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

Viral infections in lung transplantation

Viral infections account for up to 30% of all infectious complications in lung transplant recipients, remaining a significant cause of morbidity and even mortality. Impact of viral infections is not only due to the direct effects of viral replication, but also to immunologically-mediated lung injury that may lead to acute rejection and chronic lung allograft dysfunction. This has particularly been seen in infections caused by herpesviruses and respiratory viruses. The implementation of universal preventive measures against cytomegalovirus (CMV) and influenza (by means of antiviral prophylaxis and vaccination, respectively) and administration of early antiviral treatment have reduced the burden of these diseases and potentially their role in affecting allograft outcomes. New antivirals against CMV for prophylaxis and for treatment of antiviral-resistant CMV infection are currently being evaluated in transplant recipients, and may continue to improve the management of CMV in lung transplant recipients. However, new therapeutic and preventive strategies are highly needed for other viruses such as respiratory syncytial virus (RSV) or parainfluenza virus (PIV), including new antivirals and vaccines. This is particularly important in the advent of the COVID-19 pandemic, for which several unanswered questions remain, in particular on the best antiviral and immunomodulatory regimen for decreasing mortality specifically in lung transplant recipients. In conclusion, the appropriate management of viral complications after transplantation remain an essential step to continue improving survival and quality of life of lung transplant recipients.

Clinical course of human herpesvirus 6 infection in pediatric living donor liver transplantation

Differentiation between active and latent viral infection is critical for analysis of HHV-6-associated disease. HHV-6 infection has been associated with several clinical manifestations; however, the precise role of HHV-6 in pediatric LDLT remains unclear. This retrospective cohort study included 33 pediatric patients who received LDLT. All of the recipients were monitored for HHV-6 infection using viral isolation and real-time PCR. HHV-6 infection was observed in 14 of 33 (42.4%) recipients, and HHV-6B infection occurred within 2 weeks after LDLT in 10 of 14 (71.4%) recipients. HHV-6 was isolated from 10 of 33 (30.3%) recipients. Multivariate analysis showed that independent predictors of HHV-6B infection were age (OR 0.975; 95% CI 0.943-0.999; P = .041), PELD (OR 1.091; P = .038), and biliary atresia (OR 16.48; P = .035). The occurrence of unexplained fever was significantly higher in recipients with HHV-6B infection (11/14) compared with uninfected recipients (6/19) (P = .013). Additionally, ALT levels at 8 and 9 weeks after transplantation were significantly higher in the recipients with HHV-6B infection. Younger age, high MELD/PELD score, and biliary atresia as an underlying disease were identified as risk factors for viral infection.

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.

Human herpes virus 6 infection in pediatric organ transplant patients

Transplant patients need lifelong immunosuppressive medication, but this reduces their defense mechanisms, making them prone to viral infections and reactivations. We aimed to clarify the prevalence and clinical manifestations of the human herpes virus 6 (HHV-6) infection in children after pediatric solid organ transplants. Clinical findings and viral loads were compared between primary HHV-6 infections and reactivations. The study comprised 47 kidney, 25 liver, and 12 heart transplant patients who underwent surgery from 2009 to 2014. HHV-6 antibodies were analyzed before surgery, and HHV-6 DNAemia tests were regularly carried out after the transplant using a real-time quantitative polymerase chain reaction method. We found the primary HHV-6 infection in 19 of 22 (86%) seronegative patients, and it was more common in patients under 3 years of age (79%) than over 3 (38%, P=.0002). Post-transplant HHV-6 DNAemia affected 48 of 84 (57%) patients and was significantly higher in primary infections than reactivations (P=.001), and 17 of 48 (35%) patients had symptoms when it was detected at a median of 2 weeks post-transplant. The HHV-6 infection was common after solid organ transplants, especially under 3 years of age, and it typically started 2 weeks after surgery. Testing for HHV-6 DNAemia is recommended shortly after transplantation, especially in patients with fever, diarrhea, rash, seizures, or abnormal liver enzyme tests.

Multiple cavities with halo sign in a case of invasive pulmonary aspergillosis during therapy for drug-induced hypersensitivity syndrome

A 67-year-old female with rheumatoid arthritis and asthma-chronic obstructive pulmonary disease overlap syndrome was admitted for drug-induced hypersensitivity syndrome (DIHS) caused by salazosulfapyridine. Human herpes virus 6 (HHV-6) variant B was strongly positive on peripheral blood. Multiple cavities with ground grass opacities rapidly emerged predominantly in the upper and middle lobes. She was diagnosed with invasive pulmonary aspergillosis (IPA), and was treated successfully with antifungal agents. Therapeutic systemic corticosteroids, emphysematous change in the lungs, and the worsening of the patient's general condition due to DIHS were considered major contributing factor leading to IPA. HHV-6 reactivation could have an effect on clinical course of IPA. Cavities with halo sign would provide an early clue to IPA in non-neutropenic and immunosuppressive patients.

Infections due to human herpesvirus 6 in solid organ transplant recipients

PURPOSE OF REVIEW

This article summarizes the current state of the epidemiology, diagnosis, and management of human herpesvirus 6 (HHV-6) infection after solid organ transplantation.

RECENT FINDINGS

HHV-6 reactivates commonly during the early weeks after solid organ transplantation. However, disease due to HHV-6 is uncommon and is manifested as a febrile illness associated with rash and tissue-invasive manifestations such as encephalitis, hepatitis, pneumonitis, and gastrointestinal disease. HHV-6 has also been indirectly associated with other opportunistic infections such as cytomegalovirus and fungal infections. Molecular tests such as PCR assays are preferred methods for the diagnosis of HHV-6 infection. Recent guideline from the American Society of Transplantation Infectious Disease Community of Practice does not recommend specific antiviral prophylaxis or preemptive therapy for HHV-6 infection. For established disease, intravenous ganciclovir and foscarnet are considered first-line agents.

SUMMARY

Infection due to HHV-6 is a common after transplantation, but clinical disease is rare. Nonetheless, this infection has been indirectly associated with poor allograft and patient survival after transplantation. No specific prevention strategy is recommended, but treatment of established HHV-6 disease consists of antiviral therapy with intravenous ganciclovir and/or foscarnet, and reduction in immunosuppression.

Clinical consequences of human herpesvirus-6 DNAemia in peripheral blood in pediatric liver transplant recipients

The significance of HHV6 DNAemia after solid organ transplantation has not been fully determined. Our objectives were to determine the prevalence of HHV6 DNAemia in pediatric liver transplant recipients and to describe the associated clinical characteristics and outcomes. This was a retrospective case-control study. Eligible liver transplant patients aged ≤ 18 yr with HHV6 DNAemia were matched with two subjects without HHV6 DNAemia. Matching was by age ± 6 months. Among 154 subjects, 25 patients (16%) had HHV6 DNAemia detected by PCR in whole blood or plasma (M:F ratio = 0.9:1). While 28% of subjects with DNAemia (7/25) had symptoms consistent with HHV6 infection, active infection was detected in only four subjects (2.6% of liver transplant patients). The major symptoms/signs were fever, vomiting, lethargy, splenomegaly, bone marrow suppression, and elevated transaminases. The prevalence of DNAemia due to other herpesviruses in cases vs. controls was EBV 56% vs. 60%, CMV 12% vs. 12%, HHV7 20% vs. 12%; p value is not significant for all pairwise comparisons. HHV6 DNAemia in pediatric liver transplant patients is not an uncommon entity. While the clinical relevance is still not entirely established, active HHV6 infection and attributable symptoms are relatively rare.

Strategies for the prevention of infection after solid organ transplantation

Infection is a frequent complication of organ transplantation and is associated with significant morbidity and mortality. Preventative antimicrobial strategies are a key component of the care received by transplant patients. This review summarizes the evidence supporting anti-infective prophylaxis in this setting. Specific recommendations for the prevention of bacterial, fungal, viral and parasitic infection after transplant are made, with a focus on recent developments in the field of transplant infectious diseases.

Monitoring for HHV-6 infection after renal transplantation: evaluation of risk factors for sustained viral replication

BACKGROUND

Human herpesvirus-6 (HHV-6) is known to reactivate after renal transplantation and has been associated with several clinical manifestations. Risk factors for sustained viral replication, however, remain unclear.

METHODS

Thirty consecutive kidney transplant patients were prospectively followed for HHV-6 replication between February 2007 and February 2008. Plasma samples for DNA detection were collected from the donor and the recipient before transplantation and from the recipient weekly for the first 2 months after transplantation and then every 2 weeks for 2 additional months. HHV-6 active infection was defined as detection of viral DNA in plasma, by polymerase chain reaction, in at least two consecutive samples over an interval of at least 1 week.

RESULTS

Active viral infection was detected in 25% of the recipients before transplantation and 27% (8 of 30) of the patients after transplantation. The mean time to onset of viral replication was 28.1 days after transplantation and 7 of 8 (87.5%) were asymptomatic. Risk factors associated with active HHV-6 infection were receiving an organ from a living donor (P=0.028), recipients with IgM antibodies detected before transplantation (P=0.005), and pretransplantation recipient HHV-6 viral load more than 10,000 copies/mL plasma (P=0.034).

CONCLUSIONS

Active HHV-6 infection occurs early after renal transplantation and is mostly asymptomatic. Donor or recipient infection may occur at the time of transplantation and are related to higher rates of posttransplantation infections.

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.

Infections caused by herpes viruses other than cytomegalovirus in solid organ transplant recipients

Despite great advances in solid organ transplantation (SOT) in recent decades, infection remains a major cause of morbidity and mortality among SOT recipients. Members of the herpesvirus family are the most common viral pathogens causing disease in this patient population. Herpes viruses are large enveloped DNA viruses that commonly reactivate during periods of severe immunosuppression. Currently, infections caused by herpes viruses continue to complicate clinical management of transplant patients. Although cytomegalovirus (CMV) is the most important virus of this family and is the subject of active research, herpes simplex virus (HSV) and varicella-zoster virus (VZV) can also lead to severe disease. Epstein-Barr virus (EBV) associated with post-transplant lymphoproliferative disease is increasingly recognized as a major complication of SOT. There is less information available on the role and impact of other viruses of the herpesvirus family, such as the human herpes virus 6 (HHV-6), human herpes virus 7 (HHV-7) and human herpes virus 8 (HHV-8). This review summarizes current knowledge regarding epidemiology, clinical manifestations, diagnosis, treatment and prevention of infections caused by herpes viruses other than CMV in SOT recipients.

Impact of human herpes virus 6 in liver transplantation

Human herpes virus 6 (HHV-6) infects > 95% of humans. Primary infection which occurs mostly during the first 2 years of life in the form of roseola infantum, non-specific febrile illness, or an asymptomatic illness, results in latency. Reactivation of latent HHV-6 is common after liver transplantation. Since the majority of human beings harbor the latent virus, HHV-6 infections after liver transplantation are most probably caused by endogenous reactivation or superinfection. In a minority of cases, primary HHV-6 infection may occur when an HHV-6-seronegative individual receives a liver allograft from an HHV-6-seropositive donor. The vast majority of HHV-6 infections after liver transplantation are asymptomatic. Only in a minority of cases, when HHV-6 causes a febrile illness associated with rash and myelosuppression, hepatitis, gastroenteritis, pneumonitis, and encephalitis after liver transplantation. In addition, HHV-6 has been implicated in a variety of indirect effects, such as allograft rejection and increased predisposition to and severity of other infections, including cytomegalovirus, 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 prevention after liver transplantation. Asymptomatic HHV-6 infection does not require antiviral treatment, while treatment of established HHV-6 disease is treated with intravenous ganciclovir, foscarnet, or cidofovir and this should be complemented by a reduction in immunosuppression.

Challenges of T cell therapies for virus-associated diseases after hematopoietic stem cell transplantation

IMPORTANCE OF THE FIELD

Hematopoietic stem cell transplantation (HSCT) is the treatment of choice for many hematological malignancies and genetic disorders. The majority of patients do not have a human leukocyte antigen (HLA) identical sibling donor, and alternative stem cell sources include HLA-matched or mismatched unrelated donors and haploidentical related donors. However, alternative donor HSCT are associated with three major complications i) graft rejection; ii) graft-versus-host disease (GvHD); and iii) delayed immune reconstitution leading to viral infections and relapse.

AREAS COVERED IN THIS REVIEW

Graft rejection and the risk of GvHD can be significantly reduced by using intensive conditioning regimens, including in vivo T cell depletion as well as ex vivo T cell depletion of the graft. However, the benefits of removing alloreactive T cells from the graft are offset by the concomitant removal of T cells with anti-viral or anti-tumor activity as well as the profound delay in endogenous T cell recovery post-transplant. Thus, opportunistic infections, many of which are not amenable to conventional small-molecule therapeutics, are frequent in these patients and are associated with significant morbidity and high mortality rates. This review discusses current cell therapies to prevent or treat viral infections/reactivations post-transplant.

WHAT THE READER WILL GAIN

The reader will gain an understanding of the current state of cell therapy to prevent and treat viral infections post-HSCT, and will be introduced to preclinical studies designed to develop and validate new manufacturing procedures intended to improve therapeutic efficacy and reduce associated toxicities.

TAKE HOME MESSAGE

Reconstitution of HSCT recipients with antigen-specific T cells, produced either by allodepletion or in vitro reactivation, can offer an effective strategy to provide both immediate and long-term protection without harmful alloreactivity.

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.

Pediatric liver transplantation

In previous decades, pediatric liver transplantation has become a state-of-the-art operation with excellent success and limited mortality. Graft and patient survival have continued to improve as a result of improvements in medical, surgical and anesthetic management, organ availability, immunosuppression, and identification and treatment of postoperative complications. The utilization of split-liver grafts and living-related donors has provided more organs for pediatric patients. Newer immunosuppression regimens, including induction therapy, have had a significant impact on graft and patient survival. Future developments of pediatric liver transplantation will deal with long-term follow-up, with prevention of immunosuppression-related complications and promotion of as normal growth as possible. This review describes the state-of-the-art in pediatric liver transplantation.

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

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

Antiviral therapy for respiratory tract infections

Viruses are important pathogens causing respiratory tract infections both in the community and health-care facility settings. They are extremely common causes of morbidity in the competent hosts and some are associated with significant mortality in the compromised individuals. With wider application of molecular techniques, novel viruses are being described and old viruses are found to have new significance in different epidemiological and clinical settings. Some of these emerging pathogens may have the potential to cause pandemics or global spread of a severe disease, as exemplified by severe acute respiratory syndrome and avian influenza. Antiviral therapy of viral respiratory infections is often unnecessary in the competent hosts because most of them are selflimiting and effective agents are not always available. In the immunocompromised individuals or for infections caused by highly pathogenic viruses, such as avian influenza viruses (AIV), antiviral treatment is highly desirable, despite the fact that many of the agents may not have undergone stringent clinical trials. In immunocompetent hosts, antiviral therapy can be stopped early because adaptive immune response can usually be mounted within 5-14 days. However, the duration of antiviral therapy in immunosuppressed hosts depends on clinical and radiological resolution, the degree and duration of immunosuppression, and therefore maintenance therapy is sometimes needed after the initial response. Immunotherapy and immunoprophylaxis appear to be promising directions for future research. Appropriate and targeted immunomodulation may play an important adjunctive role in some of these infections by limiting the extent of end-organ damage and multi-organ failure in some fulminant infections.

Human herpesvirus 6 infection in adult living related liver transplant recipients

To analyze human herpesvirus 6 (HHV-6) infection in adult living related liver transplantation, we performed a virological analysis, including viral isolation, serological assay, and real-time polymerase chain reaction, of serially collected blood samples from 67 recipients. In addition, cytokine levels were measured to determine their role in viral reactivation. HHV-6 was isolated from only 4 recipients (6.0%), and viral DNA was detected in 15 (22.4%) of the 67 recipients. A significant increase in HHV-6 immunoglobulin G antibody titers was observed in 19 (28.4%) of the 67 recipients. Finally, 26 recipients (38.8%) had HHV-6 reactivation 2-6 weeks after transplantation. HHV-6 associated clinical features were analyzed in the 17 recipients presenting with either viremia or DNAemia. Two recipients with viremia and 3 recipients with DNAemia had unexplained fever at the time of viral infection. An increase in aminotransferase levels was observed in 2 recipients with viremia and 3 recipients with DNAemia. Recipients with liver cirrhosis caused by hepatitis B virus or hepatitis C virus infection as the underlying disease were more likely to have HHV-6 infection (P = 0.025). Mortality at the last follow-up in recipients with HHV-6 reactivation was significantly higher than in those without viral reactivation (P = 0.0118). Plasma interleukin-6 levels were significantly higher in the recipients with HHV-6 viremia than in the recipients without viremia at 4 weeks post-transplant (P = 0.0411). Moreover, tumor necrosis factor alpha levels were also higher in recipients with HHV-6 viremia (P < 0.0001) or reactivation (P = 0.0011) than in recipients without viremia or reactivation 4 weeks post-transplant.

Human Herpesvirus-6 and -7 After Lung and Heart–Lung Transplantation

BACKGROUND

The impact of herpesvirus-6 and -7 (HHV-6, HHV-7) activation in lung transplant recipients is still poorly understood. We report the appearance of HHV-6 and HHV-7 antigenemia after lung transplantation and evaluate the efficacy of anti-viral drugs against these viruses.

METHODS

Twenty-two lung or heart-lung recipients were monitored for HHV-6, HHV-7 and cytomegalovirus (CMV) during 12 post-operative months. HHV-6- and HHV-7-specific antigens and CMV pp65 antigens were analyzed in blood leukocytes and bronchoalveolar lavage fluid cells by monoclonal antibodies. Ganciclovir or valganciclovir prophylaxis for a minimum of 3 months was given to 19 recipients at risk for CMV infection.

RESULTS

HHV-6, HHV-7 and CMV antigenemia was detected in 20 (91%), 11 (50%) and 12 (55%) recipients (median 16, 31 and 165 days) after transplantation, respectively. HHV-6 antigenemia occurred in 15 (79%), HHV-7 antigenemia in 7 (37%) and CMV antigenemia in 1 (7%) of these patients during anti-viral prophylaxis. HHV-6 or HHV-7 antigenemia was frequently associated with CMV antigenemia, which was detected 3 to 12 months after transplantation. Ganciclovir or valganciclovir treatment of CMV infection was effective against the concomitant HHV-6 and HHV-7 antigenemia in 9 of 12 (75%) and 5 of 6 (83%) cases, respectively. One case of pneumonitis and 1 of encephalitis were temporally associated with HHV-6. No other clinical manifestations could be linked solely to HHV-6 or -7.

CONCLUSIONS

HHV-6 and -7 antigenemia was common and appeared early after lung transplantation. CMV prophylaxis was not able to prevent the appearance of HHV-6 and -7 antigenemia.

HHV-6 DNA in peripheral blood mononuclear cells after liver transplantation

BACKGROUND

Human herpesvirus-6 (HHV-6) infections have been reported after liver transplantation. In this study, the detection of HHV-6 DNA in peripheral blood mononuclear cells (PBMC) was compared with HHV-6 antigenemia in liver transplant patients.

OBJECTIVES

Forty-three adult liver recipients were frequently monitored by HHV-6 antigenemia test, which detects the viral antigens in PBMC, but is rather qualitative than quantitative.

STUDY DESIGN

From the same PBMC specimens HHV-6 DNA was demonstrated by in situ hybridization using a biotinylated probe and quantified as positive cells/10, 000 PBMC. Altogether 330 blood specimens were analyzed.

RESULTS

During the first 6 months (mean 12 days) after transplantation, 35/43 patients developed HHV-6 antigenemia. Concurrently, HHV-6 DNA-positive cells with mean peak number of 661(+/-574)/10, 000 were detected in 33/35 patients. Seven patients received ganciclovir treatment because of concurrent CMV infection with mean peak number of HHV-6 DNA-positive cells 381(+/-336) before and 34(+/-59)/10, 000 after the treatment (p = 0.03). All CMV infections responded to ganciclovir, but HHV-6 DNAemia disappeared slowly, within 79 days (mean 36 days). Without antivirals, HHV-6 DNAemia/antigenemia lasted usually longer.

CONCLUSIONS

Detection of HHV-6 DNA in PBMC correlated well with HHV-6 antigenemia, and may be used in the monitoring of transplant patients.

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.

Emerging viral infections in transplantation

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

A prospective survey of human herpesvirus-6 primary infection in solid organ transplant recipients

Human herpesvirus 6 (HHV-6) infection is potentially life-threatening to immunosuppressed patients. There is a lack of information regarding the risk and the clinical manifestations of primary HHV-6 infection in solid-organ transplant recipients. We prospectively evaluated patients undergoing solid organ transplantation with negative immunoglobulin (Ig) G antibodies against HHV-6 by means of HHV-6 quantitative polymerase chain reaction. Among 193 recipients, seven were HHV-6 seronegative (prevalence 3.6%). We detected a positive HHV-6 viral load in only one patient, and four patients seroconverted after one year posttransplantation. The patient with a positive HHV-6 viral load developed cholestatic hepatitis without fever and did not experience severe end-organ disease. In conclusion, our findings show a low incidence of symptomatic primary HHV-6 infection among seronegative solid-organ transplant recipients.

Pediatric liver transplantation

Liver transplantation has become the accepted standard of care in the treatment of a child with a failing liver. Advances in the management of critical care and immunosuppression along with the development of innovative operative procedures have improved outcome such that 5-year survival rates of 80% to 90% are expected following liver transplantation. Organ allocation schemes have evolved in an effort to better stratify recipient risk thereby more appropriately distributing deceased donor grafts. A persistent shortage of appropriate donors continues to contribute to patient mortality. The consequences of long-term immunosuppression have become increasingly apparent such that health care providers need to be aware of the side effects of chronic immunosuppression. New strategies need to be defined to minimize the need of continuous immunosuppression. The continued success of pediatric liver transplantation will require multi-disciplinary health care teams comprised of general pediatricians, pediatric hepatologists, transplant surgeons, and transplant coordinators who focus on the complex needs of the transplant recipient.

HHV-6 and HHV-7 antigenemia related to CMV infection after liver transplantation

BACKGROUND

Betaherpesviruses human herpesvirus-6 and -7 (HHV-6, HHV-7), which are closely related to cytomegalovirus (CMV), have been reported in transplant patients. In this retrospective study, we investigated the occurrence of HHV-6 and HHV-7 antigenemia in relation to symptomatic CMV infection after liver transplantation.

METHODS

Sample material from 64 adult liver transplant recipients was included in the study. The patients were monitored weekly for CMV, HHV-6, and HHV-7. CMV infections were diagnosed by pp65-antigenemia and viral cultures. Concomitantly HHV-6 and HHV-7 antigens were demonstrated in peripheral blood mononuclear cells by monoclonal antibodies against both variants A and B and immunoperoxidase staining. Altogether 540 post-transplant blood specimens were analyzed.

RESULTS

Nineteen patients (30%) developed symptomatic CMV pp65 antigenemia during the first 3 months (mean 33 days, range 5-62 days) post-transplantation and were treated with intravenous ganciclovir. Concurrent HHV-6 antigenemia was detected in 16/19 (median 9 days, range 6-24 days) and HHV-7 antigenemia 15/19 patients (median 17 days, range 5-58 days) after transplantation. HHV-6 appeared before CMV in most cases (12/16), HHV-7 usually together with CMV. In those cases that HHV-6 preceded CMV antigenemia, it also was a possible cause of graft dysfunction. HHV-7 and CMV were so closely overlapping, that no symptoms could solely be linked with HHV-7.

CONCLUSION

HHV-6 and HHV-7 antigenemia usually occurred together with symptomatic CMV infection after liver transplantation. HHV-6 preceded CMV, but HHV-7 appeared together with CMV. Further investigation of the clinical significance of HHV-6 and HHV-7 antigenemia in organ transplant patients is necessary.

Pediatric liver transplantation

In the past two decades, pediatric liver transplantation has become the state-of-the-art operation with anticipated success and limited mortality. The future success of pediatric liver transplantation will require thoughtful solutions to the delicate balance of risk to donors and recipients, the complex needs of the acute postoperative patient, and the long-term challenges of chronic immunosuppression in these previously unsalvageable patients.

Viral and fungal infections after liver transplantation--part II

Viral and fungal infections in liver transplant recipients are important to recognize and treat early because of their association with substantial morbidity and mortality. Some viruses, such as cytomegalovirus and human herpesvirus 6, have immunomodulatory properties and can facilitate other infections, including fungal infections. Cytomegalovirus has long been recognized as an important virus in transplantation, but in the past decade other viruses have also received attention in the medical literature because of their association with particular clinical syndromes. Although human herpesvirus 6 has been associated with fever, rash, and encephalitis, a direct cause-and-effect relationship is still lacking. Human herpesvirus 8 has been found to be the cause of Kaposi sarcoma. Molecular techniques (e.g., pp65 antigenemia and polymerase chain reaction) that have been introduced for routine diagnosis of viruses have facilitated the diagnosis of asymptomatic viral infections and the institution of preemptive therapy. Nonetheless, the diagnosis of invasive fungal infections in liver transplant recipients is often delayed and thus associated with high mortality. Despite the use of new antifungal agents in clinical practice and the reduced incidence of fungal infections because of antifungal prophylaxis regimens, mortality has not decreased. Future patient outcomes may improve with early identification of patients who have risk factors for invasive fungal infections and with the development of new molecular diagnostic techniques for early detection.

Quantitative detection and differentiation of human herpesvirus 6 subtypes in bone marrow transplant patients by using a single real-time polymerase chain reaction assay

Human herpesvirus (HHV)--6 infections are ubiquitous, but infection or reactivation under immunocompromised conditions, such as bone marrow or solid organ transplantation, can often result in serious clinical manifestations. Two HHV-6 subtypes are known. Most primary HHV-6 infections are caused by subtype 6B, but little information is available about the prevalence, distribution, and clinical divergence of 6A and 6B. To study this, we have developed a highly sensitive and specific real-time polymerase chain reaction (PCR) assay that can detect, quantitate, and reliably differentiate HHV-6A and -6B in clinical specimens. Exploiting a single-base variation in the DNA polymerase gene of these respective subtypes, we used melting curve analysis for subtype discrimination. Moreover, this assay's ability to discriminate HHV-6 subtypes was confirmed by PCR/restriction fragment length polymorphism analysis of the HHV-6 large tegument protein gene and PCR amplicon size-discrimination analysis of the HHV-6 immediate-early gene. Using this assay, we present our findings about the prevalence and distribution of these subtypes in bone marrow transplant patients. Of 803 plasma specimens tested from 353 patients, 136 specimens (17%) from 60 patients were determined to be HHV-6 positive. We analyzed these HHV-6--positive patients for subtype identification by using our newly developed assay and determined that 58 patients (97%) were HHV-6B positive and 2 patients (3%) were HHV-6A positive. No patient was coinfected with both subtypes. This assay can be a sensitive, genotype-specific, rapid method to reliably diagnose life-threatening HHV-6 infections in immunocompromised patients and can be useful in guiding and monitoring specific therapy.

HHV-6-DNAemia Related to CMV-DNAemia After Liver Transplantation

In addition to cytomegalovirus (CMV), activation of other betaherpesviruses, especially human herpesvirus 6 (HHV-6), has been reported in liver transplant patients. The purpose of this study was to investigate the posttransplant HHV-6-DNAemia in relation to CMV-DNAemia in liver transplant patients. Thirty-one adult liver allograft recipients were regularly monitored for CMV and HHV-6 during the first 3 months after transplantation. For the diagnosis of CMV infections, pp65-antigenemia assay and quantitative DNA-PCR were used. HHV-6 was demonstrated by using quantitative DNA-PCR and HHV-6 antigenemia test. Altogether 253 blood specimens of 31 recipients were analyzed. In addition, CMV and HHV-6 specific antigens were demonstrated by immunohistochemistry in liver biopsy specimens in the case of graft dysfunction. Thirteen patients (40%) developed a clinically significant CMV infection, at a mean of 33 days (range 5 to 62 days) after transplantation and were treated with intravenous ganciclovir. The peak viral loads of these symptomatic CMV infections were high (CMV-DNA 34210 +/- 37557 copies/mL plasma). Six additional asymptomatic patients demonstrated significantly lower CMV-DNAemia levels (1020 +/- 1008 copies/mL, P < .05), and were not treated. Concurrently with CMV, HHV-6 DNAemia and antigenemia were detected in 17 of 19 patients, mean 11 days (range 6 to 24 days) after transplantation. HHV-6 appeared prior to CMV in most cases (12 of 17). However, the peak viral loads were low (HHV-6-DNA <1500 copies/mL blood), even in the five patients who demonstrated HHV-6 antigens on liver biopsy. All CMV infections were successfully treated with ganciclovir and the CMV DNAemia/antigenemia subsided. HHV-6 also responded to the antiviral treatment, but more slowly and less clearly. In conclusion, HHV-6 activations were common and usually associated with CMV infection in liver transplant patients. Further investigation of the clinical significance of HHV-6 DNAemia/antigenemia is necessary.

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).

Encephalitis owing to human herpesvirus-6 after cardiac transplant

Human herpesvirus-6 (HHV-6), a beta herpesvirus closely related to cytomegalovirus (CMV), infects the majority of the population in childhood. Human herpesvirus-6 can be reactivated in the immunosuppressed patient. After bone marrow and orthotopic liver transplant, it has been linked to various clinical syndromes, including undifferentiated febrile illness, encephalitis, pneumonitis and bone marrow suppression. To date its infectious role after orthotopic heart transplant has not been well documented. We present the case of a 32-year-old cardiac transplant recipient who initially presented 8 weeks after his transplant with high fever and headache. He developed increasing confusion, pulmonary infiltrates and neutropenia. Cytomegalovirus viral loads were negative. Polymerase chain reaction (PCR) of blood and cerebrospinal fluid detected HHV-6 DNA, consistent with HHV-6-related encephalitis, pneumonitis and bone marrow suppression. He was treated with foscarnet with gradual improvement in clinical status. We review the literature on the significance of this virus post cardiac transplant.

Human herpesvirus 6 (HHV6) infection

Human herpes virus-6 was first reported in 1986 and is the sixth member of the herpes virus family. HHV-6 consists of two closely related variants HHV-6A and HHV-6B. The majority of infections occur in healthy infants with most infections caused by HHV-6B. The virus preferentially infects CD4+T-lymphocytes and the surface marker CD46 acts as a co-receptor. Infection is followed by persistence and latency in different cells and organs including monocytes/macrophages, salivary glands, the brain and the kidneys. In this article we will discuss the clinical manifestations of HHV-6 infection in healthy children and the syndromes associated with HHV-6 reactivation in immunocompromised patients. Evidence of association between HHV-6 infection and different clinical entities such as multiple sclerosis, malignancy, infectious momononucleosis, drug hypersensitivity syndromes and skin eruptions is discussed. Published data on the use and efficacy of antiviral agents in complicated infections and infections in immunocompromised patients is presented.

Human herpesvirus-6 in renal transplant recipients: potential risk factors for the development of human herpesvirus-6 seroconversion

Herpesviruses, including human herpesvirus-6 (HHV-6), reactivate and have the potential to be pathogenic in immunocompromised patients. Little information is available regarding the correlation between immunosuppressive therapy and HHV-6 seroconversion after organ transplantation. Serum samples obtained from 120 kidney and kidney/pancreas transplant recipients were tested to explore the potential risk factors for developing HHV-6 infection including types of immunosuppression and induction/rejection therapy. Stored serum samples obtained prior to and at the 2nd, 4th, 12th and 48th weeks after transplantation were tested for anti-HHV-6 immunoglobulin (Ig)M antibodies using indirect immunofluorescence assay. Prior to transplantation and 48 weeks after transplantation the sera were additionally tested for anti-HHV-6 IgG using enzyme-linked immunoassay. Ninety-one percent of 120 recipients were HHV-6 IgG-positive before transplantation. One hundred seven of 120 patients were anti-HHV-6 IgM-negative before transplantation. Primary/secondary HHV-6 seroconversion occurred in sera of 46.6% of these 107 patients. HHV-6 seroconversion most frequently occurred 2 to 4 weeks after transplantation. There was no significant relationship between HHV-6 seroconversion and the treatment with methylprednisolone (MP). The incidence of HHV-6 seroconversion was significantly higher in subjects who were treated with the regimens including Daclizumab or Sirolimus as compared with those who were on other protocols. HHV-6 seropositivity in the Polish population of organ transplant recipients is very high. We demonstrated a trend toward association of HHV-6 seroconversion with type of immunosuppressive therapy.

Human herpesvirus-6 and -7 infections in transplantation

Human herpesvirus-6 (HHV-6) and human herpesvirus-7 (HHV-7) are ubiquitous in the human population and cause exanthem subitum, a benign disease seen in infancy. The viruses remain latent in the body after primary infection, and reactivate in immunocompromised patients. HHV-6 infection occurs in nearly 50% of all bone marrow and in 20-30% of solid-organ transplant recipients, 2-3 weeks following the procedure. It has been suggested that the viral infection and activation result in clinical symptoms, including fever, skin rash, pneumonia, bone marrow suppression, encephalitis, and rejection. In order to understand the viral infection in greater detail, several studies investigating the route of viral transmission and diagnostic procedures have been carried out. In contrast to studies of HHV-6 infection in organ-transplant recipients, the number of studies examining HHV-7 infection in these patients is limited. According to several recent studies, HHV-7 may act as a cofactor for cytomegalovirus disease in organ-transplant recipients.