense ParaBAD promoter with the AraC regulator. In the presence of L-arabinose at 28 C, unwanted transcription of lysis gene E from λpR promoter is repressed by a simultaneous transcription event from ParaBAD promoter by means of anti-sense RNA-mediated inhibition. Tight repression of lysis gene E in the absence of induction temperature resulted in higher bacterial cell number in culture suspension and, consequently, higher production of Salmonella Gallinarum (SG) ghost biomass. The safety and protective efficacy of the SG ghost vaccine were further examined in chickens. All of the immunized chickens showed significantly higher mucosal and systemic antibody responses accompanied by a potent antigen-specific lymphocyte proliferative response. Vaccination of chickens with SG ghost preparation offered efficient protection against wild-type SG challenge.

The lysis cassette of DLP12 defective prophage is regulated by RpoE.

Expression of the lysis cassette (essD, ybcT, rzpD/rzoD) from the defective lambdoid prophage at the 12th minute of Escherichia coli's genome (DLP12) is required in some strains for proper curli expression and biofilm formation. Regulating production of the lytic enzymes encoded by these genes is critical for maintaining cell wall integrity. In lambdoid phages, late-gene regulation is mediated by the vegetative sigma factor RpoD and the lambda antiterminator Qλ. We previously demonstrated that DLP12 contains a Q-like protein (QDLP12) that positively regulates transcription of the lysis cassette, but the sigma factor responsible for this transcription initiation remained to be elucidated. In silico analysis of essDp revealed the presence of a putative - 35 and - 10 sigma site recognized by the extracytoplasmic stress response sigma factor, RpoE. In this work, we report that RpoE overexpression promoted transcription from essDp in vivo, and in vitro using purified RNAP. We demonstrate that the - 35 region is important for RpoE binding in vitro and that this region is also important for QDLP12-mediated transcription of essDp in vivo. A bacterial two-hybrid assay indicated that QDLP12 and RpoE physically interact in vivo, consistent with what is seen for Qλ and RpoD. We propose that RpoE regulates transcription of the DLP12 lysis genes through interaction with QDLP12 and that proper expression is dependent on an intact - 35 sigma region in essDp. This work provides evidence that the unique Q-dependent regulatory mechanism of lambdoid phages has been co-opted by E. coli harbouring defective DLP12 and has been integrated into the tightly controlled RpoE regulon.

Immune responses and protection induced by Brucella suis S2 bacterial ghosts in mice

With the purpose of generating Brucella suis bacterial ghosts and investigating the immunogenicity of bacterial ghosts as a vaccine candidate, the lysis gene E and temperature-sensitive regulator cassette were cloned into a shuttle plasmid, pBBR1MCS-2, for construction of a recombinant temperature-sensitive shuttle lysis plasmid, pBBR1MCS-E. pBBR1MCS-E was then introduced into attenuated B. suis live vaccine S2 bacteria, and the resultant transformants were used for production of B. suis ghosts (BSGs) by inducing lysis gene E expression. The BSGs were characterized by observing their morphology by transmission electron microscopy. The safety and immunogenicity of BSGs were further evaluated using a murine model, the result suggested that BSG was as safe as formalin-killed B. suis. In mice, BSG demonstrated a similar capacity of inducing pathogen-specific serum IgG antibody response, spleen CD3+ and CD4+ T cell responses, induce secretion of gamma interferon and interleukin-4, and protection levels against Brucella melitensis 16M challenge, as the attenuated B. suis live vaccine. These data suggesting that BSG could confer protection against Brucella infection in a mouse model of disease and may be developed as a new vaccine candidate against Brucella infection.

Improved Escherichia coli Bactofection and Cytotoxicity by Heterologous Expression of Bacteriophage ΦX174 Lysis Gene E.

Bactofection offers a gene delivery option particularly useful in the context of immune modulation. The bacterial host naturally attracts recognition and cellular uptake by antigen presenting cells (APCs) as the initial step in triggering an immune response. Moreover, depending on the bacterial vector, molecular biology tools are available to influence and/or overcome additional steps and barriers to effective antigen presentation. In this work, molecular engineering was applied using Escherichia coli as a bactofection vector. In particular, the bacteriophage ΦX174 lysis E (LyE) gene was designed for variable expression across strains containing different levels of lysteriolysin O (LLO). The objective was to generate a bacterial vector with improved attenuation and delivery characteristics. The resulting strains exhibited enhanced gene and protein release and inducible cellular death. In addition, the new vectors demonstrated improved gene delivery and cytotoxicity profiles to RAW264.7 macrophage APCs.

Amount of colicin release in Escherichia coli is regulated by lysis gene expression of the colicin E2 operon.

The production of bacteriocins in response to worsening environmental conditions is one means of bacteria to outcompete other microorganisms. Colicins, one class of bacteriocins in Escherichia coli, are effective against closely related Enterobacteriaceae. Current research focuses on production, release and uptake of these toxins by bacteria. However, little is known about the quantitative aspects of these dynamic processes. Here, we quantitatively study expression dynamics of the Colicin E2 operon in E. coli on a single cell level using fluorescence time-lapse microscopy. DNA damage, triggering SOS response leads to the heterogeneous expression of this operon including the cea gene encoding the toxin, Colicin E2, and the cel gene coding for the induction of cell lysis and subsequent colicin release. Advancing previous whole population investigations, our time-lapse experiments reveal that at low exogenous stress levels all cells eventually respond after a given time (heterogeneous timing). This heterogeneous timing is lost at high stress levels, at which a synchronized stress response of all cells 60 min after induction via stress can be observed. We further demonstrate, that the amount of colicin released is dependent on cel (lysis) gene expression, independent of the applied exogenous stress level. A heterogeneous response in combination with heterogeneous timing can be biologically significant. It might enable a bacterial population to endure low stress levels, while at high stress levels an immediate and synchronized population wide response can give single surviving cells of the own species the chance to take over the bacterial community after the stress has ceased.

A new enterotoxigenic Escherichia coli vaccine candidate constructed using a Salmonella ghost delivery system: Comparative evaluation with a commercial vaccine for neonatal piglet colibacillosis

In this study, a comparative evaluation between a Salmonella ghost vaccine expressing enterotoxigenic Escherichia coli (ETEC) fimbrial antigens and a commercial ETEC vaccine was conducted in neonatal piglets. Genes encoding the ETEC K88ab, K88ac, K99, FasA, and F41 fimbrial proteins were individually cloned into an expression/ghost plasmid (pJHLP184) carrying the pBR origin, asd, the ompA signal sequence to direct antigens to the cell membrane, cI857/λPR promoter, araC ParaBAD, and the phiX174 lysis gene E. Individual clones were subsequently used to electroporate a Δasd S. Typhimurium strain, and positive clones were used to generate Salmonella ghosts. Pregnant sows (n=12) were equally divided into four groups. Pregnant sows were primed and boosted at 11 and 14 weeks of pregnancy, respectively. Group A, B, and C sows were intramuscularly inoculated with PBS as a control, a commercial vaccine, and with 2×1010 ghost cells, respectively, while group D sows were orally immunized with 2×1010 ghost cells. All the vaccinated sows and their offspring exhibited increased ETEC fimbrial antigen antibody levels relative to those in the unimmunized group A. Especially, serum IgG and colostrum IgA levels in the group D sows and serum IgG and IgA levels in their piglets were significantly higher than those in control group sows and offspring, respectively. The levels of interleukin-4 against all the fimbrial proteins in peripheral blood lymphocytes of group D sows also increased significantly, whereas no difference between the control group and any of the immunized groups was detected for interferon-γ. In addition, the piglets of group D did not experience diarrhea following challenge with virulent ETEC strains. Diarrhea was observed in 88.9%, 30.4%, and 23.5% of the piglets in groups A, B and C, respectively. Mortality was observed in 16.7% and 5.9% of the piglets in groups A and C, respectively. These findings indicate that immunization of sows with the ghost vaccine candidate, especially by the oral route, can effectively protect their offspring against E. coli colibacillosis.

Systematic approach to Escherichia coli cell population control using a genetic lysis circuit.

BackgroundCell population control allows for the maintenance of a specific cell population density. In this study, we use lysis gene BBa_K117000 from the Registry of Standard Biological Parts, formed by MIT, to lyse Escherichia coli (E. coli). The lysis gene is regulated by a synthetic genetic lysis circuit, using an inducer-regulated promoter-RBS component. To make the design more easily, it is necessary to provide a systematic approach for a genetic lysis circuit to achieve control of cell population density.ResultsFirstly, the lytic ability of the constructed genetic lysis circuit is described by the relationship between the promoter-RBS components and inducer concentration in a steady state model. Then, three types of promoter-RBS libraries are established. Finally, according to design specifications, a systematic design approach is proposed to provide synthetic biologists with a prescribed I/O response by selecting proper promoter-RBS component set in combination with suitable inducer concentrations, within a feasible range.ConclusionThis study provides an important systematic design method for the development of next-generation synthetic gene circuits, from component library construction to genetic circuit assembly. In future, when libraries are more complete, more precise cell density control can be achieved.

Controlled Bacterial Lysis for Electron Tomography of Native Cell Membranes

Cryo-electron tomography (cryoET) has become a powerful tool for direct visualization of 3D structures of native biological specimens at molecular resolution, but its application is limited to thin specimens (<300 nm). Recently, vitreous sectioning and cryoFIB milling technologies were developed to physically reduce the specimen thickness; however, cryoET analysis of membrane protein complexes within native cell membranes remains a great challenge. Here, we use phage ΦX174 lysis gene E to rapidly produce native, intact, bacterial cell membranes for high resolution cryoET. We characterized E gene-induced cell lysis using FIB/SEM and cryoEM and showed that the bacteria cytoplasm was largely depleted through spot lesion, producing ghosts with the cell membranes intact. We further demonstrated the utility of E-gene-induced lysis for cryoET using the bacterial chemotaxis receptor signaling complex array. The described method should have a broad application for structural and functional studies of native, intact cell membranes and membrane protein complexes.

Icariin is a PPARα activator inducing lipid metabolic gene expression in mice.

Icariin is effective in the treatment of hyperlipidemia. To understand the effect of icariin on lipid metabolism, effects of icariin on PPARα and its target genes were investigated. Mice were treated orally with icariin at doses of 0, 100, 200, and 400 mg/kg, or clofibrate (500 mg/kg) for five days. Liver total RNA was isolated and the expressions of PPARα and lipid metabolism genes were examined. PPARα and its marker genes Cyp4a10 and Cyp4a14 were induced 2-4 fold by icariin, and 4-8 fold by clofibrate. The fatty acid (FA) binding and co-activator proteins Fabp1, Fabp4 and Acsl1 were increased 2-fold. The mRNAs of mitochondrial FA β-oxidation enzymes (Cpt1a, Acat1, Acad1 and Hmgcs2) were increased 2-3 fold. The mRNAs of proximal β-oxidation enzymes (Acox1, Ech1, and Ehhadh) were also increased by icariin and clofibrate. The expression of mRNAs for sterol regulatory element-binding factor-1 (Srebf1) and FA synthetase (Fasn) were unaltered by icariin. The lipid lysis genes Lipe and Pnpla2 were increased by icariin and clofibrate. These results indicate that icariin is a novel PPARα agonist, activates lipid metabolism gene expressions in liver, which could be a basis for its lipid-lowering effects and its beneficial effects against diabetes.

Characterization of a Salmonella Typhimurium ghost carrying an adjuvant protein as a vaccine candidate for the protection of chickens against virulent challenge

In this study we describe the generation of a safe, immunogenic, genetically inactivated Salmonella Typhimurium ghost vaccine candidate carrying the Escherichia coli heat-labile enterotoxin B subunit (LTB) protein as an adjuvant molecule. An asd+ p15A ori– plasmid pJHL187-LTB harbouring the E lysis gene cassette and a foreign antigen delivery cassette containing the eltB gene was used to transform a Δasd Salmonella Typhimurium (JOL1311) strain to construct the ghost strain, JOL1499. Incubation of mid-logarithmic phase JOL1499 cultures at 42°C resulted in co-expression of the eltB and E lysis genes, leading to the generation of Salmonella Typhimurium ghost cells carrying the LTB protein (Salmonella Typhimurium-LTB ghost). The production of LTB in Salmonella Typhimurium-LTB ghost preparations was confirmed by western blot analysis, and functional activity of the LTB protein to bind with GM1 receptors was determined by means of GM1 enzyme-linked immunosorbent assay. Efficacy of the Salmonella Typhimurium-LTB ghost as a vaccine candidate was evaluated in a chicken model using 56 chickens at 5 weeks old, which were divided into four groups (n = 14): group A was designated the non-vaccinated control group, whereas the birds in groups B, C, and D were immunized intramuscularly with 109, 108, and 107 ghost cells, respectively. Compared with the non-immunized chickens (group A), immunized chickens (groups B, C and D) exhibited increased titres of plasma IgG and intestinal secretory IgA antibodies. After oral challenge with 109 colony-forming units of a virulent Salmonella Typhimurium strain, the vaccinated group B birds showed a decrease in internal organ colonization with the challenge strain.