Engineering and expression of a human rotavirus candidate vaccine in Nicotiana benthamiana

Production of Bovine Rotavirus VP6 Subunit Vaccine in a Transgenic Fodder Crop, Egyptian Clover (Berseem, Trifolium alexandrinum) that Elicits Immune Responses in Rabbit

Group A rotavirus causes acute gastroenteritis in young ones of animals worldwide and is responsible for a high rate of their morbidity and mortality leading to huge economic losses. Developing affordable and safer vaccine on large scale is imperative to reach cattle population worldwide for the long-term control of diarrhea. Rotavirus middle capsid protein layer, VP6, is the most immunogenic and highly conserved protein that induces immune responses against rotavirus. In the present study, bovine group A rotavirus VP6 protein has been expressed for the first time in a highly nutritious and palatable forage crop, Trifolium alexandrinum, using Agrobacterium tumefaciens-mediated stable nuclear transformation. Transgenic nature of the shoots regenerated from cotyledon explants and rooted on hygromycin-containing medium was confirmed by polymerase chain reaction (PCR), Southern blot hybridization, reverse transcription-PCR (RT-PCR) and quantitative real-time PCR (qPCR), and protein expression and quantification by Western blot and enzyme-linked immune-sorbent assay (ELISA), respectively. The transformation efficiency of 2.10% was obtained. The highest amount of VP6 protein produced in a transgenic line was 402 ng/g fresh weights (0.03% of total soluble protein). Oral feeding of transgenic leafy shoots expressing VP6 protein stimulated systemic immunity by inducing significantly higher titers of anti-VP6 serum IgG antibodies in rabbit to reduce rotavirus infection. These transgenic fodder plants offer safer vaccine produced on large scale at low cost with reduced regulatory issues to improve livestock's health and wealth. These plants would be used as alternative to the current live attenuated vaccines to protect young calves against rotavirus infection.

Rotavirus Particle Disassembly and Assembly In Vivo and In Vitro

Rotaviruses (RVs) are non-enveloped multilayered dsRNA viruses that are major etiologic agents of diarrheal disease in humans and in the young in a large number of animal species. The viral particle is composed of three different protein layers that enclose the segmented dsRNA genome and the transcriptional complexes. Each layer defines a unique subparticle that is associated with a different phase of the replication cycle. Thus, while single- and double-layered particles are associated with the intracellular processes of selective packaging, genome replication, and transcription, the viral machinery necessary for entry is located in the third layer. This modular nature of its particle allows rotaviruses to control its replication cycle by the disassembly and assembly of its structural proteins. In this review, we examine the significant advances in structural, molecular, and cellular RV biology that have contributed during the last few years to illuminating the intricate details of the RV particle disassembly and assembly processes.

Expression and Purification of Porcine Rotavirus Structural Proteins in Silkworm Larvae as a Vaccine Candidate

In this study, silkworm larvae were used for expression of porcine rotavirus A (KS14 strain) inner capsid protein, VP6, and outer capsid protein, VP7. Initially, VP6 was fused with Strep-tag II and FLAG-tag (T-VP6), and T-VP6 was fused further with the signal peptide of Bombyx mori 30k6G protein (30k-T-VP6). T-VP6 and 30 k-T-VP6 were then expressed in the fat body and hemolymph of silkworm larvae, respectively, with respective amounts of 330 μg and 50 μg per larva of purified protein. Unlike T-VP6, 30k-T-VP6 was N-glycosylated due to attached signal peptide. Also, VP7 was fused with PA-tag (VP7-PA). Additionally, VP7 was fused with Strep-tag II, FLAG-tag, and the signal peptide of Bombyx mori 30k6G protein (30k-T-ΔVP7). Both VP7-PA and 30k-T-ΔVP7 were expressed in the hemolymph of silkworm larvae, with respective amounts of 26 μg and 49 μg per larva of purified protein, respectively. The results from our study demonstrated that T-VP6 formed nanoparticles of greater diameter compared with the ones formed by 30k-T-VP6. Also, higher amount of VP6 expressed in silkworm larvae reveal that VP6 holds the potential for its use in vaccine development against porcine rotavirus with silkworm larvae as a promising host for the production of such multi-subunit vaccines.

Energy-efficient production of vaccine protein against porcine edema disease from transgenic lettuce (Lactuca sativa L.)

The development of functional protein production systems using transgenic plants as hosts has been rapidly progressing in recent years. Lettuce (Lactuca sativa L.) has been studied as one such host, and it has been reported that the biomass of lettuce per area and target protein expression level can be increased by optimizing the cultivation conditions. Therefore, we investigated methods to minimize the input light energy per target protein to reduce production costs. Herein, we examined the yield of a nontoxic B subunit of Stx2e (Stx2eB) from transgenic lettuce under various cultivation conditions. Stx2eB acts as a vaccine against swine edema disease. The effects of photon flux densities (PPFDs), photoperiod, and light source on Stx2eB production were examined and the findings suggested that 400 μmol m-2 s-1, 24 h, and white LED lamps, respectively, contributed to energy-efficient Stx2eB production. In addition, Stx2eB was produced 1.4 times more efficiently per unit area time using a high plant density (228.5 plants m-2) than a common density (30.4 plants m-2). The findings of the present study can facilitate the development of energy-efficient and low-cost production processes for vaccine protein production, considering temporal and spatial perspectives.

Enhanced HIV SOSIP Envelope yields in plants through transient co-expression of peptidyl-prolyl isomerase B and calreticulin chaperones and ER targeting

High yield production of recombinant HIV SOSIP envelope (Env) trimers has proven elusive as numerous disulfide bonds, proteolytic cleavage and extensive glycosylation pose high demands on the host cell machinery and stress imposed by accumulation of misfolded proteins may ultimately lead to cellular toxicity. The present study utilized the Nicotiana benthamiana/p19 (N.b./p19) transient plant system to assess co-expression of two ER master regulators and 5 chaperones, crucial in the folding process, to enhance yields of three Env SOSIPs, single chain BG505 SOSIP.664 gp140, CH505TF.6R.SOSIP.664.v4.1 and CH848-10.17-DT9. Phenotypic changes in leaves induced by SOSIP expression were employed to rapidly identify chaperone-assisted improvement in health and expression. Up to 15-fold increases were obtained by co-infiltration of peptidylprolvl isomerase (PPI) and calreticulin (CRT) which were further enhanced by addition of the ER-retrieval KDEL tags to the SOSIP genes; levels depending on individual SOSIP type, day of harvest and chaperone gene dosage. Results are consistent with reducing SOSIP misfolding and cellular stress due to increased exposure to the plant host cell's calnexin/calreticulin network and accelerating the rate-limiting cis-trans isomerization of Xaa-Pro peptide bonds respectively. Plant transient co-expression facilitates rapid identification of host cell factors and will be translatable to other complex glycoproteins and mammalian expression systems.

Transient Expression in Cytoplasm and Apoplast of Rotavirus VP6 Protein Fused to Anti-DEC205 Antibody in Nicotiana benthamiana and Nicotiana sylvestris

Rotavirus is the most common cause of severe diarrhea in infants and children worldwide and is responsible for about 215,000 deaths annually. Over 85% of these deaths originate in low-income/developing countries in Asia and Africa. Therefore, it is necessary to explore the development of vaccines that avoid the use of "living" viruses and furthermore, vaccines that have viral antigens capable of generating powerful heterotypic responses. Our strategy is based on the expression of the fusion of the anti-DEC205 single-chain variable fragment (scFv) coupled by an OLLAS tag to a viral protein (VP6) of Rotavirus in Nicotiana plants. It was possible to express transiently in N. benthamiana and N. sylvestris a recombinant protein consisting of the single chain variable fragment linked by an OLLAS tag to the VP6 protein. The presence of the recombinant protein, which had a molecular weight of approximately 75 kDa, was confirmed by immunodetection, in both plant species and in both cellular compartments (cytoplasm and apoplast) where it was expressed. In addition, the recombinant protein was modeled, and it was observed that some epitopes of interest are exposed on the surface, which could favor their immunogenic response.

Plant-Based COVID-19 Vaccines: Current Status, Design, and Development Strategies of Candidate Vaccines

The prevalence of the coronavirus disease 2019 (COVID-19) pandemic in its second year has led to massive global human and economic losses. The high transmission rate and the emergence of diverse SARS-CoV-2 variants demand rapid and effective approaches to preventing the spread, diagnosing on time, and treating affected people. Several COVID-19 vaccines are being developed using different production systems, including plants, which promises the production of cheap, safe, stable, and effective vaccines. The potential of a plant-based system for rapid production at a commercial scale and for a quick response to an infectious disease outbreak has been demonstrated by the marketing of carrot-cell-produced taliglucerase alfa (Elelyso) for Gaucher disease and tobacco-produced monoclonal antibodies (ZMapp) for the 2014 Ebola outbreak. Currently, two plant-based COVID-19 vaccine candidates, coronavirus virus-like particle (CoVLP) and Kentucky Bioprocessing (KBP)-201, are in clinical trials, and many more are in the preclinical stage. Interim phase 2 clinical trial results have revealed the high safety and efficacy of the CoVLP vaccine, with 10 times more neutralizing antibody responses compared to those present in a convalescent patient's plasma. The clinical trial of the CoVLP vaccine could be concluded by the end of 2021, and the vaccine could be available for public immunization thereafter. This review encapsulates the efforts made in plant-based COVID-19 vaccine development, the strategies and technologies implemented, and the progress accomplished in clinical trials and preclinical studies so far.

Development and characterization of a plant-derived rotavirus-like particle vaccine

BACKGROUND

Virus-like particles (VLPs) are unable to replicate in the recipient but stimulate the immune system through recognition of repetitive subunits. Parenterally delivered rotavirus-VLP (Ro-VLP) vaccine could have the potential to overcome the weaknesses of licensed oral live-attenuated rotavirus vaccines, namely, low efficacy in low-income and high mortality settings and a potential risk of intussusception.

METHODS

A monovalent Ro-VLP composed of viral protein (VP) 7, VP6 and VP2 of G1 genotype specificity was produced in Nicotiana benthamiana using Agrobacterium tumefaciens infiltration-based transient recombinant expression system. Plants expressing recombinant G1 Ro-VLP were harvested, then the resultant biomass was processed through a series of clarification and purification steps including standard extraction, filtration, ultrafiltration and chromatography. The purified G1 Ro-VLP was subsequently examined for its immunogenicity and toxicological profile using animal models.

RESULTS

G1 Ro-VLP had a purity of ≥90% and was structurally similar to triple-layered rotavirus particles as determined by cryogenic transmission electron microscopy. Two doses of aluminum hydroxide-adjuvanted G1 Ro-VLP (1 μg, 5 μg or 30 μg), administered intramuscularly, elicited a robust homotypic neutralizing antibody response in rats. Also, rabbits administered G1 Ro-VLP (10 μg or 30 μg) four times intramuscularly with aluminum hydroxide adjuvant did not show any significant toxicity.

CONCLUSIONS

Plant-derived Ro-VLP composed of VP7, VP6 and VP2 structural proteins would be a plausible alternative to live-attenuated oral rotavirus vaccines currently distributed worldwide.

Recombinant Lactobacillus plantarum NC8 strain expressing porcine rotavirus VP7 induces specific antibodies in BALB/c mice

The major etiologic agent that causes acute gastroenteritis worldwide in young animals and children is Group A rotavirus. Currently, commercially available vaccines do not often prevent porcine rotavirus (PRV) infection. In this study, we evaluated the efficacy of oral recombinant Lactobacillus vaccine against PRV in a mouse model. Lactobacillus plantarum NC8 was used as the host strain, and bacterial vectors were constructed, because the NC8 isolated has shown the capability to survive gastric transit and to colonize the intestinal tract of humans and other mammals. To explore the immunological mechanisms, lactic acid bacterial vectors were used to express VP7 antigen from PRV. We constructed an L. plantarum strain with surface-displayed VP7, named NC8-pSIP409-pgsA-VP7-DCpep. The expressed recombinant protein had a molecular weight of ∼37 kDa. The strain was used to immunize BALB/c mice to evaluate their immunomodulatory characteristics. Mice were orally immunized with recombinant L. plantarum NC8-pSIP409-pgsA-VP7-DCpep at a dose of 2 × 109 colony forming units/200 µl. The results showed that NC8-pSIP409-pgsA-VP7-DCpep significantly stimulated the differentiation of dendritic cells (DCs) in Peyer's patches (PPs) and increased the serum levels of IL-4 and IFN-γ, as measured by enzyme-linked immunosorbent assay in mice treated with NC8-pSIP409-pgsA-VP7-DCpep. Compared to the empty vector group, NC8-pSIP409-pgsA-VP7-DCpep significantly increased the production of B220+ B cells in mesenteric lymph nodes (MLNs) and PPs and also increased the titer levels of the VP7-specific antibodies, including IgG and sIgA. The administration of NC8-pSIP409-pgsA-VP7-DCpep mediated relatively broad cellular responses. This study reveals that clear alternatives exist for PRV control strategies and provides information on PRV infection.

Soluble Human Angiotensin- Converting Enzyme 2 as a Potential Therapeutic Tool for COVID-19 is Produced at High Levels In Nicotiana benthamiana Plant With Potent Anti-SARS-CoV-2 Activity

The coronavirus disease 2019 (COVID-19) pandemic, which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has rapidly spread to more than 222 countries and has put global public health at high risk. The world urgently needs a safe, cost-effective SARS-CoV-2 vaccine as well as therapeutic and antiviral drugs to combat COVID-19. Angiotensin-converting enzyme 2 (ACE2), as a key receptor for SARS-CoV-2 infections, has been proposed as a potential therapeutic tool in patients with COVID-19. In this study, we report a high-level production (about ∼0.75 g/kg leaf biomass) of human soluble (truncated) ACE2 in the Nicotiana benthamiana plant. After the Ni-NTA single-step, the purification yields of recombinant plant produced ACE2 protein in glycosylated and deglycosylated forms calculated as ∼0.4 and 0.5 g/kg leaf biomass, respectively. The plant produced recombinant human soluble ACE2s successfully bind to the SARS-CoV-2 spike protein. Importantly, both deglycosylated and glycosylated forms of ACE2 are stable at increased temperatures for extended periods of time and demonstrated strong anti-SARS-CoV-2 activities in vitro. The half maximal inhibitory concentration (IC50) values of glycosylated ACE2 (gACE2) and deglycosylated ACE2 (dACE2) were ∼1.0 and 8.48 μg/ml, respectively, for the pre-entry infection, when incubated with 100TCID₅₀ of SARS-CoV-2. Therefore, plant produced soluble ACE2s are promising cost-effective and safe candidates as a potential therapeutic tool in the treatment of patients with COVID-19.

Co-expression of human calreticulin significantly improves the production of HIV gp140 and other viral glycoproteins in plants

Plant molecular farming (PMF) is rapidly gaining traction as a viable alternative to the currently accepted paradigm of producing biologics. While the platform is potentially cheaper and more scalable than conventional manufacturing systems, expression yields and appropriate post-translational modifications along the plant secretory pathway remain a challenge for certain proteins. Viral fusion glycoproteins in particular are often expressed at low yields in plants and, in some cases, may not be appropriately processed. Recently, however, transiently or stably engineering the host plant has shown promise as a strategy for producing heterologous proteins with more complex maturation requirements. In this study we investigated the co-expression of a suite of human chaperones to improve the production of a human immunodeficiency virus (HIV) type 1 soluble gp140 vaccine candidate in Nicotiana benthamiana plants. The co-expression of calreticulin (CRT) resulted in a dramatic increase in Env expression and ameliorated the endoplasmic reticulum (ER) stress response - as evidenced by lower transcript abundance of representative stress-responsive genes. The co-expression of CRT similarly improved accumulation of glycoproteins from Epstein-Barr virus (EBV), Rift Valley fever virus (RVFV) and chikungunya virus (CHIKV), suggesting that the endogenous chaperone machinery may impose a bottleneck for their production. We subsequently successfully combined the co-expression of human CRT with the transient expression of human furin, to enable the production of an appropriately cleaved HIV gp140 antigen. These transient plant host engineering strategies are a promising approach for the production of high yields of appropriately processed and cleaved viral glycoproteins.

Expression of an scFv antibody fragment in Nicotiana benthamiana and in vitro assessment of its neutralizing potential against the snake venom metalloproteinase BaP1 from Bothrops asper

Human accidents with venomous snakes represent an overwhelming public health problem, mainly in rural populations of underdeveloped countries. Their high incidence and the severity of the accidents result in 81,000 to 138,000 deaths per year. The treatment is based on the administration of purified antibodies, produced by hyper immunization of animals to generate immunoglobulins (Igs), and then obtained by fractionating hyper immune plasma. The use of recombinant antibodies is an alternative to conventional treatment of snakebite envenoming, particularly the Fv fragment, named the single-chain variable fragment (scFv). We have produced recombinant single chain variable fragment scFv against the venom of the pit viper Bothrops asper at high levels expressed transiently and stably in transgenic plants and in vitro cultures that is reactive to BaP1 (a metalloproteinase from B. asper venom). The yield from stably transformed plants was significantly (p > 0.05) higher than the results in from transient expression. In addition, scFvBaP1 yields from systems derived from stable transformation were: transgenic callus 62 μg/g (±2); biomass from cell suspension cultures 83 μg/g (±0.2); culture medium from suspensions 71.75 mg/L (±6.18). The activity of scFvBaP1 was confirmed by binding and neutralization of the fibrin degradation induced by BnP1 toxins from B. neuwiedi and by Atroxlysin Ia from B. atrox venoms. In the present work, we demonstrated the potential use of plant cells to produce scFvBaP1 to be used in the future as a biotechnological alternative to horse immunization protocols to produce anti-venoms to be used in human therapy against snakebites.

Therapeutics and Immunoprophylaxis Against Noroviruses and Rotaviruses: The Past, Present, and Future

Background:

Noroviruses and rotaviruses are important viral etiologies of severe gastroenteritis. Noroviruses are the primary cause of nonbacterial diarrheal outbreaks in humans, whilst rotaviruses are a major cause of childhood diarrhea. Although both enteric pathogens substantially impact human health and economies, there are no approved drugs against noroviruses and rotaviruses so far. On the other hand, whilst the currently licensed rotavirus vaccines have been successfully implemented in over 100 countries, the most advanced norovirus vaccine has recently completed phase-I and II trials.

Methods:

We performed a structured search of bibliographic databases for peer-reviewed research litera-ture on advances in the fields of norovirus and rotavirus therapeutics and immunoprophylaxis.

Results:

Technological advances coupled with a proper understanding of viral morphology and replication over the past decade has facilitated pioneering research on therapeutics and immunoprophylaxis against noroviruses and rotaviruses, with promising outcomes in human clinical trials of some of the drugs and vaccines. This review focuses on the various developments in the fields of norovirus and rotavirus thera-peutics and immunoprophylaxis, such as potential antiviral drug molecules, passive immunotherapies (oral human immunoglobulins, egg yolk and bovine colostral antibodies, llama-derived nanobodies, and anti-bodies expressed in probiotics, plants, rice grains and insect larvae), immune system modulators, probiot-ics, phytochemicals and other biological substances such as bovine milk proteins, therapeutic nanoparti-cles, hydrogels and viscogens, conventional viral vaccines (live and inactivated whole virus vaccines), and genetically engineered viral vaccines (reassortant viral particles, virus-like particles (VLPs) and other sub-unit recombinant vaccines including multi-valent viral vaccines, edible plant vaccines, and encapsulated viral particles).

Conclusions:

This review provides important insights into the various approaches to therapeutics and im-munoprophylaxis against noroviruses and rotaviruses..

Production of complex viral glycoproteins in plants as vaccine immunogens

Plant molecular farming offers a cost-effective and scalable approach to the expression of recombinant proteins which has been proposed as an alternative to conventional production platforms for developing countries. In recent years, numerous proofs of concept have established that plants can produce biologically active recombinant proteins and immunologically relevant vaccine antigens that are comparable to those made in conventional expression systems. Driving many of these advances is the remarkable plasticity of the plant proteome which enables extensive engineering of the host cell, as well as the development of improved expression vectors facilitating higher levels of protein production. To date, the only plant-derived viral glycoprotein to be tested in humans is the influenza haemagglutinin which expresses at ~50 mg/kg. However, many other viral glycoproteins that have potential as vaccine immunogens only accumulate at low levels in planta. A critical consideration for the production of many of these proteins in heterologous expression systems is the complexity of post-translational modifications, such as control of folding, glycosylation and disulphide bridging, which is required to reproduce the native glycoprotein structure. In this review, we will address potential shortcomings of plant expression systems and discuss strategies to optimally exploit the technology for the production of immunologically relevant and structurally authentic glycoproteins for use as vaccine immunogens.

Oral immunization with rotavirus VP7-CTB fusion expressed in transgenic Arabidopsis thaliana induces antigen-specific IgA and IgG and passive protection in mice

Human rotavirus (HRV) is the primary cause of severe gastroenteritis in children. However, there is currently no protective virus for rotavirus available. In the present study, an HRVVP7-cholera toxin B subunit (CTB) fusion protein was expressed in Arabidopsis thaliana. To determine the adjuvant effect of HRVVP7-CTB, HRVVP7 without CTB was expressed in the same manner. HRVVP7-CTB accounted for 0.39% of the total soluble protein (TSP) in the transgenic seeds and 52.65 µg/g of HRVVP7 protein was expressed in these seeds. Mice were immunized with TSP from the transformed seeds and produced serum immunoglobulin G (IgG) and mucosal IgA specifically directed against HRVVP7. Antibody titers were highest in mice orally immunized with the plant-expressed HRVVP7-CTB protein, whereas HRVVP7-CTB-specific IgG neutralized the rotavirus. Suckling pups born from dams immunized with the HRVVP7-CTB fusion protein were protected against challenge with virulent rotavirus. The results of the present study suggest that the HRVVP7-CTB fusion protein produced in A. thaliana may be a rotaviral-specific candidate subunit vaccine.

The Last Ten Years of Advancements in Plant-Derived Recombinant Vaccines against Hepatitis B

Disease prevention through vaccination is considered to be the greatest contribution to public health over the past century. Every year more than 100 million children are vaccinated with the standard World Health Organization (WHO)-recommended vaccines including hepatitis B (HepB). HepB is the most serious type of liver infection caused by the hepatitis B virus (HBV), however, it can be prevented by currently available recombinant vaccine, which has an excellent record of safety and effectiveness. To date, recombinant vaccines are produced in many systems of bacteria, yeast, insect, and mammalian and plant cells. Among these platforms, the use of plant cells has received considerable attention in terms of intrinsic safety, scalability, and appropriate modification of target proteins. Research groups worldwide have attempted to develop more efficacious plant-derived vaccines for over 30 diseases, most frequently HepB and influenza. More inspiring, approximately 12 plant-made antigens have already been tested in clinical trials, with successful outcomes. In this study, the latest information from the last 10 years on plant-derived antigens, especially hepatitis B surface antigen, approaches are reviewed and breakthroughs regarding the weak points are also discussed.

Changing distribution of age, clinical severity, and genotypes of rotavirus gastroenteritis in hospitalized children after the introduction of vaccination: a single center study in Seoul between 2011 and 2014

Background

This study aimed to explore changes in clinical epidemiology and genotype distribution and their association among hospitalized children with rotavirus gastroenteritis after the introduction of vaccines.

Methods

Between November 2010 and October 2014, hospitalized children with acute gastroenteritis were enrolled. Rotavirus genotypes were confirmed through reverse transcription-polymerase chain reaction (RT-PCR), semi-nested PCR, and sequencing. Clinical information including vaccination status and the modified Vesikari scores were collected.

Results

Among 179 children with rotavirus infection, nineteen (10.6 %) were completely vaccinated. During the study period, the number of children between three and 23 months of age decreased significantly compared to the number of children older than 24 months of age (P = 0.010), who showed lower diarrhea severity (duration, P = 0.042; frequency, P = 0.021) but higher vomiting severity (P = 0.007, 0.036) compared to the former. Vaccination status was also significantly associated with lower vomiting severity after adjustment for age (frequency only, P = 0.018). The predominant genotypes were G2P[4] (18.4 %), G1P[8] (14.5 %), and G1P[4]P[8] (12.8 %), and the prevalence of genotypes with uncommon and mixed combinations was more than 50 %. Children infected with G2P[4] strains tended to be older (P = 0.005) and had more severe vomiting (P = 0.018, 0.006) than those with G1P[8].

Conclusions

Increase in age of infected, hospitalized children was accompanied by change in clinical severity during 2011–2014 after the introduction of vaccines in Seoul. Clinical severity was also associated with vaccination status and genotype. Long-term large scale studies are needed to document the significance of the increase in genotypes of uncommon and mixed combinations.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-1623-y) contains supplementary material, which is available to authorized users.