Human herpesvirus-6 meningoencephalitis in a recipient of an unrelated allogeneic bone marrow transplantation

Late-phase human herpesvirus 6B reactivation in hematopoietic stem cell transplant recipients

BACKGROUND

We sought to determine whether late-phase human herpesvirus 6B (HHV-6B) infection in hematopoietic stem cell transplant (HSCT) recipients was associated with serious outcomes and mortality.

METHODS

The occurrence and course of HHV-6B infection was monitored for at least 60 days after transplant using virus isolation and real-time polymerase chain reaction. Risk factors for late-phase HHV-6B infection were examined, and the propensity score was calculated with significant risk factors. The inverse probability-weighted multivariable logistic regression analysis was performed to estimate odds ratios (ORs) and the 95% confidence intervals (95% CI) for mortality.

RESULTS

Late-phase HHV-6B infection was observed in 12/89 (13.5%) of the HSCT recipients. Older age (OR: 10.3, 95% CI: 2.1/72.9, P = .0027), hematologic malignancy (OR: 10.3, 95% CI: 1.8/97.1, P = .0063), unrelated donor transplantation (OR: 5.3, 95% CI: 1.1/36.0, P = .0345), and sex-mismatched donor transplantation (OR: 6.3, 95% CI: 1.4/39.5, P = .0149) were identified as risk factors for late-phase HHV-6B infection. Fifteen subjects died (17%). Inverse probability-weighted multivariable logistic model analysis revealed that late-phase HHV-6B infection was an independent risk factor for mortality (OR: 4.2, 95% CI: 1.7/11.0, P = .0012). Among 5 of the fatal cases of late-phase HHV-6B infection, viral infection might be associated with severe clinical manifestations.

CONCLUSION

Late-phase HHV-6B infection in HSCT recipients was associated with worse outcomes. The full spectrum of clinical features of the infection has not been fully elucidated, and therefore, recipients with high-risk factors for late-phase HHV-6B infection should be carefully monitored.

Valacyclovir versus Acyclovir for HSV Prophylaxis in Neutropenic Patients

BACKGROUND:

It is common practice to administer acyclovir as prophylaxis to patients with hematologic malignancies during neutropenia; however, effective therapy requires frequent dosing, which is difficult in this setting. Valacyclovir has greater oral bioavailability and requires less frequent dosing.

OBJECTIVE:

To evaluate the efficacy and safety of valacyclovir compared with acyclovir.

METHODS:

Patients who had been treated with chemotherapy or stem-cell transplantation were randomized to receive acyclovir 400 mg orally 3 × daily (n = 51), valacyclovir 500 mg orally twice daily (n = 48), or valacyclovir 250 mg orally twice daily (n = 52) during neutropenia.

RESULTS:

Clinical success, defined as the absence of an active herpes simplex virus (HSV) lesion or asymptomatic viral shedding, was similar between the 3 groups (acyclovir 96%, valacyclovir 500 mg 95%, valacyclovir 250 mg 100%). The overall rates of adverse events were similar in the 3 groups.

CONCLUSIONS:

Prophylactic treatment with valacyclovir is an effective and safe alternative to acyclovir for the prevention of HSV reactivation in patients with hematologic malignancies.

The development of new therapies for human herpesvirus 6

Human herpesvirus 6 (HHV-6) infections are typically mild and in rare cases can result in encephalitis. A common theme among all the herpesviruses, however, is the reactivation upon immune suppression. HHV-6 commonly reactivates in transplant recipients. No therapies are approved currently for the treatment of these infections, although small studies and individual case reports have reported intermittent success with drugs such as cidofovir, ganciclovir, and foscarnet. In addition to the current experimental therapies, many other compounds have been reported to inhibit HHV-6 in cell culture with varying degrees of efficacy. Recent advances in the development of new small molecule inhibitors of HHV-6 will be reviewed with regard to their efficacy and spectrum of antiviral activity. The potential for new therapies for HHV-6 infections will also be discussed, and they will likely arise from efforts to develop broad spectrum antiviral therapies for DNA viruses.

Central nervous system infections in cancer patients and hematopoietic stem cell transplant recipients

Central nervous system (CNS) infections in cancer patients present a diagnostic and therapeutic challenge for clinicians. While CNS infections are not frequent complications of cancer, its therapies, or hematopoietic stem cell transplantation, the importance of CNS infections lies in their propensity to result in profound morbidity and substantial mortality in this vulnerable patient population. With an expanding population of patients with malignant disease undergoing more potent and aggressive therapies and with the advent of newer immunomodulatory agents, the incidence of CNS infectious complications is likely to rise. This chapter will summarize the clinical and diagnostic evaluation of potential infections of the CNS in these patients and will discuss particular pathogens of interest with regard to this at-risk patient population.

Human herpesvirus 6 infections after liver transplantation

Human herpesvirus 6 (HHV-6) infections occur in > 95% of humans. Primary infection, which occurs in early childhood as an asymptomatic illness or manifested clinically as roseola infantum, leads to a state of subclinical viral persistence and latency. Reactivation of latent HHV-6 is common after liver transplantation, possibly induced and facilitated by allograft rejection and immunosuppressive therapy. Since the vast majority of humans harbor the virus in a latent state, HHV-6 infections after liver transplantation are believed to be mostly due to endogenous reactivation or superinfection (reactivation in the transplanted organ). In a minority of cases, however, primary HHV-6 infection may occur when an HHV-6 negative individual receives a liver allograft from an HHV-6 positive donor. The vast majority of documented HHV-6 infections after liver transplantation are asymptomatic. In a minority of cases, HHV-6 has been implicated as a cause of febrile illness with rash and myelosuppression, hepatitis, pneumonitis, and encephalitis after liver transplantation. In addition, HHV-6 has been associated with a variety of indirect effects such as allograft rejection, and increased predisposition and severity of other infections including cytomegalovirus (CMV), hepatitis C virus, and opportunistic fungi. Because of the uncommon nature of the clinical illnesses directly attributed to HHV-6, there is currently no recommended HHV-6-specific approach to prevention. However, ganciclovir and valganciclovir, which are primarily intended for the prevention of CMV disease, are also active against HHV-6 and may prevent its reactivation after transplantation. The treatment of established HHV-6 disease is usually with intravenous ganciclovir, cidofovir, or foscarnet, complemented by reduction in the degree of immunosuppression. This article reviews the current advances in the pathogenesis, clinical diagnosis, and therapeutic modalities against HHV6 in the setting of liver transplantation.

Role of dendritic cells infected with human herpesvirus 6 in virus transmission to CD4(+) T cells

Human herpesvirus 6 (HHV-6) is a ubiquitous betaherpesvirus that predominantly infects and replicates in CD4(+) T lymphocytes. However, the mechanism of HHV-6 transmission to T cells from the peripheral mucosa is unknown. Here we found that dendritic cells (DCs) can transmit HHV-6 to T cells, resulting in productive infection. In immature monocyte-derived DCs (MDDCs) infected with HHV-6, viral early and late antigens were expressed, and nucleocapsids containing a DNA core were observed, although few virions were detected in the cytoplasm by electron microscopy, indicating that the maturation of HHV-6 virions may be incomplete in MDDCs. However, HHV-6 transmission from MDDCs to stimulated CD4(+) T cells occurred efficiently in coculture of these cells, but not from MDDCs culture supernatants. This transmission was partially inhibited by treating the DCs with a viral DNA synthesis blocker, indicating that viral replication in MDDCs is required for this transmission. Furthermore, myeloid DCs and plasmacytoid DCs infected with HHV-6 could also transmit the virus to stimulated T cells. Thus, DCs may be the first cell population targeted by HHV-6 and could play an important role in the virus' transmission to T cells for their further propagation.

Human herpesvirus 6 and central nervous system disease in hematopoietic cell transplantation

Human herpesvirus 6 infects virtually all children within the first few years of life and like other herpesviruses, establishes latency after primary infection. In immunocompromised hosts, especially hematopoietic cell transplant (HCT) recipients, HHV-6 has been demonstrated to reactivate frequently. This reactivation has been associated with a number of different clinical endpoints in HCT recipients, including central nervous system (CNS) disease. There have been many detailed descriptions of individual patients with HHV-6-associated encephalitis. In addition, longitudinal observational studies have established a correlation between systemic HHV-6 reactivation and CNS dysfunction. Further research is needed to define optimal diagnostic, prevention, and treatment strategies.

Effectiveness of ganciclovir against human herpesvirus-6 excreted in saliva in stem cell transplant recipients

The aim of this study was to evaluate the effect of ganciclovir on human herpesvirus-6 (HHV)-6. Forty allogeneic stem cell transplant recipients were prospectively studied by repeated sampling of the saliva. The saliva samples were assayed for HHV-6 by quantitative polymerase chain reaction. HHV-6 was detected in 33 patients. Ganciclovir was given as preemptive therapy for cytomegalovirus infection during 15 episodes that were compared to 18 episodes without any concomitant antiviral therapy. The mean HHV-6 load decreased 0.49 (s.e. 0.31) log(10)/week in patients receiving ganciclovir whereas it increased 0.15 (s.e. 0.17) log(10)/week in episodes without antiviral therapy (P=0.04). We conclude that ganciclovir can decrease the HHV-6 viral load in saliva.

Human herpesvirus-6 infection in solid organ and stem cell transplant recipients

HHV-6 has in recent years become recognized as a potential significant pathogen in both solid organ and stem cell transplant recipients. HHV-6 infections are common after transplantation regardless of the utilized diagnostic technique. Several different clinical manifestations have been described including fever, bone marrow suppression, encephalitis, skin rash, and hepatitis. The most important end-organ disease is encephalitis in stem cell transplant recipients that has been reported to have a mortality of at least 40%. HHV-6 is also considered an immunomodulatory and immunosuppressive virus that may facilitate super-infections with other opportunistic pathogens such as CMV and fungal infections and thereby contribute to overall mortality. No established therapy exists but both ganciclovir and foscarnet have been reported to have in vitro and in vivo efficacy against HHV-6.

Fatal HHV-6 associated encephalitis in an HIV-1 infected patient treated with cidofovir

We describe the case of a patient infected with HIV and a concomitant HHV-6 encephalitis. The patient experienced virological failure following cidofovir treatment. RT-PCR was used both for early diagnosis and follow-up.

A reverse transcription-nested PCR assay for HHV-6 mRNA early transcript detection after transplantation

Monitoring of human herpesvirus-6 (HHV-6) reactivation is important, especially in immunocompromised patients such as transplant recipients. Reverse transcription PCR (RT-PCR) is a useful method to distinguish between latent and active infection. Here, a RT-nested PCR coupled with a colorimetric plate hybridization assay was established to detect HHV-6 types A and B U79/80 mRNAs. After confirming the reliability of the assay on HHV-6 cultures, it was applied to the detection of HHV-6 reactivation after renal (27 patients), bone marrow (14 patients) or heart (7 patients) transplantation. A total of 206 blood samples were tested from renal (137), bone marrow (58) and heart (11) transplant recipients. U79/80 mRNAs were found in 32 samples that were considered as indicative of HHV-6 reactivation: 15, 13 and 5 from kidney, bone marrow and heart transplant recipients, respectively. Finally, U79/80 mRNA detection was correlated with clinical manifestations including leucopenia, skin rash, graft rejection or dysfunction and diarrhoea.

Clinical Outcomes of Human Herpesvirus 6 Reactivation after Hematopoietic Stem Cell Transplantation

BACKGROUND

Although human herpesvirus 6 (HHV-6) is known to reactivate during hematopoietic stem cell transplantation (HSCT), the clinical significance of this finding is controversial.

METHODS

We used a quantitative PCR test for HHV-6 to assay plasma samples prospectively collected from a cohort of 110 allogeneic HSCT recipients to evaluate the clinical effects of HHV-6 infection. A retrospective review of medical records was performed to determine clinical end points.

RESULTS

HHV-6 reactivation occurred in 52 (47%) of the 110 subjects. Factors that increased the risk of subsequent HHV-6 reactivation were hematologic malignancy that occurred at a time other than the first remission (adjusted P = .002), a mismatch in the sexes of donor and recipient (adjusted P=.05), younger age (adjusted P = .01), and the receipt of glucocorticoids (adjusted P = .06). HHV-6 reactivation was associated with subsequent all-cause mortality (adjusted hazard ration [HR], 2.9; 95% confidence interval [CI], 1.1-7.5), grade 3-4 graft-versus-host disease (GVHD) (adjusted HR, 4.9; 95% CI, 1.5-16), a lower probability of monocyte engraftment (adjusted HR, 0.42; 95% CI; 0.22-0.80), a lower probability of platelet engraftment (adjusted HR, 0.47; 95% CI, 0.21-1.1; P = .05) and a higher platelet transfusion requirement (adjusted P = .02). A higher level of HHV-6 DNA was associated with subsequent central nervous system (CNS) dysfunction (HR, 21; 95% CI, 1.8-249).

CONCLUSIONS

HHV-6 reactivation is common after allogeneic HSCT and is associated with subsequent delayed monocyte and platelet engraftment, increased platelet transfusion requirements, all-cause mortality, grade 3-4 GVHD, and CNS dysfunction.

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).

Use of amplicon-6 vectors derived from human herpesvirus 6 for efficient expression of membrane-associated and -secreted proteins in T cells

The composite amplicon-6 vectors, which are derived from human herpesvirus 6 (HHV-6), can target hematopoietic cells. In the presence of the respective helper viruses, the amplicons are replicated by the rolling circle mechanism, yielding defective genomes of overall size 135 to 150 kb, composed of multiple repeats of units, containing the viral DNA replication origin, packaging signals, and the selected transgene(s). We report the use of amplicon-6 vectors designed for transgene expression in T cells. The selected transgenes included the green fluorescent protein marker, the herpes simplex virus type 1 glycoprotein D (gD), and the gD gene deleted in the transmembrane region (gDsec). The vectors were tested after electroporation and passage in T cells with or without helper HHV-6A superinfections. The results were as follows. (i)The vectors could be passaged both as cell-associated and as cell-free secreted virions infectious to new cells. (ii)The intact gD accumulated at the cell surface, whereas the gDsec was dispersed at internal locations of the cells or was secreted into the medium. (iii)Analyses of amplicon-6-gD expression by flow cytometry have shown significant expression in cultures with reiterated amplicons and helper viruses. The vector has spread to >60% of the cells, and the efficiency of expression per cell increased 15-fold, most likely due to the presence of concatemeric amplicon repeats. Current studies are designed to test whether amplicon-6 vectors can be used for gene therapy in lymphocytes and whether amplicon-6 vectors expressed in T cells and dendritic cells can induce strong cellular and humoral immune responses.

Neurologic complications of bone marrow transplantation

The various forms of HSCT are or will soon be accepted treatments for an ever-increasing number of hematologic and solid cancers. Attempts to reduce the mortality and morbidity of HSCT and at the same time preserve or increase its efficacy in tumor control include development of nonmyeloablative allogeneic stem-cell transplant strategies [208] and allogeneic laboratory research-enhancing graft acceptance [209,210]. Eventually, these efforts will reduce complication rates of HSCT, including neurologic complications. In the interim, the consultant neuro-oncologist or neurologist with a specific inteest in this field is faced with complex clinical syndromes, neuroradiologic imaging studies and neurophysiologic tests, and generally poorly understood pathophysiologic mechanisms. Prospective studies of HSCT patients in large transplantation centers using clinical registries are needed.

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.

Human herpesvirus 6 meningoencephalitis successfully treated with ganciclovir in a patient who underwent allogeneic bone marrow transplantation from an HLA-identical sibling

Human herpesvirus 6 (HHV-6) has recently been recognized as an important pathogen in immunocompromised hosts, such as patients who have undergone allogeneic bone marrow transplantation (allo-BMT). Here we report a case of HHV-6 meningoencephalitis in a patient who underwent allo-BMT from an HLA-identical sibling. The patient suffered from headache, high fever, tremor, and disorientation on day 35 after allo-BMT. Findings at magnetic resonance imaging, electroencephalography, and routine cerebrospinal fluid (CSF) examination suggested the presence of viral meningoencephalitis. We diagnosed HHV-6 meningoencephalitis by means of polymerase chain reaction (PCR) analysis of a CSF specimen. Successful treatment was achieved with ganciclovir. Because HHV-6 encephalitis has a potentially fatal and fulminant course, it is necessary that HHV-6 encephalitis be recognized as one of the central nervous system complications that can follow allo-BMT. PCR analysis for HHV-6 in the CSF specimen is necessary for appropriate diagnosis and treatment.

Antiviral prophylaxis may prevent human herpesvirus-6 reactivation in bone marrow transplant recipients

Human herpesvirus-6 (HHV-6) infects the majority of children under the age of 2 years causing roseola infantum. Following short self-limited disease, the virus enters into a latency phase in peripheral blood lymphocytes (PBL). It has been previously reported that HHV-6 reactivation from latency, in immunocompromised patients undergoing bone marrow transplantation (BMT), could result in febrile illness, pneumonitis, meningitis, and/or encephalitis. In our study, 14 BMT patients received two different antiviral prophylactic therapies: 8 patients received acyclovir, whereas 6 patients received ganciclovir. Clinical manifestations and virus recovery were monitored pre- and post-BMT by polymerase chain reaction tests of cord blood cells cultured with the patients' PBL. No HHV-6 recovery was shown in the 6 patients treated with ganciclovir, whereas 3 of the 8 acyclovir-treated patients experienced virus reactivation 20-21 days post-BMT. One of the 3 patients was asymptomatic but had late engraftment; the second patient had prolonged fever, skin rash, and hemorrhage; the third patient experienced prolonged fever, pneumonitis, marrow rejection, and fatal encephalitis. It is concluded that viral reactivation may be prevented by prophylactic treatment with ganciclovir. Our observation awaits further documentation in prospective randomized trials in high-risk BMT recipients.

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.

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.

Human herpesvirus 6 and cytomegalovirus infections in children with human immunodeficiency virus infection and cancer

AIM

Measure the prevalence of human herpesvirus 6 (HHV-6) and cytomegalovirus (CMV) infections in children and adolescents with HIV infection and malignancy.

METHODS

Semiquantitative polymerase chain reaction and serology were used to test for HHV-6 and CMV infections in 31 cases (HIV-infected children with cancer), 56 HIV controls (HIV-infected children without cancer) and 30 cancer controls (HIV-uninfected children with cancer).

RESULTS

In cases, HIV controls and cancer controls, HHV-6 DNA was detected in 29, 39 and 34%, respectively, and CMV DNA was detected in 13, 4 and 7%, respectively. Four cases (13%) and no HIV controls or cancer controls harbored HHV-6 subtype A (P = 0.014). In cases, HIV controls and cancer controls, the prevalence of HHV-6 antibodies was 58, 68 and 93%, respectively, and the prevalence of CMV antibodies was 71, 48 and 70%, respectively. HHV-6 seroprevalence was lower in cases than in cancer controls (P = 0.002), even with adjustments for age and CD4 concentrations; however, HHV-6 infection rates (presence of HHV-6 DNA and/or HHV-6 antibodies) were similar in all groups. Stratification showed that CMV infection was more common in younger patients (ages < 8 years) without severe immune suppression (CD4 concentration >200 cells/microl) than in HIV controls (odds ration, 10.343; 95% confidence interval, 1.65, 121.57). Geometric mean titers of serum anti-CMV antibodies, but not anti-HHV-6 antibodies, were higher in cases (1:71) than in HIV controls (1:33) (P = 0.005).

CONCLUSIONS

HHV-6 and CMV infections were common among children with HIV infection and cancer. CMV seropositivity also was associated with cancer in younger HIV-infected patients who did not have severe immune suppression. HHV-6A was detected only in HIV-infected children with cancer.

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.

Selection of the same mutation in the U69 protein kinase gene of human herpesvirus-6 after prolonged exposure to ganciclovir in vitro and in vivo

After serial passage in the presence of increasing concentrations of ganciclovir (GCV) in vitro, a human herpesvirus-6 (HHV-6) mutant exhibiting a decreased sensitivity to the drug was isolated. Analysis of drug susceptibility showed that the IC(50) of this mutant was 24-, 52- and 3-fold higher than that of the wild-type (wt) IC(50) in the case of GCV, cidofovir and foscarnet, respectively. Genotypic analysis showed two single nucleotide changes as compared to the wild-type: an A-->G substitution of the U69 protein kinase (PK) gene resulted in an M(318)V amino acid substitution and the other change, located in the C-terminal part of the U38 gene, resulted in an A(961)V amino acid substitution within the DNA polymerase. The M(318)V change was located within the consensus sequence DISPMN of the putative catalytic domain VI of the PK. This change was homologous to the M(460)V and M(460)I changes that had been reported previously within the consensus sequence DITPMN of the human cytomegalovirus (HCMV) UL97 PK and associated with the resistance of HCMV to GCV. The M(318)V change was also detected by PCR in HHV-6-infected PBMCs from an AIDS patient who had been treated with GCV for a long period of time and exhibited a clinically GCV-resistant HCMV infection. These findings provide strong circumstantial evidence that the M(318)V change of the PK gene is associated with resistance to GCV and raise the question of cross resistance to this drug among different betaherpesviruses.

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.

Primary human herpesvirus 6 infection in liver transplant recipients

We detected primary human herpesvirus 6 (HHV-6) infection in 5 infants who received living related liver transplantation from their HHV-6 seropositive mothers. Primary HHV-6 infection was confirmed by demonstrating the seroconversion of HHV-6 antibodies with an immunofluorescence assay, by the isolation of the virus, or both. Seroconversion of HHV-6 immunoglobulin G antibody was demonstrated in all 5 recipients. HHV-6 was isolated from 3 of the 5 recipients between 2 and 3 weeks after transplantation. Moreover, the virus genome was detected in plasma by polymerase chain reaction in 4 of the 5 recipients during the same period. Although the 5 recipients had pyrexia at the time of primary HHV-6 infection, none of the recipients had a skin rash after defervescence. Clinical symptoms disappeared without specific antiviral treatment in all but 1 of the recipients.

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.

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.

Infections of the central nervous system in transplant recipients

Central nervous system (CNS) infections, accounting for 4-29% of CNS lesions in transplant recipients, are a significant post-transplant complication. Focal CNS infectious lesions or brain abscesses have been documented in 0.36-1% of the transplant recipients. Mycelial fungi, particularly Aspergillus, are by far the most frequent etiologies of post-transplant brain abscesses. Bacteria, with the exception of Nocardia, are rarely associated with brain abscesses in transplant recipients. Time of onset and concurrent extraneural lesions have implications relevant towards invasive diagnostic procedures in transplant recipients with brain abscesses. Meningoencephalitis in transplant recipients is predominantly due to viruses, e.g., herpesviruses, and less frequently due to Listeria monocytogenes, Toxoplasma gondii, and Cryptococcus. Despite a wide, and at times perplexing array of opportunistic pathogens that can cause CNS infections, the temporal association of the infection with the time elapsed since transplantation, risk factors, clinical manifestations, and neuroimaging characteristics of the lesion can allow a reasoned and rational approach towards the recognition, diagnosis, and appropriate management of CNS infections in transplant recipients.

Encephalitis caused by human herpesvirus-6 in transplant recipients: relevance of a novel neurotropic virus

BACKGROUND

Human herpesvirus-6 (HHV-6) is a neurotropic virus. Encephalitis is a significant clinical manifestation of HHV-6; however, sparse data on this entity exist in transplant recipients.

METHODS

Cases of HHV-6 encephalitis reported in the literature (13 bone marrow transplant recipients and 1 liver transplant recipient) were reviewed. The diagnosis was established in all by viral isolation and/or detection of HHV-6 DNA in the cerebrospinal fluid by polymerase chain reaction or histopathologic method.

RESULTS

HHV-6 encephalitis occurred a median of 45 days (range 10 days to 15 months) after transplantation. Mental status changes, ranging from confusion to coma (92%), seizures (25%), and headache (25%) were the predominant clinical presentations. Focal neurologic findings occurred in only 17% of the patients. Twenty-five percent of the patients had fever; however, the height of fever (< or =40 degrees C) in febrile patients was striking. Cerebrospinal fluid pleocytosis was generally lacking. Abnormal neuroimaging findings, characterized by low-attenuation lesions in the posterior cerebral lobes, were present only in 17% of the patients. Overall mortality in patients with HHV-6 encephalitis was 58% (7 of 12); 42% (5 of 12) of the deaths were caused by HHV-6. Cure was documented in 7 of 8 patients who received ganciclovir or foscarnet for > or =7 days, compared with 0% (0 of 4) in those who did not receive these drugs or received them for < 7 days (P=.01).

CONCLUSIONS

HHV-6 may be associated with encephalitis after transplantation and warrants consideration in transplant recipients with encephalitis of unidentifiable etiology.

The spectrum of human herpesvirus 6 infection: from roseola infantum to adult disease

Human herpesvirus 6 is the causative agent of roseola infantum, a generally benign rash illness of infants. Most persons acquire HHV-6 infection by age 2 years, and HHV-6 infection is a common cause of fever and febrile seizures in infants. In adults, primary infection with HHV-6 can produce a mononucleosis-like illness and, more rarely, severe disease, including encephalitis. In addition to primary infections, HHV-6 can cause clinical illness during reactivation, particularly in immunocompromised persons.

Susceptibility of human herpesvirus 6 to antiviral compounds by flow cytometry analysis

BACKGROUND

The emergence of human herpesvirus 6 (HHV-6) as a human pathogen led to the possibility of specific therapy against HHV-6 and the development of standardized susceptibility assays of HHV-6 to antivirals.

METHODS

We have developed a flow cytometry method to analyze the multiplication of the HST strain of human herpesvirus 6 (HHV-6) variant B in vitro using monoclonal antibodies specific to virus proteins. This method was subsequently used to determine the sensitivity of HST multiplication in MT4 cells to four antiviral compounds of three different classes: acyclovir (ACV) and ganciclovir (GCV), two acyclic guanosine analogs; cedofovir (CDV), an acyclic nucleoside phosphonate; and phosphonoformic acid (PFA), a pyrophosphate analog.

RESULTS

The 50% inhibitory concentrations (IC(50)) of ACV, GCV, CDV, and PFA determined by flow cytometry assay were 25.3, 6.4, 0.95, and 6.0 microM, respectively (5.7, 1.6, 0.3, and 1.8 microg/ml, respectively). These data together with the results of cytotoxicity assays confirmed the high efficiency and selectivity of CDV and PFA against HHV-6 B in vitro, suggested by previous results.

CONCLUSIONS

Our flow cytometric assay appeared as a reproducible specific method to characterize HHV-6 susceptibility to antiviral compounds. It can be considered as a convenient alternative to the other immunologic and DNA hybridization assays used for that purpose.

Human herpes virus 6 fatal encephalitis in a bone marrow recipient

Human herpes virus 6 (HHV-6) has been implicated as a human pathogen in both normal and immunocompromised hosts. It has been associated with interstitial pneumonitis and bone marrow suppression after transplantation. We report here a case of fatal encephalitis in a bone marrow transplant recipient. This case illustrates the importance of considering HHV6 as an emerging pathogen in immunocompromised hosts.

Encephalopathy associated with human herpesvirus 6 in a liver transplant recipient

Recent reports have documented human herpesvirus 6 (HHV-6) as a cause of high fever, bone marrow depression, and rash in liver transplant recipients in the absence of another known pathogen. We describe a 49-year-old liver transplant recipient who developed confusion, occipital headache, and involuntary movements of the limbs 3 weeks after orthotopic liver transplantation. HHV-6 was detected in the peripheral blood using a rapid culture assay. Examination of cerebrospinal fluid by polymerase chain reaction for HHV-6 was also positive. No other pathogens were identified. The patient improved after commencement of intravenous ganciclovir therapy. This case suggests HHV-6 needs to be considered in the differential diagnosis of unexplained confusion in liver transplant recipients.

HHV-6-related secondary graft failure following allogeneic bone marrow transplantation

We report the case of an 11-year-old boy who underwent allogeneic bone marrow transplantation (BMT) for relapsed acute lymphoblastic leukaemia. Despite adequate engraftment, on day 45 he developed marrow aplasia with haemophagocytosis. HHV-6 was detected in blood and bone marrow by nested PCR. Retrospective testing showed that viraemia had started on day 24. Following therapy with foscarnet and ganciclovir, viral load declined to undetectable levels and his donor marrow recovered contemporaneously. This case suggests that HHV-6 may be a treatable cause of graft failure following BMT and provides clinical and virological evidence for the anti-HHV-6 activity of ganciclovir and foscarnet.

Concepts of viral pathogenesis of multiple sclerosis

Viral infections have long been suspected to cause or modulate the pathogenesis of multiple sclerosis. Recently, two viruses in particular have been associated with multiple sclerosis: human herpesvirus-6 and a retrovirus termed multiple sclerosis-associated retrovirus, which is a member of the human endogenous retrovirus-9 family. Reports on the detection of human herpesvirus-6-encoded proteins in and around multiple sclerosis lesions are intriguing. Serological and polymerase chain reaction analyses looking for signs of reactivation of human herpesvirus-6 in multiple sclerosis patients are ambiguous, however. If human herpesvirus-6 does play a role as an initiator or amplifier of inflammatory lesions in some multiple sclerosis patients, these individuals might benefit from antiviral therapy.

Herpesviruses--a rationale for antiviral treatment in multiple sclerosis

In multiple sclerosis (MS), the extensive and long lasting search for viruses or other pathogens has hitherto failed to identify a common etiological agent. However, the beneficial effects by interferon-beta treatment in MS, although suggested to depend mainly on immunomodulation, might lend support to a viral involvement in the pathogenesis. The human herpesviruses have attracted interest since their recurrent modes of infection share some similarity with the relapsing-remitting course of MS, most members are readily detected within the brain, and several of these viruses may induce demyelination within the central nervous system in human hosts as well as in animal models. Accumulated diagnostic and epidemiological data are compatible with a role for the herpesviruses as possible cofactors rather than etiological agents, and recent studies showing early neuronal damage in MS patients focus attention on the neurotropic alpha-herpesviruses. Antiviral treatment trials with safe and effective drugs such as valaciclovir offer a possibility of testing the hypotheses concerning herpesviral involvement in MS.