Prevalence of human herpesvirus 6 variant A and B infections in bone marrow transplant recipients as determined by polymerase chain reaction and sequence-specific oligonucleotide probe hybridization

Cord-blood hematopoietic stem cell transplant confers an increased risk for human herpesvirus-6-associated acute limbic encephalitis: a cohort analysis. Biol Blood Marrow Transplant. 2012;18:1638-1648. [PMID: 22564265 DOI: 10.1016/j.bbmt.2012.04.016]

Human herpesvirus-6 (HHV-6) frequently reactivates after allogeneic hematopoietic stem cell transplantation (HSCT); its most severe manifestation is the syndrome of posttransplantation acute limbic encephalitis (HHV-6-PALE). The epidemiology, risk factors, and characteristics of HHV-6-PALE after unrelated cord-blood transplantation (UCBT) are not well characterized. We analyzed 1344 patients undergoing allogeneic HSCT between March 2003 and March 2010 to identify risk factors and characteristics of HHV-6-PALE. The cohort included 1243 adult-donor HSCT and 101 UCBT recipients. All patients diagnosed with HHV-6-PALE had HHV-6 DNA in cerebrospinal fluid (CSF) specimens in addition to symptoms and studies indicating limbic encephalitis. Nineteen cases (1.4%) of HHV-6-PALE were identified during this study: 10 after UCBT (9.9%) and 9 after adult-donor HSCT (0.7%), for an incidence rate of 1.2 cases/1000 patient-days compared to 0.08 cases/1000 patient-days (P < .001), respectively. Risk factors for HHV-6-PALE on multivariable Cox modeling were UCBT (adjusted hazard ratio [aHR], 20.0; 95% confidence interval [CI], 7.3-55.0; P < .001), time-dependent acute graft-versus-host disease (aGVHD) grades II to IV (aHR, 7.5; 95% CI, 2.8-19.8; P < .001), and adult-mismatched donor (aHR, 4.3; 95% CI, 1.1-17.3; P = .04). Death from HHV-6-PALE occurred in 50% of affected patients undergoing UCBT and no recipients of adult-donor cells. Patients receiving UCBT have increased risk for HHV-6-PALE and greater morbidity from this disease.

Development of a human herpesvirus 6 species-specific immunoblotting assay

In order to assess the full spectrum of human herpesvirus 6A (HHV-6A)- and HHV-6B-associated diseases, we sought to develop an HHV-6 species-specific serological assay based on immunoblot analysis. The immunodominant proteins encoded by open reading frame U11, p100 for HHV-6A (strain U1102) and 101K for HHV-6B (strain Z29), were selected to generate virus species-specific antigens. Recombinant p100 and 101K were produced in a prokaryotic expression system. The expression of these proteins was confirmed by using anti-His tag and 101K-specific monoclonal antibodies. HHV-6 species-specific antibodies were detected by immunoblotting in patient sera. Eighty-seven serum samples obtained from various subjects were utilized to determine the reliability of the method for clinical use. Ten of twelve exanthem subitum convalescent-phase sera reacted exclusively with 101K, whereas none of twelve acute-phase sera reacted with either protein. Two of three sera collected from HHV-6A-infected patients reacted with p100 and 101K. Although all five acute and convalescent-phase sera obtained from transplant recipients reacted exclusively with 101K, two of six convalescent-phase sera obtained from patients with drug-induced hypersensitivity syndrome reacted with both p100 and 101K. Of 38 sera obtained from healthy adults, 31 were positive for 101K antibody, while 4 reacted with both proteins. However, PCR analysis of peripheral blood mononuclear cells and saliva from these subjects did not detect HHV-6A DNA. In conclusion, this novel serological assay based on immunoblot analysis using recombinant HHV-6A p100 and HHV-6B 101K allowed us to discriminate between HHV-6A- and HHV-6B-specific antibodies.

Human herpesvirus-6 entry into host cells

Human herpesvirus-6 (HHV-6) belongs to the herpesvirus family and is categorized into variant A and B (HHV-6A and HHV-6B). Primary HHV-6 infection in children and its related diseases are almost exclusively caused by HHV-6B and no disease caused by HHV-6A has been identified. The cellular receptor of HHV-6 has been shown to be a human CD46, and its viral ligand is an envelope glycoprotein complex, gH/gL/gQ1/gQ2 in HHV-6A. Furthermore, both cellular and viral lipid rafts play an important role in the HHV-6 entry process, suggesting that HHV-6 may enter its target cells through a lipid raft-associated mechanism.

Multicenter external quality assessment of molecular methods for detection of human herpesvirus 6

The purpose of this study was to evaluate the performance of laboratories for the detection and quantification of human herpesvirus 6 (HHV-6) by an external quality assessment (EQA) evaluation. The HHV-6 EQA panel consisted of eight samples containing various concentrations of HHV-6 type A (strain GS) or type B (strain Z29), two samples containing other herpesviruses (i.e., human cytomegalovirus [HCMV] and Epstein-Barr virus [EBV]), and two HHV-6-negative samples. Panel samples were prepared in human plasma, heat inactivated, and lyophilized. Panel distribution, data management, and analysis were coordinated by Quality Control for Molecular Diagnostics (QCMD), Glasgow, United Kingdom. Fifty-one laboratories participated and submitted 57 data sets. Eleven (19.3%) data sets were generated using conventional in-house assays, 11 (19.3%) data sets using commercial real-time PCR assays, and 35 (61.4%) data sets using in-house real-time PCR assays. The presence of HHV-6 DNA at viral loads exceeding 6,000 copies/ml was detected by all participants, and over 80% of the participants still reported correct qualitative results for the sample containing just over 200 copies/ml. The false-positivity rate was 1.8% for both the negative samples and the samples containing HCMV or EBV DNA. The majority (23/33; 69.7%) of quantitative data sets were generated using in-house real-time PCR assays. The standard deviations of the geometric means of the samples ranged from 0.5 to 0.7 log(10). The results of this first international EQA demonstrate encouraging analytical sensitivity for the detection of HHV-6-DNA in human plasma, although we observed extensive interlaboratory variation of quantitative HHV-6 DNA results. Standardization needs to be improved to allow further elucidation of the clinical significance of HHV-6 loads.

Direct detection of human herpesvirus 6 DNA in serum by variant specific loop-mediated isothermal amplification in hematopoietic stem cell transplant recipients

A variant specific direct loop-mediated isothermal amplification (LAMP) method was developed to detect human herpesvirus-6 (HHV-6) variants in serum samples. Specific primers were designed against HHV-6 U86 gene. Initial validation analysis confirmed high specificity and sensitivity of the method. This method was shown to be highly reliable for monitoring active HHV-6 infection in hematopoietic stem cell transplant recipients.

Prevalence of infectious pathogens in Crohn’s disease. Pathol Res Pract. 2009;205:223-230. [PMID: 19186006 DOI: 10.1016/j.prp.2008.04.018]

The importance of infectious pathogens in Crohn's disease (CD) is still under debate. Therefore, we examined a panel of potential viral and bacterial pathogens in a large series of CD patients and controls. Archival tissue from 76 patients, 56 with CD and 20 control patients, with normal colon mucosa (n=10) and non-steroid anti-inflammatory drug (NSAID)-induced colitis (n=10) were examined using PCR-based detection methods for human cytomegalovirus (CMV), Epstein-Barr virus (EBV), herpes simplex virus 1, 2 (HSV1,2), adenovirus (AD), varicella-zoster virus (VZV), human herpes virus 6 (HHV6), human herpes virus 8 (HHV8), Mycobacterium tuberculosis complex (Mtbc), atypical mycobacteria (nM/MG1), including Mycobacterium avium (subspecies paratuberculosis, MAP), Stenotrophomonas maltophilia (Sm), and Yersinia enterocolitica (Ye). In CD patients, positive PCR results were achieved in 19 cases (34%). Sm was most frequent in 10 of 56 cases (17.9%) followed by EBV (6/56, 10.7%), nM/MG1 (4/56, 7.1%), including MAP, HHV6, and CMV (2/56, 3.6%), and finally Mtbc and AD (1/56, 1.8%). The control patients showed positive PCR results in 12 patients (12/20, 60%), nine of them with only weak signals, suggesting a persistent infection. In addition, we compared typical pathomorphological features of CD patients with the PCR results and found a significant correlation between EBV infection and mural abscesses (P=0.014). Our data demonstrate that several potential pathogens can be detected in a sizeable fraction of specimens from patients with CD, but also in control patients, suggesting that the analyzed infectious pathogens may be associated with the disease, but do not represent an obligatory cause.

Human herpesvirus-6 infections and infection-preventative measures in transplant recipients

Like the other herpesviruses, human herpesvirus (HHV)-6 is capable of persisting in the host after primary infection and can reactivate under immunosuppressed conditions. In stem cell transplantation recipients, HHV-6 reactivation is observed in 40–50% of patients and is linked to various clinical manifestations, including rash, delayed platelet engraftment and encephalopathy. HHV-6 reactivation is also relatively common in solid organ transplantation recipients, and is associated with graft dysfunction and subsequent development of human cytomegalovirus disease. In particular, HHV-6 has been recognized as a life-threatening pathogen for the development of encephalopathy after stem cell transplantation. Ganciclovir, foscarnet and cidofovir are effective against HHV-6 in vitro. However, success rates are not high for patients who have developed encephalopathy. Plasma HHV-6 DNA-guided pre-emptive approaches have not been successful owing to the dynamic kinetics of HHV-6 reactivation. Establishment of optimal strategies is needed to prevent HHV-6-associated complications, in particular encephalopathy.

Loop-mediated isothermal amplification for discriminating between human herpesvirus 6 A and B

Genotyping of human herpesvirus 6 (HHV-6) is important clinically, particularly for the diagnosis of neurological diseases. The objective of this study was to establish a rapid HHV-6 genotyping method using the loop-mediated isothermal amplification (LAMP) method. An AccI site is located in the target sequence of HHV-6 B, but not in HHV-6 A. LAMP products were digested with the AccI enzyme and then separated by agarose gel electrophoresis to differentiate the digest pattern of the two variants. The fragment patterns were clearly different between HHV-6 A and B. In order to evaluate the reliability of this HHV-6 genotyping method for use in the clinical laboratory, serum samples from 20 patients with either primary HHV-6 infection or viral reactivation were collected and analyzed. HHV-6 DNA was amplified directly from the serum samples and all 20 LAMP products were positive for HHV-6 B.

Emerging viral infections in transplantation

Viral infections are an important complication of transplantation. The introduction of more potent immunosuppressive agents over the past decade correlates with an increase in the rate of hospitalizations of transplant patients with infections. Specifically, viral infections have emerged as a major source of morbidity and mortality in transplantation. There are several potential intervention strategies in the face of emerging infections and it is likely that the approach will differ depending on the virus in question. These include viral surveillance and pre-emptive therapy, intervention of the transplant community, and policy change at the level of government, blood bank and organ procurement organizations. This review focuses on the emergence of the herpesviruses; HHV-6 and HHV-7. In addition, the issue of virus transmission through organ transplant is addressed with a discussion of West Nile virus and the rabies virus.

Human herpesvirus 6 (HHV-6) U94/REP protein inhibits betaherpesvirus replication

Human herpesvirus 6 (HHV-6) is the only human herpesvirus encoding U94/rep, homologue to the parvovirus non-structural gene rep68/78. Results to date suggest that HHV-6 U94/rep might regulate viral gene expression and have a role in viral latency. To determine the effect of U94/REP upon viral replication, the protein was produced. The purified U94/REP retained the characteristic immunological features. It was internalized and localized in the nucleus of human cells, showing marked inhibitory activity on the replication of HHV-6 (both variants A and B). The effect of U94/REP was dose-dependent and sensitive to treatment with single-stranded but not double-stranded DNA. U94/REP inhibited the replication of other betaherpesviruses, HHV-7 and human cytomegalovirus, but had no effect on herpes simplex virus. These results confirm the action of U94/rep latency gene in the regulation of HHV-6 replication with implications for co-reactivations and latency of human betaherpesviruses.

Human herpesvirus-6 and -7 in pediatric stem cell transplantation

BACKGROUND

Human herpesvirus-6 (HHV-6) and -7 (HHV-7) may reactivate with immunosuppression and cause symptoms varying from subclinical to severe organ manifestations. The presence of HHV-6 and -7 and their possible association with clinical problems among pediatric recipients of stem cell grafts was studied in a single institution setting between November 1999 and December 2001.

PROCEDURE

A total of 60 patients, mean age 8.5 years, were transplanted: 2/3 received allogeneic grafts and 1/3 autologous stem cell rescue. The presence of HHV-6 and -7 was studied in blood by polymerase chain reaction (PCR) (HHV-6) and antigenemia (HHV-6 and -7).

RESULTS

Both HHV-6 and -7 were frequently present in the blood of stem cell graft recipients. No significant difference in the incidence of HHV-6 or -7 reactivations between the allogeneic and autologous patients nor recipients of sibling or unrelated donor (URD) grafts was observed. HHV-6 antigenemia was associated with fever, rash, and delayed engraftment. Among symptomatic patients two cases of encephalitis were encountered with both having HHV-6 detectable in their cerebrospinal fluid (CSF) by PCR.

CONCLUSIONS

HHV-6 and -7 seem to be common in blood both pre- and post-transplant among pediatric recipients of stem cell grafts. Prolonged reactivations appear to correlate with clinical symptoms such as fever, rash, and bone marrow suppression in the post-stem cell transplant setting (SCT), but severe complications are rare. Transient reactivations appear to be of very limited clinical significance.

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

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

Effect of antivirals on human herpesvirus 6 replication in hematopoietic stem cell transplant recipients

Human herpesvirus 6 (HHV-6) appears to cause central nervous system (CNS) syndromes, especially in hematopoietic stem cell transplant (HSCT) recipients. We reviewed our experience with HHV-6-associated CNS disease to evaluate both the clinical and virological presentation and response to antiviral therapy. A search of our virology database from January 1998 through June 2000 identified 11 HSCT recipients who had HHV-6 DNA detected by polymerase chain reaction in cerebrospinal fluid (CSF); 8 of whom had CNS dysfunction without another clear etiology identified. HHV-6 levels in serum and CSF were evaluated before and after ganciclovir and/or foscarnet therapy. Median log HHV-6 CSF levels appeared to decrease over time concurrent with antiviral therapy (serum level, 2.0 vs. 0 copies/mL [P=.38]; CSF level, 4.4 vs. 2.0 copies/mL [P=.13], sign test). Our data suggests that HHV-6 may cause moderate to severe CNS disease after HSC transplantation. Prospective studies are needed to define the spectrum of HHV-6-associated disease and to determine whether antiviral therapy offers clinical benefit.

(3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assays showed a lack of toxicity of ganciclovir (GCV), C.OXTs, and their derivatives, to TaY(OK) cells at 1 microM. Therefore we compared the antiviral potencies of these drugs at 1 microM by monitoring the viral loads produced during a 1-day period during the course of the drug treatment. Among the drugs tested, 3'-fluorocarbocyclic oxetanocin A (3'F-C.OXT-A) was the most effective for inhibiting the virus production, and at concentrations ranging from 0.5 microM to 10 microM, the inhibition of the viral production was dose-dependent. A comparison of the chemical structures of the derivatives with that of C.OXT-A, which is the parental molecule, suggested that the 3'-fluorine-modification might account for the higher anti-HHV-6 activity and lower cytotoxicity

An infection of TaY cells, which originated from an adult T-cell leukemia, with an HHV-6B OK isolate resulted in a chronically infected culture, termed TaY(OK). Cell cloning analysis revealed that the TaY(OK) culture consisted of a mixture of cells permissive and refractory to the infection, and that the permissive cells were continuously produced from the refractory cell population. Since the chronically infected culture has been maintained for over 2 years without the addition of uninfected TaY cells, we used it for an evaluation of the antiviral potency of nucleoside analogs, especially carbocyclic oxetanocins (C.OXTs).

Herpesvirus-6 encephalitis complicated by Wernicke-Korsakoff syndrome in a pediatric recipient of unrelated cord blood transplantation

A 10-year-old girl with M2 acute myeloid leukemia underwent an unrelated cord blood transplantation in refractory first relapse. On day +13, after 48 hours with fever, she showed a measles-like rash, and on day +15, she began experiencing neurologic symptoms (headache, tremors, weakness, nystagmus, mild confusion, speaking, taste, and behavior disturbances, and focal seizures). She also had amnesia for recent events with disability to learn, mimicking Wernicke-Korsakoff syndrome. Computed tomography of the brain and cerebrospinal fluid (CSF) and electroencephalogram were nonspecific. We found human herpesvirus 6 (HHV-6) DNA in CSF and cytomegalovirus in bronchoalveolar lavage using polymerase chain reaction techniques. Treatment with ganciclovir and foscarnet was effective, with total resolution of symptoms.

Human herpesvirus 6 reactivation and encephalitis in allogeneic bone marrow transplant recipients

To determine whether receipt of an investigational anti-CD3 monoclonal antibody (BC3) increased the risk of human herpesvirus 6 (HHV-6) reactivation and development of encephalitis in bone marrow transplant (BMT) recipients, persons who had and had not received BC3 were compared. Odds of HHV-6 reactivation were higher among BC3 recipients than among control patients (odds ratio, 2.5; 95% confidence interval [CI], 1.3-4.7). In addition, BC3 recipients were more likely than control patients to develop encephalitis (risk ratio [RR], 3.5; 95% CI, 1.3-9.5), and this association followed a BC3 dose-dependent relationship (P=.03, by Mantel-Haenszel chi(2) test). In a multivariable model, HHV-6 reactivation and receipt of BC3 were associated with increased risk of encephalitis (RR, 5.4; 95% CI, 1.9-15.3, and RR, 3.3; 95% CI, 1.2-9.1, respectively). In conclusion, both HHV-6 reactivation and receipt of BC3 for prophylaxis of acute graft-versus-host disease independently increased the risk of encephalitis in allogeneic BMT recipients. Prospective studies to better define the relationship between HHV-6 reactivation and encephalitis in allogeneic BMT recipients are warranted.

Inverse relationship between human herpesvirus-6 and -7 detection after allogeneic and autologous stem cell transplantation

Human herpesvirus-6 (HHV-6) and -7 were analyzed in 25 and 18 patients with allogeneic (allo) and autologous (auto) stem cell transplantation (SCT), respectively, by weekly examination of viral DNA in peripheral mononuclear cells using semiquantitative PCR and serologic tests up to 12 weeks after SCT. HHV-6 DNA was detected in 29.6% and 27.9% of samples after allo- and auto-SCT, respectively. The proportions of HHV-6-DNA-positive samples increased in week 3 and 4 after allo-SCT, and in week 1 to 3 after auto-SCT. The frequency of HHV-7 DNA detection, however, was higher after auto-SCT (24.7%) than allo-SCT (12.8%) (P 10(2) copies of HHV-6 DNA (/10(5) cells) on two consecutive occasions were allo-SCT recipients and three showed clinical episodes. Conversely, three of five patients with continuous reactivation of HHV-7 were auto-SCT recipients. Thus, the frequencies of HHV-6 and -7 DNA detection showed an inverse relationship comparing allo- and auto-SCT, suggesting a different mechanism may regulate HHV-6 and -7 reactivation.

Human herpesviruses-6, -7 and -8 in organ transplant recipients

The newer herpesviruses are being increasingly recognized as significant opportunistic pathogens in organ transplant recipients. Published data support the role of human herpesvirus-6 as a potential cause of encephalitis and bone marrow suppression in transplant setting. An association of human herpesvirus-6 with fungal infections and cytomegalovirus infection has also been documented. Human herpesvirus-7 also appears to be an immunomodulatory agent and may facilitate the pathogenicity of cytomegalovirus. Unlike human herpesviruses -6 and -7, human herpesvirus -8 is not ubiquitous; its seroprevalence exhibits wide geographic variation. Human herpesvirus-8 has been causally associated with post-transplant Kaposi's sarcoma. The complete spectrum of pathogenicity and ultimately the effective prophylaxis and management of these viruses has yet to be fully elucidated.

Human herpesvirus 6 is an important pathogen in infectious lung disease after allogeneic bone marrow transplantation

Two hundred and ten bronchoalveolar lavage (BAL) samples were obtained from 50 patients 10 days before and on defined days after allogeneic bone marrow transplantation (BMT). The samples were examined for human cytomegalovirus (HCMV) and human herpesvirus-6 (HHV-6) by polymerase chain reaction (PCR). Fifteen patients (30%) had a positive result for HCMV in at least one sample and 25 (50%) were positive for HHV-6 in at least one sample. Five patients developed HCMV-associated interstitial pneumonia (HCMV-IP) within 100 days after allogeneic BMT. Four of these patients were positive for both HCMV and HHV-6. Conspicuous HHV-6 positivity was detected in BAL samples obtained because of respiratory symptoms. No association was found between detection of HHV-6 and acute graft-versus-host disease. Engraftment failure or a delay in engraftment was observed in none of the 50 patients. The data from this study indicate that HHV-6 is a pathogen in HCMV-associated, as well as in non-HCMV-associated infectious lung disease after BMT.

Epidemiology of human herpesvirus 6 (HHV-6) infection in pregnant and nonpregnant women

BACKGROUND

Human herpesvirus 6 (HHV-6) is a ubiquitous virus primarily associated with benign conditions such as febrile syndromes and exanthem subitum (roseola infantum). Sexual, horizontal, and vertical transmission have been suggested. Little information is available regarding HHV-6 infection in women of reproductive age.

OBJECTIVE

Describe epidemiology of HHV-6 infection in pregnant and nonpregnant women.

STUDY DESIGN

The study sample consisted of 569 women, age 18-45, who attended a university family planning clinic (nonpregnant, n=224) and two obstetrics clinics (pregnant [first trimester], n=345) in San Antonio, TX between October 1995 and May 1998. Blood and a vaginal swab, as well as sociodemographic information, were collected from each participant. Plasma was tested for HHV-6 IgG antibodies using a standard immunofluorescence assay (IFA). Lysed material from vaginal swabs was tested for HHV-6 DNA by polymerase chain reaction (PCR). Products were screened by enzyme-linked immunosorbent assay and positive tests were confirmed by repeat PCR followed by Southern analysis. PCR-positive samples were subtyped using an established method.

RESULTS

All subjects were HHV-6 antibody positive. Geometric mean titers of HHV-6 antibodies were significantly higher among nonpregnant versus pregnant women. Moreover, a higher proportion of nonpregnant versus pregnant women had antibody titers >/=160 and >/=320. This association persisted even after adjusting for a number of sociodemographic and clinical factors. Low rates of HHV-6 shedding in the genital tract were observed for both groups (pregnant, 7/297 [2.0%]; nonpregnant, 8/214 [3.7%]). Of 14 samples subtyped, four (29%) were subtype A.

CONCLUSION

The present study showed that 100% of the study sample was infected with HHV-6. Higher HHV-6 antibody titers, however, were noted in nonpregnant women. Both groups shed virus at low rates in the genital tract. HHV-6 subtype A was identified more commonly than previously reported. Further longitudinal studies are required to assess the consequences of maternal HHV-6 infection.

HLA-mismatched CD34-selected stem cell transplant complicated by HHV-6 reactivation in the central nervous system

We report here a patient who suffered from PCR- confirmed human herpesvirus type 6 (HHV-6) meningoencephalitis after allogeneic purified CD34+ cell transplantation from his HLA-mismatched sibling donor, even though he had been on intense prophylaxis with i.v. ganciclovir (GCV), acyclovir (ACV) and gamma-globulin containing a specific antibody against HHV-6. Serological evaluation disclosed that both the donor and recipient had IgG antibody against HHV-6 before transplantation. His blood WBC count started to transiently increase on day 10, and all blood components had decreased by day 20. He then developed a severe headache and high blood pressure, and sporadic abnormal neurological findings including nystagmus and delirium. An analysis of cerebrospinal fluid (CSF) revealed 8 cells/microl, a glucose level of 130 mg/dl and a protein level of 201 mg/dl (normal, 50 mg/dl) on day 26. At the time, HHV-6 was detected only in CSF by a PCR-based method and he was diagnosed as having meningoencephalitis due to the local reactivation of HHV-6. Although he failed to respond to high-dose therapy with ACV (60 mg/kg/day) and gamma-globulin, the DNA of this virus disappeared from the CNS upon treatment with GCV (30 mg/kg/day) combined with the intraventricular infusion of alpha-interferon. His clinical course was further complicated with meningoencephalitis due to staphylococcus epidermidis, and he died of tentorial herniation on day 79 without the recovery of blood components. This experience may indicate that intense prophylaxis to prevent reactivation of HHV-6 in the CNS is essential for the management of such profoundly immunosuppressed patients.

Active site mutants of human herpesvirus-6 proteinase

Amino acid residues thought to comprise the catalytic triad of HHV-6 proteinase were changed by site-directed mutagenesis in the precursor form of the proteinase. By monitoring the ability of each mutant proteinase precursor to undergo autoprocessing, Ser116, His46 and His135 were identified as catalytically crucial. An attempt was made to mimic the catalytic triad arrangement of archetypal serine proteinases by replacement of the second histidine, His135, by an Asp. Instead of increasing the autoprocessing ability of the His135Asp mutant HHV-6 proteinase precursor, this mutation had a detrimental effect since the precursor persisted predominantly in its unprocessed form.

Cytomegalovirus and human herpesvirus 6 both cause viral disease after renal transplantation

BACKGROUND

Systemic viral disease after renal transplantation, especially after treatment with OKT3 or antithymocyte globulin, has usually been attributed to cytomegalovirus (CMV) infection. Identification of human herpesvirus 6 (HHV6) has raised the possibility that infection or reactivation of this virus may also occur in the same setting.

METHODS

We thus examined the incidence of CMV and HHV6 infection in a prospective blinded consecutive series of 30 renal and renal/pancreas transplant patients, 22 of whom received OKT3, antithymocyte globulin, or both.

RESULTS

Clinical diagnosis of a viral syndrome was made in 15 patients. Three patients with only HHV6 DNA in urine or serum had fever and abnormal liver function but not neutropenia. All five CMV-seronegative patients who received positive kidneys developed moderate to severe disease with fever and neutropenia but also had HHV6 DNA in urine or serum. Seven CMV-seropositive patients developed disease, mostly after OKT3/antithymocyte globulin, but six shed both CMV and HHV6 in urine or serum. The simultaneous detection of both HHV6 and CMV DNA in either urine or serum was the strongest predictor of disease (and also the severity of disease), with an odds ratio of 99.0 (95% confidence intervals 5.4-1814, P<0.002).

CONCLUSION

Most systemic viral disease after renal transplantation may be due to either coinfection or reactivation of CMV and HHV6 together. A wider understanding of risk factors for severe viral disease in this setting may come from testing for both viruses in all donors and patients in both clinical practice and clinical trials.

Human herpesvirus 6 infection and associated pathogenesis following bone marrow transplantation

Human herpesvirus 6 (HHV-6) infections following bone marrow transplantation (BMT) have been shown to be associated with fever, skin rash, graft versus host disease, encephalitis, delay in engraftment, marrow suppression, and pneumonia. Unfortunately several of these studies were case reports and although the results were suggestive they prompted us to study these pathological events systematically. These associations were primarily based on either HHV-6 isolation, HHV-6 DNA detection, antigen detection or increases in HHV-6 specific antibodies. HHV-6 activity was more frequent during the post- rather than the pre-transplantation period. All HHV-6 isolates from BMT patients have been shown to be variant B. A better understanding of HHV-6 associated pathogenesis gained by larger prospective trials is needed to facilitate proper treatment of cases of idiopathic illnesses or those associated with symptoms (fever, skin rash) similar to those caused by HHV-6.

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.

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.

Nucleotide sequence analysis of a 30-kilobase-pair region of human herpesvirus-6B (HHV-6B) genome and strain-specific variations in major immediate-early genes

Human herpesvirus 6 (HHV-6) is now classified into two distinct variants such as HHV-6 variant A(HHV-6A) and B(HHV-6B) (Ablashi et al., Arch. Virol. 129, 1993, 1-4) and the DNA of HHV-6A strain U1102 was completely sequenced (Gompels et al., Virology 209, 1995, 29-51). We have sequenced a 30-kilobase pair (kbp) (genomic positions around 111-141 kb) of HHV-6B strain HST, and a sequence of this region was compared with that of HHV-6A strain U1102. Dodecameric repeats, G/T and Kpn repeat elements, putative major immediate early 1 (MIE1) and major immediate early 2 (MIE2) genes were found in this region. The DNA sequences of HHV-6A (U1102) and HHV-6B (HSI) were markedly different in the MIE1 region, Kpn repeat elements and the putative MIE2 region. Dodecameric repeat element was located in the putative MIE2 locus of HHV-6. When primers covering dodecameric repeat region were used to amplify HHV-6 DNA of clinical isolates from patients with exanthem subitum (ES) by polymerase chain reaction (PCR), variations in size of PCR products in each isolate were found, indicating strain-specific features. Furthermore, the results of molecular biological analysis by PCR using DNA samples in a family suggest that HHV-6 infects within a family.

Human herpesvirus-6 infection in liver transplant recipients: documentation of pathogenicity

BACKGROUND

The new herpesvirus, human herpesvirus-6 (HHV-6), is able to cause clinical illness after transplantation; however, the pathogenic potential and the clinical features of HHV-6 have not been defined in liver transplant recipients.

METHODS

We report the first cases of invasive and symptomatic infection due to HHV-6 in liver transplant recipients.

RESULTS

HHV-6 infection occurred in four liver transplant recipients at a median of 50 days after transplant (range 17-90 days). Severe cytopenia was observed in all patients; leukopenia (with median leukocyte count of 1400/mm3) was the most commonly effected bone marrow lineage. One of the four patients had interstitial pneumonitis due to HHV-6. No other virus (e.g., cytomegalovirus) or another pathogen was detected in the lungs, blood, or bone marrow in any of the above patients.

CONCLUSIONS

Our data suggest that HHV-6 can be a pathogen in liver transplant recipients; idiopathic bone marrow suppression is its predominant clinical sequelae. Recognition of HHV-6 infection is clinically pertinent because HHV-6 is potentially treatable with the currently available antiviral agents.

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.

Detection and variant identification of HHV-6 by a non-radioactive hybridization microplate assay for amplimers detection

A non-radioactive hybridization microtiter plate assay was developed and evaluated for detection of the HHV-6 genome and to identify HHV-6 variants A and B. The viral DNA is amplified by the polymerase chain reaction using a 5'-end-biotinylated primer. The biotinylated amplimers are captured on avidin-coated microtiter plates, denaturated with sodium hydroxide and hybridized to a 3'-end-digoxigenin-labelled probe. Subsequently, anti-digoxigenin Fab fragments conjugated with alkaline phosphatase are used for the revelation of the hybridized probe. The result is obtained by measuring the intensity of light emitted with a spectrophotometer. This new assay was compared to the standard analysis of amplified products by Southern hybridization consisting of gel electrophoresis of the amplimers, transfer onto a nylon membrane, and hybridization with a 32P-labelled oligomeric probe. Both methods exhibited the same sensitivity and specificity. Thus, a non-radioactive hybridization microtiter plate assay may be a suitable alternative to isotopic techniques.

Coinfection with human herpesvirus 6 variants A and B in lung tissue

Human herpesvirus 6 (HHV-6) variant B is frequently identified in peripheral blood, but identification of HHV-6 variant A is relatively rare. We devised a PCR-based method for sensitive, simultaneous detection of both HHV-6 variants. The method was applied to 34 lung tissue specimens that were previously shown to contain HHV-6 DNA. A total of 22 lung tissue samples showed coinfections with HHV-6 variants A and B, 2 had only HHV-6 variant A DNA, and 10 had only HHV-6 variant B DNA. The prevalences of coinfections in lung tissues from healthy controls (54% coinfected) and in those from bone marrow transplant patients with pneumonia (67% coinfected) were similar. These data indicate that coinfections of HHV-6 variants A and B commonly occur in lung tissues of healthy and diseased individuals.

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.

Human herpesvirus-6 DNA in the saliva of paediatric oncology patients and controls

Children with malignancy are immunosuppressed and susceptible to serious infections with herpesviruses. The majority of children on chemotherapy for malignancy are seropositive for human herpesvirus-6 (HHV-6), and although HHV-6 has been demonstrated to be a pathogen in severely immunocompromised patients, whether this is the case for paediatric oncology patients is unknown. HHV-6 is secreted in saliva and in this study samples were examined prospectively for HHV-6 DNA in healthy children and those with malignancy. In a nested polymerase chain reaction (PCR), a 287 bp outer fragment and 163 inner fragment of HHV-6 DNA were amplified. The resulting amplimer contained a Hind III restriction site present only in "B" type HHV-6 and this was used to identify the type of HHV-6 amplified. In saliva from healthy control children, 74% (28/38) of samples were HHV-6 DNA-positive in either the supernate, pellet or both. In the patients, 58% (45/77) of all samples were HHV-6 DNA-positive. When sequential samples from twelve patients were examined the children appeared to fall into two groups: those who were frequently HHV-6 DNA-positive (60% of samples or more) and those who were rarely HHV-6 DNA-positive (33% of samples or less) (P < 0.0001). The only apparent difference between these two groups was that the less frequently HHV-6-positive group was more often febrile and unwell with neutropaenia. Hind III digestion demonstrated all the positive samples to be "B" type HHV-6. Possible explanations for this difference in HHV-6 secretion between the patient groups are discussed.

Identification of human herpesvirus 6 variants A and B by amplimer hybridization with variant-specific oligonucleotides and amplification with variant-specific primers

Two distinct PCR-based procedures were evaluated for the detection and identification of human herpesvirus 6 (HHV-6) variants A and B in uncultured human samples. Variant-specific oligonucleotide hybridization (VSOH) is based on the amplification of two distinct regions of the HHV-6 genome, followed by hybridization of amplimers with variant-specific oligonucleotide probes. Variant-specific primer PCR (VSPP) is based on the amplification of each variant by using variant-specific primers. The study of 10 well-characterized HHV-6 strains allowed us to demonstrate the high sensitivity and specificity of both methods. With variant mixtures, however, some limitations of VSOH were evidenced and VSPP was required to obtain unambiguous results. The combination of VSOH and VSPP was applied to the direct study of 300 peripheral blood mononuclear cell samples from French subjects. HHV-6 was detected in 15 samples: 11 corresponded to variant B, 3 corresponded to variant A, and 1 corresponded to a mixture of both variants.

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

In order to evaluate the prevalence of HHV-6 in blood donors, we examined 112 persons by polymerase chain reaction (PCR) and ELISA. HHV-6 antibodies could be detected in 107/111 (96.4%) of the donors. The median ELISA antibody level was 0.451 (range 0.056-0.914). 14 individuals (12.5%) were PCR positive in either oral lavage fluid, urine or buffy coat. Six persons (5.4%) were PCR positive in buffy coat samples. The prospective longitudinal analysis of 11 donors for periods between 7 and 13 weeks revealed that 4/6 persons who were initially PCR negative had positive tests in 9/63 weeks studied. Two persons were consistently PCR positive over the whole observation period of 12 and 13 weeks. HHV-6 variants could be determined in 14 persons as variant A in nine and variant B in five cases. These observations emphasize the high prevalence of HHV-6 and suggest that some blood donors carry detectable concentrations of the virus and therefore may be a source for transmission of HHV-6. The finding of positive PCR in antibody negative individuals suggests that antibody determination may not be sufficient to identify potentially infectious persons.

Prevalence of human herpesvirus 6 variants A and B in patients with chronic fatigue syndrome

Peripheral blood mononuclear cells collected from 13 patients with chronic fatigue syndrome and 13 healthy controls were analyzed for the presence of human herpesvirus 6 (HHV-6) DNA by variant-specific polymerase chain reaction and dot blot hybridization. HHV-6 DNA was detected in 7 of 13 (53%) patients, and of those 7 patients, 4 were positive for HHV-6 variant A DNA and 3 were for variant B. No HHV-6 DNA was detected in the controls. Serum antibody titers to the late antigen and antibody prevalence to the early antigen of HHV-6 were significantly higher in the patient group. These results suggest active replication of HHV-6 in patients with chronic fatigue syndrome.

Human herpesvirus 6 and human herpesvirus 7 infections in renal transplant recipients and healthy adults in Turkey

We explored the prevalence of human herpesvirus 6 (HHV-6) and human herpesvirus 7 (HHV-7) infections in 16 renal transplant recipients and 16 healthy controls by virus isolation, serology, polymerase chain reaction (PCR) followed by dot blot hybridization. HHV-6 variant A was isolated from one renal transplant recipient. Seven patients (44%) and six controls (38%) had HHV-6 variant B DNA in their peripheral blood mononuclear cells. The prevalence of HHV-7 DNA was found to be the same in patients and controls (19%).

Variation of DNA sequence in immediate-early gene of human herpesvirus 6 and variant identification by PCR

The complete nucleotide sequence of one of the immediate-early genes of human herpesvirus 6 variant B was determined and compared with that of variant A reported by Martin et al. (M.D. Martin, J. Nicholas, B. J. Thomson, C. Newman, and R. W. Honess, J. Virol. 65:5381-5390, 1991). While it was reported that two open reading frames exist in this region of variant A, only one open reading frame was found in variant B and the putative coding region of variant B was 2,679 nucleotides long. Furthermore, two additive regions of 108 and 228 bp were found in variant B. Primers covering one of these regions deleted in variant A were synthesized and used for PCR amplification. Twelve isolates from patients were clearly classified into variants A and B by PCR amplification with these primers. All isolates from patients with exanthem subitum were variant B.