A reliable internally controlled RT-nested PCR method for the detection of hepatitis C virus RNA

We have developed a reliable internally controlled RT-nested PCR method for the detection of hepatitis C virus (HCV) RNA using in vitro synthesized Renilla luciferase (Rluc) RNA as an internal control. Using this method, the 5'-noncoding region of HCV RNA (144 nucleotides) and Rluc RNA (276 nucleotides) were efficiently amplified in a single tube, and the sensitivity and specificity of this method were comparable to standard RT-nested PCR. This method was successfully performed on RNA specimens obtained from in vitro HCV-infected human hepatocyte PH5CH8 cells, which support HCV replication. In addition, we demonstrated that this method was useful for the evaluation of antiviral reagents by confirming the anti-HCV activity of bovine lactoferrin, which we previously found to be a new inhibitor of HCV infection. Therefore, this method may be useful for the studies of not only HCV but also of other viruses.     

用逆转录套式PCR检测风疹病毒RNA

目的：介绍一种简便的快速准确检测标本中风疹病毒ＲＮＡ的分子撑方法髟于诊断孕妇感染和胎和的先天性感染风前病毒。方法：选择风疹病毒基因组中编码膜糖蛋白Ｅ１基因中的一个片段作为靶序列进行Ｂ Ｒｅｓｔｅｄ－ＰＣＲ扩增，扩增片段的长度用Ｋｏｄａｋ数码凝胶分析软件１Ｄ２．０３版本进行分析，并用内切酶酶切进行证实。结果：风疹病毒在早孕妇女中的阳性率为１．６３％；在中妊娠羊水中的阳性率为１．１７％。在畸形的儿或死     

Rapid detection and differentiation of Newcastle disease virus by real-time PCR with melting-curve analysis

Summary. In order to rapidly detect and differentiate Newcastle disease virus (NDV) isolates, a method based on real-time PCR SYBR Green I melting-curve analysis of the fusion (F) protein gene was developed. The detection limit of real-time PCR was 9 × 10² plasmid copies and was 100 times more sensitive than conventional PCR. Thirty eight reference NDV strains were rapidly identified by their distinctive melting temperatures (T_ms): 89.23 ± 0.27 °C for velogenic strains, 90.17 ± 0.35 °C for pigeon mesogenic strains, 91.25 ± 0.14 °C for two lentogenic strains (B1 and Ishii). No amplification was detected from unrelated RNA samples by this method. This real-time PCR directly detected NDV from infected tissues and eliminated the gel electrophoretic step for analyzing PCR product using ethidium bromide. The total time for a PCR run was less than 1 hour. The results obtained in this study showed that the real-time PCR presented here is a good screening test for the identification of NDV.     

Loop-mediated isothermal amplification for rapid detection of Newcastle disease virus

We have evaluated a diagnostic system based on the loop-mediated isothermal amplification (LAMP) assay for the rapid, simple, and sensitive detection of Newcastle disease virus (NDV) directly from culture isolates as well as clinical samples. By using one set of specific primers targeting the fusion protein gene, the LAMP assay rapidly amplified the target gene within 2 h, requiring only a regular laboratory water bath or heat block for reaction. The results obtained from testing the genomes of 38 NDV strains, other different viruses, and clinical samples of experimentally infected chickens showed that LAMP was as sensitive and specific as nested PCR. All LAMP-positive samples were positive by nested PCR. The LAMP assay is faster than nested PCR, cost-effective, and easy to perform. Our results clearly demonstrate that the LAMP-based assay is a useful tool for the rapid and sensitive diagnosis of NDV infection.     

Consensus RT-nested PCR detection of yellow head complex genotypes in penaeid shrimp

A consensus RT-nested (n)PCR is described that detects the six distinct genotypic variants in the yellow head virus (YHV) complex. The PCR primers targeted ORF1b gene regions more highly conserved amongst the reference strains of YHV (genotype 1) and gill-associated virus (GAV, genotype 2) and a set of 57 field isolates containing multiple representatives of each genotype. The test employed short PCR (359 bp) and nPCR (147 bp) amplicons to minimise the effects of RNA degradation. To ensure < or = 8-primer degeneracy, two primers were designed to each site, one accommodating sequence variations amongst genotype 1 isolates and the other variations amongst isolates of the other genotypes. The analytical sensitivity limits of the PCR and nPCR were estimated to be approximately 1250 and approximately 1.25 RNA copies, respectively. The superior group-specificity of the consensus RT-nPCR compared to other OIE-recommended PCR tests for YHV/GAV was demonstrated using RNA from 17 Penaeus monodon shrimp infected with representatives of each of the six genotypes. Phylogenetic analysis using the 94 nt ORF1b gene sequence spanned by the nPCR primers generated genotype assignments that were consistent with those obtained using the extended 671 nt sequence used for the initial identification of genotypes.     

Some properties of an avirulent Newcastle disease virus

Summary Newcastle disease virus was isolated from healthy birds using chick kidney cultures. The virus strain involved was exceptionally attenuated in character and appeared to be transmitted by the enteric route. It caused no clinical illness even in day old chicks and did not regularly kill embryonated eggs. The virus is relatively thermostable and its haemagglutinin is exceptionally stable at 56 C. This easily observed property may be useful in genetic studies of the virus.     

Recombinant haemagglutinin neuraminidase antigen-based single serum dilution ELISA for rapid serological profiling of Newcastle disease virus

A recombinant haemagglutinin neuraminidase (HN) antigen-based single serum dilution enzyme linked immuno-sorbent assay (ELISA) was developed to measure the specific antibody in sera of chickens against Newcastle disease virus. A linear relationship was found between the predicted antibody titres at a single working dilution of 1:1000 and the corresponding observed serum titres as determined by the standard serial dilution method. Regression analysis was used to determine a standard curve from which an equation was derived that allowed the demonstration of this correlation. The equation was then used to convert the corrected absorbance readings of the single working dilution directly into the predicted ELISA antibody titres. The assay proved to be sensitive, specific and accurate as compared to the standard haemagglutination inhibition (HI) test.     

Real-time PCR assay for the detection of tanapox virus and yaba-like disease virus

The yatapoxvirus genus contains three members: tanapox virus (TPV), yaba-like disease virus (YLDV) and yaba monkey tumor virus (YMTV), two of which (TPV and YLDV) may infect humans. However, only a very small number of patients have been diagnosed with TPV outside Africa. Given the increased international travel and the similarity of clinical signs during the early stages of a TPV/YLDV infection as compared to diseases caused by agents of potential biological warfare, such as smallpox, monkeypox, tularemia and anthrax, the rapid and reliable recognition of a TPV/YLDV infection is crucial. A real-time PCR assay using TaqMan^® chemistry was developed in order to identify unambiguously TPV/YLDV. Primers and probe targeting a 101 bp region of the PstI L fragment of TPV, initial optimisations steps were carried out with YLDV DNA as template. Using probit regression analysis, the lower limit of detection was calculated to be ca. 8 copies per assay. A total of five TPV strains, one YDLV strain and scab-derived DNA from a patient with a TPV infection yielded specific amplification, whereas the DNA of YMTV was not amplified. Various viral and bacterial pathogens (n = 29) associated with rash-causing illnesses were not detected using this assay.     

Quantitative estimation of Newcastle disease virus antibody levels in chickens and turkeys by ELISA

A quantitative single-well ELISA for estimation of Newcastle disease (ND) virus antibodies in chickens and turkeys was developed using purified antigen from PMV-1/Chicken/Ulster 2C/71. The test was standardised using sera from 20-week-old chickens or 20- 30-week-old turkeys. Absorbance values for negative sera in chickens increased with the age of the birds but overall was lower than the cut-off for the test. ND haemagglutination inhibition (HI) positive field sera were always positive by ELISA and the mean was significantly higher than that of the negative population. Standard antisera to four of seven of the other PMV serotypes (including PMV-3) gave positive reactions in ELISA and three were also positive at low level by PMV-1 HI test. Absorbance values remained negative in turkeys given two inoculations of PMV-3 vaccine in spite of good PMV-3 HI responses. Doubling dilutions of chicken and turkey sera were tested by ELISA and end-point titres calculated. Standard curves relating ELISA titre and absorbance of each sample at 1/100 dilution were constructed and used to determine titres of test samples from single well absorbance values. A significant positive correlation between ELISA titre and HI titre for chicken and turkey sera was demonstrated. Sensitivity of the test was investigated using birds experimentally infected with PMV-1/Chicken/Ulster 2C/71 or a pigeon PMV-1 isolate. Seroconversion was detected at the same time by ELISA and HI. In experiments to estimate the ELISA titre required to protect birds against virulent ND, five groups of chickens were vaccinated twice with one of four commercial ND vaccines (three inactivated; one live) on two occasions and challenged with a virulent ND strain (PMV-1/ Chicken/Antrim/73). Two of the groups vaccinated with inactivated vaccines were protected against challenge. In another group also given inactivated vaccine, clinical signs were seen in one bird and ELISA proved a better indicator of immune status than HI. In the groups given living vaccine, no signs of ND were seen and ELISA indicated a much higher level of vaccinal antibody than HI test. In turkeys given two inoculations with inactivated vaccine, antibody levels were boosted to acceptable levels by ELISA and HI indicating that vaccinal antibody levels were adequate.     

Newcastle disease virus pathotypes

The clinical signs, mortality and postmortem findings following infection of six-week-old chicks with nine strains of Newcastle disease virus were studied. Although strains could be divided into four pathotypes the divisions were not clear-cut. The most prominent feature of disease following infection by two isolates from the post-1970 USA epidemic, a 1962 UK isolate and a 1972 UK isolate were haemorrhagic gut lesions. A virus isolate from the post-1970 UK epidemic, Lamb-Essex '70, rarely caused gut lesions in infected birds although this was the only strain to consistently induce oedema of the eye in infected birds.     

Comparison of pathology-based techniques for detection of viscerotropic velogenic Newcastle disease virus in chickens

Two pathology-based techniques, immunohistochemistry and riboprobe in-situ hybridization, were applied to formalin-fixed, paraffin wax-embedded tissues from chickens infected with three different isolates of velogenic viscerotropic Newcastle disease virus (VVNDV). With the immunohistochemical method, viral protein was consistently detectable in the spleen and caecum at the terminal phase of the infection. With in-situ hybridization, viral nucleic acid was consistently detected in the eyelid, spleen and caecum in both the acute and terminal phases. Hybridization with anti-sense probe to detect viral mRNA was often more intense than hybridization with sense probe to detect viral genomic RNA.     

Development of an indirect ELISA for the detection of antibodies to swine vesicular disease virus during monitoring studies

An indirect ELISA (I-ELISA) has been developed for swine vesicular disease virus-specific antibody detection. The analytic sensitivity of I-ELISA testing of serum samples from experimentally infected pigs with the known VN titer was 2 log2. Its diagnostic specificity was demonstrated as 100% in 4485 swine serum samples from different regions of the Russian Federation.     

Detection and differentiation of virulent and avirulent strains of Newcastle disease virus by real-time PCR

A rapid diagnostic method based on the melting curve SYBR Green I real-time PCR analysis was developed to detect and differentiate Newcastle disease virus (NDV) strains. Degenerated primers based on the cleavage site sequence of the F0 gene were designed to detect specific sequences characteristic of virulent and avirulent strains of NDV.Eighteen strains of NDV from four lineages were identified and grouped into virulent and avirulent strains. Peaks on the melting temperature graph with melting temperature values between 80.00 and 83.80 °C were observed for lentogenic (avirulent) strains. T_m values higher than 83.80 were observed for virulent (mesogenic and velogenic) strains. The detection limit of real-time PCR was 2 × 10² plasmid copies per reaction or 10² EID₅₀ for velogenic strains and 10³ EID₅₀ for lentogenic strains.The results obtained in this study demonstrate the possible applications for melting curve real-time PCR analysis in laboratory practice for the diagnosis and differentiation of avirulent and virulent strains of Newcastle disease virus.     

Physicochemical studies of Newcastle disease virus

Summary Chemical analysis was performed on the highly purified Newcastle disease virus (NDV) obtained from infected allantoic fluid. Mean values of RNA content of the virus based on optical density at 260 m, phosphorus content and orcinol reaction which were carried out after the fractionation bySchmidt-Thannhauser-Schneider procedure modified byFleck andMunro were 0.72%, 0.99% and 0.92%, respectively. Contents of protein and lipid in the virus were also determined.Isolation of the RNA from NDV was performed by hot-SDS-phenol extraction from³²P-labeled virus and sedimentation patterns of the RNA in sucrose density gradients were examined. The sedimentation constant of NDV-RNA was found to be 55S, and this component was completely digested with ribonuclease. By this observation and the base composition previously determined, the RNA of NDV must be single stranded. The molecular weight of the RNA was estimated 5.8×10⁶ at least from the weight and RNA content of the virus particle.Results of this study were presented at the 13th General Meeting of the Society of Japanese Virologists, in Nagasaki, October 1965.