Detection of herpesvirus type 6 by polymerase chain reaction in blood donors: random tests and prospective longitudinal studies

Human herpes simplex virus-6 (HHV-6) detection and seroprevalence among Qatari nationals and immigrants residing in Qatar

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The prevalence of anti-human herpes virus-6 immunoglobulin G (IgG) was 71.7% among healthy donors in Qatar.

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One-quarter (24.3%) of healthy donors in Qatar had detectable viraemia.

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No strong association was found between viraemia and IgG positivity.

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A significant association was found between viraemia and the nationality of healthy donors.

Background

Human herpes simplex virus-6 (HHV-6) is the causative agent of exanthema subitum. Transmission mainly occurs through salivary secretions, yet blood transfusions and organ transplantations have also been reported as routes of transmission. Studies of seroprevalence of HHV-6 in the Middle East and North Africa (MENA) region and other parts of Asia are scarce. As such, this study aimed to estimate the seroprevalence of HHV-6 among healthy blood donors in Qatar.

Methods

In total, 620 healthy blood donors from different nationalities residing in Qatar, mainly from the MENA region and Southeast Asia, were tested using a commercial anti-HHV-6 immunoglobulin G (IgG) enzyme-linked immunosorbent assay kit. In addition, HHV-6 DNA from randomly selected samples was tested and quantified using quantitative reverse transcriptase polymerase chain reaction.

Results

Anti-HHV-6 IgG was detected in 71.7% (445/620) [95% confidence interval (CI) 68.2–75.3%] of the tested samples, while 24.3% (61/251) (95% CI 20.0–29.6%) had detectable HHV-6 viraemia. Only 22.5% of individuals with positive IgG status had detectable HHV-6 DNA in their blood, indicating a weak association between viraemia and IgG positivity (P=0.08). Furthermore, no significant difference was associated between HHV-6 viraemia and demographic characteristics, except for nationality.

Conclusion

The seroprevalence of HHV-6 in Qatar was found to be similar to rates reported in other parts of the world.

Molecular epidemiology of human Herpesviruses types 1-6 and 8 among Greek blood donors

BACKGROUND

Human Herpesviruses (HHVs) maintain life-long latent persistence in the majority of the adult population including blood donors. The necessity for their study resides in the potential risk of transfusion-associated infection and the subsequent complications in the immunocompromised host. We aimed to assess the prevalence of HHVs types 1-6 and 8 among healthy blood donors of Thessaly prefecture in order to evaluate the frequency distribution of HHVs in Greek population and to ascertain possible correlations with demographic factors.

MATERIALS AND METHODS

Polymerase chain reaction (PCR) detection of HHVs DNA was determined in 401 randomly selected consecutive blood donors of Central Greece. Epidemiological data were recorded through a well structured questionnaire.

RESULTS

The overall PCR positivity for HHVs was 25·4%. HHVs types 1-3 were not detected in any donor sample. A specimen with high level of HHV-6 DNA (1,580,400 copies per mL) was recorded. HHV-4 DNA positivity was significantly associated with rural residency.

CONCLUSION

HHV-4 DNA is commonly detected in whole blood specimens of healthy individuals. HHVs types 5, 6 and 8 are rarely detected. However, the existence of a donor sample with high HHV-6 viral load raises questions regarding the potential risk of HHV-6 blood-borne infection and the safety of blood products.

Seroprevalence of HHV-6 and HHV-8 among blood donors in Greece

Background

Herpes viruses infection transmitted through healthy but infected blood donors pose a danger to herpes-naive immunocompromised recipients. The risk of transfusion-related HHV-8 transmission is different in endemic and not endemic areas. HHV-6 and HHV-8 seroprevalence and viral load among blood donors have been reported from different countries. The aim of our study was to assess the seroprevalence of HHV-8 and HHV-6 in volunteer blood donors from Greece which is unknown.

Findings

Serum samples from 179 healthy blood donors were tested for the presence of IgG antibodies against HHV-6 and HHV-8 with ELISA. None of the 179 donors of Greek origin tested was positive for HHV-8. HHV-6 seropositivity was assessed in 160 blood donors’ samples and was found to be 78.75% (126/160). The HHV-6 seroprevalence did not differ either between males and females or among different decade age groups.

Conclusions

The fact, that no blood donor was positive for HHV-8 IgG antibodies indicates that the risk for transfusion related HHV-8 transmission in Greece, if any, is negligible and does not warrant broad testing for HHV-8. Definitely further studies are needed, in order to clarify the potential risk of HHV-6 transmission.

Human Herpesvirus 6 Infection in Hemodialysis and Peritoneal Dialysis Patients

Background

Human herpesvirus 6 (HHV-6) infection occurs worldwide and can be reactivated from latency during periods of immunosuppression, especially after organ transplantation. No previous study has evaluated the influence of dialysis type on HHV-6 infection. The aim of the present study was to determine the prevalence of HHV-6 antibodies in hemodialysis (HD) and peritoneal dialysis (PD) patients.

Methods

W e studied 36 PD patients, 35 HD patients, and 20 healthy subjects, all with no history of organ transplantation. After systematic inquiries and a physical examination, blood was drawn for determination of biochemical parameters, cytomegalovirus immunoglobulin M (IgM) and immunoglobulin G (IgG), hepatitis B surface antigen, and the hepatitis C and human immunodeficiency virus antibodies. Titers of HHV-6 IgM and IgG antibodies were determined by ELISA.

Results

Titers for HHV-6 IgM antibody were positive in 9 HD patients (25.7%), 8 PD patients (22.2%), and 2 control subjects (10.0%, p > 0.05). More HD patients (20.0%) than PD patients (5.6%, p = 0.07) or control subjects (0.0%, p =0.03) were positive for HHV-6 IgG antibody. In HD patients, HHV-6 IgG seropositivity and duration of dialysis were positively correlated (R = 0.33, p = 0.05).

Conclusions

Infection with HHV-6 is not rare in PD and HD patients. In addition, HHV-6 IgG seropositivity was significantly higher in H D patients than in control subjects and approached significance when compared with seropositivity in PD patients. Moreover, in HD patients, HHV-6 IgG seropositivity correlated with duration on HD. These preliminary findings provide insight into the pre-transplantation period for patients and may aid our understanding of how to best protect patients against HHV-6 after transplantation.

Human herpesvirus 6 infection as a trigger of multiple sclerosis

We systematically reviewed the existing evidence to determine whether a relationship exists between infection with human herpesvirus 6 (HHV-6) and multiple sclerosis (MS) and, if so, to define the strength of that relationship. The following terms were used in searches of the Entrez-PubMed database (1966-2009): human herpes virus 6, HHV 6, demyelination, multiple sclerosis, pathogenesis, diagnosis, serology, cerebrospinal fluid, IgG antibodies, IgM antibodies, PCR, and lymphoproliferative techniques. Study quality was assessed using the criteria proposed by Moore and Wolfson and by the classification criteria used by the Canadian Task Force on the Periodic Health Examination. Studies were categorized both by experimental technique and by quality (high [A], intermediate [B], and low [C]) as determined by the Moore and Wolfson criteria. Overall, 25 (41%) of 61 studies, 15 (60%) of which were classified as A quality, reached a statistically significant result. According to the Canadian Task Force classification, all studies were categorized as evidence of quality II-1. Limitations of the available experimental techniques and perspectives for future research are discussed. The current review supports the need for further, objective, evidence-based examination of the relationship between HHV-6 infection and multiple sclerosis.

Effect of (r)-9-[4-hydroxy-2-(hydroxymethyl)butyl]guanine (H2G) and AZT-lipid-PFA on human herpesvirus-6B infected cells

BACKGROUND

Human herpesvirus-6 (HHV-6) has been associated with a wide spectrum of diseases. (r)-9-[4-Hydroxy-2-(hydroxymethyl)butyl]guanine (H2G) is an acyclic guanosine analogue that is structurally similar to acyclovir and is in clinical development for treatment of herpesvirus infections. H2G has been found to have activity against HSV type 1, HSV type 2, and HHV-6 in lymphoblast cell lines. A new anti-viral duplex drug, 3'-azido-3'-deoxythymidylyl-(5'-->2-O)-3-O-octadecyl-sn-glycerol (AZT-lipid-PFA), linking zidovudine (AZT) and foscarnet (PFA) via a lipophilic octadecylglycerol residue (lipid) also exhibits anti-viral activities against HIV, HSV type 1 and HCMV.

OBJECTIVE

To assess the efficacy of H2G and AZT-lipid-PFA conjugate against HHV-6.

STUDY DESIGN

Drug-associated toxicity and proliferative response were evaluated. We conducted in vitro experiments to determine the efficacy of H2G and an AZT-lipid-PFA conjugate in interfering with expression HHV-6 viral transcript in primary human peripheral blood mononuclear cells (PBMC).

RESULTS

Both H2G and AZT-lipid-PFA were effective at inhibiting expression of HHV-6 gene transcript at comparable concentrations. Additionally, while AZT-lipid-PFA treatment was toxic to cells at concentrations above 5microM, H2G treatment was associated with minimal cytotoxicity.

CONCLUSION

These data suggest the potential application of these anti-viral compounds in controlling HHV-6 infection.

Herpesvirus prevalence and viral load in healthy blood donors by quantitative real-time polymerase chain reaction

BACKGROUND

After primary infection, human herpesviruses (HHVs) maintain long-term latent persistence, often punctuated years later by sporadic episodes of symptomatic lytic activation. Also, blood-borne herpesvirus from healthy persistently infected blood donors can lead to active primary infection of immunocompromised transfusion recipients.

STUDY DESIGN AND METHODS

Utilizing a set of newly developed real-time polymerase chain reaction assays for detection and quantification of all eight human herpesviruses, the prevalence and viral DNA load of white cell-enriched blood from 100 randomly selected blood donors from the southeast Texas region are reported.

RESULTS

Herpes simplex viruses 1 and 2 (HSV-1 and HSV-2), varicella-zoster virus (VZV), and HHV-8 DNA were not detected in any donor sample. In contrast, Epstein-Barr virus (EBV) (72%) and HHV-7 (65%) were commonly detected, HHV-6 (30%) was often detected (Type B only), and cytomegalovirus (CMV; 1%) was rarely detected. Median viral loads of positive samples (per milliliter of blood) ranged from 4278 for HHV-6 to less than 46 for EBV.

CONCLUSIONS

These results suggest that the potential for transfusion-mediated transmission of herpesviruses from healthy adult blood donors is high for EBV and HHV-7; moderately high for HHV-6; uncommon for CMV; and rare for HSV-1, HSV-2, VZV, and HHV-8. Perhaps the most remarkable finding in this study was the detection of a single donor sample with greater than 6.1 x 10(7) HHV-6 Type B genome equivalents per mL blood. Given that this extraordinarily high level of HHV-6 DNA was obtained from a healthy adult blood donor, this phenomenon is likely unrelated to active infection or immunodeficiency.

A mu-capture immunoassay for detection of human herpes virus-6 (HHV-6) IgM antibodies in human serum

BACKGROUND

Human herpes virus-6 (HHV-6) was first isolated in 1986. It has been shown to cause exanthema subitum and has been associated with various other diseases. HHV-6 infection is widespread, and more than 90% of the population have antibodies against HHV-6 at the age of 2 years. Once acquired, the virus remains latent in the body. This makes it difficult to draw any conclusions about a causal relationship between the demonstration of HHV-6 and a specific disease.

OBJECTIVES

This work was to develop a mu-capture HHV-6 IgM enzyme linked immuno sorbent assay (ELISA) for use in routine diagnosis and for wide scale patient population analysis.

STUDY DESIGN

A mu-capture HHV-6 IgM ELISA was established. A total of 682 sera consisting of 585 sera from Danish blood donors and 97 sera from patients with autoimmune antibodies were analysed in the HHV-6 IGM ELISA. One hundred and ninety-two sera had earlier been analysed for total HHV-6 antibody content in a competitive ELISA, 94 sera were analysed for cytomegalovirus (CMV) IgM and 57 sera for Epstein Barr virus (EBV) antibodies, using different ELISA assays. The results for 12 primary infections with HHV-6 are also reported.

RESULTS

A HHV-6 IgM optical density (OD)-ratio was calculated according to a constant positive control. An empirical cut off of 0.5 HHV-6 IgM OD-ratio was chosen (with regard to the 10 HHV-6 seroconverters), which resulted in a specificity of 97.5% of the HHV-6 IgM ELISA. Two of the three donor sera with HHV-6 IgM OD-ratios more than 1.05 had total HHV-6 antibody titers significantly above the group with IgM OD-ratios below 0.7 consisting with HHV-6 reactivation. There was no cross reactions to EBV or CMV IgM positive sera.

CONCLUSION

The HHV-6 IgM ELISA seems valid to diagnose primary HHV-6 infection in particular in combination with the HHV-6 total antibody assay.

Human herpes virus 6 and multiple sclerosis

OBJECTIVES

To systematically review the published evidence for a relationship between human herpes virus 6 (HHV-6) and multiple sclerosis (MS).

MATERIALS AND METHODS

The medical literature was searched using MEDLINE and the Cochrane database. Retrieved studies are presented according to the experimental technique(s) used. The studies are rated for quality using a priori defined criteria.

RESULTS

Twenty-eight studies were retrieved. A total of 12 different experimental techniques were used. Four of these techniques provided evidence for a relationship between HHV-6 and MS, but none were able to show a causative relationship.

CONCLUSIONS

The available literature provides some support for a relationship between HHV-6 and MS. The limitations of the available studies and directions for future research are discussed.

Human herpesvirus 6 and human herpesvirus 7: emerging pathogens in transplant patients

Human herpesvirus 6 (HHV-6) and HHV-7 are two recently identified beta-herpesviruses, genetically related to human cytomegalovirus (CMV). Infection with both viruses is common worldwide with rates of seropositivity in adults over 90%. Infection with both viruses usually occurs in early childhood. In this age group HHV-6 is a cause of febrile illness including exanthem subitum, and likewise, primary HHV-7 infection has been associated with febrile illness. Similar to the other human herpesviruses, in particular CMV, the viruses have the potential for enhanced pathogenicity in the immunocompromised host. Active infection with both viruses is common following bone marrow or solid organ transplantation, most likely through reactivation of recipient's virus or re-infection considering their high prevalence in the population. Both viruses can be detected by PCR in the peripheral blood of healthy individuals and although the significance of blood-borne transmission is not clear, a preliminary study suggested that it was not significant for HHV-6. However, there is growing evidence that these viruses may be medically important in the post-transplant period. In bone marrow transplant patients HHV-6 has been associated with a range of clinical disease including encephalitis, interstitial pneumonitis, early and late graft failure and bone marrow suppression. There is also growing evidence for potential interactions among the beta-herpesviruses in liver and renal transplant patients. HHV-6 infection has been associated with an increased risk of developing CMV disease and opportunistic infections and HHV-7 infection has also been linked to an increased risk of CMV disease.

Clinical impact of human herpesvirus 6 infection after liver transplantation

BACKGROUND

Reactivation of human herpesvirus 6 (HHV-6) appears to be common after transplant. Viral reactivation may result in febrile illness and may also play an immunomodulatory role that leads to indirect effects such as opportunistic infections and rejection. The objective of this study was to determine the clinical impact of HHV-6 infection after liver transplantation including both direct and indirect effects.

METHODS

This was a prospective single center cohort study of 200 consecutive patients undergoing liver transplantation. Systemic serial HHV-6 viral load measurements and all clinical outcomes including development of opportunistic infections, cytomegalovirus (CMV) disease, and rejection were determined.

RESULTS

HHV-6 infection (defined as viral load > or = 2 log10 copies/microg input DNA) occurred in 56/200 (28%) patients. Symptomatic disease attributable to HHV-6 alone occurred in 2/200 (1%) patients. Univariate analysis revealed HHV-6 infection was associated with the development of opportunistic infection and CMV disease. In a multivariate analysis designed to control for the level of immunosuppression, the risk of opportunistic infection increased by 3.68-fold in patients with HHV-6 infection (95% confidence interval [CI], 1.86-7.27; P=0.001). In a similar multivariate analysis, the risk of CMV disease increased by 3.59-fold in patients with HHV-6 infection (95% CI, 1.53-8.44; P=0.003). HHV-6 infection was not associated with rejection except in the subgroup of patients with rejection after 30 days posttransplant (odds ration 2.27; 95% CI, 1.09-4.77; P=0.029).

CONCLUSIONS

HHV-6 reactivation after transplant is common and is associated with the development of opportunistic infections and CMV disease and possibly with a subgroup of acute rejection episodes. HHV-6 infection likely has a significant impact in transplant recipients through indirect effects of viral replication.

Human herpesvirus 6: its impact and influence on infectious diseases and their management

Human herpesvirus (HHV)-6 was discovered 15 years ago and was then grouped as a member of the family human herpesviridae. Its first clinical manifestation was identified 2 years later as the agent responsible for exanthem subitum. With the advent of newer molecular techniques, its diagnosis is easier and prospective studies have shown that it is the most common pathogen responsible for febrile illness in infants. In some infants, it is associated with febrile convulsions. Two subtypes, A and B, have been identified, B subtype commonly being responsible for primary infection in infants. Primary infection in healthy adults is rare. Most of the clinical manifestations are mild, self-limiting and rarely fatal. Reactivation of HHV-6 is frequently found in bone marrow as well as solid organ transplant recipients. HHV-6 has been shown to be an independent risk factor responsible for recurrence of cytomegalovirus infection, especially in solid organ transplants. In bone marrow transplant recipients, HHV-6 has been associated with various manifestations like marrow suppression and graft versus host disease, although most infections present as usually mild febrile illness with or without rash. It has been reported to cause encephalitis in transplant recipients. Although HHV-6 has been shown to be responsible for upregulation of HIV in vitro studies, its exact role in AIDS is yet to be defined. In addition to its neurotropic manifestation of febrile convulsion in infancy, it has been found in plaques in the brain of multiple sclerosis and progressive multifocal leukoencephalopathy. Further studies are needed before its role in the pathogenesis of these neurological illnesses can be established. Its lymphotropic feature was responsible for its discovery and now it has only been detected in some lesions of primary ocular mucosa associated lymphoid tissue lymphoma. As HHV-6 is found to be responsible for more and more illnesses, especially causing serious illnesses in the immunocompromised, it is becoming necessary to find effective treatment. Some agents, like cidofovir and phosphonoformic acid, are effective in in vitro studies and some have shown effectiveness in a clinical setting. Further studies are needed to identify its role in the pathogenesis of various neurological and malignant lesions and AIDS. Various treatment regimens should be tested in clinical scenario and especially in immunocompromised transplant recipients.

Herpesviruses in HIV-periodontitis

BACKGROUND/AIMS

Human herpesvirus-associated diseases exhibit elevated morbidity and mortality in patients infected with human immunodeficiency virus (HIV). This study aimed to investigate the occurrence of herpesviruses in HIV-periodontitis.

METHOD

Gingival biopsies from periodontitis lesions of 21 HIV-patients and 14 non HIV-patients were studied. Nested-polymerase chain reaction methods were employed to detect human cytomegalovirus, Epstein-Barr virus type 1 and 2 (EBV-1, EBV-2), herpes simplex virus, human herpes virus (HHV)-6, HHV-7 and HHV-8.

RESULTS

Gingival biopsies from HIV-periodontitis lesions showed on average 4.0 herpesvirus species and gingival biopsies from HIV periodontitis lesions of non-HIV patients revealed an average of 1.9 herpesvirus species (p<0.001). Occurrence of 4 to 6 different herpesviruses was more common in HIV- than in non HIV-gingival biopsies (71% vs. 7%) (p<0.001). EVB-2 was detected in 12 (57%) biopsies from HIV-periodontitis but was absent in non HIV-periodontitis biopsies (p= 0.002). HHV-6 also occurred in significantly higher frequency in HIV-periodontitis (71%) than in non HIV-periodontitis (21%) (p=0.01). HHV-8 was detected only in biopsies from HIV-periodontitis lesions..

CONCLUSION

HIV-periodontitis seems to be associated with elevated occurrence of EBV-2, HHV-6 and herpesvirus co-infections compared to periodontitis in non-HIV-patients. The periodontopathic significance of herpesviruses in HIV-periodontitis constitutes a research topic of considerable interest.

Predictive value of quantitative PCR-based viral burden analysis for eight human herpesviruses in pediatric solid organ transplant patients

Human herpesviruses can cause significant morbidity and mortality in pediatric solid organ transplant recipients. It was hypothesized that viral burden quantification by polymerase chain reaction using an internal calibration standard could aid in distinguishing between viral disease and latency. Here we report the results of a 2-year prospective study of 27 pediatric solid organ (liver, kidney, or heart) transplant recipients in which multiple samples were analyzed for levels of all eight human herpesviruses by internal calibration standard-polymerase chain reaction. Herpes simplex viruses 1 and 2, varicella-zoster virus, and Kaposi's sarcoma-associated herpesvirus were not detected in any of these samples. Human herpesvirus types 6 and 7 were detected in half of the patients, but were present at low levels, similar to those found in reference populations. Epstein-Barr virus (EBV) and cytomegalovirus (CMV) were detected in 89% and 56% of the patients, respectively. Viral burden analysis suggested distinct patient populations for CMV, with a natural cutoff of 10,000 viral targets/ml blood strongly associated with disease. In some cases, a dramatic increase in CMV levels preceded clinical evidence of disease by several weeks. EBV viral burden was relatively high in the only patient presenting with an EBV syndrome. However, two other patients without evidence of EBV disease had single samples with high EBV burden. Rapid reduction in both EBV and CMV burden occurred with antiviral treatment. These data suggest that viral burden analysis using internal calibration standard-polymerase chain reaction for CMV, and possibly other herpesviruses, is an effective method for monitoring pediatric transplant patients for significant herpesvirus infection and response to therapy.

Presence of human beta- and gamma-herpes virus DNA in Hodgkin's disease

Herpes viruses have been implicated in the etiology of Hodgkin's disease (HD). We studied the prevalence of human cytomegalovirus (CMV), human herpes viruses type-6 (HHV-6), type-7 (HHV-7) and type 8 (HHV-8) DNA in up to 88 Hodgkin's disease biopsies in comparison to Epstein-Barr virus (EBV) DNA by polymerase chain reaction (PCR). Non-Hodgkin lymphomas (NHL) and reactive lesions served as controls. CMV and HHV-6 were found in 8/86 (9%) and 11/88 (13%) HD cases, respectively, by nested primer PCR. Except for three cases harbouring HHV-6 type-B, only HHV-6 type-A was detected in HD. HHV-7 was observed by nested PCR in 33/88 (38%) HD cases and was already detectable in 15/88 (17%) HD cases by a single-round PCR indicating elevated virus copy numbers. Seven of these cases showed co-infection with HHV-6, and 11 cases were found to contain EBV DNA. 7/8 CMV-positive HD cases also harboured EBV DNA. HHV-8 DNA was not detected by single round or nested PCR in any HD case investigated. Thus, CMV, HHV-6, and HHV-7 were present in small proportions of HD cases, with frequent co-infection of HHV-6 and HHV-7, and frequent association with EBV. In contrast to EBV, beta-herpes viruses are therefore unlikely to have a role in the aetiology of HD. Rather, the presence of these viruses seems to reflect impaired immunological surveillance.

Human herpesvirus 6 and multiple sclerosis: systemic active infections in patients with early disease

By means of immunohistochemical staining, cells actively infected with human herpesvirus 6 (HHV-6) were found in central nervous system tissues from 8 (73%) of 11 patients with definite multiple sclerosis (MS). Interestingly, 17 (90%) of 19 tissue sections showing active demyelination were positive for HHV-6-infected cells compared with only 3 (13%) of 23 tissue sections free of active disease (P<.0001). Central nervous system tissues from 2 of 28 normal persons and patients with other inflammatory demyelinative diseases were positive for HHV-6-infected cells (P<.0001), and the 2 positive cases were diagnosed as having HHV-6 leukoencephalitis. By use of a rapid culture assay, blood samples from 22 (54%) of 41 patients with definite MS were found to contain active HHV-6 infections, compared with 0 of 61 normal controls (P<.0001). No significant difference was found between HHV-6 viremia-positive and HHV-6 viremia-negative MS patients with respect to type of disease (relapsing/remitting or progressive). In contrast, patients with active HHV-6 viremia were significantly younger and had shorter durations of disease than did HHV-6 viremia-negative patients.

Human herpes virus-6 seroprevalence and leukaemias: a case-control study. GIMEMA (Gruppo Italiano Malattie Ematologiche dell' Adulto)

The relationships between acute myeloid leukaemia (AML), acute lymphocytic leukaemia (ALL), chronic myeloid leukaemia (CML) and refractory anaemia with excess of blasts (RAEB) and human herpes virus (HHV)-6 antibody level were investigated in a multicentre case-control study. An association between increased HHV-6 seropositivity and geometric mean titre ratio with AML was shown: P for trend = 0.022, adjusted odds ratio 1.20, 95% confidence interval 1.07-1.33 respectively. No association was found between HHV-6 and ALL, CML or RAEB.

Human herpesvirus type 6 variants identified by single-strand conformation polymorphism analysis

Six human herpesvirus 6 (HHV-6) variants were analyzed for heterogeneity using the polymerase chain reaction (PCR) and single-strand conformation polymorphism (SSCP). Two independent DNA regions were selected: a fragment of the gene U11 (position 18966-21578) coding for a basic phosphoprotein, the major antigenic structural protein pp100; and a fragment from an open reading frame (ORF) area of the gene U67, previously referred to as 13R (position 102458-103519), coding for a product of unknown function. The two PCR systems based on the above DNA sequences yielded products of 187 bp and 223 bp, respectively. DNA obtained from three laboratory reference strains (U1102, R104 and St.W.) and from HHV-6 infected peripheral white blood cells of bone marrow transplant patients and blood donors was used to test the applicability of two different SSCP analysis systems for the identification of HHV-6 variants using amplicons derived by PCR from the two genomic regions described above (U11 [pp100], U67 [13R-ORF]). The generation of characteristic SSCP patterns enables the rapid differentiation of HHV-6 A and B strains for the classification of variants derived from clinical samples, reducing the need for expensive and time-consuming direct sequencing analyses.

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.

Herpesvirus 6 variant A infection after heart transplantation with giant cell transformation in bile ductular and gastroduodenal epithelium

Herpesvirus 6 (HHV-6) is a ubiquitous virus known to cause febrile syndromes and exanthema subitum in children. Less commonly, and particularly in organ transplant recipients, it may result in hepatitis, bone marrow suppression, interstitial pneunonitis, and meningoencephalitis. This report expands the spectrum of clinical disease associated with HHV-6 by documenting viral infection in a 44-year-old heart transplant recipient presenting with gastroduodenitis, pancreatitis, and hepatitis. On histopathologic examination, the gastric, duodenal, and bile ductular epithelium showed a multinucleate giant cell transformation similar to the cytopathic effect caused by the virus in human T-lymphocytes infected in vitro. Electron microscopy showed herpes particles with a thick tegument layer in the duodenum. Polymerase chain reaction amplified HHV-6 variant A sequences from multiple sites. Serology confirmed the presence of an acute HHV-6 infection. Thus, HHV-6 variant A can cause gastroduodenitis and pancreatitis in immunosuppressed individuals. Multinucleate giant cells and enveloped virions with a prominent tegument can be used as morphologic criteria to raise the possibility of HHV-6 infection in human biopsy tissue.

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.

A prospective study of human herpesvirus type 6 detected by polymerase chain reaction after liver transplantation

Human herpesvirus type 6 (HHV-6) causes roseola infantum (exanthema subitum) upon primary infection in young children. Thereafter it persists lifelong in the organism. Like other herpesviruses, HHV-6 can be reactivated in periods of immunosuppression - e.g., after organ transplantation. In order to study the incidence and the time to reactivation after orthotopic liver transplantation (OLT) we tested buffy coat lysates before and up to 10 weeks after transplantation for the presence of HHV-6 DNA by polymerase chain reaction (PCR). Forty-six patients (male n=27, female n=19) with a median age of 48 years (range 20-66) were studied. Altogether, 30 of 287 (10.5%) buffy coat samples were PCR-positive. Before OLT 2 of 21 (9.5%) patients were positive. This ratio is not different from healthy blood donor controls. After OLT 13 of 46 (23.8%) patients were positive on one or more occasions. However, there was no statistically significant difference before and after OLT. Ten patients were analyzed for HHV-6 variants by restriction enzyme digestion of PCR products. One patient carried variant A and 9 variant B. In conclusion, HHV-6 can be detected in buffy coat cells after OLT. Our observations do not argue in favor of a reactivation.