狂犬病毒蚀斑方法在病毒研究和疫苗研制中的应用

本文采用狂犬病毒CTN-1和4aC株,经Vero细胞传代适应后,以Vero细胞为培养基质,建立了狂犬病毒蚀斑试验和蚀斑减少试验的方法。目前已将此方法应用于病毒鉴定、病毒克隆、病毒滴定以及抗狂犬血清的检测,并取得了较好的结果。     

Double-layer plaque assay for quantification of enteroviruses

We describe here a double-layer plaque assay for the quantification of enteroviruses, combining a monolayer plaque assay and a suspended-cell plaque assay. The double-layer assay provides significantly greater counts than other methods of virus quantification of both suspensions of pure culture viruses and naturally occurring viruses. The counts obtained by this method are approximately one order of magnitude greater than those obtained with the more commonly used method, the monolayer plaque assay. We conclude that the methods available for quantifying viruses rank in efficiency as follows: double-layer plaque assay >or=suspended-cell plaque assay > counting cytopathogenic virus adsorbed to cellulose nitrate membrane filters >or= most probable number of cytopathogenic units > monolayer plaque assay. Moreover, the double-layer plaque assay allows the use of two different cell lines in the two layers. Using the human colonic carcinoma cell line CaCo2 facilitates the recovery of a greater number and diversity of naturally occurring enteroviruses in water than the monolayer agar method. In addition, the pretreatment of cells with 5-iodo-2'-deoxyuridine (IDU) prior to the quantification of enteroviruses by the double-layer plaque assay provides significantly higher recoveries than the use of IDU does with the other methods of quantification.     

用蚀斑法进行麻疹疫苗的病毒滴定

按世界银行中国疫苗项目对麻疹疫苗检定的要求,建立了麻疹疫苗病毒滴定的蚀斑方法。以蚀斑法对Ｈｕ１９１株生产的冻干麻疹活疫苗样品进行了测定。结果发现,Ｈｕ１９１株生产的麻疹疫苗在琼脂和甲基纤维素覆盖下所形成的蚀斑大小及形状不同,但滴度无显著性差异;在室温和３７℃吸附的滴度无显著性差异,但细胞在３７℃生长较好;在本实验条件下,蚀斑滴定和ＣＣＩＤ５０测定的滴度呈正相关,蚀斑滴定相对较敏感;采用国产６孔聚苯乙稀培养板,Ｖｅｒｏ细胞单层,在３７℃吸附,用甲基纤维素覆盖,经结晶紫及甲醛固定染色后计数空斑,操作简便易行,结果特异敏感,重复性好,可用于麻疹疫苗病毒滴定     

Double-Layer Plaque Assay for Quantification of Enteroviruses

We describe here a double-layer plaque assay for the quantification of enteroviruses, combining a monolayer plaque assay and a suspended-cell plaque assay. The double-layer assay provides significantly greater counts than other methods of virus quantification of both suspensions of pure culture viruses and naturally occurring viruses. The counts obtained by this method are approximately one order of magnitude greater than those obtained with the more commonly used method, the monolayer plaque assay. We conclude that the methods available for quantifying viruses rank in efficiency as follows: double-layer plaque assay ≥ suspended-cell plaque assay > counting cytopathogenic virus adsorbed to cellulose nitrate membrane filters ≥ most probable number of cytopathogenic units > monolayer plaque assay. Moreover, the double-layer plaque assay allows the use of two different cell lines in the two layers. Using the human colonic carcinoma cell line CaCo2 facilitates the recovery of a greater number and diversity of naturally occurring enteroviruses in water than the monolayer agar method. In addition, the pretreatment of cells with 5-iodo-2′-deoxyuridine (IDU) prior to the quantification of enteroviruses by the double-layer plaque assay provides significantly higher recoveries than the use of IDU does with the other methods of quantification.     

Design and characterization of a compact dual channel virus counter.

BACKGROUND: Although there is a growing need in the field of biotechnology to rapidly and accurately quantify viruses, time-consuming techniques such as the plaque titer method remain the "gold standard." Flow cytometric methods for virus quantification offer the advantages of rapid analysis and statistical treatment. The technique presented in this work represents the first demonstration of a flow cytometric determination of a viral count that is directly related to the count obtained by plaque titer. METHODS: A flow cytometric instrument for rapid quantification of virus particles was designed, constructed, and thoroughly characterized. A two-color method, which involved staining the viral genome and the protein coat for baculoviruses, was developed in addition to an algorithm to identify simultaneous events on the DNA and protein channels. RESULTS: The instrument was fully characterized, which included analysis of the data acquisition rate, sampling time, flow rate, detection efficiency, linear dynamic range, channel cross-talk, and the limit of detection. Baculovirus samples were analyzed and the results were compared with concentrations obtained by a one-channel flow cytometer and plaque assay. CONCLUSIONS: The dual channel virus counter yields a representative value for the concentration of active viruses in an unpurified sample when compared with plaque assay and a one-channel flow cytometer. The technique is rapid (within minutes), requires only minimal sample preparation and minimum sample size (approximately 100 microl).     

Comparison of Microtiter Procedures with the Plaque Technique for Assay of Vesicular Stomatitis Virus

This paper describes a microprocedure for the tissue culture assay of vesicular stomatitis virus (VSV) and compares the sensitivity of the method with the conventional plaque assay of viral concentration. Microtiter and plaque assay methods were used in titrations, neutralization tests, and thermoinactivation studies with this virus in chick embryo fibroblasts (CEF) and L, HeLa, and PK cell lines. Titration experiments with VSV by the microtiter procedure on preformed monolayers were significantly more sensitive than the plaque assay (P = 0.05). The results of the neutralization tests and thermoinactivation studies also showed greater ability to detect residual virus by the microtiter procedure (P = 0.10). In addition, the microtiter procedure was simpler, less costly, and more rapid than the plaque assay.     

油桐尺蠖核型多角体病毒的空斑测定

在油桐尺蠖卵巢细胞系上对油桐尺蠖核型多角体病毒(BsNPV)进行了空斑测定。用此方法测定了BsNPV的感染力,并将所得的结果与其TCID_(50)进行比较,结果显示这两种方法在测定病毒感染力时敏感性相似。     

Reverse hemolytic plaque assays: versatility in the study of secretion

The reverse hemolytic plaque assay has been used for several years to study hormone release from various endocrine cell types. The basic method utilizes a monolayer (consisting of indicator erythrocytes and the cells under study) that is fixed to the floor of an incubation chamber. Antibody directed against a peptide or protein is added to the chamber. Peptides released from the cells under study complex with the antibody and bind to protein-A on the surface of the indicator erythrocytes. The addition of complement causes the indicator cells to lyse, forming a "plaque" or zone of hemolysis surrounding the secreting cells. The size or rate of formation of these plaques can be used as indices to monitor peptide or protein release. In addition to this standard procedure, the plaque assay can be modified by using loose or unattached indicator cells and is termed the loose plaque assay (LPA). The LPA for a particular peptide can be used alone, sequentially with an assay directed toward another peptide, or repeatedly on the same cells to monitor release over time. In light of the fact that plaque assays do not compromise the function of living cells, it is possible to combine these plaque assays with other procedures such as immunocytochemistry, in situ hybridization, fluorescent microscopy, electrophysiology, and electron microscopy to explore other facets of the secretory process in conjunction with release. When taken together, the plaque assay has been quite useful in the study of endocrine cell secretion. Moreover, with the many adaptations possible, it should be particularly valuable in the future for the study of peptide release in other cell types such as neurons.     

Quantitative real-time PCR for rapid and accurate titration of recombinant baculovirus particles

We describe the use of quantitative PCR (QPCR) to titer recombinant baculoviruses. Custom primers and probe were designed to gp64 and used to calculate a standard curve of QPCR derived titers from dilutions of a previously titrated baculovirus stock. Each dilution was titrated by both plaque assay and QPCR, producing a consistent and reproducible inverse relationship between C(T) and plaque forming units per milliliter. No significant difference was observed between titers produced by QPCR and plaque assay for 12 recombinant viruses, confirming the validity of this technique as a rapid and accurate method of baculovirus titration.     

Accelerated and improved quantification of lymphocytic choriomeningitis virus (LCMV) titers by flow cytometry

Lymphocytic choriomeningitis virus (LCMV), a natural murine pathogen, is a member of the Arenavirus family, may cause atypical meningitis in humans, and has been utilized extensively as a model pathogen for the study of virus-induced disease and immune responses. Historically, viral titers have been quantified by a standard plaque assay, but for non-cytopathic viruses including LCMV this requires lengthy incubation, so results cannot be obtained rapidly. Additionally, due to specific technical constraints of the plaque assay including the visual detection format, it has an element of subjectivity along with limited sensitivity. In this study, we describe the development of a FACS-based assay that utilizes detection of LCMV nucleoprotein (NP) expression in infected cells to determine viral titers, and that exhibits several advantages over the standard plaque assay. We show that the LCMV-NP FACS assay is an objective and reproducible detection method that requires smaller sample volumes, exhibits a ～20-fold increase in sensitivity to and produces results three times faster than the plaque assay. Importantly, when applied to models of acute and chronic LCMV infection, the LCMV-NP FACS assay revealed the presence of infectious virus in samples that were determined to be negative by plaque assay. Therefore, this technique represents an accelerated, enhanced and objective alternative method for detection of infectious LCMV that is amenable to adaptation for other viral infections as well as high throughput diagnostic platforms.     

Application of direct plaque assay for detection and enumeration of bacteriophages of Bacteroides fragilis from contaminated-water samples

The direct double-agar-layer plaque assay for the detection and enumeration of specific bacteriophages of Bacteroides fragilis from contaminated-water samples was performed. Several factors that affect the methods, such as conditions of the bacterial culture, composition of the assay medium, addition of divalent cations, and decontamination techniques applied to the sample, were evaluated. The results obtained show that the direct assay technique proved to be more efficient than the most-probable-number technique. A higher recovery of bacteriophages was obtained from 17 of 24 samples with the direct assay. The two methods only showed similar results from samples with a low degree of pollution.     

Application of direct plaque assay for detection and enumeration of bacteriophages of Bacteroides fragilis from contaminated-water samples.

The direct double-agar-layer plaque assay for the detection and enumeration of specific bacteriophages of Bacteroides fragilis from contaminated-water samples was performed. Several factors that affect the methods, such as conditions of the bacterial culture, composition of the assay medium, addition of divalent cations, and decontamination techniques applied to the sample, were evaluated. The results obtained show that the direct assay technique proved to be more efficient than the most-probable-number technique. A higher recovery of bacteriophages was obtained from 17 of 24 samples with the direct assay. The two methods only showed similar results from samples with a low degree of pollution.     

Development of a new, combined rapid method using phage and PCR for detection and identification of viable Mycobacterium paratuberculosis bacteria within 48 hours

The FASTPlaqueTB assay is an established diagnostic aid for the rapid detection of Mycobacterium tuberculosis from human sputum samples. Using the FASTPlaqueTB assay reagents, viable Mycobacterium avium subsp. paratuberculosis cells were detected as phage plaques in just 24 h. The bacteriophage used does not infect M. avium subsp. paratuberculosis alone, so to add specificity to this assay, a PCR-based identification method was introduced to amplify M. avium subsp. paratuberculosis-specific sequences from the DNA of the mycobacterial cell detected by the phage. To give further diagnostic information, a multiplex PCR method was developed to allow simultaneous amplification of either M. avium subsp. paratuberculosis or M. tuberculosis complex-specific sequences from plaque samples. Combining the plaque PCR technique with the phage-based detection assay allowed the rapid and specific detection of viable M. avium subsp. paratuberculosis in milk samples in just 48 h.     

Viral Concentration Determination Through Plaque Assays: Using Traditional and Novel Overlay Systems

Plaque assays remain one of the most accurate methods for the direct quantification of infectious virons and antiviral substances through the counting of discrete plaques (infectious units and cellular dead zones) in cell culture. Here we demonstrate how to perform a basic plaque assay, and how differing overlays and techniques can affect plaque formation and production. Typically solid or semisolid overlay substrates, such as agarose or carboxymethyl cellulose, have been used to restrict viral spread, preventing indiscriminate infection through the liquid growth medium. Immobilized overlays restrict cellular infection to the immediately surrounding monolayer, allowing the formation of discrete countable foci and subsequent plaque formation. To overcome the difficulties inherent in using traditional overlays, a novel liquid overlay utilizing microcrystalline cellulose and carboxymethyl cellulose sodium has been increasingly used as a replacement in the standard plaque assay. Liquid overlay plaque assays can be readily performed in either standard 6 or 12 well plate formats as per traditional techniques and require no special equipment. Due to its liquid state and subsequent ease of application and removal, microculture plate formats may alternatively be utilized as a rapid, accurate and high throughput alternative to larger scale viral titrations. Use of a non heated viscous liquid polymer offers the opportunity to streamline work, conserves reagents, incubator space, and increases operational safety when used in traditional or high containment labs as no reagent heating or glassware are required. Liquid overlays may also prove more sensitive than traditional overlays for certain heat labile viruses.     

两种HSV-1及猴B病毒相关抗体测定方法的比较

目的以人单纯疱疹病毒（HSV-1）做为抗原,利用空斑法和IFA法比较猴BV和人HSV-1阳性血清两种不同血清的中和能力的差异,建立一种实用、准确、可靠的病毒毒力的检测方法。方法首先,将HSV-1病毒悬液作连续的10倍稀释,取1 mL接种于已经长成单层的Vero-E6细胞上,用1%甲基纤维素覆盖,待其出现蚀斑后计数,算出病毒悬液中每毫升所含蚀斑单位,即滴定出HSV-1的TC ID50。同时,用免疫荧光方法（IFA）对猴和人疱疹阳性血清进行滴定,得到其血清的效价。其次,用滴定出的病毒液分别与两种阳性血清体外中和后,接种到单层的Vero-E6细胞上,用1%甲基纤维素覆盖,待其出现蚀斑后计数。最后,计算出其蚀斑减少率。结果用1%甲基纤维素作覆盖层的蚀斑数量平均为10-5PFU,能形成115-116个/mL蚀斑,形状呈黍米大小的规则圆形,其蚀斑边缘清晰。IFA滴定的人HSV-1阳性血清与猴BV阳性血清的中和抗体均为1∶80。人HSV-1和猴BV两种阳性血清的空斑减少率均为100%。结论确定了利用1%甲基纤维素做为覆盖层可得到清晰可靠的蚀斑,由此方法检测到用人HSV-1可以代替猴B病毒,筛查猴B病毒抗体。且为将来进行药物筛选和中和实验中利用病毒空斑法建立方便、可靠的方法。     

鼠疫菌噬菌体效价噬菌斑测定法的建立

目的建立鼠疫菌噬菌体噬菌斑效价测定方法。方法通过分析细菌接种浓度、孵育吸附时间及培养温度等参数,建立鼠疫菌噬菌体效价测定方法,并分析其精密性;建立鼠疫活疫苗鉴别及纯菌检查用噬菌体效价质量标准。结果经优化后确定细菌接种浓度为7×108/mL,不需孵育吸附,培养温度为29℃,所建立的检测方法精密性较好,用于鼠疫活疫苗鉴别及纯菌检查用噬菌体效价质量标准应不低于1×106PFU/mL。结论建立了鼠疫菌噬菌体噬菌斑效价测定方法,为鼠疫菌噬菌体及疫苗质量控制奠定了基础。     

检测流行性出血热病毒滴度和中和抗体效价的半微量空斑法

建立了检测流行性出血热病毒滴度和中和抗体效价的半微量空斑法。小牛血清与胎牛血清的培养效果无差异。7株不同来源的出血热病毒均能在E6细胞上形成空斑。接种的病毒浓度与形成的空斑数呈直线关系。用空斑法测得的病毒滴度稍低于荧光TCIE50滴定法。空斑减少中和试验的敏感性较荧光中和试验高30倍左右。同时还初步表明了本方法可用于流行性出血热病毒的抗原性分析。     

Enzyme-linked immunosorbent assay-format tissue culture infectious dose-50 test for titrating dengue virus

A dengue nonstructural protein 1 (NS1) antigen capture enzyme-linked immunosorbent assay (ELISA)-based tissue culture infectious dose-50 (TCID(50)) test (TCID(50)-ELISA) was developed as an alternative to the standard plaque assay for titrating dengue virus. Virus titers obtained by TCID(50)-ELISA were comparable to those obtained by the plaque assay and by the traditional TCID(50)-cytopathic effect (CPE) test (TCID(50)-CPE), with a better reproducibility and a lower coefficient of variation. Quantitative comparison of TCID(50)-ELISA and TCID(50)-CPE resulted in a correlation coefficient of 0.976. Moreover, this new method showed a wider application to C6/36, Vero E6, BHK-21, and Vero cells compared with other titration methods. In summary, the novel TCID(50)-ELISA method described here provides a more reliable and more accurate alternative compared to the plaque assay and TCID(50)-CPE for titration of dengue virus.     

Comparison of selectable and plaque assay systems to detect menadione- and UV-induced lacI mutations in mammalian cells.

We have compared the spontaneous mutation frequency and spectrum of lacI genes recovered from a rat embryonic fibroblast line transfected with a lambda-phage shuttle vector (Rat2lambdalacI) using both the traditional plaque assay as well as a positive selection assay. In addition, mutation frequencies and spectrum were determined after treatment of the cells with either the intracellular superoxide-generating compound, menadione, or UVC light. The differences in mutation frequency between the two systems suggested that the selectable assay was better at discerning relatively small mutation frequency increases, more rapidly and at lower cost, than the plaque assay method. Some novel lacI mutations were observed in mutants derived from the selectable assay. This indicates that the selectable assay system may be a useful tool for assessing the mutagenic potential of different agents.