Drosophila X virus-like particles as delivery carriers for improved oral insecticidal efficacy of scorpion Androctonus australis peptide against the invasive fruit fly,Drosophila suzukii

Insect-specific neurotoxic peptides derived from the venoms of scorpions and spiders can cause acute paralysis and death when injected into insects,offering a promising insecticidal component for insect pest control.However,effective delivery systems are required to help neurotoxic peptides pass through the gut barrier into the hemolymph,where they can act.Here,we investigated the potential of a novel nanocarrier,Drosophila X virus-like particle(DXV-VLP),for delivering a neurotoxin from the scorpion Androctonus australis Hector(AaIT)against the invasive pest fruit fly,Drosophila suzuki.Our results show that the fusion proteins of DXV polyproteins with AalT peptide at their Ctermini could be sufficiently produced in Lepidoptera Hi5 cells in a soluble form using the recombinant baculovirus expression system,and could self-assemble into VLPs with similar particle morphology and size to authentic DXV virions.In addition,the AalT peptides displayed on DXV-VLPs retained their toxicity,as demonstrated in injection bioassays that resulted in severe mortality(72%)in adults after 72 h.When fed to adults,mild mortality was observed in the group treated with DXV-AalT(38%),while no mortality occurred in the group treated with AaIT peptide,thus indicating the significant role of DXV-VLPs in delivering AalT peptides.Overall,this proof-of-concept study demonstrates for the first time that VLPs can be exploited to enhance oral delivery of insect-specific neurotoxic peptides in the context of pest control.Moreover,it provides insights for further improvements and potentially the development of neurotoxin-based bioinsecticides and/or transgenic crops for insect pest control.

Production of CCHF Virus-Like Particle by a Baculovirus-Insect Cell Expression System

Crimean-Congo Haemorrhagic Fever Virus (CCHFV) is a tick-born virus of the Nairovirus genus within the Bunyaviridae family,which is widespread and causes high fatality.The nucleocapsid of CCHFV is comprised of N proteins that are encoded by the S segment.In this research,the N protein of CCHFV was expressed in insect cells using a recombinant baculovirus.Under an electron microscope,Virus-Like Particles (VLPs) with various size and morphology were observed in cytoplasmic vesicles in the infected cells.Sucrose-gradient purification of the cell lysate indicated that the VLPs were mainly located in the upper fraction after ultracentrifugation,which was confirmed by Western blot analysis and immuno-electron microscopy (IEM).

The truncated form of fagellin (tFlic) provides the 2dCap subunit vaccine with better immunogenicity and protective efects in mice

Porcine circovirus type 2(PCV2)is the main causative agent of porcine circovirus-associated diseases,and it causes substantial economic losses in the swine industry each year.It is crucial to develop an efective vaccine against the circulating strain PCV2d,which is prone to substantial degrees of mutation.In this study,a truncated form of fagellin(tFlic:85-111 aa)was inserted into the C-terminal sequence of 2dCap,and Western blotting results showed that recombinant Cap-tFlic VLPs were successfully expressed.Transmission electron microscopy(TEM)and dynamic light scattering(DLS)data indicated that purifed recombinant Cap-tFlic fusion proteins existed in the form of polymers and that tFlic could not afect the formation and internalization of VLPs.Integrated Cap-tFlic VLPs induced the expression of antigen presentation-related factors(MHC-II and CD86)by bone marrow-derived dendritic cells(BM-DCs),and the expression of TLR5-related factors(TNF-α)was dramatically elevated.Mice intramuscularly immunized with Cap-tFlic VLPs exhibited signifcantly higher levels of Cap-specifc antibodies and neutralizing antibodies than mice immunized with wild-type Cap VLPs.The data obtained in the current study indicate that Cap-tFlic may be a candidate for a subunit vaccine against PCV2 in the future.

Generation of Hepatitis B virus PreS2-S antigen in Hansenula polymorpha

Despite the long availability of a traditional prophylactic vaccine containing the HBV surface antigen(HBsA g) and aluminum adjuvant, nearly 10% of the population remains unable to generate an effective immune response. Previous studies have indicated that hepatitis B virus(HBV) PreS 2-S is abundant in T/B cell epitopes, which induces a stronger immune response than HBsA g, particularly in terms of cytotoxic T lymphocyte(CTL) reaction. In the current study, the HBV PreS 2-S gene encoding an extra26 amino acids(PreS 2 C-terminus) located at the N-terminus of HBsA g was cloned into the pV CH1300 expression vector. Pre S2-S expressed in the methylotrophic yeast, Hansenula polymorpha, was produced at a yield of up to 250 mg/L. Subsequent purification steps involved hydrophobic adsorption to colloidal silica, ion-exchange chromatography and density ultracentrifugation. The final product was obtained with a total yield of ~15% and purity of ~99%. In keeping with previous studies, ~22 nm viruslike particles were detected using electron microscopy. The generated PreS 2-S antigen will be further studied for efficacy and safty in animals.

Viral and nonviral nanocarriers for in vivo CRISPR-based gene editing

The continued development of clustered regularly interspaced short palindromic repeats(CRISPR)technology has the potential to greatly impact clinical medicine,particularly for disease diagnosis and treatment.Despite high demand for the in vivo delivery of CRISPR-based therapies,significant challenges persist.These include rapid degradation by enzymes,inefficient disease site targeting,and the risk of undesired off-target outcomes.Nanoparticulate platforms,with their tailorable properties,have been engineered to efficiently package CRISPR payloads in various formats,including as plasmid DNA,mRNA,and ribonucleoprotein complexes,for in vivo delivery.Among them,recombinant adeno-associated viruses,virus-like particles,and lipid nanoparticles have displayed exceptional promise.This review will discuss the development of these and other nanocarriers for in vivo CRISPR-based genome editing.

Monoclonal neutralizing antibodies against EV71 screened from mice immunized with yeast-produced virus-like particles

Periodic outbreaks of hand, foot and mouth disease(HFMD) occur in children under 5 years old, and can cause death in some cases. The C4 strain of enterovirus 71(EV71) is the main pathogen that causes HFMD in China. Although no drugs against EV71 are available, some studies have shown that candidate vaccines or viral capsid proteins can produce anti-EV71 immunity. In this study, female BABL/c mice(6–8 weeks old) were immunized with virus-like particles(VLPs) of EV71 produced in yeast to screen for anti-EV71 antibodies. Two hybridomas that could produce neutralizing antibodies against EV71 were obtained. Both neutralizing m Abs(D4 and G12) were confirmed to bind the VP1 capsid protein of EV71, and could protect > 95% cells from 100 TCID50 EV71 infection at 25 μg/m L solution(lowest concentration). Those two neutralizing m Abs identified in the study may be promising candidates in development for m Abs to treat EV71 infection, and utilized as suitable reagents for use in diagnostic tests and biological studies.

Zika Virus Baculovirus-Expressed Virus-Like Particles Induce Neutralizing Antibodies in Mice

The newly emerged mosquito-borne Zika virus(ZIKV) strains pose a global challenge owing to its ability to cause microcephaly and neurological disorders. Several ZIKV vaccine candidates have been proposed, including inactivated and live attenuated virus vaccines, vector-based vaccines, DNA and RNA vaccines. These have been shown to be efficacious in preclinical studies in mice and nonhuman primates, but their use will potentially be a threat to immunocompromised individuals and pregnant women. Virus-like particles(VLPs) are empty particles composed merely of viral proteins, which can serve as a safe and valuable tool for clinical prevention and treatment strategies. In this study, we used a new strategy to produce ZIKV VLPs based on the baculovirus expression system and demonstrated the feasibility of their use as a vaccine candidate. The pre-membrane(prM) and envelope(E) proteins were co-expressed in insect cells and selfassembled into particles similar to ZIKV. We found that the ZIKV VLPs could be quickly and easily prepared in large quantities using this system. The VLPs were shown to have good immunogenicity in immunized mice, as they stimulated high levels of virus neutralizing antibody titers, ZIKV-specific IgG titers and potent memory T cell responses. Thus, the baculovirus-based ZIKV VLP vaccine is a safe, effective and economical vaccine candidate for use against ZIKV.

Design and immunogenicity assessment of HIV-1 virus-like particles as a candidate vaccine

The rapid growth of the global HIV/AIDS epidemic makes it a high priority to develop an effective vaccine.Since a live attenuated or inactivated HIV vaccine is not likely to be approved for clinical application due to safety concerns,HIV virus like particles(VLPs) offer an attractive alternative because they are considered safer since they lack viral genome.We got a stable eukaryotic cell line by G418 resistance selection,engineered to express the HIV-1 structure protein Gag and Env efficiently and stably.We confirmed the presence of Gag and Env proteins in the cell culture supernatant and that they could self-assemble into VLPs.These VLPs were found to be able to elicit specific humoral and cellular immune response after immunization without any adjuvant.

Development of a novel virus-like particle-based vaccine for preventing tick-borne encephalitis virus infection

Tick-borne encephalitis virus(TBEV)is an important tick-borne pathogen that poses as a serious public health concern.The coverage and immunogenicity of the currently available vaccines against TBEV are relatively low;therefore,it is crucial to develop novel and effective vaccines against TBEV.The present study describes a novel strategy for the assembly of virus-like particles(VLPs)by co-expressing the structural(core/prM/E)and non-structural(NS2B/NS3Pro)proteins of TBEV.The efficacy of the VLPs was subsequently evaluated in C57BL/6 mice,and the resultant IgG serum could neutralize both Far-Eastern and European subtypes of TBEV.These findings indicated that the VLP-based vaccine elicited the production of cross-subtype reactive antibodies.The VLPs provided protection to mice lacking the type I interferon receptor(IFNAR^(-/-))against lethal TBEV challenge,with undetectable viral load in brain and intestinal tissues.Furthermore,the group that received the VLP vaccine did not exhibit significant pathological changes and the inflammatory factors were significantly suppressed compared to the control group.Immunization with the VLP vaccine induced the production of multiple-cytokine-producing antiviral CD4+T cells in vivo,including TNF-α^(+),IL-2^(+),and IFN-γ^(+)T cells.Altogether,the findings suggest that noninfectious VLPs can serve as a potentially safe and effective vaccine candidate against diverse subtypes of TBEV.

Virus like particle-based vaccines against emerging infectious disease viruses

Emerging infectious diseases are major threats to human health.Most severe viral disease outbreaks occur in developing regions where health conditions are poor.With increased international travel and business,the possibility of eventually transmitting infectious viruses between different countries is increasing.The most effective approach in preventing viral diseases is vaccination.However,vaccines are not currently available for numerous viral diseases.Viruslike particles(VLPs) are engineered vaccine candidates that have been studied for decades.VLPs are constructed by viral protein expression in various expression systems that promote the selfassembly of proteins into structures resembling virus particles.VLPs have antigenicity similar to that of the native virus,but are non-infectious as they lack key viral genetic material.VLP vaccines have attracted considerable research interest because they offer several advantages over traditional vaccines.Studies have shown that VLP vaccines can stimulate both humoral and cellular immune responses,which may offer effective antiviral protection.Here we review recent developments with VLP-based vaccines for several highly virulent emerging or re-emerging infectious diseases.The infectious agents discussed include RNA viruses from different virus families,such as the Arenaviridae,Bunyaviridae,Caliciviridae,Coronaviridae,Filoviridae,Flaviviridae,Orthomyxoviridae,Paramyxoviridae,and Togaviridae families.

Comparison of viral propagation and drug response among SARS-CoV-2 VOCs using replicons capable of recapitulating virion assembly and release

Several variants of concern(VOCs)have emerged since the WIV04 strain of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)was first isolated in January 2020.Due to mutations in the spike(S)protein,these VOCs have evolved to enhance viral infectivity and immune evasion.However,whether mutations of the other viral proteins lead to altered viral propagation and drug resistance remains obscure.The replicon is a noninfectious viral surrogate capable of recapitulating certain steps of the viral life cycle.Although several SARS-CoV-2 replicons have been developed,none of them were derived from emerging VOCs and could only recapitulate viral genome replication and subgenomic RNA(sgRNA)transcription.In this study,SARS-CoV-2 replicons derived from the WIV04 strain and two VOCs(the Beta and Delta variants)were prepared by removing the S gene from their genomes,while other structural genes remained untouched.These replicons not only recapitulate viral genome replication and sgRNA transcription but also support the assembly and release of viral-like particles,as manifested by electron microscopic assays.Thus,the S-deletion replicon could recapitulate virtually all the post-entry steps of the viral life cycle and provides a versatile tool for measuring viral intracellular propagation and screening novel antiviral drugs,including inhibitors of virion assembly and release.Through the quantification of replicon RNA released into the supernatant,we demonstrate that viral intracellular propagation and drug response to remdesivir have not yet substantially changed during the evolution of SARS-CoV-2 from the WIV04 strain to the Beta and Delta VOCs.