高效液相尺寸排阻色谱-多角度激光散射定量检测灭活禽流感病毒抗原中完整病毒颗粒

本研究旨在建立一种灭活禽流感病毒原料液中完整病毒颗粒准确定量的方法。针对直接采用高效液相尺寸排阻色谱法（high performance size exclusion chromatography，HPSEC）检测灭活禽流感病毒原液存在杂质干扰的问题，首先以H5N8型抗原为对象，分别考察了聚乙二醇（polyethylene glycol，PEG）沉淀和离子交换色谱法（ion exchange chromatography，IEC）进行预处理。在优化条件下，经DEAE FF阴离子交换层析纯化预处理，杂蛋白去除率为86.87%，病毒血凝回收率为100%。HPSEC分析预处理后的样品，8.5–10.0 min处色谱峰样品电泳检测显示主要为H5N8病毒蛋白，动态光散射分析平均粒径为127.7 nm，推测为完整病毒特征峰；在IEC预处理后的样品中加入抗体进行HPSEC检测，8.5-10.0 min处特征峰消失，显示IEC预处理有效去除了杂质干扰。通过将HPSEC与多角度激光散射技术（multi-angle laser scattering technique，MALLS）联用，可以准确获得样品中完整病毒颗粒的数量，且病毒颗粒数与色谱峰面积具有良好线性关系（R²=0.997）。建立的IEC预处理-HPSEC-MALLS检测方法应用于其他亚型（H7N9）、批次和浓度的病毒原液中完整病毒颗粒数的准确检测，均具有良好适用性，且重复性好，相对标准偏差（relative standard deviation，RSD）<5%，n=3。     

Tangential flow microfiltration and ultrafiltration for human influenza A virus concentration and purification

Large scale purification of viruses and viral vectors for gene therapy applications and viral vaccines is a major separation challenge. Here tangential flow microfiltration and ultrafiltration using flat sheet membranes has been investigated for concentration of human influenza A virus. Ultrafiltration membranes with molecular weight cutoffs of 100 and 300 kDa as well as 0.1, 0.2 and 0.45 microm microfiltration membranes have been tested. The results indicate that use of 300 kDa membranes not only concentrate the virus particles but also lead to a significant removal of host cell proteins and DNA in the permeate. Tangential flow filtration may be used to fractionate virus particles. Human influenza A virus particles are spherical with an average size of 100 nm. Use of a 0.1 microm membrane leads to passage of virus particles less than 100 nm into the permeate and an increase of larger particles in the retentate. These results suggest that control of the transmembrane pressure, membrane pore size and pore size distribution could enable isolation of intact virus particles from damaged virions. Isolation of the virus particles of interest from viral fragments and other particulate matter could result in simplification of subsequent purification steps. Larger pore size membranes such as 0.45 microm that allow the passage of all virus particles may be used to remove host cell fragments. In addition virus particles attached to these fragments will be removed. Careful selection of membrane morphology and operating conditions will be essential in order to maximize the benefit of tangential flow filtration steps in the purification of viral products from cell cultures.     

乙肝病毒核心抗原作为载体用于病毒样颗粒疫苗研究的主要进展

乙肝病毒核心抗原(Hepatitis B virus core antigen,HBcAg)是乙肝病毒的核壳结构蛋白,由183～185个氨基酸组成,大小约21～23kD。HBcAg由于其能自我组装成病毒样颗粒(Virus-like particle,VLP)、高表达、易纯化以及强免疫原性等特点,使其成为一个高效安全且应用广泛的VLP载体,可用于各种病原的疫苗研发。发展至今已有数十种病毒、细菌以及寄生虫的相关基因的抗原表位成功表达在HBcAg VLP颗粒上,成为新型疫苗研发的重要平台。     

Plant-produced recombinant influenza vaccine based on virus-like HBc particles carrying an extracellular domain of M2 protein

Conventional influenza vaccines are based on a virus obtained in chicken embryos or its components. The high variability of the surface proteins of influenza virus, hemagglutinin and neuraminidase, requires strain-specific vaccines matching the antigenic specificity of newly emerging virus strains to be developed. A recombinant vaccine based on a highly conservative influenza virus protein M2 fused to a nanosized carrier particle can be an attractive alternative to traditional vaccines. We have constructed a recombinant viral vector based on potato X virus that provides for expression in the Nicotiana benthamiana plants of a hybrid protein M2eHBc consisting of an extracellular domain of influenza virus M2 protein (M2e) fused to hepatitis B core antigen (HBc). This vector was introduced into plant cells by infiltrating leaves with agrobacteria carrying the viral vector. The hybrid protein M2eHBc was synthesized in the infected N. benthamiana plants in an amount reaching 1–2% of the total soluble protein and formed virus-like particles with the M2e peptide presented on the surface. Methods of isolation and purification of M2eHBc particles from plant producers were elaborated. Experiments on mice have shown a high immunogenicity of the plant-produced M2eHBc particles and their protective effect against lethal influenza challenge. The developed transient expression system can be used for production of M2e-based candidate influenza vaccine in plants.     

Removal of chromatin by salt-tolerant endonucleases for production of recombinant measles virus

Host cell DNA is a critical impurity in downstream processing of enveloped viruses. Especially, DNA in the form of chromatin is often neglected. Endonuclease treatment is an almost mandatory step in manufacturing of viral vaccines. In order to find the optimal performer, four different endonucleases, two of them salt tolerant, were evaluated in downstream processing of recombinant measles virus. Endonuclease treatment was performed under optimal temperature conditions after clarification and before the purification by flow-through chromatography with a core shell chromatography medium: Capto™ Core 700. Virus infectivity was measured by TCID50. DNA and histone presence in process and purified samples was determined using PicoGreen™ assay and Western blot analysis using an anti-histone antibody, respectively. All tested endonucleases allowed the reduction of DNA content improving product purity. The salt-tolerant endonucleases SAN and M-SAN were more efficient in the removal of chromatin compared with the non-salt-tolerant endonucleases Benzonase® and DENARASE®. Removal of chromatin using M-SAN was also possible without the addition of extra salt to the cell culture supernatant. The combination of the endonuclease treatment, using salt-tolerant endonucleases with flow-through chromatography, using core–shell particles, resulted in high purity and purification efficiency. This strategy has all features for a platform downstream process of recombinant measles virus and beyond.     

Viral Nucleic Acids in Live-Attenuated Vaccines: Detection of Minority Variants and an Adventitious Virus

Metagenomics and a panmicrobial microarray were used to examine eight live-attenuated viral vaccines. Viral nucleic acids in trivalent oral poliovirus (OPV), rubella, measles, yellow fever, varicella-zoster, multivalent measles/mumps/rubella, and two rotavirus live vaccines were partially purified, randomly amplified, and pyrosequenced. Over half a million sequence reads were generated covering from 20 to 99% of the attenuated viral genomes at depths reaching up to 8,000 reads per nucleotides. Mutations and minority variants, relative to vaccine strains, not known to affect attenuation were detected in OPV, mumps virus, and varicella-zoster virus. The anticipated detection of endogenous retroviral sequences from the producer avian and primate cells was confirmed. Avian leukosis virus (ALV), previously shown to be noninfectious for humans, was present as RNA in viral particles, while simian retrovirus (SRV) was present as genetically defective DNA. Rotarix, an orally administered rotavirus vaccine, contained porcine circovirus-1 (PCV1), a highly prevalent nonpathogenic pig virus, which has not been shown to be infectious in humans. Hybridization of vaccine nucleic acids to a panmicrobial microarray confirmed the presence of endogenous retroviral and PCV1 nucleic acids. Deep sequencing and microarrays can therefore detect attenuated virus sequence changes, minority variants, and adventitious viruses and help maintain the current safety record of live-attenuated viral vaccines.Highly effective, safe, and relatively inexpensive, live-attenuated viruses protect against numerous human and animal viral infections. Attenuation is achieved by genetically adapting viruses for replication in a different host species or under nonphysiological conditions, such that viruses lose their pathogenic potential in their original host species while remaining sufficiently antigenic to induce lasting protective immunity. Live-attenuated vaccines are highly efficacious due to the physiologic presentation of native antigen to the host''s immune system and include the earliest human vaccine developed by serial passages of rabies virus in rabbits. In very rare instances, one attenuated viral vaccine, the oral poliovirus vaccine (OPV), can accumulate mutations as well as recombine with other coinfecting enteroviruses and revert to a pathogenic state (18, 24). Attenuated live vaccines also carry a potential risk of contamination with adventitious viruses introduced during the attenuation process, from the cell lines used, and/or from the animal sera or other biologics often used in cell cultures. Very early Theiler''s yellow fever attenuated virus was once “stabilized” with human plasma thought to contain hepatitis B virus, resulting in many cases of hepatitis (5, 28). Some early Sabin poliovirus vaccines were contaminated with the simian virus 40 (SV40) polyomavirus from the monkey cells used to amplify polioviruses. While carcinogenic in rodents, SV40 has no epidemiologic association with human cancers (10). Avian leukosis virus (ALV) and endogenous avian virus (AEV) have been reported in attenuated vaccines grown in chicken embryo fibroblasts (CEF), but extensive testing has also ruled out human infections (14, 15). Vaccine-associated ALV and AEV are thought to originate from endogenous retroviruses in the chicken germ line (14, 15, 17).Because the chemical inactivation used in the manufacture of killed-virus vaccines is also likely to inactivate adventitious viruses, we focused on eight live-attenuated viruses, OPV (Biopolio), rubella (Meruvax-II), measles (Attenuvax), yellow fever (YF-Vax), human herpesvirus 3 (HHV-3) (Varivax), rotavirus (Rotarix and Rotateq), and multivalent measles/mumps/rubella (MMR-II), to resequence the attenuated viruses and test for the presence of adventitious viruses after viral particle purification, massively parallel pyrosequencing, and viral sequence similarity searches. Vaccine nucleic acids were also analyzed using a panmicrobial microarray.     

The purification of alphavirus virions and subviral particles using ultrafiltration and gel exclusion chromatography

Conventional methods of virus purification using ultracentrifugation frequently result in distorted particles with low levels of biological activity, and are thus unsuitable for preparing samples for high-resolution techniques such as neutron scattering, X-ray scattering in solution, and X-ray crystallography. Moreover, in the event of an instrument failure, ultracentrifugation can also pose a significant hazard when preparing pathogenic viruses or subunits derived from them. By employing exclusively ultrafiltration and gel exclusion chromatography, a method has been developed to prepare highly purified, intact alphavirus particles retaining high levels of biological activity. These procedures have also been adapted to prepare aggregates of viral envelope protein with a defined immunogenic content.     

Large-Scale Purification of Rubella Virus and Preparation of an Experimental Split Rubella Virus Vaccine

Large-scale purification of rubella virus from tissue culture fluid and preparation of an experimental rubella subunit vaccine are described. The virus, purified isopycnically in sucrose gradients, was Tween 80-ether treated, and the product was filtered sterile. The vaccines were of two types, formalinized and nonformalinized. They were not infectious, had only a slight pyrogenicity, and caused no harmful symptoms in animals. The immune response in guinea pigs was better when the nonformalinized vaccine was used and the dosage was 2,500 hemagglutinating units per injection (0.5 ml).     

Potency estimation of measles, mumps and rubella trivalent vaccines with quantitative PCR infectivity assay.

The quantitative PCR infectivity assay is a combination of virus propagation and quantitative PCR. Previously [Schalk JAC, van den Elzen C, Ovelgonne H, Baas C, Jongen PMJM. Estimation of the number of infectious measles viruses in live virus vaccines using quantitative real-time PCR. J Virol Methods 2004;117:179-87.], we used this assay to estimate the titer of infectious measles virus in trivalent, live, measles, mumps, rubella vaccines (MMR). Here we describe the further improvement and development of the assay for simultaneous potency estimation of measles, mumps and rubella viruses. The potency of measles and mumps virus is estimated within one assay after 1 day of cell culture. The potency of rubella virus is estimated in a separate assay after 2 days of cell culture. Compared to conventional CCID50 and plaque assays, the quantitative PCR infectivity assay has the advantage in being fast because the assay is not dependent on the formation of cytopathic effect. Furthermore assay design is simplified: serological neutralization can be omitted because PCR is virus-specific and, under the conditions used, the individual components of trivalent measles, mumps, rubella vaccines do not interfere with each other. The assay was validated and compared to the performance of a plaque assay.     

Virus-like particles production in green plants

Viruses-like particles (VLPs), assembled from capsid structural subunits of several different viruses, have found a number of biomedical applications such as vaccines and novel delivery systems for nucleic acids and small molecules. Production of recombinant proteins in different plant systems has been intensely investigated and improved upon in the last two decades. Plant-derived antibodies, vaccines, and microbicides have received great attention and shown immense promise. In the case of mucosal vaccines, orally delivered plant-produced VLPs require minimal processing of the plant tissue, thus offering an inexpensive and safe alternative to more conventional live attenuated and killed virus vaccines. For other applications which require higher level of purification, recent progress in expression levels using plant viral vectors have shown that plants can compete with traditional fermentation systems. In this review, the different methods used in the production of VLPs in green plants are described. Specific examples of expression, assembly, and immunogenicity of several plant-derived VLPs are presented.     

Optimization of virus detection in cells using massively parallel sequencing

Massively parallel sequencing (MPS)-based virus detection has potential regulatory applications. We studied the ability of one of these approaches, based on degenerate oligonucleotide primer (DOP)-polymerase chain reaction (PCR), to detect viral sequences in cell lines known to express viral genes or particles. DOP-PCR was highly sensitive for the detection of small quantities of isolated viral sequences. Detected viral sequences included nodavirus, bracovirus, and endogenous retroviruses in High Five cells, porcine circovirus type 1 and porcine endogenous retrovirus in PK15 cells, human T-cell leukemia virus 1 in MJ cells, human papillomavirus 18 in HeLa cells, human herpesvirus 8 in BCBL-1 cells, and Epstein–Barr Virus in Raji cells. Illumina sequencing (for which primers were most efficiently added using PCR) provided greater sensitivity for virus detection than Roche 454 sequencing. Analyzing nucleic acids extracted both directly from samples and from capsid-enriched preparations provided useful information. Although there are limitations of these methods, these results indicate significant promise for the combination of nonspecific PCR and MPS in identifying contaminants in clinical and biological samples, including cell lines and reagents used to produce vaccines and therapeutic products.     

Expression in Plants of a Recombinant Protein Based on Flagellin Linked to Conservative Fragments of M2 Protein and Hemagglutintin of Influenza Virus

The composition of traditional influenza vaccines require nearly annual updates due to the high variability of the influenza virus. The use of conservative viral antigens, the extracellular domain of the transmembrane protein M2, and fragments of the second subunit of hemagglutinin provides the opportunity to create recombinant broad-spectrum vaccines. Bacterial flagellin was used as a mucosal adjuvant to increase the immunogenicity of these conservative antigens. Recombinant proteins based on flagellin simultaneously containing M2e and a fragment of the hemagglutinin stem region were expressed in Nicotiana benthamiana plants using a self-replicating vector based on the potato virus X genome. Methods for their isolation from plants and purification have been developed. The developed expression system can be used to produce a new candidate influenza vaccine in plants.     

ELISA法检测疫苗中牛血清残留量的适用性研究

为了验证ELISA法对病毒性疫苗中残余牛血清蛋白检测的适用性,用牛血清蛋白ELISA测定法与牛血清白蛋白ELISA测定法、牛血清IgG-ELISA测定法对麻疹疫苗、风疹疫苗、腮腺炎疫苗洗涤前病毒培养液、洗涤后病毒收获液以及多种成品疫苗中的残余牛血清蛋白含量进行了测定。结果显示,麻疹疫苗、风疹疫苗、腮腺炎疫苗洗涤前病毒培养液中牛血清白蛋白含量依次为IgG含量的70.5倍、65倍、84.3倍,洗涤后病毒收获液中两者比值分别为4.2、1.8和8.1;牛血清白蛋白ELISA法和牛血清蛋白ELISA法均能检测出疫苗中牛血清白蛋白,但前者测不出牛血清IgG,而后者可准确检测牛血清IgG。牛血清蛋白ELISA测定法可同时检测牛血清白蛋白和牛血清IgG,更适用于疫苗残余牛血清蛋白含量的测定。     

A simple and sensitive method for the purification and peptide mapping of proteins solubilized from densonucleosis virus with sodium dodecyl sulfate

An efficient method for the proteolysis and subsequent analysis of dansylated viral (or other) proteins solubilized with sodium dodecyl sulfate (SDS), after their purification using SDS electrophoresis, is described. The dansylation of proteins or the by-products of the reaction do not interfere in this technique. This very simple technique has important advantages over other methods for the purification and characterization of proteins. The method used indicates that the four viral proteins of densonucleosis virus originate at least partially from a common DNA sequence.     

Virus-like particles in picornavirus vaccine development

Virus-like particles (VLP), which are similar to natural virus particles but do not contain viral genes, have brought about significant breakthroughs in many research fields because of their unique advantages. The ordered repeating epitopes of VLP can induce immunity responses similar to those prompted by natural viral infection; thus, VLP vaccines are regarded as candidate alternatives to whole-virus vaccines. As picornavirus has serious impacts on human and animal health, the development of efficient and safe vaccines is a key endeavor in preventing virus infections. The characteristics of picornavirus capsid proteins allow the development of VLP vaccines. This paper investigates research scenarios and progress on picornavirus VLP vaccines with the aim of providing a reference for researchers focusing on virology and vaccinology.     

Studies on live rubella vaccine. V. Quantitative aspects of interference between rubella, measles and mumps viruses in their trivalent vaccine

Rubella vaccine combined with measles and mumps vaccines was administered in a single injection to children of 1 to 5 years of age. All three vaccines were serologically effective, and the clinical reactions caused by measles vaccine were considerably alleviated, when 6 x 10(3) PFU of rubella and 10(4) TCD50 per dose of mumps vaccines were combined with 5 x 10(4) TCD50 of measles vaccine. When a larger amount of mumps vaccine (3 x 10(5) TCD50/dose) was used, it caused interference with the rubella and measles viruses, i.e., the antibody response to rubella virus became poor and the incidence of clinical reactions to measles virus decreased. On the other hand, when 5 x 10(5) TCD50/dose of measles vaccine was combined with 10(4) TCD50/dose of mumps vaccine, the clinical reactions to measles virus were decreased but were almost the same as those induced by this vaccine alone.     

Viremia in a Recipient of HPV-77 Rubella Virus Vaccine

A live rubella virus vaccine, HPV-77 (High Passage Virus - 77 tissue culture passages) was administered subcutaneously to eight rubella-susceptible children housed in an isolation ward. One blood specimen, taken on the tenth day after vaccination, from one of the eight vaccines, yielded a rubella virus. This virus had laboratory markers which were “vaccine-like.” To our knowledge, this represents the first isolation of rubella virus from the blood of a recipient of HPV-77 vaccine. However, the consistent antibody responses among vaccinees and the regular presence of rubella virus in their pharynges argue that viremia occurs in almost every susceptible recipient. The most logical explanation for the failure to document viremia in other recipients of HPV-77 vaccine is that the viremia is ordinarily low grade or transient or both.     

Purification of densonucleosis virus by tangential flow ultrafiltration

Purification at commercial scale of viruses and virus vectors for gene therapy applications and viral vaccines is a major separations challenge. Tangential flow ultrafiltration has been developed for protein purification. Here tangential flow ultrafiltration of parvoviruses has been investigated. Because these virus particles are small (18-26 nm), removal of host cell proteins will be challenging. The results obtained here indicate that 30, 50, and 100 kDa membranes reject the virus particles, whereas 300 kDa membranes allow some virus particles to pass into the permeate. The decrease in permeate flux for the 300 kDa ultrafiltration membrane is much greater than for the 30, 50, and 100 kDa membranes, indicating possible entrapment of virus particle in the membrane pores. The permeate flux and level of protein rejection is strongly affected by the cell culture growth medium. The results indicate that when developing a new process, it is essential that the cell culture and purification operations be developed in parallel.     

土壤病毒生态学研究方法

病毒是地球上最丰富的生物实体,每克土壤中可包含数以亿计的病毒,它不仅影响土壤中其它微生物的群落组成、土壤元素的生物地球化学循环,还会影响土壤微生物的物种进化,甚至影响植物、动物和人体健康。目前人们对土壤中病毒的种类及丰度、分布特征以及功能引起的生态环境效应还知之甚少。在概述病毒生态学研究方法的基础上,对土壤病毒的提取、纯化、定量及分子生态学方法等基本流程进行了比较分析,以期建立一套快速简便、高效稳定的适用于土壤病毒研究的方法,并用于研究土壤病毒的多样性及分布特征,探讨病毒在环境中的生存和传播机制,为土壤病毒的防控及开发利用提供支撑。