Publications by authors named "Robert J Capon"

152 Publications

Poly(hydrophobic amino acid) Conjugates for the Delivery of Multiepitope Vaccine against Group A Streptococcus.

Bioconjug Chem 2021 Aug 11. Epub 2021 Aug 11.

School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, Queensland 4072, Australia.

Peptide-based vaccines are composed of small, defined, antigenic peptide epitopes. They are designed to induce well-controlled immune responses. Multiple epitopes are often employed in these vaccines to cover strain variability of a pathogen. However, peptide epitopes cannot stimulate adequate immune responses on their own and require an adjuvant (immune stimulant) and/or delivery system. Here, we designed and synthesized a multiepitope vaccine candidate against Group A Streptococcus (GAS) composed of several B-cell epitopes (J8, PL1, and 88/30) derived from GAS M-protein, universal PADRE T-helper cell epitope, and a polyleucine self-adjuvanting unit. The vaccine components were conjugated together (using mercapto-maleimide and azide-alkyne Huisgen cycloaddition reactions) or delivered as a mixture. The conjugated multiepitope vaccine candidate self-assembled into small nanoparticles and chain-like aggregated nanoparticles (CLANs) that were able to induce the production of J8-, PL1-, and 88/30-specific antibodies in mice. The multiepitope conjugate and the physical mixture of conjugates bearing the individual epitopes produced similar nanoparticles and induced comparable immune responses. Hence, simple physical mixing can replace complex chemical conjugation to produce multiepitope nanoparticles with equivalent morphology and immunological efficacy. This greatly simplifies vaccine production.
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http://dx.doi.org/10.1021/acs.bioconjchem.1c00333DOI Listing
August 2021

Chemical cues that attract cannibalistic cane toad (Rhinella marina) larvae to vulnerable embryos.

Sci Rep 2021 Jun 15;11(1):12527. Epub 2021 Jun 15.

School of Life and Environmental Sciences A08, University of Sydney, Sydney, NSW, 2006, Australia.

Chemical cues produced by late-stage embryos of the cane toad (Rhinella marina) attract older conspecific larvae, which are highly cannibalistic and can consume an entire clutch. To clarify the molecular basis of this attraction response, we presented captive tadpoles with components present in toad eggs. As previously reported, attractivity arises from the distinctive toxins (bufadienolides) produced by cane toads, with some toxins (e.g., bufagenins) much stronger attractants than others (e.g., bufotoxins). Extracts of frozen toad parotoid glands (rich in bufagenins) were more attractive than were fresh MeOH extracts of the parotoid secretion (rich in bufotoxins), and purified marinobufagin was more effective than marinobufotoxin. Cardenolide aglycones (e.g., digitoxigenin) were active attractors, whereas C-3 glycosides (e.g., digoxin, oubain) were far less effective. A structure-activity relationship study revealed that tadpole attractant potency strongly correlated with Na/K ATPase inhibitory activity, suggesting that tadpoles monitor and rapidly react to perturbations to Na/K ATPase activity.
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http://dx.doi.org/10.1038/s41598-021-90233-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8206116PMC
June 2021

Cell-Penetrating Peptides-Based Liposomal Delivery System Enhanced Immunogenicity of Peptide-Based Vaccine against Group A Streptococcus.

Vaccines (Basel) 2021 May 12;9(5). Epub 2021 May 12.

School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, QLD 4072, Australia.

Peptide-based vaccine development represents a highly promising strategy for preventing Group A Streptococcus (GAS) infection. However, these vaccines need to be administered with the help of a delivery system and/or immune adjuvant. Cell-penetrating peptides (CPPs) have been used as a powerful tool for delivering various therapeutic agents, including peptides, as they can overcome the permeability barrier of cell membranes. Here, we used CPPs to deliver our lead lipopeptide-based vaccine (LCP-1). CPPs were anchored through a spacer to LCP-1-bearing multilamellar and unilamellar liposomes and administered to Swiss outbred mice. Tat conjugated to two palmitic acids via a (Gly) spacer (to form a liposome-anchoring moiety) was the most efficient system for triggering immune responses when combined with multilamellar liposomes bearing LCP-1. The immunostimulatory potential of a variety of other CPPs was examined following intranasal administration in mice. Among them, LCP-1/liposomes/Tat and LCP-1/liposomes/KALA induced the highest antibody titers. The antibodies produced showed high opsonic activity against clinically isolated GAS strains D3840 and GC2 203. The use of the CPP-liposome delivery system is a promising strategy for liposome-based GAS vaccine development.
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http://dx.doi.org/10.3390/vaccines9050499DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8151947PMC
May 2021

-Amino-l-Proline Methyl Ester from an Australian Fish Gut-Derived Fungus: Challenging the Distinction between Natural Product and Artifact.

Mar Drugs 2021 Mar 12;19(3). Epub 2021 Mar 12.

Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD 4072, Australia.

Further investigation into a fish gut-derived fungus sp. CMB-F563, previously reported to produce the unprecedented Schiff base prolinimines A-B (-), revealed a new cryptic natural product, -amino-l-proline methyl ester ()-only the second reported natural occurrence of an -amino-proline, and the first from a microbial source. To enable these investigations, we developed a highly sensitive analytical derivitization methodology, using 2,4-dinitrobenzaldehyde (2,4-DNB) to cause a rapid in situ transformation of to the Schiff base , with the latter more readily detectable by UHPLC-DAD (400 nm) and HPLC-MS analyses. Moreover, we demonstrate that during cultivation is retained in fungal mycelia, and it is only when solvent extraction disrupts mycelia that is released to come in contact with the furans - (which are themselves produced by thermal transformation of carbohydrates during media autoclaving prior to fungal inoculation). Significantly, on contact, undergoes a spontaneous condensation with - to yield the Schiff base prolinimines -, respectively. Observations made during this study prompted us to reflect on what it is to be a natural product (i.e., ), versus an artifact (i.e., -), versus a media component (i.e., -).
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http://dx.doi.org/10.3390/md19030151DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7999761PMC
March 2021

Polyethylenimine quantity and molecular weight influence its adjuvanting properties in liposomal peptide vaccines.

Bioorg Med Chem Lett 2021 05 9;40:127920. Epub 2021 Mar 9.

School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, QLD 4072, Australia. Electronic address:

We recently reported that polyethylenimine (PEI; molecular weight of 600 Da) acted as a vaccine adjuvant for liposomal group A Streptococcus (GAS) vaccines, eliciting immune responses in vivo with IgG antibodies giving opsonic activity against five Australian GAS clinical isolates. However, to date, no investigation comparing the structure-activity relationship between the molecular weight of PEI and its adjuvanting activity in vaccine development has been performed. We hypothesized that the molecular weight and quantity of PEI in a liposomal vaccine will impact its adjuvanting properties. In this study, we successfully formulated liposomes containing different molecular weights of PEI (600, 1800, 10k and 25k Da) and equivalents of PEI (0.5, 1 and 2) of branched PEI. Outbred mice were administrated the vaccine formulations intranasally, and the mice that received a high ratio of PEI 600 reported a stronger immune response than the mice that received a lower ratio of PEI 600. Interestingly, mice that received the same quantity of PEI 600, PEI 10k and PEI 25k showed similar immune responses in vivo and in vitro. This comparative study highlights the ratio of PEI present in the liposome vaccines impacts adjuvanting activity, however, PEI molecular weight did not significantly enhance its adjuvanting properties. We also report that the stability of PEI liposomes is critical for vaccines to elicit the desired immune response.
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http://dx.doi.org/10.1016/j.bmcl.2021.127920DOI Listing
May 2021

New from Old: Thorectandrin Alkaloids in a Southern Australian Marine Sponge, (CMB-01889).

Mar Drugs 2021 Feb 9;19(2). Epub 2021 Feb 9.

Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD 4072, Australia.

(CMB-01889) was prioritized as a source of promising new chemistry from a library of 960 southern Australian marine sponge extracts, using a global natural products social (GNPS) molecular networking approach. The sponge was collected at a depth of 45 m. Chemical fractionation followed by detailed spectroscopic analysis led to the discovery of a new tryptophan-derived alkaloid, thorectandrin A (), with the GNPS cluster revealing a halo of related alkaloids -. In considering biosynthetic origins, we propose that (CMB-01889) produces four well-known alkaloids, 6-bromo-1',8-dihydroaplysinopsin (), 6-bromoaplysinopsin (), aplysinopsin (), and 1',8-dihydroaplysinopsin (), all of which are susceptible to processing by a putative indoleamine 2,3-dioxygenase- (IDO) enzyme to -. Where the 1',8-dihydroalkaloids and are fully transformed to stable ring-opened thorectandrins and -, and -, respectively, the conjugated precursors and are transformed to highly reactive Michael acceptors that during extraction and handling undergo complete transformation to artifacts -, and -, respectively. Knowledge of the susceptibility of aplysinopsins as substrates for IDOs, and the relative reactivity of Michael acceptor transformation products, informs our understanding of the pharmaceutical potential of this vintage marine pharmacophore. For example, the cancer tissue specificity of IDOs could be exploited for an immunotherapeutic response, with aplysinopsins transforming in situ to Michael acceptor thorectandrins, which covalently bind and inhibit the enzyme.
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http://dx.doi.org/10.3390/md19020097DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7914882PMC
February 2021

Neobulgarones Revisited: and Bianthrones from an Australian Mud Dauber Wasp Nest-Associated Fungus, sp. CMB-MD22.

J Nat Prod 2021 03 3;84(3):762-770. Epub 2021 Feb 3.

Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia.

We report on the chemical analysis of a mud dauber wasp nest-associated fungus, sp. CMB-MD22, leading to the discovery and structure elucidation of three known (-) and two new ( and ) anthrones, and a family of new and known bianthrones, neobulgarones -. Detection and structure elucidation of - was supported by detailed spectroscopic analysis, as well as chemical (thermal) transformations, and global natural products social (GNPS) molecular networking. An empirical approach using HPLC retention times was effective at differentiating from bianthrone isomers, while a facile thermal equilibration was shown to favor over isomers. The neobulgarones - are natural products, and a crude extract rich in - exhibits selective antifungal activity against a co-isolated mud dauber wasp nest-associated fungus, suggestive of a possible ecological role as an antifungal chemical defense.
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http://dx.doi.org/10.1021/acs.jnatprod.0c01035DOI Listing
March 2021

Immunogenicity Assessment of Cell Wall Carbohydrates of Group A via Self-Adjuvanted Glyco-lipopeptides.

ACS Infect Dis 2021 02 3;7(2):390-405. Epub 2021 Feb 3.

School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, QLD 4072, Australia.

Identifying the immunogenic moieties and their precise structure of carbohydrates plays an important role for developing effective carbohydrate-based subunit vaccines. This study assessed the structure-immunogenicity relationship of carbohydrate moieties of a single repeating unit of group A carbohydrate (GAC) present on the cell wall of group A (GAS) using a rationally designed self-adjuvanted lipid-core peptide, instead of a carrier protein. Immunological evaluation of fully synthetic glyco-lipopeptides (particle size: 300-500 nm) revealed that construct consisting of higher rhamnose moieties (trirhamnosyl-lipopeptide) was able to induce enhanced immunogenic activity in mice, and GlcNAc moiety was not found to be an essential component of immunogenic GAC mimicked epitope. Trirhamnosyl-lipopeptide also showed 75-97% opsonic activity against four different clinical isolates of GAS and was comparable to a subunit peptide vaccine (J8-lipopeptide) which illustrated 65-96% opsonic activity.
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http://dx.doi.org/10.1021/acsinfecdis.0c00722DOI Listing
February 2021

Poly(hydrophobic amino acid)-Based Self-Adjuvanting Nanoparticles for Group A Vaccine Delivery.

J Med Chem 2021 03 2;64(5):2648-2658. Epub 2021 Feb 2.

School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, QLD 4072, Australia.

Peptide antigens have been widely used in the development of vaccines, especially for those against autoimmunity-inducing pathogens and cancers. However, peptide-based vaccines require adjuvant and/or a delivery system to stimulate desired immune responses. Here, we explored the potential of self-adjuvanting poly(hydrophobic amino acids) (pHAAs) to deliver peptide-based vaccine against Group A (GAS). We designed and synthesized self-assembled nanoparticles with a variety of conjugates bearing a peptide antigen (J8-PADRE) and polymerized hydrophobic amino acids to evaluate the effects of structural arrangement and pHAAs properties on a system's ability to induce humoral immune responses. Immunogenicity of the developed conjugates was also compared to commercially available human adjuvants. We found that a linear conjugate bearing J8-PADRE and 15 copies of leucine induced equally effective, or greater, immune responses than commercial adjuvants. Our fully defined, adjuvant-free, single molecule-based vaccine induced the production of antibodies capable of killing GAS bacteria.
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http://dx.doi.org/10.1021/acs.jmedchem.0c01660DOI Listing
March 2021

Amaurones A-K: Polyketides from the Fish Gut-Derived Fungus sp. CMB-F713.

J Nat Prod 2021 02 2;84(2):474-482. Epub 2021 Feb 2.

Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia.

Using a molecular networking guided strategy, chemical analysis of the Australian mullet fish gastrointestinal tract-derived fungus sp. CMB-F713 yielded a family of polyketide pyrones, amaurones A-I (-), featuring an unprecedented carbon skeleton. Structures were assigned to - by detailed spectroscopic analysis (including X-ray analysis of ), biosynthetic considerations, and chemical interconversions. For example, the orthoacetate was unstable when stored dry at room temperature, transforming to the monoacetates and , while mild heating (40 °C) prompted quantitative conversion of to , via an intramolecular -acetylation. Likewise, during handling, the monoacetate was prone to intramolecular -acetylation, leading to an equilibrium mixture with the isomeric monoacetate amaurone J (), confirmed when partial hydrolysis of the diacetate yielded the monoacetates and and the triol amaurone K ().
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http://dx.doi.org/10.1021/acs.jnatprod.0c01343DOI Listing
February 2021

Lincolnenins A-D: Isomeric Bactericidal Bianthracenes from .

J Org Chem 2021 Aug 15;86(16):11011-11018. Epub 2020 Dec 15.

Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD 4072, Australia.

Cultivation profiling followed by chemical analysis of yielded four new isomeric bianthracenes, lincolnenins A-D (-), with relative stereostructures assigned on the basis of detailed spectroscopic analysis. Lincolnenins A () and B () exhibit restricted rotation about alternate bianthracene 9-9' and 9-8' bridges, respectively, and exist as single atropisomers, whereas C () and D () are thermally interconvertible atropisomers sharing a common 8-8' bianthracene bridge. Absolute configurations were assigned to - on the basis of diagnostic ROESY correlations and ECD calculations, whereas acid-mediated dehydration of led to formation and revision of the absolute configuration of the biosynthetically related known antibiotic, setomimycin (). Lincolnenin A () exhibited significant bactericidal activity against multiple susceptible and drug-resistant Gram-positive pathogens (MIC < 2.0 μM), including H37Ra (MIC = 0.9 μM).
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http://dx.doi.org/10.1021/acs.joc.0c02492DOI Listing
August 2021

A dual-adjuvanting strategy for peptide-based subunit vaccines against group A Streptococcus: Lipidation and polyelectrolyte complexes.

Bioorg Med Chem 2020 12 20;28(24):115823. Epub 2020 Oct 20.

School of Chemistry & Molecular Biosciences, The University of Queensland, St Lucia, QLD 4072, Australia; Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD 4072, Australia; School of Pharmacy, The University of Queensland, Woolloongabba, QLD 4102, Australia. Electronic address:

In order to improve the immunogenicity of peptide-based vaccines against group A Streptococcus (GAS), lipid moieties (C16 lipoamino acid and cholic acid) were conjugated with peptide antigen (P25-J8) and further modified with α-poly(glutamic acid) (α-PGA). Thus, positively charged lipopeptide vaccine candidates LCP-1 (P25-K(J8)-SS-C16-C16) and LCP-2 (P25-K(J8)-SS-K(cholic acid)) were synthesized. Negatively charged LCP-3 (P25-K(PGA-J8)-SS-K(cholic acid)) was also produced by attaching α-PGA to the J8 N-terminus of LCP-2. Polyelectrolyte complex (PEC) nanoparticles were formulated with heparin and/or trimethyl chitosan (TMC) for delivery of the lipopeptide vaccine candidates. The ability of the antigen-loaded nanoparticles to induce humoral immune responses was examined in outbred female Swiss mice following intranasal immunization. The antibodies produced were opsonic against all clinical GAS isolates tested.
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http://dx.doi.org/10.1016/j.bmc.2020.115823DOI Listing
December 2020

Polyethylenimine: An Intranasal Adjuvant for Liposomal Peptide-Based Subunit Vaccine against Group A .

ACS Infect Dis 2020 09 26;6(9):2502-2512. Epub 2020 Aug 26.

School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, Queensland 4072, Australia.

Group A (GAS) and GAS-related infections are a worldwide challenge, with no commercial GAS vaccine available. Polyethylenimine (PEI) attaches to the cells' surface and delivers cargo into endosomal and cytosolic compartments. We hypothesized that this will confer mucosal adjuvant properties for peptide antigens against group A (GAS). In this study, we successfully demonstrated the development of PEI incorporated liposomes for the delivery of a lipopeptide-based vaccine (LCP-1) against GAS. Outbred mice were administrated with the vaccine formulations intranasally, and immunological investigation showed that the PEI liposomes elicited significant mucosal and systemic immunity with the production of IgA and IgG antibodies. Antibodies were shown to effectively opsonize multiple isolates of clinically isolated GAS. This proof-of-concept study showed the capability for PEI liposomes to act as a safe vehicle for the delivery of GAS peptide antigens to elicit immune responses against GAS infection, making PEI a promising addition to liposomal mucosal vaccines.
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http://dx.doi.org/10.1021/acsinfecdis.0c00452DOI Listing
September 2020

Levoglucosenone and Its Pseudoenantiomer -Levoglucosenone as Scaffolds for Drug Discovery and Development.

ACS Omega 2020 Jun 8;5(23):13926-13939. Epub 2020 Jun 8.

Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD 4072, Australia.

The bioderived platform molecule levoglucosenone (LGO, ) and its readily prepared pseudoenantiomer (-LGO, ) have each been subjected to α-iodination reactions with the product halides then being engaged in palladium-catalyzed Ullmann cross-coupling reactions with various bromonitropyridines. The corresponding α-pyridinylated derivatives such as and , respectively, are produced as a result. Biological screening of such products reveals that certain of them display potent and selective antimicrobial and/or cytotoxic properties. In contrast, the azaindoles obtained by reductive cyclization of compounds such as and are essentially inactive in these respects. Preliminary mode-of-action studies are reported.
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http://dx.doi.org/10.1021/acsomega.0c01331DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7301580PMC
June 2020

Exploring Natural Product Artifacts: The Polyketide Enterocin Warms to a Ballet of Isomers.

Org Lett 2020 06 8;22(12):4828-4832. Epub 2020 Jun 8.

Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland 4072, Australia.

The polyketide enterocin is responsive to environmental stimuli, where mild heating promotes an equilibrium mixture of the isomeric acetals enterocins B and C, which subsequently undergo pseudo-chair-boat inversion to enterocin D. When exposed to aqueous base, enterocin is converted to the isomeric Michael acceptor enterocin F. These studies demonstrate that knowledge of environmental stimuli and associated artifacts is critical to understanding the chemical and ecological properties of enterocins and other classes of natural products.
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http://dx.doi.org/10.1021/acs.orglett.0c01629DOI Listing
June 2020

Opsonic Activity of Conservative Versus Variable Regions of the Group A M Protein.

Vaccines (Basel) 2020 May 7;8(2). Epub 2020 May 7.

School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, QLD 4072, Australia.

Group A (GAS) and GAS-associated infections are a global challenge, with no licensed GAS vaccine on the market. The GAS M protein is a critical virulence factor in the fight against GAS infection, and it has been a primary target for GAS vaccine development. Measuring functional opsonic antibodies against GAS is an important component in the clinical development path for effective vaccines. In this study, we compared the opsonic activity of two synthetic, self-adjuvanting subunit vaccines containing either the J8- or 88/30-epitope in Swiss outbred mice using intranasal administration. Following primary immunization and three boosts, sera were assessed for IgG activity using ELISA, and opsonization activity against seven randomly selected clinical isolates of GAS was measured. Vaccine constructs containing the conservative J8-epitope showed significant opsonic activity against six out of the seven GAS clinical isolates, while the vaccine containing the variable 88/30-epitope did not show any significant opsonic activity.
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http://dx.doi.org/10.3390/vaccines8020210DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7349123PMC
May 2020

Development of Polyelectrolyte Complexes for the Delivery of Peptide-Based Subunit Vaccines against Group A .

Nanomaterials (Basel) 2020 Apr 26;10(5). Epub 2020 Apr 26.

School of Chemistry & Molecular Biosciences, The University of Queensland, St. Lucia, QLD 4072, Australia.

Peptide subunit vaccines hold great potential compared to traditional vaccines. However, peptides alone are poorly immunogenic. Therefore, it is of great importance that a vaccine delivery platform and/or adjuvant that enhances the immunogenicity of peptide antigens is developed. Here, we report the development of two different systems for the delivery of lipopeptide subunit vaccine (LCP-1) against group A streptococcus: polymer-coated liposomes and polyelectrolyte complexes (PECs). First, LCP-1-loaded and alginate/trimethyl chitosan (TMC)-coated liposomes (Lip-1) and LCP-1/alginate/TMC PECs (PEC-1) were examined for their ability to trigger required immune responses in outbred Swiss mice; PEC-1 induced stronger humoral immune responses than Lip-1. To further assess the adjuvanting effect of anionic polymers in PECs, a series of PECs (PEC-1 to PEC-5) were prepared by mixing LCP-1 with different anionic polymers, namely alginate, chondroitin sulfate, dextran, hyaluronic acid, and heparin, then coated with TMC. All produced PECs had similar particle sizes (around 200 nm) and surface charges (around + 30 mV). Notably, PEC-5, which contained heparin, induced higher antigen-specific systemic IgG and mucosal IgA titers than all other PECs. PEC systems, especially when containing heparin and TMC, could function as a promising platform for peptide-based subunit vaccine delivery for intranasal administration.
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http://dx.doi.org/10.3390/nano10050823DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7712447PMC
April 2020

Genomic and Metabolomic Analysis of Antarctic Bacteria Revealed Culture and Elicitation Conditions for the Production of Antimicrobial Compounds.

Biomolecules 2020 04 27;10(5). Epub 2020 Apr 27.

Laboratory of Molecular Applied Biology, Center of Excellence in Translational Medicine, Universidad de La Frontera, Avenida Alemania 0458, Temuco 4810296, Chile.

Concern about finding new antibiotics against drug-resistant pathogens is increasing every year. Antarctic bacteria have been proposed as an unexplored source of bioactive metabolites; however, most biosynthetic gene clusters (BGCs) producing secondary metabolites remain silent under common culture conditions. Our work aimed to characterize elicitation conditions for the production of antibacterial secondary metabolites from 34 Antarctic bacterial strains based on MS/MS metabolomics and genome mining approaches. Bacterial strains were cultivated under different nutrient and elicitation conditions, including the addition of lipopolysaccharide (LPS), sodium nitroprusside (SNP), and coculture. Metabolomes were obtained by HPLC-QTOF-MS/MS and analyzed through molecular networking. Antibacterial activity was determined, and seven strains were selected for genome sequencing and analysis. Biosynthesis pathways were activated by all the elicitation treatments, which varies among strains and dependents of culture media. Increased antibacterial activity was observed for a few strains and addition of LPS was related with inhibition of Gram-negative pathogens. Antibiotic BGCs were found for all selected strains and the expressions of putative actinomycin, carotenoids, and bacillibactin were characterized by comparison of genomic and metabolomic data. This work established the use of promising new elicitors for bioprospection of Antarctic bacteria and highlights the importance of new "-omics" comparative approaches for drug discovery.
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http://dx.doi.org/10.3390/biom10050673DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7277857PMC
April 2020

Structure-Activity Analysis of Cyclic Multicomponent Lipopeptide Self-Adjuvanting Vaccine Candidates Presenting Group A Antigens.

J Med Chem 2020 05 12;63(10):5387-5397. Epub 2020 May 12.

School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane 4072, Australia.

Group A (GAS) infection causes a range of life-threatening diseases, including rheumatic heart disease. Cyclic peptides offer an attractive solution for presentation of short peptide antigens due to their stability and structurally constrained conformation. We investigated a cyclic carrier decapeptide incorporating a B cell GAS peptide epitope, a universal T helper epitope, and a synthetic toll-like receptor 2-targeting moiety as a possible self-adjuvanting GAS vaccine. A structure-activity relationship of the cyclic lipopeptide vaccine showed successful induction of J8-specific systemic immunoglobulin G (IgG) antibodies when administered subcutaneously without an additional adjuvant. Interestingly, the physical mixture control induced the highest titers of all vaccine compounds, with antibodies from mice immunized with this physical mixture control shown to effectively opsonize multiple strains of clinically isolated GAS bacteria. This study showed the capability for a self-adjuvanting cyclic delivery system to act as a vehicle for the delivery of GAS peptide antigens to treat GAS infections.
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http://dx.doi.org/10.1021/acs.jmedchem.0c00203DOI Listing
May 2020

Dysidealactams and Dysidealactones: Sesquiterpene Glycinyl-Lactams, Imides, and Lactones from a sp. Marine Sponge Collected in Southern Australia.

J Nat Prod 2020 05 3;83(5):1577-1584. Epub 2020 Apr 3.

Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD 4072, Australia.

A GNPS molecular networking approach mapped a library of 960 southern Australian marine sponges and prioritized sp. (CMB-01171) for chemical investigation. Although the published natural products literature on Australian sponges extends back over half a century and suffers from the perception of being near exhausted, fractionation of sp. (CMB-01171) led to the discovery of a family of 10 new biosynthetically and chemically related sesquiterpenes. Detailed spectroscopic analysis guided structure elucidation identified dysidealactams A-F (-), dysidealactones A and B ( and ), and two solvolysis artifacts, and . The dysidealactams A-D (-) incorporate a rare glycinyl-lactam functionality, while dysidealactam E () is particularly noteworthy in incorporating an unprecedented glycinyl-imide moiety. In addition to expanding knowledge of natural products, this study demonstrates the value of applying GNPS molecular networking to map chemical diversity and prioritize the selection of marine sponge extracts for more detailed chemical analysis.
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http://dx.doi.org/10.1021/acs.jnatprod.0c00041DOI Listing
May 2020

Poly(amino acids) as a potent self-adjuvanting delivery system for peptide-based nanovaccines.

Sci Adv 2020 01 29;6(5):eaax2285. Epub 2020 Jan 29.

The University of Queensland, School of Chemistry & Molecular Biosciences, Lucia, QLD 4072, Australia.

To be optimally effective, peptide-based vaccines need to be administered with adjuvants. Many currently available adjuvants are toxic, not biodegradable; they invariably invoke adverse reactions, including allergic responses and excessive inflammation. A nontoxic, biodegradable, biocompatible, self-adjuvanting vaccine delivery system is urgently needed. Herein, we report a potent vaccine delivery system fulfilling the above requirements. A peptide antigen was coupled with poly-hydrophobic amino acid sequences serving as self-adjuvanting moieties using solid-phase synthesis, to produce fully defined single molecular entities. Under aqueous conditions, these molecules self-assembled into distinct nanoparticles and chain-like aggregates. Following subcutaneous immunization in mice, these particles successfully induced opsonic epitope-specific antibodies without the need of external adjuvant. Mice immunized with entities bearing 15 leucine residues were able to clear bacterial load from target organs without triggering the release of soluble inflammatory mediators. Thus, we have developed a well-defined and effective self-adjuvanting delivery system for peptide antigens.
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http://dx.doi.org/10.1126/sciadv.aax2285DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6989150PMC
January 2020

Chrysosporazines F-M: P-Glycoprotein Inhibitory Phenylpropanoid Piperazines from an Australian Marine Fish Derived Fungus, sp. CMB-F294.

J Nat Prod 2020 02 24;83(2):497-504. Epub 2020 Jan 24.

Division of Chemistry and Structural Biology, Institute for Molecular Bioscience , The University of Queensland , St Lucia , QLD 4072 , Australia.

Chemical analysis of the fungus sp. CMB-F294 isolated from the gastrointestinal tract of a market-purchased specimen of mullet yielded eight new alkaloids, belonging to a rare class of phenylpropanoid piperazines. Chrysosporazines F-M (-) occur as an equilibrium mixture of acetamide rotamers and feature unprecedented carbocyclic and heterocyclic scaffolds. Structures inclusive of absolute configuration were assigned by detailed spectroscopic analysis, supported by biosynthetic considerations. Structure-activity relationship studies determined that selected chrysosporazines were promising noncytotoxic inhibitors of the multidrug resistance efflux pump P-glycoprotein (P-gp), capable of reversing doxorubicin resistance in P-gp-overexpressing human colon carcinoma cells (SW620 Ad300). Chrysosporazine F () was particularly noteworthy, with a 2.5 μM cotreatment inducing a doxorubicin gain in sensitivity (GS 14) > 2-fold that of the positive control verapamil (GS 6.1).
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http://dx.doi.org/10.1021/acs.jnatprod.9b01181DOI Listing
February 2020

Polyacrylate-Peptide Antigen Conjugate as a Single-Dose Oral Vaccine against Group A .

Vaccines (Basel) 2020 Jan 13;8(1). Epub 2020 Jan 13.

School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Brisbane, QLD 4072, Australia.

Group A (GAS)-associated rheumatic heart disease is a leading cause of death caused by GAS infection. While antibiotics can treat the infection in most cases, growing antibiotic resistance, late medical intervention, and recurrent infection are major obstacles to the effective treatment of GAS-associated diseases. As GAS infection typically originates from the bacterial colonization of mucosal tissue in the throat, an oral vaccine that can generate both systemic and mucosal immune responses would solve problems associated with traditional medical interventions. Moreover, orally delivered vaccines are more easily administered and less expensive for mass immunization. In this study, the B-cell epitope J8, derived from GAS M protein, and universal T-helper Pan HLA-DR-binding epitope peptide (PADRE), were conjugated to poly (methyl acrylate) (PMA) to form a self-assembled nanoparticle vaccine candidate (PMA-P-J8). Strong systemic and mucosal immune responses were induced upon single oral immunization of mice with the conjugate. The antibodies generated were opsonic against GAS clinical isolates as measured after boost immunization. Thus, we developed a simple conjugate as an effective, adjuvant-free oral peptide-based vaccine.
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http://dx.doi.org/10.3390/vaccines8010023DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7157655PMC
January 2020

Microbioreactor Techniques for the Production and Spectroscopic Characterization of Microbial Peptides.

Methods Mol Biol 2020 ;2103:303-322

Institute for Molecular Bioscience, University of Queensland, Brisbane, QLD, Australia.

We have demonstrated that the simple and low-cost microbioreactor can speed up the bioprocessing techniques by using small amount of reagents and very few seed cultures to give results comparable with those obtained from the shake flask. The microbioreactor has the potential of replacing the normal conventional-scale process and offers a high-throughput efficient and analytical technique in addressing some of the challenges encountered in bioprocessing starting that includes bacterial growth and secondary metabolites production targeting the discovery of new antibacterial peptides. In our case studies, we proved that microbes were capable of growing in the microbioreactor and the production of microbial secondary metabolites (i.e., peptides) was detectable in HPLC-DAD-MS. We used QTOF-MS/MS to detect the production of peptides in the microbial culture. The purified peptides were characterized using 1D and 2D NMR, QTOF-MS/MS, and Marfey's analysis.
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http://dx.doi.org/10.1007/978-1-0716-0227-0_21DOI Listing
January 2021

The Effects of Conspecific Alarm Cues on Larval Cane Toads (Rhinella marina).

J Chem Ecol 2019 Oct 1;45(10):838-848. Epub 2019 Nov 1.

School of Life and Environmental Sciences A08, University of Sydney, Sydney, NSW, 2006, Australia.

Many aquatic organisms detect and avoid damage-released cues from conspecifics, but the chemical basis of such responses, and the effects of prolonged exposure to such cues, remain poorly understood. Injured tadpoles of the cane toad (Rhinella marina) produce chemical cues that induce avoidance by conspecific tadpoles; and chronic exposure to those cues decreases rates of tadpole survival and growth, and reduces body size at metamorphosis. Such effects suggest that we might be able to use the cane toads' alarm cue for biocontrol of invasive populations in Australia. In the present study, we examined behavioral and ecological effects of compounds that are present in cane toad tadpoles and thus, might trigger avoidance of crushed conspecifics. Four chemicals (L-Arg, L-Leu-L-Leu-OH, L-Leu-L-Ile-OH and suberic acid) induced behavioral avoidance in toad tadpoles at some (but not all) dosage levels, so we then exposed toad larvae to these chemicals over the entire period of larval development. Larval survival and size at metamorphosis were decreased by chronic exposure to crushed conspecifics (consistent with earlier studies), but not by exposure to any of the four chemicals. Indeed, L-Arg increased body size at metamorphosis. We conclude that the behavioral response to crushed conspecifics by cane toad tadpoles can be elicited by a variety of chemical cues, but that consistent exposure to these individual chemical cues does not affect tadpole viability or developmental trajectory. The optimal behavioral tactic of a tadpole may be to flee if it encounters even a single chemical cue likely to have come from an injured conspecific (indicative of predation risk), whereas the continuing presence of that single chemical (but no others) provides a less reliable signal of predation risk. Our data are consistent with results from studies on fish, that suggest a role for multiple chemicals in initiating alarm responses to damage-released cues.
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http://dx.doi.org/10.1007/s10886-019-01111-2DOI Listing
October 2019

Trivirensols: Selectively Bacteriostatic Sesquiterpene Trimers from the Australian Termite Nest-Derived Fungus CMB-TN16.

J Nat Prod 2019 11 18;82(11):3165-3175. Epub 2019 Oct 18.

Division of Chemistry and Structural Biology, Institute for Molecular Bioscience , The University of Queensland , St Lucia , QLD 4072 , Australia.

The termite nest-derived fungus CMB-TN16 cultivated on rice-based media produced seven new first-in-class trimeric sesquiterpenes, trivirensols A-G (-). Structures inclusive of absolute configurations were assigned by detailed spectroscopic analysis and biosynthetic considerations. Although trivirensols exhibit no cytotoxicity to mammalian carcinoma cells, selected examples are bacteriostatic against vancomycin-resistant (VRE). Structure-activity relationship (SAR) investigations combined with chemical stability studies documented bacteriostatic activity for trivirensols A () and B () and the co-metabolite divirensols A (), B (), and G (), all of which share a common terminal butenolide. Significantly, SAR studies also revealed bacteriostatic activity for trivirensols C () and G () and the co-metabolite divirensol C (), all of which share a common hydrated butenolide terminal. Of note, when exposed to VRE cell cultures, the hydrated butenolides , , and undergo rapid dehydration to corresponding butenolides, suggesting hydrated butenolides are a pro-drug form of the butenolide VRE bacteriostatic pharmacophore.
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http://dx.doi.org/10.1021/acs.jnatprod.9b00760DOI Listing
November 2019

A tetrapeptide class of biased analgesics from an Australian fungus targets the µ-opioid receptor.

Proc Natl Acad Sci U S A 2019 10 14;116(44):22353-22358. Epub 2019 Oct 14.

Discipline of Pharmacology, School of Medical Sciences, University of Sydney, NSW 2006, Australia;

An Australian estuarine isolate of sp. MST-MF667 yielded 3 tetrapeptides named the bilaids with an unusual alternating LDLD chirality. Given their resemblance to known short peptide opioid agonists, we elucidated that they were weak ( low micromolar) μ-opioid agonists, which led to the design of bilorphin, a potent and selective μ-opioid receptor (MOPr) agonist ( 1.1 nM). In sharp contrast to all-natural product opioid peptides that efficaciously recruit β-arrestin, bilorphin is G protein biased, weakly phosphorylating the MOPr and marginally recruiting β-arrestin, with no receptor internalization. Importantly, bilorphin exhibits a similar G protein bias to oliceridine, a small nonpeptide with improved overdose safety. Molecular dynamics simulations of bilorphin and the strongly arrestin-biased endomorphin-2 with the MOPr indicate distinct receptor interactions and receptor conformations that could underlie their large differences in bias. Whereas bilorphin is systemically inactive, a glycosylated analog, bilactorphin, is orally active with similar in vivo potency to morphine. Bilorphin is both a unique molecular tool that enhances understanding of MOPr biased signaling and a promising lead in the development of next generation analgesics.
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http://dx.doi.org/10.1073/pnas.1908662116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6825270PMC
October 2019

Chrysosporazines A-E: P-Glycoprotein Inhibitory Piperazines from an Australian Marine Fish Gastrointestinal Tract-Derived Fungus, sp. CMB-F214.

Org Lett 2019 10 23;21(19):8097-8100. Epub 2019 Sep 23.

Institute for Molecular Bioscience , The University of Queensland , St Lucia , QLD 4072 , Australia.

Chemical analysis of sp. CMB-F214, yielded five new piperazines, chrysosporazines A-E (-), with structures assigned by spectroscopic and X-ray analyses and biosynthetic considerations. The chrysosporazines - exist as an equilibrium of major and minor -acyl rotamers, while - incorporate an unprecedented hexahydro-6-pyrazino[1,2-]isoquinolin-6-one scaffold. The noncytotoxic chrysosporazines reverse doxorubicin drug resistance in P-glycoprotein overexpressing colon carcinoma cells (SW620 Ad300), with delivering a comparable gain in sensitivity to the positive control, verapamil.
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http://dx.doi.org/10.1021/acs.orglett.9b03094DOI Listing
October 2019

Cinerols, Nitrogenous Meroterpenoids from the Marine Sponge .

J Nat Prod 2019 09 18;82(9):2586-2593. Epub 2019 Sep 18.

Research Center for Marine Drugs, State Key Laboratory of Oncogenes and Related Genes, Department of Pharmacy, Ren Ji Hospital, School of Medicine , Shanghai Jiao Tong University , Shanghai , 200127 , People's Republic of China.

Eleven new nitrogenous meroterpenoids, cinerols A-K (-), were isolated from the marine sponge collected in the South China Sea, and their structures were determined by detailed spectroscopic analysis. Cinerols A () and B () feature a rare 5-pyrrolo[1,2a]benzimidazole moiety, while cinerols C-G (-) are examples of rare meroterpene benzoxazoles. The cinerols are noncytotoxic to human melanoma A375 cells at the concentration of 32 μM; however, selected cinerols exhibit moderate inhibitory activity against one or more of protein-tyrosine phosphatase 1B, ATP-citrate lyase, and SH2 domain-containing phosphatase-1 with IC values of 2.8-27 μM.
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http://dx.doi.org/10.1021/acs.jnatprod.9b00471DOI Listing
September 2019

Cholic Acid-based Delivery System for Vaccine Candidates against Group A Streptococcus.

ACS Med Chem Lett 2019 Sep 24;10(9):1253-1259. Epub 2019 Jul 24.

School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, QLD, Australia.

Peptide-based subunit vaccines require an immunostimulant (adjuvant) and/or delivery system to protect the antigenic peptide from degradation and induce the desired immunity. Currently available adjuvants are either too toxic for human use (experimental adjuvants) or they are limited for use in particular vaccines or licensed countries (commercial adjuvants). Therefore, there is an immediate need for novel adjuvants that are both safe and effective. Herein, we assessed the ability of cholic acid (a major bile acid) as a nontoxic, biodegradable, human-derived, potent vaccine delivery system. An antigenic peptide derived from Group A Streptococcus was conjugated to hydrophobic cholic acid via solid phase peptide synthesis to produce lipopeptide that self-assembled into rod-like nanoparticles under aqueous conditions. Following intranasal immunization in mice, this lipopeptide was capable of inducing the production of opsonic epitope-specific antibodies on its own and in liposomal formulation. The cholic acid-based conjugate induced significantly stronger humoral immune responses than cholera toxin-based adjuvant. Thus, we demonstrated, for the first time, capability of the human-derived lipid to act as a built-in immunoadjuvant for vaccines.
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http://dx.doi.org/10.1021/acsmedchemlett.9b00239DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6746084PMC
September 2019
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