Human herpesvirus-6 and acute liver failure

Clinical and Histopathologic Characteristics of Acute Severe Hepatitis Associated With Human Herpesvirus 6 Infection

Acute severe hepatitis associated with active human herpesvirus 6 (HHV-6) infection is a rare life-threatening condition with unclear clinical course and histopathology. In this study, we retrospectively analyzed 5 patients with indeterminate acute severe hepatitis found to have active hepatic HHV-6 infection during care. All patients were previously healthy children presenting with a nonspecific prodrome. Four developed acute liver failure (ALF) and 3 received liver transplantation. The explanted livers and biopsies demonstrated a centrilobular pattern of necroinflammation characterized by moderate to marked central perivenulitis and confluent centrilobular to panlobular necrosis in 4 cases, accompanied by marked hepatocellular swelling and milder portal inflammation in 3. Central perivenulitis was more prominent in comparison to a control of group of ALF without HHV-6 (P=0.01). When compared with the children with acute severe hepatitis associated with adenovirus encountered in the recent outbreak, both central perivenulitis and centrilobular necrosis were significant predictors for association with HHV-6 (P<0.01). Liver immunohistochemistry detected HHV-6 structural protein in biliary epithelium in all cases and a predominance of CD8+ T cells in the perivenular inflammatory infiltrate. Among the 4 patients with ALF, one received early anti-HHV-6 therapy and had transplant-free survival, while the other 3 received either general prophylactic antiviral treatment only (n=2) or late anti-HHV-6 therapy (n=1) and needed liver transplantation. Our findings were similar to those in previously reported cases. In summary, acute severe hepatitis associated with HHV-6 tends to affect children, progress to ALF, and exhibit characteristic centrilobular necroinflammation which likely represents an immune-mediated process.

Could Herpesviridae be the cause of severe acute hepatitis of unknown origin in children?

INTRODUCTION

Severe acute hepatitis (SAH) is defined by a severe inflammation of hepatocytes in the liver parenchyma which can lead to an acute liver failure, a clinical condition with high mortality rate that can be triggered by several factors but is usually associated to hepatotropic viruses' infection. In 2022, cases of children with severe acute hepatitis of unknown origin hospitalized in Glasgow, Scotland, were reported. Possible causes of this condition include, but are not limited to, undiagnosed viral (and non-viral) infections, autoimmune hepatitis, drug and/or chemical toxicity, mitochondrial chain respiratory and metabolic disorders.

AREAS COVERED

Herpesviruses can cause severe acute hepatitis, but little is known about the role and the mechanisms of herpesviruses as a causative agent of this type of hepatitis. We review the role of herpesviruses as causative agent of SAH in children and other possible mechanisms involved in this disease.

EXPERT OPINION

Differential diagnosis for herpesvirus in SAH should be implemented in all settings. Alternative fluids, such as saliva and dried blood, could be used in the diagnosis to overwhelm the availability of biological specimens at sufficient volume. In the future, genetic studies could also be added to increase the knowledge about severe acute hepatitis in children.

Case report: Acute liver failure in children and the human herpes virus 6-? A factor in the recent epidemic

The 2022 worldwide epidemic of acute hepatitis and liver failure in young children has led to a focus on unusual causes for childhood acute hepatitis. In the UK epidemic, human herpes virus subtype 6B (HHV-6B) was detected along with adenovirus subtype-41F in severely affected children, especially in those requiring liver transplantation (LT). The lifting of COVID lock-down measures has coincided with the rise in these common childhood infections with a higher than expected rate of systemic complications. The sudden exposure of young children to common childhood infections from which they were protected during the pandemic may have induced an abnormal immune mediated response potentiated by multiple pathogen exposure. Primary HHV-6 infection is one such common childhood infection. Classically known as Roseola infantum due to the appearance of a widespread erythematous rash on fever subsidence (exanthema subitem), it has a peak incidence of 6-12 months of age and almost all children will have been infected by age 2. It is the virus most frequently associated with febrile convulsions but the more serious complications of hepatitis and liver failure are rare. We report on the historic cases of three female infants who had suspected primary HHV-6B infection, acute hepatitis and rapid progression to acute liver failure (ALF) requiring LT. Appearances of their native liver were identical to those described in children in the recent hepatitis epidemic. Deteriorating clinical trajectories of recurrent graft hepatitis and rejection-like episodes followed and all three succumbed to graft failure with HHV-6B detected posthumously in their liver allografts. Our case series and the serious complications observed with the recent rise in common childhood infections is a reminder that these routinely encountered pathogens can be deadly especially in the young immunologically untrained. We advocate for HHV-6 to be screened for routinely in children with acute hepatitis and the use of effective HHV-6 anti-viral prophylaxis to prevent recurrence post-transplant.

Investigation of Inherited Chromosomally Integrated Human Herpesvirus-6A+ and -6B+ in a Patient with Ulipristal Acetate-Induced Fulminant Hepatic Failure

Inherited chromosomally integrated (ici) human herpes virus 6 (HHV-6) is estimated to occur in 0.6–2.7% of people worldwide. HHV-6 comprises two distinct species: HHV-6A and HHV-6B. Both HHV-6A and HHV-6B integration have been reported. Several drugs are capable of activating iciHHV-6 in tissues, the consequences of which are poorly understood. We report herein a case of a woman with iciHHV-6A+ and iciHHV-6B+, who developed ulipristal acetate (a selective progesterone receptor modulator)-induced fulminant hepatic failure that required liver transplantation. We confirmed the presence of ~one copy per cell of both HHV-6A and HHV-6B DNA in her hair follicles using multiplex HHV-6A/B real-time PCR and demonstrated the Mendelian inheritance of both iciHHV-6A and iciHHV-6B in her family members over three generations. Because of the rarity of this presentation, we discuss herein the possible links between reactivated HHV-6 from iciHHV-6A and/or iciHHV-6B and adverse drug reactions, suggesting that iciHHV-6 could be screened before the introduction of any hepatotoxic drugs to exclude HHV-6 active disease or combined idiosyncratic drug-induced liver injury in these patients.

Trimethoprim-induced drug reaction with eosinophilia and systemic symptoms (DRESS) associated with reactivation of human herpes virus-6 (HHV-6) leading to acute liver failure

Drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome can have insidious symptoms which may lead to acute liver failure and death. Prompt recognition, stopping offending drug, and initiating corticosteroid are the mainstay of treatment. Early involvement of a specialist liver unit is vital.

Evaluating for Human Herpesvirus 6 in the Liver Explants of Children With Liver Failure of Unknown Etiology

BACKGROUND

Liver failure of unknown etiology (LFUE) has a transplant-free survival rate <25%. Human herpesvirus 6 (HHV-6) may be associated with LFUE, but studies are limited by small sample size.

METHODS

We identified all children who underwent liver transplant for LFUE at a single quaternary children's hospital; 51/65 cases could be age matched with controls (children who underwent liver transplant for metabolic liver disease). Quantitative polymerase chain reaction for HHV-6 was performed on DNA from formalin-fixed paraffin-embedded liver explant tissue.

RESULTS

HHV-6 was detected in 34/51 cases (66.7%) and 19/51 controls (37.3%) (P = .005). Average HHV-6 viral load was 213207 copies/106 cells in positive cases (range: 7293-1102030) and 38115 copies/106 cells in positive controls (range: 1382-122375) (P = .0008). HHV-6 was present significantly more often in cases compared to controls in patients younger than 6 years. In particular, in patients younger than 3 years, HHV-6 was present in 13/27 cases (48.1%) and 2/27 controls (7.4%) (P = .0009).

CONCLUSIONS

HHV-6 was detected in liver explants significantly more often and in higher quantities in children transplanted for LFUE compared to controls, suggesting HHV-6 should be evaluated in young children who present with LFUE.

Current understanding of human herpesvirus 6 (HHV-6) chromosomal integration

Human herpesvirus 6A (HHV-6A) and 6B (HHV-6B) are members of the genus Roseolovirus in the Betaherpesvirinae subfamily. HHV-6B infects humans in the first years of life, has a seroprevalence of more than 90% and causes Roseola Infantum, but less is known about HHV-6A. While most other herpesviruses maintain their latent genome as a circular episome, HHV-6A and HHV-6B (HHV-6A/B) have been shown to integrate their genome into the telomeres of infected cells. HHV-6A/B can also integrate into the chromosomes of germ cells, resulting in individuals carrying a copy of the virus genome in every nucleated cell of their bodies. This review highlights our current understanding of HHV-6A/B integration and reactivation as well as aspects that should be addressed in the future of this relatively young research area. It forms part of an online symposium on the prevention and therapy of DNA virus infections, dedicated to the memory of Mark Prichard.

Acute Liver Failure: An Update

Pediatric acute liver failure (PALF) is a dynamic, life-threatening condition of disparate etiology. Management of PALF is dependent on intensive collaborative clinical care and support. Proper recognition and treatment of common complications of liver failure are critical to optimizing outcomes. In parallel, investigations to identify underlying cause and the implementation of timely, appropriate treatment can be life-saving. Predicting patient outcome in the era of liver transplantation has been unfulfilling and better predictive models must be developed for proper stewardship of the limited resource of organ availability.

Acute Liver Failure in an Adolescent Male Induced by Human Herpesvirus 6 (HHV-6): A Case Report With Literature Review

A previously healthy 11-year-old Caucasian boy presented with a 2-week history of nonspecific symptoms of nausea and nonbilious, nonbloody emesis. He developed significant jaundice and hepatic encephalopathy within 1 week of beginning symptoms and was discovered to have fulminant liver failure. Extensive work-ups for underlying etiologies included serologic evaluation for underlying chronic liver diseases, toxicology screening, inborn errors of metabolism, and infectious diseases. The results of the entire assessment were negative except for human herpesvirus 6B, which was detected in the liver by quantitative real-time polymerase chain reaction and immunohistochemical analysis. The patient underwent ABO-compatible liver transplantation and has had clinically stable health, with no evidence to date of complications associated with HHV-6 or other members of the herpesvirus family.

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.

Glycoproteins of HHV-6A and HHV-6B

Recently, human herpesvirus 6A and 6B (HHV-6A and HHV-6B) were classified into distinct species. Although these two viruses share many similarities, cell tropism is one of their striking differences, which is partially because of the difference in their entry machinery. Many glycoproteins of HHV-6A/B have been identified and analyzed in detail, especially in their functions during entry process into host cells. Some of these glycoproteins were unique to HHV-6A/B. The cellular factors associated with these viral glycoproteins (or glycoprotein complex) were also identified in recent years. Detailed interaction analyses were also conducted, which could partially prove the difference of entry machinery in these two viruses. Although there are still issues that should be addressed, all the knowledges that have been earned in recent years could not only help us to understand these viruses' entry mechanism well but also would contribute to the development of the therapy and/or prophylaxis methods for HHV-6A/B-associated diseases.

The viral paradigm in type 1 diabetes: Who are the main suspects?

Type 1 diabetes (T1D) is an autoimmune disease characterized by the loss of pancreatic beta cells in the islets of Langerhans. Although genetic predisposition plays an important role in T1D development, studies of identical twins suggest that environmental factors such as viruses and other pathogens may be critical triggers either through direct cytolytic effect and gradual beta cell destruction, or by bystander activation of the immune system. In addition, viruses may circumvent the host immune response and have the capacity to establish chronic lifelong infections. The association of various viral infections with the induction of T1D has been extensively studied at the serological and epidemiological level. However, there is still little evidence from studies of human pancreas to confirm their presence or a causal role in disease pathogenesis. In this review, we identify possible suspects for viral triggers of disease and explain their potential roles in the "viral paradigm" of T1D.

Fulminant hepatic failure attributed to infection with human herpesvirus 6 (HHV-6) in an immunocompetent woman: A case report and review of the literature

Mild disease due to human herpesvirus-6 (HHV-6) has been reported in healthy children. Severe disease due to this virus can occur in immunocompromised patients but is rarely reported in previously healthy adults. We report the case of a previously healthy woman who presented with a skin rash, mild upper respiratory symptoms, and abdominal pain and succumbed to fulminant hepatic failure attributed to infection with HHV-6B. HHV-6 may be more commonly associated with fulminant hepatitis in immunocompetent patients than previously thought and should be considered in the differential diagnosis of patients presenting with skin rash, upper respiratory symptoms, and unexplained hepatitis.

Laboratory and clinical aspects of human herpesvirus 6 infections

Human herpesvirus 6 (HHV-6) is a widespread betaherpesvirus which is genetically related to human cytomegalovirus (HCMV) and now encompasses two different species: HHV-6A and HHV-6B. HHV-6 exhibits a wide cell tropism in vivo and, like other herpesviruses, induces a lifelong latent infection in humans. As a noticeable difference with respect to other human herpesviruses, genomic HHV-6 DNA is covalently integrated into the subtelomeric region of cell chromosomes (ciHHV-6) in about 1% of the general population. Although it is infrequent, this may be a confounding factor for the diagnosis of active viral infection. The diagnosis of HHV-6 infection is performed by both serologic and direct methods. The most prominent technique is the quantification of viral DNA in blood, other body fluids, and organs by means of real-time PCR. Many active HHV-6 infections, corresponding to primary infections, reactivations, or exogenous reinfections, are asymptomatic. However, the virus may be the cause of serious diseases, particularly in immunocompromised individuals. As emblematic examples of HHV-6 pathogenicity, exanthema subitum, a benign disease of infancy, is associated with primary infection, whereas further virus reactivations can induce severe encephalitis cases, particularly in hematopoietic stem cell transplant recipients. Generally speaking, the formal demonstration of the causative role of HHV-6 in many acute and chronic human diseases is difficult due to the ubiquitous nature of the virus, chronicity of infection, existence of two distinct species, and limitations of current investigational tools. The antiviral compounds ganciclovir, foscarnet, and cidofovir are effective against active HHV-6 infections, but the indications for treatment, as well as the conditions of drug administration, are not formally approved to date. There are still numerous pending questions about HHV-6 which should stimulate future research works on the pathophysiology, diagnosis, and therapy of this remarkable human virus.

Liver involvement in systemic infection

The liver is often involved in systemic infections, resulting in various types of abnormal liver function test results. In particular, hyperbilirubinemia in the range of 2-10 mg/dL is often seen in patients with sepsis, and several mechanisms for this phenomenon have been proposed. In this review, we summarize how the liver is involved in various systemic infections that are not considered to be primarily hepatotropic. In most patients with systemic infections, treatment for the invading microbes is enough to normalize the liver function tests. However, some patients may show severe liver injury or fulminant hepatic failure, requiring intensive treatment of the liver.

Hepatitis due to human herpesvirus 6B after hematopoietic cell transplantation and a review of the literature

Human herpesvirus 6B (HHV-6B) is an opportunistic pathogen associated with a growing number of complications in immunocompromised patients. Multiple reports of HHV-6B-associated hepatitis following primary HHV-6 infection and liver transplantation have appeared, but this has only been well documented in 1 patient after hematopoietic cell transplantation (HCT). This report describes a case of acute hepatitis likely caused by HHV-6B in an HCT recipient who was successfully treated with ganciclovir. HHV-6B DNA was demonstrated in plasma and hepatic tissue using quantitative polymerase chain reaction and immunohistochemical stains. Chromosomal integration was ruled out. We review the literature reporting HHV-6B-associated hepatitis, which may be an underappreciated cause of liver disease after HCT.

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.

[Human herpesvirus-6 and human herpesvirus-7 (HHV-6, HHV-7)]

human herpesvirus 6 (HHV-6) is the major causative agent of exanthem subitum which is one of popular diseases in infant, and establishes latent infections in adults of more than 90%. Recently, the encephalitis caused by reactivated- HHV-6 has been shown in patients after transplantation. In addition, the relationship HHV-6 and drug-induced hypersensitivity syndrome has also been reported. human herpesvirus 7 (HHV-7) was isolated from the stimulated-peripheral blood lymphocytes of a healthy individual, and also causes exanthema subitum. Both viruses are related viruses which belong to betaherpesvirus subfamily, and replicate and produce progeny viruses in T cells.

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.

Drug-induced hypersensitivity syndrome associated with reactivation of human herpesvirus 6 presenting with severe hepatic injury

Little is known about the pathophysiology of liver complication seen in drug-induced hypersensitivity syndrome (DIHS). We describe herein a 32-year-old Japanese man with DIHS due to salazosulfapyridine (SASP) associated with reactivation of human herpesvirus 6 (HHV-6) presenting with severe acute hepatic injury. The patient, with a 1-year history of ulcerative colitis (UC), presented with high fever and abnormally elevated liver enzymes. Six weeks prior to his symptoms, prednisolone (PSL) and SASP had been started because of UC aggravation. Besides fever and liver dysfunction, the appearance of atypical lymphocytes together with eosinophils and generalized erythematous maculopapular skin rash developed sequentially, and a diagnosis of DIHS was established. Despite cessation of SASP and increased dose of PSL, his initial abnormalities continued, and biphasic second alanine aminotransferase (ALT) flare with deep jaundice worsened. Based on the significant increase in the titer of HHV-6 IgG antibodies at the second peak of ALT level without HHV-6 IgM antibody elevation, strongly suggesting reactivation of the virus, HHV-6 was first considered to directly contribute to the deterioration of liver function. However, extensive histological analysis of the liver led to the realization that the cause of the DIHS liver injury was essentially drug-related hepatotoxicity induced by SASP, causing wide-ranging damage to both the hepatocytes and cholangiocytes.

Liver in systemic disease

Potential causes of abnormal liver function tests include viral hepatitis, alcohol intake, nonalcoholic fatty liver disease, autoimmune liver diseases, hereditary diseases, hepatobiliary malignancies or infection, gallstones and drug-induced liver injury. Moreover, the liver may be involved in systemic diseases that mainly affect other organs. Therefore, in patients without etiology of liver injury by screening serology and diagnostic imaging, but who have systemic diseases, the abnormal liver function test results might be caused by the systemic disease. In most of these patients, the systemic disease should be treated primarily. However, some patients with systemic disease and severe liver injury or fulminant hepatic failure require intensive treatments of the liver.

Critical role of toll-like receptors and the common TLR adaptor, MyD88, in induction of granulomas and liver injury

BACKGROUND/AIMS

Toll-like receptors (TLR) recognize pathogens and regulate innate immune activation. Here, we investigated the roles of TLR9 and the common TLR adaptor, MyD88, in liver injury.

METHODS

C57BL6, TLR9(-/-), IFNgamma(-/-) or MyD88(-/-) mice were primed with Propionibacterium acnes, TLR9 (CpG) or TLR2 (lipoteichoic acid) ligands followed by LPS challenge. ALT, cytokines and liver histology were assessed.

RESULTS

Selective priming through TLR9 but not TLR2 induced granulomas, elevated serum ALT, and sensitized C57BL6 mice to increased LPS-induced serum IL-6, IL-12 and IFNgamma levels. Further, TLR2 and TLR9 ligands synergized in induction of granulomas and sensitization to LPS-induced inflammation. IFNgamma induction by P. acnes, TLR2 and TLR9 ligands required MyD88. In MyD88(-/-) mice P. acnes failed to induce granulomas and both MyD88 and TLR9 deficiency prevented P. acnes-induced sensitization to LPS. Increased mRNA expression of genes of the TLR4 signaling complex (TLR4, CD14, MD-2, and MyD88) and the NADPH complexes (p47phox, p67phox, gp91phox, and p22phox) was induced by priming with P. acnes or TLR9 plus TLR2 suggesting mechanisms for LPS sensitization and liver injury.

CONCLUSIONS

TLR9+/-TLR2 activation via MyD88-dependent pathways plays a pivotal role in liver sensitization and granuloma formation.

Reactivation of Viruses in Solid Organ Transplant Patients Receiving Cytomegalovirus Prophylaxis

A series of substudies of a large international cytomegalovirus (CMV) prophylaxis trial investigated the incidence and clinical relevance of reactivation of human herpesviruses 6, 7, and 8, varicella zoster virus, Epstein-Barr virus, polyomavirus, and adenovirus, and the effect of CMV prophylaxis on clinical and subclinical non-CMV viral infections, in adult solid organ transplant (SOT) patients. Results of the substudy analyses showed that viremia caused by a number of viruses is surprisingly common posttransplantation; most of these infections likely represent reactivation of endogenous latent virus. In addition, although infection or active viral replication was common in this cohort of SOT patients, symptomatic disease due to these viruses was uncommon and the clinical sequelae of viremia were unclear or not apparent. CMV prophylaxis may have modified the natural history of some of these non-CMV viral infections.

Pretransplant human herpesvirus 6 infection of patients with acute liver failure is a risk factor for posttransplant human herpesvirus 6 infection of the liver

BACKGROUND

Acute liver failure (ALF) is a significant cause of liver transplantation. We have previously reported that human herpesvirus-6 (HHV-6) was found in most livers of patients with ALF of unknown origin ending up with liver transplantation. In this study, we investigated the posttransplant HHV-6 infection of the liver graft in these patients.

METHODS

Thirty-two patients transplanted due to ALF were included in this retrospective study. Twelve of the 15 patients with unknown cause and four of 17 patients with a known cause of ALF had HHV-6 antigens in the explanted liver. Altogether, 18 patients had some pretransplant evidence of HHV-6. After transplantation, the patients were frequently monitored for the viruses, and biopsy histology was performed in every case of graft dysfunction. HHV-6 was demonstrated in liver tissue by immunohistochemistry.

RESULTS

During the follow-up of 6 months, hepatic HHV-6 infection was demonstrated in 9 of the 18 patients, at a mean 19 days (6-38 days) after transplantation. All patients with posttransplant HHV-6 showed graft dysfunction. In biopsy histology, seven out of these nine patients demonstrated viral infection, one of them also having CMV antigens in the liver. None of those patients without evidence of pretransplant HHV-6 showed HHV-6 in the posttransplant biopsies. Posttransplant HHV-6 was not treated and the virus had no effect on 1-year patient or graft survivals.

CONCLUSION

Pretransplant hepatic HHV-6 infection of patients with ALF is a risk factor for posttransplant HHV-6 infection and liver dysfunction, but has no effect on 1-year graft or patient survival.

Syndrome d’hypersensibilité médicamenteuse associé à une primo-infection HHV6

INTRODUCTION

Drug hypersensitivity syndrome is a severe life-threatening drug reaction. An association between this syndrome and HHV6 reactivation has been hypothesized.

CASE-REPORT

A 45 year-old women was treated with sulfasalazine for polyarthralgia. One month after beginning the treatment, she developed a drug hypersensitivity syndrome with severe acute hepatic failure. HHV6 serology and serum PCR revealed a primary HHV6 infection.

DISCUSSION

We report the second case of drug hypersensitivity syndrome associated with a primary HHV6 infection. An immunological disorder may explain such an association by increasing viral replication. Detection and titration of anti-HHV6 antibodies in each case of drug hypersensitivity syndrome should help to confirm this association and possibly modify treatment strategy.

Human herpesvirus-6 hepatitis associated with cyclosporine-A encephalitis after bone marrow transplantation for chronic myeloid leukemia

A 31-year-old man referred to our hospital for treatment of his chronic myeloid leukemia (CML) in the first chronic phase by bone marrow transplantation. We pretreated him with cyclophosphamide and total body irradiation and bone marrow transplantation (BMT) was carried out. On day 31, the engraftment was confirmed and on day 52, acute graft versus host disease (GVHD) was observed. On day 189, he lost consciousness due to cyclosporine A-induced leukoencephalopathy and 375 mg cyclosporine A was changed to 100 mg prednisolone. On day 199, liver dysfunction (AST 410 IU/L, ALT 557 IU/L, gammaGTP 385 IU/L, ALP 363 IU/L, D-Bil 0.3 mg/dl) developed and a liver biopsy was performed. PCR analysis of DNA from the liver biopsy specimen was positive for HHV-6 and immunostaining using anti-HHV-6 and anti-HHV-6b antibodies showed positive staining in the cytosol of hepatocytes. No other viruses were found to induce hepatitis. From these results, he was diagnosed as having HHV-6 hepatitis and it was successfully treated with gancyclovir (GCV) administration.

HHV-6-related acute liver failure in two immunocompetent adults: favourable outcome after liver transplantation and/or ganciclovir therapy

Fulminant hepatitis of unknown origin remain a significant cause of mortality, for which liver transplantation is often considered as the only therapeutic option. In retrospective studies, human herpesvirus 6 (HHV-6) infections have been associated with such diseases, but the diagnosis of HHV-6 infection of the liver is rarely established during the acute phase of liver failure. Using real-time polymerase chain reaction (PCR), we diagnosed two cases of severe acute liver failure (ALF) related to HHV-6 occurring in immunocompetent young adults. Both cases had a favourable outcome, one after valganciclovir therapy, one after liver transplantation associated with ganciclovir. Viral origin was evidenced in each case by the detection of high amounts of HHV-6 DNA in liver tissue by the PCR assay. The decrease of intrahepatic viral load after therapeutic intervention was also monitored by quantitative PCR and paralleled in the two cases the clinical improvement. Diagnosis of HHV-6 infection must be systematically evoked in case of unexplained ALF, since it might lead to specific therapeutic interventions, in addition of liver transplantation.

Impact of human herpesvirus-6 after haematopoietic stem cell transplantation

We studied 228 consecutive stem cell transplant recipients, screened for reactivation of human herpesvirus-6 (HHV-6) in peripheral blood and other specimens as clinically indicated by means of qualitative polymerase chain reaction. Among them, 197 received an allograft and 31 autograft. Ninety-six of 228 patients (42.1%) showed HHV-6 reactivation in peripheral blood and 129 of 228 (56.6%) demonstrated HHV-6 in at least one of the specimens tested. 41.9% of patients were asymptomatic when HHV-6 was identified. Clinical features, noted when HHV-6 was detected, included interstitial or alveolar pneumonia, gastroduodenal and colorectal disease, bone marrow suppression and liver disease. However, based on clinical and histopathological criteria, HHV-6 was considered a causal agent in only a minority of patients, in particular, those suffering from bone marrow suppression (n = 11), gastroduodenitis (five), colitis (three), interstitial/alveolar pneumonia (five), skin rash (one), pericarditis (two) and encephalitis (one). HHV-6 reactivation was significantly associated with the occurrence of graft-versus-host disease [odds ratio (OR) 5.31], Epstein-Barr virus coinfection (OR 8.89) and unrelated donor transplantation (OR 5.67) indicating an increased stage of immunosuppression.

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).

Acute liver failure

Acute liver failure is a rare and life-threatening clinical syndrome following severe hepatic injury. Depending on the rapidity of its development, two distinct complications contribute to a high mortality: in hyperacute liver failure, rapid development of massive hepatic necrosis and apoptosis gives rise to severe hyperammonemia, hepatic encephalopathy and life-threatening cerebral edema. The high risk of cerebral herniation requires early listing for emergency liver transplantation. Patients with hyperacute liver failure surviving the initial episode of cerebral edema have a substantial potential for hepatic recovery. If progressive hepatic failure develops more slowly, astrocytic osmoregulation prevents cerebral herniation in most instances. Unfortunately, these patients have a small potential of hepatic regeneration and transplantation should be performed before renal failure, sepsis or multiorgan failure emerge. Experimental treatment methods including detoxification by artificial or bioartificial liver support or by stimulating hepatic regeneration are currently evaluated. Recognition of ammonia toxicity has stimulated the search for early ammonia-lowering strategies and strongly renewed the interest in dialytic therapies. Anti-apoptotic interventions are among the most promising pharmacological options for the near future.

Infection with human herpesvirus 6 after kidney-pancreas transplant

We describe the first known case of symptomatic infection resulting from human herpesvirus-6 (HHV-6) in simultaneous pancreas-kidney transplant recipients. The role of HHV-6 in solid-organ transplant recipients is not well defined. In hematopoietic stem cell transplantation (SCT) HHV-6 may cause fever, rash, myelosuppression, interstitial pneumonitis, and encephalitis.