Comparison of commercial systems for extraction of nucleic acids from DNA/RNA respiratory pathogens

This study compared six automated nucleic acid extraction systems and one manual kit for their ability to recover nucleic acids from human nasal wash specimens spiked with five respiratory pathogens, representing Gram-positive bacteria (Streptococcus pyogenes), Gram-negative bacteria (Legionella pneumophila), DNA viruses (adenovirus), segmented RNA viruses (human influenza virus A), and non-segmented RNA viruses (respiratory syncytial virus). The robots and kit evaluated represent major commercially available methods that are capable of simultaneous extraction of DNA and RNA from respiratory specimens, and included platforms based on magnetic-bead technology (KingFisher mL, Biorobot EZ1, easyMAG, KingFisher Flex, and MagNA Pure Compact) or glass fiber filter technology (Biorobot MDX and the manual kit Allprep). All methods yielded extracts free of cross-contamination and RT-PCR inhibition. All automated systems recovered L. pneumophila and adenovirus DNA equivalently. However, the MagNA Pure protocol demonstrated more than 4-fold higher DNA recovery from the S. pyogenes than other methods. The KingFisher mL and easyMAG protocols provided 1- to 3-log wider linearity and extracted 3- to 4-fold more RNA from the human influenza virus and respiratory syncytial virus. These findings suggest that systems differed in nucleic acid recovery, reproducibility, and linearity in a pathogen specific manner.     

Comparison of six nucleic acid extraction methods for detection of viral DNA or RNA sequences in four different non-serum specimen types.

BACKGROUND: Extraction of viral nucleic acids from serum samples is widely used in diagnostic pathology tests. However, the heterogeneous nature of non-serum samples may contribute to variations in the yields of viral nucleic acids with different extraction methods and specimen types. OBJECTIVES: Six different methods were compared for optimal extraction of viral DNA or RNA from four types of non-serum specimens. STUDY DESIGN: The DNA viruses used were herpes simplex virus and cytomegalovirus. The RNA viruses were poliovirus, rotavirus and small round structured virus. The specimens used were from respiratory, genital, faecal and peripheral blood mononuclear cell samples. The extracted nucleic acids were amplified by PCR and detected in an enzyme immunoassay using digoxygenin-labelled amplicons. RESULTS AND CONCLUSIONS: For extraction of viral DNA, the phenol-chloroform method yielded the highest amount of DNA as judged by endpoint titration. The three methods compared for extraction of viral RNA used guanidine isothiocyanate and the QiaRNA kit was shown to yield the highest amount of viral RNA.     

Pre-analytical and analytical procedures for the detection of enteric viruses and enterovirus in water samples

Practical pre-analytical and analytical procedures were developed and validated for detection of enteric viruses in three water matrices. Both RNA viruses (norovirus, coxsackievirus, echovirus, and rotavirus) and DNA virus (adenovirus 41) were included in the study. The NanoCeram 90mm laminated disc with electropositive filter and procedures of filtration, elution and flocculation were utilized to concentrate known amount of viruses in different water matrices. Real time quantitative PCR was used to evaluate the recovery of virus and cell culture to assess viral infectivity. There was no PCR inhibition using various concentrations and pH of beef extract eluting buffer. A good recovery of the viruses spiked in 10L of deionized water was achieved for serial dilutions of coxsackievirus (41-67%), echovirus (22-90%), norovirus (23-44%) and rotavirus (24-46%). Relatively lower recovery was observed for adenovirus 41 (24-35%). There was no significant difference in viral recovery from deionized, tap and river water samples. The infectivity of recovered adenovirus, coxsackievirus and echovirus was demonstrated using in vitro cell culture. The pre-analytical and analytic procedures attained consistent recovery of RNA and DNA viruses both as infectious viral particles and viral genome, provided effective removal of inhibitory substances, achieved reliable reproducibility, and were relatively inexpensive for monitoring viruses in water.     

Detection and heterogeneity of herpesviruses causing Pacheco's disease in parrots

Pacheco's disease (PD) is a common, often fatal, disease of parrots. We cloned a virus isolate from a parrot that had characteristic lesions of PD. Three viral clones were partially sequenced, demonstrating that this virus was an alphaherpesvirus most closely related to the gallid herpesvirus 1. Five primer sets were developed from these sequences. The primer sets were used with PCR to screen tissues or tissue culture media suspected to contain viruses from 54 outbreaks of PD. The primer sets amplified DNA from all but one sample. Ten amplification patterns were detected, indicating that PD is caused by a genetically heterogeneous population of viruses. A single genetic variant (psittacid herpesvirus variant 1) amplified with all primer sets and was the most common virus variant (62.7%). A single primer set (23F) amplified DNA from all of the positive samples, suggesting that PCR could be used as a rapid postmortem assay for these viruses. PCR was found to be significantly more sensitive than tissue culture for the detection of psittacid herpesviruses.     

Loop-mediated isothermal amplification assay for the diagnosis of retinitis caused by herpes simplex virus-1

A loop-mediated isothermal amplification (LAMP) assay was developed for the detection of herpes simplex virus 1 (HSV-1). The specificity of the assay was tested using DNA extracted from HSV-1-infected rabbit corneal epithelium cultures, HSV-2 grown on Vero cell line, cytomegalovirus (CMV) (AD-169), varicella zoster virus (VZV) (Oka-vaccine), adenovirus, Aspergillus flavus and Staphylococcus aureus. The specificity of LAMP was confirmed by bidirectional sequencing of the amplicons. The sensitivity of the LAMP assay was tested using different concentrations of HSV-1 DNA. To evaluate the application of the LAMP assay in clinical diagnosis, we tested vitreous samples from 20 patients with suspected viral retinitis using LAMP and real-time PCR for HSV-1. The LAMP primers amplified only HSV-1 DNA; no LAMP products were detected with the DNAs of HSV-2, CMV, VZV, adenovirus A. flavus and S. aureus. The sequences of the positive HSV-1 LAMP products perfectly (99–100%) matched the HSV-1 sequences deposited in the GenBank database. LAMP is as sensitive as real-time PCR, with the lowest detection limit being 10 copies/μL of HSV-1 DNA. Of the 20 patients with suspected viral retinitis, four tested positive for HSV-1 using real- time PCR and LAMP. A 100% concordance was observed across the two methods. The LAMP assay is a rapid, highly specific and sensitive method for the diagnosis of retinitis caused by HSV-1.     

柯萨奇病毒B3VP1重组腺病毒载体疫苗rAd/VP22-L-VP1的构建及表达**

背景：VP22是单纯疱疹病毒1型(Herpes simplex virus type 1,HSV-1)UL49基因编码的碱性蛋白质,具有蛋白转导结构域(protein transduction domain, PTD),能够把与之融合的蛋白或与之结合的DNA 等大分子跨膜送递到邻近细胞,在基因靶向预防中表现出优势。 目的：构建表达单纯疱疹病毒1型VP22与柯萨奇病毒B3主要中和抗原VP1融合蛋白的重组腺病毒载体疫苗,观察外源基因在HEK293细胞中的良好表达。 方法：PCR法扩增目的基因HSV-1 VP22和CVB3 VP1,经Linker连接,将VP22-L-VP1插入腺病毒穿梭载体pAdTrack-CMV,构建重组穿梭质粒AdTrack-CMV/VP22-L-VP1。再将此载体与腺病毒骨架载体pAdEasy-1在大肠杆菌BJ5183中进行同源重组,生成重组腺病毒质粒pAd/VP22-L-VP1,脂质体介导pAd/VP22-L-VP1转染HEK293细胞包装重组腺病毒rAd/VP22-L-VP1。HEK293细胞上进行病毒扩增和滴定并检测外源基因的表达。 结果与结论：构建的重组腺病毒载体pAd/VP22-L-VP1经过第4轮扩增,其滴度达到6.77×107 pfu/mL,体外感染293细胞可见VP22和VP1融合蛋白的表达。说明实验成功构建并包装重组腺病毒rAd/VP22-L-VP1。     

Universal virus detection by degenerate-oligonucleotide primed polymerase chain reaction of purified viral nucleic acids

This study describes a novel non-specific universal virus detection method that permits molecular detection of viruses in biological materials containing mixtures of cells and viruses. Samples are subjected to nuclease digestion and ultracentrifugation to separate encapsidated viral nucleic acids from cellular nucleic acids. A degenerate oligonucleotide primer PCR (DOP-PCR) that has been optimized for the non-specific amplification of virus sized genomes is then employed. Virus identification is performed by sequencing of cloned DOP-PCR products followed by sequence comparison to sequences published in GenBank. This method was used to detect a variety of DNA viruses (including HSV, VZV, SV40, AAV, and EBV) and RNA viruses (including HTLV-I, HTLV-II, influenza, and poliovirus), which were spiked into cells, constitutively expressed in cell culture, or detected in productively infected cultured cells. This novel approach was compared with a non-specific virus detection method used previously and found to be several logs more sensitive. This type of approach has potential utility in solving virus detection and discovery problems where other methods have failed.     

Echovirus 5: infectious transcripts and complete nucleotide sequence from uncloned cDNA

Echovirus 5 (EV5) may be isolated from various neurological and exanthematic diseases. To determine the relationship of EV5 to other enteroviruses and for studies of its interactions with the target cell, the complete nucleotide sequence of EV5 was determined. Three overlapping fragments, collectively representing the complete genome, were amplified with RT-PCR and sequenced. Analysis of the EV5 sequence revealed a typical enterovirus-like organization of the genome. To verify that the cDNA generated sequence was derived from infectious viruses, complete EV5 genomes were amplified in one amplicon by long distance PCR. Transfection of in vitro transcribed RNA from these amplicons into cell cultures resulted in replicating EV5. Comparison of the overall nucleotide and amino acid sequences demonstrates that EV5 can be regarded as a coxsackievirus B-like enterovirus. Variable sequences between EV5 and the well characterized coxsackievirus B3 (CVB3) are for the most part observed for amino acid residues that correspond to exposed sequences in the CVB3 capsid. This observation indicates that the reported EV5 strain recently diverged from group B coxsackieviruses.     

Sera of Peruvians with fever of unknown origins include viral nucleic acids from non-vertebrate hosts

Serum samples collected from 88 Peruvians with unexplained fever were analyzed for viral sequences using metagenomics. Nucleic acids of anelloviruses, pegivirus A (GBV-C), HIV, Dengue virus, and Oropouche virus were detected. We also characterized from two sera the RNA genomes of new species of partitivirus and dicistrovirus belonging to viral families known to infect fungi or arthropod, respectively. Genomic DNA of a putative fungal cellular host could be PCR amplified from the partitivirus-containing serum sample. The detection in human serum of nucleic acids from viral families not known to infect vertebrates may indicate contamination during sample collection and aliquoting or human infection by their presumed cellular host, here a fungus. The role, if any, of the non-vertebrate infecting viruses detected in serum in inducing fever is unknown.     

心肌炎和克山病患者分离的肠道病毒核酸序列分析

目的 分析自心肌炎和克山病患者分离的肠道病毒的核酸序列,探讨病毒病因的分子基因。方法 使用肠道病毒特异引物对从心肌炎和克山病患者分离的肠道病毒RNA进行RT－PCR扩增,PCR产物经纯经后分别经不同的引物正反向直接核酸循环测序,并应用SeqEd和DNA软件及AssemblyLIGN软件对测序结果进行分析。结果 确定7株病毒5′端从核苷酸位点40到750之间710bp基因序列;序列分析结果发现,尽管为同血清型病毒,但其5′非编码区基因变异率仍在15％左右,而血清型为柯萨奇B5病毒则高达34．08％,与肠道病毒各血清型之间5′端非编码区基因变异率无明显差异;对血清型为CVB3的两分离株病毒5′端基因特殊位点分析,发现与CVB3标准株（Nancy株）比较234位由T→C、690位由C→A。结论 确定了所分离到的一些肠道病毒5′端非编码区序列;肠道病毒5′端非编码区基因与血清型关系不大;CVB3分离株5′端基因特殊位点变异与致病的关系值得进一步探讨。     

Defined recombinants of poliovirus and coxsackievirus: sequence-specific deletions and functional substitutions in the 5'-noncoding regions of viral RNAs

We describe the isolation of a variant of a polio--coxsackie recombinant virus (PCV110) containing a genomic RNA with a chimeric 5'-noncoding region. The variant virus [designated PCV110(1)] has growth and biosynthetic properties that are quite different from the original, temperature-sensitive isolate of the recombinant virus [designated PCV110(4)]. Nucleotide sequencing of the 5'-noncoding region of RNA from PCV110(1) revealed a 4-base deletion within the substituted coxsackievirus region of the chimeric genome that may contribute to the loss of temperature sensitivity of this variant recombinant virus. In addition, we have generated new recombinant viruses that contain (1) coxsackievirus sequences within the N66-N627 region of the poliovirus genome and (2) coxsackievirus sequences substituted from N1-N627 in the poliovirus genome. These recombinant viruses are not temperature sensitive for growth at 37 degrees and have biosynthetic properties similar to those of wild-type poliovirus. Our results provide evidence that replicase recognition signals encoded in the 5' noncoding regions of enterovirus genomic RNAs are not strictly sequence specific.