Detection of single copies of Epstein-Barr virus in paraffin wax sections by non-radioactive in situ hybridisation

Tropism of subgroup J avian leukosis virus as detected by in situ hybridization

The HPRS-103 strain of avian retrovirus is the prototype of subgroup J avian leukosis virus (ALV-J) and causes myeloid leukosis in meat-type chickens. Using immunohistochemical detection of the viral groupspecific antigen (Gag) we have previously demonstrated that the induction of myeloid leukosis by ALV-J is associated with viral tropism for myelomonocytic cells. In this paper we describe an in situ hybridization (ISH) technique using digoxigenin (DIG)-labelled probes for detecting RNA transcripts in tissues from chickens infected with avian leukosis viruses (ALV) of subgroups J (HPRS-103 strain) and A (RAV-1 strain). Virus-specific RNA was detected mainly in the heart, kidney, proventriculus and adrenal in locations similar to those of the Gag protein. Viral gene expression could not be detected in the bone marrow or tumour tissues using this test. Higher levels of viral gene expression in the bursa of Fabricius infected with RAV-1, but not with HPRS-103, might help explain the inability of the latter virus to induce lymphoid leukosis.

Rapid determination of Epstein-Barr virus latent or lytic infection in single human cells using in situ hybridization

Epstein-Barr (EBV) virus is associated with malignancies such as lymphoma and carcinoma. Infection of cells with EBV may result in either lytic infection with production of viral particles, characterized by the presence of linear DNA forms, or latent infection, characterized by either episomal or integrated DNA forms. To examine whether the different lytic and latent EBV DNA forms can reliably be distinguished in single human cells, in situ hybridization was performed in EBV-positive cell lines. Immunocytochemistry and Southern blot analysis were performed supplementary to in situ hybridization. In latent infection, three in situ hybridization patterns were observed: large-disperse (episomal), small-punctate (integrated) and combined (both), signal types 1, 2 and 3 respectively. These were associated with expression of latent membrane protein 1, but not with Z fragment of Epstein-Barr replication activator or viral capsid antigen. In lytic infection, three additional in situ hybridization patterns were observed: nuclear membrane associated, bubble (filling up the nucleus) and spillover (covering the lysed cells) signals types 4, 5 and 6 respectively. Signal types 4 and 5 were associated with expression of latent membrane protein 1 and Z fragment of Epstein-Barr replication activator but not viral capsid antigen, whereas type 6 was associated with expression of viral capsid antigen only. Southern blot analysis confirmed these results; however, low copy numbers of integrated virus were often missed by Southern blot, confirming that in situ hybridization is more sensitive in determining the presence of all types of EBV DNA. In situ hybridization may prove useful in rapidly screening large series of tissue microarrays and other clinical specimens for the presence of lytic or latent EBV.

Detection of Epstein-Barr virus genomes in peripheral blood B cells from solid-organ transplant recipients by fluorescence in situ hybridization

Resolution of Epstein-Barr Virus (EBV) infection in pediatric solid-organ transplant recipients often leads to an asymptomatic carrier state characterized by a persistently elevated circulating EBV load that is 2 to 4 orders of magnitude greater than the load typical of healthy latently infected individuals. Elevated EBV loads in immunosuppressed individuals are associated with an increased risk for development of posttransplant lymphoproliferative disease. We have performed fluorescence in situ hybridization (FISH) studies with peripheral blood B cells from carriers of persistent EBV loads in order to directly quantitate the number of EBV genomes per infected cell. Patients were assigned to two groups on the basis of the level of the persistent load (low-load carriers, 8 to 200 genomes/10(5) peripheral blood lymphocytes; high-load carriers, >200 genomes/10(5) peripheral blood lymphocytes). FISH analysis revealed that the low-load carriers predominantly had circulating virus-infected cells harboring one or two genome copies/cell. High-load carriers also had cells harboring one or two genome copies/cell; in addition, however, they carried a distinct population of cells with high numbers of viral genome copies. The increased viral loads correlated with an increase in the frequency of cells containing high numbers of viral genomes. We conclude that low-load carriers possess EBV-infected cells that are in a state similar to normal latency, whereas high-load carriers possess two populations of virus-positive B cells, one of which carries an increased number of viral genomes per cell and is not typical of normal latency.

Assessment of the prognostic impact of the Epstein-Barr virus-encoded latent membrane protein-1 expression in Hodgkin's disease

We have examined expression of the Epstein-Barr virus (EBV) latent membrane protein-1 (LMP1) in the malignant Hodgkin and Reed-Sternberg (HRS) cells of Hodgkin's disease (HD) and its impact on response to treatment and on survival. Paraffin tissue from 100 adult immunocompetent patients with HD were analysed using immunohistochemistry to identify LMP1 expression. According to the Rye classification, 8% of patients had lymphocyte predominance (LP) subtype, 48% had nodular sclerosis (NS) disease, 37% were of the mixed cellularity (MC) subtype and 7% were of the lymphocyte depletion (LD) subtype. During the five year follow-up period 27 patients died and 74 patients achieved a complete remission. Patients with LD subtype were older (P = 0.03), less frequently achieved complete remission (P = 0.01), had shorter disease-free survival (P = 0.01) and overall survival (P = 0.002) compared with the other subtypes of HD. LMP1 expression was found in the tumour cells of 26% of cases of HD. LMP1 expression was less common in NS disease than in the other subtypes (P = 0.05), whereas an association between MC subtype and LMP1 expression was not found (P = 0.22). Using the log-rank test there were no differences in overall survival or disease-free survival based on EBV status either when all patients were analysed or when LD and LP subtypes were excluded. However, the presence of EBV was associated with significantly longer disease-free survival in the subgroup of patients </= 30 years old (P = 0.02) and in those patients </= 34 years old (P = 0.05). In contrast, there was a trend for shorter disease-free survival for EBV-positive patients in the subgroup > 35 years old, but this difference was not statistically significant (P = 0.11). A similar trend was observed in patients > 50 years old. Analysis of the impact of LMP1 expression in patients who had different stage and B symptoms status showed that expression of EBV was associated with longer disease-free survival (P = 0.019) in early stage (1 + 2) patients without B symptoms. Significant differences in the other subgroups based on EBV status was not found. Factors adversely affecting the likelihood to achieve a complete remission were: absence of LMP1 expression (OR 6.4, 95% Cl 1.07-38.5, P = 0.04), age (OR 1.68, 95%Cl 1.15-2.5, P = 0.007) and subtype of HD (OR 3.32, 95%Cl 1.11-9.94, P = 0.03). Age and subtype of HD had an independent impact on overall survival (P = 0.01). We conclude that expression of LMP1 in HRS cells has a favourable impact on prognosis for HD patients, but that this effect may be restricted to young adult patients and those with early stage disease.

Epstein-Barr virus early ribonucleic acids as a diagnostic adjunct for relapsed metastatic tumors in patients with cured primary undifferentiated nasopharyngeal carcinoma

PURPOSE

Epstein-Barr virus (EBV) has been consistently shown to be associated with undifferentiated nasopharyngeal carcinoma (NPC). In this article, the authors attempt to detect Epstein-Barr virus in distant relapsed metastatic sites in undifferentiated NPC patients with cured primary cancer.

MATERIALS AND METHODS

In situ hybridization (ISH) technique is a reliable method to detect EBV early RNAs (EBERs) within NPC cells. We used a nonisotopical ISH technique to examine the presence of EBERs in paraffin-embedded tissues obtained from 1 paired specimen of primary NPC and its metastatic counterpart at liver and 2 metastatic specimens of retroperitoneal lymph nodes and bone.

RESULTS

All the primary lesions and the metastatic tumors of NPC with undifferentiated histology contained EBERs that could be clearly detected in the nuclei of cancer cells.

CONCLUSIONS

This article shows that EBERs can be successfully detected in cells of the distant relapsed metastatic sites. These results suggest that this nonisotopical ISH method of EBERs can be potentially used to diagnose NPC patients developing distant relapsed metastatic lesions with cured primary cancer early. It can offer quick information as to institute suitable salvage chemotherapy for these patients.

Epstein-Barr virus meningoencephalitis with a lymphoma-like response in an immunocompetent host

We report the clinical and neuropathological findings in an immunocompetent 19-year-old patient with a fatal acute Epstein-Barr virus (EBV) meningoencephalitis and a lymphoma-like B-lymphocyte response. Our results suggest that an immunotoxic rather than direct viral neuronal invasion mediates brain damage in EBV encephalitis and rule out primary central nervous system lymphoma (PCNSL) in our patient. We discuss immunosuppression as a therapeutic option, because present strategies mainly consist of symptomatic therapy due to unclear pathogenesis and nonavailability of effective antiviral agents.

DNA viruses in the pathogenesis of sporadic chronic idiopathic intestinal pseudo-obstruction

BACKGROUND

Hereditary forms of chronic idiopathic intestinal pseudo-obstruction (CIIP) are well described but the aetiology of most cases of sporadic CIIP is unknown.

AIM

To determines whether herpes viruses can persist in the gastrointestinal tract, thereby implicating them in the pathogenesis of CIIP.

METHODS

Twenty one specimens of small and large intestine from 13 patients with CIIP (eight visceral myopathy, three visceral neuropathy, two undifferentiated), and 12 patients operated on for colorectal cancer (controls) were examined for evidence of Herpesvirus DNA (cytomegalovirus, Epstein-Barr virus (EBV), herpes simplex virus type 1, and varicella zoster virus) by nested polymerase chain reaction (PCR) and in situ DNA hybridisation (ISH) to localise signal to the muscularis propria or myenteric plexus.

RESULTS

Screening with nested PCR produced three patients with positive results. One patient with an inflammatory visceral neuropathy had EBV detected in the small intestine by PCR, and ISH demonstrated localisation to neurones in the myenteric plexus. A patient with a visceral myopathy had EBV DNA in both the small and large intestine; and one patient with a visceral neuropathy had small intestine positive for CMV DNA (both negative by ISH). No control tissue was positive for any virus.

CONCLUSIONS

In individual patients there appears to be evidence linking a viral aetiology to sporadic CIIP. The role of neurotropic viruses in acute and chronic motility disturbances needs further study.

Direct in situ transcriptase polymerase chain reaction for the detection of Enterovirus genome in liver tissues

Adolescent female mice were inoculated intraperitoneally with coxsackievirus B3 Nancy strain, sacrificed 3 and 5 days later and the livers harvested. A protocol for direct reverse transcriptase in situ PCR (RT-ISPCR) detection of enteroviral RNA in paraffin-embedded liver tissues was developed. The optimal conditions for the assay were determined. The best results were obtained when the tissue was fixed in formalin, prior to being embedded in paraffin, then cut in 5 micron thick sections, and mounted onto silanized slides. After deparaffination the slides were incubated in 1 microgram/m1 Proteinase K for 10 min and cDNA synthesis was carried out. For successful RT-ISPCR 40-50 cycles of amplification were necessary. The optimal concentrations of dNTP, primers and Taq Polymerase for RT-ISPCR were determined by serial dilution assays. Primers were selected from highly conserved sequences in the 5' non-coding region (5'NTR). To detect the viral RNA in the liver, digoxigenin-dUTP was incorporated during amplification, subsequently bound with an antidigoxigenin antibody conjugated to alkaline phosphatase (AP), followed by colorimetric detection with nitroblue tetrazolium salt (NBT) and 5-brom-4chloro-3indolyl-phosphate (BCIP). The result was a blue precipitate in the cytoplasm of hepatocytes from infected mice. Fibroblasts, endothelial cells, lymphocytes and the nuclei of hepatocytes were negative. Thus, RT-ISPCR is a specific method for the detection of enterovirus RNA in the hepatocytes of infected mice, and can be of use for the determination of EV liver disease in man.

Chemiluminescent in situ hybridization for the detection of cytomegalovirus DNA

A chemiluminescent in situ hybridization assay that could combine the sensitivity of chemiluminescent substrates, the specificity of digoxigenin-labeled probes, and the spatial morphological resolution and localization of the signal of the in situ hybridization was developed for the detection of cytomegalovirus (CMV) DNA. CMV DNA in cultured CMV-infected cells and in different clinical samples (tissue sections and cellular smears) was detected using digoxigenin-labeled probes constructed in our laboratory that were immunoenzymatically visualized employing anti-digoxigenin Fab fragments labeled with alkaline phosphatase and the chemiluminescent adamantil-1,2-dioxetane phenyl phosphate substrate for alkaline phosphatase. The luminescent signal from the hybrid formation was detected, analyzed, and measured with a high performance, low light level imaging luminograph apparatus connected to an optical microscope and to a personal computer for quantitative image analysis. Increasing values of emitted photons per second per infected cell, corresponding to the presence of hybridized CMV DNA, could be found in infected cells fixed at various times after infection, following the CMV replication cycle. When the assay was performed on different clinical samples from patients with acute CMV infections, CMV DNA was detected in all positive samples tested, both in cellular samples and in frozen and paraffin-embedded tissue sections, proving specific and sensitive. The chemiluminescent in situ hybridization assay developed in this work can be a useful tool for a sensitive and specific diagnosis of viral infection and can be easily adapted to detect and study any specific gene sequence inside the cells. The assay may also be promising for an estimation and quantification of nucleic acids present in tissue samples or cellular smears and for imaging gene expression in cells.

Criteria for consistent and high sensitivity of DNA in situ hybridization on paraffin sections: optimal proteolytic enzyme digestion

It is technically challenging for the detection of target DNA in low abundancy, such as viral DNA sequences in latently infected cells by nonisotopic in situ hybridization (ISH). Consistent result is even more difficult to achieve on routine paraffin sections. Proteolytic enzyme digestion is most critical for both consistency and sensitivity of the technique. We here have investigated the effect of enzyme digestion on cell morphology, protein and DNA reduction, and hybridization efficiency. The results demonstrated that enzyme digestion improves efficiency of ISH through a process involving partial DNA purification on sections. There is a clear relationship between proteolytic enzyme digestion, morphology changes, and hybridization efficiency. Although detection of DNA sequences in abundance can be achieved within a relatively wide range of digestion levels, maximum hybridization efficiency was always related to the cells, which showed morphology of nuclear swollen, weak homogeneous chromatin staining with hematoxylin and loss of visible nuclear membrane. Detection of viral DNA in low copy number critically depends on the creation of the morphologic changes by enzyme digestion. The morphological changes would therefore serve as important criteria for optimal digestion, result interpretation, and comparison.

Epstein-Barr virus in Hodgkin disease. Relation to age and subtype

BACKGROUND

Epstein-Barr virus (EBV) has been associated with Hodgkin disease (HD), but its relationship to the age of the patients and the histologic subtype is not well defined. The possibility that other lymphotropic herpesviruses, such as cytomegalovirus (CMV) and human herpesvirus type 6 (HHV-6) could be involved in the pathogenesis of HD is also unclear.

METHODS

Paraffin-embedded material from 77 cases of HD was studied. This consisted of 24 specimens from children (mean age, 11.4 years), 36 from young adults (mean age, 28.8 years), and 17 from older adults (mean age, 53.8 years). EBV was detected in Hodgkin and Reed-Sternberg cells (HR-S) by a sensitive in situ hybridization technique based on the detection of Epstein-Barr-encoded RNA. Viral activity was subsequently demonstrated in HR-S cells by using monoclonal antibodies to EBV latent membrane protein.

RESULTS

EBV was found in a total of 25 of 77 cases (32%). There was no significant difference in EBV positivity between the different age groups. However, the prevalence of EBV varied between different subtypes: 68% of mixed cellularity cases were found to be positive by contrast with 24% nodular sclerosis, 0% lymphocyte predominant, and 14% lymphocyte depleted. Analysis of the histologic reports of a further 783 cases of HD to determine the age distribution of the different subtypes revealed an absence of an older adult second peak in the age distribution curve. In situ hybridization for CMV and HHV-6 was negative in all cases.

CONCLUSIONS

It was concluded that EBV is predominantly associated with mixed cellularity HD, and there is no correlation with the age of the patient.

Detection of Epstein-Barr virus in a case of undifferentiated nasopharyngeal carcinoma by in situ hybridization with digoxigenin-labelled PCR-generated probes

A case of nasopharyngeal carcinoma is presented. Epstein-Barr viral genome was identified in the neoplastic cells by in situ hybridization with digoxigenin-labelled polymerase chain reaction-generated probes. We report the development of this technique in paraffin-embedded sections and propose that such identification may prove valuable for the diagnosis of this tumour in routine material.

Detection of Epstein-Barr virus in Reed-Sternberg cells of Hodgkin's disease arising in children

Nonisotopic in situ hybridization has been used to investigate the role of Epstein-Barr virus (EBV) in the aetiology of pediatric Hodgkin's disease. Sections from 24 cases arising in children under the age of 15 years were hybridised with digoxigenin-labelled probes for both EBV and cytomegalovirus, and reactive sites were identified by a sensitive three-layer immunoperoxidase technique. EBV was identified in Reed-Sternberg and mononuclear Hodgkin's cells in five samples (21%). No samples were positive when the cytomegalovirus probe was employed. The specific identification of EBV in the malignant cells of Hodgkin's disease arising in children lends further support for a role of EBV in the aetiology of this disorder.

Epstein Barr virus (EBV) encoded small RNAs: targets for detection by in situ hybridisation with oligonucleotide probes

AIMS

To develop a rapid, sensitive, and specific non-isotopic in situ hybridisation (NISH) procedure for the detection of Epstein-Barr virus in formalin fixed, paraffin wax embedded tissues.

METHODS

Two low molecular weight RNAs, designated EBER-1 and EBER-2 (Epstein-Barr encoded RNA), were used: cells latently infected with EBV secrete large amounts of EBERs. The method uses digoxigenin labelled anti-sense oligonucleotides, corresponding to sequences in EBER-1 and EBER-2.

RESULTS

The use of these probes, in conjunction with high temperature microwave denaturation, ensured that the technique was considerably more sensitive than other in situ hybridisation techniques for detecting EBV. Furthermore, the hybridisation signal was morphologically distinct in that only the nucleus and not the nucleolus give a positive signal. No cross-hybridisation was observed with cells infected with other lymphotropic herpes viruses.

CONCLUSION

The sensitivity, simplicity, and rapidity of this technique make it ideal for diagnostic use, and for studies investigating the role of this virus in neoplastic disease.

Presence of Epstein-Barr virus in Hodgkin's disease is not exclusive to Reed-Sternberg cells

Thirty-three cases of Hodgkin's disease (HD) have been studied for the presence of Epstein-Barr virus (EBV) using a novel nonisotopic in situ hybridization procedure, based on the detection of Epstein-Barr encoded RNAs with oligonucleotide probes. An intense and morphologically distinct nuclear staining, sparing the nucleolus was seen in a total of 12 cases (36%). In six of these cases, the signal was located to the Hodgkin and Reed-Sternberg cells (HR-S); in the other six positive cases, the signal was observed only in the non-neoplastic small lymphocytes. These lymphocytes were few in number and immunocytochemistry results were consistent with a B-cell phenotype. The presence of EBV in those cases characterized by nuclear staining of small lymphocytes was confirmed by the polymerase chain reaction (PCR) analysis. The authors report the detection of EBV in small lymphocytes in HD by in situ hybridization and discuss the implications of these findings in relation to the proposed etiologic association between EBV and HD.

Persistence of Epstein-Barr virus in Reed-Sternberg cells throughout the course of Hodgkin's disease

Non-isotopic in situ hybridization employing digoxigenin-labelled DNA probes has been used to localize Epstein-Barr virus (EBV) in 55 cases of Hodgkin's disease (HD). The virus was found in Reed-Sternberg (RS) and mononuclear Hodgkin's cells in nine patients (16 per cent). Further samples taken at different times from three patients also showed the presence of EBV in the malignant cell population. Estimations of the number of EBV genomes present per cell suggested wide variations between different patients, but relatively constant amounts in different samples from the same patient. These findings are compatible with a stable infection of the neoplastic cells and support the notion that EBV may play a role in the development of HD in these patients. We also found evidence for the presence of EBV in a small percentage of non-neoplastic cells in 8 of the 55 samples. This suggests that isolation of EBV from HD tissue does not always signify a pathogenetic role for the virus. Furthermore, it is apparent that a high percentage of HD tissues do not contain demonstrable EBV, and the virus is therefore unlikely to be a causative agent for all cases of HD.