Assembly of Immunogenic Protein Particles toward Advanced Synthetic Vaccines.

Immunogenic carrier proteins such as the non-toxic diphtheria toxin variant, cross-reacting material 197 (CRM197), are widely used in subunit vaccine formulations to boost immunogenicity of chemically conjugated antigens. Conjugate vaccines are inherently expensive due to laborious manufacturing steps. Here, this work develops a particulate vaccine platform based on using engineered Escherichia coli to assemble CRM197-antigen fusion proteins into discrete submicron-sized particles. This approach enables precise loading of diverse antigens and epitopes enhancing their immunogenicity. A cost-effective, high-yield, and scalable biomanufacturing process is developed. Purified particulate CRM197-antigen vaccines are ambient-temperature stable. CRM197 particles incorporating pathogen-specific antigens or epitopes from SARS-CoV-2, Streptococcus pyogenes (group A), and Mycobacterium tuberculosis induced cell-mediated and humoral immune responses mediating protective immunity in respective animal models of infection. The CRM197 particle vaccine platform is versatile, enabling co-delivery of selected antigens/epitopes together with immunogenic CRM197 as discrete stable particles avoiding laborious manufacture of soluble CRM197 and antigen followed by chemical conjugation.

Bromotyrosine-Derived Metabolites from a Marine Sponge Inhibit Pseudomonas aeruginosa Biofilms.

Pseudomonas aeruginosa forms stable biofilms, providing a major barrier for multiple classes of antibiotics and severely impairing treatment of infected patients. The biofilm matrix of this Gram-negative bacterium is primarily composed of three major exopolysaccharides: alginate, Psl, and Pel. Here, we studied the antibiofilm properties of sponge-derived natural products ianthelliformisamines A-C and their combinations with clinically used antibiotics. Wild-type P. aeruginosa strain and its isogenic exopolysaccharide-deficient mutants were employed to determine the interference of the compounds with biofilm matrix components. We identified that ianthelliformisamines A and B worked synergistically with ciprofloxacin to kill planktonic and biofilm cells. Ianthelliformisamines A and B reduced the minimum inhibitory concentration (MIC) of ciprofloxacin to 1/3 and 1/4 MICs, respectively. In contrast, ianthelliformisamine C (MIC = 53.1 µg/mL) alone exhibited bactericidal effects dose-dependently on both free-living and biofilm populations of wild-type PAO1, PAO1ΔpslA (Psl deficient), PDO300 (alginate overproducing and mimicking clinical isolates), and PDO300Δalg8 (alginate deficient). Interestingly, the biofilm of the clinically relevant mucoid variant PDO300 was more susceptible to ianthelliformisamine C than strains with impaired polysaccharide synthesis. Ianthelliformisamines exhibited low cytotoxicity towards HEK293 cells in the resazurin viability assay. Mechanism of action studies showed that ianthelliformisamine C inhibited the efflux pump of P. aeruginosa. Metabolic stability analyses indicated that ianthelliformisamine C is stable and ianthelliformisamines A and B are rapidly degraded. Overall, these findings suggest that the ianthelliformisamine chemotype could be a promising candidate for the treatment of P. aeruginosa biofilms.

Engineered Mycobacterium tuberculosis antigen assembly into core-shell nanobeads for diagnosis of tuberculosis.

Despite recent advances in diagnosis, tuberculosis (TB) remains one of the ten leading causes of death worldwide. Here, we engineered Mycobacterium tuberculosis (Mtb) proteins (ESAT6, CFP10, and MTB7.7) to self-assemble into core-shell nanobeads for enhanced TB diagnosis. Respective purified Mtb antigen-coated polyester beads were characterized and their functionality in TB diagnosis was tested in whole blood cytokine release assays. Sensitivity and specificity were studied in 11 pulmonary TB patients (PTB) and 26 healthy individuals composed of 14 Tuberculin Skin Test negative (TSTn) and 12 TST positive (TSTp). The production of 6 cytokines was determined (IFNγ, IP10, IL2, TNFα, CCL3, and CCL11). To differentiate PTB from healthy individuals (TSTp + TSTn), the best individual cytokines were IL2 and CCL11 (>80% sensitivity and specificity) and the best combination was IP10 + IL2 (>90% sensitivity and specificity). We describe an innovative approach using full-length antigens attached to biopolyester nanobeads enabling sensitive and specific detection of human TB.

Bioinformatic prospecting and phylogenetic analysis reveals 94 undescribed circular bacteriocins and key motifs.

BACKGROUND: Circular bacteriocins are antimicrobial peptides produced by bacteria with a N and C termini ligation. They have desirable properties such as activity at low concentrations along with thermal, pH and proteolytic resistance. There are twenty experimentally confirmed circular bacteriocins as part of bacteriocin gene clusters, with transport, membrane and immunity proteins. Traditionally, novel antimicrobials are found by testing large numbers of isolates against indicator strains, with no promise of corresponding novel sequence. RESULTS: Through bioprospecting publicly available sequence databases, we identified ninety-nine circular bacteriocins across a variety of bacteria bringing the total to 119. They were grouped into two families within class I modified bacteriocins (i and ii) and further divided into subfamilies based on similarity to experimentally confirmed circular bacteriocins. Within subfamilies, sequences overwhelmingly shared similar characteristics such as sequence length, presence of a polybasic region, conserved locations of aromatic residues, C and N termini, gene clusters similarity, translational coupling and hydrophobicity profiles. At least ninety were predicted to be putatively functional based on gene clusters. Furthermore, bacteriocins identified from Enterococcus, Staphylococcus and Streptococcus species may have activity against clinically relevant strains, due to the presence of putative immunity genes required for expression in a toxin-antitoxin system. Some strains such as Paenibacillus larvae subsp. pulvifaciens SAG 10367 contained multiple circular bacteriocin gene clusters from different subfamilies, while some strains such as Bacillus cereus BCE-01 contained clusters with multiple circular bacteriocin structural genes. CONCLUSIONS: Sequence analysis provided rapid insight into identification of novel, putative circular bacteriocins, as well as conserved genes likely essential for circularisation. This represents an expanded library of putative antimicrobial proteins which are potentially active against human, plant and animal pathogens.

Innovative antigen carrier system for the development of tuberculosis vaccines.

A major obstacle to tuberculosis (TB)-subunit-vaccine development has been the induction of inadequate levels of protective immunity due to the limited breadth of antigen in vaccine preparations. In this study, immunogenic mycobacterial fusion peptides Ag85B-TB10.4 and Ag85B-TB10.4-Rv2660c were covalently displayed on the surface of self-assembled polyester particles. This study investigated whether polyester particles displaying mycobacterial antigens could provide augmented immunogenicity (i.e., offer an innovative vaccine formulation) when compared with free soluble antigens. Herein, polyester particle-based particulate vaccines were produced in an endotoxin-free Escherichia coli strain and emulsified with the adjuvant dimethyl dioctadecyl ammonium bromide. C57BL/6 mice were used to study the immunogenicity of formulated particulate vaccines. The result of humoral immunity showed the antibodies only interacted with target antigens and not with PhaC and the background proteins of the production host. The analysis of T helper 1 cellular immunity indicated that a relatively strong production of cellular immunity biomarkers, IFN-γ and IL-17A cytokines, was induced by particulate vaccines when compared with the respective soluble controls. This study demonstrated that polyester particles have the potential to perform as a mycobacterial antigen-delivery agent to induce augmented antigen-specific immune responses in contrast to free soluble vaccines.-Chen, S., Sandford, S., Kirman, J. R., Rehm, B. H. A. Innovative antigen carrier system for the development of tuberculosis vaccines.

Analysis of the alginate O-acetylation machinery in Pseudomonas aeruginosa.

O-acetylation of alginate produced by the opportunistic human pathogen Pseudomonas aeruginosa significantly contributes to its pathogenesis. Three proteins, AlgI, AlgJ and AlgF have been implicated to form a complex and act together with AlgX for O-acetylation of alginate. AlgI was proposed to transfer the acetyl group across the cytoplasmic membrane, while periplasmic AlgJ was hypothesised to transfer the acetyl group to AlgX that acetylates alginate. To elucidate the proposed O-acetylation multiprotein complex, isogenic knockout mutants of algI, algJ and algF genes were generated in the constitutively alginate overproducing P. aeruginosa PDO300 to enable mutual stability studies. All knockout mutants were O-acetylation negative and complementation with the respective genes in cis or trans restored O-acetylation of alginate. Interestingly, only the AlgF deletion impaired alginate production suggesting a link to the alginate polymerisation/secretion multiprotein complex. Mutual stability experiments indicated that AlgI and AlgF interact independent of AlgJ as well as impact on stability of the alginate polymerisation/secretion multiprotein complex. Deletion of AlgJ did not destabilise AlgX and vice versa. When the alginate polymerase, Alg8, was absent, then AlgI and AlgF stability was strongly impaired supporting a link of the O-acetylation machinery with alginate polymerisation. Pull-down experiments suggested that AlgI interacts with AlgJ, while AlgF interacts with AlgJ and AlgI. Overall, these results suggested that AlgI-AlgJ-AlgF form a multiprotein complex linked via Alg8 to the envelope-spanning alginate polymerisation/secretion multiprotein complex to mediate O-acetylation of nascent alginate. Here, we provide the first insight on how the O-acetylation machinery is associated with alginate production.

Pseudomonas aeruginosa Biofilms.

Pseudomonas 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.

Polyester as Antigen Carrier toward Particulate Vaccines.

Spherical polyhydroxyalkanoate (PHA) inclusions are naturally self-assembled inside bacteria. These PHA beads are shell-core structures composed of a hydrophobic PHA core surrounded by proteins, such as PHA synthase (PhaC). PhaC is covalently attached and serves as an anchor protein for foreign protein vaccine candidate antigens. PHA beads displaying single and multiple antigens showed enhanced immunological properties when compared to respective soluble vaccines. This review highlights the unique design space of the PHA bead-based vaccines toward the development of safe and synthetic particulate vaccines. The PHA bead technology will be compared with chemically synthesized polyesters, such as polylactic acids, formulated to deliver vaccine antigens. The performance of PHA bead vaccine candidates to induce specific immune responses and protective immunity against bacterial and viral pathogens in animal trials will be summarized. We propose that the PHA bead technology offers a versatile vaccine platform for design and cost-effective manufacture of synthetic multivalent vaccines.

A randomized, controlled, phase II clinical trial of ß-D-mannuronic acid (M2000) in pre-surgical breast cancer patients at early stage (T1-T2).

Following the potent efficacy of ß-D-Mannuronic acid in a breast cancer murine model, we evaluated the efficacy of this novel non-steroidal anti-inflammatory drug in breast cancer patients in the present clinical trial. The study was an 8-week randomized, controlled, phase II clinical trial (IRCT: 2017012213739N7 (in 48 pre-surgical breast cancer patients. Patients who had breast cancer at early stage, with invasive ductal carcinoma, were placed on a waiting-list for surgery and were allocated to the study. ß-D-Mannuronic was administrated at a dose of two capsules (1000 mg/d) orally during a period of 8 weeks. The end point of this study was when the patients were admitted for surgery. Moreover, the patients' well-being status was followed up on for safety. There were no statistically significant differences between treatment and non-treatment groups at baseline. ß-D-Mannuronic acid therapy, from 20 patients, showed that in one patient (5%) tumour size was decreased; in five patients (25%) tumour growth was stopped; and in 14 patients (70%) the growth rate in the treatment group did not show significant change, compared to the non-treatment group. Evaluation of two tumour markers (carcinoembryonic antigen and cancer antigen 15-3) showed that there was no significant difference between before and after treatment. Although the use of some non-steroidal anti-inflammatory drugs in a long time period has shown a prophylactic effect in breast cancer, their therapeutic efficacy in a short time period is unknown, whereas treatment with ß-D-Mannuronic acid during 8 weeks could show 30% therapeutic effects in pre-surgical breast cancer patients.

International multicenter randomized, placebo-controlled phase III clinical trial of ß-D-mannuronic acid in rheumatoid arthritis patients.

BACKGROUND: The oral administration of drug ß-D-mannuronic acid (M2000) showed a potent therapeutic effect in phase I/II study in rheumatoid arthritis (RA) patients. Here, our aim is to assess the efficacy and safety of this new drug in RA patients under a multinational, randomized placebo-controlled phase III clinical trial. METHOD: Patients (n = 288) with active disease at baseline and inadequate response to conventional drugs were randomly allocated to three groups; (1) receiving mannuronic acid at a dose of two capsules (500 mg) per day orally for 12 weeks, (2) placebo-controlled, and (3) conventional. The primary endpoints were the America College of Rheumatology 20 response (ACR20), 28-joint disease activity score (DAS28) and Modified Health Assessment Questionnaire-Disability Index (M-HAQ-DI). In addition, the participants were followed-up for safety assessment. RESULTS: In this phase III trial, after 12 weeks of treatment, there was a significant reduction in ACR20 between mannuronic-treated patients compared to placebo and conventional groups. Moreover, there was a similar significant improvement for DAS28 following mannuronic therapy. The statistical analysis showed a significant reduction in the swollen and tender joint count in mannuronic-treated patients compared with the placebo group. On the other side, mannuronic acid showed no-to-very low adverse events in comparison to placebo. CONCLUSION: The results of this multinational, phase III clinical trial provided a potent evidence base for the use of ß-D-mannuronic acid as a new highly safe and efficient drug in the treatment of RA.

Design of Modular Polyhydroxyalkanoate Scaffolds for Protein Immobilization by Directed Ligation.

In vivo-assembled polyhydroxyalkanoate (PHA) particles have been successfully bioengineered to display foreign protein functions toward high-value applications in medicine and industry. To further expand the design space of PHA particles toward immobilization of various functional proteins, we developed a tunable modular protein immobilization method implementing the SpyCatcher/SpyTag chemistry. We successfully displayed the SpyCatcher protein using translational fusion with the Ralstonia eutropha PHA synthase (PhaC). The SpyCatcher domain displayed on the surface of PHA particles was accessible for cross-linker-free ligation with SpyTag-bearing proteins. We demonstrated tunable protein immobilization of various SpyTagged proteins on SpyCatcher-PHA particles, which ultimately enabled assembly of multiple proteins coating the surface of PHA particles. Overall, the functionality, stability, and reusability of proteins immobilized to SpyCatcher-PHA particles were either retained or enhanced in comparison to the soluble forms. This modular platform can be implemented as a generic tool for protein immobilization in an array of applications.

Purification of therapeutic proteins mediated by in vivo polyester immobilized sortase.

OBJECTIVES: To overcome laborious and costly procedures often associated with therapeutic protein production and purification, in vivo polyester immobilized sortase is explored for the production of human tumor necrosis factor alpha (TNFα) and human interferon alpha 2b (IFNα2b) by Escherichia coli. RESULTS: Hybrid genes encoding PhaC-Sortase-TNFα or PhaC-Sortase-IFNα2b fusions (with a LPETG recognition signal immediately before TNFα or IFNα2b), mediated intracellular production of polyester (polyhydroxyalkanoate, PHA) beads in Escherichia coli. Upon isolation of respective PHA beads, pure soluble TNFα or IFNα2b was released by activating sortase via addition of CaCl2 and triglycine. TNFα and IFNα2b each were recognized by corresponding conformational antibodies in an ELISA assay. CONCLUSIONS: In vivo polyester immobilized sortase could be exploited for production and purification of high-value therapeutic proteins without laborious and costly downstream processing.

A phase I/II randomized, controlled, clinical trial for assessment of the efficacy and safety of ß-D-mannuronic acid in rheumatoid arthritis patients.

BACKGROUND: Following the potent efficacy of ß-D-mannuronic acid (M2000) in phase I/II trial in ankylosing spondylitis patients, the present clinical trial was conducted to evaluate the efficacy, safety, and tolerability of this novel drug in rheumatoid arthritis (RA) patients who had inadequate response to conventional therapy. METHOD: The study was a 12-week randomized, controlled, phase I/II clinical trial with two treatment arms: M2000 and conventional treatment. Patients who had RA according to the modified American College of Rheumatology (ACR) criteria, with active disease at baseline also inadequate response to conventional therapy, were enrolled in this study. M2000 was administrated at a dose of two capsules (500 mg) per day orally during a period of 12 weeks. The primary endpoint was the proportion of patients fulfilling the ACR 20% improvement criteria after 12 weeks of M2000 therapy. Moreover, the patients were also followed up for safety. RESULTS: There were no statistically significant differences between treatment and conventional groups at baseline characteristics. The ACR20 response rate was significantly higher among M2000-treated patients than conventional-treated control, so that 74% of patients in treatment group showed an ACR20 response after 12 weeks of M2000 therapy (74 versus 16%; P = 0.011). 10% of M2000-treated patients and 57.1% of conventional-treated patient's adverse events occurred during this study. CONCLUSION: Treatment with M2000 in combination with conventional therapy showed a significantly superior efficacy along with a high safety profile compared to conventional-treated patients. Thereby, M2000 might be suggested as a suitable option in the treatment of RA.

The effects of ß-D-mannuronic acid (M2000), as a novel NSAID, on COX1 and COX2 activities and gene expression in ankylosing spondylitis patients and the murine monocyte/macrophage, J774 cell line.

Ankylosing spondylitis (AS) is a debilitating chronic inflammatory disease with genetic predisposition, which is characterized by the involvement of spine and sacroiliac joints. Due to the relatively unsuccessful treatments, we designed ß-D-mannuronic (M2000) with the beneficial effects in various experimental models as a novel non-steroidal anti-inflammatory drug (NSAID). The aims of our present study were: first, to compare the therapeutic effects of M2000, as a novel designed NSAID, with naproxen and placebo in Iranian patients with AS during 12 weeks; second, to evaluate the effect of M2000 on gene expression of cyclooxygenase enzyme (COX-1/COX-2), a key enzyme in the initiation of inflammatory pathways in AS patients; and third, to assess the activity of COX-1 and COX-2 enzymes in the presence/absence of M2000 at the different doses in the murine macrophage, J774 cell line. This was a sub-study of phase II, randomized, placebo-controlled trial with three treatment arms: M2000, naproxen, and placebo. The outcome measures were the mean changes from baseline to week 12. The gene expression was assessed by real-time PCR. The COX-1 and COX-2 activities were evaluated by ELISA in J774 cell line induced by LPS and arachidonic acid (AA). Our findings demonstrated that M2000 had beneficial therapeutic effects on pain, stiffness, and inflammation, whereas no adverse effects were observed following the use of M2000 after 12 weeks. The analysis of gene expression showed that M2000 could effectively reduce the expression levels of COX-1 and COX-2 in comparison with untreated patients. In addition, the enzymatic activities in the presence of M2000 were significantly less than LPS- and AA-treated groups. Our results indicate that M2000, as a novel designed NSAID with immunosuppressive properties, can be considered as one of the therapeutic options for the treatment of inflammatory diseases without adverse events. Clinical trial identifier IRCT2013062213739N1/ http://www.IRCT.ir .

Activation Mechanism and Cellular Localization of Membrane-Anchored Alginate Polymerase in Pseudomonas aeruginosa.

The exopolysaccharide alginate, produced by the opportunistic human pathogen Pseudomonas aeruginosa, confers a survival advantage to the bacterium by contributing to the formation of characteristic biofilms during infection. Membrane-anchored proteins Alg8 (catalytic subunit) and Alg44 (copolymerase) constitute the alginate polymerase that is being activated by the second messenger molecule bis-(3', 5')-cyclic dimeric GMP (c-di-GMP), but the mechanism of activation remains elusive. To shed light on the c-di-GMP-mediated activation of alginate polymerization in vivo, an in silico structural model of Alg8 fused to the c-di-GMP binding PilZ domain informed by the structure of cellulose synthase, BcsA, was developed. This structural model was probed by site-specific mutagenesis and different cellular levels of c-di-GMP. Results suggested that c-di-GMP-mediated activation of alginate polymerization involves amino acids residing at two loops, including H323 (loop A) and T457 and E460 (loop B), surrounding the catalytic site in the predicted model. The activities of the respective Alg8 variants suggested that c-di-GMP-mediated control of substrate access to the catalytic site of Alg8 is dissimilar to the known activation mechanism of BcsA. Alg8 variants responded differently to various c-di-GMP levels, while MucR imparted c-di-GMP for activation of alginate polymerase. Furthermore, we showed that Alg44 copolymerase constituted a stable dimer, with its periplasmic domains required for protein localization and alginate polymerization and modification. Superfolder green fluorescent protein (GFP) fusions of Alg8 and Alg44 showed a nonuniform, punctate, and patchy arrangement of both proteins surrounding the cell. Overall, this study provides insights into the c-di-GMP-mediated activation of alginate polymerization while assigning functional roles to Alg8 and Alg44, including their subcellular localization and distribution.IMPORTANCE The exopolysaccharide alginate is an important biofilm component of the opportunistic human pathogen P. aeruginosa and the principal cause of the mucoid phenotype that is the hallmark of chronic infections of cystic fibrosis patients. The production of alginate is mediated by interacting membrane proteins Alg8 and Alg44, while their activity is posttranslationally regulated by the second messenger c-di-GMP, a well-known regulator of the synthesis of a range of other exopolysaccharides in bacteria. This study provides new insights into the unknown activation mechanism of alginate polymerization by c-di-GMP. Experimental evidence that the activation of alginate polymerization requires the engagement of specific amino acid residues residing at the catalytic domain of Alg8 glycosyltransferase was obtained, and these residues are proposed to exert an allosteric effect on the PilZAlg44 domain upon c-di-GMP binding. This mechanism is dissimilar to the proposed mechanism of the autoinhibition of cellulose polymerization imposed by salt bridge formation between amino acid residues and released upon c-di-GMP binding, leading to activation of polymerization. On the other hand, conserved amino acid residues in the periplasmic domain of Alg44 were found to be involved in alginate polymerization as well as modification events, i.e., acetylation and epimerization. Due to the critical role of c-di-GMP in the regulation of many biological processes, particularly the motility-sessility switch and also the emergence of persisting mucoid phenotypes, these results aid to reach a better understanding of biofilm-associated regulatory networks and c-di-GMP signaling and might assist the development of inhibitory drugs.

Engineering Mycobacteria for the Production of Self-Assembling Biopolyesters Displaying Mycobacterial Antigens for Use as a Tuberculosis Vaccine.

Tuberculosis (TB) is a disease caused by Mycobacterium tuberculosis or Mycobacterium bovis and still remains one of the world's biggest global health burdens. Recently, engineered polyhydroxyalkanoate (PHA) biobeads that were produced in both Escherichia coli and Lactococcus lactis and displayed mycobacterial antigens were found to induce significant cell-mediated immune responses in mice. We observed that such PHA beads contained host cell proteins as impurities, which we hypothesized to have the potential to induce immunity. In this study, we aimed to develop PHA beads produced in mycobacteria (mycobacterial PHA biobeads [MBB]) and test their potential as a TB vaccine in a mouse model. As a model organism, nonpathogenic Mycobacterium smegmatis was engineered to produce MBB or MBB with immobilized mycobacterial antigens Ag85A and ESAT-6 on their surface (A:E-MBB). Three key enzymes involved in the poly(3-hydroxybutyric acid) pathway, namely, ß-ketothiolase (PhaA), acetoacetyl-coenzyme A reductase (PhaB), and PHA synthase (PhaC), were engineered into E. coli-Mycobacterium shuttle plasmids and expressed in trans Immobilization of specific antigens to the surface of the MBB was achieved by creating a fusion with the PHA synthase which remains covalently attached to the polyester core, resulting in PHA biobeads displaying covalently immobilized antigens. MBB, A: E-MBB, and an M. smegmatis vector control (MVC) were used in a mouse immunology trial, with comparison to phosphate-buffered saline (PBS)-vaccinated and Mycobacterium bovis BCG-vaccinated groups. We successfully produced MBB and A:E-MBB and used them as vaccines to induce a cellular immune response to mycobacterial antigens.IMPORTANCE Tuberculosis (TB) is a disease caused by Mycobacterium tuberculosis or Mycobacterium bovis and still remains one of the world's biggest global health burdens. In this study, we produced polyhydroxyalkanoate (PHA) biobeads in mycobacteria and used them as vaccines to induce a cellular immune response to mycobacterial antigens.

Purification of target proteins from intracellular inclusions mediated by intein cleavable polyhydroxyalkanoate synthase fusions.

BACKGROUND: Recombinant protein production and purification from Escherichia coli is often accompanied with expensive and complicated procedures, especially for therapeutic proteins. Here it was demonstrated that, by using an intein cleavable polyhydroxyalkanoate synthase fusion, recombinant proteins can be first produced and sequestered on a natural resin, the polyhydroxyalkanoate (PHA) inclusions, then separated from contaminating host proteins via simple PHA bead isolation steps, and finally purified by specific release into the soluble fraction induced by a pH reduction. RESULTS: By translationally fusing a target protein to PHA synthase using a self-cleaving intein as linker, intracellular production of PHA beads was achieved. Upon isolation of respective PHA beads the soluble pure target protein was released by a simple pH shift to 6. The utility of this approach was exemplified by producing six target proteins, including Aequorea victoria green fluorescent protein (GFP), Mycobacterium tuberculosis vaccine candidate Rv1626, the immunoglobulin G (IgG) binding ZZ domain of protein A derived from Staphylococcus aureus, human tumor necrosis factor alpha (TNFα), human granulocyte colony-stimulating factor (G-CSF), and human interferon alpha 2b (IFNα2b). CONCLUSIONS: Here a new method for production and purification of a tag-less protein was developed through intein cleavable polyhydroxyalkanoate synthase fusion. Pure target protein could be easily obtained without laborious downstream processing.

Engineering Bacillus megaterium for production of functional intracellular materials.

BACKGROUND: Over the last 10-15 years, a technology has been developed to engineer bacterial poly(3-hydroxybutyrate) (PHB) inclusions as functionalized beads, for applications such as vaccines, diagnostics and enzyme immobilization. This has been achieved by translational fusion of foreign proteins to the PHB synthase (PhaC). The respective fusion protein mediates self-assembly of PHB inclusions displaying the desired protein function. So far, beads have mainly been produced in recombinant Escherichia coli, which is problematic for some applications as the lipopolysaccharides (LPS) co-purified with such inclusions are toxic to humans and animals. RESULTS: In this study, we have bioengineered the formation of functional PHB inclusions in the Gram-positive bacterium Bacillus megaterium, an LPS-free and established industrial production host. As B. megaterium is a natural PHB producer, the PHB-negative strain PHA05 was used to avoid any background PHB production. Plasmid-mediated T7 promoter-driven expression of the genes encoding ß-ketothiolase (phaA), acetoacetyl-CoA-reductase (phaB) and PHB synthase (phaC) enabled PHB production in B. megaterium PHA05. To produce functionalized PHB inclusions, the N- and C-terminus of PhaC was fused to four and two IgG binding Z-domains from Staphylococcus aureus, respectively. The ZZ-domain PhaC fusion protein was strongly overproduced at the surface of the PHB inclusions and the corresponding isolated ZZ-domain displaying PHB beads were found to purify IgG with a binding capacity of 40-50 mg IgG/g beads. As B. megaterium has the ability to sporulate and respective endospores could co-purify with cellular inclusions, a sporulation negative production strain was generated by disrupting the spoIIE gene in PHA05. This strain did not produce spores when tested under sporulation inducing conditions and it was still able to synthesize ZZ-domain displaying PHB beads. CONCLUSIONS: This study provides proof of concept for the successful genetic engineering of B. megaterium as a host for the production of functionalized PHB beads. Disruption of the spoIIE gene rendered B. megaterium incapable of sporulation but particularly suitable for production of functionalized PHB beads. This sporulation-negative mutant represents an improved industrial production strain for biotechnological processes otherwise impaired by the possibility of endospore formation.

Assessing the Performance of Floating Biofilters for Oxidation of Methane from Dairy Effluent Ponds.

Mitigating methane (CH) emissions from New Zealand dairy effluent ponds using volcanic pumice soil biofilters has been found to be a promising technology. Because the soil column biofilter prototype previously used was cumbersome, here we assess the effectiveness of volcanic pumice soil-perlite biofilter media in a floating system to remove high concentrations of CH emitted from a dairy effluent pond and simultaneously in a laboratory setting. We measured the CH removal over a period of 11 mo and determined methanotroph population dynamics using molecular techniques to understand the role of methanotroph population abundance and diversity in CH removal. Irrespective of the season, the pond-floating biofilters removed 66.7 ± 5.7% CH throughout the study period and removed up to 101.5 g CH m h. By contrast, the laboratory-based floating biofilters experienced more biological disturbances, with both low (∼34%) and high (∼99%) CH removal phases during the study period and an average of 58% of the CH oxidized. These disturbances could be attributed to the measured lower abundance of type II methanotroph population compared with the pond biofilters. Despite the acidity of the pond biofilters increasing significantly by the end of the study period, the biofilter encouraged the growth of both type I ( and ) and type II ( and ) methanotrophs. This study demonstrated the potential of the floating biofilters to mitigate dairy effluent ponds emissions efficiently and indicated methanotroph abundance as a key factor controlling CH oxidation in the biofilter.

Immunogencity of antigens from Mycobacterium tuberculosis self-assembled as particulate vaccines.

Traditional approaches to vaccine development have failed to identify better vaccines to replace or supplement BCG for the control of tuberculosis (TB). Subunit vaccines offer a safer and more reproducible alternative for the prevention of diseases. In this study, the immunogenicity of bacterially derived polyester beads displaying three different Rv antigens of Mycobacterium tuberculosis was evaluated. Polyester beads displaying the antigens Rv1626, Rv2032, Rv1789, respectively, were produced in an endotoxin-free Escherichia coli strain. Beads were formulated with the adjuvant DDA and subcutaneously administered to C57BL/6 mice. Cytokine responses were evaluated by CBA and antibody responses by ELISA. Specificity of the IgG response was assessed by immunoblotting cell lysates of the vaccine production strains using sera from the vaccinated mice. Mice vaccinated with beads displaying Rv1626 had significantly greater IgG1 responses compared to mice vaccinated with Rv1789 beads and greater IgG2 responses than the group vaccinated with Rv2032 beads (p<0.05). Immunoblotting of antisera from these mice indicated the antibody responses were Rv1626 antigen-specific and there was no detectable immune response to the polyester component of the vaccine. Overall, this study suggested that selected TB antigens derived from reverse vaccinology approaches can be displayed on polyester beads to produce antigen-specific immune responses potentially relevant to the prevention of TB.