ABSTRACT
Although the United States Food & Drug Administration (FDA) has provided guidance on the control of drug degradants for prescription drugs, there is less guidance on how to set degradant specifications for FDA OTC monograph drugs. Given that extensive impurity testing was not part of the safety paradigm in original OTC monographs, a weight of evidence (WOE) approach to qualify OTC degradants is proposed. This approach relies on in silico tools and read-across approaches alongside standard toxicity testing to determine safety. Using several drugs marketed under 21 CFR 341 as case studies, this research demonstrates the utility of a WOE approach across data-rich and data-poor degradants. Based on degradant levels ranging from 1 to 4% of the maximum daily doses of each case study drug and 10th percentile body weight data for each patient group, children were recognized as having the highest potential exposure relative to adults per body mass. Depending on data availability and relationship to the parent API, margins of safety (MOS) or exposure margins were calculated for each degradant. The findings supported safe use, and indicated that this contemporary WOE approach could be utilized to assess OTC degradants. This approach is valuable to establish specifications for degradants in OTCs.
Subject(s)
Antitussive Agents , Nonprescription Drugs , United States Food and Drug Administration , Nonprescription Drugs/adverse effects , Humans , United States , Antitussive Agents/adverse effects , Cough/drug therapy , Risk Assessment , Child , Drug Contamination , Adult , Toxicity Tests/methods , Common Cold/drug therapyABSTRACT
The United States Pharmacopeia (USP) is an independent, nonprofit science-based organization whose mission is to improve global health through public standards and related products for medicines, food and dietary supplements. Probiotic-based dietary supplements are increasingly popular in the marketplace and USP has developed fourteen monographs specific to probiotic ingredients, including representatives from the Genera Lactobacillus, Bacillus, Streptococcus, and Bifidobacterium. These monographs include the definition of the article, tests for identification, quantification assays (enumeration in the case of probiotics), limits for contaminants, and other quality parameters when appropriate. In addition to quality, the USP also considers the safety of probiotics for monograph development. This report includes an overview of the USP admission evaluation process for probiotics as well as a tabular summary of the probiotic monographs currently available. Pharmacopeia monographs can guide manufacturers and brand owners and protect consumers through establishment of quality standards.
ABSTRACT
Interest in botanicals, particularly as dietary supplement ingredients, is growing steadily. This growth, and the marketing of new ingredients and combination products as botanical dietary supplements, underscores the public health need for a better understanding of potential toxicities associated with use of these products. This article and accompanying template outline the resources to collect literature and relevant information to support the design of botanical toxicity studies. These resources provide critical information related to botanical identification, characterization, pre-clinical and clinical data, including adverse effects and interactions with pharmaceuticals. Toxicologists using these resources should collaborate with pharmacognosists and/or analytical chemists to enhance knowledge of the botanical material being tested. Overall, this guide and resource list is meant to help locate relevant information that can be leveraged to inform on decisions related to toxicity testing of botanicals, including the design of higher quality toxicological studies.
Subject(s)
Dietary Supplements , Drug-Related Side Effects and Adverse Reactions , Humans , Dietary Supplements/toxicityABSTRACT
Staphylococcus aureus is a human pathogen with many infections originating on mucosal surfaces. One common group of S. aureus is the USA200 (CC30) clonal group, which produces toxic shock syndrome toxin-1 (TSST-1). Many USA200 infections occur on mucosal surfaces, particularly in the vagina and gastrointestinal tract. This allows these organisms to cause cases of menstrual TSS and enterocolitis. The current study examined the ability of two lactobacilli, Lactobacillus acidophilus strain LA-14 and Lacticaseibacillus rhamnosus strain HN001, for their ability to inhibit the growth of TSST-1 positive S. aureus, the production of TSST-1, and the ability of TSST-1 to induce pro-inflammatory chemokines from human vaginal epithelial cells (HVECs). In competition growth experiments, L. rhamnosus did not affect the growth of TSS S. aureus but did inhibit the production of TSST-1; this effect was partially due to acidification of the growth medium. L. acidophilus was both bactericidal and prevented the production of TSST-1 by S. aureus. This effect appeared to be partially due to acidification of the growth medium, production of H2O2, and production of other antibacterial molecules. When both organisms were incubated with S. aureus, the effect of L. acidophilus LA-14 dominated. In in vitro experiments with HVECs, neither lactobacillus induced significant production of the chemokine interleukin-8, whereas TSST-1 did induce production of the chemokine. When the lactobacilli were incubated with HVECs in the presence of TSST-1, the lactobacilli reduced chemokine production. These data suggest that these two bacteria in probiotics could reduce the incidence of menstrual and enterocolitis-associated TSS. IMPORTANCE Toxic shock syndrome (TSS) Staphylococcus aureus commonly colonize mucosal surfaces, giving them the ability to cause TSS through the action of TSS toxin-1 (TSST-1). This study examined the ability of two probiotic lactobacilli to inhibit S. aureus growth and TSST-1 production, and the reduction of pro-inflammatory chemokine production by TSST-1. Lacticaseibacillus rhamnosus strain HN001 inhibited TSST-1 production due to acid production but did not affect S. aureus growth. Lactobacillus acidophilus strain LA-14 was bactericidal against S. aureus, partially due to acid and H2O2 production, and consequently also inhibited TSST-1 production. Neither lactobacillus induced the production of pro-inflammatory chemokines by human vaginal epithelial cells, and both inhibited chemokine production by TSST-1. These data suggest that the two probiotics could reduce the incidence of mucosa-associated TSS, including menstrual TSS and cases originating as enterocolitis.
Subject(s)
Probiotics , Shock, Septic , Staphylococcal Infections , Female , Humans , Staphylococcus aureus , Shock, Septic/prevention & control , Shock, Septic/microbiology , Lactobacillus/physiology , Hydrogen Peroxide/pharmacology , Enterotoxins , Chemokines , Staphylococcal Infections/prevention & control , Staphylococcal Infections/microbiologyABSTRACT
Having varied approaches to the design and manufacture of vaccines is critical in being able to respond to worldwide needs and newly emerging pathogens. Virus-like particles (VLPs) form the basis of two of the most successful licensed vaccines (against hepatitis B virus [HBV] and human papillomavirus). They are produced by recombinant expression of viral structural proteins, which assemble into immunogenic nanoparticles. VLPs can be modified to present unrelated antigens, and here we describe a universal "bolt-on" platform (termed VelcroVax) where the capturing VLP and the target antigen are produced separately. We utilize a modified HBV core (HBcAg) VLP with surface expression of a high-affinity binding sequence (Affimer) directed against a SUMO tag and use this to capture SUMO-tagged gp1 glycoprotein from the arenavirus Junín virus (JUNV). Using this model system, we have solved the first high-resolution structures of VelcroVax VLPs and shown that the VelcroVax-JUNV gp1 complex induces superior humoral immune responses compared to the noncomplexed viral protein. We propose that this system could be modified to present a range of antigens and therefore form the foundation of future rapid-response vaccination strategies. IMPORTANCE The hepatitis B core protein (HBc) forms noninfectious virus-like particles, which can be modified to present a capturing molecule, allowing suitably tagged antigens to be bound on their surface. This system can be adapted and provides the foundation for a universal "bolt-on" vaccine platform (termed VelcroVax) that can be easily and rapidly modified to generate nanoparticle vaccine candidates.
Subject(s)
Vaccines , Humans , Hepatitis B Core Antigens/genetics , Hepatitis B virus , Glycoproteins , VaccinationABSTRACT
A history of safe use is a backbone of safety assessments for many current probiotic species, however, there is no global harmonization regarding requirements for establishing probiotic safety for use in foods and supplements. As probiotic manufacturers are increasingly seeking to use new strains, novel species, and next-generation probiotics, justification based on a significant history of use may be challenged. There are efforts underway by a variety of stakeholders, including the United States Pharmacopeia (USP), to develop best practices guidelines for assessing the quality and safety of probiotics. A current initiative of the USP seeks to provide expert advice specific to safety considerations for probiotics. Toward this goal, this review provides a helpful summary guide to global regulatory guidelines. We question the suitability of traditional animal toxicology studies designed for testing chemicals for relevance in assessing probiotic safety. This includes discussion of the use of excessive dose levels, the length of repeated dose toxicity studies needed, and the most suitable animal species used in toxicology studies. In addition, the importance of proper manufacturing practices with regard to final product safety are also included. Thus, an outline of essential parameters of a comprehensive safety assessment for a probiotic are provided.
Subject(s)
Probiotics , Animals , Probiotics/adverse effects , Dietary SupplementsABSTRACT
Gamma-amino butyric acid (GABA) is marketed in the U.S. as a dietary supplement. USP conducted a comprehensive safety evaluation of GABA by assessing clinical studies, adverse event information, and toxicology data. Clinical studies investigated the effect of pure GABA as a dietary supplement or as a natural constituent of fermented milk or soy matrices. Data showed no serious adverse events associated with GABA at intakes up to 18 g/d for 4 days and in longer studies at intakes of 120 mg/d for 12 weeks. Some studies showed that GABA was associated with a transient and moderate drop in blood pressure (<10% change). No studies were available on effects of GABA during pregnancy and lactation, and no case reports or spontaneous adverse events associated with GABA were found. Chronic administration of GABA to rats and dogs at doses up to 1 g/kg/day showed no signs of toxicity. Because some studies showed that GABA was associated with decreases in blood pressure, it is conceivable that concurrent use of GABA with anti-hypertensive medications could increase risk of hypotension. Caution is advised for pregnant and lactating women since GABA can affect neurotransmitters and the endocrine system, i.e., increases in growth hormone and prolactin levels.
Subject(s)
Antihypertensive Agents/therapeutic use , Dietary Supplements , Performance-Enhancing Substances/therapeutic use , Product Surveillance, Postmarketing , gamma-Aminobutyric Acid/therapeutic use , Animals , Blood Pressure/drug effects , Dogs , Female , Fermentation , Humans , Male , Milk/chemistry , Pregnancy , Rats , Soy Foods/analysis , United StatesABSTRACT
Recent estimates for the global brain health supplement category, i.e. nootropic market size, will grow to nearly $5.8 billion by 2023. Overall, nearly one-quarter (23%) of adults currently take a supplement to maintain or improve brain health or delay and reverse dementia. Not surprisingly, the use of such supplements increases with age - more than one-third of the oldest generation (ages 74 and older) takes a supplement for brain health. This widespread use is being driven by a strong desire both in the younger and older generations to enhance cognitive performance and achieve healthy aging. The most prevalent botanicals currently dominating the nootropic marketplace include Gingko biloba, American ginseng, and Bacopa monnieri. However, other botanicals that affect stress, focus, attention, and sleep have also been procured by dietary supplement companies developing products for improving both, short and long-term brain health. This review focuses on efficacy data for neuroactive botanicals targeted at improving cognitive function, stress reduction, memory, mood, attention, concentration, focus, and alertness, including Bacopa monnieri, Ginkgo biloba, Holy basil, American ginseng, Gotu kola, Lemon balm, Common and Spanish sages and spearmint. Botanicals are discussed in terms of available clinical efficacy data and current safety profiles. Data gaps are highlighted for both efficacy and safety to bring attention to unmet needs and future research.
Subject(s)
Bacopa , Nootropic Agents , Adult , Aged , Brain , Cognition , Dietary Supplements , Humans , Nootropic Agents/adverse effectsABSTRACT
As part of the United States Pharmacopeia's ongoing review of dietary supplement safety data, a new comprehensive systematic review on green tea extracts (GTE) has been completed. GTEs may contain hepatotoxic solvent residues, pesticide residues, pyrrolizidine alkaloids and elemental impurities, but no evidence of their involvement in GTE-induced liver injury was found during this review. GTE catechin profiles vary significantly with manufacturing processes. Animal and human data indicate that repeated oral administration of bolus doses of GTE during fasting significantly increases bioavailability of catechins, specifically EGCG, possibly involving saturation of first-pass elimination mechanisms. Toxicological studies show a hepatocellular pattern of liver injury. Published adverse event case reports associate hepatotoxicity with EGCG intake amounts from 140â¯mg to â¼1000â¯mg/day and substantial inter-individual variability in susceptibility, possibly due to genetic factors. Based on these findings, USP included a cautionary labeling requirement in its Powdered Decaffeinated Green Tea Extract monograph that reads as follows: "Do not take on an empty stomach. Take with food. Do not use if you have a liver problem and discontinue use and consult a healthcare practitioner if you develop symptoms of liver trouble, such as abdominal pain, dark urine, or jaundice (yellowing of the skin or eyes)."
ABSTRACT
During the 25 years since the US Congress passed the Dietary Supplement Health and Education Act (DSHEA), the law that transformed the US Food and Drug Administration's (FDA's) authority to regulate dietary supplements, the dietary supplement market has grown exponentially. Retail sales of herbal products, a subcategory of dietary supplements, have increased 83% from 2008 to 2018 ($4.8 to $8.8 billion USD). Although consumers often equate "natural" with "safe", it is well recognized by scientists that constituents in these natural products (NPs) can result in toxicity. Additionally, when NPs are co-consumed with pharmaceutical agents, the precipitant NP can alter drug disposition and drug delivery, thereby enhancing or reducing the therapeutic effect of the object drug(s). With the widespread use of NPs, these effects can be underappreciated. We present a summary of a symposium presented at the Annual Meeting of the Society of Toxicology 2019 (12 March 2019) that discussed potential toxicities of NPs alone and in combination with drugs.
Subject(s)
Biological Products/adverse effects , Legislation, Food , Pharmaceutical Preparations , Biological Products/administration & dosage , Dietary Supplements , Humans , Marketing , Pharmaceutical Preparations/administration & dosage , United States , United States Food and Drug AdministrationABSTRACT
In 2016, the World Health Organization classification system of testicular tumors included the new entity prepubertal-type teratoma based on its morphological and molecular profile, and the realization that these tumors may occur in postpubertal men. For treatment and prognostic purposes, it is important to distinguish prepubertal-type teratoma from the usual postpubertal-type teratoma, because the former is benign unlike the latter. The distinction may be challenging. In this study, we investigated clinical, morphological, and molecular criteria for distinguishing prepubertal-type teratoma from postpubertal-type teratoma in a prospective series of pure testicular teratomas. All cases of pure teratoma in postpubertal men assessed at Barts Health NHS Trust or in consultation since the introduction of routine investigation of chromosome 12p status in 2010 were reviewed. Morphological features suggestive of prepubertal-type teratoma were observed in 14 out of 35 cases. All underwent molecular testing and none displayed 12p amplification. Mean tumor size was 16 mm (range 7-28 mm). None had associated germ cell neoplasia in situ or significant atrophy. Four incorporated a well-differentiated neuroendocrine tumor, 1-2 mm in size. Of the ten patients with follow-up information, none have recurred or metastasized. Twenty-one of the 35 cases were diagnosed as postpubertal-type teratoma, mean tumor size 40 mm (range 6-90 mm). One case underwent molecular testing: a tumor of pure skeletal muscle differentiation and possessed 12p amplification. Three cases presented with clinical metastases. Eight cases contained immature areas, ten cases had associated germ cell neoplasia in situ, and 17 cases had severe atrophy of the parenchyma. One case with neither germ cell neoplasia in situ nor atrophy showed necrosis. We conclude that both morphological and molecular features are of help in differentiating prepubertal-type teratoma from postpubertal-type teratoma. In nearly all postpubertal-type teratomas, molecular testing was unnecessary, and merely confirmed the morphological impression in the prepubertal-type teratomas. Our study confirmed the high incidence of well-differentiated neuroendocrine tumors in the prepubertal-type.
Subject(s)
Biomarkers, Tumor/genetics , Puberty , Teratoma/genetics , Teratoma/pathology , Testicular Neoplasms/genetics , Testicular Neoplasms/pathology , Adult , Aged , Biomarkers, Tumor/analysis , Biopsy , Cell Differentiation , Diagnosis, Differential , Genetic Predisposition to Disease , Humans , Immunohistochemistry , Male , Middle Aged , Molecular Diagnostic Techniques , Phenotype , Predictive Value of Tests , Prospective Studies , Teratoma/chemistry , Testicular Neoplasms/chemistry , Tumor Burden , Young AdultABSTRACT
The seeds of the guarana plant (Paullinia cupana Kunth, family Sapindaceae) are well-known to many cultures as a stimulant, aphrodisiac, and astringent. Its rhizome was traditionally boiled into a tea by Amazonian cultures. Today, guarana seeds are ground to a fine powder and sold as powder, tablets, and capsules. This review focuses on the traditional uses, phytochemistry, and biological activities of the guarana seed to evaluate its safety as a dietary ingredient. A comprehensive review of published literature was conducted to identify articles that focused on the phytochemistry, pharmacology, and safety of guarana. On the basis of this review, guarana is not currently known to be associated causally with any serious health risks when consumed properly. Overall, guarana is generally recognized as safe as a dietary ingredient marketed for its flavor and caffeine content. If guidelines for caffeine intake are respected, guarana consumption is not likely to be associated with any serious health risks.
Subject(s)
Paullinia/chemistry , Plant Extracts/chemistry , Seeds/chemistry , Animals , Food Safety , Humans , Paullinia/adverse effects , Paullinia/metabolism , Plant Extracts/adverse effects , Plant Extracts/metabolism , Seeds/adverse effects , Seeds/metabolismABSTRACT
Botanical safety science continues to evolve as new tools for risk assessment become available alongside continual desire by consumers for "natural" botanical ingredients in consumer products. Focusing on botanical food/dietary supplements a recent international roundtable meeting brought together scientists to discuss the needs, available tools, and ongoing data gaps in the botanical safety risk assessment process. Participants discussed the key elements of botanical safety evaluations. They provided perspective on the use of a decision tree methodology to conduct a robust risk assessment and concluded with alignment on a series of consensus statements. This discussion highlighted the strengths and vulnerabilities in common assumptions, and the participants shared additional perspective to ensure that this end-to-end safety approach is sufficient, actionable and timely. Critical areas and data gaps were identified as opportunities for future focus. These include, better context on history of use, systematic assessment of weight of evidence, use of in silico approaches, inclusion of threshold of toxicological concern considerations, individual substances/matrix interactions of plant constituents, assessing botanical-drug interactions and adaptations needed to apply to in vitro and in vivo pharmacokinetic modelling of botanical constituents.
Subject(s)
Decision Trees , Dietary Supplements/adverse effects , Plant Preparations/adverse effects , Toxicology/methods , Animals , Consensus , Consumer Product Safety , Dose-Response Relationship, Drug , Humans , Models, Biological , Patient Safety , Plant Preparations/pharmacokinetics , Risk Assessment , Risk Factors , Toxicokinetics , Toxicology/standardsABSTRACT
1,2-Unsaturated pyrrolizidine alkaloids (PAs) are sometimes present in foods or herbal supplements/medicines as impurities and pose potential concerns for liver genotoxicity/carcinogenicity. PAs display a strong structure toxicity relationship, however, current regulatory approaches to risk assessment take the precautionary approach of assuming all PAs display the same potency as the most toxic congeners lasiocarpine (LAS) and riddelliine (RID). Here we explore the relative potencies of a series of structurally diverse PAs by measuring DNA adduct formation in vitro in a rat sandwich culture hepatocyte (SCH) cell system. The adducts generated are consistent with those identified in vivo as biomarkers of PA exposure and potential liver-tumor formation. DNA reactive PAs require metabolic activation to form intermediates that bind DNA, therefore, adduct formation is a direct reflection of reactive metabolite formation. Since the area under the concentration versus time curve (AUC) for the depletion of parent PA from the extracellular media is a measure of PA exposure, the ratio of adducts/AUC provides a measure of hepatocyte exposure to DNA-binding metabolites corresponding to an intrinsic potency for DNA adduct formation. Intrinsic potencies relative to potencies for LAS compare well with existing relative potency data further affirming that PA toxicity varies considerably with chemical structure.
Subject(s)
DNA Adducts/metabolism , Pyrrolizidine Alkaloids/metabolism , Pyrrolizidine Alkaloids/toxicity , Animals , Dose-Response Relationship, Drug , Hepatocytes/drug effects , Hepatocytes/metabolism , Kinetics , Male , Molecular Structure , Pyrrolizidine Alkaloids/chemistry , Rats, Sprague-DawleyABSTRACT
Botanical dietary supplements are complex mixtures containing one or more botanical ingredient(s), each containing numerous constituents potentially responsible for its purported biological activity. Absorption, distribution, metabolism, and excretion (ADME) data are critical to understand the safety of botanical dietary supplements, including their potential for pharmacokinetic botanical-drug or botanical-botanical interactions. However, ADME data for botanical dietary supplements are rarely available and frequently inadequate to characterize their fate in vivo. Based on an assessment of the current status of botanical dietary supplements ADME research, the following key areas are identified that require robust data for human safety assessment: 1) phytochemical characterization including contaminant analysis and botanical authentication; 2) in vitro and/or in vivo data for identifying potential botanical-botanical or botanical-drug interactions and active/marker constituents; 3) robust ADME study design to include systemic exposure data on active/marker constituents using traditional or novel analytical chemistry and statistical approaches such as poly-pharmacokinetics; and 4) investigation of human relevance. A case study with Ginkgo biloba extract is used to highlight the challenges and proposed approaches in using ADME data for human safety assessment of botanical dietary supplements.
Subject(s)
Dietary Supplements , Phytochemicals/pharmacokinetics , Animals , Ginkgo biloba , Herb-Drug Interactions , Humans , Plant Extracts/pharmacokinetics , Xenobiotics/pharmacokineticsABSTRACT
The United States Pharmacopeia (USP) is an independent, nonprofit, science-based organization whose mission is to improve global health through public quality standards for dietary supplements, medicines, and food ingredients.1 Before developing standards for dietary supplement ingredients, the USP performs an "Admission Evaluation" (Figure 1), which includes an assessment to ascertain that an ingredient does not present a serious health risk.2 This article discusses the challenges encountered during the evaluation of botanicals and proposes possible solutions.
Subject(s)
Consumer Product Safety/standards , Dietary Supplements/standards , Patient Safety/standards , Pharmacopoeias as Topic/standards , Phytotherapy/standards , Plant Preparations/standards , Quality Control , Quality Improvement/standards , Animals , Dietary Supplements/adverse effects , Humans , Phytotherapy/adverse effects , Plant Preparations/adverse effects , Risk Assessment , United StatesABSTRACT
Botanicals are plant-derived products that have been consumed by humans for centuries. Today, the marketing and use of botanicals for health and wellness benefits continues to thrive worldwide, with consumers projected to spend more than $140 billion globally by 2024 (Global Analysis, Inc). However, research on the quality and safety of these products has lagged behind sales. Because of this divergence, opportunities abound for collaborations amongst scientists from industry, academia, and government to address these unmet public health needs. Clinical pharmacologists and toxicologists from all of these sectors play critical roles in developing harmonized approaches to achieve the common goal of ensuring botanical products with superior quality and safety.
Subject(s)
Dietary Supplements , Phytotherapy , Plant Preparations/therapeutic use , Plants, Medicinal , Animals , Consumer Product Safety , Dietary Supplements/adverse effects , Dietary Supplements/history , Dietary Supplements/standards , Forecasting , History, 16th Century , History, 18th Century , History, 19th Century , History, 20th Century , History, 21st Century , History, Ancient , Humans , Patient Safety , Phytotherapy/adverse effects , Phytotherapy/history , Phytotherapy/standards , Plant Preparations/adverse effects , Plant Preparations/history , Plant Preparations/standards , Plants, Medicinal/adverse effects , Quality Control , Risk AssessmentABSTRACT
Exposure to botanicals in dietary supplements is increasing across many geographies; with increased expectations from consumers, regulators, and industry stewards centered on quality and safety of these products. We present a tiered approach to assess the safety of botanicals, and an in silico decision tree to address toxicity data gaps. Tier 1 describes a Threshold of Toxicologic Concern (TTC) approach that can be used to assess the safety of conceptual levels of botanicals. Tier 2 is an approach to document a history of safe human use for botanical exposures higher than the TTC. An assessment of botanical-drug interaction (BDI) may also be necessary at this stage. Tier 3 involves botanical chemical constituent identification and safety assessment and the in silico approach as needed. Our novel approaches to identify potential hazards and establish safe human use levels for botanicals is cost and time efficient and minimizes reliance on animal testing.
Subject(s)
Consumer Product Safety , Dietary Supplements/adverse effects , Drug Industry , Patient Safety , Phytotherapy/adverse effects , Plant Preparations/adverse effects , Plants, Medicinal/adverse effects , Toxicity Tests/standards , Animals , Consumer Product Safety/standards , Dietary Supplements/standards , Drug Industry/standards , Humans , Patient Safety/standards , Phytotherapy/standards , Plant Preparations/standards , Quality Control , Risk AssessmentABSTRACT
The hepatitis B virus (HBV) core protein (HBc) has formed the building block for virus-like particle (VLP) production for more than 30 years. The ease of production of the protein, the robust ability of the core monomers to dimerize and assemble into intact core particles, and the strong immune responses they elicit when presenting antigenic epitopes all demonstrate its promise for vaccine development (reviewed in Pumpens and Grens (Intervirology 44: 98-114, 2001)). HBc has been modified in a number of ways in attempts to expand its potential as a novel vaccine platform. The HBc protein is predominantly α-helical in structure and folds to form an L-shaped molecule. The structural subunit of the HBc particle is a dimer of monomeric HBc proteins which together form an inverted T-shaped structure. In the assembled HBc particle the four-helix bundle formed at each dimer interface appears at the surface as a prominent "spike." The tips of the "spikes" are the preferred sites for the insertion of foreign sequences for vaccine purposes as they are the most highly exposed regions of the assembled particles. In the tandem-core modification two copies of the HBc protein are covalently linked by a flexible amino acid sequence which allows the fused dimer to fold correctly and assemble into HBc particles. The advantage of the modified structure is that the assembly of the dimeric subunits is defined and not formed by random association. This facilitates the introduction of single, larger sequences at the tip of each surface "spike," thus overcoming the conformational clashes contingent on insertion of large structures into monomeric HBc proteins.Differences in inserted sequences influence the assembly characteristics of the modified proteins, and it is important to optimize the design of each novel construct to maximize efficiency of assembly into regular VLPs. In addition to optimization of the construct, the expression system used can also influence the ability of recombinant structures to assemble into regular isometric particles. Here, we describe the production of recombinant tandem-core particles in bacterial, yeast and plant expression systems.
Subject(s)
Hepatitis B Core Antigens/genetics , Hepatitis B virus/genetics , Recombinant Fusion Proteins/genetics , Vaccines, Virus-Like Particle/genetics , Amino Acid Sequence , Bacteria/virology , Epitopes/genetics , Pichia/genetics , Pichia/virology , Plants/virology , Viral Vaccines/genetics , Yeasts/virologyABSTRACT
Use of herbal dietary supplements by the public is common and has been happening for centuries. In the United States, the Food and Drug Administration has a limited scope of regulation over marketed herbal dietary supplements, which may contain toxic botanical compounds that pose a public health risk. While the Food and Drug Administration has made efforts to prohibit the sale of unsafe herbal dietary supplements, numerous reports have proliferated of adverse events due to these supplements. This literature review investigates bioactive plant compounds commonly used in herbal dietary supplements and their relative toxicities. Using primarily the National Library of Medicine journal database and SciFinder for current reports, 47 toxic compounds in 55 species from 46 plant families were found to demonstrate harmful effects due to hepatic, cardiovascular, central nervous system, and digestive system toxicity. This review further contributes a novel and comprehensive view of toxicity across the botanical dietary market, and investigates the toxicity of the top ten botanical dietary supplements purchased in the United States of America to gauge the exposure risk of toxicity to the public. The criteria of measuring toxicity in this review (plant compound, family, quantity, and toxicity effects) across the entire market in the United States, with special attention to those supplements whose exposure to the consumer is maximal, provides a unique contribution to the investigation of botanical supplements.