Quantitative PCR for human herpesviruses 6 and 7

Large-scale analysis of viral nucleic acid spectrum in temporal lobe epilepsy biopsies

OBJECTIVE

Chronic inflammatory processes are important promotors of temporal lobe epilepsy (TLE) development. Based on human herpesvirus 6 (HHV-6) DNA detection in brain tissue from patients with TLE, an association of persistent viral infection with TLE has been discussed. Individual studies reported increased HHV-6 DNA in patients with clinical signs of previous inflammatory brain reaction, that is, febrile seizures or meningoencephalitis. However, detection rates vary considerably between different studies. Here we performed a large-scale analysis of viral DNA/RNA spectrum in high-quality TLE biopsies. In addition to all Herpesviridae, we addressed potentially relevant neurotropic RNA viruses.

METHODS

DNA and RNA were extracted from 346 fresh-frozen tissue samples removed by epilepsy surgery. Real-time polymerase chain reaction (PCR) and nested PCR were performed for Herpesviridae and RNA viruses, respectively. Clinical data were analyzed for earlier signs of inflammatory brain reactions. Fresh-frozen hippocampal tissue samples from patients without chronic central nervous system (CNS) disease served as controls (n = 62). Seven previous PCR studies with overall 178 TLE patients were additionally analyzed regarding a correlation of clinical parameters and HHV-6 detection.

RESULTS

PCR revealed HHV-6B DNA in 34 specimens (9.8%) from TLE patients. HHV-6B DNA was also present in eight control samples (12.9%; p > 0.05), but showed a lower virus concentration (p < 0.001). Other herpesviruses and RNA viruses were virtually absent. In patients with clinical signs of previous brain inflammation, HHV-6B DNA was observed in 15.0%, whereas only 6.3% of the samples from patients without febrile seizures or meningoencephalitis were positive for HHV-6B DNA (p < 0.05). A meta-analysis of the eight HHV-6 PCR studies revealed similar results.

SIGNIFICANCE

This biopsy-based study shows no differences in frequency of HHV-6B DNA detection between TLE patients and controls. These results do not support the hypothesis of a persistent HHV-6B infection as a major pathogenetic factor in TLE. However, the higher virus load in TLE patients and the increased detection rate of HHV-6B DNA in patients with previous inflammatory brain reactions require further investigations.

Mini review article. Human herpesvirus-6 and the etiology of multiple sclerosis: a literature review

Background: There is no consensus in the literature on the role of human herpes virus-6 (HHV-6) in multiple sclerosis (MS) onset or progression.

Objective: We evaluated a possible role for HHV-6 in MS onset and progression.

Methods: We conducted a literature search of PubMed and Google scholar with the following search terms: (“multiple sclerosis” OR “MS”) and (“Human Herpes Virus-6” OR “HHV-6”).

Results: A total 21 publications were retrieved, of which 19 case-control studies were included. A further 25 articles were retrieved for background information.

Conclusion: There was insufficient evidence to support a role of HHV-6 in MS onset and progression.

Deficient EBV-specific B- and T-cell response in patients with chronic fatigue syndrome

Epstein-Barr virus (EBV) has long been discussed as a possible cause or trigger of Chronic Fatigue Syndrome (CFS). In a subset of patients the disease starts with infectious mononucleosis and both enhanced and diminished EBV-specific antibody titers have been reported. In this study, we comprehensively analyzed the EBV-specific memory B- and T-cell response in patients with CFS. While we observed no difference in viral capsid antigen (VCA)-IgG antibodies, EBV nuclear antigen (EBNA)-IgG titers were low or absent in 10% of CFS patients. Remarkably, when analyzing the EBV-specific memory B-cell reservoir in vitro a diminished or absent number of EBNA-1- and VCA-antibody secreting cells was found in up to 76% of patients. Moreover, the ex vivo EBV-induced secretion of TNF-α and IFN-γ was significantly lower in patients. Multicolor flow cytometry revealed that the frequencies of EBNA-1-specific triple TNF-α/IFN-γ/IL-2 producing CD4(+) and CD8(+) T-cell subsets were significantly diminished whereas no difference could be detected for HCMV-specific T-cell responses. When comparing EBV load in blood immune cells, we found more frequently EBER-DNA but not BZLF-1 RNA in CFS patients compared to healthy controls suggesting more frequent latent replication. Taken together, our findings give evidence for a deficient EBV-specific B- and T-cell memory response in CFS patients and suggest an impaired ability to control early steps of EBV reactivation. In addition the diminished EBV response might be suitable to develop diagnostic marker in CFS.

A multiplex calibrated real-time PCR assay for quantitation of DNA of EBV-1 and 2

Accurate and highly sensitive tests for the diagnosis of active Epstein-Barr virus (EBV) infection are essential for the clinical management of individuals infected with EBV. A calibrated quantitative real-time PCR assay for the measurement of EBV DNA of both EBV-1 and 2 subtypes was developed, combining the detection of the EBV DNA and a synthetic DNA calibrator in a multiplex PCR format. The assay displays a wide dynamic range and a high degree of accuracy even in the presence of 1μg of human genomic DNA. This assay measures with the same efficiency EBV DNA from strains prevalent in different geographic areas. The clinical sensitivity and specificity of the system were evaluated by testing 181 peripheral blood mononuclear cell (PBMCs) and plasma specimens obtained from 21 patients subjected to bone marrow transplantation, 70 HIV-seropositive subjects and 23 healthy controls. Patients affected by EBV-associated post-transplant lymphoprolipherative disorders had the highest frequency of EBV detection and the highest viral load. Persons infected with HIV had higher levels of EBV DNA load in PBMCs and a higher frequency of EBV plasma viremia compared to healthy controls. In conclusion, this new assay provides a reliable high-throughput method for the quantitation of EBV DNA in clinical samples.

Diagnosis of human herpesvirus 6B primary infection by polymerase chain reaction in young children with exanthematic disease

INTRODUCTION

Exanthem subitum is a classical rash disease of early childhood caused by human herpesvirus 6B (HHV-6B). However, the rash is frequently misdiagnosed as that of either measles or rubella.

METHODS

In this study, a nested multiplex polymerase chain reaction (PCR) was used to diagnose HHV-6B primary infection, differentiate it from infections caused by HHV-6A and compare it to antibody avidity tests. The samples were separated into case group and control group according to the results of the indirect immunofluorescence assay (IFA) technique.

RESULTS

From the saliva samples analyzed, HHV-6A DNA was detected in 3.2% of the case group and in 2.6% of the control group. Regarding HHV-6B, PCR detected viral DNA in 4.8% of the case group and in 1.3% of the control group. Among the serum samples studied, a frequency of 1.7% was determined for HHV-6A in the case group and 1.2% in the control group. PCR did not detect HHV-6B DNA in serum samples. The sensitivity and specificity of the PCR technique ranged from 0% to 4.8% and 97.5% to 100%, respectively, compared to IFA.

CONCLUSIONS

The PCR technique was not suitable for diagnosing primary infection by HHV-6B in children with exanthematic disease and should not substitute the IFA.

Pityriasis rosea: an update with a critical appraisal of its possible herpesviral etiology

Pityriasis rosea is an acute, self-healing exanthem characterized by oval erythematous-squamous lesions of the trunk and limbs, that usually spares face, scalp, palms, and soles. Constitutional symptoms, which have the character of true prodromes; clinical features, which resemble those of the known exanthems; and many epidemiologic data all suggest an infectious origin. A host of infectious agents have been incriminated, but, recently, human herpesvirus 6 and 7 have been extensively studied. The goal of this review is to outline the epidemiologic, clinical, histologic, and ultrastructural features of pityriasis rosea, but mainly to stress its possible human herpesvirus nature. In addition, clues have been added to help the reader to go through the complex subtleties of the virologic investigation.

Apoptotic effects of Human Herpesvirus-6A on glia and neurons as potential triggers for central nervous system autoimmunity

BACKGROUND

Human Herpesvirus type 6 (HHV-6A and/or HHV-6B) has been tentatively associated with multiple sclerosis (MS). However, there is currently no direct proof of pathogenicity.

OBJECTIVES

To determine whether exposure to HHV-6 variants is capable of inducing programmed cell death (apoptosis) in representative cell types of the central nervous system (CNS).

STUDY DESIGN

HHV-6A and HHV-6B variants were grown on human T cell lines HSB2 and MOLT-3, respectively. Human neuronal (SK-N-SH), astrocytes (CRT), and oligodendrocytes (TC620) cell lines were exposed in vitro to infected T cells in a trans-well system for up to 4 days (5x10(4) cells target cells and 2x10(6) T cells). Apoptosis was measured by a FACS-based method.

RESULTS

Exposure to HHV-6A induced apoptosis in a time-dependent manner, while exposure to HHV-6B did not. Three days after exposure, apoptosis was increased compared to normalized controls, by 239% in neurons, 321% in astrocytes, and 326% in oligodendrocytes, respectively.

CONCLUSIONS

This study provides the demonstration that exposure to immune cells carrying replicating HHV-6A may injure glial cells and neurons by inducing apoptosis, and direct evidence for a causal association between HHV-6A with MS and related disorders.

Additional evidence that pityriasis rosea is associated with reactivation of human herpesvirus-6 and -7

To elucidate the role of human herpesvirus (HHV)-6 and -7 (HHV-7) in pityriasis rosea (PR), we measured their DNA load in plasma, peripheral blood mononuclear cells (PBMC), and tissues using a calibrated quantitative real-time PCR assay. We also studied HHV-6- and HHV-7-specific antigens in skin by immunohistochemistry and anti-HHV-7 neutralizing activity using a syncytia-inhibition test. Plasma and PBMC were obtained from 31 PR patients (14 children, 17 adults), 12 patients with other dermatites, and 36 blood donors. Skin biopsies were obtained from 15 adults with PR and 12 with other dermatites. HHV-6 and HHV-7 DNA were detected in 17% and in 39% of PR plasmas, respectively, but in no controls. HHV-7 viremia was associated with a higher PBMC load and, in adults, with systemic symptoms. HHV-7, but not HHV-6, levels in PBMC were higher in PR patients than in controls. HHV-6 and HHV-7 antigens were found only in PR skin (17% and 67% of patients analyzed, respectively), indicating a productive infection. Syncytia-neutralizing antibodies were found in PR patients and controls, but their titers were lower in patients with HHV-7 viremia. These data confirm the causal association between PR and active HHV-7 or, to a lesser extent, HHV-6 infection.

Is human herpesvirus 6 linked to kikuchi-fujimoto disease? The importance of consistent molecular and serologic analysis

BACKGROUND

Kikuchi-Fujimoto disease, also called histiocytic necrotizing lymphadenitis, is a self-limiting lymphadenopathy of unknown cause. The patient often presents with fever, malaise, and lymphadenopathy primarily involving the cervical lymph nodes. Laboratory findings are nonspecific, and the diagnosis is established by identifying characteristic pathologic features from lymph node biopsy. The etiologic agent has been proposed to be of viral origin; specifically, human herpesvirus 6 (HHV-6) has been implicated.

METHODS

The clinical, histologic, serologic, and molecular data from 471 cases of Kikuchi-Fujimoto disease reported between 1982 and 2001 and their relationship to HHV-6 were reviewed.

RESULTS

Thirty-two of the 471 patients in this review were tested for HHV-6 serology; all 32 had elevated titers for HHV-6. One hundred twelve patients with lymphadenopathies, including histiocytic necrotizing lymphadenitis, tested positive for HHV-6 by polymerase chain reaction. In situ hybridization results were positive in 41 cases.

CONCLUSION

This review illustrates the necessity for consistent molecular and serologic analysis.

Virus del herpes humano tipo 6 y tipo 7 en receptores de trasplantes

Recent years have witnessed a growing interest in the role of human herpesvirus (HHV) type 6 and type 7 as emerging pathogens or copathogens in transplant recipients. Both HHV-6 and HHV-7 belong to the beta-herpesvirus family and are closely related to another member of the family, cytomegalovirus. After the primary infection, these viruses remain latent in the human host and can reactivate after transplantation. Various clinical processes such as fever, rash, pneumonitis, encephalitis, hepatitis, and myelosuppression have been described in association with herpesvirus. Moreover, a growing body of evidence suggests that the major impact of HHV-6 and HHV-7 reactivation in transplantation is related to indirect effects, such as their association with cytomegalovirus disease, increased opportunistic infections, and graft dysfunction and rejection. The pathogenesis of HHV-6 and HHV-7 during the post-transplantation period, the methods used for their diagnosis, and the evaluation of antiviral drugs and strategies for their prevention and treatment are now the subject of extensive research.

Human herpesvirus 6: molecular biology and clinical features

Human herpesvirus 6 (HHV-6) exists as distinct variants HHV-6A and HHV-6B. The complete genomes of HHV-6A and HHV-6B have been sequenced. HHV-6B contains 97 unique genes. CD46 is the cell receptor for HHV-6, explaining its broad tissue tropism but its restricted host-species range. HHV-6 utilizes a number of strategies to down-regulate the host immune response, including molecular mimicry by production of a functional chemokine and chemokine receptors. Immunosuppression is enhanced by depletion of CD4 T lymphocytes via direct infection of intra-thymic progenitors and by apoptosis induction. Infection is widespread in infants between 6 months and 2 years of age. A minority of infants develop roseola infantum, but undifferentiated febrile illness is more common. Reactivation from latency occurs in immunocompromised hosts. Organ-specific clinical syndromes occasionally result, but indirect effects including interactions with other viruses such as human immunodeficiency virus type 1 and human cytomegalovirus or graft dysfunction in transplant recipients may be more significant complications in this population. Recent advances in quantitative PCR are providing additional insights into the natural history of infection in paediatric populations and immunocompromised hosts.

Calibrated real-time PCR assay for quantitation of human herpesvirus 8 DNA in biological fluids

Accurate laboratory tests for the diagnosis of active human herpesvirus 8 (HHV-8) infection are becoming essential to study the pathogenesis of HHV-8-associated tumors and for the clinical management of HHV-8-infected individuals. We have developed a highly sensitive, calibrated quantitative real-time PCR assay for the measurement of cell-free HHV-8 DNA in body fluids, based on the addition of a synthetic DNA calibrator prior to DNA extraction. The calibrator controls each sample for the presence of PCR inhibitors, determines a cutoff value of sensitivity for negative samples, and normalizes positive samples for the efficiency of DNA recovery. The assay shows a wide dynamic range of detection (between 1 and 10(6) viral genome equivalents/reaction) and a high degree of accuracy even in the presence of high amounts (up to 1 micro g) of human genomic DNA. Moreover, the assay has a very high sensitivity (lower detection limit, 10 genome equivalents/ml) and a high degree of reproducibility and repeatability with a coefficient of variation (CV) of <15 and 23%, respectively. Furthermore, the use of the calibrator improves the accuracy of quantitation and decreases the intersample variability (CV, 9 and 6%, respectively). The sensitivity and specificity of the assay were tested with a series of clinical specimens obtained from patients affected by various HHV-8-related diseases, as well as from a wide number of controls. In conclusion, our calibrated real-time PCR assay provides a reliable high-throughput method for quantitation of HHV-8 DNA in clinical and laboratory specimens.

Human herpesvirus 6 infection in febrile infants ninety days of age and younger

BACKGROUND

The importance of human herpesvirus 6 (HHV-6) as a pathogen in febrile infants </=90 days of age is unknown.

OBJECTIVE

To determine whether febrile infants 90 days of age and younger evaluated for sepsis have evidence of HHV-6 DNA in plasma or cerebrospinal fluid (CSF).

METHODS

Febrile infants </=90 days of age were tested for HHV-6 DNA using a real time quantitative fluorescent probe polymerase chain reaction assay.

RESULTS

Eighty samples from 47 infants were tested for HHV-6 DNA; 5 of 47 infants (10.6%) had HHV-6 DNA in plasma. In 2 of the 5 infants with HHV-6 DNA in plasma, HHV-6 DNA was also detected in the CSF. Both infants with evidence of HHV-6 DNA in plasma and CSF had HHV-6 Variant A infection. The quantity of HHV-6 DNA detected ranged from 70 to 169,000 DNA copies/ml. One infant with HHV-6 variant B infection had concomitant Escherichia coli bacteremia and urinary tract infection.

CONCLUSIONS

Approximately 10% of febrile infants </=90 days of age evaluated for sepsis had evidence of HHV-6 infection. HHV-6 Variant A and B infections were seen in these young infants. HHV-6 DNA was found in infants with and without another explanation for fever. Quantification of viral DNA may be important in determining the relevance of HHV-6 DNA in clinical specimens.

High incidence of human herpesvirus 6 infection with a high viral load in cord blood stem cell transplant recipients

Human herpesvirus 6 (HHV-6) infection in recipients of cord blood stem cell transplants (CBSCTs) was estimated by semiquantitative and real-time quantitative polymerase chain reaction (PCR) and reverse-transcription PCR. Of the CBSCT recipients, 7 (70%) of 10 had active HHV-6 infection after transplantation, and all 7 were inferred from their age to have already had a primary infection. Because HHV-6 DNA is seldom detected in cord blood, these cases were considered likely to represent reactivation. In contrast, the 3 patients without HHV-6 infection were all believed to be naive regarding HHV-6 primary infection because of their age and the results of PCR assays given before the transplantation procedure. The incidence of HHV-6 infection after transplantation was significantly higher (P < .05) than after bone marrow (BM) transplantation and peripheral blood stem cell (PBSC) transplantation, when recipients without primary HHV-6 infection prior to transplantation were excluded (CBSCT, 100%; BMT/PBSCT, 56.3%). Real-time PCR revealed a higher level of viral DNA in the peripheral blood mononuclear cells from CBSCT recipients than from BMT/PBSCT recipients or patients with exanthem subitum (P < .05). HHV-6 mRNA of the U79/80gene was also detected by reverse-transcription PCR in all analyzed patients with HHV-6 infection. Its detection was correlated with the emergence of viral DNA in the plasma and symptoms such as fever and rash. Thus, HHV-6 infection was more frequent and the viral load was higher in CBSCT recipients with prior primary infection.

High incidence of human herpesvirus 6 infection with a high viral load in cord blood stem cell transplant recipients

Human herpesvirus 6 (HHV-6) infection in recipients of cord blood stem cell transplants (CBSCTs) was estimated by semiquantitative and real-time quantitative polymerase chain reaction (PCR) and reverse-transcription PCR. Of the CBSCT recipients, 7 (70%) of 10 had active HHV-6 infection after transplantation, and all 7 were inferred from their age to have already had a primary infection. Because HHV-6 DNA is seldom detected in cord blood, these cases were considered likely to represent reactivation. In contrast, the 3 patients without HHV-6 infection were all believed to be naive regarding HHV-6 primary infection because of their age and the results of PCR assays given before the transplantation procedure. The incidence of HHV-6 infection after transplantation was significantly higher (P < .05) than after bone marrow (BM) transplantation and peripheral blood stem cell (PBSC) transplantation, when recipients without primary HHV-6 infection prior to transplantation were excluded (CBSCT, 100%; BMT/PBSCT, 56.3%). Real-time PCR revealed a higher level of viral DNA in the peripheral blood mononuclear cells from CBSCT recipients than from BMT/PBSCT recipients or patients with exanthem subitum (P < .05). HHV-6 mRNA of the U79/80gene was also detected by reverse-transcription PCR in all analyzed patients with HHV-6 infection. Its detection was correlated with the emergence of viral DNA in the plasma and symptoms such as fever and rash. Thus, HHV-6 infection was more frequent and the viral load was higher in CBSCT recipients with prior primary infection.

Real-time PCR for quantification of human herpesvirus 6 DNA from lymph nodes and saliva

A real-time quantitative PCR assay has been developed to measure human herpesvirus 6 (HHV-6) DNA in biological specimens. The assay sensitivity was 10 copies of DNA per well, with a linear dynamic range of 10 to 10(7) copies of HHV-6 DNA. Intra- and interassay variations were, respectively, 0.88 and 0.8% for samples containing 10(2) DNA copies, 0.99 and 0.96% for samples containing 10(4) copies, and 0.76 and 0.9% for samples containing 10(6) copies. Among 34 saliva samples from healthy subjects, 26 were found to contain HHV-6 DNA (76.5%; median, 23,870 copies/ml), and following a single freeze-thaw cycle, 25 of the same samples were found to be positive for HHV-6 DNA, although at a statistically significantly lower concentration (median, 3,497 copies/ml). The assay enabled detection of HHV-6 DNA in lymph node biopsies from patients with Hodgkin's disease (HD) (13 of 37 patients [35.1%]), B-cell neoplasms (8 of 36 patients [22.2%]), and T- or NK-cell neoplasms (3 of 13 patients [23.1%]), with concentrations ranging from 100 to 864,640 HHV-6 copies per microg of DNA (HHV-6B being found in every case except two). All HD patients infected with HHV-6 presented clinically with the nodular sclerosis subtype of HD. The real-time quantitative PCR assay developed here was simple to perform and was sensitive over a wide range of HHV-6 concentrations. It therefore appears to be of potential value in clinical investigation or diagnosis of HHV-6 infection.

Development of a real-time polymerase chain reaction assay for the diagnosis of human herpesvirus-6 infection and application to bone marrow transplant patients

A quantitative real-time PCR assay was developed for human herpesvirus-6 (HHV-6) genome based on TaqMan technology. After choosing a region of interest into the U65-U66 genes of HHV-6 genome, its nucleotide sequence was determined among four HHV-6 strains (one variant A and three variants B) to exclude a variability of sensitivity due to interstrain sequence differences. A plasmid containing HHV-6 target sequences identical to those of reference type viruses was constructed with the aim of standardisation. This HHV-6 genomic quantitation assay has a threshold sensitivity of ten copy equivalents (EqCop) per reaction. In order to test the feasibility of this assay directly on human samples, the technique was applied to the quantitation of HHV-6 genome in 30 blood samples from healthy subjects as well as 31 blood samples and three samples of cerebrospinal fluid (CSF) from 21 bone marrow transplant (BMT) recipients and four patients with a haematological disease but not treated by bone marrow transplantation. HHV-6 load ranged between 0.00015 and 0.0008 equivalent DNA copy number (EqCop) per 100 peripheral blood mononuclear cells (PBMCs) in healthy subjects whereas it ranged from <10 to 7500 EqCop per 100 PBMCs, and from <10 to 415,820 EqCop per 100 microl of whole CSF in patients. The efficacy of treatment with antiherpetic drug was associated with a decrease of the viral load in the CSF of one patient. This method leads to relevant results in term of range of quantitation, sensitivity, and safety against contamination by amplicons, and might constitute a useful tool for the follow-up of BMT recipients particularly in the presence of antiherpetic therapy.

Gene expression profile of herpesvirus-infected T cells obtained using immunomicroarrays: induction of proinflammatory mechanisms

Herpesvirus infections can frequently lead to acute inflammation, yet the mechanisms regulating this event remain poorly understood. In order to determine some of the immunological mechanisms regulated by human herpesvirus infections, we studied the gene expression profile of lymphocytes infected with human herpesvirus 6 (HHV-6) by using a novel immunomicroarray. Our nylon-based immunomicroarray contained more than 1,150 immune response-related genes and was highly consistent between experiments. Experimentally, we found that independently of the HHV-6 strain used to infect T cells, multiple proinflammatory genes were increased and anti-inflammatory genes were decreased at the mRNA and protein levels. HHV-6 strains A and B increased expression of the genes for interleukin-18 (IL-18), the IL-2 receptor, members of the tumor necrosis factor alpha superfamily receptors, mitogen-activated protein kinase, and Janus kinase signaling proteins. As reported previously, CD4 protein levels were also increased significantly. Specific type 2 cytokines, including IL-10, its receptor, and IL-14, were downregulated by HHV-6 infection and, interestingly, amyloid precursor proteins and type 1 and 2 presenilins. Thus, T cells respond to HHV-6 infection by inducing a type 1 immune response that may play a significant role in the development and progression of diseases associated with HHV-6, including pediatric, hematologic, transplant, and neurologic disorders.

Quantitation of human herpesvirus 6 DNA in infant with exanthem subitum by microplate PCR-hybridization assay

BACKGROUND

Quantitative analysis of human herpesvirus 6 (HHV-6) genome is important for monitoring active virus infection. The purpose of our study is to evaluate the reliability of a hybridization-based microtiter plate assay (polymerase chain reaction enzyme-linked immunosorbent assay (PCR ELISA)) for quantifying the virus genome.

METHODS

Semiquantitative analysis of the virus genome was carried out in 31 (18 male and 13 female) infants with primary HHV-6 infection. If the HHV-6 virus could be isolated from the peripheral blood mononuclear cells (PBMC), the infants were defined as being infected with HHV-6. The PCR ELISA method was used to determine the virus load. A titration of the virus was also carried out in the samples obtained during the acute phase of exanthem subitum.

RESULTS

Specificity of the method was demonstrated by a lack of amplification of human herpesvirus 7 and cytomegalovirus DNA. The upper and lower detection limits of the method were 58 and 5800 copies of the virus genome, respectively. The quantity of HHV-6 DNA in the PBMC during the acute phase (879 +/- 975 copies/10(4) PBMC) was significantly higher than during the convalescent phase (54 +/- 76 copies/10(4) PBMC). Furthermore, the virus load in acute phase plasma (53 +/- 75 copies/microL) was also significantly higher than in the convalescent phase samples (2 +/- 9 copies/microL). Virus load in both PBMC and plasma gradually increased after the onset of exanthem subitum until about day 3 to 4 of the illness, but then decreased quickly. However, there was no significant association between virus load and the numbers of infected cells.

CONCLUSION

Virus load in both PBMC and plasma gradually increased after the onset of exanthem subitum until about day 3 and day 4 of the illness, respectively, then it decreased quickly. These results indicate that our PCR ELISA system is reliable for monitoring active HHV-6 infection in vivo.

Human herpesvirus-6 and -7 in transplantation

Infections with the beta-herpesviruses human herpesvirus-6 (HHV-6) and human herpesvirus-7 (HHV-7) are ubiquitous in childhood. The immunosuppression secondary to organ or bone marrow transplantation together with posttransplantation management may favour viral replication and reactivation. HHV-6 and -7 induce immunosuppression by targeting lymphocytes, natural killer cells and monocytes. HHV-6 is commonly detected posttransplantation but variability in definitions of clinical syndromes related to this virus and detection methods have complicated understanding of the clinical relevance of HHV-6 posttransplantation. Clinical symptoms associated with HHV-6 include febrile illness, pneumonitis, hepatitis, encephalitis and bone marrow suppression. However, the majority of HHV-6 infections are asymptomatic. The incidence of HHV-7 infection and its clinical manifestations posttransplantation are even less well characterised. In addition, HHV-6 and HHV-7 are related to CMV disease or acute graft-versus-host disease and, indirectly, to increases in resource utilisation. Based on the potential relevance of these two beta-herpesviruses in transplant recipients, further studies are required to establish their real impact in transplantation. For this, sensitive and specific molecular diagnostic techniques allowing for the rapid detection and quantitation of virus and for the analysis of susceptibility to current antiviral agents are required.

Real-time quantitative PCR for human herpesvirus 6 DNA

The diagnosis of human herpesvirus 6 (HHV-6) infection represents a complex issue because the most widely used diagnostic tools, such as immunoglobulin G antibody titer determination and qualitative DNA PCR with blood cells, are unable to distinguish between latent (clinically silent) and active (often clinically relevant) infection. We have developed a new, highly sensitive, quantitative PCR assay for the accurate measurement of HHV-6 DNA in tissue-derived cell suspensions and body fluids. The test uses a 5' nuclease, fluorogenic assay combined with real-time detection of PCR amplification products with the ABI PRISM 7700 sequence detector system. The sensitivity of this method is equal to the sensitivity of a nested PCR protocol (lower detection limit, 1 viral genome equivalent/test) for both the A and the B HHV-6 subgroups and shows a wider dynamic range of detection (from 1 to 10(6) viral genome equivalents/test) and a higher degree of accuracy, repeatability, and reproducibility compared to those of a standard quantitative-competitive PCR assay developed with the same reference DNA molecule. The novel technique is versatile, showing the same sensitivity and dynamic range with viral DNA extracted from different fluids (i.e., culture medium or plasma) or from tissue-derived cell suspensions. Furthermore, by virtue of its high-throughput format, this method is well suited for large epidemiological surveys.

Outbreaks of human-herpes virus 6 (HHV-6) infection in day-care centers in Belém, Pará, Brazil

A total of 730 children aged less than 7 years, attending 8 day-care centers (DCCs) in Belém, Brazil were followed-up from January to December 1997 to investigate the occurrence of human-herpes virus 6 (HHV-6) infection in these institutional settings. Between October and December 1997 there have been outbreaks of a febrile- and -exanthematous disease, affecting at least 15-20% of children in each of the DCCs. Both serum- and- plasma samples were obtained from 401 (55%) of the 730 participating children for the detection of HHV-6 antibodies by enzyme-linked immunosorbent assay (ELISA), and viral DNA amplification through the nested-PCR. Recent HHV-6 infection was diagnosed in 63.8% (256/401) of them, as defined by the presence of both IgM and IgG-specific antibodies (IgM+/IgG+); of these, 114 (44.5%) were symptomatic and 142 (55.5%) had no symptoms (p = 0.03). A subgroup of 123 (30.7%) children were found to be IgM-/IgG+, whereas the remaining 22 (5.5%) children had neither IgM nor IgG HHV-6- antibodies (IgM-/IgG-). Of the 118 children reacting strongly IgM-positive (> or = 30 PANBIO units), 26 (22.0%) were found to harbour the HHV-6 DNA, as demonstrated by nested-PCR. Taken the ELISA-IgM- and- nested PCR-positive results together, HHV-6 infection was shown to have occurred in 5 of the 8 DCCs under follow-up. Serological evidence of recent infections by Epstein-Barr virus (EBV) and parvovirus B19 were identified in 2.0% (8/401) and 1. 5% (6/401) of the children, respectively. Our data provide strong evidence that HHV-6 is a common cause of outbreaks of febrile/exanthematous diseases among children attending DCCs in the Belém area.

An immunoblot assay for detection of immunoglobulin M antibody to human herpesvirus 6

We identified the human herpesvirus 6 (HHV-6)-dominant immunoglobulin M (IgM)-reactive virion protein as being the same 101-kDa protein (101K) previously identified as the major IgG immunoreactive protein and a specific serologic marker of HHV-6 infection. An immunoblot assay (IB) to detect HHV-6-specific IgM antibodies against the 101K protein in human serum samples was developed. The assay was validated by using acute- and convalescent-phase serum collected from children under 2 years of age in which we previously detected IgG seroconversion to the HHV-6 101K protein. Of 32 serum pairs which previously demonstrated IgG seroconversion to the 101K protein, 29 had IgM reactivity to the same protein in the acute-phase sample and the remaining 3 had reactivity in the convalescent-phase sample. We also detected HHV-6 IgM activity in sera collected from individuals > or =4 years of age who were also IgM seropositive to measles or rubella. Results of cross-adsorption studies using measles virus-, rubella virus-, and HHV-6-infected cells as the adsorbing antigen indicated no cross-reactivity between measles or rubella IgM and HHV-6 IgM in human serum samples. The IgM IB detected HHV-6-specific IgM antibody to the 101K protein in 78% (63 of 81) of tested acute-phase serum collected from young children with an undifferentiated rash illness by using a single serum dilution.

Monitoring of human herpesvirus-6 and -7 genomes in saliva samples of healthy adults by competitive quantitative PCR

Human herpesviruses-6 and -7 (HHV-6 and HHV-7) are thought to be transmitted during early infancy through saliva. However, the kinetics of the virus shedding in saliva of healthy adults, from whom children are assumed to acquire the viruses, is mostly unknown. This study was conducted to determine how many copies of the genome are secreted in saliva of healthy adults and to clarify the relationship between viral DNA load and virus isolation of HHV-6 and HHV-7. Competitive PCR was performed using primer sets in the U42 gene of each viral genome. In saliva samples from 29 healthy adults, HHV-6 and HHV-7 DNA was detected in 41.4% and 89.7%, respectively. The average copy number of the HHV-7 genome in the positive samples was higher than that of the HHV-6 genome. Follow-up studies of six seropositive individuals for 3 months showed that the amount of HHV-7 DNA was constant in each individual and that "high producers" and "low producers" could be distinguished. By contrast, the amount of HHV-6 DNA varied drastically over time in each individual. Although HHV-6 was never isolated from the saliva of any of the six individuals during the follow-up period, HHV-7 was isolated from each individual several times. The amount of HHV-7 DNA tended to be higher at the times when the virus was isolated than at the times when the virus was not isolated. These data demonstrate a striking contrast between HHV-6 and HHV-7 in the kinetics of genome and virus shedding.

Quantification of human herpesvirus 6 in healthy volunteers and patients with lymphoproliferative disorders by PCR-ELISA

To determine whether actual numbers of human herpesvirus 6 (HHV-6) genome in hematologic neoplasias are associated with disease condition, we developed a quantitative PCR-ELISA for detection of HHV-6. The amount of viral DNA was determined using externally amplified known amounts of the plasmid DNA containing the viral target sequences. First, we determined a viral burden in peripheral blood leukocytes obtained from 23 healthy volunteers and four specimens of lymph nodes with reactive hyperplasia. Using 1 microg of DNA, the prevalence of HHV-6 was 43.4% (10/23), ranging from 0 to 100 HHV-6 genomes in blood obtained from healthy volunteers. The amounts of HHV-6 genomes were < 10 in four non-neoplastic lymph node specimens. We next examined the amount of viral DNA in 21 blood specimens and 19 lymph node specimens obtained from patients with lymphoproliferative diseases (LPD) at the time of diagnosis. The number of HHV-6 genomes in most of the B-cell lymphoma was < 5 in both blood and lymph node specimens, however, two lymph node specimens obtained from immunoblastic lymphadenopathy (IBL) and T-cell lymphoma had very high levels of HHV-6 viral DNA (3705 and 810, respectively). We also found that HHV-6 genomes in peripheral blood were more than 1000 in two patients with chronic lymphocytic leukemia. For all LPD patients combined, there were significantly higher levels of viral DNA (200.6 +/- 654.8 HHV-6 genomes per 1 microg purified DNA) compared to those in healthy volunteers (10.0 +/- 21.0 HHV-6 genomes per 1 microg purified DNA) (P < 0.05). This study demonstrates that a high level of HHV-6 viral DNA is occasionally associated with LPD patients. Although it is still uncertain whether HHV-6 is related to the pathogenesis in LPD or not, our results suggest that measurement of HHV-6 genomes using PCR-ELISA may be useful not only to understand the mechanism of HHV-6 infection in hemopoietic neoplasia but also to manage the care of immnocompromised patients such as bone marrow transplant patients.

Interferon-induced proteins are elevated in blood samples of patients with chemically or virally induced chronic fatigue syndrome

Overlapping symptomatologies between Chronic Fatigue Syndrome (CFS) and Chemical Sensitivity have been observed by different investigators. Therefore, it is of great importance to develop biomarker(s) for possible differentiation between viral induced CFS (without sensitivity to chemicals) versus chemically induced CFS. Since interferon induced proteins 2-5A Synthetase and Protein Kinase RNA (PKR) have been implicated in the viral induction of CFS, the objective of this study was to utilize 2-5A and PKR activity for differentiation between CFS induced by either viruses or chemicals. Based on the CDC definition and criteria, twenty CFS patients who were positive for viral genome(s) (mainly HHV6; HTLVII, EBV, and CMV) and did not have any history of exposure to toxic chemicals were included in this study. As a comparison, the second group of patients consisted of twenty individuals from the same geographical area who were negative for viral genomes but had been exposed to methyl tertiary-butyl ether concentration of up to 70 ppb and benzene concentration up to 14 ppb. All patients complained of fatigue and other symptoms overlapping between the two groups. From all 40 patients, blood was drawn, leukocyte extract was prepared and assayed for 2-5A Synthetase and PKR activity. Clinical specimens which were positive for viral genomes showed from 2.2-38.7 fold increase in 2-5A activity and 1.3-13.5 fold increase in PKR activities over the background of the healthy controls. Similarly, the second group (negative for viral genomes, but exposed to chemicals) showed a 1.1-29.2 fold increase for 2-5A Synthetase and a 1.3-11.6 fold increase for PKR when they were compared to healthy subjects. To elucidate mechanisms involved in viral versus chemical induction of 2-5A Synthetase and PKR, MDBK cell lines were cultured either in the presence or absence of HHV6, MTBE, or Benzene, heat shock proteins and interferon-beta. 2-5A and PKR activities were measured in all the above conditions. A clear induction of 2-5A and PKR was observed when MDBK cells were exposed to HHV6, MTBE, and Benzene. This induction was more significant with HSP90, HSP70, and IFN-beta indicating their involvement in the mechanism of action. However, when MDBK cells were incubated either with MTBE + Benzene or HHV6 in the presence or absence of anti IFN-beta or anti-HSP-70, the activities of both 2-5A and PKR in HHV6 infected cells were inhibited by more than 90% due to addition of anti IFN-beta, and only 20% by addition of anti-HSP70. While in MTBE + Benzene exposed cells anti IFN-beta reduced the activity of these enzymes by 40% and anti-HSP70 by more than 90%. This variation in the induction of 2-5A and PKR by anti-HSP70 or IFN-beta indicates involvement of IFN-beta in viral induction 2-5A and PKR, and HSP involvement in chemical induction of these enzymes. We conclude that 2-5A and PKR are not only biomarkers for viral induction of CFS, but biomarkers to other stressors that include MTBE and Benzene.

Human herpesvirus 6

Human herpesvirus (HHV) 6 is a beta-herpes, DNA virus. This virus shows closest homology with cytomegalovirus and HHV-7. Infection usually occurs in infants 6 to 24 months of age, and primary infection may result in roseola. HHV-6 infection in infants is the commonest cause of fever-induced seizures. Infection in adults is seen primarily in immunocompromised hosts with solid organ transplants or in those with human immunodeficiency virus infection. The virus is capable of pronounced interaction in vitro with cytomegalovirus and human immunodeficiency virus and induces immunosuppression and apoptosis. The importance of these interactions in vivo necessitates further investigation. HHV-6 infection may contribute to the pathogenesis of multiple sclerosis. HHV-6 may be diagnosed by viral culture, serology, or polymerase chain reaction.

Quantitation of herpes simplex viral DNA in Vero cells for evaluation of an antiviral agent using the polymerase chain reaction

A method for quantitation of the DNA of Herpes simplex virus type 2 (HSV-2)-infected Vero cells by the polymerase chain reaction (PCR) was developed. This method allowed recognition of several molecules of viral DNA among the total DNA extracted from cells. The method could be applied to a very large range (10(-0)-10(-7)) of initial amounts of template. Products of PCR were collected after each cycle for kinetic analysis. Products were subjected to electrophoresis and amplified bands were stained with ethidium bromide. The intensity of fluorescence of each band was measured with a charge-coupled device (CCD) image analyzer. The time course of increases in the relative yield of viral DNA was determined. Two-fold amplification of viral DNA occurred each 6-h cycle from 7 h after infection. Using this method, the yields of viral DNA after treatment with the drug acyclovir (ACV) at 0.1 and 2 microg/ml were about 1/10 and 1/80 of those from nontreated infected cells, respectively. These results indicate that this method makes clear the inhibitory effect of ACV on the synthesis of viral DNA.

Detection of Mycoplasma genus and Mycoplasma fermentans by PCR in patients with Chronic Fatigue Syndrome

Mycoplasma fermentans and other Mycoplasma species are colonizers of human mucosal surfaces and may be associated with human immunodeficiency virus infection. While many infectious agents have been described in different percentages of patients with Chronic Fatigue Syndrome (CFS), little is known about the prevalence of mycoplasmas and especially M. fermentans in CFS patients. A polymerase chain reaction (PCR)-based assay was used to detect Mycoplasma genus and M. fermentans genomes in peripheral blood mononuclear cells (PBMC) of CFS patients. Blood was collected from 100 patients with CFS and 50 control subjects. The amplified products of 717 bp of Mycoplasma genus, and 206 bp of M. fermentans were detected in DNA purified from blood samples in 52% and 34% of CFS samples, respectively. In contrast, these genomes were found in only 14% and 8% of healthy control subjects respectively (P < 0.0001). All samples were confirmed by Southern blot with a specific probe based on internal sequences of the expected amplification product. Several samples, which were positive for Mycoplasma genus, were negative for M. fermentans indicating that other Mycoplasma species are involved. A quantitative PCR was developed to determine the number of M. fermentans genome copies present in 1 microg of DNA for controls and CFS patients. Mycoplasma copy numbers ranging from 130 to 880 and from 264 to 2400 were detected in controls and CFS positive subjects, respectively. An enzyme immunoassay was applied for the detection of antibodies against p29 surface lipoprotein of M. fermentans to determine the relationship between M. fermentans genome copy numbers and antibody levels. Individuals with high genome copy numbers exhibited higher IgG and IgM antibodies against M. fermentans specific peptides. Isolation of this organism by culture from clinical specimens is needed in order to demonstrate specificity of signal detected by PCR in this study.

Human Herpesvirus-6 (HHV-6) infection in multiple sclerosis: a preliminary report

We examined cerebral spinal fluid (CSF) from multiple sclerosis (MS) patients and patients with other neurological diseases (OND) for antibody specific for Human Herpesvirus-6 (HHV-6) and for HHV-6 DNA detectable by PCR. CSF from MS patients had a higher frequency of IgG antibody to HHV-6 late antigens (39.4%) compared with CSF from OND (7.4%). In contrast, the frequency of detectable IgG antibody in CSF from MS patients specific for Epstein-Barr Virus (EBV) (12.1%) and Human Cytomegalovirus (HCMV) (6.1%) was much lower. Two of 12 MS CSFs (16.7%) also contained HHV-6 DNA detected by PCR. None of four OND CSF were positive for HHV-6 DNA. Plasma from 16 patients with MS, eight with OND and 72 healthy donors were tested for antibodies by ELISA to HHV-6 early (p41/38) and late (gp110) proteins. Although no differences in anti-gp110 IgG antibody were detected between MS patients, patients with other neurological diseases, and normals, IgG antibody to early protein p41/38 was detected in > 68% of the plasma from MS patients, 12.5% from OND patients and 27.8% of the controls. IgM antibody to p41/38 was present in > 56% of MS patients, 12.5% of OND patients, and 19% of controls. These data suggest that more than half of the MS patients had active, ongoing HHV-6 infections. HHV-6 was also isolated from peripheral blood mononuclear cells (PBMC) from 3/5 MS patients who were in relapse or had progressive disease and was identified as HHV-6 Variant B. These preliminary results support the hypothesis that HHV-6 may be a co-factor in the pathogenesis of some cases of MS.

Application of competitive PCR to cerebrospinal fluid samples from patients with herpes simplex encephalitis

The purpose of the present study was to determine if the quantity of herpes simplex virus (HSV) DNA in the cerebrospinal fluid (CSF) of patients with herpes encephalitis would be useful in establishing the prognosis of the disease and to determine the effect of antiviral therapy on the clearance of viral DNA from the CSF. Quantitation of HSV DNA was done by constructing an internal standard (IS) from the glycoprotein B amplicon which had a 25-bp deletion between primer annealing sites. Each CSF specimen was coamplified with the IS and the ratio of the amount of HSV/amount of IS was compared to the ratios on a standard curve constructed with the same IS plus known amounts of HSV DNA. CSF specimens were available from 16 patients who were treated with intravenous acyclovir, and the amount of HSV DNA ranged from < 25 to 18,000 copies per microliter in CSF obtained before or within 4 days of the initiation of acyclovir therapy. Patients with > 100 copies of HSV DNA per microliter were older, were found by computed tomography to have lesions, and had poorer outcomes than patients with < 100 copies. Follow-up CSF specimens were available from seven patients. In six of these seven patients, the HSV DNA levels decreased during therapy. One patient had a twofold increase in HSV DNA levels after 1 week of therapy and died on day 8. The application of this assay may be helpful in establishing the prognosis and in the monitoring of patients with herpes simplex encephalitis.

Human herpesvirus type 7 in Hodgkin's disease

Several lines of evidence have pointed to the involvement of a viral agent in the pathogenesis of Hodgkin's disease (HD). Therefore we investigated the presence of human herpesvirus type 7 (HHV-7) in 53 cases of HD by polymerase chain reaction (PCR), DNA in situ hybridization (ISH) and immunohistochemistry. HHV-7 DNA was frequently detected (68% of the cases) in HD biopsies by PCR independently of the histological type, whereas only 32% (P<0.05) of positive cases were found in 19 reactive lymph nodes. However, by applying the quantitative PCR technique, the majority of the samples showed a low level of viral load. Moreover, ISH for HHV-7 DNA was positive in a low number of small T lymphocytes and consistently negative in Hodgkin and Reed-Sternberg (HRS) cells, which appeared negative for HHV-7 also at immunohistochemistry. These results indicate that the high frequency of HHV-7 infection in HD: (i) is probably non-productive, (ii) mainly involves small lymphocytes belonging to the T-lineage, and (iii) is probably due to the recruitment of non-malignant reactive cells in HD tissue.

The clinical utility of viral quantitation using molecular methods

BACKGROUND

The quantitation of viral nucleic acids in biological fluids has become increasingly desirable over the past several years. To this end, a number of quantitative molecular procedures have been developed.

OBJECTIVES

The objective was to review the current literature on the molecular techniques used in the quantitation of viral nucleic acids and to assess the appropriateness of these methods for clinical use.

RESULTS

Assays involving both target and signal amplification are now available for the accurate and precise quantitation of viral burden in infected patients. These methods include quantitative polymerase chain reaction (PCR), branched chain signal amplification (bDNA), nucleic acid sequence-based amplification (NASBA) and the SHARP signal and hybrid capture systems. Our understanding of the natural history and pathogenesis of viruses such as the human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), cytomegalovirus (CMV) and Epstein-Barr virus (EBV) may be greatly facilitated by accurate determinations of viral and infected cell burden. Quantitation of viral load in infected individuals may also be useful to assess disease progression, monitor the efficacy of therapy and to predict treatment failure and the emergence of drug-resistant viruses.

CONCLUSION

Precise, accurate and reproducible quantitation of viral load is now feasible. Molecular assays for viral quantitation should have a considerable impact on medical research and clinical care.

Comparative study of different standardization concepts in quantitative competitive reverse transcription-PCR assays

Four different standardization approaches based on a competitive reverse transcription (RT)-PCR assay were compared with a noncompetitive assay based on an external standard curve. Criteria for assessment were accuracy in quantitation, correctness of recovery, sensitivity, dynamic range, reproducibility, throughput, and convenience of sample handling. As a model system, we used the 5'-noncoding region of hepatitis C virus (HCV) for amplification in all quantitative RT-PCRs. A computer program that allowed parallel data processing was developed. Surprisingly, all methods were found suitable for accurate quantitation and comparable with respect to the criterion correctness of recovery. All results differed only by a factor of about 2. The reason for this finding might be that all of our mimics, as well as the wild-type genome of HCV, exhibited exactly the same amplification and hybridization efficacy. Moreover, minimal competition occurred in our experiments over a 5-log dynamic range. A further topic of our investigation was the comparison of two different competitive RNA fragments, mimics, with regard to their suitability as internal standards. One was a heterologous mimic, in which only the primer binding sites were identical to the wild type. The second one was a homologous mimic identical to the wild type except for a small region used for differential hybridization, which was replaced by a permutated sequence of the same length. Both the homologous and heterologous internal mimics were found appropriate for an accurate competitive RT-PCR assay, provided that amplification efficacy, as well as capture efficacy, is proven identical for both analyte and mimic.

Detection of human herpesvirus 6 DNA in serum by a microplate PCR-hybridization assay

PCR was performed on DNA extracts derived from clinical serum samples submitted for human herpesvirus 6 (HHV-6) serological examination. To detect amplified HHV-6 products, a hybridization-based microtiter plate assay (PCR ELISA; Boehringer Mannheim) was used. The assay system was found to be rapid, specific, and sensitive. Approximately three copies of a plasmid-based HHV-6 sequence could be detected, and no cross amplification was observed with HHV-7 genomic DNA. There was no correlation found between HHV-6 DNA detection and serological status in clinical serum samples from individuals more than 2 years old. On the other hand, in serum samples from infants less than 2 years old, a high rate of detection of HHV-6 DNA was observed in those who lacked immunoglobulin G and M antibodies to HHV-6 (55%). In this regard, PCR of serum DNA extracts may be used as a sensitive indicator of active HHV-6 infection in infants prior to their seroconversion.

Development of a semiquantitative PCR assay using internal standard and colorimetric detection on microwell plate for pseudorabies virus

We have developed a semiquantitative PCR assay on microtitre plates for quantitation of pseudorabies virus (PRV). The test is based on co-amplification with an internal control (IC) of the target viral DNA, followed by hybridization of the biotin-amplified products on a capture probe covalently immobilized to a Covalink-NH MicroWells plate and then visualization with colorimetric enzymatic reactions. PCR was performed in the presence of uracil-N-glycolsylase (UNG) with dUTP instead of dTTP to prevent false positive results due to carry-over contamination. Our colorimetric test had a 3.5 log dynamic range with a detection level of 30 DNA copies per PCR reaction. A standard curve for quantitation of pseudorabies virus was established from co-amplification of 10 to 10(5) PRV molecules with 1000 IC molecules. Ratios of viral optical density/IC optical density were plotted against the number of PRV DNA target molecules in the PCR amplification. Integration of 96-well formats and automation using robots at different steps of the test ensured a good repeatability. Calibration of the quantitative test using samples from experimentally-infected pigs is in progress.

Human herpesvirus-6 and human herpesvirus-7 infections in bone marrow transplant recipients

Human cytomegalovirus (HCMV), human herpesvirus-6 (HHV-6), and human herpesvirus-7 (HHV-7) DNA in peripheral blood leukocytes (PBL) of 61 bone marrow transplant recipients was monitored weekly during the first 12 weeks post-transplantation by a nested polymerase chain reaction (PCR). Thirty-seven (61%), 17 (28%), and 32 (53%) of patients had one or more PBL specimens positive for HCMV, HHV-6 or HHV-7 DNA, respectively. HHV-7 DNA in PBL during the early post-transplant period was associated with a longer time to neutrophil engraftment (mean 28.8 days vs 19.8 days; P = 0.01). In two patients who failed to engraft, HHV-6 DNA and HHV-7 DNA was detected in plasma and PBL, respectively, early in their post-transplant period. Patients with HCMV disease were more likely to have concurrent HHV-7 DNA in PBL prior to onset of disease than were patients with asymptomatic HCMV infection, suggesting that HHV-7 may be a cofactor in the progression from HCMV infection to HCMV disease. In the 17 patients (179 specimens) in whom viral DNA in plasma was studied (in addition to PBL), a positive result was found only in 3. In each, viral DNA in plasma appeared to correlate with clinically significant disease. HHV-7 DNA in plasma was associated with encephalitis in an allograft recipient.

Acquired immunodeficiency syndrome-associated Kaposi's sarcoma and human herpesvirus 8 DNA detection in serial peripheral blood mononuclear cell samples

Human herpesvirus 8 (HHV8) DNA was amplified from peripheral blood mononuclear cells (PBMCs) using PCR in 120 HIV-seropositive in- and outpatients who were enrolled in a cohort study between January 1994 and June 1995. Risk factors for HIV infection were homosexuality/bisexuality alone in 64 cases (30 with Kaposi's sarcoma (KS) and 34 without KS, 4 of whom had KS lesions that appeared during follow-up in the cohort), heterosexual contact alone in 32 cases (among whom 1 woman with KS who was the spouse of a bisexual with KS), and transfusion of blood or blood products alone in 24 cases. Three blood samples at 3-4-month intervals were scheduled for each patient. Twenty-five HIV1-seronegative patients served as controls. A total of 47.1% of homo- or bisexual males with KS and 26.7% of homo- or bisexual males without KS had positive HHV8 DNA detection as compared with 21.9% of patients contaminated by heterosexual contact, 8.3% of blood product recipients and 0% of controls. HHV8 DNA detection was intermittent in all but 3 patients according to sequential sampling. Multivariate analysis showed that AIDS-KS was associated with sexual transmission, mainly homo- or bisexual practices and with HHV8 infection assessed by PCR in PBMCs.

Effects of storage temperature and time on qualitative and quantitative detection of cytomegalovirus in blood specimens by shell vial culture and PCR

Cytomegalovirus (CMV) infectious titers and DNA levels were determined by quantitative shell vial culture and quantitative-competitive PCR with blood samples from 10 renal transplant recipients with active CMV infection. Blood samples were stored at either room temperature or 4 degrees C and were processed at intervals of 0, 6, 24, 48, and 72 h. All samples were culture and PCR positive at baseline. Whereas the sensitivity of shell vial culture progressively declined, with only 55% positive at 24 h and 10% positive at 48 h, all samples remained PCR positive at all time points. Furthermore, the infectious titer diminished by 83 to 91% by 24 h compared to that at baseline (P < 0.0001), but quantitative DNA levels did not decline over time. Storage temperature had no significant effect on either infectious titer or DNA levels.

Human herpesvirus 6

Human herpesvirus 6 variant A (HHV-6A) and human herpesvirus 6 variant B (HHV-6B) are two closely related yet distinct viruses. These visuses belong to the Roseolovirus genus of the betaherpesvirus subfamily; they are most closely related to human herpesvirus 7 and then to human cytomegalovirus. Over 95% of people older than 2 years of age are seropositive for either or both HHV-6 variants, and current serologic methods are incapable of discriminating infection with one variant from infection with the other. HHV-6A has not been etiologically linked to any human disease, but such an association will probably be found soon. HHV-6B is the etiologic agent of the common childhood illness exanthem subitum (roseola infantum or sixth disease) and related febrile illnesses. These viruses are frequently active and associated with illness in immunocompromised patients and may play a role in the etiology of Hodgkin's disease and other malignancies. HHV-6 is a commensal inhabitant of brains; various neurologic manifestations, including convulsions and encephalitis, can occur during primary HHV-6 infection or in immunocompromised patients. HHV-6 and distribution in the central nervous system are altered in patients with multiple sclerosis; the significance of this is under investigation.

Role of the extracellular domain of human herpesvirus 7 glycoprotein B in virus binding to cell surface heparan sulfate proteoglycans

In an attempt to identify the human herpesvirus 7 (HHV-7) envelope protein(s) involved in cell surface binding, the extracellular domain of the HHV-7 glycoprotein B (gB) homolog protein was cloned and expressed as a fusion product with the Fc domain of human immunoglobulin G heavy chain gamma1 (gB-Fc) in an eukaryotic cell system. Indirect immunofluorescence followed by flow cytometric analysis revealed specific binding of gB-Fc to the membrane of SupT1 cells but not to other CD4+ T-lymphoblastoid cell lines, such as Jurkat or PM1, clearly indicating that gB-Fc did not bind to the CD4 molecule. This was also suggested by the ability of gB-Fc to bind to CD4-negative fibroblastoid Chinese hamster ovary (CHO) cells. The binding was abrogated by enzymatic removal of cell surface heparan sulfate proteoglycans by heparinase and heparitinase but not by treatment with condroitinase ABC. In addition, binding of the gB-Fc fusion protein to CHO cells was severely impaired in the presence of soluble heparin, as well as when heparan sulfate-deficient mutant CHO cells were used. Consistent with these findings, soluble heparin was found to block HHV-7 infection and syncytium formation in the SupT1 cell line. Although the CD4 antigen is a critical component of the receptor for the T-lymphotropic HHV-7, these findings suggest that heparin-like molecules also play an important role in HHV-7-cell surface interactions required for infection and that gB represents one of the HHV-7 envelope proteins involved in the adsorption of virus-to-cell surface proteoglycans.

New quantitative assay of hepatitis B and C viruses by competitive PCR using alternative internal sequences

A competitive PCR was developed for quantitation of hepatitis B virus (HBV) DNA and hepatitis C virus (HCV) RNA, alternatively, using only two constructions containing both priming sites. DNAs corresponding to the HBV-S gene and the HCV-5' non-coding region were introduced into distinct plasmids. HBV plasmid was used as a standard for HBV-DNA quantitation, in competition with the HCV plasmid as internal control. HBV and HCV plasmids also served as template for transcription of HBV-RNA, and HCV-RNA, which was used as internal control and standard, respectively, in competition for HCV-RNA quantitation. The analyzed samples for HBV and HCV quantitation were processed in the same way in competition with the internal controls and to the respective calibration curves obtained by serial dilutions of the mimic standard. This method showed very good specificity and sensitivity, allowing absolute quantitation in a large linear range from 5 viral genomic copies per assay up to 10(6) copies, in sera of chronically HBV and HCV infected patients, as well as in supernatants of cell cultures inoculated with these viruses.

Development and application of HHV-6 antigen capture assay for the detection of HHV-6 infections

An HHV-6 antigen capture assay measuring gp116/64/54 antigen was developed. This ELISA is specific for HHV-6 Variants A and B, does not cross react with other human herpesviruses, is sensitive, stable, quantitative, and can detect antigen in body fluids and cell cultures. Relative to virus isolation or techniques for measuring HHV-6 nucleic acids, the assay is much simpler and less expensive to perform. Plasmas/sera (413) obtained from healthy donors, children with Exanthem subitum, febrile illnesses, patients with Chronic Fatigue Syndrome, and AIDS patients tested by antigen capture assay demonstrated that the assay is useful in clinical laboratory settings. The capture assay can also be used to monitor cell cultures for virus isolation, production, quantitation, and antiviral agent screening.