Clinical Significance of Pretransplant Chromosomally Integrated Human Herpesvirus-6 in Liver Transplant Recipients

Reactivation of a Transplant Recipient's Inherited Human Herpesvirus 6 and Implications to the Graft

BACKGROUND

The implications of inherited chromosomally integrated human herpesvirus 6 (iciHHV-6) in solid organ transplantation remain uncertain. Although this trait has been linked to unfavorable clinical outcomes, an association between viral reactivation and complications has only been conclusively established in a few cases.

METHODS

We used hybrid capture sequencing for in-depth analysis of the viral sequences reconstructed from sequential liver biopsies. Moreover, we investigated viral replication through in situ hybridization (U38-U94 genes), reverse transcriptase polymerase chain reaction (U89/U90 genes), immunohistochemistry, and immunofluorescence. We also performed whole transcriptome sequencing to profile the host immune response.

RESULTS

We report a case of reactivation of a recipient's iciHHV-6B and subsequent infection of the graft. Using a novel approach integrating the analysis of viral and mitochondrial DNAs, we located the iciHHV-6B intragraft. We demonstrated active replication via the emergence of viral minor variants, in addition to positive viral messenger RNAs and antigen stainings in tissue sections. Furthermore, we detected significant upregulation of antiviral immune responses, arguing against immunotolerance.

CONCLUSIONS

Our analysis underscores the potential pathological impact of iciHHV-6B, emphasizing the need for monitoring reactivation in transplant recipients. Most crucially, it highlights the critical role that the host's virome can play in shaping the outcome of transplantation.

Recurrent herpes simplex virus encephalitis with presumptive Human Herpesvirus 6 chromosomal integration

Viral encephalitis can lead to encephalopathy, epileptic activity, focal neurological deficits, and death. Prompt recognition and a high index of clinical suspicion can lead to early initiation of appropriate management. We describe an interesting case of a 61-year-old presenting with fever and altered mental status, diagnosed with numerous episodes of viral encephalitis caused by divergent and recurrent viruses. On his initial presentation, lumbar puncture revealed lymphocytic pleocytosis and positivity for Human Herpesvirus 6 (HHV-6), and he was treated with ganciclovir. On subsequent admissions, he was diagnosed with recurrent HHV-6 encephalitis as well as Herpes Simplex Virus 1 encephalitis and treated with ganciclovir, foscarnet and acyclovir. Despite prolonged courses of treatment and resolution of symptoms, he continued to have persistently high plasma viral loads of HHV-6, consistent with probable chromosomal integration. In this report, we emphasize the clinical pearl of chromosomally integrated HHV-6 that can present in a patient with persistently high plasma viral loads of HHV-6, that are non-responsive to treatment. Individuals with chromosomally integrated HHV-6 may be more susceptible to other viral infections.

Prevalence of human herpesviruses in biliary fluid and their association with biliary complications after liver transplantation

BACKGROUND

Beta-herpesviruses are common opportunistic pathogens that cause morbidity after liver transplantation (LT).

METHODS

Objective of the study was to evaluate the prevalence and correlation of herpesviruses in bile, blood and liver tissue and to investigate their association with biliary complications and retransplantation (re-LT) free survival after LT. The study design is a single-center case-control study. We performed quantative polymerase chain reaction (qPCR) for herpesvirus 1-8 DNA in bile, blood and liver tissue of 73 patients after first LT and analyzed their clinical courses retrospectively.

RESULTS

The median follow-up was 48 months (range 2-102), during which a total of 16 patients underwent re-LT and 11 patients died. Of the patients, 46.5% received valganciclovir prophylaxis at the time of bile sample acquisition. Cytomegalovirus (CMV) (18.3%), human herpesvirus 6 (HHV-6) (34.2%), human herpesvirus 7 (HHV-7) (20.5%) and Epstein-Barr virus (EBV) (16.4%) were highly prevalent in bile after LT, while herpes simpex virus 1 and 2 (HSV-1, HSV-2), varicella-zoster virus (VZV) and human herpesvirus 8 (HHV-8) were not or rarely detected in bile. Valganciclovir prophylaxis did not reduce the prevalence of HHV-6 and HHV-7 in bile, but it did reduce the presence of CMV and EBV. The presence of HHV-6 in bile was associated with non-anastomotic biliary strictures (NAS) and acute cellular rejection (ACR).

CONCLUSIONS

CMV, EBV, HHV-6 and HHV-7 are more prevalent in biliary fluid than in liver biopsy or blood serum after LT. HHV-6 and HHV-7 might be associated with biliary complications after LT. Biliary fluids might be an attractive target for routine herpesvirus detection.

Human herpesvirus 6, 7, and 8 in solid organ transplantation: Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These updated guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation review the diagnosis, prevention, and management of HHV-6A, HHV-6B, HHV-7, and HHV-8 in the pre- and post-transplant period. The majority of HHV-6 (A and B) and HHV-7 infections in transplant recipients are asymptomatic; symptomatic disease is reported infrequently across organs. Routine screening for HHV-6 and 7 DNAemia is not recommended in asymptomatic patients, nor is prophylaxis or preemptive therapy. Detection of viral nucleic acid by quantitative PCR in blood or CSF is the preferred method for diagnosis of HHV-6 and HHV-7 infection. The possibility of chromosomally integrated HHV-6 DNA should be considered in individuals with persistently high viral loads. Antiviral therapy should be initiated for HHV-6 encephalitis and should be considered for other manifestations of disease. HHV-8 causes Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman disease and is also associated with hemophagocytic syndrome and bone marrow failure. HHV-8 screening and monitoring may be indicated to prevent disease. Treatment of HHV-8 related disease centers on reduction of immunosuppression and conversion to sirolimus, while chemotherapy may be needed for unresponsive disease. The role of antiviral therapy for HHV-8 infection has not yet been defined.

Human Herpesvirus 6B in the Transplant Recipient: When to Worry, When to Act

Human herpesvirus 6B (HHV-6B) is a ubiquitous pathogen that infects most individuals before the age of three years. HHV-6B reactivates in approximately 40% of transplant recipients where it has been associated with a number of important outcomes, especially in allogeneic transplant recipients. This article will review the epidemiology, clinical manifestations, diagnosis, and treatment of HHV-6B infection.

High human herpesvirus 6 viral load in pediatric allogeneic hematopoietic stem cell transplant patients is associated with detection in end organs and high mortality

Human Herpes Virus 6 (HHV-6) reactivation occurs in approximately half of patients following allogeneic hematopoietic stem cell transplant (HSCT). While encephalitis and delayed engraftment are well-documented complications of HHV-6 following HSCT, the extent to which HHV-6 viremia causes disease in children is controversial. We performed a retrospective review of HHV-6 reactivation and possible manifestations in pediatric allogeneic HSCT patients at a single institution. Of 89 children and young adults who underwent allogeneic HSCT over a three-and-a-half-year period, 34 patients reactivated HHV-6 early post-transplant. Unrelated donor stem cell source and lack of antiviral prophylaxis were risk factors for the development of HHV-6 viremia. Viremia correlated with the presence of acute graft-versus-host disease, but not chronic graft-versus-host disease. We identified two subgroups within the viremic patients-a high-risk viremic and tissue-positive group that reactivated HHV-6 and had suspected end-organ disease and a low-risk viremic but asymptomatic group that reactivated HHV-6 but did not exhibit symptoms or signs of end-organ disease. Peak viral load was found to be strongly associated with mortality. Prospective studies in larger numbers of patients are needed to further investigate the role of HHV-6 in causing symptomatic end-organ disease as well as the association of viral load with mortality.

HHV-6 in liver transplantation: A literature review

Human herpesvirus 6 (HHV-6A and HHV-6B) can cause primary infection or reactivate from latency in liver transplant recipients, which can result in a variety of clinical syndromes, including fever, hepatitis, encephalitis and higher rates of graft dysfunction as well as indirect effects including increased risks of mortality, CMV disease, hepatitis C progression and greater fibrosis scores. Although HHV-6 infection is currently diagnosed by quantifying viral DNA in plasma or blood, biopsy to demonstrate histopathological effects of HHV-6 remains the gold standard for diagnosis of end-organ disease. HHV-6 reactivation may be restricted to the infected organ with no evidence of active infection in the blood. HHV-6 infections in liver transplant patients are mostly asymptomatic, but clinically significant tissue-invasive infections have been treated successfully with ganciclovir, foscarnet or cidofovir. Inherited chromosomally integrated HHV-6 (ciHHV-6), in either the recipient or the donor organ, may create confusion about systemic HHV-6 infection. Recipients with inherited ciHHV-6 may have an increased risk of opportunistic infection and graft rejection. This article reviews the current scientific data on the clinical effects, risk factors, pathogenesis, diagnosis and treatment of HHV-6 infections in liver transplant recipients.

Chemokines encoded by herpesviruses

Viruses use diverse strategies to elude the immune system, including copying and repurposing host cytokine and cytokine receptor genes. For herpesviruses, the chemokine system of chemotactic cytokines and receptors is a common source of copied genes. Here, we review the current state of knowledge about herpesvirus-encoded chemokines and discuss their possible roles in viral pathogenesis, as well as their clinical potential as novel anti-inflammatory agents or targets for new antiviral strategies.

Outcomes of hematopoietic cell transplantation using donors or recipients with inherited chromosomally integrated HHV-6

Human herpesvirus 6 (HHV-6) species have a unique ability to integrate into chromosomal telomeres. Mendelian inheritance via gametocyte integration results in HHV-6 in every nucleated cell. The epidemiology and clinical effect of inherited chromosomally integrated HHV-6 (iciHHV-6) in hematopoietic cell transplant (HCT) recipients is unclear. We identified 4319 HCT donor-recipient pairs (8638 subjects) who received an allogeneic HCT and had archived pre-HCT peripheral blood mononuclear cell samples. We screened these samples for iciHHV-6 and compared characteristics of HCT recipients and donors with iciHHV-6 with those of recipients and donors without iciHHV-6, respectively. We calculated Kaplan-Meier probability estimates and Cox proportional hazards models for post-HCT outcomes based on recipient and donor iciHHV-6 status. We identified 60 HCT recipients (1.4%) and 40 donors (0.9%) with iciHHV-6; both recipient and donor harbored iciHHV-6 in 13 HCTs. Thus, there were 87 HCTs (2%) in which the recipient, donor, or both harbored iciHHV-6. Acute graft-versus-host disease (GVHD) grades 2-4 was more frequent when recipients or donors had iciHHV-6 (adjusted hazard ratios, 1.7-1.9; P = .004-.001). Cytomegalovirus viremia (any and high-level) was more frequent among recipients with iciHHV-6 (adjusted HRs, 1.7-3.1; P = .001-.040). Inherited ciHHV-6 status did not significantly affect risk for chronic GVHD, hematopoietic cell engraftment, overall mortality, or nonrelapse mortality. Screening for iciHHV-6 could guide donor selection and post-HCT risk stratification and treatment. Further study is needed to replicate these findings and identify potential mechanisms.

Roseolovirus-associated encephalitis in immunocompetent and immunocompromised individuals

The roseoloviruses, human herpesvirus (HHV)-6A, HHV-6B, and HHV-7, can cause severe encephalitis or encephalopathy. In immunocompetent children, primary HHV-6B infection is occasionally accompanied by diverse clinical forms of encephalitis. Roseolovirus coinfections with heterologous viruses and delayed primary HHV-7 infection in immunocompetent adults result in very severe neurological and generalized symptoms. Recovery from neurological sequelae is slow and sometimes incomplete. In immunocompromised patients with underlying hematological malignancies and transplantation, frequent single or simultaneous reactivation of roseoloviruses elicit severe, lethal organ dysfunctions, including damages in the limbic system, brain stem, and hippocampus. Most cases have been due to HHV-6B with HHV-6A accounting for 2-3%. The most severe manifestation of HHV-6B reactivation is post-transplantation limbic encephalitis. Seizures, cognitive problems, and abnormal EEG are common. Major risk factors for HHV-6B-associated encephalitis include unrelated cord blood cell transplantation and repeated hematopoietic stem cell transplantation. Rare genetic disorders, male gender, certain HLA constellation, and immune tolerance to replicating HHV-6 in persons carrying chromosomally integrated HHV-6 might also predispose an individual to roseolovirus-associated brain damage. At this time, little is known about the risk factors for HHV-7-associated encephalitis. Intrathecal glial cell destruction due to virus replication, overexpression of proinflammatory cytokines, and viral mimicry of chemokines all contribute to brain dysfunction. High virus load in the cerebrospinal fluid, hippocampal astrogliosis, and viral protein expression in HHV-6B-associated cases and multiple microscopic neuronal degeneration in HHV-7-associated cases are typical laboratory findings. Early empirical therapy with ganciclovir or foscarnet might save the life of a patient with roseolovirus-associated encephalitis.

Treatment of alpha and beta herpesvirus infections in solid organ transplant recipients

INTRODUCTION

Human herpesviruses frequently cause infections in solid organ transplant (SOT) recipients. Areas covered: We provide an overview of the clinical impact of alpha and beta herpesviruses and highlight the mechanisms of action, pharmacokinetics, clinical indications, and adverse effects of antiviral drugs for the management of herpes simplex virus, varicella zoster virus and cytomegalovirus. We comprehensively evaluated key clinical trials that led to drug approval, and served as the foundation for management guidelines. We further provide an update on investigational antiviral agents for alpha and beta herpesvirus infections after SOT. Expert commentary: The therapeutic armamentarium for herpes infections is limited by the emergence of drug resistance. There have been major efforts for discovery of new drugs against these viruses, but the results of early-phase clinical trials have been less than encouraging. We believe, however, that more antiviral drug options are needed given the adverse side effects associated with current antiviral agents, and the emergence of drug-resistant virus populations in SOT recipients. Likewise, optimized use and strategies are needed for existing and novel antiviral drugs against alpha and beta-herpesviruses in SOT recipients.

Efficient identification of inherited chromosomally integrated human herpesvirus 6 using specimen pooling

BACKGROUND

Human herpesvirus 6 (HHV-6) has a unique ability to integrate into chromosomal telomeres. Vertical transmission via germ cell integration results in offspring with inherited chromosomally integrated (ci)HHV-6 in all nucleated cells, affecting ∼1% of the population.

OBJECTIVES

Inherited ciHHV-6 may be a direct or indirect mediator of human disease, but efficient identification of affected individuals is a fundamental roadblock to larger studies exploring the clinical importance of this condition.

STUDY DESIGN

A group testing strategy was designed to efficiently identify individuals with inherited ciHHV-6. DNA was extracted from 2496 cellular samples from hematopoietic cell transplant (HCT) donor-recipient pairs. Pools of 12 samples were screened for HHV-6 DNA with quantitative (q)PCR. Individual samples from high positive pools were tested with qPCR, and high positive individual samples were tested for inherited ciHHV-6 using droplet digital (dd)PCR to determine HHV-6 DNA copies/cellular genome.

RESULTS

Thirty-one pools had high positive HHV-6 DNA detection with >10(3) HHV-6 DNA copies/μg. Each pool had one sample with >10(4) copies/μg HHV-6 DNA. Inherited ciHHV-6 was confirmed by ddPCR in every high positive sample (>10(3) HHV-6 DNA copies/μg), yielding a prevalence of 1.5% in HCT recipients and 0.96% in donors. We performed 580 qPCR tests to screen 2496 samples for inherited ciHHV-6, a 77% reduction in testing.

CONCLUSIONS

Inherited ciHHV-6 can be efficiently identified by specimen pooling coupled with modern molecular techniques. This algorithm can be used to facilitate cost-effective identification of patients with inherited ciHHV-6, thereby removing a major hurdle for large-scale study of its clinical impact.

Interplay between β herpesviruses and fungal infections in transplant patients: from the bench to the bedside

ABSTRACT 

The studies on the interplay between β-herpesviruses (CMV, human herpes viruses 6 and 7) and fungi in immunocompromised hosts, have demonstrated that a detailed knowledge of the interaction between the host and the above infectious agents may have a significant clinical relevance. β-herpesviruses may directly be associated to different pathological conditions and may indirectly be involved in the development of opportunistic infections (e.g., fungal infections), allograft rejection and decreased patient survival. Recent in vitro and in vivo studies have pointed out the importance of the microbiome, exposure to microbes and the innate immune system in determining the risk of developing infections; such microbial interactions may modulate the expression of the infection, change the microbial pathogenicity, or increase the immunosuppression.

Analyses of germline, chromosomally integrated human herpesvirus 6A and B genomes indicate emergent infection and new inflammatory mediators

Human herpesvirus-6A (HHV-6A) is rarer than HHV-6B in many infant populations. However, they are similarly prevalent as germline, chromosomally integrated genomes (ciHHV-6A/B). This integrated form affects 0.1-1 % of the human population, where potentially virus gene expression could be in every cell, although virus relationships and health effects are not clear. In a Czech/German patient cohort ciHHV-6A was more common and diverse than ciHHV-6B. Quantitative PCR, nucleotide sequencing and telomeric integration site amplification characterized ciHHV-6 in 44 German myocarditis/cardiomyopathy and Czech malignancy/inflammatory disease (MI) patients plus donors. Comparisons were made to sequences from global virus reference strains, and blood DNA from childhood-infections from Zambia (HHV-6A mainly) and Japan (HHV-6B). The MI cohort were 86 % (18/21) ciHHV-6A, the cardiac cohort 65 % (13/20) ciHHV-6B, suggesting different disease links. Reactivation was supported by findings of 1) recombination between ciHHV-6A and HHV-6B genes in 20 % (4/21) of the MI cohort; 2) expression in a patient subset, of early/late transcripts from the inflammatory mediator genes chemokine receptor U51 and chemokine U83, both identical to ciHHV-6A DNA sequences; and 3) superinfection shown by deep sequencing identifying minor virus-variants only in ciHHV-6A, which expressed transcripts, indicating virus infection reactivates latent ciHHV-6A. Half the MI cohort had more than two copies per cell, median 5.2, indicative of reactivation. Remarkably, the integrated genomes encoded the secreted-active form of virus chemokines, rare in virus from childhood-infections. This shows integrated virus genomes can contribute new human genes with links to inflammatory pathology and supports ciHHV-6A reactivation as a source for emergent infection.

Roseoloviruses in transplant recipients: clinical consequences and prospects for treatment and prevention trials

Roseoloviruses frequently reactivate in transplant recipients. We review the impact of Roseoloviruses in transplant recipients and highlight research priorities. Human herpesvirus 6A (HHV-6A) and HHV-6B were recently classified as distinct species with important differences. Both viruses can result in inherited chromosomally integrated HHV-6, which may cause complications after transplant. HHV-6B is the primary species associated with disease and appears to have pleiotropic effects on the central nervous system. Small preemptive and prophylactic studies have not shown a statistically significant impact on HHV-6 disease. Although Roseoloviruses are associated with diverse complications in transplant patients, studies providing strong evidence for a causal role are lacking. Trials focusing on prevention and treatment will be important to inform the significance of Roseolovirus reactivation.

Co-infection and clinical impact of human herpesvirus 5 and 6 in liver transplantation

BACKGROUND

Human herpesvirus (HHV) 5 and 6 remain latent after primary infection and can be reactivated after immunosuppression for organ transplantation. An association between HHV-5 and HHV-6 has been reported in liver transplant patients. The coinfection is associated with clinical manifestations and graft dysfunction.

OBJECTIVE

The aim of this study was to monitor herpesviruses in liver transplant recipients to better understand issues involving coinfection with HHV-5/6 and correlations with acute cellular rejection episodes and bacterial infections.

METHODS

Forty-five adult liver transplant patients of median age 47 years (range, 18-66), gave blood samples and liver biopsies in the first 6 months after their surgeries. Viremia was detected with the use of nested PCR and antigenemia; the Banff classification was used to detect allograft rejection.

RESULTS

IgG positive for HHV-5 was observed in 94% of subjects whose main indication (67%) for transplantation was hepatitis C. Twenty-three (51.1%) displayed cytomeg virus (CMV) infections and 12 (26.7%) HHV-6 infection. There were 6 patients (13.3%) with HHV-5/6 coinfections. Eighteen of the 23 patients had CMV disease, showing a strong correlation between a positive test and CMV disease; 6 displayed an acute cellular rejection episode in the same period (χ(2) = 6.62; P < .03). Four out of 6 patients who displayed coinfections (HHV-5/6) had concomitant bacterial infections; 3/6 experienced graft rejection episodes. During follow-up, 1 patient had HHV-6 infection diagnosed as encephalitis followed by fever on the 24th day after surgery. The median 32 days for HHV-6 detection by nested PCR positivity was shorter than 38 days for HHV-5.

CONCLUSIONS

HHV-5/6-infected patients displayed more allograft rejection episodes, coinfections, and concomitant bacterial infections, besides an higher risk for CMV disease.

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

Human herpesviruses (HHV) 6 and 7 are ubiquitous infections that reactivate commonly in transplant recipients. However, clinical diseases due to these viruses are reported only in 1% of solid organ transplant recipients. Fever, rash and bone marrow suppression are the most common manifestations, but symptoms of tissue invasive disease may be observed. Treatment of HHV-6 and HHV-7 disease includes antiviral therapy and cautious reduction in immunosuppression. HHV-8 is an oncogenic gamma-herpesvirus that causes Kaposi's sarcoma, Castleman's disease and primary effusion lymphomas in transplant recipients. Nonmalignant diseases such as bone marrow suppression and multiorgan failure have also been associated with HHV-8. Reduction in immunosuppression is the first line treatment of HHV-8 infection. Other alternatives for treatment, especially for HHV-8 diseases not responsive to immuno-minimization strategies, are surgery and chemotherapy. Sirolimus has been shown to be a beneficial component for the treatment of Kaposi's sarcoma and the role of antivirals for HHV-8 infection is being investigated.

Human herpesvirus 6 (HHV-6) disease in the setting of transplantation

PURPOSE OF REVIEW

Human herpesvirus 6 (HHV-6) frequently reactivates after solid-organ and hematopoietic cell transplantation (HCT), and it has been associated with important outcomes in these settings. In 1-2% of recipients or donors, HHV-6 was inherited through chromosomal integration. Although HHV-6 chromosomal integration has not been associated with disease, the resulting very high levels of HHV-6 DNA in human tissue and blood samples can be challenging to interpret in the transplant setting. This review addresses the recent findings regarding the clinical outcomes associated with HHV-6 as well as diagnostic and therapeutic concerns.

RECENT FINDINGS

The evidence supports a causal association between HHV-6 and central nervous system disease. New studies have further characterized the impact of HHV-6 on the central nervous system. In addition, new studies have explored the associations between HHV-6 and other important outcomes. The implications of integrated HHV-6 in transplant recipients remain undefined, though the possibility of an association with organ rejection has been suggested. New exploratory data exist regarding the safety of antiviral prophylactic and preemptive strategies.

SUMMARY

Our understanding of the full clinical impact of HHV-6 in the transplant population remains incomplete. A large antiviral trial would not only help to further define causality between HHV-6 associated clinical outcomes but also start to define preventive strategies.

Antiviral therapy of two patients with chromosomally-integrated human herpesvirus-6A presenting with cognitive dysfunction

BACKGROUND

Human herpesvirus 6 (HHV-6) is a neurotropic virus implicated in central nervous system (CNS) dysfunction, multiple sclerosis, seizures and encephalitis. Inherited or "chromosomally integrated" HHV-6 (CIHHV-6) is a condition characterized by high DNA loads and germ line transmission of HHV-6 genomes, which are integrated into the telomere.

OBJECTIVES

We previously reported that integrated HHV-6 can be reactivated by trichostatin A in vitro. Therefore, we hypothesized that a broad array of neurological symptoms of CIHHV-6 patients may respond to antiviral drug treatment.

STUDY DESIGN

The patients have been treated with antiviral drugs and monitored for viral load, late mRNA, and clinical improvement.

RESULTS

Antiviral therapy of two CIHHV patients resulted in successful clinical resolution. However, both patients relapsed on multiple occasions within 4-6 months of cessation of antiviral therapy.

CONCLUSIONS

Successful antiviral drug treatment suggests that clinical symptoms of these patients were due to symptomatic reactivation of CIHHV-6. Alternatively, some CIHHV-6 patients may have a reduced resistance to community-acquired HHV-6 strains due to tolerance leading to persistent infections.

Human herpesvirus-6 infections in kidney, liver, lung, and heart transplantation: review

Human herpesvirus-6 (HHV-6), which comprises of HHV-6A and HHV-6B, is a common infection after solid organ transplantation. The rate of HHV-6 reactivation is high, although clinical disease is not common. Only 1% of transplant recipients will develop clinical illness associated with HHV-6 infection, and most are ascribable to HHV-6B. Fever, myelosuppression, and end-organ disease, including hepatitis and encephalitis, have been reported. HHV-6 has also been associated with various indirect effects, including a higher rate of CMV disease, acute and chronic graft rejection, and opportunistic infection such as invasive fungal disease. All-cause mortality is increased in solid organ transplant recipients with HHV-6 infection. HHV-6 is somewhat unique among human viruses because of its ability to integrate into the host chromosome. The clinical significance of chromosomally integrated HHV-6 is not yet defined, although a higher rate of bacterial infection and allograft rejection has been suggested. The diagnosis of HHV-6 is now commonly made using nucleic acid testing for HHV-6 DNA in clinical samples, but this can be difficult to interpret owing to the common nature of asymptomatic viral reactivation. Treatment of HHV-6 is indicated in established end-organ disease such as encephalitis. Foscarnet, ganciclovir, and cidofovir have been used for treatment.

The Link between Hypersensitivity Syndrome Reaction Development and Human Herpes Virus-6 Reactivation

Background. There are challenges in the clinical diagnosis of drug-induced injury and in obtaining information on the reactivation of human herpes viruses (HHV) during idiosyncratic adverse drug reactions. Objectives. (i) To develop a unified list of drugs incriminated in drug-induced hepatotoxicity and severe cutaneous reactions, in which drug hypersensitivity leads to HHV-6 reactivation and further complication of therapy and recovery and (ii) to supplement the already available data on reporting frequencies of liver- or skin-induced cases with knowledge of individual case reports, including HHV-6 reactivation and briefly introducing chromosomally integrated HHV-6. Data Sources and Extraction. Drugs identified as causes of (i) idiosyncratic reactions, (ii) drug-induced hypersensitivity, drug-induced hepatotoxicity, acute liver failure, and Stevens-Johnson syndrome, and (iii) human herpes virus reactivation in PubMed since 1997 have been collected and discussed. Results. Data presented in this paper show that HHV-6 reactivation is associated with more severe organ involvement and a prolonged course of disease. Conclusion. This analysis of HHV-6 reactivation associated with drug-induced severe cutaneous reactions and hepatotoxicity will aid in causality assessment and clinical diagnosis of possible life-threatening events and will provide a basis for further patient characterization and therapy.

Chromosomally integrated human herpesvirus 6: questions and answers

Chromosomally integrated human herpesvirus 6 (ciHHV-6) is a condition in which the complete HHV-6 genome is integrated into the host germ line genome and is vertically transmitted in a Mendelian manner. The condition is found in less than 1% of controls in the USA and UK, but has been found at a somewhat higher prevalence in transplant recipients and other patient populations in several small studies. HHV-6 levels in whole blood that exceed 5.5 log10 copies/ml are strongly suggestive of ciHHV-6. Monitoring DNA load in plasma and serum is unreliable, both for identifying and for monitoring subjects with ciHHV-6 due to cell lysis and release of cellular DNA. High HHV-6 DNA loads associated with ciHHV-6 can lead to erroneous diagnosis of active infection. Transplant recipients with ciHHV-6 may be at increased risk for bacterial infection and graft rejection. ciHHV-6 can be induced to a state of active viral replication in vitro. It is not known whether ciHHV-6 individuals are put at clinical risk by the use of drugs that have been associated with HHV-6 reactivation in vivo or in vitro. Nonetheless, we urge careful observation when use of such drugs is indicated in individuals known to have ciHHV-6. Little is known about whether individuals with ciHHV-6 develop immune tolerance for viral proteins. Further research is needed to determine the role of ciHHV-6 in disease. Copyright © 2011 John Wiley & Sons, Ltd.