Characterisation and separation of infectious bursal disease virus-like particles using aqueous two-phase systems

Infectious bursal disease(IBD)causes considerable economic losses in the commercial poultry industry worldwide.The principal way to control IBD virus(IBDV),the causative agent of IBD,is still through vaccination programs.Virus-like particles(VLPs)are recognised as a safe and potent recombinant vaccine platform.This research work explores the characterisation and separation of infectious bursal disease virus-like particles(IBD-VLPs)from crude feedstock.Various characteristics were studied with highperformance size-exclusion chromatography(HP-SEC),sodium dodecyl sulphate–polyacrylamide gel electrophoresis(SDS-PAGE)and transmission electron microscopy(TEM)analyses.Subsequently,the separation of IBD-VLPs using polyethylene glycol(PEG)/sodium citrate-based aqueous two-phase systems(ATPSs)was conducted and optimised.Moreover,a scale-up study of the best ATPS constituted of 15%PEG 6000,11%sodium citrate and 10%crude feedstock was performed to compare the separation performance of IBD-VLPs with and without centrifugation-assisted.The results indicated that the optimised ATPS with centrifugation-assisted for both 5 g and 50 g systems showed good recovery of IBDVLPs of>97%in the interphase between the PEG-rich top and salt-rich bottom phases.These optimised systems also showed high removal efficiencies of impurities of>95%.The results demonstrated that aqueous two-phase extraction could be a promising technology for efficient VLPs separation.

Expression,purification and characterization of enterovirus-71 virus-like particles

瞄准：Enterovirus 71 (EV71 ) 作为为在亚太区域与严重神经病学的疾病联系的手，脚和嘴疾病的最近的爆发负责的病因学的代理人被含有。方法：集会过程被假设发生经由一由病毒的朊酶 3CD 的 P1 先锋的安排解朊的处理。测试这个假设，我们构造了 3 recombinant baculoviruses：表示 P1 的 Bac-P1；表示 3CD 的 Bac-3CD；并且 Bac-P1-3CD 共同表示 P1 和 3CD。结果：由 Bac-P1-3CD 的两单个感染和由 Bac-P1 和 Bac-3CD 的合作感染导致了 P1 的正确劈开产出单个蛋白质 VP0， VP1 和 VP3，当以前的途径产出更高的 VLP 生产时。在房间，进类似于真 EV71 粒子总数的像病毒的粒子(VLP ) 的簇自我装配的结构的蛋白质。在 ultracentrifugation 纯化以后，驱散的 VLP 与在尺寸，外观，作文和表面 epitopes 的真病毒难区分，作为由标记的 SDS 页，西方的污点，传播电子显微镜学和免疫黄金决定了。结论：我们的数据第一次，在 EV71 结构的蛋白质采用一个处理和类似于脊髓灰质炎病毒汇编的汇编小径的昆虫房间建议那。粒子形态学和作文的保藏建议 VLP 可以是一个珍贵疫苗的候选人阻止 EV71 流行病。

PRODUCTION IN PICHIAPASTORISAND CHARACTERIZATION OF GENETIC ENGINEERED CHIMERIC HBV/HEV VIRUS-LIKE PARTICLES

Objective To investigate the presentation of a neutralization epitope-containing peptide antigen of hepatitis E virus (HEV) on chimeric virus-like particles (VLPs) of hepatitis B surface antigen (HBsAg). MethodsThe gene fragment corresponding to amino acids (aa) 551-607 (HEnAg) of HEV capsid protein, which contains the only neutralization epitope identified to date, was fused via a synthetic glycine linker in frame with the gene of HBsAg. The resulted fusion gene was then integrated through transformation into the genome of Pichiapastorisunder the control of a methanol-induced alcohol oxidase 1 (AOX1) promoter and expressed intracellularly. The expression products in the soluble cell extracts were characterized by Western blot, ELISA, CsCl density gradient analysis, and electron microscopic visualiza-tion. Results The novel fusion protein incorporating HBsAg and the neutralization epitope-containing HEnAg was expressed successfully in Pichiapastoriswith an expected molecular weight of approximately 32 kD. It was found to possess the ability to assemble into chimeric HBV/HEV VLPs with immunological, physical and morphological characteristics akin to HBsAg particles. Not only did the chimeric VLPs show high activity levels in a HBsAg particle-specific ELISA but they were also strongly immunoreactive with hepatitis E (HE) positive human serum in a HEV specific ELISA, indicating that HEnAg peptide fragments were exposed on VLP surfaces and would be expected to be readily accessible by cells and molecules of the immune system. Similarity between chimeric VLPs to highly immunogenic HBsAg particles may confer good immuno-genicity on surface-displayed HEnAg. Conclusion The chimeric HBV/HEV VLPs produced in this study may have potential to be a recombinant HBV/HEV bivalent vaccine candidate.

A Virus-type Specific Serological Diagnosis of Flavivirus Infection Using Virus-like Particles

Many flaviviruses are emerging and reemerging pathogens,such as West Nile virus(WNV) ,dengue virus(DENV) ,yellow fever virus(YFV) ,and Japanese encephalitis virus. Serological assay is the dominant method for diagnosis of flavivirus infections in human. Because antibodies generated during flavivirus infections cross-react with other flavivirus members,plaque reduction neutralization test(PRNT) is the only available assay to determine the infecting flavivirus type. Since PRNT requires culturing raw viruses,it must be performed in biosafety level-3 or level-4 containment for many flaviviruses,and takes more than ten days to complete. To overcome these problems,we have developed flavivirus viral-like particles(VLPs) that could be used to replace raw viruses in the neutralization assay. The VLPs were prepared by trans packaging a luciferase-reporting replicon with viral structural proteins. This novel assay involves three simple steps:(i) VLPs from a panel of flaviviruses are incubated with flavivirus-infected sera at 37℃ for 1 h;(ii) the neutralized VLPs are used to infect Vero cells;and(iii) the infected cells are measured for luciferase activities at 22 h post-infection. The virus type whose VLP is most efficiently neutralized by the serum specimen(as quantified by the luciferase activities) is the etiologic agent. As a proof-of-concept,we show that a WNV-infected mouse serum neutralized the WNV VLP more efficiently and selectively than the DENV and YFV VLPs. Our results demonstrate that the VLP neutralization assay maintains the "gold standard" of the classic PRNT;importantly,it shortens the assay time from >10 days to <1 day,and can be performed in biosafety level-2 facility.

Characterization of a Putative Filovirus Vaccine:Virus-Like Particles

Filoviruses are hemorrhagic fever viruses endemic to parts of Africa and the Philippines. Infection carries with it a mortality rate of up to 90% and currently there are no effective vaccines or therapeutics available to combat infection. However, the filovirus virus-like particles (VLP), which are currently under development, have been shown to be a promising vaccine candidate. They provide protection from infection in the mouse, guinea pig, and nonhuman primate models of infection, eliciting high anti-glycoprotein antibody titers and T cell responses to viral proteins. In this review, we will highlight the development of the filovirus VLP and describe the current understanding of VLP immunogenicity and correlates of protection.

The codon-optimized capsid gene of duck circovirus can be highly expressed in yeast and self-assemble into virus-like particles

The capsid （Cap） protein, which is the only structural protein of duck circovirus （DuCV）, is the most important antigen for the development of vaccines against DuCV and the virus＇s serological diagnostic methods. In order to use yeast expression system to produce a large quantities of DuCVCap protein which is close to its natural form to display the antigen peptides perfectly, the Cap gene was optimized into the codon-optimized capsid （Opt-Cap） gene towards the preference of yeast firstly. Then, the genes of Cap and Opt-Cap were separately cloned into pPIC9K plasmid and transformed into Picha pas- toris GSl15. The strains that displayed the phenotype of Mut~ and contained multiple inserts of expression cassette were selected from those colonies. After the induction expression, the secretory type of Cap protein, which was about 43 kDa, was best expressed under 0.5% （v/v） methanol and sorbitol induction. Compared with the Cap gene, the expression level of Opt-Cap gene was much higher. What＇s more, the purified Cap protein had a good reactivity to its specific polyclone antibody and DuCV-positive serum, and it was able to self-assemble into virus-like particles （VLPs）. These VLPs, with a diameter of 15-20 nm and without a nucleic acid structure, showed a high level of similarity to DuCV particles in size and shape. All of the resultsdemonstrated that, based on the codon-optimization, it is suitable to use the P. pastoris expression system to produce DuCV VLPs on a large scale. It is the first time that a large amounts of DuCV VLPs were produced successfully in P. pastoris, which might be particularly useful for the further studies of serological diagnosis and vaccines of DuCV.

Carboxyl Terminus Truncated Human Papillomavirus Type 58 L1 Protein Maintains Its Bioactivity and Ability to Form Virus-like Particles

Summary: To prepare carboxyl terminus truncated human papillomavirus type 58 L1(HPV58L1) protein and evaluate its ability to form virus-like particles, the baculovirus and Sf-9 insect cells was used to express HPV58L1 protein, and pFastBac-Htb containing HPV58L1 gene sequence of carboxyl terminus truncation was generated. Then Sf-9 cells were infected with recombinant baculovirus. After being cultured, the post-infected cells expressing-HPV58L1 protein-were harvested and analyzed by SDS-PAGE and Western blot. The ProBond~TM purification system was used for protein purification. The bio-activity of purified protein was identified by mouse erythrocyte hemagglutination assay, and the VLP formation was examined with transmission electron microscope. Our results showed that the recombinant baculovirus was generated and the Sf-9 cells was infected with the recombinant baculovirus, and after collecting, total cellular proteins were extracted. Truncated HPV58L1 protein with MW 58KD was revealed by SDS-PAGE and confirmed by Western blot. The purified L1 proteins under native condition could cause mouse erythrocytes to agglutinate and form VLP. It is concluded that HPV58L1 protein with carboxyl terminus truncation could be efficiently expressed. In baculovirus Sf-9 cells expression system, the purified protein could self-assemble into virions in vitro, and induce agglutination of mouse erythrocytes, indicating that carboxyl terminus truncation does not interfere with the bioactivity of HPV58L1 protein.

Construction and Production of FluorescentPapillom avirus-like Particles

The green fluorescent protein (GFP) from the jellyfish Aequorea victoria has attracted widespread interest since it was demonstrated to be fluorescent in vivo when expressed in other organisms. In order to investigate papillomavirus life cycle which hampered by the unavailability of conventional cell culture system, we constructed a chimeric bovine papillomavirus (BPV) type 1 virus like particles (VLPs) containing GFP. It was found that fluorescent VLPs could be assembled from L2 protein in which GFP is inserted into the N terminal region of L2 (aa 88). The fluorescent VLPs could also be assembled from a GFP/L2 fusion protein in which part of the L2 sequence had been deleted. In vitro , fluorescent VLPs could bind to CV 1 cells, and this VLP/cell interaction could be analyzed by FACS assay. These results demonstrated that GFP could incorporate into BPV1 VLPs without disruption of the VLP structure. Fluorescent VLPs might be a useful tool for study of papillomavirus virus/cell interaction.

Purification of <i>Dengue Virus</i>Particles by One-Step Ceramic Hydroxyapatite Chromatography

Dengue virus type 2 ThNH7/93 retained infectious activity after purification by ceramic hydroxyapatite chromatogra-phy. Dengue virus type 2 culture fluid was loaded onto the ceramic hydroxyapatite column and eluted with a linear gradient of sodium phosphate buffer. Culture fluid and protein contaminants derived from host cells were eluted initially, followed by elutions of dsDNA, and then dengue virus type 2. The recoveries of dengue virus type 2 were 64 ± 14% (n = 11) in the hemagglutination (HA) test and 60% (n = 2) determined by focus assay for viral infectivity. This protocol was highly reproducible, simple, rapid, and appears applicable to other virus species such as influenza virus, Japanese encephalitis virus and adenovirus.

HPV 6b L1VIRUS-LIKE PARTICLES ELICIT HUMORAL IMMUNITY IN MICE

Objective.To test whether intramuscular,intranasal,intrarectal and intravagina l administration of HPV6b L 1 virus-like particlescould induce immune response in mice and to as sess whether intra-muscular and mucosal vaccination against HPV is feasible.Me thods.HPV6b L1proteins self-assembled into VLPs in Sf-9cell in vitro.Mic e were immunized on day0and21with50ìg HPV6b L1VLPs intramuscularly,int ranasally,intrarectally and intravagi-nally respectively.Sera were collected for testing IgG titer after a further7days and3months respec-tively.Results .After immunizations,all mice developed significant anti-HPV6b L1antibody titers in serum by7days after the second immunization.The titer of the serum I gG antibody against HPV6b L1VLPs in the intramuscularly immunized group was h igher than that in the intranasally,intrarectally and intravaginally immunized groups respectively,indicating that both muscular and mucosal administration of HPV6b L1VLPs can stimulate a systemic HPV-specific antibody response.Sera of the mice in the in-tramuscularly immunized group still maintained a high tit er of the serum IgG antibody against HPV6b L1VLPs 3months after the immunizat ion.Conclusion.The results demonstrated that the HPV6b L1VLPs maintain stro ng antigenicity.Immu-nization with HPV6b L1VLPs via intramuscular and mucos al routes,without adjuvant ,can elicit spe-cific antibody in sera.These fin dings suggest that the VLPs are able to induce protective antibodies.

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).

Efficient Humoral and Cellular Immune Responses Induced by a Chimeric Virus-like Particle Displaying the Epitope of EV71 without Adjuvant

Objective To eliminate the side effects of aluminum adjuvant and His-tag,we constructed chimeric VLPs displaying the epitope of EV71（SP70） without His-tagged.Then evaluating whether the VLPs could efficiently evoke not only humoral but also cellular immune responses against EV71 without adjuvant.Methods The fusion protein was constructed by inserting SP70 into the MIR of truncated HBc Ag sequence,expressed in E.Coli,and purified through ion exchange chromatography and density gradient centrifugation.Mice were immunized with the VLPs and sera were collected afterwards.The specific antibody titers,Ig G subtypes and neutralizing efficacy were detected by ELISA,neutralization assay,and EV71 lethal challenge.IFN-γ and IL-4 secreted by splenocytes were tested by ELISPOT assay.Results HBc-SP70 proteins can self-assemble into empty VLPs.After immunization with HBc-SP70 VLPs,the detectable anti-EV71 antibodies were effective in neutralizing EV71 and protected newborn mice from EV71 lethal challenge.There was no significant difference for the immune efficacy whether the aluminum adjuvant was added or not.The specific Ig G subtypes were mainly IgG1 and IgG2 b and splenocytes from the mice immunized produced high levels of IFN-γ and IL-4.Conclusion The fusion proteins without His-tagged was expressed and purified as soluble chimeric HBc-SP70 VLPs without renaturation.In the absence of adjuvant,they were efficient to elicit high levels of Th1/Th2 mixed immune response as well as assisted by aluminum adjuvant.Furthermore,the chimeric VLPs have potential to prevent HBV and EV71 infection simultaneously.

Construction of HIV-1 Virus-like Particle Vaccine

The virus-like particle（VLPs） vaccine is an ideal HIV-1 vaccine, which can simultaneously induce a neutralizing antibody reaction and cell-mediated immunity effectively. In this study, two kinds of plasmids have been used, one can express the HIV-1 main structure proteins, Gagpol and Env, and the other contains an antibiotic gene. The two kinds of plasmids have been cotransfected into 293 cells. A stable cell line that can express Gagpol and Env proteins efficiently and lastingly has been screened. It has been confirmed that Gagpol and Env proteins in the cell culture supernatant can be self-assembled into virus-like particles. The authors have detected the secretion of VLPs in the cell medium, defined the peak of the secretion, and followed and monitored the stability of expression.

铝佐剂对HBoV1 VP2 VLPs诱导小鼠免疫应答的影响

目的:探讨铝佐剂对HBoV1 VP2 VLPs诱导小鼠免疫应答的影响。方法:BABL/c小鼠随机分为VLPs实验组、明矾佐剂实验组、PBS对照组和明矾佐剂对照组。实验组小鼠分别采用HBoV1 VP2 VLPs和HBoV1 VP2 VLPs加明矾佐剂肌肉注射免疫,对照组小鼠同期注射等量明矾佐剂或PBS缓冲液;实验8周后ELISA检测两实验组特异性Ig G抗体效价和活性,ELIspot检测两实验组特异性细胞免疫反应强度,从细胞免疫和体液免疫强度探讨铝佐剂对HBoV1 VP2 VLPs诱导小鼠免疫应答的影响。结果:明矾佐剂降低HBoV1 VP2 VLPs诱导细胞免疫反应强度(P<0.001),增强HBoV1 VP2 VLPs诱导的血清Ig G效价(P<0.01)和Ig G活性(P<0.05)。结论:明矾佐剂使HBoV1 VP2 VLPs诱导的体液免疫反应增强而细胞免疫反应减弱。HBoV1 VP2 VLPs作为预防性疫苗使用时应添加明矾佐剂,作为治疗性疫苗使用时应不加明矾佐剂。

新城疫病毒样颗粒(ND-VLPs)免疫效力的研究

为了研究ND-VLPs的免疫原性,利用共表达NDV F、HN、NP和M蛋白的重组杆状病毒rBac-F-HN-NP-M感染Sf9细胞,采用蔗糖密度梯度离心法纯化释放到细胞培养上清的VLPs,免疫60只,18日龄SPF鸡,监测血清中NDV特异性抗体滴度的变化。2周后用相同剂量的VLPs加强免疫。二免后2周以3.16×103EID50的F48E9株强毒滴鼻攻毒。攻毒前,LaSota灭活苗、LaSota+20μgVLP和不同剂量VLPs组(10μg、20μg、25μg)HI效价分别为28.3、28.9、24.1、26.1、26.7;攻毒后,10μg和20μgVLP免疫组仅能提供了80%和90%的保护率,但与LaSota灭活苗、LaSota+20μgVLP一样,25μgVLP试验组却能够完全抵抗致死剂量的NDV强毒攻击。本试验表明,ND-VLPs具有良好的免疫原性,25μgVLP诱导机体产生的免疫应答能抵抗致死剂量强毒的攻击。ND-VLPs有可能用来研制针对新城疫流行变异株的高效疫苗。

嵌合O型口蹄疫病毒多表位基因猪细小病毒VLPs载体疫苗的构建

综合运用生物信息学和分子生物学技术,模拟PPV VP2蛋白表面不同Loop区插入O型FMDV VP1蛋白上多表位基因(VP1:21～40、141～160和200～213残基)空间构象,并在VP2 N端引入通用型辅助性T淋巴细胞表位(PADRE),人工合成嵌合基因并克隆到杆状病毒转移载体pFastBac HTA中,转化E.coli DH10Bac感受态细胞,经三抗筛选,获得重组杆状病毒表达质粒rBac-FMDV VP1∶PPV VP2,用脂质体法转染Sf9细胞。对rBac-FMDVVP1∶PPV VP2感染的Sf9细胞,用间接免疫荧光试验(IFA)检测,具有特异性荧光;用Western-blotting分析,在64 000处出现一条特异蛋白条带;电镜观察,重组VP2蛋白能够自主组装成病毒样颗粒。红细胞凝集试验证实,表达的嵌合蛋白PPV∶VP2-FMDV∶VP1具有与全病毒类似的血凝活性。

RHDV VLPs对口蹄疫病毒B细胞表位的展示效果

为研究兔出血症病毒(RHDV)病毒样颗粒(VLPs)携带外源表位的能力及其免疫原性,以兔出血症病毒(RHDV)衣壳蛋白VP60为载体,分别在RHDV VP60蛋白质的C端、N端和306位插入FMDV VP1双串联B细胞表位[GS-(200~213 aa)-GS-(141~160 aa)],得到嵌合蛋白质,分别命名为VP60-2FB、VP60-306FB和VP60-578FB。经IFA、SDS-PAGE和Western blot鉴定,嵌合VP60蛋白质在杆状病毒表达系统中均得到有效表达;通过电镜观察发现嵌合蛋白质可自聚成病毒样颗粒。将嵌合蛋白质免疫小鼠,检测产生的免疫应答情况,结果显示,嵌合蛋白质可以产生针对VP60特异的免疫应答,且在插入长度为42 aa外源氨基酸片段的情况下,嵌合蛋白质免疫的小鼠仍能诱导产生较高水平的针对外源表位的特异性应答。在进一步扩展了载体的容纳性后,序列的增加不影响VLPs的形成以及对外源表位的递呈效果,说明VP60-VLPs作为外源B细胞表位展示载体是可行性的。

肠道病毒EV71新型VLPs疫苗的制备及鉴定

目的制备肠道病毒71型(EV71)的新型病毒样颗粒(VLPs)疫苗,为手足口病防治奠定基础。方法应用分子克隆技术构建外壳蛋白VP1融合基因cVP1,免疫细胞化学及Western Blot测定该融合基因在HeLa细胞表达情况;将cVP1克隆于杆状病毒表达载体pFastbac1,应用昆虫细胞TN5制备重组杆状病毒cVP1 rBV,再将此重组病毒与本室保存的gag rBV以不同MOI比例共感染昆虫细胞TN5,得到含有VP1的重组嵌合病毒样颗粒cVP1 VLPs,最后以Westem Blot及电镜进行鉴定。结果免疫细胞化学及Western Blot结果显示构建的融合基因cVP1可在真核细胞内表达,并成功制备成cVP1 rBV,该重组杆状病毒和gag rBV共感染昆虫细胞制备的VLPs结构完整。结论成功制备了EV71的新型VLPs疫苗,为后续研究打下了基础。

补益类复方中药增强流感VLPs疫苗免疫原性的佐剂效应研究

目的探讨补益类复方中药作为佐剂增强流感病毒样颗粒(Virus-like particles,VLPs)疫苗免疫原性的可行性。方法将42只BALB/C小鼠随机分为7组,每组6只,分别为VLPs组、VLPs+益气方组、VLPs+养血方组、VLPs+滋阴方组、VLPs+壮阳方组、VLPs+霍乱毒素组和PBS阴性对照组,分别于0和第14天通过鼻腔使用VLPs进行免疫,加用中药复方佐剂组在第1天至第13天连续灌服中药。VLPs疫苗按10μg/次接种,中药佐剂按200 mg/kg剂量接种,霍乱毒素按1μg/次鼻腔接种。在免疫前及免疫后第13天、第28天采集外周血,在第28天同时采集肺腔灌洗液,测定小鼠外周血清中Ig G水平和肺泡灌洗液中Ig A水平,并进一步对外周血清中和抗体效价进行测定。结果(1)补益类中药具有良好的增强外周血Ig G体液免疫应答的功能,其中益气方、滋阴方可以早期快速提高Ig G水平(P<0.01),而益气方则可以进一步持续性提升Ig G水平(P<0.01);(2)益气方、补血方和滋阴方均可以显著提高VLPs诱导肺腔Ig A水平(P<0.01),其中以益气方组升高最为明显;(3)无论是在免疫应答早期还是后期,益气方、滋阴方均显著提高流感VLPs诱导小鼠外周血中和抗体效价(P<0.01)。结论益气方、滋阴方可以显著增强流感VLPs诱导的外周体液免疫应答和肺脏局部黏膜免疫应答水平,益气联合滋阴方有望成为新型中药佐剂进而增加流感VLPs疫苗免疫原性。