Induction of humoral and cell-mediated immune responses by hepatitis B virus epitope displayed on the virus-like particles of prawn nodavirus

Chimeric virus-like particles of nodavirus displaying M2e of human and avian influenza A viruses as a potential dual-use vaccine: Inducing a broader immune response and protecting mice against viral infections

The haemagglutinin (HA) and neuraminidase (NA) of influenza A viruses (IAVs) mutate rapidly, necessitating yearly updates to seasonal influenza vaccines. The highly conserved matrix 2 ectodomain protein (M2e) of IAVs presents a promising candidate for developing a universal influenza vaccine. However, variations in the M2e amino acid sequences, particularly in host-restriction specificity regions between human and avian IAVs, pose significant challenges. To broaden the M2e immunogenicity, we previously fused M2e from human and avian IAVs at the C-terminal end of Macrobrachium rosenbergii nodavirus capsid protein (NvC). The chimeric protein self-assembled into virus-like particles (VLPs), stimulating IgY antibodies and cell-mediated immune responses to human and avian M2e in chickens. In this study, we investigated the breadth and cross-subtype immunity of these chimeric VLPs in BALB/c mice to assess their potential for human use. The chimeric protein purified with immobilised metal affinity chromatography exhibited significant antigenicity to anti-H1N1 and anti-H9N2 M2e antibodies. Immunisation of BALB/c mice subcutaneously with the chimeric VLPs led to the development of anti-H1N1 and anti-H9N2 M2e-specific IgG antibodies that cross-reacted with M2e of H5N1 and H5N2 IAVs. The chimeric VLPs also elicited a strong cell-mediated immune response, characterised by a balanced Th1 and Th2 cytokine profile. Additionally, a significant increase in the CD8+/CD4+ cell ratio in splenocytes suggests enhanced cytotoxic T lymphocyte (CTL) activity. The chimeric VLPs, with or without adjuvant, conferred 100 % protection against challenges with four times median lethal dose (4xLD50) of mouse-adapted H1N1 and H3N2 IAVs, reducing morbidity, pathology, and viral load in their lungs. Collectively, our data showed that the chimeric VLPs that induce potent immunogenicity in chickens hold potential for human application as demonstrated in BALB/c mice study, where anti-IAV immunity was broadened, protecting the mice from H1N1 and H3N2 IAV infections.

A simple and high efficiency purification of His-tagged turnip yellow mosaic virus-like particle (TYMV-VLP) by nickel ion affinity precipitation

Virus-like particles (VLPs) is one of the most favourable subjects of study, especially in the field of nanobiotechnology and vaccine development because they possess good immunogenicity and self-adjuvant properties. Conventionally, VLPs can be tagged and purified using affinity chromatography or density gradient ultracentrifugation which is costly and time-consuming. Turnip yellow mosaic virus (TYMV) is a plant virus, where expression of the viral coat protein (TYMVc) in Escherichia coli (E. coli) has been shown to form VLP. In this study, we report a non-chromatographic method for VLP purification using C-terminally His-tagged TYMVc (TYMVcHis₆) as a protein model. Firstly, the TYMVcHis₆ was cloned and expressed in E. coli. Upon clarification of cell lysate, nickel (II) chloride [NiCl₂; 15µM or equivalent to 0.0000194% (w/v)] was added to precipitate TYMVcHis₆. Following centrifugation, the pellet was resuspended in buffer containing 1mM EDTA to chelate Ni²⁺, which is then removed via dialysis. A total of 50% of TYMVcHis₆ was successfully recovered with purity above 0.90. Later, the purified TYMVcHis₆ was analysed with sucrose density ultracentrifugation, dynamic light scattering (DLS), and transmission electron microscopy (TEM) to confirm VLP formation, which is comparable to TYMVcHis₆ purified using the standard immobilized metal affinity chromatography (IMAC) column. As the current method omitted the need for IMAC column and beads while significantly reducing the time needed for column washing, nickel affinity precipitation represents a novel method for the purification of VLPs displaying poly-histidine tags (His-tags).

Site-Specific Modification of Virus-Like Particles for Exogenous Tumor Antigen Display and Minimizing Preexisting Immunity

The widespread preexisting immunity against virus-like particles (VLPs) seriously limits the applications of VLPs as vaccine vectors. Enabling technology for exogenous antigen display should not only ensure the assembly ability of VLPs and site-specific modification, but also consider the effect of preexisting immunity on the behavior of VLPs in vivo. Here, combining genetic code expansion technique and synthetic biology strategy, a site-specific modification method for hepatitis B core (HBc) VLPs via incorporating azido-phenylalanine into the desired positions is described. Through modification position screening, it is found that HBc VLPs incorporated with azido-phenylalanine at the main immune region can effectively assemble and rapidly conjugate with the dibenzocycolctyne-modified tumor-associated antigens, mucin-1 (MUC1). The site-specific modification of HBc VLPs not only improves the immunogenicity of MUC1 antigens but also shields the immunogenicity of HBc VLPs themselves, thereby activating a strong and persistent anti-MUC1 immune response even in the presence of preexisting anti-HBc immunity, which results in the efficient tumor elimination in a lung metastatic mouse model. Together, these results demonstrate the site-specific modification strategy enabled HBc VLPs behave as a potent antitumor vaccine and this strategy to manipulate immunogenicity of VLPs may be suitable for other VLP-based vaccine vectors.

Virus-like Particles of Nodavirus Displaying the Receptor Binding Domain of SARS-CoV-2 Spike Protein: A Potential VLP-Based COVID-19 Vaccine

Since the outbreak of the coronavirus disease 2019 (COVID-19), various vaccines have been developed for emergency use. The efficacy of the initial vaccines based on the ancestral strain of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) has become a point of contention due to the emergence of new variants of concern (VOCs). Therefore, continuous innovation of new vaccines is required to target upcoming VOCs. The receptor binding domain (RBD) of the virus spike (S) glycoprotein has been extensively used in vaccine development due to its role in host cell attachment and penetration. In this study, the RBDs of the Beta (β) and Delta (δ) variants were fused to the truncated Macrobrachium rosenbergii nodavirus capsid protein without the protruding domain (CΔ116-MrNV-CP). Immunization of BALB/c mice with the virus-like particles (VLPs) self-assembled from the recombinant CP showed that, with AddaVax as an adjuvant, a significantly high level of humoral response was elicited. Specifically, mice injected with equimolar of adjuvanted CΔ116-MrNV-CP fused with the RBD of the β- and δ-variants increased T helper (Th) cell production with a CD8⁺/CD4⁺ ratio of 0.42. This formulation also induced proliferation of macrophages and lymphocytes. Overall, this study demonstrated that the nodavirus truncated CP fused with the SARS-CoV-2 RBD has potential to be developed as a VLP-based COVID-19 vaccine.

Yeast-Based Virus-like Particles as an Emerging Platform for Vaccine Development and Delivery

Virus-like particles (VLPs) are empty, nanoscale structures morphologically resembling viruses. Internal cavity, noninfectious, and particulate nature with a high density of repeating epitopes, make them an ideal platform for vaccine development and drug delivery. Commercial use of Gardasil-9 and Cervarix showed the usefulness of VLPs in vaccine formulation. Further, chimeric VLPs allow the raising of an immune response against different immunogens and thereby can help reduce the generation of medical or clinical waste. The economically viable production of VLPs significantly impacts their usage, application, and availability. To this end, several hosts have been used and tested. The present review will discuss VLPs produced using different yeasts as fermentation hosts. We also compile a list of studies highlighting the expression and purification of VLPs using a yeast-based platform. We also discuss the advantages of using yeast to generate VLPs over other available systems. Further, the issues or limitations of yeasts for producing VLPs are also summarized. The review also compiles a list of yeast-derived VLP-based vaccines that are presently in public use or in different phases of clinical trials.

Development of virus-like particles-based vaccines against coronaviruses

Severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus (MERS-CoV), and the current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are the most impactful coronaviruses in human history, especially the latter, which brings revolutionary changes to human vaccinology. Due to its high infectivity, the virus spreads rapidly throughout the world and was declared a pandemic in March 2020. A vaccine would normally take more than 10 years to be developed. As such, there is no vaccine available for SARS-CoV and MERS-CoV. Currently, 10 vaccines have been approved for emergency use by World Health Organization (WHO) against SARS-CoV-2. Virus-like particle (VLP)s are nanoparticles resembling the native virus but devoid of the viral genome. Due to their self-adjuvanting properties, VLPs have been explored extensively for vaccine development. However, none of the approved vaccines against SARS-CoV-2 was based on VLP and only 4% of the vaccine candidates in clinical trials were based on VLPs. In the current review, we focused on discussing the major advances in the development of VLP-based vaccine candidates against the SARS-CoV, MERS-CoV, and SARS-CoV-2, including those in clinical and pre-clinical studies, to give a comprehensive overview of the VLP-based vaccines against the coronaviruses.

Bio-nanogate manipulation on electrode surface as an electrochemical immunosensing strategy for detecting anti-hepatitis B surface antigen

The diagnosis of hepatitis B virus (HBV) and monitoring of the vaccination efficiency against HBV require real-time analysis. The presence of antibody against hepatitis B virus surface antigen (anti-HBsAg) as a result of HBV infection and/or immunization may indicate individual immune status towards HBV. This study investigated the ability of a bio-nanogate-based displacement immunosensing strategy in detecting anti-HBsAg antibody, via nonspecific-binding between polyamidoamine dendrimers encapsulated gold nanoparticles (PAMAM-Au) and the 'antigenic determinant' region (aD) of HBsAg. For this purpose, maltose binding protein harbouring the aD region (MBP-aD) was synthesized as a bioreceptor and immobilized on the screen-printed carbon electrode (SPCE). Following that, PAMAM-Au was deposited on MBP-aD, forming the 'gate' and was used as a monitoring agent. Under optimal conditions, the high specificity of anti-HBsAg antibody towards MBP-aD displaced PAMAM-Au causing the decrement of anodic peak in differential pulse voltammetry (DPV) analysis. The signal changes were proportionally related to the concentration of anti-HBsAg antibody, in a range of 1 - 1000 mIU/mL with a limit of detection (LOD) of 2.5 mIU/mL. The results also showed high specificity and selectivity of the immunosensor platform in detecting anti-HBsAg antibody both in spiked buffer and human serum samples.

Immunological Analysis of Nodavirus Capsid Displaying the Domain III of Japanese Encephalitis Virus Envelope Protein

Japanese encephalitis virus (JEV) is the pathogen that causes Japanese encephalitis (JE) in humans and horses. Lethality of the virus was reported to be between 20–30%, of which, 30–50% of the JE survivors develop neurological and psychiatric sequelae. Attributed to the low effectiveness of current therapeutic approaches against JEV, vaccination remains the only effective approach to prevent the viral infection. Currently, live-attenuated and chimeric-live vaccines are widely used worldwide but these vaccines pose a risk of virulence restoration. Therefore, continuing development of JE vaccines with higher safety profiles and better protective efficacies is urgently needed. In this study, the Macrobrachium rosenbergii nodavirus (MrNV) capsid protein (CP) fused with the domain III of JEV envelope protein (JEV-DIII) was produced in Escherichia coli. The fusion protein (MrNV-CP^JEV-DIII) assembled into virus-like particles (VLPs) with a diameter of approximately 18 nm. The BALB/c mice injected with the VLPs alone or in the presence of alum successfully elicited the production of anti-JEV-DIII antibody, with titers significantly higher than that in mice immunized with IMOJEV, a commercially available vaccine. Immunophenotyping showed that the MrNV-CP^JEV-DIII supplemented with alum triggered proliferation of cytotoxic T-lymphocytes, macrophages, and natural killer (NK) cells. Additionally, cytokine profiles of the immunized mice revealed activities of cytotoxic T-lymphocytes, macrophages, and NK cells, indicating the activation of adaptive cellular and innate immune responses mediated by MrNV-CP^JEV-DIII VLPs. Induction of innate, humoral, and cellular immune responses by the MrNV-CP^JEV-DIII VLPs suggest that the chimeric protein is a promising JEV vaccine candidate.

Advances in Nanoparticle Drug Delivery Systems for Anti-Hepatitis B Virus Therapy: A Narrative Review

Chronic hepatitis B (CHB) is an infectious viral disease that is prevalent worldwide. Traditional nucleoside analogues, as well as the novel drug targets against hepatitis B virus (HBV), are associated with certain critical factors that influence the curative effect, such as biological stability and safety, effective drug delivery, and controlled release. Nanoparticle drug delivery systems have significant advantages and have provided a basis for the development of anti-HBV strategies. In this review, we aim to review the advances in nanoparticle drug delivery systems for anti-hepatitis B virus therapy by summarizing the relevant literature. First, we focus on the characteristics of nanoparticle drug delivery systems for anti-HBV therapy. Second, we discuss the nanoparticle delivery systems for anti-HBV nucleoside drugs, gene-based drugs, and vaccines. Lastly, we provide an overview of the prospects for nanoparticle-based anti-HBV agents.

Chimeric virus-like particles (VLPs) designed from shrimp nodavirus (MrNV) capsid protein specifically target EGFR-positive human colorectal cancer cells

Recombinant MrNV capsid protein has been shown to effectively deliver plasmid DNA and dsRNA into Sf9 insect cells and shrimp tissues. To extend its application to cancer cell-targeting drug delivery, we created three different types of chimeric MrNV virus-like particles (VLPs) (R-MrNV, I-MrNV, and E-MrNV) that have specificity toward the epidermal growth factor receptor (EGFR), a cancer cell biomarker, by incorporating the EGFR-specific GE11 peptide at 3 different locations within the host cell recognition site of the capsid. All three chimeric MrNV-VLPs preserved the ability to form a mulberry-like VLP structure and to encapsulate EGFP DNA plasmid with an efficiency comparable to that previously reported for normal MrNV (N-MrNV). Compared to N-MrNV, the chimeric R-MrNV and E-MrNV carrying the exposed GE-11 peptide showed a significantly enhanced binding and internalization abilities that were specific towards EGFR expression in colorectal cancer cells (SW480). Specific targeting of chimeric MrNV to EGFR was proven by both EGFR silencing with siRNA vector and a competition with excess GE-11 peptide as well as the use of EGFR-negative colorectal cells (SW620) and breast cancer cells (MCF7). We demonstrated here that both chimeric R-MrNV and E-MrNV could be used to encapsulate cargo such as exogenous DNA and deliver it specifically to EGFR-positive cells. Our study presents the potential use of surface-modified VLPs of shrimp virus origin as nanocontainers for targeted cancer drug delivery.

Regulation of Proteolytic Activity to Improve the Recovery of Macrobrachium rosenbergii Nodavirus Capsid Protein

The causative agent of white tail disease (WTD) in the giant freshwater prawn is Macrobrachium rosenbergii nodavirus (MrNV). The recombinant capsid protein (CP) of MrNV was previously expressed in Escherichia coli, and it self-assembled into icosahedral virus-like particles (VLPs) with a diameter of approximately 30 nm. Extensive studies on the MrNV CP VLPs have attracted widespread attention in their potential applications as biological nano-containers for targeted drug delivery and antigen display scaffolds for vaccine developments. Despite their advantageous features, the recombinant MrNV CP VLPs produced in E. coli are seriously affected by protease degradations, which significantly affect the yield and stability of the VLPs. Therefore, the aim of this study is to enhance the stability of MrNV CP by modulating the protease degradation activity. Edman degradation amino acid sequencing revealed that the proteolytic cleavage occurred at arginine 26 of the MrNV CP. The potential proteases responsible for the degradation were predicted in silico using the Peptidecutter, Expasy. To circumvent proteolysis, specific protease inhibitors (PMSF, AEBSF and E-64) were tested to reduce the degradation rates. Modulation of proteolytic activity demonstrated that a cysteine protease was responsible for the MrNV CP degradation. The addition of E-64, a cysteine protease inhibitor, remarkably improved the yield of MrNV CP by 2.3-fold compared to the control. This innovative approach generates an economical method to improve the scalability of MrNV CP VLPs using individual protease inhibitors, enabling the protein to retain their structural integrity and stability for prominent downstream applications including drug delivery and vaccine development.

Chimeric Virus-Like Particles of Prawn Nodavirus Displaying Hepatitis B Virus Immunodominant Region: Biophysical Properties and Cytokine Response

Hepatitis B is a major global health challenge. In the absence of an effective treatment for the disease, hepatitis B vaccines provide protection against the viral infection. However, some individuals do not have positive immune responses after being vaccinated with the hepatitis B vaccines available in the market. Thus, it is important to develop a more protective vaccine. Previously, we showed that hepatitis B virus (HBV) ‘a’ determinant (aD) displayed on the prawn nodavirus capsid (Nc) and expressed in Spodoptera frugiperda (Sf9) cells (namely, Nc-aD-Sf9) self-assembled into virus-like particles (VLPs). Immunisation of BALB/c mice with the Nc-aD-Sf9 VLPs showed significant induction of humoral, cellular and memory B-cell immunity. In the present study, the biophysical properties of the Nc-aD-Sf9 VLPs were studied using dynamic light scattering (DLS) and circular dichroism (CD) spectroscopy. Enzyme-linked immunosorbent assay (ELISA) was used to determine the antigenicity of the Nc-aD-Sf9 VLPs, and multiplex ELISA was employed to quantify the cytokine response induced by the VLPs administered intramuscularly into BALB/c mice (n = 8). CD spectroscopy of Nc-aD-Sf9 VLPs showed that the secondary structure of the VLPs predominantly consisted of beta (β)-sheets (44.8%), and they were thermally stable up to ~52 °C. ELISA revealed that the aD epitope of the VLPs was significantly antigenic to anti-HBV surface antigen (HBsAg) antibodies. In addition, multiplex ELISA of serum samples from the vaccinated mice showed a significant induction (p < 0.001) of IFN-γ, IL-4, IL-5, IL-6, IL-10, and IL-12p70. This cytokine profile is indicative of natural killer cell, macrophage, dendritic cell and cytotoxic T-lymphocyte activities, which suggests a prophylactic innate and adaptive cellular immune response mediated by Nc-aD-Sf9 VLPs. Interestingly, Nc-aD-Sf9 induced a more robust release of the aforementioned cytokines than that of Nc-aD VLPs produced in Escherichia coli and a commercially used hepatitis B vaccine. Overall, Nc-aD-Sf9 VLPs are thermally stable and significantly antigenic, demonstrating their potential as an HBV vaccine candidate.

Immunological Analysis of the Hepatitis B Virus "a" Determinant Displayed on Chimeric Virus-Like Particles of Macrobrachium rosenbergii Nodavirus Capsid Protein Produced in Sf9 Cells

Chimeric virus-like particles (VLPs) have been widely exploited for various purposes including their use as vaccine candidates, particularly due to their ability to induce stronger immune responses than VLPs consisting of single viral proteins. In the present study, VLPs of the Macrobrachium rosenbergii nodavirus (MrNV) capsid protein (Nc) displaying the hepatitis B virus “a” determinant (aD) were produced in Spodoptera frugiperda (Sf9) insect cells. BALB/c mice immunised with the purified chimeric Nc-aD VLPs elicited a sustained titre of anti-aD antibody, which was significantly higher than that elicited by a commercially available hepatitis B vaccine and Escherichia coli-produced Nc-aD VLPs. Immunophenotyping showed that the Sf9-produced Nc-aD VLPs induced proliferation of cytotoxic T-lymphocytes and NK1.1 natural killer cells. Furthermore, enzyme-linked immunospot (ELISPOT)analysis showed the presence of antibody-secreting memory B cells in the mice splenocytes stimulated with the synthetic aD peptide. The significant humoral, natural killer cell and memory B cell immune responses induced by the Sf9-produced Nc-aD VLPs suggest that they present good prospects for use as a hepatitis B vaccine candidate.

Recent Progress on the Versatility of Virus-Like Particles

Virus-like particles (VLPs) are multimeric nanostructures composed of one or more structural proteins of a virus in the absence of genetic material. Having similar morphology to natural viruses but lacking any pathogenicity or infectivity, VLPs have gradually become a safe substitute for inactivated or attenuated vaccines. VLPs can achieve tissue-specific targeting and complete and effective cell penetration. With highly ordered epitope repeats, VLPs have excellent immunogenicity and can induce strong cellular and humoral immune responses. In addition, as a type of nanocarrier, VLPs can be used to display antigenic epitopes or deliver small molecules. VLPs have thus become powerful tools for vaccinology and biomedical research. This review highlights the versatility of VLPs in antigen presentation, drug delivery, and vaccine technology.

Interaction study of peptide-PAMAM as potential bio-nanogate for detecting anti-hepatitis B surface antigen

Bio-nanogate involves synthesized or natural molecules as a 'gate' towards bioreceptors and responds upon the presence of targeted analytes in nanoscale dimension. Development of bio-nanogate improves analyte selectivity and signal response across various types of biosensors. The versatility of PAMAM dendrimers to form conjugates with guest molecules, such as proteins can be utilized in forming a bio-nanogate. PAMAM interaction with peptide bioreceptor for antibody detection is of interest in this study. This study investigated the interaction of synthesized immunogenic 'a' determinant (aD) region of hepatitis B virus surface antigen (HBsAg) with PAMAM G4 and anti-HBsAg antibody, as a potential bio-nanogate for anti-HBsAg detection. The aD peptide fused with maltose binding protein (MBP), was confirmed with Western blotting. Nano-Differential Scanning Fluorimetry (nano-DSF) study revealed that the interaction of MBP-aD with anti-HBsAg indicated a higher thermal stability as compared to its interaction with PAMAM G4. Electrochemical impedance spectroscopy showed that a higher binding constant of MBP-aD interaction with anti-HBsAg (0.92 μM^-1) was observed at maximum saturation, as compared with PAMAM G4 (0.07 μM^-1). Thermodynamic parameters demonstrated that MBP-aD interacted with anti-HBsAg and PAMAM G4, through van der Waals and hydrogen bonding. These analyses suggest that the weak interaction of MBP-aD and PAMAM G4 may form a potential bio-nanogate. It is hypothesized that the presence of anti-HBsAg has a higher affinity towards MBP-aD which may displace PAMAM G4 in the anti-HBsAg detection system. This interaction study is crucial as an initial platform of using peptide-PAMAM as a bio-nanogate in an antibody detection system.

Recent Advances in the Vaccine Development Against Middle East Respiratory Syndrome-Coronavirus

Middle East respiratory syndrome (MERS) is a deadly viral respiratory disease caused by MERS-coronavirus (MERS-CoV) infection. To date, there is no specific treatment proven effective against this viral disease. In addition, no vaccine has been licensed to prevent MERS-CoV infection thus far. Therefore, our current review focuses on the most recent studies in search of an effective MERS vaccine. Overall, vaccine candidates against MERS-CoV are mainly based upon the viral spike (S) protein, due to its vital role in the viral infectivity, although several studies focused on other viral proteins such as the nucleocapsid (N) protein, envelope (E) protein, and non-structural protein 16 (NSP16) have also been reported. In general, the potential vaccine candidates can be classified into six types: viral vector-based vaccine, DNA vaccine, subunit vaccine, nanoparticle-based vaccine, inactivated-whole virus vaccine and live-attenuated vaccine, which are discussed in detail. Besides, the immune responses and potential antibody dependent enhancement of MERS-CoV infection are extensively reviewed. In addition, animal models used to study MERS-CoV and evaluate the vaccine candidates are discussed intensively.

Thermally-responsive Virus-like Particle for Targeted Delivery of Cancer Drug

Multifunctional nanocarriers displaying specific ligands and simultaneously response to stimuli offer great potentials for targeted and controlled drug delivery. Several synthetic thermally-responsive nanocarriers have been studied extensively for hyperthermia incorporated chemotherapy. However, no information is available on the application of virus-like particle (VLP) in thermally-controlled drug delivery systems. Here, we describe the development of a novel multifunctional nanovehicle based on the VLP of Macrobrachium rosenbergii nodavirus (MrNVLP). Folic acid (FA) was covalently conjugated to lysine residues located on the surface of MrNVLP, while doxorubicin (Dox) was loaded inside the VLP using an infusion method. This thermally-responsive nanovehicle, namely FA-MrNVLP-Dox, released Dox in a sustained manner and the rate of drug release increased in response to a hyperthermia temperature at 43 °C. The FA-MrNVLP-Dox enhanced the delivery of Dox to HT29 cancer cells expressing high level of folate receptor (FR) as compared to CCD841CoN normal cells and HepG2 cancer cells, which express low levels of FR. As a result, FA-MrNVLP-Dox increased the cytotoxicity of Dox on HT29 cells, and decreased the drug's cytotoxicity on CCD841CoN and HepG2 cells. This study demonstrated the potential of FA-MrNVLP-Dox as a thermally-responsive nanovehicle for targeted delivery of Dox to cancer cells rich in FR.

Oral vaccination of Macrobrachium rosenbergii with baculovirus-expressed M. rosenbergii nodavirus (MrNV) capsid protein induces protective immunity against MrNV challenge

White Tail Disease (WTD) is one of the important viral diseases of fresh water giant prawn Macrobrachium rosenbergii, which is caused by Macrobrachium rosenbergii nodavirus (MrNV). In the present study, the capsid protein gene of MrNV containing a His-tag was cloned into a baculovirus vector pVL1393 and expressed the recombinant MrNV protein in insect cells, using a baculovirus expression system. A band corresponding to the MrNV protein of 43 kDa was characterized after fractionating the proteins of baculovirus-infected cell lysates by SDS-polyacrylamide gel, and immunostaining with His-tag monoclonal antibody. Furthermore, purified MrNV capsid protein assembled into virus-like particles (VLPs) of ∼30 nm in diameter, when examined by transmission electron microscopy (TEM). To vaccinate the larvae by oral route, the recombinant MrNV (r-MrNV) protein was coated with artificial prawn feed and fed to M. rosenbergii larvae (90 ± 10 mg) for 60 days. After 30 and 60 days of vaccine treatment, group of prawns were challenged with virulent MrNV orally. Samples were collected at different time intervals to evaluate the survival of larvae and to analyze the presence of MrNV by double-step PCR and expression of immune/ toll-like receptor (TLR) genes. Non-vaccinated group of M. rosenbergii larvae succumbed to death and had 90% mortality, whereas the r-MrNV protein treated groups exhibited 65 and 80% survival (P  ≤  0.001) for 30 and 60 days post-vaccination (dpv), respectively. Double-step PCR diagnosis revealed that there was 100% positive signals observed in non-vaccinated prawn group, whereas the infection was reduced significantly (P < 0.001) to 32 and 17% respectively in 30 and 60 dpv. Among the four different immune/ TLR genes such as antimicrobial peptide (Mramp), lysozyme (MrLY), proPhenol Oxidase (MrPPO) and Toll-Like Receptor (MrToll) expression screening, Mramp was successfully expressed in the MrNV subunit protein vaccinated prawns, whereas the non-vaccinated prawn had no immune/TLR gene expression. Taken together, our results demonstrate that oral vaccination of M. rosenbergii larvae with baculovirus-expressed MrNV capsid protein confer up to 78% protection against MrNV infection.

Structure of the Macrobrachium rosenbergii nodavirus: A new genus within the Nodaviridae?

Macrobrachium rosenbergii nodavirus (MrNV) is a pathogen of freshwater prawns that poses a threat to food security and causes significant economic losses in the aquaculture industries of many developing nations. A detailed understanding of the MrNV virion structure will inform the development of strategies to control outbreaks. The MrNV capsid has also been engineered to display heterologous antigens, and thus knowledge of its atomic resolution structure will benefit efforts to develop tools based on this platform. Here, we present an atomic-resolution model of the MrNV capsid protein (CP), calculated by cryogenic electron microscopy (cryoEM) of MrNV virus-like particles (VLPs) produced in insect cells, and three-dimensional (3D) image reconstruction at 3.3 Å resolution. CryoEM of MrNV virions purified from infected freshwater prawn post-larvae yielded a 6.6 Å resolution structure, confirming the biological relevance of the VLP structure. Our data revealed that unlike other known nodavirus structures, which have been shown to assemble capsids having trimeric spikes, MrNV assembles a T = 3 capsid with dimeric spikes. We also found a number of surprising similarities between the MrNV capsid structure and that of the Tombusviridae: 1) an extensive network of N-terminal arms (NTAs) lines the capsid interior, forming long-range interactions to lace together asymmetric units; 2) the capsid shell is stabilised by 3 pairs of Ca2+ ions in each asymmetric unit; 3) the protruding spike domain exhibits a very similar fold to that seen in the spikes of the tombusviruses. These structural similarities raise questions concerning the taxonomic classification of MrNV.

Peptide inhibitors of Macrobrachium rosenbergii nodavirus

Macrobrachium rosenbergii nodavirus (MrNv) causes white tail disease (WTD) in giant freshwater prawns, which leads to devastating economic losses in the aquaculture industry. Despite extensive research on MrNv, there is still no antiviral agent to treat WTD. Thus, the main aim of this study was to identify potential anti-MrNv molecules. A 12-mer phage-displayed peptide library was biopanned against the MrNv virus-like particle (VLP). After four rounds of biopanning, two dominant phages harbouring the amino acid sequences HTKQIPRHIYSA and VSRHQSWHPHDL were selected. An equilibrium binding assay in solution was performed to determine the relative dissociation constant (KDrel) of the interaction between the MrNv VLP and the selected fusion phages. Phage-HTKQIPRHIYSA has a KDrel value of 92.4±22.8 nM, and phage-VSRHQSWHPHDL has a KDrel value of 12.7±3.8 nM. An in-cell elisa was used to determine the inhibitory effect of the synthetic peptides towards the entry of MrNv VLP into Spodoptera frugiperda (Sf9) cells. Peptides HTKQIPRHIYSA and VSRHQSWHPHDL inhibited the entry of the MrNv VLP into Sf9 cells with IC50 values of 30.4±3.6 and 26.5±8.8 µM, respectively. Combination of both peptides showed a significantly higher inhibitory effect with an IC50 of 4.9±0.4 µM. An MTT assay revealed that the viability of MrNv-infected cells increased to about 97 % in the presence of both peptides. A real-time RT-PCR assay showed that simultaneous application of both peptides significantly reduced the number of MrNv per infected cell, from 97±9 to 11±4. These peptides are lead compounds which can be further developed into potent anti-MrNv agents.

Virus like particles as a platform for cancer vaccine development

Cancers have killed millions of people in human history and are still posing a serious health problem worldwide. Therefore, there is an urgent need for developing preventive and therapeutic cancer vaccines. Among various cancer vaccine development platforms, virus-like particles (VLPs) offer several advantages. VLPs are multimeric nanostructures with morphology resembling that of native viruses and are mainly composed of surface structural proteins of viruses but are devoid of viral genetic materials rendering them neither infective nor replicative. In addition, they can be engineered to display multiple, highly ordered heterologous epitopes or peptides in order to optimize the antigenicity and immunogenicity of the displayed entities. Like native viruses, specific epitopes displayed on VLPs can be taken up, processed, and presented by antigen-presenting cells to elicit potent specific humoral and cell-mediated immune responses. Several studies also indicated that VLPs could overcome the immunosuppressive state of the tumor microenvironment and break self-tolerance to elicit strong cytotoxic lymphocyte activity, which is crucial for both virus clearance and destruction of cancerous cells. Collectively, these unique characteristics of VLPs make them optimal cancer vaccine candidates. This review discusses current progress in the development of VLP-based cancer vaccines and some potential drawbacks of VLPs in cancer vaccine development. Extracellular vesicles with close resembling to viral particles are also discussed and compared with VLPs as a platform in cancer vaccine developments.

Advances in the study of nodavirus

Nodaviruses are small bipartite RNA viruses which belong to the family of Nodaviridae. They are categorized into alpha-nodavirus, which infects insects, and beta-nodavirus, which infects fishes. Another distinct group of nodavirus infects shrimps and prawns, which has been proposed to be categorized as gamma-nodavirus. Our current review focuses mainly on recent studies performed on nodaviruses. Nodavirus can be transmitted vertically and horizontally. Recent outbreaks have been reported in China, Indonesia, Singapore and India, affecting the aquaculture industry. It also decreased mullet stock in the Caspian Sea. Histopathology and transmission electron microscopy (TEM) are used to examine the presence of nodaviruses in infected fishes and prawns. For classification, virus isolation followed by nucleotide sequencing are required. In contrast to partial sequence identification, profiling the whole transcriptome using next generation sequencing (NGS) offers a more comprehensive comparison and characterization of the virus. For rapid diagnosis of nodavirus, assays targeting the viral RNA based on reverse-transcription PCR (RT-PCR) such as microfluidic chips, reverse-transcription loop-mediated isothermal amplification (RT-LAMP) and RT-LAMP coupled with lateral flow dipstick (RT-LAMP-LFD) have been developed. Besides viral RNA detections, diagnosis based on immunological assays such as enzyme-linked immunosorbent assay (ELISA), immunodot and Western blotting have also been reported. In addition, immune responses of fish and prawn are also discussed. Overall, in fish, innate immunity, cellular type I interferon immunity and humoral immunity cooperatively prevent nodavirus infections, whereas prawns and shrimps adopt different immune mechanisms against nodavirus infections, through upregulation of superoxide anion, prophenoloxidase, superoxide dismutase (SOD), crustin, peroxinectin, anti-lipopolysaccharides and heat shock proteins (HSP). Potential vaccines for fishes and prawns based on inactivated viruses, recombinant proteins or DNA, either delivered through injection, oral feeding or immersion, are also discussed in detail. Lastly, a comprehensive review on nodavirus virus-like particles (VLPs) is presented. In recent years, studies on prawn nodavirus are mainly focused on Macrobrachium rosenbergii nodavirus (MrNV). Recombinant MrNV VLPs have been produced in prokaryotic and eukaryotic expression systems. Their roles as a nucleic acid delivery vehicle, a platform for vaccine development, a molecular tool for mechanism study and in solving the structures of MrNV are intensively discussed.

Cryo-Electron Microscopy Structure of the Macrobrachium rosenbergii Nodavirus Capsid at 7 Angstroms Resolution

White tail disease in the giant freshwater prawn Macrobrachium rosenbergii causes significant economic losses in shrimp farms and hatcheries and poses a threat to food-security in many developing countries. Outbreaks of Macrobrachium rosenbergii nodavirus (MrNV), the causative agent of white tail disease (WTD) are associated with up to 100% mortality rates. There are no interventions available to treat or prevent MrNV disease however. Here we show the structure of MrNV virus-like particles (VLPs) produced by recombinant expression of the capsid protein, using cryogenic electron microscopy. Our data show that MrNV VLPs package nucleic acids in a manner reminiscent of other known nodavirus structures. The structure of the capsid however shows striking differences from insect and fish infecting nodaviruses, which have been shown to assemble trimer-clustered T = 3 icosahedral virus particles. MrNV particles have pronounced dimeric blade-shaped spikes extending up to 6 nm from the outer surface of the capsid shell. Our structural analysis supports the assertion that MrNV may belong to a new genus of the Nodaviridae. Moreover, our study provides the first structural view of an important pathogen affecting aquaculture industries across the world.

Tracking the virus-like particles of Macrobrachium rosenbergii nodavirus in insect cells

Macrobrachium rosenbergii nodavirus (MrNv) poses a major threat to the prawn industry. Currently, no effective vaccine and treatment are available to prevent the spread of MrNv. Its infection mechanism and localisation in a host cell are also not well characterised. The MrNv capsid protein (MrNvc) produced in Escherichia coli self-assembled into virus-like particles (VLPs) resembling the native virus. Thus, fluorescein labelled MrNvc VLPs were employed as a model to study the virus entry and localisation in Spodoptera frugiperda, Sf9 cells. Through fluorescence microscopy and sub-cellular fractionation, the MrNvc was shown to enter Sf9 cells, and eventually arrived at the nucleus. The presence of MrNvc within the cytoplasm and nucleus of Sf9 cells was further confirmed by the Z-stack imaging. The presence of ammonium chloride (NH₄Cl), genistein, methyl-β-cyclodextrin or chlorpromazine (CPZ) inhibited the entry of MrNvc into Sf9 cells, but cytochalasin D did not inhibit this process. This suggests that the internalisation of MrNvc VLPs is facilitated by caveolae- and clathrin-mediated endocytosis. The whole internalisation process of MrNvc VLPs into a Sf9 cell was recorded with live cell imaging. We have also identified a potential nuclear localisation signal (NLS) of MrNvc through deletion mutagenesis and verified by classical-NLS mapping. Overall, this study provides an insight into the journey of MrNvc VLPs in insect cells.

Virus-like particle of Macrobrachium rosenbergii nodavirus produced in Spodoptera frugiperda (Sf9) cells is distinctive from that produced in Escherichia coli

Macrobrachium rosenbergii nodavirus (MrNV) is a virus native to giant freshwater prawn. Recombinant MrNV capsid protein has been produced in Escherichia coli, which self-assembled into virus-like particles (VLPs). However, this recombinant protein is unstable, degrading and forming heterogenous VLPs. In this study, MrNV capsid protein was produced in insect Spodoptera frugiperda (Sf9) cells through a baculovirus system. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) revealed that the recombinant protein produced by the insect cells self-assembled into highly stable, homogenous VLPs each of approximately 40 nm in diameter. Enzyme-linked immunosorbent assay (ELISA) showed that the VLPs produced in Sf9 cells were highly antigenic and comparable to those produced in E. coli. In addition, the Sf9 produced VLPs were highly stable across a wide pH range (2-12). Interestingly, the Sf9 produced VLPs contained DNA of approximately 48 kilo base pairs and RNA molecules. This study is the first report on the production and characterization of MrNV VLPs produced in a eukaryotic system. The MrNV VLPs produced in Sf9 cells were about 10 nm bigger and had a uniform morphology compared with the VLPs produced in E. coli. The insect cell production system provides a good source of MrNV VLPs for structural and immunological studies as well as for host-pathogen interaction studies. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 33:549-557, 2017.