Peptide nucleic acid-based in situ hybridization assay for detection of parvovirus B19 nucleic acids

Synthetic genetic polymers: advances and applications

Advances and applications of synthetic genetic polymers (xeno-nucleic acids) are reviewed in this article. The types of synthetic genetic polymers are summarized. The basic properties of them are elaborated and their technical applications are presented. Challenges and prospects of synthetic genetic polymers are discussed.

A new colorimetric peptide nucleic acid-based assay for the specific detection of bacteria

AIM

Developments on synthetic molecules, such as peptide nucleic acid (PNA), make FISH procedures more robust for microbial identification. Fluorochromes use might hinder a broader implementation of PNA-FISH, but colorimetric applications are inexistent so far.

METHODS

A biotin-labeled eubacteria probe was used to develop a colorimetric PNA-in situ hybridization (ISH) assay. An enzymatic-conjugate, targeting biotin, was introduced. The procedure was optimized and evaluated regarding sensitivity, specificity and detection limit.

RESULTS

RESULTS have shown strong ISH signals. The method was specific, but permeabilization problems were observed for Gram-positive bacteria. Detection limit was 5 × 10(7) CFU/ml, limiting current applications to pre-enriched samples.

CONCLUSION

The PNA-ISH procedure described here is a simple alternative to other detection methods, and is also the base for the development of other PNA colorimetric systems.

Parvovirus B19 Achievements and Challenges

Parvovirus B19 is a widespread human pathogenic virus, member of the Erythrovirus genus in the Parvoviridae family. Infection can be associated with an ample range of pathologies and clinical manifestations, whose characteristics and outcomes depend on the interplay between the pathogenetic potential of the virus, its adaptation to different cellular environments, and the physiological and immune status of the infected individuals. The scope of this review is the advances in knowledge on the biological characteristics of the virus and of virus-host relationships; in particular, the interactions of the virus with different cellular environments in terms of tropism and ability to achieve a productive replicative cycle, or, on the contrary, to establish persistence; the consequences of infection in terms of interference with the cell physiology; the process of recognition of the virus by the innate or adaptive immune system, hence the role of the immune system in controlling the infection or in the development of clinical manifestations. Linked to these issues is the continuous effort to develop better diagnostic algorithms and methods and the need for development of prophylactic and therapeutic options for B19V infections.

Parvovirus B19 is a bystander in adult myocarditis

BACKGROUND

The genomic DNA of parvovirus B19, a small single-stranded DNA virus of the genus Erythrovirus, has been shown to persist in solid tissues of constitutionally healthy, immunocompetent individuals. Despite these data, many case reports and series have linked the presence of parvovirus B19 genomic DNA, detected through nucleic acid amplification testing, with myocarditis and cardiomyopathy. Herein, we use multiple tools to better assess the relationship between parvovirus B19 and myocarditis and cardiomyopathy.

METHODS

Nucleic acid amplification testing, immunohistochemistry, in situ hybridization, and electron microscopy were used to assess the location and activity of parvovirus B19 in cases of myocarditis and in cases with no significant cardiac disease.

RESULTS

Nucleic acid amplification testing for parvovirus B19 genomic DNA was positive in 73% of patients with myocarditis/cardiomyopathy and in 26% of patients with no significant disease. In situ hybridization and immunohistochemistry showed that, in cases with amplifiable parvovirus B19 DNA, parvovirus B19 genomic DNA and viral protein production were present in rare mononuclear cells.

CONCLUSIONS

In a majority of cases of myocarditis and a significant number of otherwise normal hearts, nucleic acid amplification testing detected persistent parvovirus B19 genomic DNA that did not play a significant pathogenic role. The source of parvovirus B19 DNA appeared to be interstitial mononuclear inflammatory cells and not myocardial or endothelial cells. Therefore, nucleic acid amplification testing alone is not diagnostically helpful for determining the etiology of adult myocarditis.

Diagnosis of fetal parvovirus B19 infection: value of virological assays in fetal specimens

OBJECTIVE

The purpose of our work was to examine the most reliable laboratory diagnosis of fetal parvovirus B19 infection in hydropic fetuses by evaluating the most appropriate clinical sample and laboratory test.

DESIGN

B19 DNA detection in fetal samples and serological signs of B19 infection in the respective mothers. Samples collected between January 2000 and July 2008.

SETTING

Microbiology, University of Bologna, Bologna, Italy.

SAMPLES

One hundred thirty-five fetal samples (58 fetal cord blood and 77 amniotic fluid samples) and 109 serum samples collected from 109 pregnant women.

METHODS

Validated and certified in situ hybridisation assay (ISH) and polymerase chain reaction-enzyme-linked immunosorbent assay (PCR-ELISA) were performed on fetal samples to detect B19 DNA. B19-specific antibodies were investigated in maternal serum samples by a commercial enzyme immunoassay.

MAIN OUTCOME MEASURES

Parvovirus B19 DNA detection in fetal specimens was analysed in relation to maternal serological signs of infection.

RESULTS

Parvovirus B19 DNA was detected in 22.41% of fetal cord blood and 36.36% of amniotic fluid samples. A statistically significant difference was found between DNA detection by ISH (23.70%) and PCR-ELISA (14.81%) (P= 0.004). Only 11.76% of fetuses with virological diagnosis of B19 infection were from women with serological signs of acute/recent B19 infection.

CONCLUSIONS

Diagnosis of fetal parvovirus B19 infection cannot always rely on maternal serological investigations but rather on the virological analysis of fetal samples. Both fetal cord blood and amniotic fluid samples are suitable for diagnosis, but the detection of B19 DNA in the cells of amniotic fluid samples by ISH proved to be the most reliable diagnostic system.

A FRET-based assay for characterization of alternative splicing events using peptide nucleic acid fluorescence in situ hybridization

We describe a quantitative method for detecting RNA alternative splicing variants that combines in situ hybridization of fluorescently labeled peptide nucleic acid (PNA) probes with confocal microscopy Förster resonance energy transfer (FRET). The use of PNA probes complementary to sequences flanking a given splice junction allows to specifically quantify, within the cell, the RNA isoform generating such splice junction by FRET measure. As a proof of concept we analyzed two alternative splicing events originating from lymphocyte antigen 6 (LY6) complex, locus G5B (LY6G5B) pre-mRNA. These are characterized by the removal of the first intron (Fully Spliced Isoform, FSI) or by retention of such intron (Intron-Retained Isoform, IRI). The use of PNA probe pairs labeled with donor (Cy3) and acceptor (Cy5) fluorophores, suitable to FRET, flanking FSI and IRI specific splice junctions specifically detected both mRNA isoforms in HeLa cells. We have observed that the method works efficiently with probes 5–11 nt apart. The data supports that this FRET-based PNA fluorescence in situ hybridization (FP–FISH) method offers a conceptually new approach for characterizing at the subcellular level not only splice variant isoform structure, location and dynamics but also potentially a wide variety of close range RNA–RNA interactions.

Parvovirus b19 infection localized in the intestinal mucosa and associated with severe inflammatory bowel disease

Infection by human parvovirus B19 is widespread and can be associated with a wide range of different pathologies and clinical manifestations. We provide the first evidence of localization of an active parvovirus B19 infection in the intestinal mucosa and its association with a severe inflammatory bowel disease, characterized by duodenal villous atrophy with increased intraepithelial lymphocytes and inflammatory infiltrates in the colonic mucosa. Virus in the intestinal mucosa was detected in cells of the inflammatory infiltrate, identified as T lymphocytes and selectively localized in sites of active tissue degeneration.

Human erythrovirus B19 and blood transfusion ? an update

Erythrovirus (parvovirus) B19 (B19) is a common human pathogen. It is a non-enveloped single-strand DNA virus packaging its genome in small tight capsids consisting of viral VP1 and VP2 proteins. It is now accepted that B19 is a relatively quickly evolving virus having diverged in several genetic variants recently identified. The main route of B19 transmission is respiratory, with a majority of infections occurring during childhood and manifesting as erythema infectiousum. B19 can also be transmitted vertically and via blood transfusion and organ transplantation. The majority of adult populations show immunological evidence of previous exposure to B19. Although the immune response is able to clear infection and provide life-long protection against B19, recent data suggest that in some, if not the majority, of individuals the acute phase of infection is followed by viral persistence in the blood or other tissues regardless of the host's immunocompetence. Transmission of B19 by blood and blood products and its resistance to common viral inactivation methods raises several blood safety questions, still unanswered. The diversity of B19 strains and the ability of the virus to persist in the presence of specific antibodies raise the issue of transmissibility by transfusion not so much to immunocompetent recipients but rather to the large proportion of recipients in whom there is some degree of immunodeficiency. The ability of the virus to reactivate in immunodeficient recipients may create difficulties in differentiating between transfusion transmission and reactivation.

PNA-based probe for quantitative chemiluminescent in situ hybridisation imaging of cellular parvovirus B19 replication kinetics

To allow the ultrasensitive localization and the quantitative detection of parvovirus B19 nucleic acids in single infected cells at various times post-infection, a peptide nucleic acid (PNA)-based in situ hybridisation (ISH) assay with chemiluminescent detection has been developed. The assay is based on the use of a biotin-labelled PNA probe detected by a streptavidin-linked alkaline phosphatase and a chemiluminescent dioxetane phosphate derivative substrate. The luminescent signal was quantified and imaged with an ultrasensitive nitrogen-cooled CCD camera connected to an epifluorescence microscope. The assay was used to analyze the parvovirus B19 infection process in cell cultures and to quantify the amount of viral nucleic acids at different times after infection. The chemiluminescent ISH-PNA assay is characterized by high resolution providing a sharp localization of B19 nucleic acids within single cells, with higher sensitivity with respect to conventional colorimetric ISH detection. Thanks to the high detectability and wide linear range of chemiluminescence detection, an objective evaluation of the percentage of infected cells, which reached its maximum at 24 h after infection, following a B19 virus infectious cycle could be accurately evaluated. Chemiluminescence detection also allowed the quantitative analysis of viral nucleic acids at the single-cell level, showing a continuous increase of the content of viral nucleic acids in infected cells with time after infection. The developed chemiluminescent ISH-PNA assay could thus represent a potent tool for the assessment of viral infections and for the quantitative evaluation of the virus nucleic acid load of infected cells in virus studies and diagnostics.