PCR ELISA for the quantitative detection of Epstein-Barr virus genome

Individuals infected with JC polyomavirus do not present detectable JC virus DNA in oropharyngeal fluids

JC virus (JCV) is ubiquitous in the human population. Primary infection normally occurs during childhood and is followed by a lifelong persistent infection. The main mode of transmission remains unknown. Several authors have hypothesized that JCV transmission occurs through the respiratory route, and that respiratory secretions could represent a possible source of viral particles. The present study intended to evaluate oropharyngeal fluids from patients infected with JCV, in order to ascertain if respiratory secretions could indeed constitute a source of exposure to this polyomavirus. Oropharyngeal washing samples from 25 patients co-infected with JCV and human immunodeficiency virus type 1 were evaluated for the presence of JCV DNA. Regardless of the titre of antibodies or the presence of viral urinary excretion, JCV genome was not detected in oropharyngeal samples collected from any of the patients infected with JCV included in this study, which may suggest that oropharyngeal fluids are an unlikely source for JCV infection.

Development of a microtiter plate hybridization-based PCR-enzyme-linked immunosorbent assay for identification of clinically relevant human group A rotavirus G and P genotypes

A microtiter plate hybridization-based PCR-enzyme-linked immunosorbent assay (PCR-ELISA) has been used for the detection and identification of a variety of microorganisms. Here, we report the development of a PCR-ELISA for the identification of clinically relevant human rotavirus VP7 (G1 to G6, G8 to G10, and G12) and VP4 (P[4], P[6], P[8], P[9], and P[14]) genotypes. The G and P types of reference human and animal rotavirus strains for which specific probes were available were correctly identified by the PCR-ELISA. In addition, reference strains bearing G or P genotypes for which specific probes were unavailable, such as G11, G14, P[3], P[10], and P[11], did not display any cross-reactivity to the probes. The usefulness of the assay was further evaluated by analyzing a total of 396 rotavirus-positive stool samples collected in four countries: Brazil, Ghana, Japan, and the United States. The results of this study showed that the PCR-ELISA was sensitive and easy to perform without the use of any expensive and sophisticated equipment, the reagents used are easy to obtain commercially and advantageous over multiplex PCR since more than one type-specific probe is used and the selection of probes is more flexible.

Production of anti-digoxigenin antibody HRP conjugate for PCR-ELISA DIG detection system

There are several methods used to visualize the end product of polymerase chain reactions. One of these methods is an ELISA-based detection system (PCR-ELISA) which is very sensitive and can be used to measure the PCR products quantitatively by a colorimetric method. According to this technique, copies of DNA segments from genomic DNA are amplified by PCR with incorporation of digoxigenin-11-dUTP. Samples are analyzed in a microtiter plate format by alkaline denaturation and are hybridized to biotinylated allele-specific capture probes bound to streptavidin coated plates. Use of the produced anti-digoxigenin antibody horseradish peroxidase conjugate and the substrate 2,2'-azino-di-3-ethylbenzthiazolinsulfonate (ABTS) detected the hybridized DNA. One of the key components in this procedure is the anti-digoxigenin antibody HRP conjugate. Described here is the preparation, purification, and characterization of anti-digoxigenin antibody HRP conjugate for use in the PCR-ELISA DIG detection system. Several biochemical protocols and modifications were applied to increase the sensitivity and specificity of this conjugate for an efficient and cost-effective product.

Advances in developing molecular-diagnostic tools for strongyloid nematodes of equids: fundamental and applied implications

Infections of equids with parasitic nematodes of the order Strongylida (subfamilies Strongylinae and Cyathostominae) are of major veterinary importance. In last decades, the widespread use of drugs against these parasites has led to problems of resistance within the Cyathostominae, and to an increase in their prevalence and intensity of infection. Novel control strategies, based on improved knowledge of parasite biology and epidemiology, have thus become important. However, there are substantial limitations in the understanding of fundamental biological and systematic aspects of these parasites, which have been due largely to limitations in their specific identification and diagnosis using traditional, morphological approaches. Recently, there has been progress in the development of DNA-based approaches for the specific identification of strongyloids of equids for systematic studies and disease diagnosis. The present article briefly reviews information on the classification, biology, pathogenesis, epidemiology of equine strongyloids and the diagnosis of infections, highlights knowledge gaps in these areas, describes recent advances in the use of molecular techniques for the genetic characterisation, specific identification and differentiation of strongyloids of equids as a basis for fundamental investigations of the systematics, population biology and ecology.

PCR-ELISA I: Application to simultaneous analysis of mixed bacterial samples composed of intestinal species

Sixteen oligonucleotide identification probes, designed in this study or adapted from literature, were tested for a PCR-ELISA application to simultaneously detect under standardised conditions selected intestinal bacteria, lactobacilli and bifidobacteria. The level of specificity obtained with most of the probes fulfilled the set criteria. The lack of efficiency of PCR performed with the primers, proposed to be specific for the entire eubacteria domain, and compromises made in hybridisation conditions due to simultaneous usage of multiple probes reduced the sensitivity of the PCR-ELISA test. The method was, however, found to be suitable for detecting predominant members of the intestinal flora. Applicability of the PCR-ELISA test could be further widened using primers with a more restricted specificity in the PCR step, as was demonstrated for the detection of Bifidobacterium with genus-specific primers. Advantages of the PCR-ELISA method include convenient performance and the possibility to test rapidly large amounts of samples with a multitude of probes.

Semiquantitative PCR analysis of Epstein-Barr virus DNA in clinical samples of patients with EBV-associated diseases

The laboratory diagnosis of primary and reactivated Epstein-Barr virus (EBV) infection is based on serologic methods in immunocompetent patients. However, in immunocompromised patients, serologic data are difficult to interpret and do not often correlate with clinical data. In order to find a useful and practical marker for diagnosis of EBV-related diseases, a polymerase chain reaction (PCR) assay was established for semiquantitative detection of EBV sequences. The method was based on a nested PCR, using primers of the virus capsid antigen p23 region and an endpoint dilution. This method was carried out on 68 plasma samples, 68 samples of peripheral blood mononuclear cells and 5 cerebrospinal fluid samples of 39 patients with various diseases to evaluate the EBV-genome copy number. Samples from patients suffering from infectious mononucleosis served as positive controls for active EBV infection. In 5 patients with infectious mononucleosis, high copy numbers of EBV genomes in peripheral blood mononuclear cells were detected within a range of 1,000-40,000 copies in 10(5) peripheral blood mononuclear cells. In contrast, samples from 19 latently infected persons either showed low copy numbers (10-100 in 10(5) peripheral blood mononuclear cells) or were EBV PCR negative. Comparable results were observed in seven renal transplant patients without any symptoms. The practical value of the semiquantitative detection of EBV DNA was demonstrated in three bone marrow transplant recipients. Two developed a lymphoproliferative disease associated with extremely high amounts of EBV DNA in plasma (16,000 and 50,000 copies/ml, respectively) and peripheral blood mononuclear cells (100,000 and 6.5 million copies in 10(5) peripheral blood mononuclear cells, respectively). The high EBV load in plasma and peripheral blood mononuclear cells was reduced dramatically after successful antiviral therapy in one case. The third bone marrow transplant recipient developed an EBV-induced transverse myelitis with an increased number of EBV-genome copies in peripheral blood mononuclear cells and EBV-positive cerebrospinal fluid samples. After combined antiviral and immune therapy, the EBV-genome copy numbers decreased and the patient recovered completely. These data demonstrate a good correlation between semiquantitative detection of EBV genomes and clinical findings. The method is recommended for the diagnosis of EBV-associated diseases in patients after transplantation, as well as for monitoring the response to therapy.

Quantitative PCR-ELAHA for the Determination of Retroviral Vector Transduction Efficiency

Current methods to detect transduction efficiency during the routine use of integrating retroviral vectors in gene therapy applications may require the use of radioactivity and usually rely upon subjective determination of the results. We have developed two competitive quantitative assays that use an enzyme-linked, amplicon hybridization assay (ELAHA) to detect the products of PCR-amplified regions of transgene from cells transduced with Moloney murine leukemia virus vectors. The quantitative assays (PCR-ELAHA) proved to be simple, rapid, and sensitive, avoiding the need for Southern hybridization, complex histochemical stains, or often subjective and time-consuming tissue culture and immunofluorescence assays. The PCR-ELAHA systems can rapidly detect proviral DNA from any retroviral vector carrying the common selective and marker genes neomycin phosphotransferase and green fluorescent protein, and the methods described are equally applicable to other sequences of interest, providing a cheaper alternative to the evolving real-time PCR methods. The results revealed the number of copies of retrovector provirus present per stably transduced cell using vectors containing either one or both qPCR targets.

RT-PCR and chemiluminescent ELISA for detection of enteroviruses

Reverse transcription followed by polymerase chain reaction amplification (RT-PCR) is now used commonly to detect the presence of enteric RNA viruses in environmental samples. A sensitive, non-isotopic microtitre plate hybridisation assay was developed and applied for detection of enteroviruses in environmental samples. Following reverse transcription, viral cDNA was labelled with digoxigenin (DIG)-dUTP during the PCR amplification step. The labelled PCR products were then hybridised with enterovirus-specific biotinylated oligonucleotide probe and captured in streptavidin-coated microtitre wells. Hybridised enteroviral PCR products were detected by an anti-digoxigenin peroxidase conjugate using either a colourimetric or a chemiluminescent substrate and automated measurement. Standard curves were established for poliovirus and other enteroviruses. The chemiluminescent assay was more sensitive than the colourimetric assay for detection of poliovirus, and was specific for enteroviruses. The chemiluminescent ELISA assay was used to confirm the presence of enteroviruses in environmental water samples.