1,721,070 research outputs found
The regulation of alginate biosynthesis via cyclic di-GMP signaling
No full textBacterial alginates are anionic exopolysaccharides, which are produced by Pseudomonas and Azotobacter species. Bacterial cells embedded in extracellular polymeric substances such as alginates have a survival advantage as they are protected against various physical and chemical stresses as well as the immune system. In the model organism P. aeruginosa, alginate is polymerized and secreted by a multiprotein complex spanning the entire bacterial envelope. The ubiquitous second messenger cyclic di-GMP is required for activation of alginate production. In this chapter, after a brief overview on alginates, their general properties, biological functions and applications, we will discuss the importance of alginate production and its regulation via cyclic di-GMP signaling during bacterial pathogenesis, which implies biofilm formation coinciding with chronic infection. We will review the current understanding of the molecular pathways controlling the cyclic di- GMP-dependent regulation of alginate production including (1) diguanylate cyclases and phosphodiesterases, which control cellular levels of cyclic di-GMP, (2) the cyclic di-GMP receptor/effector protein Alg44 that senses cyclic di-GMP, while it interacts with other protein subunits to constitute the alginate biosynthesis/ modification/secretion multiprotein complex at the bacterial envelope, (3) insights into structural elucidation of PilZ domain-containing Alg44 including mechanistic insights into cyclic di-GMP binding and activation of alginate polymerization, and (4) other regulator proteins whose functions are controlled by cyclic di-GMP levels and impact on alginate production.No Full Tex
Special Issue on the International Symposium on Biological Polymers 2018 (Editorial)
No full textThere is an increasing world‐wide interest in converting fossil‐based economies into sustainable bioeconomies. Renewable and biodegradable materials derived from natural resources play an import part in this process. The 16th International Symposium on Biopolymer (ISBP2018) held in Beijing (China) and hosted by a world‐leading biopolymer expert Professor George Guo‐Qiang Chen (Tsinghua University) attracted renowned biopolymer scientists from across the world. This special issue follows up on exciting biopolymer research and development advances presented at ISPB2018. Biotechnological production of biopolymers and precursors for in vitro synthesis of polymers have been successfully commercialized by industry. Renewable biodegradable biopolymers are relevant not only toward gradually replacing oil‐based commodity products but are also considered as biocompatible biomaterials for high‐value medical applications. Extensive research and development efforts over the last few decades provided critical insight into the underlying molecular mechanisms of biosynthesis of biopolymers and key monomers that can be used in polymerization reactions. Knowledge about these molecular processes was utilized in metabolic engineering of microorganisms leading to the production of custom‐made biopolymers and development of strongly improved microbial production strains for industrial biotechnology.No Full Tex
Editorial: Pathway, Genetic and Process Engineering of Microbes for Biopolymer Synthesis (Editorial)
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Intranasal Delivery of Antigen-Coated Polymer Particles Protects against Pseudomonas aeruginosa Infection
No full textPseudomonas aeruginosa is an opportunistic human pathogen that is intrinsically resistant to multiple antibiotics, causing severe and persistent infections in immunocompromised individuals. This bacterium has been listed as a priority pathogen by the WHO in 2017, and there is no vaccine available for human use. In this study, 10 vaccine candidate antigens were selected for particulate vaccine design. We engineered Escherichia coli to assemble biopolymer particles (BPs) that were either coated with epitopes (Ag) derived from OprF/I-AlgE proteins or PopB or PopB-Ag or coated with single or double copies of epitopes (10Ag and 10Ag(2x)) derived from OprF, OprI, AlgE, OprL, PopB, PilA, PilO, FliC, Hcp1, and CdrA. Antigen-coated BPs showed a diameter of 0.93-1.16 μm with negative surface charge. Antigens attached to BPs were identified by mass spectrometry. Vaccination with BP-Ag, BP-PopB, BP-PopBAg, PB-10Ag, and BP-10Ag(2x) with and without Alhydrogel adjuvant induced significant antigen-specific humoral and cell-mediated immune responses in mice. All particulate vaccines with Alhydrogel induced protection in an acute pneumonia murine model of P. aeruginosa infection, contributing to up to 80% survival when administered intramuscularly, and the addition of Alhydrogel boosted immunity. The BP-10Ag(2x) vaccine candidate showed the best performance and even induced protective immunity in the absence of Alhydrogel. Intramuscular administration of the BP-10Ag(2x) without Alhydrogel vaccine resulted in 60% survival. Intranasal vaccination induced immunity, contributing to about 90% survival. Overall, our data suggest that vaccination with BPs coated with P. aeruginosa antigens induce protective immunity against P. aeruginosa infections. The possibility of intranasal delivery will strongly facilitate administration and use of BP vaccines.No Full Tex
Engineering antigens to assemble into polymer particle vaccines for prevention of streptococcus suis infection
No full textStreptococcus suis is a zoonotic pathogen affecting pigs and humans. This bacterium causes severe economic losses in the swine industry and poses a serious threat to public health and food safety. There is no effective commercial vaccine available for pigs or humans. In this study, we applied the biopolymer particle (BP) vaccine technology to incorporate seven conserved S. suis antigens (38 kDa protein (38), enolase (Enol), SSU1915, SSU1355, SSU0185, SSU1215, and SSU1773 (SSU1 and SSU2)). Two combinations of these antigens (38 and Enol; all SSU antigens designated as SSU1 and SSU2) were engineered to mediate production of BPs coated with either antigens 38 and Enol or SSU1 and SSU2 inside recombinant Escherichia coli. The isolated and purified empty BPs, 38-BP-Enol and SSU1-BP-SSU2, showed size ranges of 312–428 nm and 292–344 nm with and without the QuilA® adjuvant, respectively, and all showed a negative surface charge. Further characterization of purified BPs confirmed the presence of the expected antigen-comprising fusion proteins as assessed by tryptic peptide fingerprinting analysis using quadrupole time-of-flight mass spectrometry and im-munoblotting. Vaccination with 38-BP-Enol and SSU1-BP-SSU2 formulated with and without QuilA® adjuvant induced significant antigen-specific humoral immune responses in mice. Antigen-coated BPs induced significant and specific Ig (IgM + IgG) and IgG immune responses (1.0 × 106–1.0 × 107) when compared with mice vaccinated with empty BPs. Functionality of the immune response was confirmed in challenge experiments using an acute murine S. suis infection model, which showed 100% survival of the 38-BP-Enol and SSU1-BP-SSU2 vaccinated mice compared to 70% survival when vaccinated with empty BPs. Overall, our data suggest that S. suis antigen-coated BPs could be developed into particulate vaccines that induce protective immunity against S. suis infections.Full Tex
Bioengineered Polyhydroxyalkanoates as Immobilized Enzyme Scaffolds for Industrial Applications
No full textEnzymes function as biocatalysts and are extensively exploited in industrial applications. Immobilization of enzymes using support materials has been shown to improve enzyme properties, including stability and functionality in extreme conditions and recyclability in biocatalytic processing. This review focuses on the recent advances utilizing the design space of in vivo self-assembled polyhydroxyalkanoate (PHA) particles as biocatalyst immobilization scaffolds. Self-assembly of biologically active enzyme-coated PHA particles is a one-step in vivo production process, which avoids the costly and laborious in vitro chemical cross-linking of purified enzymes to separately produced support materials. The homogeneous orientation of enzymes densely coating PHA particles enhances the accessibility of catalytic sites, improving enzyme function. The PHA particle technology has been developed into a remarkable scaffolding platform for the design of cost-effective designer biocatalysts amenable toward robust industrial bioprocessing. In this review, the PHA particle technology will be compared to other biological supramolecular assembly-based technologies suitable for in vivo enzyme immobilization. Recent progress in the fabrication of biological particulate scaffolds using enzymes of industrial interest will be summarized. Additionally, we outline innovative approaches to overcome limitations of in vivo assembled PHA particles to enable fine-tuned immobilization of multiple enzymes to enhance performance in multi-step cascade reactions, such as those used in continuous flow bioprocessing.Full Tex
Pseudomonas aeruginosa Biofilms
No full textPseudomonas aeruginosa is an opportunistic human pathogen causing devastating acute and chronic infections in individuals with compromised immune systems. Its highly notorious persistence in clinical settings is attributed to its ability to form antibiotic-resistant biofilms. Biofilm is an architecture built mostly by autogenic extracellular polymeric substances which function as a scaffold to encase the bacteria together on surfaces, and to protect them from environmental stresses, impedes phagocytosis and thereby conferring the capacity for colonization and long-term persistence. Here we review the current knowledge on P. aeruginosa biofilms, its development stages, and molecular mechanisms of invasion and persistence conferred by biofilms. Explosive cell lysis within bacterial biofilm to produce essential communal materials, and interspecies biofilms of P. aeruginosa and commensal Streptococcus which impedes P. aeruginosa virulence and possibly improves disease conditions will also be discussed. Recent research on diagnostics of P. aeruginosa infections will be investigated. Finally, therapeutic strategies for the treatment of P. aeruginosa biofilms along with their advantages and limitations will be compiled
Polymeric nanoparticle vaccines to combat emerging and pandemic threats
No full textSubunit vaccines are more advantageous than live attenuated vaccines in terms of safety and scale-up manufacture. However, this often comes as a trade-off to their efficacy. Over the years, polymeric nanoparticles have been developed to improve vaccine potency, by engineering their physicochemical properties to incorporate multiple immunological cues to mimic pathogenic microbes and viruses. This review covers recent advances in polymeric nanostructures developed toward particulate vaccines. It focuses on the impact of microbe mimicry (e.g. size, charge, hydrophobicity, and surface chemistry) on modulation of the nanoparticles’ delivery, trafficking, and targeting antigen-presenting cells to elicit potent humoral and cellular immune responses. This review also provides up-to-date progresses on rational designs of a wide variety of polymeric nanostructures that are loaded with antigens and immunostimulatory molecules, ranging from particles, micelles, nanogels, and polymersomes to advanced core-shell structures where polymeric particles are coated with lipids, cell membranes, or proteins.No Full Tex
Self-assembled particulate vaccine elicits strong immune responses and reduces Mycobacterium avium subsp. paratuberculosis infection in mice
No full textMycobacterium avium subspecies paratuberculosis (MAP) causes chronic progressive granulomatous enteritis leading to diarrhoea, weight loss, and eventual death in ruminants. Commercially available vaccines provide only partial protection against MAP infection and can compromise the use of bovine tuberculosis diagnostic tests. Here, we report the development of a protein-particle-based vaccine containing MAP antigens Ag85A202–347-SOD1–72-Ag85B173–330-74F1–148+669–786 as a fusion (‘MAP fusion protein particle’). The fusion antigen displayed on protein particles was identified using mass spectrometry. Surface exposure and accessibility of the fusion antigen was confirmed by flow cytometry and ELISA. The MAP fusion protein particle vaccine induced strong antigen-specific T-cell immune responses in mice, as indicated by increased cytokine (IFN-γ and IL-17A) and costimulatory signals (CD40 and CD86) in these animals. Following MAP-challenge, a significant reduction in bacterial burden was observed in multiple organs of the mice vaccinated with the MAP fusion protein particle vaccine compared with the PBS group. The reduction in severity of MAP infection conferred by the MAP fusion protein particle vaccine was similar to that of Silirum and recombinant protein vaccines. Overall, the results provide evidence that MAP antigens can be engineered as a protein particulate vaccine capable of inducing immunity against MAP infection. This utility offers an attractive platform for production of low-cost particulate vaccines against other intracellular pathogens.Full Tex
Diphtheria Toxoid Particles as Q Fever Vaccine
No full textThere is an unmet need for a stable and nonreactogenic vaccine against the bioterrorism agent, Coxiella burnetii, causing Q fever. Here a safe, effective, and non-reactogenic Q fever vaccine is developed by employing self-assembled particles (CPs) composed of cross-reacting material 197, a nontoxic variant of diphtheria toxin. CPs are designed that incorporate selected C. burnetii antigens and assemble them inside engineered Escherichia coli at high yields. A cost-effective manufacturing process enables the production of CP-based Q fever vaccine candidates. Four vaccine candidates are developed, including a T-cell epitope-based vaccine (CP-COX), and one that comprises two immunodominant antigens, Com1 and YbgF. The latter is tested separately (CP-Com1, CP-YbgF) or as a mixture (CP-Com1/CP-YbgF). Initial immunogenicity studies in mice reveal that the mixed CP-Com1/YbgF elicits the highest antibody titers with a half maximal effective concentration (EC50) value of ≈100 000 and induction of TH1 and TH2 cytokines. CP-Com1/YbgF is further evaluated in guinea pigs, demonstrating its safety and efficacy, as shown by the absence of adverse reactions and a significant reduction in febrile responses compared to alum upon challenge with C. burnetii. Together, the study shows the potential of CPs for the development of a safe and immunogenic subunit Q fever vaccine.Full Tex
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