A rapid monitoring system of human herpesviruses reactivation by LightCycler in stem cell transplantation

Persistent low level Epstein-Barr virus DNAemia in childhood cancer survivors

BACKGROUND

Clinical observation of Epstein-Barr virus (EBV) status has not documented in childhood cancer survivors (CCSs) sustaining long-term remission of malignant diseases. Thus, the aim of this study was to evaluate the EBV status in children with various malignant diseases after they completed their treatments.

PATIENTS AND METHODS

Thirty consecutive children with various malignant diseases previously received treatment at the University of Tsukuba Hospital. Nine cases had acute lymphoblastic leukemia (ALL), 10 had solid tumors, 4 had lymphoma, 4 had CNS tumors, and 3 had acute myeloid leukemia (AML). EBV DNA in 328 whole blood samples were monitored by real-time QPCR for all cases after treatment. Clinical records and laboratory data were also reviewed.

RESULTS

There were 6/30 (20%) cases with continuous detection of EBV DNA while there were 24/30 (80%) cases without continuous EBV DNA. EBV DNAemia was persistently observed in 4/9 (44.4%) cases with ALL and in 2/4 (50%) cases with lymphoma. Persistent EBV DNAemia can be observed for >5 years without any EBV associated symptoms or diseases.

CONCLUSIONS

Childhood cancer survivors have persistent EBV DNAemia more frequently, which is thought to be observed in cases with ALL and lymphoma with higher tendency for >5 years after treatment. Persistent EBV DNAemia is frequent in CCSs aged 5-10 years. Any immunological alteration is speculative in a pathophysiology of persistent EBV DNAemia.

(-)-Epigallocatechin-3-gallate inhibition of Epstein-Barr virus spontaneous lytic infection involves ERK1/2 and PI3-K/Akt signaling in EBV-positive cells

Epstein-Barr virus (EBV) reactivation into the lytic cycle plays certain roles in the development of EBV-associated diseases, including nasopharyngeal carcinoma and lymphoma. In this study, we investigated the effects of the tea polyphenol (-)-epigallocatechin-3-gallate (EGCG) on EBV spontaneous lytic infection and the mechanism(s) involved in EBV-positive cells. We found that EGCG could effectively inhibit the constitutive lytic infection of EBV at the DNA, gene transcription and protein levels by decreasing the phosphorylation and activation of extracellular signal-regulated kinase 1/2 (ERK1/2) and Akt. By using cellular signaling pathway-specific inhibitors, we also explored the signaling mechanisms underlying the inhibitory effects of EGCG on EBV spontaneous lytic infection in cell models. Results show that specific inhibitors of Mitogen-Activated Protein Kinase Kinase (MEK) (PD98059) and phosphatidylinositol 3-kinase [PI3-K (LY294002)] markedly downregulated gene transcription and expression of BZLF1 and BMRF1 indicating that the MEK/ERK1/2 and PI3-K/Akt pathways are involved in the EBV spontaneous lytic cycle cascade. Therefore, one of the mechanisms by which EGCG inhibits EBV spontaneous lytic infection appears to involve the suppression of the activation of MEK/ERK1/2 and PI3-K/Akt signaling.

Optimization of the Sybr Green real time PCR for the detection of Human Herpes Virus type 6 (HHV-6)

HHV-6 is the etiological agent of Exanthem subitum which is considered the sixth most frequent disease in infancy. In immuno-compromised hosts, reactivation of latent HHV-6 infection may cause severe acute disease. We developed a Sybr Green Real Time PCR for HHV-6 and compared the results with nested conventional PCR. A 214 pb PCR derived fragment was cloned using pGEM-T easy from Promega system. Subsequently, serial dilutions were made in a pool of negative leucocytes from 10-6 ng/microL (equivalent to 2465.8 molecules/microL) to 10-9 (equivalent to 2.46 molecules/microL). Dilutions of the plasmid were amplified by Sybr Green Real Time PCR, using primers HHV3 (5' TTG TGC GGG TCC GTT CCC ATC ATA 3)'and HHV4 (5' TCG GGA TAG AAA AAC CTA ATC CCT 3') and by conventional nested PCR using primers HHV1 (outer): 5'CAA TGC TTT TCT AGC CGC CTC TTC 3'; HHV2 (outer): 5' ACA TCT ATA ATT TTA GAC GAT CCC 3'; HHV3 (inner) and HHV4 (inner) 3'. The detection threshold was determined by plasmid serial dilutions. Threshold for Sybr Green real time PCR was 24.6 molecules/microL and for the nested PCR was 2.46 molecules/microL. We chose the Real Time PCR for diagnosing and quantifying HHV-6 DNA from samples using the new Sybr Green chemistry due to its sensitivity and lower risk of contamination.

Detection and typing of human herpesvirus 6 by molecular methods in specimens from patients diagnosed with encephalitis or meningitis

Human herpesvirus 6 (HHV-6) was detected in specimens from patients hospitalized with symptoms of encephalitis or meningitis. A real-time PCR assay was developed which has a linear dynamic range of 5 to 5 x 10(6) copies of HHV-6 and a sensitivity of five gene copies per reaction. While the assay detects both subtypes, HHV-6A and HHV-6B, it is specific and does not cross-react with a selected specificity panel. A total of 1,482 patient specimens, which were collected between 2003 and 2007, were tested; 26 specimens from 24 patients were found to be positive for HHV-6 by real-time PCR. The HHV-6 detection rate in this population was therefore 1.75%. The majority of the specimens tested (>95%) were cerebrospinal fluid (CSF) specimens. We were able to type 20 of the 26 positive specimens by conventional PCR and sequence analysis; all were HHV-6B. Forty-two percent of the patients were 3 years of age or younger, which may indicate a primary infection in these patients. Given the ages of the remaining patients (from 4 to 81 years), their infections were most probably due to virus reactivations. Where information was available, symptoms of patients included fever (71%), altered mental status (67%), and abnormal CSF profile (75%). Fifty percent of patients of 3 years of age or younger suffered from seizures. The detection of HHV-6 in specimens from patients diagnosed with encephalitis or meningitis, in the absence of a positive PCR result for other agents, strongly suggests a role for HHV-6 in the pathogenesis of these central nervous system diseases.

Detection of β-herpesviruses in allogenic stem cell recipients by quantitative real-time PCR

The aim of this study was to investigate the clinical impact of reactivation of human herpes virus-6 (HHV-6) and HHV-7 infections in stem cell transplantation recipients, and to examine a possible increase in virulence of the two roseoloviruses when a reactivation of CMV (HHV-5) simultaneously occurs. For this purpose, quantitative real-time PCR systems were developed to assess the viral load of CMV, HHV-6, or HHV-7 in the plasma of haematopoetic stem cell recipients. One hundred and ninety-eight plasma samples from 37 patients who underwent allogeneic stem cell transplantation were tested for CMV, HHV-6, and HHV-7 by a 5'-exonuclease (TaqMan) quantitative real-time PCR. The CMV load obtained by the real-time PCR assay was compared retrospectively with results generated previously with a commercially available test (COBAS AMPLICOR CMV MONITOR Test, Roche). The results suggest that CMV and HHV-6 may be associated with post-transplantation end-organ disease, while HHV-7 reactivation had no impact on the patients included in this study. No evidence for a potential interaction of the roseoloviruses and CMV infections was found.

Transcriptional profiling of Epstein-Barr virus (EBV) genes and host cellular genes in nasal NK/T-cell lymphoma and chronic active EBV infection

Nasal NK/T-cell lymphoma is an aggressive subtype of non-Hodgkin lymphoma (NHL) that is closely associated with Epstein–Barr virus (EBV). The clonal expansion of EBV-infected NK or T cells is also seen in patients with chronic active EBV (CAEBV) infection, suggesting that two diseases might share a partially similar mechanism by which EBV affects host cellular gene expression. To understand the pathogenesis of EBV-associated NK/T-cell lymphoproliferative disorders (LPD) and design new therapies, we employed a novel EBV DNA microarray to compare patterns of EBV expression in six cell lines established from EBV-associated NK/T-cell LPD. We found that expression of BZLF1, which encodes the immediate-early gene product Zta, was expressed in SNK/T cells and the expression levels were preferentially high in cell lines from CAEBV infection. We also analyzsd the gene expression patterns of host cellular genes using a human oligonucleotide DNA microarray. We identified a subset of pathogenically and clinically relevant host cellular genes, including TNFRSF10D, CDK2, HSPCA, IL12A as a common molecular biological properties of EBV-associated NK/T-cell LPD and a subset of genes, such as PDCD4 as a putative contributor for disease progression. This study describes a novel approach from the aspects of viral and host gene expression, which could identify novel therapeutic targets in EBV-associated NK/T-cell LPD.

Multiplex real-time PCR assay for simultaneous quantitation of human cytomegalovirus and herpesvirus-6 in polymorphonuclear and mononuclear cells of transplant recipients

Human cytomegalovirus (HCMV) and human herpesvirus-6 (HHV-6) are two closely related viruses, which belong to the Herpesviridae family. Following primary infection, they are thought to persist for life as latent forms in mononuclear cells. HCMV and HHV-6 can cause considerable morbidity in immunocompromised individuals, such as transplant patients. A sensitive and specific LightCycler multiplex real-time PCR assay based on fluorescence energy transfer (known as FRET) was developed. This assay, by using two sets of hybridization probes specific for HHV-6 (A and B) and HCMV, can differentiate reliably and quantify simultaneously both viruses in order to diagnose reactivation processes. The assay was optimized and the lower limit of detection for both viruses was determined to be 10 viral genome copies per reaction. Both viruses were quantified in 83 peripheral blood mononuclear cells (PBMCs) and 87 polymorphonuclear leukocytes (PMNLs) collected from 32 transplant recipients. This multiplex real-time quantitative PCR was finally compared with two other quantitation and detection assays used daily in laboratory (PCR DIG detection and antigenemia for HCMV, TaqMan Assay for HHV-6). This technique can be useful for the differentiation and quantitation of HCMV and HHV-6 for monitoring transplant patients.

Comparison of the SYBR Green and the hybridization probe format for real-time PCR detection of HHV-6

A comparative study was conducted of a novel real-time quantitative PCR test (LightCycler System) with FastStart DNA Master(PLUS) SYBR Green I dye to detect DNA of human herpes virus 6 (HHV-6). Results were compared with those of a real-time quantitative PCR with hybridization probe (HP) formats using the fluorescence resonance energy transfer method, and with those of a single qualitative PCR test. The detection limit of the test with SYBR Green I dye was 20 copies of the virus, similar to that of the other two tests. The reproducibility was satisfactory. The new test has the same advantages as real-time PCR with HP formats and offers a greater versatility at lower cost.

Real-time PCR in clinical microbiology: applications for routine laboratory testing

Real-time PCR has revolutionized the way clinical microbiology laboratories diagnose many human microbial infections. This testing method combines PCR chemistry with fluorescent probe detection of amplified product in the same reaction vessel. In general, both PCR and amplified product detection are completed in an hour or less, which is considerably faster than conventional PCR detection methods. Real-time PCR assays provide sensitivity and specificity equivalent to that of conventional PCR combined with Southern blot analysis, and since amplification and detection steps are performed in the same closed vessel, the risk of releasing amplified nucleic acids into the environment is negligible. The combination of excellent sensitivity and specificity, low contamination risk, and speed has made real-time PCR technology an appealing alternative to culture- or immunoassay-based testing methods for diagnosing many infectious diseases. This review focuses on the application of real-time PCR in the clinical microbiology laboratory.

Estimating immunoregulatory gene networks in human herpesvirus type 6-infected T cells

The immune response to viral infection involves complex network of dynamic gene and protein interactions. We present here the dynamic gene network of the host immune response during human herpesvirus type 6 (HHV-6) infection in an adult T-cell leukemia cell line. Using a pathway-focused oligonucleotide DNA microarray, we found a possible association between chemokine genes regulating Th1/Th2 balance and genes regulating T-cell proliferation during HHV-6B infection. Gene network analysis using an integrated comprehensive workbench, VoyaGene, revealed that a gene encoding a TEC-family kinase, ITK, might be a putative modulator in the host immune response against HHV-6B infection. We conclude that Th2-dominated inflammatory reaction in host cells may play an important role in HHV-6B-infected T cells, thereby suggesting the possibility that ITK might be a therapeutic target in diseases related to dysregulation of Th1/Th2 balance. This study describes a novel approach to find genes related with the complex host-virus interaction using microarray data employing the Bayesian statistical framework.

Transcriptional profiling of human herpesvirus type B (HHV-6B) in an adult T cell leukemia cell line as in vitro model for persistent infection

Human herpesvirus 6 (HHV-6), which is present in more than 90% of the human, is known to cause infectious diseases in immuno-compromised patients, e.g., transplant patients. To clarify the possible role of the pattern of expression of HHV-6 genes in various types of HHV-6B infection, we sought to determine whether or not viral DNA microarray could be used for detailed characterization of viral transcription using a HHV-6B DNA microarray that contains 97 known open reading frames of HHV-6B. A subset of genes are preferentially expressed in persistent infection: U16 (IE-B, transactivator, US22 gene family), U18 (IE-B, homolog to HCMV IE glycoprotein), U20 (glycoprotein), U27 (DNA polymerase processivity transactivator), U82 (gL, gH accessory protein), U83 (chemokine), U85 (OX-2 homology, glycoprotein), U90 (IE-A), and U94 (transactivator), respectively. Although the function of each HHV-6B is not fully understood, our study suggests that comprehensive analysis of HHV-6B transcription is useful not only to clarify the pathogenesis of the virus but also to develop new strategies for anti-viral drugs.

Update on human herpesvirus 6 biology, clinical features, and therapy

Human herpesvirus 6 (HHV-6) is a betaherpesvirus that is closely related to human cytomegalovirus. It was discovered in 1986, and HHV-6 literature has expanded considerably in the past 10 years. We here present an up-to-date and complete overview of the recent developments concerning HHV-6 biological features, clinical associations, and therapeutic approaches. HHV-6 gene expression regulation and gene products have been systematically characterized, and the multiple interactions between HHV-6 and the host immune system have been explored. Moreover, the discovery of the cellular receptor for HHV-6, CD46, has shed a new light on HHV-6 cell tropism. Furthermore, the in vitro interactions between HHV-6 and other viruses, particularly human immunodeficiency virus, and their relevance for the in vivo situation are discussed, as well as the transactivating capacities of several HHV-6 proteins. The insight into the clinical spectrum of HHV-6 is still evolving and, apart from being recognized as a major pathogen in transplant recipients (as exemplified by the rising number of prospective clinical studies), its role in central nervous system disease has become increasingly apparent. Finally, we present an overview of therapeutic options for HHV-6 therapy (including modes of action and resistance mechanisms).

Differentiation and quantitation of human herpesviruses 6A, 6B and 7 by real-time PCR

The beta-herpesviruses cause considerable morbidity in immunocompromised individuals, such as transplant patients. Most notably within this group is human cytomegalovirus, although HHV-6 and -7 are a growing concern. Identifying HHV-6 and -7 as the cause of post-transplant illness can be challenging due to high seroprevalence and latency properties associated with these human herpesviruses. We have developed a sensitive and specific real-time PCR assay, which can differentiate reliably and quantify HHV-6A, -6B and -7. Using two sets of hybridization probes specific for HHV-6A or -6B and HHV-7, the assay reliably differentiates the three viruses using melting curve analysis. The lower limit of detection for all three viruses was determined to be ten viral genomes. This real-time PCR assay will be useful for differentiation and quantitation of HHV-6A, -6B and -7, especially for monitoring transplant patients.